LED Landing Lights
Design, Certification & Production
Financial & Technical Feasibility Study
Internship report
May 8, 2013
Aslm El-Gharabawy
M.Sc. Graduate Student
Delft University of Technology
Faculty of Aerospace Engineering
Kluyverweg 1
Delft, The Netherlands
KLM Royal Dutch Airlines
KLM Engineering & Maintenance
Dept. Cabin Avionics, Hangar 14
Schiphol-Oost, The Netherlands
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Table of contents
TABLE OF CONTENTS ..............................................................................................2
INTRODUCTION..........................................................................................................5
1.
SELECTING LAMP POSITION & AIRCRAFT TYPE ...........................................6
1.1
1.2
2.
LED SYSTEM BREAKDOWN ..............................................................................9
2.1
2.2
2.3
2.4
2.5
3.
CONSUMPTION LIST ANALYSES .........................................................................6
CHOOSING A LAMP ...........................................................................................7
LED PACKAGE .................................................................................................9
THERMAL HEAT SINK ......................................................................................10
LED ELECTRICAL DRIVER ...............................................................................11
OPTICAL LENS ...............................................................................................11
LUMINAIRE HOUSING ......................................................................................11
THE LANDING LIGHT ASSEMBLIES ...............................................................12
3.1
THE RETRACTABLE LANDING LIGHT ASSEMBLY ................................................12
3.1.1 Location of the assembly .........................................................................12
3.1.2 Parts of the assembly...............................................................................13
3.1.3 Dimensions of the assembly ....................................................................15
3.1.4 Material of the assembly ..........................................................................15
3.2
THE FIXED LANDING LIGHT ASSEMBLY .............................................................16
3.2.1 Location of the assembly .........................................................................17
3.2.2 Parts of the assembly...............................................................................17
3.2.3 Dimensions of the assembly ....................................................................19
3.2.4 Material of the assembly ..........................................................................19
3.3
OPERATING ENVIRONMENT ............................................................................19
3.3.1 Temperature.............................................................................................20
3.3.2 Atmospheric pressure ..............................................................................20
3.3.3 Air density ................................................................................................20
3.3.4 Absolute and relative humidity .................................................................21
3.4
OPERATING TIME ...........................................................................................22
3.4.1 Operating time per procedure ..................................................................22
3.4.2 Average operating time per year ..............................................................22
4.
PRELIMINARY LED LAMP DESIGN .................................................................24
4.1
DESIGN REQUIREMENTS.................................................................................24
4.1.1 CS 25.773(a) ............................................................................................25
4.1.2 CS 25.1383(a), (b), (c) .............................................................................25
4.1.3 SAE ARP693 REV. D...............................................................................25
4.1.4 SAE ARP6402 REV. A .............................................................................26
4.1.5 SAE guidance outline ...............................................................................26
4.1.6 Minimum Equipment List ..........................................................................29
4.2
REVERSE ENGINEERING .................................................................................29
4.3
DROP-IN REPLACEMENT (RETROFITTING) .......................................................30
4.4
PAR 64 SEALED BEAM HALOGEN LAMPS ........................................................30
4.5
LIGHT OUTPUT: FROM LUMINOUS INTENSITY TO LUMINOUS FLUX .....................31
4.6
LUMINOUS EFFICACY......................................................................................33
4.7
LED PACKAGE PARAMETERS ..........................................................................36
4.7.1 Light output ..............................................................................................36
4.7.2 Thermal performance indicators ..............................................................36
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4.7.3 Design simplicity and versatility ...............................................................37
4.7.4 Color temperature ....................................................................................37
4.7.5 Robustness ..............................................................................................38
4.7.6 Operating temperatures ...........................................................................38
4.8
THERMAL MANAGEMENT ................................................................................39
4.8.1 Wall-plug efficiency ..................................................................................39
4.8.2 Vapor chamber and heat pipes ................................................................40
4.8.3 LEDs directly mounted on heat pipes ......................................................44
4.8.3 Thermal conductivity, conductance and resistance .................................47
4.8.4 Meeting the expectations .........................................................................50
4.8.5 Thermal convection ..................................................................................53
4.8.6 Thermal radiation .....................................................................................55
4.8.7 Thermal path to additional surface ...........................................................56
4.9
THE RESULTS ................................................................................................56
5.
COST-BENEFIT ANALYSIS ..............................................................................59
5.1
DESIGN COSTS ..............................................................................................59
5.1.1 Outsourcing detailed design.....................................................................59
5.1.2 Total design costs DOA holder ................................................................61
5.2
PRODUCTION COSTS......................................................................................61
5.2.1 Production Organization Approval ...........................................................61
5.2.2 Non-POA: Philips Innovation Services .....................................................62
5.3
CERTIFICATION COSTS ...................................................................................63
5.3.1 DO-160G testing ......................................................................................63
5.3.2 EASA Supplemental Type Certificate (STC) ............................................63
5.4
PRODUCT/UNIT COSTS ...................................................................................64
5.5
RETURN ON INVESTMENT (ROI) .....................................................................64
5.5.1 Total expenses per year...........................................................................64
5.5.2 Total development costs ..........................................................................65
5.5.3 Results of the regular approach ...............................................................66
5.5.4 Results of the depreciation approach.......................................................66
6
RISK ANALYSIS - EVALUATING AND MANAGING RISKS ............................69
6.1
IDENTIFYING RISKS/THREATS..........................................................................69
6.1.1 Certification risks ......................................................................................69
6.1.2 Financial risks ..........................................................................................71
6.1.3 Technical risks .........................................................................................72
6.1.4 Procedural risks .......................................................................................73
6.2
FAILURE MODES AND EFFECTS ANALYSIS (FMEA) .........................................73
7
CONCLUSION AND RECOMMENDATIONS ....................................................77
REFERENCES...........................................................................................................79
APPENDIX A: THE RETRACTABLE LANDING LIGHT ASSEMBLY ......................81
APPENDIX B: DAILY AVERAGE NUMBER OF LANDINGS B737 .........................83
APPENDIX C: CONCEPT PROPOSAL THERMAL MANAGEMENT SOLUTION
FROM THERMACORE EUROPE ..............................................................................85
APPENDIX D: SAE AEROSPACE – LANDING AND TAXIING LIGHTS - DESIG
CRITERIA FOR INSTALLATION [SAE-ARP-693] ...................................................89
APPENDIX E: SAE AEROSPACE – LED LANDING,TAXIING, RUNWAY
TURNOFF, AND RECOGNITION LIGHTS [SAE-ARP-6402] .................................107
APPENDIX F: QUOTATION FOR A THERMAL ANALYSIS FROM THERMACORE
EUROPE ..................................................................................................................121
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APPENDIX G: QUOTATION FOR A TECHNICAL FEASIBILITY STUDY FROM
ADVANCED COOLING TECHNOLOGIES, INC. ....................................................123
APPENDIX H: QUOTATION FOR A THERMAL ANALYSIS & CONCEPT
DEVELOPMENT FROM MJM ENGINEERING .......................................................129
APPENDIX I: QUOTATION FOR DO-160G TESTING FROM NATIONAAL LUCHTEN RUIMTEVAARTLABORATORIUM (NLR) .........................................................133
APPENDIX J: TECHNICAL FEASIBILITY STUDY PHILIPS ..................................141
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Introduction
The key strengths of LED lighting compared to incandescent lighting are reduced
power consumption and longer operating lifetime, both resulting into lower life time
costs. Also slow failure – LEDs mostly fail by dimming over time, rather than the
abrupt failure of incandescent bulbs – and shock resistance as a solid state
component are important benefits for aerospace lighting.
Due to these benefits, KLM Royal Dutch Airlines has the desire to reduce
maintenance and fuel costs by implementing exterior LED lighting systems into
aircrafts. For new-built aircrafts, exterior LED lighting systems are already realized.
For existing aircraft, KLM desires replacement of the existing exterior lighting
systems by LED lighting systems.
The study described in this report concerns a feasibility research on the
implementation of exterior LED lighting systems for existing aircraft. As there are
many types of exterior lighting systems and only a limited time frame to perform this
research, the author of this report chooses to start off with the landing lights of the
Boeing 737-Next Generation aircrafts. The reasons for this choice will be explained in
section 1.2.
The report will deal with the question whether it is possible and feasible for KLM to
develop their own high-quality LED aircraft landing light lamps, including their
(external) production. The issue of retrofitting – by designing a drop-in LED lmap
solution – plays a key role in the technical and financial feasibility. As such, it is
imperative to study the certification and technical risks (section 6.1.1 and 6.1.3
respectively), necessary resources and financial means (chapters 4 and 5
respectively) and the timeframe that is needed in order to have such a system ready
for production with the related conditions that should be met in order to achieve this
(section 4.1).
It is of the essence to start off by giving some insight into LED technology and to
where this technology is heading in the near future. Since LED technology is in rapid
development as the future lighting solution, this project aims to design a retrofitting
LED landing light lamp as reliability increasing solution to be applied on the entire
KLM fleet. With this aim, a start is made with by looking at the landing lights
(assemblies) of the aircraft type which covers the major part (46%) of the fleet,
namely the Boeing 737-NG aircraft. With this type as a starting point, the journey for
the exploration of the technical and financial possibilities begins.
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1.
Selecting lamp position & aircraft type
Aircrafts have different exterior lighting positions and as such also different lamp
types, which again may well vary per aircraft type. In civil aviation these exterior
lighting positions in general consist of (see also figure 1.1):
 Position lights
 Anti-collision lights
 Landing, taxi and runway turnoff lights
 Logo lights
 Wing and engine inspection lights
 Cargo and service lighting
 Emergency lights
As the project had to be completed within five month, it was not possible to include all
exterior aircraft lighting positions of all aircraft types in this study. This section
describes the procedure and key factors which influenced the decision of choosing
the landing lights of the Boeing 737-NG as first candidates to be fitted by LED
solutions.
Figure 1.1: Aircraft exterior lighting systems (Boeing 737-NG)
1.1
Consumption list analyses
As the project had to be completed within the limited time frame of five month, it was
not possible to include all exterior aircraft lamp positions of all aircraft types in the
research plan for the technical and financial feasibility analysis. As such the author
chose to select an external light position on a specific aircraft type. In order to go
about this, an item consumption list of all exterior lamps is requested from the
Material Planning department at KLM, which listed all the exterior lamps that have
been consumed by the KLM fleet during the past 68 month. The same list also
indicates the price per item and the consumption rate per item per month. Using this
data a simple overview is made of the average consumption rate of each item per
month and consequently thus also the average costs per item.
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This analysis purely indicates the item costs, without any indication of auxiliary costs.
As auxiliary costs one could come up with storage costs and labor hours spent on
lamp replacements during maintenance. Inquiring on these costs, the maintenance
department pointed out that they generally are the same for each lamp type. The
amount of labor hours which is registered by the system is standardized for all lamp
types and is set at one hour per lamp change.
Performing this analysis showed three top items as candidates for this project, sorted
in table 1.1 by consumption rate per month from the most to the least consumed:
Lamp part
number
GEQ4559X /
GEQ5559
GEQ4631
HLX64621
A/C Model &
Type
Average
consumption
per month
ALL
64
$21.50 /
$55.85
Average
costs per
month in USD
$1370 /
$3575
48
$30.70
$1467
B747/ MD11/A330
B737/MD11/B777/A330
Supplier price
in USD
47
$457
Table 1.1: Top 3 lamps with most average costs per month
The applications of the lamps in table 1.1 are:
 HLX64621:
Wing scanning lights, position lights, logo lights
 GEQ4559X / GEQ5559:
Landing lights
 GEQ4631:
Wing scanning lights, logo lights
1.2
Choosing a lamp
As can be seen form table 1.1, during the last 68 months the lamps with part
numbers GEQ4559X/GEQ5559 have the highest consumption rate per month. These
Sealed Beam PAR 64 lamps are used for the landing lights of all aircraft types.
GEQ4559X was used until August 2010. From August 2010 GEQ5559 was
introduced as a replacement for GEQ4559X, since it was supposed to last twice as
long as the GEQ4559X. It turned out that this is actually not the case, according to a
conducted research of the lamp failure rates of the Transavia B737-NG fleet (using
GEQ4559X), which was compared with the KLM B737-NG fleet (using GEQ4559X).
Since the cost of a labor hour is much more expensive than the lamp costs (≈ $175)
and every lamp is changed on demand (after an observed failure), the labor costs
outweigh the lamp costs when performing the financial analysis. As such the lamp
costs are not considered significant and the lamp choice is made according to the
highest failure rate (i.e. consumption rate). This renders GEQ4559X/GEQ5559 as the
lamp candidate which is most attractive to be replaced by an LED variant in order to
increase the fleet reliability.
In consultation with KLM Engineering & Maintenance, the following arguments for
this decision can be mentioned:
1. The Sealed Beam PAR 36 GEQ4631 has a higher average consumption rate
of 16 more consumptions per month than the number two candidate
GEQ4559X/GEQ5559. This amounts to 16 more labor hours of work per
month and related auxiliary costs will definitely be higher then the difference
in average costs per month between both lamps.
2. GEQ4631 is a 250 Wattage lamp, whereas GEQ4559/GEQ5559 have a
power consumption of 600 Watts. It is therefore more challenging to design a
LED variant for the latter lamp type. Once a design has been put forth, it is
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more straightforward to downgrade this to one that is compatible with the
Sealed Beam PAR 36 type GEQ4631, which has actually the shape parabolic
shape as the Sealed Beam PAR 64 type GEQ4559X/GEQ5559 but is smaller.
Furthermore since GEQ4559X/GEQ5559 lamps:
a. have the highest power consumption of all other lamps, the design will
be more complicated and challenging
b. are located at – among others – a retractable position, so their design
should be as compact and volume efficient as possible
3. GEQ5559 (currently used) is more expensive than the all the other lamps.
4. There is still no retrofitting LED solution for the Sealed Beam PAR 64 type.
Considering the abovementioned reasoning, the remainder of this study will deal with
the replacement of the current Sealed Beam PAR 64 halogen lamp GEQ4559X by a
LED variant.
Figure 1.2: GEQ4631 - Sealed Beam PAR 36 lamp
Figure 1.3: Teledyne Alphabeam FAA-PMA-approved LED retrofit of the Sealed Beam PAR 36 lamp
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2.
LED system breakdown
LED systems consist of several parts which should be tuned to one another. Parts of
simple LED systems can be roughly categorized into:
 LED module/package
 Thermal design (e.g. heat sink)
 LED electrical driver
 Optical design / reflectors
 Luminaire housing
Figure 2.1: Several parts of a LED system
During the redesign of GEQ4559X all these parts need to be considered in order to
have a sound LED replacement. Each part and its function shall be briefly described
in the following subsections of this chapter.
2.1
LED package
The LED module contains the LED package, which consists of an outer package that
contains 1) a LED chip mounted on 2) a (usually silicon) submount or die attach,
which is again mounted on 3) a thermal heat sink slug and 4) a hard lens on the topside of the LED package to protect it from damage and shaped to produce a specific
viewing angle. Figure 2.2 is an example of a typical LED package.
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The bottom side of the LED chip which is connected to the submount, is called the
LED junction. LED packages can be mounted in series as well as in parallel on e.g.
printed circuit boards to create a LED array.
Figure 2.2: Typical LED package
2.2
Thermal heat sink
Light is produced on the top side of LED chips, whereas dissipating heat is produced
on the bottom side of the chips (the LED junction area). The light production
efficiency of LEDs is overall 30-40%. This means that around 60-70% of the input
power will be transformed to heat that needs to be carried away from the bottom side
of the LED chip. This is extremely essential, since the performance/efficiency and
lifetime of LED chips are strongly related to the junction temperature of the chips.
Also the reliability of LED chips is strongly dependent on the junction temperature.
In general it is recommended to keep the junction below 120 °C in order to run the
LEDs for maximum lifetime. Exceeding the maximum operating temperature
specification, which is typically 150 °C junction temperature, can cause permanent
damage to LEDs.
There are many thermal management solutions; passive and active ones. Though
active thermal designs can carry lots of heat away from the source, they are not
preferred since they include moving parts that have higher failure rates than nonmovable parts. Active thermal designs thus make the total system less reliable.
Passive thermal solutions can carry considerable less heat than active ones, but
have a much higher reliability. To ensure good thermal management for high power
LED operation, one should have a clear idea of the conducting thermal path of the
LED device. Eventually all the heat which is carried away from the source should be
dumped into some kind of heat sink made of highly thermal conductive material,
which dissipates it to the ambient atmosphere by convection and radiation.
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2.3
LED electrical driver
Regulating LED current is obtained by driving the device with a constant current
source. Through the use of control circuitry, a constant current source is provided or
“driven” to the LED. This constant current eliminates variations in current due to
changes in the forward current, which results in a uniform or constant level of LED
brightness.
A LED driver is a stand-alone control circuitry or a self-contained power supply with
control circuitry that provides an output matching the electrical characteristics of the
LEDs to be controlled. It responds to the ever-changing needs of the LED, or circuit
of LEDs, by supplying a constant amount of power to the LED as its electrical
properties change with temperature [1].
2.4
Optical lens
LED packages have a high viewing angle of up to 140 degrees, whereas the landing
lights illuminate the runway with a directional light beam of up to 11 degrees. Hence it
is necessary to have an optical lens designed for the LED device that bundles the
emitted LED light into a directional light beam which matches that of the current
halogen landing light lamp.
2.5
Luminaire housing
In order to protect the components of a LED device against any damage, a rigid
housing should contain all (electrical) parts and components. Often this housing also
functions as a (part of the) heat sink and its area is sometimes increased by adding a
fin structure to it. If that is indeed the case, obviously the material of the luminaire
housing should be highly thermal conductive.
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3.
The landing light assemblies
The Boeing 737-NG aircrafts are equipped with two types of landing light assemblies:
two fixed and two retractable assemblies. The fixed landing lights are always
operated during both landing and takeoff procedures. The retractable landing lights
are generally only operated during landing procedures at night. However, strictly
speaking, there a no hard regulations on the usage of the latter lights and as such
pilots tend to have different operating behavior considering those lights.
Landing lights are used primarily to provide ground reference information during final
approach, touchdown, ground roll, and takeoff, and to illuminate any major
obstructions in the airplane’s approach glide path or on the runway at night [21].
It may also be used for signaling purposes in flight. The landing lights may be turned
“on” when [21]:
a. Operating within 10 miles of any airport
b. Operating in conditions of reduced visibility, i.e., haze, dust, etc.
c. Operating under special visual flight rules (VFR) conditions
d. Operating where flocks of birds may be expected (coastal area, swamp lands,
migratory areas, etc.)
3.1
The retractable landing light assembly
This section shows and explains the retractable landing light assemblies in which the
current PAR 64 Q45559 halogen lamps operate as subparts.
3.1.1 Location of the assembly
The landing lights assemblies are installed in the lower airplane fuselage, near the
wing root. The lights are designed to extend and shine forward, parallel to the
waterline of the airplane. The lights may be extended at any speed. Figure 3.1
indicates the location on the fuselage. These images are part of the Aircraft
Illustrated Parts Catalog for Boeing 737-NG.
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STA 540
Landing light
Figure 3.1: Location landing light assembly on a Boeing 737-NG
3.1.2 Parts of the assembly
The landing lights assembly of the Boeing 737-NG fleet is composed of two main
parts, each part consisting of several subparts, as shown in figure 3.2 – also from the
Aircraft Illustrated Parts Catalog for the Boeing 737-NG:
1. A retractable part, with:
A. A cone-shaped fixture that contains the PAR 64 Sealed Beam halogen
lamp GEQ4559X
B. The PAR 64 Sealed Beam halogen lamp GEQ4559X (see section 4.3
for more details)
C. A lens in front of the halogen lamp en connected to the fixture by
screws
2. A non-movable part, with:
D. A cover in which the retractable part is retained
E. A baseplate on the cover
F. A motor assembly for retracting the retractable part
G. A transformer
See also Appendix A for photographic images of the assembly.
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C
G
E
F
D
A
B
Figure 3.2: Retractable Landing Light Boeing 737-NG
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3.1.3 Dimensions of the assembly
Figure 3.3 shows the approximate dimensions of the retractable part of the landing
light assembly in extended and retracted configuration, i.e. the lamp fixture. There is
no interest in the dimensions of the non-movable part since it does not contain the
GEQ4559X lamp and consequently it will not be subjected to alternations in case the
halogen lamp gets replaced by a LED lamp.
Since the exact dimensions are proprietary data of the original manufacturer
Honeywell, the dimensions had to be measured by hand from an assembly which
was taken out for maintenance. Though these measurements are approximations,
they are good enough for a preliminary design and feasibility study of a replacement
LED lamp inside the retractable fixture.
≈ 120
81.2°± 0.5°
≈ 50
≈ 230
≈ 180
≈ 140
Figure 3.3: Dimensions of the main assembly parts (in mm)
3.1.4 Material of the assembly
Although not explicitly mentioned, Honeywell’s Component Maintenance Manual
(CMM) for this assembly indicates that the complete assembly is made of aluminum.
This indication is based on the fact that the CMM mentions to “Use ANSI B74.18
aluminum oxide abrasive cloth on aluminum parts” under the ‘Repair’ section [19].
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However, it is not exactly known what type of aluminum alloy is used. The author of
this report thus assumes it to be of the same type as the aircraft skin, since the
expansion coefficients of both the assembly and the skin should be the same,
considering the fact that the assembly’s baseplate (part E of figure 3.2) is part of the
aircraft’s skin and both are exposed to the same ambient atmospheric conditions.
Figure 3.4 shows the assembly’s baseplate in its position at the fuselage cut.
Another straightforward reason for the mentioned assumption is that complete
assembly would be very heavy in case it had been made of any other metallic
material.
Baseplate
Aircraft skin
Figure 3.4: Baseplate in position at the fuselage cut
3.2
The fixed landing light assembly
The fixed landing lights are typically used during takeoff and landing procedures at
both day and night. The lamp used on this assembly, the General Electric Q5559, is
slightly different than the one used for the retractable landing light. Like the GE
Q4559x, this lamp is also a PAR64 Sealed Beam halogen lamp. It has the same
specifications as Q4559x, except the light output (Max. Beam Candlepower) is lower;
650,000 Candela instead of 765,000. See section 4.4 for more information regarding
these lamps.
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3.2.1 Location of the assembly
The fixed landing lights on the Boeing 737-NGs are located on the leading edge of
the aircraft root, next to the runway turnoff lights, as show in figure 3.5. This figure is
part of the Aircraft Illustrated Parts Catalog for the Boeing 737-NG.
Figure 3.5: Position fixed landing lights on B737-NG
3.2.2 Parts of the assembly
The landing light assembly is much simpler than the retractable one. It consists of a
part that retains or actually ‘fixes’ the lamp in a certain position which enables the
lamp – and thus also the light beam – to be tilted 3.07 degrees with respect to its
normal axis. This is fixed configuration is shown in figures 3.6. Figure 3.7 shows as
section through the part of the lamp retainer which clasps around the edge of the
lamp and as such holds the latter in position.
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Lamp
Container
Q5559
Lens
Figure 3.6: Lamp retainer of the fixed landing light assembly
Lamp
Container
Q5559
Figure 3.7: Section through the lamp retainer
The lens of the fixed assembly is bolted in front of the lamp retainer as can be viewed
in Figure 3.8.
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Runway
turnoff light
Lens
Figure 3.8: Lens assembly in front of the fixed landing light lamp
3.2.3 Dimensions of the assembly
As of yet the exact dimensions of the fixed landing light assembly are unknown. But
since the dimensions of the PAR64 lamp are well known and also the lamp retainer is
just a sort of a clasp which pins the lamp in tight position, it is not very essential to
have these exact dimensions. In order to redesign the current assembly it suffices to
know the lamp dimensions.
3.2.4 Material of the assembly
The assembly (lamp retainer and edge of the lens) is most probably of the same
material as the retractable landing light, which is the aluminum alloy T6061.
3.3
Operating environment
According to the flight manual of the Boeing 737-NG, the landing lights should be
extended and operated when the aircraft reaches a minimum height of 10,000 feet or
3,048 meter MSL (Mean Sea Level) during approach and landing procedures. Also
during take-off procedures, the landing lights should be in extended position and
operating until the aircraft reaches a minimum height of 10,000 feet.
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3.3.1 Temperature
At 10,000 feet or equivalently 3,048 meters MSL, the ambient temperature is around
-4.8 °C. This can be verified by a calculation which involves the troposphere lapse
rate of -0.0065 °C/m (or K/m), i.e. the rate of decrease in temperature with height in
the altitude region of 0 to 11,000 meter. Taking an MSL ambient temperature value of
15 °C, the ambient temperature at 3,048 meter is:
15 − (0.0065 ⋅ 3048) = −4.812°C = 268.338K
3.3.2 Atmospheric pressure
The atmospheric pressure at which the landing lights operate can be found by
consulting data sheet of atmospheric pressure versus altitudes. One could also
calculate the pressure values with an equation relating pressure to altitude above
MSL. Within the troposphere, this equation – the Barometric formula – relates
atmospheric pressure p to altitude h according to:
g ⋅M
 L ⋅ h  R ⋅L

p = p 0 ⋅ 1 −
T
0 

With:
Parameter
p
p0
L
T0
h
g
M
R
Description
Atmospheric pressure at altitude h
Sea level standard atmospheric pressure
Temperature lapse rate
Sea level standard temperature
Height above Mean Sea Level
Earth-surface gravitational acceleration
Molar mass of dry air
Universal gas constant
Value
-- Pa
101325 Pa
0.0065 K/m
288.15 K
-- m
9.80665 m/s2
0.0289644 kg/mol
8.31447 J/(mol∙K)
Using this equation and belonging constants, the atmospheric pressure values which
need to be considered are calculated to the range of:


0 meter MSL: p = p 0 = 101325Pa
3,048 meter MSL:
 0.0065 ⋅ 3048 
p = 101325 ⋅ 1 −

288.15 

9.80665⋅0.0289644
8.31447⋅0.0065
= 69682.1306Pa
3.3.3 Air density
In order to calculate air density, the Ideal Gas Law equation should be applied.
Before this gas law equation can be used, the temperature must first be converted in
degrees Celsius to degrees Kelvin by simply adding 273.15 to the Celsius
temperature reading. The Ideal Gas Law states:
LED Landing Light │ Design, Certification & Production
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ρ air =
p
T ⋅Ra
With:
Parameter
ρ air
T
Rw
Ra
Description
Air density
Temperature at altitude h
Gas constant for water vapor
Gas constant for air
Value
-- kg/m3
-- K
461.5 J/(kg∙K)
287.04 J/(kg∙K)
Hence, using the Ideal Gas Law, the air density values which need to be considered
are calculated to the range of:


101325
= 1.2251 kg/m 3
288.15 ⋅ 287.04
69682.1306
3,048 meter MSL: ρ air =
= 0.9047 kg/m 3
268.338 ⋅ 287.04
0 meter MSL: ρ air =
3.3.4 Absolute and relative humidity
Absolute humidity is the density of water vapor in the air (kg/m3): the mass of water
vapor per unit volume of total air and water vapor mixture. To calculate absolute
humidity, the dew point temperature (in degrees celcius) should be used together
with August-Roche-Magnus formula, to calculate the actual vapor pressure in
millibars or hPa. It is assumed that the air is completely saturated with water vapor,
so the dew point temperature is equal to the air temperature and consequently the
relative humidity (RH) is 100%.
Then the actual vapor pressure should be converted in millibars/hPa to Pa by
multiplying by 100. Once the actual vapor pressure is obtained in Pa, the gas law as
discussed above can be used to calculate the water vapor density (i.e. absolute
humidity) by substituting R w in place of R and by using the vapor pressure in the gas
law formula, rather than the total atmospheric pressure.
The gas constant for water vapor R w should be used when calculating the absolute
humidity, since the effect of pure water vapor has to be taken into account. The
August-Roche-Magnus formula states:
 17.625 ⋅ Td 

e w = 6.1094 ⋅ exp
 Td + 243.04 
With:
Parameter
ew
Td

Description
(Actual) water vapor pressure
Dew point temperature at altitude h
Value
-- hPa
-- K
0 meter MSL:

 17.625 ⋅ 15 
e w = 6.1094 ⋅ exp
 = 17.0198hPa = 1701.98Pa
 15 + 243.04 
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

ρ w = AH =
3,048 meter MSL:


ew
1701.98
=
= 0.0128kg/m 3
T ⋅ R w 288.15 ⋅ 461.5
 17.625 ⋅ (−4.812) 
 = 4.2794hPa = 427.94Pa
e w = 6.1094 ⋅ exp
 (−4.812) + 243.04 
ew
427.94
ρ w = AH =
=
= 0.0035kg/m 3
T ⋅ R w 268.338 ⋅ 461.5
Would the relative humidity decrease (below 100%), the dew point temperature
decreases as well, which results in a decrease of the actual water vapor pressure.
Consequently the Ideal Gas Law equation indicates that the water vapor density ρ w ,
i.e. the absolute humidity (AH), also decreases.
3.4
Operating time
The lifetime of the LED packages are strongly correlated with the junction
temperature at which these packages are operated. In order to determine the
junction temperature for which the LED lamp will be designed, this section discusses
an assessment of the operating time of the landing lights over the lifetime of an
aircraft. The operation of landing lights during takeoff procedures differs from landing
procedures and both depend on whether the lights are operated during daytime or
nighttime.
3.4.1 Operating time per procedure
A reasonably accurate estimation of the operating time of the landing lights per
takeoff and landing procedure can be viewed in table 3.1. These data are given by a
KLM engineering pilot and captain of the Boeing 737 [Frank Mannaerts, KLM Flight
Operations SPL/NV].
Fixed landing light
Retractable landing light *1
Takeoff
6 min.
-
Landing
10 min.
10 min.
Total
16 min.
10 min.
Table 3.1: Operating time landing light B737 per procedure
In case of a missed approach another 10 minutes should be added to the landing
procedure, though this happens seldom; at most once a week.
3.4.2 Average operating time per year
To know the daily average operating time of the landing lights, the amount of flights
per day for a Boeing 737 aircraft is calculated by assessing the number of landings
during last year – from January 1st, 2012 to January 1st, 2013 – of each aircraft (i.e.
per aircraft registration) of both the KLM and Transavia Boeing 737 fleet. This data
can be viewed in Appendix B.
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The average number of daily landings (i.e. number of daily flights) for each Boeing
737 aircraft registration is then determined by dividing the number of landings during
last year by 366 days*2 (2012 is a leap year). Adding all these average landings per
aircraft and dividing that by the amount of aircrafts in the B737 fleet, a good
estimation of the average daily flights of the Boeing 737 can be found (for KLM as
well as Transavia).
The results are summarized in table 3.2:
Average daily flights
KLM
5
Transavia
4
Table 3.2: Average daily flights of the Boeing 737 per fleet
Taking the largest average of 5 flights per day (KLM), a straightforward calculation is
made to determine the yearly average operating time of the landing lights:
Yearly avg. = (Normal Landing ) + (Missed Approach )
(5 ⋅ 16 ⋅ 365) + (52 ⋅ 10)
=
60
= 495.33 hours
Considering an in-service lifetime of 25 years before the aircraft is taken out of
service, the total operating time during service is:
Total operating time = 495.33 ⋅ 25
= 12383.33 hours
Rounding this figure up to 20,000 hours operating time would be equivalent to an
aircraft lifetime of 40 years.
*1 The retractable landing light is only operated at night, during takeoff.
*2 Since some B737 aircrafts started operation later than January 1st, 2012, some yearly averages had
st
to be divided by the number of days since operation until January 1 , 2013 (so less than 366 days). This
is the reason why first the daily average had to be determined before assessing the yearly average
operating time of the landing lights of the whole Boeing 737 fleet (KLM and Transavia).
LED Landing Light │ Design, Certification & Production
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4.
Preliminary LED lamp design
This section will explain the design procedure which is taken to come up with a
preliminary LED lamp design for the landing lights of the Boeing 737-NG. Although
purely conceptual, it forms the foundation of any further development on the design.
All aspects of the previous section concerning LED systems will be adopted and
refined to match the landing light application.
4.1
Design requirements
Each landing light should be designed and installed according to the criteria
described in EASA’s Certification Specifications for Large Aeroplanes CS-25:
reference parts §25.1383(a), (b), (c) and §25.773(a).
The requirements in the abovementioned references of CS-25 do not contain any
detailed information about the design parameters, such as the required light output,
beam angle, color temperature, color rendering, etc. Furthermore, according to
Boeing’s representative at KLM, Frank Marcott [24], it is highly unlikely that Boeing
will give any such proprietary data to its customers, since it is dedicated to protect
their own production. However, keen on knowing the minimum requirements for the
lamps so that the pilots are able to perform their duties (as stated in FAR's and
EASA’s Certification Specifications), the author of this report sent out a Service
Request with SR number: 1-2411922410 to Boeing with the following request:
“We would like to extend our 'Qualified Equipment Parts' list for the lamp
types Q4559x and Q5559 (halogen Sealed Beam PAR64) by exploring
available LED solutions. These lamps are used on the landing lights of e.g.
the Boeing 737. In order to appropriatly qualify the lamps for service, it is
essential to know the light output requirements considering visibility aspects,
i.e. the minimum beam angle (vertical and horizontal), color rendering and
intensity (in Candela or lumens). These requirements are not readily available
in the documentation. The best description can be found in the 'Certification
Specifications for Large Aeroplanes CS-25', stating:
CS 25.1383 Landing lights
(a) Each landing light must be approved, and must be installed so that
(1) No objectionable glare is visible to the pilot;
(2) The pilot is not adversely affected by halation; and
(3) It provides enough light for night landing.
(b) Except when one switch is used for the lights of a multiple light installation
at one location, there must be a separate switch for each light.
(c) There must be a means to indicate to the pilots when the landing lights are
extended.
Kindly advice. Thank you for your consideration.”
The response from Boeing on this Service Request was:
“here is no minimum required for lumination levels, intensity, and photometric
for the landing lights. However, there is the guidance provided in SAE
document which is SAE-ARP-963.”
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However, this response contains a typographical error, since the SAE document
which provides guidance is SAE-ARP-693.
4.1.1 CS 25.773(a)
This part of EASA’s ‘Certification Specifications for Large Aeroplanes CS-25’ states
[22]:
CS 25.773
Pilot compartment view
(a) Non-precipitation conditions. For non-precipitation conditions, the following
apply:
(1) Each pilot compartment must be arranged to give the pilots a
sufficiently extensive, clear, and undistorted view, to enable them to
safely perform any manoeuvres within the operating limitations of the
aeroplane, including taxiing, takeoff, approach and landing.
(2) Each pilot compartment must be free of glare and reflection that
could interfere with the normal duties of the minimum flight crew
(established under CS 25.1523). This must be shown in day and night
flight tests under non-precipitation conditions.
4.1.2 CS 25.1383(a), (b), (c)
This part of EASA’s ‘Certification Specifications for Large Aeroplanes CS-25’ states
[22]:
CS 25.1383 Landing lights
(a) Each landing light must be approved, and must be installed so that –
(1) No objectionable glare is visible to the pilot;
(2) The pilot is not adversely affected by halation; and
(3) It provides enough light for night landing.
(b) Except when one switch is used for the lights of a multiple light installation
at one location, there must be a separate switch for each light.
(c) There must be a means to indicate to the pilots when the landing lights are
extended.
4.1.3 SAE ARP693 REV. D
This Aerospace Recommended Practice (ARP) document is issued by Society of
Automobile Engineers (SAE) Aerospace on 1961-06, reaffirmed on 2006-06 and
revised on 2012-03. It is titled: ‘Landing and Taxiing Lights - Design Criteria for
Installation.’
It includes requirements of installations of adequate landing and taxiing lighting
systems in aircraft of several categories, among them large multiengine turbojets.
The purpose of the document is to provide certain basic considerations and design
criteria for installation of landing and taxiing light systems for night operation. See
Appendix D for the complete document.
The following publications form a part of this document to the extent specified therein
[25]:
 SAE publications:
 AS580: Pilot Visibility From the Flight Deck Design Objectives for
Commercial Transport Aircraft
LED Landing Light │ Design, Certification & Production
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ARP6402: LED Landing, Taxiing, Runway Turnoff, and Recognition
Lights
 J1330: Photometry Laboratory Accuracy Guidelines
FAA Publications:
 14 CFR Part 25, Airworthiness Standards: Transport Category
Airplanes
 14 CFR Part 121, Certification and Operations: “Domestic, Flag and
Supplemental Air Carriers and Commercial Operators of Large
Aircraft”
 Aeronautical Information Manual 4-3-23. Use of Aircraft Lights section
c.
 Federal Aviation Administration Advisory Circular AC 25-7A Flight Test
Guide for Certification of Transport Category Airplanes


4.1.4 SAE ARP6402 REV. A
This Aerospace Recommended Practice (ARP) document is issued by Society of
Automobile Engineers (SAE) Aerospace on 2011-06 and revised on 2011-11. It is
titled: ‘LED Landing, Taxiing, Runway Turnoff, and Recognition Lights.’
This document is almost nearly the same as the previous one (ARP693), except it
focuses on LED. It provides guidance material for the design, qualification,
certification and use of LED based Landing, Taxiing, Runway Turnoff Lights, and
Recognition Lights. This document can be viewed in Appendix E.
The following publications form a part of this document to the extent specified therein
[26]:
 SAE publications:
 ARP6253: LEDs and Aircraft Applications
 ARP693: Landing and Taxiing Lights - Design Criteria for Installation
 J1330: Photometry Laboratory Accuracy Guidelines
 FAA Publications:
 Federal Aviation Regulations, Part 25, Airworthiness Standards:
Transport Category Aircrafts
 Federal Aviation Regulations, Part 121, Certification and Operations:
“Domestic, Flag and Supplemental Air Carriers and Commercial
Operators of Large Aircraft”
 Federal Aviation Administration Advisory Circular AC 25-7A Flight Test
Guide for Certification of Transport Category Airplanes
4.1.5 SAE guidance outline
Both SAE documents of sections 4.1.3 and 4.1.4 provide to a great extent the same
general provisions and detailed recommendations for landing light design [25] [26]:
 Landing lights are used primarily to provide ground reference information
during final approach, touchdown, ground roll, and takeoff, and to illuminate
any major obstructions in the airplane’s approach glide path or on the runway
at night.
 It may also be used for signaling purposes in flight. The landing lights may be
turned “on” when:
 Operating within 10 miles of any airport, day or night
 Operating in conditions of reduced visibility, i.e. haze, dust, etc.
 Operating under special visual flight rules (VFR) conditions
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Operating where flocks of birds may be expected (coastal area,
swamp lands, migratory areas, etc.)
Each landing light should provide sufficient illumination of the runway for night
landings. As a design objective, 21.5 lux (2 ft-c) minimum at 122 m (400 ft) in
front of the pilot at touchdown attitude and 5.4 lux (0.5 ft-c) minimum at 91 m
(300 ft) in front of the pilot during ground roll should be provided. Lux (ft-c)
levels are measured normal to the light beam.
The minimum recommended number of landing lights required for night flying
with large multiengine turbojets are 4. This quantity refers to equipment
installations only and should not be misinterpreted as quantities required for
aircraft dispatch (see section 4.1.6: Minimum Equipment List).
Color to be white. Flight test for certification should include an assessment to
determine adequate color discrimination for runway and taxiway signs as well
as color contrasts between the pavement and the surrounding environment
for the proper orientation of the aircraft on the runways and taxiways.
The amount of ultraviolet light should be considered due to possible negative
effects on materials and observers.
LEDs generally do not fail catastrophically, but experience gradual
degradation in light output over time. The rate of degradation is dependant
upon many factors including, the LED component materials, drive current,
operating environment and LED junction temperature. Due to the lack of a
hard failure point, it is desirable to define the photometric end of life (EoL).
EoL can be defined as a percentage of initial output (70% for many
applications), or the length of operational time until the light no longer meets
defined minimum intensities. Because photometric margin and life can be
impacted by adjusting package size, weight, power and cost, establishing
specific values / requirements for life is not appropriate as these requirements
can be market / platform / installation specific. An appropriate EoL
requirement does, however, need to be considered during the design /
installation process in order to ensure that the lights will meet their intended
function for the duration of their rated life.
Icing, humidity, and condensation should be considered in the design of the
lighting system due effects on system performance. Appropriate draining
and/or venting are recommended.
Warm up and stabilization: For purposes of demonstrating compliance with
this specification, all photometric and color measurements shall be made after
a minimum warm up period (30 minutes for LED sources, 90 seconds for
incandescent/tungsten halogen light sources), or after the light has reached
thermal stabilization, whichever is longer. Stabilization shall be defined as the
point in which light output does not change by more than 3% over a 15 minute
period.
It is recommended that adequate landing light aiming and illumination be
provided to cover the following airplane attitudes:
 Prior to touchdown, the pilot will start using the lights as he initiates
the flare. The landing lights shall be aimed somewhat ahead of the
pilot’s vision limit, and along the glide slope (figure 4.1).
 Before the point of touchdown is reached, the airplane is positioned in
a nose up attitude and the centerline of the beam moves further down
the runway relative to the pilot’s field of vision. At touchdown, it is
desirable to provide illumination of the runway centerline and possible
obstructions as far as 122 m (400 ft) away from the pilot (figure 4.2).
 After touchdown, the nose wheel gradually drops to the ground and
the airplane assumes a ground roll attitude. At this point, it is desirable
to provide illumination of the runway centerline at least 91 m (300 ft)
away from the pilot (figure 4.3).









LED Landing Light │ Design, Certification & Production
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Crosswind conditions should be considered in design of landing light
installations.
It is recommended that the landing light fixture contain provisions to orient the
lamp to assure that the correct horizontal and vertical beam pattern is
achieved according to table 4.1. The performance levels in this table may be
used as guideline in the design of LED landing lights. Recommended end of
operating hours is 1000 hours minimum. Power consumption and heat
loading should be taken into account in design of wiring, circuit protection,
and enclosure materials.


Lamp Class
Volts
Beam
Maximum
Candela on
Centerline
5
6
7
28
28
28
600000
800000
300000
Minimum
Horizontal
Nominal
Beam Spread
to 10% of
Center Beam
Candle Power
(deg)
12
12
15
Minimum
Vertical
Nominal
Beam Spread
to 10% of
Center Beam
Candle Power
(deg)
12
6
9
Table 4.1: Lamps for landing service of large multiengine turbojets [26]
The lamp classes listed in table 4.1 represent current industry usage typical for this
type of installation with incandescent light sources. Performance levels found to be
acceptable in flight test may take the place of the recommendations found in table
4.1 [26]. Please note that lights do not always conform to their specification sheet
performance levels. Performance will be affected if cover lenses are used.
Figure 4.1: Landing light at approach attitude
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Figure 4.2: Landing light at touch down attitude
Figure 4.3: Landing light at ground roll attitude
4.1.6 Minimum Equipment List
One Inoperative Per Side
According to Section 2 Part 33-08A of the Minimum Equipment List (MEL), four
landing lights should be installed, but 2 are required to operate. One may be
inoperative on each side provided one of the two operating lights is in the fixed
position [27].
Day Operations
According to Section 2 Part 33-08B of the Minimum Equipment List (MEL) four
landing lights should be installed, but none are required to operate, i.e. all lights may
be inoperative for day operations [27].
4.2
Reverse engineering
Section 4.1 provides clear guidance material of how to design the new LED lamp.
However, there a no specific design details described. As such, part of the design is
a reverse engineering procedure of the currently used PAR 64 lamp (Q5559). Other
aspects should be designed within the guidelines provided by SAE Aerospace. The
probability of designing a sound airworthy product is much larger by making sure the
design stays within the limits given by these guidelines.
Reverse engineering and staying within the SAE Aerospace guidelines, provide solid
ground to develop a design for a LED lamp that offers the same functionalities as the
LED Landing Light │ Design, Certification & Production
Page 29
original halogen lamp. In order to go about this issue, several reverse engineering
parameters will be discussed in the remainder of this section.
4.3
Drop-in replacement (Retrofitting)
Another important aspect which should be taken care into account during the
preliminary design is that the certification for airworthiness of the new LED lamp will
be significantly simplified when it is designed as a drop-in replacement for the current
halogen lamp of the landing lights. Compared to the to-be replaced device, such
retrofit solutions are equivalent in performance, functionality and compatibility.
By upholding this condition it is readily clear that (major) changes to the assembly
are not part of the new LED lamp design. The only part of the assembly that is
allowed to be redesigned is the PAR 64 Sealed Beam halogen lamp, since this is the
part which will be replaced by a drop-in LED lamp.
This means that the new LED lamp should be mechanically and functionally
compatible with the current fixtures, i.e. the lamp should be of the same form and fit
as its PAR64 Sealed Beam counterpart.
4.4
PAR 64 Sealed Beam halogen lamps
The current lamps inside both the fixed and retractable fixtures are of the Sealed
Beam PAR 64 type. PAR stands for Parabolic Aluminized Reflector. The digits
behind the letter PAR indicate the nominal diameter of the lamp in inches when
dividing this number by 8. As such, a PAR 64 has a nominal diameter of 8 inches,
which is equivalent to 203.2 mm.
In order to reverse engineer a drop-in design for the landing lights, the datasheets of
the lamp GEQ4559x and GEQ5559 are consulted. Genaral, photometric, electrical
and dimensional characteristics are extracted from of the relevant data sheets and
shown in table 4.2 [2].
GEQ4559x
GEQ5559
Sealed Beam - PAR
PAR64
Screw Terminals
Aircraft; Very Narrow Spot
CC-6
Halogen
 100 hrs
Sealed Beam - PAR
PAR64
Screw Terminals
Aircraft
CC-6
Halogen
 200 hrs
Photometric characteristics
Beam Spread – Horizontal
Beam Spread – Vertical
Max. Beam Candlepower
11 degrees
7.5 degrees
 765,000 Candela
11 degrees
7.5 degrees
 650,000 Candela
Electrical characteristics
Wattage
Voltage
600 Watt
28 Volt
600 Watt
28 Volt
General characteristics
Lamp type
Bulb
Base
Primary Application
Filament
Product Technology
Rated life
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Dimensions
Maximum Overall Length
Bulb Diameter
3.7500 in / 95.2 mm
8.0000 in / 203.2 mm
3.7500 in / 95.2 mm
8.0000 in / 203.2 mm
Table 4.2: General Electric Quartzline® PAR64 - Aircraft; Very Narrow Spot
The complete dimensional depiction of the PAR 64 halogen lamp used in the landing
lights fixture is shown in figure 4.1.
95.2 mm
203 2 mm
Figure 4.1: Dimensional depiction of the PAR 64 halogen lamp
There are two different characteristics between both lamps: the Rated life and the
Max. Beam Candlepower. GEQ5559 is a qualified part to replace GEQ4559x and its
lifetime is doubled, though at the expense of the light output, which is reduced by
15% compared to its predecessor GE4559x.
4.5
Light output: from Luminous Intensity to Luminous Flux
According to the product data sheet, the lowest amount of light output is produced by
GEQ5559, with a total of 650,000 Candelas. Candela (cd) is a unit for luminous
intensity. Light output of LED chips/packages is almost always given in lumen (lm),
which is a unit of light power flux or luminous flux. Before proceeding on reverse
engineering the light output, more elaboration on those two photometric units is
needed.
Light power (luminous flux) is measured in lumens. You could measure it in watts,
but the lumen is specifically weighted to the human eye response. A watt of light
power at 700nm (verging on infrared) is much less bright than 1W at 400nm.
A lumen at 700nm would be the same brightness as a lumen at 400nm, but would
correspond to a different amount of power.
The unit of Luminous intensity or brightness is the lumen/steradian or candela (or
candlepower). This is the angular distribution of the luminous flux. Imagine the light
flux concentrated in a cone of variable plane angle θ (i.e. beam angle) as depicted in
figure1.1. The narrower the cone, the brighter the light for the same source power.
The SI unit of solid angle is the steradian (sr), but thinking in terms of this is difficult,
so it is useful to write a conversion equation which relates plane angles (unit:
radians) to solid angels (unit: steriaden):
Solid angle [sr.]

 1 
Ω = 2π 1 − cos θ  
 2 

LED Landing Light │ Design, Certification & Production
θ = angle of cone [rad.]
Page 31
Where Ω is the solid angle and θ is the plane angle of the cone [3].
Figure 4.2: Relation between Plane Angle θ and Solid Angle Ω
Luminous intensity or “brightness” is the lumen/steradian or candela (or
candlepower):
Luminous Intensity =
Luminous Flux
Solid angle
So in order to convert the luminous intensity of GEQ4559X to luminous flux, the solid
angle of the light beam from this halogen lamp is needed. An accurate approximation
of this solid angle can be calculated by taking the average beam spread angle of the
horizontal and vertical values given in de lamp’s datasheet (Table X.X), which leads
to an average plane angle θ of the emitted light beam:
θ=
11 + 7.5
= 9.25 deg rees
2
Using the relation between plane angle θ and solid angle Ω as given:
Taking the mean Beam Spread angle θ = 9.25 deg. this corresponds to:
Luminous Flux = Luminous Intensity ⋅ Solid Angle =

 1 (11 + 7.5)  
765000 ⋅ 2 π ⋅ 1 − cos ⋅
  = 15651.41778 lm
2

2

Taking the maximum Beam Spread angle θ = 11 deg. this corresponds to:
LED Landing Light │ Design, Certification & Production
Page 32
Luminous Flux = Luminous Intensity ⋅ Solid Angle =

1

765000 ⋅ 2 π ⋅ 1 − cos ⋅ 11  = 22128.80216 lm
2


Taking the minimum Beam Spread angle θ = 7.5 deg. this corresponds to:
Luminous Flux = Luminous Intensity ⋅ Solid Angle =


1
765000 ⋅ 2 π ⋅ 1 − cos ⋅ 7.5   = 10291.37827 lm

2

There is a 115% difference between the luminous flux values related to the maximum
(horizontal) and minimum (vertical) beam spread angles. Since this difference is too
large, the author of this report chooses to use the average spread angle value of θ =
9.25 degrees and related luminous flux value of 15,651 lumens as the reversed
engineered solution for the beam angle used in the conversion of the light output of
the PAR64 Sealed Beam lamp with the least amount of light output.
4.6
Luminous efficacy
Luminous efficacy is the ratio of luminous flux (SI Unit: lumens [lm]) emitted to the
electrical power used to power the light source (Watt), i.e. lm/W. The higher the
luminous efficacy the more efficient a light source operates. Measuring luminous
efficacy (lm/W) this way is useful for lighting applications, as it takes into account how
much power is wasted on the generation of heat and non-visible electromagnetic
radiation, instead of visible light.
Figure 4.3 shows that the trends and forecasts for the luminous efficacy of several
lighting applications. While traditional lighting technologies are relatively mature and
offer less potential for improvement, LED technology – and Solid State Lighting in
general – is still at a comparatively early stage and continues to achieve remarkable
advances in efficacy. The theoretical efficacy limit for white LEDs (using a blue LED
and yellow phosphor) is around 263 lm/W [4].
LED Landing Light │ Design, Certification & Production
Page 33
Figure 4.3: Luminous efficacy trends and forecasts of lighting applications
In order to design for a drop-in LED lamp, scheduled for production in 2013/2014, the
author of this report (conservatively) approximates the luminous efficacy at that time
to be 150 lm/W at practical forward currents. In fact: Cree, Inc., one of the most
renowned LED manufacturers, was the first to break the 200-lm/W barrier in
February 2010 for white power LEDs [5] and in 2012, Cree announced a white LED
giving 254 lumens per watt. However, it is relevant to notice that these values were
established during laboratory tests at (very) low forward currents of several tens of
milliamps. A high-brightness LED reaches its peak efficiency at a few tens of
milliamps and thereafter, it’s all downhill. This phenomenon, which causes efficiency
to drop as drive current is increased, is known as ‘efficiency droop’.
As such, to achieve a light output of 15,650 lumens, the total power consumption will
be roughly 105 Watt, according to:
15650
= 104.33 Watt
150
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Figure 4.4: Electrical power consumption as a function of Luminous Flux plotted [1]
The slope of the LED curve in figure 4.4 is approximately:
16
= 0.00941 W/lm
1700
Needing a total of 15650 lumens as light output, results into a power consumption of:
16
⋅ 15650 = 147.29 Watt
1700
The data of the graph in figure 4.4 suggest a luminous efficacy of 1700 ÷ 16 = 106.25
lm/W, which does not correspond any more with the data of the graph presented in
figure 4.3, since the latter suggests a value of 125 lm/W for white LED in 2012/2013.
However, when considering the most recent LED datasheets from Cree – one of the
most prominent LED manufacturers – one can not help but notice that the predictions
of both figures 4.3 and figure 4.4 are not quite accurate anymore. For example:
according to CREE’s latest datasheet update of December 18th, 2012 [6]: Cree®
XLamp® MK-R LEDs are capable of delivering up to 200 lm/W [7]. The minimum
luminous flux of this LED package is 1200 lumens (Group Code K2), at a typical
forward current of 700 mA, a typical forward voltage of 11.7 V and junction
temperature T J = 85 °C. A quick calculation suggests that at the present time the
actual total power consumption of the LED landing light should be around:
15650
⋅ 11.7 ⋅ 0.7 = 106.81 Watt
1200
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It is self-evident that this power consumption shall only decrease with future LED
package releases. Presently, the luminous efficacy of Cree® XLamp® MK-R is:
1200
= 146.52 lm/W
11.7 ⋅ 0.7
and a total of 13 of those LED packages are needed in order to meet the condition of
generating a light output of 15,650 lumens:
n LED =
15650
= 13
1200
Hence, this study assumes the following:
 A power consumption value of 100 Watt
 A luminous efficacy of 150 lm/W
 Number of LED packages to be used for further analyses and modeling is 13
4.7
LED package parameters
This section briefly describes the properties of the LED packages which are part of
the LED array in the LED module. These properties are of interest in order to be able
to come up with a preliminary design. More elaboration on the actual airworthiness
requirements for the landing light equipment can be found in section 4.1 of this
report.
4.7.1 Light output
As was concluded in section 4.4, the landing lights operate at a very high light output.
As such, the only LEDs which could be used in the drop-in LED lamp are of the
(very) high brightness type with a high luminous flux and luminous efficacy in order to
minimize the power supply and the heat dissipation rate.
4.7.2 Thermal performance indicators
An important aspect of LED package/chip selection concerns the thermal
performance of this product. This thermal performance is summarized by a heat
property indicator for LED packages called the Thermal Resistance of a package.
The thermal resistance indicates the temperature difference across a structure which
resists a heat flow through it in unit time. The SI unit for thermal resistance is
consequently expressed as °C/Watt. For LED packages the thermal path across
which the thermal resistance values are given, lies between the chip’s junction and
the solder point below the package’s thermal heat sink (see figure 2.2). The lower the
thermal resistance, the lower the temperature variation across the LED’s structure,
and thus the better the performance due to a lower junction temperature. A low
junction temperature is crucial for a longer lifetime and increased light output per
Watt (luminous efficacy) of LED chips. The maximum allowed junction temperature is
the temperature above which the LED chip’s performance and physical structure will
deteriorate rapidly and irreversibly. This maximum junction temperature should
therefore be as high possible and not be reached in any circumstances.
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To date, LED manufacturers are capable of designing LED packages with a thermal
resistance as low as 0.8 °C/W [8].
Another important thermal performance indicator is the ‘Temperature Coefficient of
Voltage’ in mV/°C. This indicator’s value is usually negative. It indicates the drop in
forward voltage in a LED package with increasing junction temperature T j . Due to the
linear relation between the forward voltage and forward current; this would mean that
also the forward current and hence the luminous flux decrease. A low a value of
Temperature Coefficient of Voltage’ is therefore important. LED chips manufactured
nowadays have temperature coefficients of voltage ranging between -1 and -15
mV/°C.
4.7.3 Design simplicity and versatility
The design of a LED lamp is a process with many aspects which need to be
considered to make a sound and technical attuned device. The more aspects and
technical difficulties the design should overcome, the more complicated and
expensive the product will be. In addition; the design freedom would become too
restricted. Hence, technically feasible simplifications or eliminations of
processes/components in order to simplify the design are very much encouraged.
Several ways to simplify a LED lamp design process are by:
 Reducing the thermal path of the dissipating heat rate by minimizing the
number of components in the LED module design. This results in a lower total
thermal resistance, which optimizes the heat sinking potential.
 Enabling redundancy by designing the LED module to run at a lower current
by adding extra LEDs to the array. As such, any LED package failure shall be
compensated by automatically running the rest of the packages at a higher
current in order to keep producing equal pre-failure light output.
 The design should be maintenance friendly and easy access to subparts is
essential for inspections.
4.7.4 Color temperature
Color temperature can be described as a method of describing the color
characteristics of light by measuring it in degrees of Kelvin (°K), usually either warm
(yellowish) or cool (bluish). More specifically it is the temperature of an ideal black
body radiator that radiates light of comparable hue to that of the light source.
Quartz halogen lamps, such as GEQ4559X, have color temperatures ranging
between 3000 - 3500 K. So in order to reverse engineer a design for the Boeing 737NG landing lights, it is important to select a LED package which emits light with a
color temperature in that range. Too much below it will result in a warmer/yellowish
white color and too much above this range results in a cooler/bluish one. Daylight
has a color temperature ranging between 5500 - 6500 K. Figure 4.5 shows the
variation of temperature colors of several types of light sources.
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Figure 4.5: Color temperatures of several types of electric light sources
LEDs have higher luminous flux values when operated at higher color temperatures.
The considered color temperature values for this research are between 3,000 K en
6,000 K.
4.7.5 Robustness
As LEDs are solid state, they inherently perform well in a high vibration environment.
It is however of similar importance to make the complete LED system robust as well.
The LEDs should be able to be mounted with (soldering) techniques capable of
resisting vibration accelerations up to the levels prescribed by the ‘Random Test
Procedure’ in section 8.2.5 of the Environmental Conditions and Test Procedures for
Airborne Equipment (RTCA DO-160G) document [31]. This particular test procedure
holds also for the remaining part of the light system, such as the optics and thermal
and electrical components.
4.7.6 Operating temperatures
The range of operating temperatures of the LED packages should at least include the
Operating Low Temperature and the Operating High Temperature for equipment
category B2 as provided by section 4 of the Environmental Conditions and Test
Procedures for Airborne Equipment (RTCA DO-160G):
Equipment intended for installation in non-pressurized and non-controlled
temperature locations on an aircraft that is operated at altitudes up to 25,000 ft
(7,620 m) MSL is identified as Category B2.
These temperatures are -45 °C and +70 °C, respectively. Most LED packages are
designed to easily meet the condition of the Operating High Temperature. The
Operating Low Temperature for most conventionally available LED packages
however, is always -40 °C, which is -5 °C less than required. Nevertheless, as further
research is undertaken to study the effects of cryogenic temperatures on LEDs [18],
this small set-back is not likely to form much hinder and it is expected that in the near
future this value shall meet the stated requirement for equipment category B2.
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Furthermore, notice should also be given to the Ground Survival Low and High
Temperatures of category B2, -55 °C and 85 °C respectively. The LED lamp does not
have to in operative mode at these temperature extremes, but it should be able to
survive them for a certain minimum time span, outlined in the RTCA DO-160G
document, and be operative again in the range of the Operating Low and High
Temperatures.
4.8
Thermal management
One of the most crucial aspects of designing a LED lamp is thermal management.
The LED junction temperature should be kept well under the maximum junction
temperature at all times, yet it is highly recommended to decrease this temperature
as much as possible in order to increase the lifespan and operating performance of
the LEDs.
4.8.1 Wall-plug efficiency
Overall luminous efficacy is the ratio of the amount of optical power output to the
electrical power input and is also called the Wall-Plug Efficiency (WPE).
Figure 4.6: Wall-plug efficiency curves as functions of forward current and temperature (2009)
Wall-plug efficiency or radiant efficiency is influenced by the efficiency of five
processes [9]:
 η electrical is the electrical efficiency: the electrical contacts and resistance
losses
 η IQE is the internal quantum efficiency of the active layer
 η extraction is the photon (light) extraction efficiency from the chip
 η phosphor is the phosphor conversion efficiency when making white LEDs
 η package is the light extraction out of the LED package
The total wall plug efficiency of a white LED with phosphors can accordingly be
expressed as:
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η WPE = η electrical x η IQE x η extraction x η phosphor x η package
In section 4.5 it is stated that the theoretical limit for a blue LED and yellow phosphor
is 263 lm/W (263 lm at 1 W of radiation). This is the amount of light emitted in the
visible spectrum. The rest of wavelengths are emitted in the non-visible spectrum and
considered as inefficient emission, though not a heat-producing one. So, assuming
having LEDs with a luminous efficacy of 150 lm/W, running at practical currents (in
order to generate enough luminosity), produced by the end of 2013/beginning of
2014 and including an electrical driver efficiency of about 90%; the total WPE results
in:
150
⋅ 0.9 = 0.5133 ≡ 51.33%
263
This means that about 48.67% ≈ 50% of the input power will be converted to heat.
This figure can be backed up by claims from the industry. According to Cree, Inc.
[10]: “Cree royal blue XLamp LEDs are over 50% efficient and white XLamp LEDs
are over 40% efficient. That is, under normal operating conditions, approximately
50% to 60% of the input power is output as heat, while the rest of the input power is
converted to light.”
The amount of heat flux to dissipate is thus:
15650
⋅ 0.4867 = 50.78Watt
150
To dissipate this amount of heat away from the LEDs, several thermal management
solutions are stated in the next subsections.
4.8.2 Vapor chamber and heat pipes
To transfer the heat away from under the LEDs to a spot where it can be safely and
effectively dissipated, use can be made of heat pipe technology. This fairly simple
and reliable method to conduct large amount of heat has been used in aerospace
(and many other) applications for decades. Thermal conductivity of heat pipes is up
to 90 times greater than copper for the same size (Faghiri, 1995) resulting in low
thermal resistance (Peterson, 1994). Typical thermal resistances for the high power
heat pipes range from 0.05 to 0.1°C/watt [11]. Conventional heat sinking is not
possible due to the large heat flux.
Heat is created under the LED chips at the junction. This heat flows from the junction
to the silicon substrate and from the substrate to the package's heat sink. From there
the flow path should be further extended.
The calculated heat flow of around 50 Watt can best be removed when it is evenly
spread over the surface on which the LEDs are mounted (soldered). This flattening of
temperatures will also avoid hot spots with relatively much higher (peak)
temperatures from emerging. To spread the heat the new design will make use of a
round vapor chamber (very flat heat pipe) on top of which the LEDs are directly
mounted to minimize any obstacles/resistance from hindering the heat flow to spread
effectively.
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A vapor chamber consists of a sealed vacuum vessel, with an internal wicking
structure, and a small amount of working fluid that is in equilibrium with its own vapor.
The low pressure inside the chamber allows the fluid to vaporize at a temperature
much lower than its normal boiling temperature. When heat is applied to the vapor
chamber, the fluid near that location immediately vaporizes and rushes to fill the
entire volume of the chamber (driven by pressure difference). When the vapor comes
into contact with a cooler wall surface, it condenses, and releases its latent heat of
vaporization. The condensed fluid returns to the heat source by capillary action of the
wick structure. As the vaporization and condensation cycle repeats, heat is moved for
the heat source to the entire volume of the chamber, resulting in a uniform
temperature distribution on its surface.
A vapor chamber is a high-end thermal management device that can rapidly spread
heat from a small source to a large platform of area, see figure 4.7). It has a similar
construction and mechanism as a heat pipe except that a heat pipe typically refers to
a tube that transfers heat from one single point to another (see figure 4.11), while a
vapor chamber refers to a plate that spreads heat from one point to a twodimensional area.
Comparing thermal resistances between conventional cooling systems using only a
finned heat sink and cooling systems using vapor chamber/heat pipes, the latter
system can reduce the thermal resistance by at least 56% [13]. Thermal resistance
values of high-end vapor chambers can reach values as low as 0.05 °C/W [14]. In
addition thermal diffusion of the vapor chamber is faster than the conventional
cooling system and it takes less time to reach steady state.
Figure 4.7: Working principle of a vapor chamber
There are two different methods for mounting the LEDs on the vapor chamber [12]:
1. Mounting the multi-LED chips directly over the vapor chamber
2. Printing the circuit boards over the vapor chamber, then mount the LEDs on
top using surface-mount technology
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Figure 4.8: Vapor chamber (aluminum) without any printing of mounting
Figure 4.9: Vapor chamber (aluminum) with only a printing of a circuit board
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Figure 4.10: LEDs mounted on a printed circuit board over a vapor chamber (aluminum)
The vapor chamber is firmly connected to the (retractable) fixture by a rubber sealant
to avoid it from any relative displacement/vibration.
Once the heat has been evenly spread over the mounting area, it is conducted to the
aluminum fixture – which will function as the ultimate heat sink – by four flat heat
pipes directly soldered to the bottom side of the vapor chamber or attached with a
strong thermally conductive adhesive, since the contact resistance between the
evaporator and the heat source and between the condenser and the heat sink is
relatively large and should be minimized. Refer to figure 4.11 for a demonstration of
flat heat pipes.
Figure 4.11: Flat heat pipe (copper) in different shapes and curvatures
Once the heat is transferred to the fixture trough the heat pipes, it gets dissipated to
the ambient by convection and radiation.
A graphical representation of this heat transfer concept can be seen in figure 4.12.
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LED
Vapor
chamber
Heat pipe
Retractable fixture
Figure 4.12: LEDs cooled with vapor chamber and heat pipes (cross section)
Another way which is more compatible with a drop-in solution as discussed earlier in
section 4.2, would be the same as described above, except that the condensator of
the heat pipes would now be attached to the lower side of an LED lamp shaped in
the form of the inner space of the retractable fixture, shown as part A in figure 4.2.
This form could also be in the same as that of the PAR 64 Sealed Beam lamp, but is
better to shape the lamp in a way that minimizes the distance between the lamp and
the aluminum wall of the retractable fixture. As such, improved thermal conductivity
can be achieved since the thickness of the highly thermal conductive gel, filled in the
space between the lamp and the fixture to conduct the heat away from the lamp to
the fixture wall, is also minimized. A graphical representation of this heat transfer
concept can be seen in figure 4.13.
The first concept of this subsection is preferred considering the efficiency of the
thermal conductive property of the LED lamp, as there is no need to add a filling
material to conduct the heat away from the lamp. The second concept is preferred
from a ‘drop-in solution’ point of view; no major alterations have to done in order to
achieve the required LED lamp performance.
LED
Heat pipe
Vapor
chamber
Thermal conductive gel
PAR 64 Sealed
Beam lamp
Retractable fixture
Figure 4.13: Drop-in solution with thermal conductive gel between lamp and fixture (cross section)
4.8.3 LEDs directly mounted on heat pipes
Another, more efficient approach is to directly mount the LED packages on the heat
pipes [23]. By doing so, the extra thermal resistance of the vapor chamber can be
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omitted and the dissipated heat is directly transferred to the inner surface of the
fixture through the heat pipes. This can be modeled by setting a thermal resistance of
0 °C/W for the vapor chamber in the analytical model. An example of this approach is
visualized in figure 4.14, where an example is shown of a way to attach LED
packages directly on a heat pipe while connecting them to the printed circuit board.
Because the LEDs are directly mounted on the surface of the heat pipe, the heat
generated by the LEDs is effectively delivered to the atmosphere due to reaction of
the latent heat phase transformation in the heat pipe. The heat is delivered to the
lamp fixture (heat sinks) at far sides for heat exchange so that improved heat
dissipation and a space saving result are achieved.
Figure 4.14: The LED directly attached to the heat pipe
A concept of a lamp design where the LED packages are directly mounted on the hot
ends of heat pipes can be seen in figure 4.15. In this design the cold ends of the heat
pipes are attached to a thin layer aluminum cone. This cone is connected to the
fixture by a highly conductive thermal interface material (e.g. paste/adhesive). This
allows the heat to be conducted to the outer fixture, where convection to ambient will
take place. In case the heat flux is too large for full convection to ambient, a flexible
heat pipe can transport the remaining heat to an additional heat sink, e.g. the
aluminum aircraft skin or other structural component.
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Flexible heat pipe
Aluminum fixture
Flat heat pipe
Thin layer
aluminum cone
LED packages
Figure 4.15: Concept lamp design with heat pipes (front view)
Cold plate
Hot plate
Flexible
heat pipe
Figure 4.16: Concept lamp design with heat pipes (back view)
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4.8.3 Thermal conductivity, conductance and resistance
The definition of thermal conductivity is given by:
Thermal Conductivity: A measure of the ability of a material to transfer
heat. Given two surfaces on either side of a material with a temperature
difference between them, the thermal conductivity is the heat energy
transferred per unit time and per unit surface area, divided by the temperature
difference [16].
Thermal conductivity is a bulk property that describes the ability of a material to
transfer heat. In the following equation, thermal conductivity is the proportionality
factor k, see figure 4.14, measured in units W/m·K or equivalently W/m·°C.
Figure 4.14: Conduction heat transfer process from hot (T 1 ) to cold (T 2 ) surfaces
The thermal conductivity is also called the K-value. Knowing this material-specific
value and the dimensions of the component, the C- and R-values are derived, which
are values for the thermal conductance and thermal resistance, respectively.
Thermal conductance
Thermal conductance is the quantity of heat that passes in unit time through a plate
of particular area and thickness when its opposite faces differ in temperature by one
kelvin. For a plate of thermal conductivity k, area A and thickness ∆x this is:
C=
k⋅A
∆x
measured in W/K (equivalent to: W/°C).
Thermal resistance
As the name already implies, this is a thermal-property of a material to resist the
conduction or flow of heat through it. Thermal resistance is the reciprocal of thermal
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conductance; lowering its value will raise the heat conduction and vice versa. When
thermal resistances occur in series, they are additive.
R=
1
∆x
=
C k⋅A
The superposition rule for thermal resistances applies to the heat sink design of the
new LED landing light, since the heat sink components, i.e., the vapor chamber, heat
pipes and fixture are all aligned in series. Since thermal resistance is the reciprocal of
thermal conductance, it is measured in K/W (equivalent to: °C/W).
Single chip package
At JEDEC Standard No. 51-1, thermal resistance of a single semiconductor device
(chip package) is defined as:
R JX =
TJ − TX
PD
With:
Parameter
R JX
TJ
TX
PD
Description
Thermal resistance from LED device/package junction
to the specific environment X
Junction temperature of LED device/package in a
steady state condition
Reference temperature for the specific environment X
Power (heat) dissipation in the LED device/package
Value & unit
-- K/W
-- K
-- K
-- W
Multiple heat sources
Thermal resistance of LED arrays which have multiple heat sources can be
described according to the following expression [15]:
θ ja −avg =
Tj,avg − Tamb
PT
With:
Parameter
θ ja-avg
T j,avg
T amb
PT
Description
Average junction to ambient thermal resistance
Average junction temperature of LED array
Ambient temperature
Total power (heat) dissipation of all packages
Value & unit
-- K/W
-- K
-- K
-- W
The latter equation assumes that each LED mounted on the array exhibit the same
thermal characteristics. Because the LEDs used in the design are of identical
geometry and power dissipation, the employment of the above equation is validated
in the analysis [15].
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The LEDs are mounted on a vapor chamber, thus the temperature of the vapor
chamber is assumed to be the same. The temperature difference between the
junction and the ambient is expressed as the number of i chips, namely:
∆TJi −amb = ∆TJi − vc + ∆Tvc − hp + ∆Thp −fix + ∆Tfix −amb
 n

 n

 n

= Pi ⋅ θi +  ∑ Pk  ⋅ θvc − hp +  ∑ Pk  ⋅ θhp −fix +  ∑ Pk  ⋅ θfix −amb
=
 k 1=

 k 1=

k 1 
 n

= Pi ⋅ θi +  ∑ Pk  ⋅ ( θvc − hp + θhp −fix + θfix −amb )
 k =1 
= Pi ⋅ θi + Ptotal ⋅ ( θvc − hp + θhp −fix + θfix −amb )
Where:
Parameter
∆TJi−amb
∆TJi−vc
∆Tvc−hp
∆Thp−fix
∆Tfix −amb
Pi
θi
θvc−hp
θhp−fix
θfix −amb
n LED
Description
Temperature difference between the i th chip and
ambient
Temperature difference between the i th chip and the
vapor chamber
Temperature difference between the vapor chamber
and the heat pipes
Temperature difference between the heat pipes and
the fixture
Temperature difference between the fixture and
ambient conditions
Dissipated power (heat) of the i th chip
Partial thermal resistance between the i th chip and
the vapor chamber
Partial thermal resistance between the vapor chamber
and the heat pipes
Partial thermal resistance between the heat pipes and
the fixture
Partial thermal resistance between the fixture and
ambient conditions
Number of active LEDs
Value & unit
-- K
-- K
-- K
-- K
-- K
-- W
-- K/W
-- K/W
-- K/W
-- K/W
-- / --
Because the heat is generated at the junction and flows from the vapor chamber to
the environment, P total is the sum of P i . Define ∆TJ ,avg = Tj,avg − Tamb , then it is
reasonable to assume that ∆TJ,avg =
∆TJi −amb (i = 1 ~ n). This leads to the total thermal
resistance as expressed by the following [15]:
∆TJi −amb
θ ja −avg =
Ptotal
=
Pi ⋅ θi + Ptotal ⋅ ( θvc − hp + θhp −fix + θfix −amb )
Ptotal
For a LED array system with n LED packages, this equation is simplified as:
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1
⋅ Ptotaal ⋅ θi + Ptotal ⋅ ( θvc − hp + θhp −fix + θfix −amb )
n
=
Ptotal
θ ja −avg
1
⋅ θi + θvc − hp + θhp −fix + θfix −amb
n
1
=
⋅ θi + ( θcooling )
n
=
This indicates that the increase in the number of unit package in a system results in
the decrease of total (average) thermal resistance [15].
4.8.4 Meeting the expectations
In this section a simple, straight forward approach on how to determine the correct
LED heat sink for the new LED lighting design is given. This is a simplified approach
of the integral model and verification tests has of course to be done, but it will give
enough insight to make sure both the functional integrity as well as the operational
reliability of the design will meet the marked expectations.
Each LED lighting design has its own specific parameters, therefore it is required to
take these specifics in to account and to define the exact starting points:
1. Expected ambient temperature
According to the document ‘Environmental Conditions and Test Procedures for
Airborne Equipment’ (RTCA DO-160G) the landing light equipment should be able to
be operated between the ambient temperature criteria of -45 °C and +70 °C. This
corresponds to category B2 of RTCA DO-160G section 4.3 [31].
2. Defining LED package characteristics
In order to calculate for a LED heat sink, starting/reference data on the LED
package’s characteristics are required. These are usually mentioned on the product’s
data sheets, provided by the manufacturer. As an example, a calculation is
performed with a LED package candidate from the Cree® XLamp® MK-R series:
Characteristic
Forward current
Forward voltage
Power
Thermal resistance, junction to solder point
Maximum junction temperature
Temperature coefficient of voltage
Viewing angle
Value & unit
700 mA
11.7 V
8.19 W
1.7 °C/W
150 °C
-7 mV/°C
120 °
The aim is to design a heat sink for the LED module/array containing the LED
packages with junction temperatures varying between 85 °C and 120 °C. This can be
achieved by using the iteration steps given below.
3. Calculate the required LED heat sink capacity
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The junction temperature of the LED chips can be calculated by using the thermal
resistance of the components along the heat flow path. Each part of the design adds
up some heat due to individual thermal resistances of each material. The adding up
can be calculated as ∆T = P total x θ th , with:
 ∆T: temperature increment of the relevant component [°C]
 P total : total power (heat) to be dissipated in [W]
 θ th : thermal resistance of the relevant component [°C/W]
In this case we have the thermal resistance of the Cree® XLamp® MK-R module θ i
and – as described in the previous subsection – the thermal resistance from our
cooling system θ cooling which has to make sure that the total design stays below the
maximum required junction temperature T j .
Having two junction temperatures limits and two ambient ones, there are four cases
to distinguish and investigate:
1. T j = 85 °C and T amb = 55 °C
2. T j = 85 °C and T amb = -20 °C
3. T j = 120 °C and T amb = 55 °C
4. T j = 120 °C and T amb = -20 °C
These combinations of junction and ambient temperatures are will be studied from a
thermal model, which reflects the heat transfer mechanisms that are part of the total
heat sinking process. This model is explained below and the calculations/iterations
are made in Microsoft Excel, which shows and visualizes through charts, the heat
sink component temperatures and heat rates as function of several key variables.
Now a mathematical definition of what would be the maximum thermal resistance our
cooling system ( θ cooling = θ vc−amb = θ vc− hp + θ hp −fix + θ fix −amb ) should have, or define the
maximum raise in temperature the cooling system will create when dissipating P total =
50 W.
The thermal resistance model is constructed as follows:
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TJi
θj-vc
TJi
Tvc
θvc-hp
Thp
θj-vc
Tvc
θhp-fix
Tfix1
θvc-amb
θfix1-fix2
Tfix2
Tfix2
Where:
Parameter
T Ji
T vc
T hp
T fix1
T fix2
Description
LED junction temperature
Vapor chamber temperature
Heat pipes temperature
Inner fixture surface temperature
Outer fixture surface temperature
Value & unit
-- K
-- K
-- K
-- K
-- K
The thermal resistance values θ j-vc , θ vc-hp , θ hp-fix , θ fix-amb are needed in order to push
forward with a calculation that will eventually lead to the maximum heat rate allowed
to be dissipated by the current fixture. θ j-vc is a known constant given in the datasheet
of the LED package manufacturer. θ vc-hp and θ hp-fix are usually also given by the
vapor chamber and heat pipes manufacturers respectively. Knowing the fixture
dimensions and a thermal conductivity of 200, θ fix-amb is calculated to be:
θfix1−fix 2 =
∆x fix
0.005
=
= 3.93 ⋅10−4 °C/W
k fix ⋅ A fix 200 ⋅ 0.064
Working from the top to the bottom of the thermal resistance model, an iterative
calculation process can be set up in order to find the maximum heat rate the fixture’s
outer surface can convect and radiate to ambient. Additional fins can be placed on
the fixture in order to increase the convection and radiation to ambient. As will be
verified from calculations on this model, an ambient temperature of +55 °C will
require for both junction temperatures T Ji = 85 °C and T Ji = 120 °C, extra surface in
order to convect the dissipated heat.
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Starting with a junction temperature T Ji = 85 °C
Model part
TJi
Known constant
Needed parameter
θ j-vc = 1.7 °C/W
T Ji = 85 °C
P i ≈ 11.7 ∙ 0.7 ∙ 0.5 = 4.095 W
θj-vc
T vc
TJi − Tvc= Pd ⋅ θ j− vc
Tvc= TJi − Pi ⋅ θ j− vc
Tvc =
85 − 4.095 ⋅1.7
Tvc
Tvc
θvc-hp
=
Tvc 78.058 °C
θ vc-hp = 0.05 °C/W (see section 4.7.3)
T vc = 78.05799 °C (from previous part)
n LED = 13 (see section 4.5)
P total = P i ∙ n LED = 4.095 ∙ 13 = 53.261 W
T hp
Tvc − T=
Ptotal ⋅ θvc − hp
hp
Thp
= Tvc − Ptotal ⋅ θvc − hp
Thp
Thp = 78.058 − 53.261 ⋅ 0.05
=
Thp 75.395 °C
Thp
θhp-fix
θ hp-fix = 0.1 °C/W (see section 4.7.3)
T hp = 75.395 °C (from previous part)
n LED = 13 (see section 4.5)
P total = P i ∙ n LED = 4.095 ∙ 13 = 53.261 W
T fix1
Thp − T=
Ptotal ⋅ θhp −fix
fix1
= Thp − Ptotal ⋅ θhp −fix
Tfix1
Tfix1
Tfix1 = 75.395 − 53.261 ⋅ 0.1
=
Tfix1 70.069 °C
Tfix1
θfix1-fix2
θ fix1-fix2 = 3.93∙10-4 (see this section)
T fix1 = 70.069 °C (from previous part)
n LED = 13 (see section 4.5)
P total = P i ∙ n LED = 4.095 ∙ 13 = 53.261 W
T fix2
=
Tfix1 − Tfix
Ptotal ⋅ θfix −amb
2
Tfix2
=
Tfix
Tfix1 − Ptotal ⋅ θfix −amb
2
Tfix =
70.069 − 53.261 ⋅ 3.93 ⋅10−4
2
=
Tfix 2 70.048 °C
4.8.5 Thermal convection
The last step of the previous calculation shows that dissipation of the heat rate
results into an outer surface temperature of T fix2 = 70.048 °C. From this point on, the
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thermal analyses continues with convecting the heat to ambient conditions. Now the
question arises: how much heat rate can the fixture transfer to air solely by
convection? The fixture is made of an aluminum alloy, which has a thermal
conductivity of 200 W/m∙K at 0 °C [17]. The fixture wall is approximately ∆x = 5 mm
thick. The shape of the fixture is a truncated cone (frustum) with an upper base but
without a lower base, see figure 4.15. The geometry, size and thermal properties are
such that the resistance to heat flow is much greater at the external surfaces than
internally can be treated as a lump of material cooling at uniform temperature.
r1
h
∆x
s
r2
Figure 4.15: Truncated cone (frustum)
The surface area A for a truncated cone without lower base can be calculated by the
equation (assuming a thin-walled structure):
A = π ⋅ (r1 + r2 ) ⋅ s + π ⋅ r22
Where, see also section 3.3 for the fixture dimensions:
Parameter
A
r1
r2
s
Description
Surface area truncated cone without lower base
Radius lower base of the truncated cone
Radius upper base of the truncated cone
Slant height of the truncated cone
Value & unit
-- m2
0.115 m
0.025 m
0.140 m
This results into an area A of:
A = π ⋅ (r1 + r2 ) ⋅ s + π ⋅ r22
= π ⋅ (0.115 + 0.025) ⋅ 0.140 + π ⋅ 0.025 2
= 0.064 m 2
The equation for natural or free convection by air can be expressed as:
Q = h air ⋅ A ⋅ ∆T
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Where:
Parameter
Q
h air
A
∆T = T fix2 – T amb
Description
Heat transferred per unit time
Convective heat transfer coefficient of air
Heat transfer area of the surface
Temperature difference between the outer fixture
surface and the bulk ambient air
Value & unit
-- W
5 - 25 W/m2∙K
0.105 m2
-- K
The convective heat transfer coefficient for air h air can vary significantly depending on
boundary conditions, such as:
 Velocity of the fluid
 Orientation to the flow
 Geometric shape
 Surface condition
 Viscosity
However, for natural convection h will usually be in the range of 5-20 W/m2∙K.
Typically, for natural convection in air, a value of 10 W/m2∙K is a good assumption for
an initial rough calculation [20].
Q = h air ⋅ A fix ⋅ ΔT
= h air ⋅ A fix ⋅ ( Tfix 2 − Tamb )
=⋅
10 0.064 ⋅ ( 70.048 − 55 )
= 9.561 W
This amount of heat rate is not anywhere near the required value of 53.235 W. The
reason for this is the high ambient temperature required by RTCA DO-160G
paragraph 4.3 and the particularly low junction temperature of T Ji = 85°C. Extra
surface area at the heat sink is evidently required to facilitate the heat convection of
the remaining part of the heat dissipation.
4.8.6 Thermal radiation
An additional way to dissipate the heat is by thermal radiation. For surfaces which
are not black bodies, the radiation power is calculated with the Stefan-Boltzmann
Law, expressed as:
4
Prad = ε ⋅ σ ⋅ A ⋅ Tfix
2
Where:
Parameter
P rad
ε
σ
A
T fix2
Description
Radiative power fixture
Emissivity coefficient outer surface fixture
Stefan–Boltzmann constant
Heat transfer area of the surface
Temperature outer fixture surface
Value & unit
-- W
0.5 [-]
5.670 373∙10−8 W·m−2·K−4
0.064 m2
70.048 °C
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The magnitude of radiation heat transfer is based on the emissivity coefficient of the
fixture’s material, which is the ratio of how closely its surface approximates a
blackbody. Note that the emissivity coefficient for aluminum can vary significantly
depending on the material finish, having a value that could range from 0.02 - 0.9 [20].
Hence, a mean value of 0.5 is assumed to perform the necessary calculations.
Anodizing dramatically increases the emissivity of an aluminum heat sink (up to 0.8)
[20].
It turns out that the contribution of radiation will be extremely small, compared to the
effects of convection.
Prad =0.5 ⋅ 5.67 ⋅10−8 ⋅ 0.064 ⋅ 70.0484
= 4.34 ⋅10−2 W
4.8.7 Thermal path to additional surface
As concluded in section 4.7.5, extra surface area is needed to assist in the heat
convection of the total heat dissipation. Several options are available to do so. One is
to add finned surfaces on the outer surface of the fixture.
Another way is by utilizing (flexible) heat pipes in order to transfer the heat from the
fixture to elsewhere, e.g. the aircraft’s skin or struts for the fixed lights or the nonmovable part of the assembly of the retractable lights. As such, heat convection does
not get restricted to solely the outer surface area of the (retractable) fixture and is
able to make use of the assembly’s complete surface or other aluminum parts of the
aircraft.
An example of a flexible heat pipe that could be used for the retractable lights is
shown in figure 4.16.
4.9
The results
Figures 4.16 and 4.17 show for both ambient temperatures of 70 °C and -45 °C, the
influence of additional surface area on the ability of the heat sink to dissipate the total
heat rate of 53.261 W ≈ 55 W, through natural (free) convection and radiation. It is
clear that the heat dissipation goes well for an ambient temperature of -45 °C, for
both junction temperatures of T J = 85 °C and T J = 120 °C, but the fixture outer
surface is not large enough to dissipate all the heat during an ambient temperature
condition of 70 °C (red curve). Since heat radiation is not significant for the
dissipation and in order to create a measurable shift in the heat sinking capabilities of
the fixture, it is necessary to increase the area for natural convection.
Figure 4.16 (T J = 85 °C) shows that in order to dissipate 55 W of heat in ambient
temperature conditions of 70 °C, the additional needed surface area should be ≈ 0.55
m2.
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Junction temperature T J = 85 °C
Figure 4.16: Total dissipated heat rate vs. additional surface area for T J = 85 °C
Figure 4.17 (T J = 120 °C) shows that the dissipation process of 55 W heat in ambient
temperature conditions of 70 °C, needs an additional surface area of ≈ 0.25 m2.
Adding additional surface area could be done by mounting fins on the outer surface
of the fixture. Good notice has to be taken of the available space in the landing light
assembly in case the fixture retracts during flight.
For a retrofit solution this renders a technical infeasibility from a thermal management
perspective, since te surface area of the PAR 64 lamp is smaller than the outer
fixture of the retractable assembly. This area could be increased by a fin structure,
yet this approach has its limitation with respect to the optimal fin size for a good heat
convection by air.
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Junction temperature T J = 120 °C
Figure 4.17: Total dissipated heat rate vs. additional surface area for T J = 120 °C
Table 4.3 shows the effect of increasing (arrow up) and decreasing (arrow down) of a
parameter’s value on the amount of required additional surface area for convection:
Parameter
Thermal resistance LED θ LED [°C/W]
Thermal resistance vapor chamber θ vc [°C/W]
Thermal resistance heat pipe θ hp [°C/W]
Thermal resistance fixture θ fix [°C/W]
Luminous flux LED package [lm]
Luminous efficacy [lm/W]
Driver efficiency η driver [-]
Number of LED packages n [-]
Ambient temperature T amb [°C]
Junction temperature T LED [°C]
Aluminum emissivity coefficient ε [-]
Heat transfer coefficient air [W/m2∙ K]
Beam angle [°]
Luminous intensity [cd]
Value














Add. surface area














Table 4.3: Effect of increase and decrease of parameters on additional surface area
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5.
Cost-benefit analysis
It is important to have an accurate estimation of the costs that will be invested into
the project realization process of the new LED lamp. This process encompasses the
development as well as the certification and quality assurance testing. The complete
breakdown of the development costs includes:
 The design (engineering costs)
 The production/assembling
 The certification/(environmental) testing
 The installation
Besides the development costs, there are expenditure costs resulting from the use of
the current incandescent lamp. The breakdown of these expenditure costs includes:
 Lamp costs (consumable)
 Labor costs (lamp changes)
 Costs due to delays and cancellations
An accurate analysis of these costs will enable a good assessment of the Return On
Investment (ROI) in years, taking into account the change from a consumable to a
lifetime product.
5.1
Design costs
KLM DOA is experienced, but their experience on LED design is not well enough to
engage in detailed design. As such, many aspects of the detailed design needs to be
outsourced to one or more experienced design organizations which have profound
knowledge on LED design.
Outsourcing of the (detailed) design brings along additional costs, which needs to be
taken into account during the cost-benefit analyses. However, this kind of
expenditure is hard to put a finger on, since it has quite a lot of unknowns and is
often part of a bigger process. The subparts of this post can be among others:
 Preliminary design
 Detailed design
 Computer modeling
 Redesign or (radical) design modifications
5.1.1 Outsourcing detailed design
To have an idea of the design costs, several companies have been approached to
provide quotes for the detailed design of (several important parts of the) LED lamp.
Among these parts, the heat managing apparatus and the LED driver are the biggest
and most complicated ones. The heat management part is also (for the most part)
the lamp’s luminaire/fixture. The LED driver needs to be an integrated component of
the total lamp and is required to be small enough in order to be integrated. Once this
part is realized, the following steps involve mounting and wiring of the LED packages,
plus adding a (custom designed) lens.
The companies that have been approached to present quotes are:
 Thermacore  A technical leader in design, development and manufacturing
of high-performance thermal solutions for the purpose of enabling their
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



customers’ next generation products in a range of markets, including military,
aerospace, computers, communications, power semiconductor, energy
conversion, medical and test equipment, transportation and many other
industries.
Thermacore provided a quotation for the technical feasibility study, detailed
design and unit price of the heat management apparatus (also fixture) of the
LED lamp. They have provided a preliminary design in order to prove and
show the technical feasibility of a heat dissipating fixture incorporating heat
pipe technology.
Advanced Cooling Technologies, Inc. (ACT)  A premier thermal
management solutions company, which serves customers in diverse markets
including Aerospace, Electronics, HVAC and Energy Recovery, and
Temperature Calibration and Control.
ACT provided a quotation for a technical feasibility study of developing a heat
management solution for the new LED lamp. Since this quotation was rather
high however, it is decided to continue with Thermacore, as their technical
feasibility study quotation was much lower than ACT’s.
MJM Engineering Co.  MJM Engineering Co. is an R&D and consulting
firm specialized in the cooling of electronics and telecommunication
components and systems. Areas of expertise include: heat exchanger design,
thermal system design and optimization, fluid mechanics and convection heat
transfer, and cooling of electronic systems, including phase change materials.
MJM Engineering Co. provided a quotations for the following:
 Thermal analyses (using numerical techniques) to obtain baseline
thermal performance of the device.
 Development of 3 concepts of thermal management systems of which
one will be selected for further development.
 Final full design and development (of selected concept) with thermal
modeling of the device for performance assessment.
 Preparation of detailed report.
Philips Innovation Services  Philips Innovation Services offers access to
a range of advanced innovation services, expertise and high-tech facilities
across the whole innovation process. The main services extend from concept
creation support, product and process development, prototyping and small
series production, equipment development, quality and reliability,
industrialization, right through to sustainability and industrial consulting.
Fokker Services B.V.  Fokker Services B.V. is a (Design Organization
Approval) DOA and (Production Organization Approval) POA holder and has
as an Original Equipment Manufacturer (OEM) much experience in the
aviation industry. Fokker Services is part of Fokker Technologies, which
designs, develops and produces structures, landing gears and electrical
systems for the aerospace and defense industry, and supplies integrated
maintenance services to aircraft owners and operators.
From all the companies which have been approach to provide quotations,
Fokker Services B.V. is the most interesting and attractive partner to work
with should this project continue. This due to several reasons:
 DOA holder: as an EASA DOA holder, Fokker Services B.V. is
allowed/approved to design airworthy aircraft parts, and holding, or
applying for, type-certificates, supplemental type-certificates, changes
or repairs design approvals or ETSO Authorizations.
 POA holder: due to this production approval, Fokker Services B.V.
has the approval to build and certify aircraft parts when a DOA-POA
agreement is in place, which is always the case when an organization
holds both approvals. KLM as a DOA holder needs a POA holder in
order to produce airworthy approved equipment. It still needs to be
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

decided which company/organization (KLM or Fokker Services B.V.)
would be the ultimate responsible DOA holder for the new LED lamp.
This decision depends on the sales model of the project
(make/buy/collaborate).
Experience: as an OEM, Fokker Services B.V. has lots of experience
in the (detailed) design, production and certification processes of
aircraft (electrical) equipment.
Nearby location: Fokker Services B.V. is located nearby KLM
Engineering & Maintenance. This lowers the communication threshold
between both parties considerably.
Below an overview is given of all the quotations provided so far.
Thermacore *1
Technical
feasibility
€ 4,500.00
Detailed
design
(Thermal
management only)
-
(Thermal
management only)
(Thermal
management only)
-
-
$ 15,900.00
ACT, Inc. *2
MJM Engineering Co. *3
Philips Innovation Services
Fokker Services B.V.
Production
(unit price)
€ 670.00
$ 2,500.00
(Thermal
management only)
-
$ 3,750.00
(Thermal
management only)
-
-
*1
See Appendix F
See Appendix G
*3
See Appendix H
*2
5.1.2 Total design costs DOA holder
Within KLM Engineering & Maintenance, the DOA engineers have estimated around
800 hours of total time needed in order to finish all DOA proceedings, including
certification and testing. KLM DOA engineering costs are € 78.00 per hour. Total
DOA engineering costs will therefore sum up to:
Engineering costs = 800 hrs ⋅ € 78.00 = € 62,400.00
5.2
Production costs
The production and assembly costs of the different parts have also been assessed. It
is preferable to have the parts and complete assembly fully produced and assembled
at a production organization with a Production Organization Approval (POA), which
has the approval to build and certify aircraft parts when a DOA-POA agreement is in
place (EASA Part-21 Subpart G). As such, involvement of a third organization and all
the all additional costs such an involvement entails are omitted.
5.2.1 Production Organization Approval
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Unfortunately there are only very few companies in The Netherlands that hold POAs
of which the Scopes of Work cover external aircraft lighting. These organizations
have been filtered from the total of EASA’s POA holders list of The Netherlands:
 AIS-International B.V.  Their POA’s Scope of Work does not cover
external aircraft lighting, yet they are prepared to extend this Scope of Work
in coordination with KLM DOA.
 Fokker Services B.V.  The Scope of Work of their POA covers external
aircraft lighting.
 Van Den Berg’s Technische Bedrijven B.V.  The Scope of Work of their
POA covers external aircraft lighting as well.
5.2.2 Non-POA: Philips Innovation Services
Although it is preferred to have the production at a POA holder, the abovementioned
organizations can not produce the LED lamp from A to Z, i.e. the production process
will contain outsourcing. As such it might be more efficient to have the product
produced by a company which is not POA approved, yet can have the product
produced without any outsourcing. Such an organization in The Netherlands is
Philips Innovation Services. Together with Philips Lumileds, the Innovation Services
are able to provide assistance for:
 Concept creation
 Product and process development
 Equipment development
 Prototyping and small series production
 Industrialization
 Quality and reliability
 Sustainability, safety and health
 Industry consulting
Furthermore, the centre’s competences cover:
 Micro and nano technologies
 Mechatronics and electronics manufacturing
 Mechatronics and high precision engineering
 Industrialization & production technologies
 Quality and reliability test and measurement
 Quality and reliability engineering
 Software products and systems
 Electronic products and systems
Philips Innovation Services covers all necessities in order to produce a LED lamp
solution and as such, the author of this report has visited Philips Innovation Services
in order to discuss the possibilities of producing the LED solution mentioned in the
precious sections. The outcome of the visit was quite positive. Philips Innovation
Services greeted the idea with an optimistic attitude and sees opportunities that
would most likely result into a solution, though paired with quite some challenges to
overcome.
One of the main challenges besides the thermal management is the electrical driver
needed to power the LED packages. The current power supply provides 28 VAC 400
Hz to the lamp and there is currently no off-the-shelf solution which could provide the
needed output of 120-130 Watt with constant current. Such a solution needs to be
custom engineered, which – according to the contact person at Philips Innovation
Services – could extend to a year of development. This problem could be
circumvented by branching out a 28 VDC power cable to the landing light
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assemblies, since it is easier to develop a driver that works with a DC power input. In
that case the transformer of the lights can to be removed. However this requires a
change to the aircraft, which excludes this solution from being a drop-in one.
On the 2nd of May 2013, Ir. Joris Vrehen of the Optics Research department of Philips
Lighting provided the author with a technical feasibility study of a retrofit LED PAR 64
lamp. This study is discussed in more detail in section 6.1.3 (Technical risks).
5.3
Certification costs
The product certification costs consist of:
 DO-160G Environmental Conditions and Test Procedures for Airborne
Equipment
 EASA Supplemental Type Certificate (STC)
5.3.1 DO-160G testing
Since the LED landing light lamp is an electrical equipment installed outside the
pressure cabin, it should submit and pass the DO-160G Environmental Conditions
and Test Procedures for Airborne Equipment. These test procedures can be
performed at a few select laboratories in The Netherlands. The Nationaal Lucht- en
Ruimtevaartlaboratorium / National Aerospace Laboratory (NLR) can facilitate most
of the testing procedures at one location. Two of DO-160G’s 23 test section need to
be outsourced to other laboratories in Great-Britain and Germany, but NLR is willing
to arrange these outsourcings as well. This way all the testing is organized and
facilitated by one organization.
NLR was requested to provide two quotations: one of a complete DO-160G testing
with all its sections and one with only the sections which the author of this report
regarded as indispensable to be tested, thus omitting the sections that show a
similarity in performance compared to the current incandescent lamp.
The quotations can be found in Appendix I and are offered at:
 Full set of DO-160G environmental tests:
€ 66,100.00
 Limited set of DO-160G environmental tests:
€ 37,300.00
Furthermore KLM Engineering & Maintenance requested the quotations to be
modular per section, which means that they include the price per section test
procedure. This would enable KLM DOA engineers to recalculate/estimate the
quotation price in case a redesign of the LED lamp occurs which might affect the
similarity assumptions.
5.3.2 EASA Supplemental Type Certificate (STC)
The new LED lamp is considered an alteration to the aircraft's certified built-in
equipment, initiated by KLM DOA, which is a party other than the type certificate
holder. As such, this alteration needs an approved supplementary ("supplemental" in
FAA terminology) type certificate, or STC. Consultation with Hein Lindhout (Master
Engineer (senior) IFE) [29] resulted in an estimation of the associated costs
amounting to € 10,000.00.
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5.4
Product/unit costs
Waiting for POA results, but for now estimated to be € 1,500.00, based on the
already sold PAR46 price which is at most € 1,200.00.
5.5
Return On Investment (ROI)
In order to reflect on the cost-benefit analysis it is of the essence to know the ROI.
The ROI is a performance measure which evaluates the efficiency of an investment.
In the scope of this research, the ROI should be obtained as an amount of time (e.g.
years) it takes to breakeven the invested costs. There are two ways to calculate the
ROI for this research. The regular approach would be simply to divide the total
developing/invested costs (per aircraft) by the total yearly expenses (per aircraft):
ROIregular approach =
Total developmen t costs
Total expenses per year
However, since in this case there is a change from a consumable product
(incandescent lamp) to a lifetime product (LED lamp), it is more appropriate to
depreciate the total development costs over the amount of years in service of the
aircraft that are needed in order to start making profit from the new investment and
comparing that with the total expenses per year multiplied by this same amount of
years in service. By doing so, the breakeven point of both the development costs and
expenses can be found.
The breakeven point is done by dividing the total development costs by the amount
of years in service needed (as a variable) and equating that with the total expenses
during the same period (i.e. ‘Total expenses per year’ multiplied by ‘Years in
service’). This provides the following relation regarding the breakeven point, which
resembles the ROI expressed in years of aircraft service over which the development
costs of the new lifetime product should be depreciated in order to start making profit
out of the invested money for developing this product:
(Total developmen t costs)
= (Years in service) ⋅ (Total expenses per year)
(Years in service)
Solving this relation for the ROI expression ‘(Years in service)’ as follows, gives the
breakeven point, which is the ROI in years of service:
(Total developmen t costs)
= (Years in service) ⋅ (Total expenses per year)
(Years in service)
(Years in service) =
(Total developmen t costs)
= ROIregular approach
(Total expenses per year)
5.5.1 Total expenses per year
The total expenses per year are mainly from two aspects:
 The cost of the replaced lamps
 The labor hours for replacing these lamps
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A Q5559 lamp costs €42.63 and one hour of labor costs €134.- per hr. Approximately
1.5 hours of labor is required per lamp change.
An overview of the total lamp changes and labor of the total fleet is given table
Table 5.1: Cost overview of the total lamp changes and labor of the total fleet
5.5.2 Total development costs
The total development costs are eventually broken down into the following aspects:
 LED product/lamp:
 DOA detailed design
 POA production / Unit costs
 Certification:
 EASA STC
 DO-160 testing
 Other:
 A/C modification costs (non drop-in unit)
 Unanticipated costs/risk
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Table 5.2: Cost overview of the LED PAR 64 lamp development
5.5.3 Results of the regular approach
The ‘Total development costs’ for the total fleet amount to € 833,470.00, whereas the
‘Total expenses per year’ for the total fleet amount to € 95,007.32. Using the
According to the regular approach, the ROI should be:
ROI =
Total developmen t costs
Total expenses per year
€ 833,470.00
€ 95,007.32
≈ 8.8 years
=
This ROI is of course too high, compared to the desired ROI of 1 year.
5.5.4 Results of the depreciation approach
This approach looks for a breakeven point between the total development costs and
the total expenses by depreciating the total costs over a certain period and equating
the result to the expenses over the same period. According to section 5.5 the ROI is
obtained by the equation:
(Years in service) =
(Total developmen t costs)
(Total expenses per year)
= ROIregular approach
=
€ 833,470.00
€ 95,007.32
≈ 3.0 years
The development costs at this breakeven point is equal to the expenses and can be
calculated by inserting the calculated breakeven value of the ‘(Years in service)’ in
either the equation for the expenses of the development costs:
LED Landing Light │ Design, Certification & Production
Page 66
(Total developmen t costs)
= (Years in service) ⋅ (Total expenses per year)
(Years in service)
€ 833,470.00
€ 833,470.00
€ 95,007.32
=
€ 833,470.00
⋅ € 95,007.32 = € 281,399.63
€ 95,007.32
The graphical demonstration of the depreciation procedure is shown in figure 5.1.
This figure represents a graph that visualizes the total expenses arising during the
years of aircraft service (orange line) and the development costs depreciated during
the same period of aircraft service.
As calculated above, the breakeven point is positioned at the 3 years (x-axis) and
€281,399.62 (y-axis). After the breakeven point of 3 years aircraft service, the project
becomes profitable.
∆ Costs
Figure 5.1: Expenses vs. Development costs of the total fleet
Breakeven point
Years in service ≈ 3
Expenses = development costs = € 281,399.62
This profit increases yearly. The rate of profit increase per year in service is found to
be:
LED Landing Light │ Design, Certification & Production
Page 67
(Total developmen t costs)
(Years in service)
(
Total developmen t costs )
d(∆Costs )
= (Total expenses per year ) +
d(Years in service )
(Years in service)2
∆Costs = (Years in service ) ⋅ (Total expenses per year ) −
= € 95,007.32 +
€ 833,470.00
(Years in service)2
Both functions are shown in figure 5.2 in the same graph of figure 5.1. It can be seen
that for increasing ‘(Years in service)’ these functions eventually approach their
asymptotes, which are (for ‘(Years of service)’ ≥ 15):
∆Costs = (Years in service ) ⋅ (Total expenses per year ) = (Years in service ) ⋅ € 95,007.32
d(∆Costs)
= (Total expenses per year ) = € 95,007.32
d(Years in service )
Figure 5.2: Profit rate per year in service
As can be seen in the graph of figure 5.2, eventually the profit (∆ costs) will equal the
yearly expense rate of € 95,007.32 per year.
LED Landing Light │ Design, Certification & Production
Page 68
6
Risk Analysis - Evaluating and Managing Risks
A Risk Analysis helps to identify and manage potential problems that could
undermine key business initiatives or projects. Risk is made up of two things: the
probability of something going wrong, and the negative consequences that will
happen if it does.
A Risk Analysis is carried out by first identifying the possible threats that this project
can face, and by then estimating the likelihood that these threats will happen. One
good way of presenting these risks and their impact on the project’s prospects is the
so-called ‘Failure Mode Effects Analysis (FMEA)’, which is discussed in section 6.2.
6.1
Identifying risks/threats
The first step in Risk Analysis is to identify the existing and possible threats that the
project for the realization of an LED landing light lamp might face. These can come
from the following sources:
 Certification
 Financial
 Operational
 Technical
 Procedural
Next sections will identify these threats by breaking them down.
6.1.1 Certification risks
During certification several risks may occur. These risks are listed below and
assessed according to their exposure level to the project.
DO-160G tests
The possibility that the new LED PAR 64 lamp fails the DO-160G tests is expected to
be low. The argumentation for this assessment is based on the fact that a quite
similar lamp – the LED PAR 46 – already passed the DO-160G tests. However, since
the LED PAR 64 lamp will be equipped with a different driver, the DO-160G sections
that might be excluded from similarity between both lamps are mainly those involving
electrical and Electromagnetic Interference (EMI) facets:
 Section 16.0 - Power Input
 Section 17.0 - Voltage Spike
 Section 18.0 - Audio Frequency Conducted Susceptibility - Power Inputs
 Section 19.0 - Induced Signal Susceptibility
 Section 20.0 - Radio Frequency Susceptibility (Radiated and Conducted)
 Section 21.0 - Emission of Radio Frequency Energy
 Section 25.0 - Electrostatic Discharge
It is nevertheless not expected that the new LED PAR 64 lamp would fail any of
those test.
Modification classification
A PAR 64 LED drop-in solution, which passes the DO-160G tests and designed
according to the SAE Aerospace guidelines for landing lights of large multiengine
LED Landing Light │ Design, Certification & Production
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turbojet aircraft (see section 4.1.5), will not be considered a change and can be used
as a qualified alternative part for Q5559.
If the solution, however, requires an aircraft change, i.e. it is not a drop-in one; this
modification would need to be classified Minor or Major. The extent of aircraft change
depends on the technical limitations (see Section X.X) to keep the new LED lamp as
close to a drop-in solution as possible.
The current design is not a drop-in solution and it is expected to be classified as a
Minor modification, according to KLM’s Head of Airworthiness Office, Maurice
Laarakker [28]. However, in the case it gets classified as a Major, it would require
additional effort and lead-time for the certification process. EASA (CAA-NL) will
closely monitor and participate in KLM DOA’s second Major EASA STC which will
have impact on project lead-time.
Dependence on third parties
The level of dependence on third parties can pose a (considerable) risk to the
realization of a LED landing light solution. This risk can be caused by:
 The assigned person from EASA: the level of collaboration with EASA is
depended on the willingness of the EASA representative to help realizing the
new design.
 Level of innovation in the new design: a design which involves a high level of
novelty will need extra testing at locations that might not be readily available
nearby KLM DOA’s location and it adds extra workload and costs.
 KLM E&M is a DOA holder, which means that they are only allowed to design
airworthy products, but not allowed to engage in the production of such
products. Only a POA holder has the approval to build and certify aircraft
parts when a DOA-POA agreement is in place.
 The production might need to be (partly) outsourced to one or several third
parties, which induces extra communication channels between these parties
and the POA-DOA. It will also most probably induce extra costs.
 Parts of the certification documents are needed from EASA approved test
stations. This will cause delay to the certification process. Fortunately all
required DO-160G tests can be executed at or arranged by the test facilities
of the Nationaal Lucht- en Ruimtevaartlaboratorium (NLR). KLM DOA has
received a price offer for these tests.
 KLM DOA does not have sufficient experience and expertise to independently
complete the detailed design. This is further discussed in the section below:
“DOA capabilities”.
DOA capabilities
Within KLM DOA there are several risk factors which need to be taken into account
during the (detailed) design phase of this project.
 According to Senior Master Engineer H.J. Lindhout [29], the earliest
opportunity for KLM DOA to start this project would be around
August/September 2013. This would mean that there is a delay of five to six
months in order to start with the detailed design and further deployment of the
project.
The advantage that a delay could hold is a further maturing technological
foundation. LED technology is yet to improve much further and is currently
still not matured in terms of e.g. efficiency/efficacy and luminous flux (light
out). Similar trends of development have been observed in the maturity
process of other light sources.
 There is capability for assigning only one DOA engineer to work on / lead this
project. This minimum assignment could jeopardize meeting the targeted
deadline for this project.
LED Landing Light │ Design, Certification & Production
Page 70

KLM DOA does not have sufficient experience and expertise to independently
complete the detailed design. Part of the design will have to be outsourced to
another DOA organization.
6.1.2 Financial risks
Financial risks are probably the most important risk factors. As such, a thorough
analysis of these risks is an absolute necessity.
Break-even point (BEP) of one year
The break-even point (BEP) is the point at which cost or expenses and revenue are
equal. For this project this point is set for a period of one year. This period is a strong
requirement and an extension of it may very well be a deal-breaker, provided an
appropriate substantiation could be given to press on for extended time. Several
aspects can cause an extension of this period, such as:
 High engineering cost.
 High production/assembly cost.
 High certification cost.
 High implementation cost.
 High maintenance/operating cost
Every aspect is discussed in detail below.
Engineering cost
The cost of engineering a feasible PAR 64 LED drop-in solution could be higher than
expected. According to Senior Maintenance Engineer H.J. Lindhout [29], the
estimated minimum of labor hours required within KLM DOA for this project may well
be 800 hours, give or take 20%. A labor hour of an engineer within KLM DOA is
priced at €84,-. In total the minimal engineering costs will be around
Engineering cost = 2 = 800 hrs × € 78.00 = € 62,400.00
Spreading these costs over the production, which amounts to 108 × 4 = 184 units,
the total engineering cost per unit would be:
Engineering cost per unit =
800 hrs × € 78.00
= € 144.44 ≈ €145.00
108 × 4
The more complex the design, the more engineering hours should be accounted for.
The abovementioned estimated engineering cost is already alarming high and could
only get higher, considering the fact that KLM DOA will not be able to deliver a
complete detailed design. Some of the design tasks will require outsourcing to an
additional DOA holder. Cost-wise it is highly recommended that this DOA holder is
also the POA holder that eventually will produce the product. Such an arrangement
could result in spreading out the outsourced engineering cost over the production,
and make it part of the production cost, which results in a more expensive product,
but less initial/start-up costs.
Production/assembly cost
The cost of producing the final design is the most uncertain financial factor, and as
such is generally considered one of the highest risk factors. The production costs
depend on several parameters, such as:
 Complexity of the design
LED Landing Light │ Design, Certification & Production
Page 71





Material cost
Labor cost of the POA holder
Amount of units to be produced
Prospect for a long-term collaborative with production organization
Profit margin of the POA holder
KLM DOA has influence on the design complexity by reducing the amount of needed
parts as much as possible. The design complexity should be kept to a minimum,
without jeopardizing the targeted performance characteristics. This is a fine balance
that should always be iterated throughout the design process. A minimum complexity
of the design ensures lower production costs.
It is self-evident that the higher the amount of to be produced units, the lower the
price per unit will be, i.e., mass production result in lower production costs, which
results in lower unit cost. Depending on what the final product would be, the amount
of units could vary. In case of a full fledged drop-in solution, practically the complete
KLM fleet could and would be equipped with this new LED landing light lamp. This
would mean a production quantity of 108 × 4 = 432 ≈ 450 units. If the design is not or
only partly a drop-in one, i.e. some kind of aircraft modification would be needed,
then the production quantity would be restricted to the aircraft type that makes up the
major part of the fleet: the Boeing 737-NG. The problem with this type however, is
that it is equipped with two types of landing lights: a fixed and a retractable one. This
forms a technical risk, which will be discussed in the next section (6.1.3).
Having some kind of a prospect for a long-term collaborative with the production
organization could influence the unit price. In order to create this prospect, KLM
could for instance explore opportunities to extend the implementation of the new LED
lamp to more types on the fleet and other companies and partners associated to
KLM. Also any maintenance items supplies to the operator (KLM) could be a part of
the long-term collaborative.
6.1.3 Technical risks
The main technical risks concern:
 Infeasible drop-in solution
 Due to insufficient heat sinking
 Due to large electrical driver
 Required aircraft modifications
Infeasible drop-in solution
A feasible drop-in solution is mainly threatened by the necessity to install a large heat
sink and/or electrical driver, which will not fit into the limited space of the PAR 64
lamp. These threats/risks are considerable since the amount of heat that needs to be
dissipated and the required electrical capacity are substantial, whereas the available
“drop-in” lamp space is quite limited.
Ir. Joris Vrehen of the Optics Research department of Philip Lighting conducted a
technical feasibility study addressing only the optic and thermal limitations. Other
very important items like electronics, protection from moisture, de-icing, pressure
variations etc., where not included. This complete study can be viewed in Appendix
J. The conclusion of this study is stated as:
“Based on the optical and thermal estimation there are two major roadblocks
ahead. First of all, the limited brightness of today’s LED’s require a large area
of collimator lenses that is significantly (factor 2.8) bigger than the available
LED Landing Light │ Design, Certification & Production
Page 72
space. It is very doubtful whether an improved lens design can bridge this
gap.
The other roadblock is the thermal limitation. In order to obtain a long lifetime,
and given the thermal power that’s needed to be dissipated; we will be very
limited in the acceptable ambient lamp temperatures. Calculations where
based on a slightly too big heat sink having free convection on all sides. It
should be noted that the electronics that need to be integrated will also take a
significant part of the heat sink further reducing the cooling capacity.
So far I have to conclude that we cannot fit the required performance in the
available space with current available technology. An innovation step is
needed to meet these challenging requirements.”
Required aircraft modifications
Aircraft modifications are required in case the LED lamp is not fully drop-in, or only
semi-drop-in. Semi-drop-in lamps are of PAR 64 format and dimensions, but require
different electrical input than currently is delivered to the incandescent lamp, namely
DC instead of AC.
6.1.4 Procedural risks
The main procedural risks are because of:
 Insufficient expertise by KLM DOA engineers
 Insufficient DOA-organization capability
 POA/DOA non-performance
Insufficient expertise by KLM DOA engineers
Since KLM DOA engineers are not experienced in LED lamp design, there is
insufficient expertise in order to complete a well-designed detailed design. Extra
procedural steps are required in order to make up for this lack of expertise, such as
outsourcing, which will induce more costs and most probably also procedural delay.
Insufficient DOA-organization capability
Furthermore, it is also probable that the KLM DOA capability in terms of
manpower/personnel might not be sufficient to complete the detailed design and
certification within the project’s outlined period of one year. This might cause a delay
or even stalemate of the project, which will only induce extra costs. Insufficient
capability of DOA engineers might also jeopardize the progress of other projects.
POA - DOA (-Subcontractor) non-performance
With the involvement of more than one party it is viable that not only the design but
also and especially the production progress gets delayed and faltered. This could be
mainly due to insufficient collaboration, inefficient communication and unclear
responsibilities or contractual agreements.
6.2
Failure Modes and Effects Analysis (FMEA)
Failure Modes and Effects Analysis (FMEA) is a systematic, proactive method for
evaluating a process to identify where and how it might fail and to assess the relative
impact of different failures, in order to identify the parts of the process that are most
in need of change. FMEA includes review of the following:
LED Landing Light │ Design, Certification & Production
Page 73




Steps in the process
Failure modes (What could go wrong?)
Failure causes (Why would the failure happen?)
Failure effects (What would be the consequences of each failure?)
FMEA is used to evaluate processes for possible failures and to prevent them by
correcting the processes proactively rather than reacting to adverse events after
failures have occurred. This emphasis on prevention may reduce risk of harm to both
patients and staff. FMEA is particularly useful in evaluating a new process prior to
implementation and in assessing the impact of a proposed change to an existing
process [30].
For each step in FMEA, the Failure effects, Failure causes and Current Process
Control (i.e. Prevention Control/Detection) are evaluated with values between 1 and
10. The Failure effects and Failure causes are evaluated according to their severity
and probability of occurrence respectively, the higher the value they get (10 is the
maximum value) the more severe the effect or the more probable the occurrence of
the cause. The Current Process (Prevention) Control is valued reversely, i.e. the
better the detection of a failure cause, the lower the value it is given (with 1 the
minimum value). Eventually all three value per process step are multiplied, yielding a
value between 1 and 1000, which is called the Risk Priority Number (RPN). This RPN
should be as low as possible in order to minimize risk. Acceptable RPN values for
most process steps are ≤100.
In addition, the FMEA also includes Recommended Actions per process step. Per
Recommended Action the Responsible Person & Target Date and Taken Action
are usually also stated. Consequently, the Severity, Probability of Occurrence and
Detection are re-evaluated, taking into account the Recommended and Taken
Actions.
An overview of the FMEA analyses with the most important process steps for this
project can be viewed in table 6.1:
Process
Function
(Step)
Production
Potential
Failure
Modes
(process
defects)
POA nonperformance
Potential
Effect(s)
of Failure
S
E
V
Potential
Cause(s)
of Failure
O
C
C
Multiple
involved
parties.
Longer
development
time.
Extra costs.
Extra effort.
5
Unclear
responsibilitie
s/contractual
agreements
Third parties
are located at
far locations.
LED Landing Light │ Design, Certification & Production
D
E
T
R
P
N
5
125
Finding POA
holders that
can absorp
maximum
POA work
scope.
Insufficient
co-operation /
willingness.
Inefficient
communicatio
n.
Current
Process
Controls
5
Checking
how eager
POA (and
subcontractor
s) are to
engage into a
co-operation.
Page 74
More costs.
Design
Major change
classification.
Production
Insufficient
units to be
produced.
Engineering
High
engineering
cost
Production
High
production
cost.
More effort.
Longer
development
time.
No drop-in
solution.
8
High unit
price.
Negative
cost-benefit
analyses.
Negative
cost-benefit
analyses.
9
Restricted
amount of
A/C in KLM
fleet.
9
Many hours
needed in
order to finish
a (detailed)
design.
Expensive
unit price.
Negative
cost-benefit
analyses.
Extensive
A/C
modification.
9
Expensive
labor cost.
Expensive
material cost.
10
Performing a
technical
feasibility
study.
3
240
6
Several
project
scopes could
be adopted.
But it is not
yet clear
which one is
most suitable.
5
270
7
Check
needed time
with DOA
engineers.
5
315
5
360
10
Performing a
technical
feasibility
study.
5
400
4
Capability
check with
DOA
engineers
within KLM
E&M.
3
84
3
90
1
100
8
ROM check
at production
organizations.
Large heat
sinking
required.
Study
Drop-in
solution
technically
not feasible
A/C
modification
needed
8
Large area of
collimator
lenses
required.
Poor detailed
design.
Design
Slow project
development.
Certification
process
delayed.
7
Jeopardizing
progress of
other
projects.
Design
Design
LED lamp not
passing one
or more DO160 sections
during
testing.
LED lamp is
not certifiable.
Detailed
design not
correct.
Detailed
design is not
meeting
requirements.
Large driver
required.
10
Unsufficient
DOA
capabilities
Design error
Production /
prototyping
error.
Detailed
design.
3
Test (setup)
error.
10
DOA holder
has
unsufficient
expertice in
LED lamp
design.
Consulting
POA and
other LED
production
organizations.
10
Reduction of
nr. of test
through
similarity
analyses.
Consulting
DOA
engineers at
KLM E&M.
Table 6.1: FMEA analysis of the design, certification and production process
LED Landing Light │ Design, Certification & Production
Page 75
From this FMEA analysis it could be concluded that there are several risks to be
taken care of in the study, design, engineering and production steps of the process.
These are risks can be minimized with the following recommended actions:
 Study:
 Involving more experienced parties for the technical feasibility study
 Design:
 High-quality detailed design
 Quality control during prototype production
 Redundant testing
 Find experienced designers
 Decide on Make/Buy/Collaborate
 Reduce complexity of the design as much as possible
 Production:
 Avoid needing subcontractors as much as possible
 POA for both production and testing
 Involving KLM Purchasing
 Tight project management
 Explore involvement of other airlines.
 Find economy of scale: develop 'less' expensive options as well, e.g.
PAR46 and PAR36.
 Reduce complexity of the design as much as possible
LED Landing Light │ Design, Certification & Production
Page 76
7
Conclusion and Recommendations
LED technology has several key strengths over traditional incandescent lighting.
These are mainly: its solid state which makes it more durable and shock resistant; a
higher efficiency ensures reduced power consumption; a much longer operating
lifetime; slow failure mode; operational in extremely cold or hot temperatures; instant
lighting and frequent switching.
Several LED lamps have already been developed for aviation, such as anti-collision
lights, navigation/position lights and taxi & turn lights. Yet PAR 64 LED landing light
lamps still remain undeveloped. This is due to the fact that LED technical feasible
solutions for these high-brightness lamps are quite a challenge. Besides this
technical feasibility, also the financial feasibility is a challenge.
Replacing the incandescent landing light lamps with LED lamps requires several
important aspects to be taken into account. For smooth certification and
implementation it is almost necessary to develop an LED lamp that is a drop-in
version of its incandescent predecessor, which means that the new lamp should be
of the same shape and run on the same electrical supply. This ensures that the lamp
could be placed at all landing light positions (fixed, retractable and nose gear
positions), plus no landing light assembly of aircraft modifications are required.
Next to this drop-in requirement, the main design/technical challenges consist of the
development of a capable electrical driver to supply enough electrical power and a
thermal management system that is able to dissipate a considerable amount of heat
created by the LED chips/packages of the lamp. Also the optical aspect is important,
since the right beam spreading pattern should be produced during operation. The
light intensity/output and color rendering index should also be taken good care of
during the (detailed) design.
Design requirement and guidance is found in the Certification Specifications for
Large Aircraft (CS-25): ‘CS 25.773(a) - Pilot compartment view’ and ‘CS 25.1383(a),
(b), (c) - Landing Lights’. More detailed guidance material however, is given in two
documents of the Society of Automotive Engineers Aerospace (SAE Aerospace).
These are ‘SAE ARP693 REV. D - Landing and Taxiing Lights - Design Criteria for
Installation’ and ‘SAE ARP6402 REV. A - LED Landing, Taxiing, Runway Turnoff,
and Recognition Lights’. Further information could be found in the ‘Minimum
Equipment List (Part M)’.
The cost-benefit analysis could be executed in two different ways. The regular
approach gives a Return On Investment (ROI) after approximately 8.8 years.
However, since the LED lamp should be considered as a lifetime product and hence
an investment instead of a consumable, it is customary to depreciate this product
over the years in service. This renders a shorter ROI of approximately 3 years.
Several risks during the development process could be identified. These risks are
mainly found in the study, design/engineering and production stages. The most
prominent are: technical infeasibility of a drop-in solution, high
production/engineering costs, insufficient units to be produced, a major change
(STC) classification, insufficient performance of POA and a slow project
development. A technical feasibility study by Philips Lighting, which addressed the
optical and thermal limitations, rendered a negative result concerning the technical
feasibility of a retrofit/drop-in solution. It was concluded that the required performance
criteria cannot be fitted in the available space with current available technology. An
innovation step is needed to meet these challenging requirements
In light of the abovementioned conclusion, the author of this report recommends the
following in order to successfully fulfill the realization of the outlined project:
 Aiming for a drop-in solution by innovating.
LED Landing Light │ Design, Certification & Production
Page 77






More research should be done to reduce the area of the collimator lenses in
order to sufficiently narrow the light beam.
Performing extensive studies on the electrical driver, since that is one of the
main challenges to overcome in order to realize a drop-in solution.
More detailed heat-management analysis should be done in order to establish
the exact heat sink area needed for free convection. It is expected that this
area will be so large, that a retrofit drop-in LED lamp will not be possible.
Find economy of scale: develop 'less' expensive options as well, e.g. PAR 46
and PAR 36, in order to increase the unit production and decrease the price
per unit. These lamp types have the same shape as the PAR 64, but are
smaller.
Explore involvement of other airlines in order to increase unit production and
interested (more experienced) partners in order to increase competence,
know-how and product quality.
Decide on whether to make the lamp, buy it or collaborate in its production
(as a launching customer).
LED Landing Light │ Design, Certification & Production
Page 78
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Cree, Inc., Thermal Management of Cree® XLamp® LEDs,
http://www.cree.com/~/media/Files/Cree/LED%20Components%20and%20M
odules/XLamp/XLamp%20Application%20Notes/XLampThermalManagement
.pdf
[21]
Landing and Taxiing Light - Design Criteria for Installation, SAE-ARP-693
Rev. D, issued 1961-06, revised 2012-03, SAE Aerospace
[22]
Certification Specifications for Large Aeroplanes CS-25, European Aviation
Safety Agency, ED decision no. 2003/2/RM.
[23]
Light Emitting Diode Lighting Module with Improved Heat Dissipation
Structure, Inventors: Shu Jung Yang, Tainan County (TW); Ra Min Tain,
Taipei County (TW).
[24]
Frank Marcott, Boeing 737 representative, frank.marcott@transavia.com /
frank.a.marcott@boeing.com, Tel: +31 (0)20 648-4639 / +31 (0)65 256-0268
[25]
SAE ARP693 Rev. D, Landing and Taxiing Lights - Design Criteria for
Installation, SAE Aerospace, Issued 1961-06, Reaffirmed 2006-06, Revised
2012-03, Superseding ARP693C
[26]
SAE ARP6402 Rev. A, LED Landing, Taxiing, Runway Turnoff, and
Recognition Lights, SAE Aerospace, Issued 2011-06, Revised 201-11,
Superseding ARP6402
[27]
Boeing 737 Minimum Equipment List (MEL), Revision Number: 21, Revision
Date: Dec 13, 2012
[28]
Laarakker, M.J.H.J., Head of Airworthiness Office, KLM Engineering &
Maintenance, Department SPL/WM, Hangar 14, Office 32204, 1117 ZL
Schiphol-Airport, The Netherlands, +31 (0)20 6493704,
MJHJ.Laarakker@klm.com
[29]
Lindhout, H.J., Master Engineer (senior) IFE, KLM Engineering &
Maintenance, Department SPL/WM, Hangar 14, Office 32158, 1117 ZL
Schiphol-Airport, The Netherlands, +31 (0)20 6482302,
HJ.Lindhout@klm.com
[30]
http://www.ihi.org/knowledge/Pages/Tools/FailureModesandEffectsAnalysisT
ool.aspx, Institute for Healthcare Improvement, Last Modified: 11/01/2011
[31]
Environmental Conditions and Test Procedures for Airborne Equipment,
RTCA DO-160G, Supersedes DO-160F, RTCA, Incorporated, 1828 L Street,
NW, Suite 805, Washington, DC 20036, USA
LED Landing Light │ Design, Certification & Production
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Appendix A: The Retractable Landing Light Assembly
Photographic images of the retractable part from the retractable landing light
assembly of the Boeing 737-NG. These photos are taken from the maintenance
department of KLM.
Figure A.4: Front view of the retractable part
Figure A.2: Side view of the retractable part
LED Landing Light │ Design, Certification & Production
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Figure A.3: Back view of the retractable part
Figure A.4: Lamp lens of the retractable part
LED Landing Light │ Design, Certification & Production
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Appendix B: Daily Average Number of Landings B737
The daily average number of landings (i.e. number of flights) for each registration
number in the KLM and Transavia Boeing 737 fleet.
Registration
Operator
Factory
Del. date
# Landings
01-01-12
# Landings
01-01-13
# Landings
2012
# Landings
daily avg.
PH-BGD
PH-BGE
PH-BGF
PH-BGG
PH-BGH
PH-BGI
PH-BGK
PH-BGL
PH-BGM
PH-BGN
PH-BGO
PH-BGP
PH-BGQ
PH-BGR
PH-BGT
PH-BGU
PH-BGW
PH-BGX
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
25-08-08
29-08-08
15-12-08
18-03-09
16-12-09
16-02-10
11-06-10
23-09-10
26-04-11
28-03-11
31-03-11
09-05-11
22-06-11
25-08-11
06-09-11
28-09-11
11-10-11
24-10-11
5981
6172
5685
5175
3724
3521
2976
2414
1375
1540
1502
1281
1048
657
632
497
408
342
7919
8102
7609
7096
5740
5477
5034
4497
3440
3598
3574
3332
3100
2827
2705
2545
2502
2429
1938
1930
1924
1921
2016
1956
2058
2083
2065
2058
2072
2051
2052
2170
2073
2048
2094
2087
5.30
5.27
5.26
5.25
5.51
5.34
5.62
5.69
5.64
5.62
5.66
5.60
5.61
5.93
5.66
5.60
5.72
5.70
PH-BXA
PH-BXB
PH-BXC
PH-BXD
PH-BXE
PH-BXF
PH-BXG
PH-BXH
PH-BXI
PH-BXK
PH-BXL
PH-BXM
PH-BXN
PH-BXU
PH-BXV
PH-BXW
PH-BXY
PH-BXZ
PH-BGA
PH-BGB
PH-BGC
PH-BCA
PH-BCB
PH-BCD
PH-BCE
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
KLM
25-02-99
10-05-99
30-06-99
30-08-99
18-05-00
15-06-00
22-07-00
15-08-00
29-08-00
12-09-00
26-09-00
27-11-00
16-12-00
12-05-06
16-03-07
20-12-07
06-02-08
05-03-08
09-04-08
06-05-08
28-05-08
20-12-10
26-05-11
??-05-13
??-04-14
20617
20205
19858
19330
18459
18471
18237
17958
18263
17990
17753
17309
17608
9519
7898
6712
6656
6607
6408
6243
6148
1806
1038
0
0
22260
21864
21380
20992
20241
20263
19871
19599
19967
19723
19352
18957
19294
11177
9590
8386
8392
8305
8237
8027
7928
3595
2846
0
0
1643
1659
1522
1662
1782
1792
1634
1641
1704
1733
1599
1648
1686
1658
1692
1674
1736
1698
1829
1784
1780
1789
1808
0
0
4.49
4.53
4.16
4.54
4.87
4.90
4.46
4.48
4.66
4.73
4.37
4.50
4.61
4.53
4.62
4.57
4.74
4.64
5.00
4.87
4.86
4.89
4.94
0.00
0.00
LED Landing Light │ Design, Certification & Production
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PH-BXO
PH-BXP
PH-BXR
PH-BXS
PH-BXT
KLM
KLM
KLM
KLM
KLM
29-06-01
24-08-01
03-10-01
27-10-01
12-05-04
16149
17725
1576
16163
17826
1663
15649
17318
1669
16030
17762
1732
12197
13830
1633
Average daily flights per B737 KLM:
PH-HSB
PH-HSC
PH-HSD
PH-HSE
PH-HSF *1
PH-HSG *1
PH-HSW
TRA
TRA
TRA
TRA
TRA
TRA
TRA
21-04-10
04-05-10
29-04-11
19-05-11
17-04-12
01-05-12
27-04-09
2532
2502
1073
935
2
2
3975
3928
3956
2582
2467
1165
1123
5245
1396
1454
1509
1532
1163
1121
1270
3.82
3.98
4.13
4.20
4.53
4.36
3.48
PH-HZD
PH-HZE
PH-HZF
PH-HZG
PH-HZI
PH-HZJ
PH-HZK
PH-HZL
PH-HZM *2
PH-HZN
PH-HZO
TRA
TRA
TRA
TRA
TRA
TRA
TRA
TRA
TRA
TRA
TRA
22-04-99
24-05-99
11-06-99
25-03-00
25-04-00
10-05-00
16-05-00
06-04-01
26-04-01
01-04-04
23-04-07
17720
17837
18005
17188
16706
17093
16502
15708
15034
10863
6322
18971
19181
19247
18498
17846
18323
17811
16866
15034
12069
7742
1251
1344
1242
1310
1140
1230
1309
1158
0
1206
1420
3.43
3.68
3.40
3.59
3.12
3.37
3.59
3.17
0.00
3.30
3.89
OY-TDA *2
PH-HZX
PH-HZW
OY-TDB
PH-XRA
PH-XRB
OY-TDZ
PH-XRD
PH-XRZ
PH-XRY
PH-XRX
PH-XRW
PH-XRE
PH-XRV
TRA
TRA
TRA
TRA
TRA
TRA
TRA
TRA
TRA
TRA
TRA
TRA
TRA
TRA
20-04-02
25-04-02
09-05-02
19-06-02
22-06-01
01-04-03
06-05-03
16-06-03
18-02-03
12-03-03
31-03-03
25-04-03
20-04-04
29-04-05
0
1328
954
1264
1714
1688
1752
1808
1640
1655
1752
1758
1602
1744
0.00
3.64
2.61
3.46
4.70
4.62
4.80
4.95
4.49
4.53
4.80
4.82
4.39
4.78
3.99
13546
14874
13587
14541
13080
14344
18595
20309
16050
17738
15248
17000
16484
18292
16293
17933
16274
17929
16558
18310
16741
18499
14606
16208
12768
14512
Average daily flights per B737 TRA:
4.31
4.54
4.56
4.73
4.46
4.99
*1 NOTE: These aircrafts were delivered after January 1st, 2012. This had NO impact on the
assessment, given that the average number of landings since deliver date could still be calculated.
2
* NOTE: Discrepancy in/unavailability of the data: NOT TAKEN INTO ACCOUNT AND EXCLUDED
FROM ASSESSMENT!
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Appendix C: Concept Proposal Thermal Management
Solution from Thermacore Europe
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Appendix D: SAE Aerospace – Landing and Taxiing
Lights - Desig Criteria for Installation [SAE-ARP-693]
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Appendix E: SAE Aerospace – LED Landing,Taxiing,
Runway Turnoff, and Recognition Lights [SAE-ARP6402]
Page1/14
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Appendix F: Quotation for a Thermal Analysis from
Thermacore Europe
Page 1/2
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Appendix G: Quotation for a Technical Feasibility
Study from Advanced Cooling Technologies, Inc.
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Appendix H: Quotation for a Thermal Analysis &
Concept Development from MJM Engineering
Page 1/4
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Appendix I: Quotation for DO-160G testing from
Nationaal Lucht- en Ruimtevaartlaboratorium (NLR)
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Appendix J: Technical Feasibility Study PHILIPS
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