FUEL CONSERVATION
EMPRESA BRASILEIRA DE AERONÁUTICA S.A.
REVISION 4 IS A FULL REISSUE OF THIS MANUAL.
GP–145/1536
AUGUST 31, 2001
REVISION 4 – SEPTEMBER 25, 2008
Copyright 2001 by EMBRAER - Empresa Brasileira de Aeronáutica S.A.. All rights reserved. This document shall not
be copied or reproduced, whether in whole or in part, in any form or by any means without the express written
authorization of Embraer. The information, technical data, designs and drawings disclosed in this document are
property information of Embraer or third parties and shall not be used or disclosed to any third party without
permission of Embraer.
GENERAL
PUBLICATION
FUEL CONSERVATION
LIST OF EFFECTIVE PAGES
ORIGINAL ..........0 ....... AUG 31, 2001
REVISION ..........1 ....... OCT 28, 2002
REVISION ..........2 ........SEP 29, 2006
REVISION ..........3 ........ JUN 15, 2007
REVISION .......... 4 ........ SEP 25, 2008
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GENERAL
PUBLICATION
GENERAL
PUBLICATION
FUEL CONSERVATION
FUEL CONSERVATION
TABLE OF CONTENTS
GP-145/1536
SECTION I – GENERAL ...................................................................... 1
INTRODUCTION ............................................................................. 2
FUEL BURN CONTRIBUTION TO OPERATING COSTS......... 2
TYPICAL OPERATIONAL PROFILE ......................................... 3
REDUCTION OF FUEL COSTS ................................................ 4
FUEL CONSERVATION PHILOSOPHY.................................... 5
SECTION II − FLIGHT OPERATIONS AND PERFORMANCE ........... 7
OEW INCREASE AND CONTROL ................................................. 8
FLIGHT PLANNING ...................................................................... 10
REGULATORY RESERVES AND DISPATCH POLICY.......... 10
EXTRA FUEL CONSIDERATIONS.......................................... 11
OPTIMUM CRUISE ALTITUDE ............................................... 13
CRUISE SPEED SELECTION ................................................. 15
FUEL TANKERING .................................................................. 20
IN FLIGHT PROFILE..................................................................... 21
GROUND OPERATIONS......................................................... 21
APU USE ON GROUND .......................................................... 21
AIR CONDITIONING USE ON GROUND................................ 22
SINGLE ENGINE TAXI ............................................................ 23
TAKEOFF ................................................................................. 24
CLIMB....................................................................................... 24
ANALYZING DIFFERENT CLIMB SCHEDULES..................... 25
CLIMB SPEED LOWER THAN 270 KIAS/M0.56..................... 27
CRUISE SPEED MANAGEMENT............................................ 28
LATERAL NAVIGATION OPTIMIZATION ............................... 29
DESCENT ................................................................................ 30
HOLDING ................................................................................. 33
APPROACH AND LANDING.................................................... 33
SUMMARY ............................................................................... 34
REVISION 4
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FUEL CONSERVATION
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SECTION III − MAINTENANCE PRACTICES ....................................37
UTILISATION OF MEL AND CDL .................................................37
MEL – MINIMUM EQUIPMENT LIST .......................................37
CONFIGURATION DEVIATION LIST – CDL ...........................42
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REVISION 4
GP-145/1536
AERODYNAMIC DETERIORATION .............................................42
MISSING PARTS – CDL ..........................................................44
AERODYNAMIC SMOOTHNESS ............................................45
AIRPLANE SYSTEMS...................................................................63
FLIGHT CONTROLS –
RIGGING OF CONTROL SURFACES.....................................63
AIRSPEED INDICATION ACCURACY ....................................64
ENVIRONMENTAL AND PNEUMATICS .................................65
ELECTRICAL POWER .............................................................66
IN-FLIGHT OPERATIONS........................................................67
POWER PLANT........................................................................69
SERVICE BULLETINS ..................................................................72
EFFECTS OF CRUISE SPEED SELECTION ON
DIRECT MAINTENANCE COST ...................................................73
EFFECTS OF SELECTING LOWER CRUISE SPEEDS
ON THE DIRECT MAINTENANCE EXPENSES ......................73
SECTION IV − CONCLUSIONS .........................................................76
GENERAL
PUBLICATION
FUEL CONSERVATION
SECTION I − GENERAL
GP-145/1536
This General Publication presents useful information of fuel
conservation operational and technical aspects and must be used in
conjunction with approved manuals released by EMBRAER. Any
difference between data presented in this document and those
publications, the information contained in the approved manuals must
prevail.
REVISION 4
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FUEL CONSERVATION
GENERAL
PUBLICATION
INTRODUCTION
120
375
350
325
300
275
250
225
200
175
150
125
100
75
50
25
0
110
Crude Oil (US$/Barrel)
100
90
80
70
60
50
40
30
20
10
19
90
19
91
19
92
19
93
19
94
19
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19
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19
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19
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19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
1s 200
tQ 7
20
Ap 08
r2
00
8
0
Jet Fuel (USc/Gallon)
Since 2002 oil prices have experienced a dramatic increase reaching
all-time highs.
Source: Energy Information Administration
Official Energy Statistics from the U.S. Government
Aviation fuel prices have been closely following that trend, which has a
detrimental impact upon an airline’s costs and profitability.
A Fuel Conservation Program is a set of operational and maintenance
procedures that assist an operator in minimizing the fuel required for a
given trip, thereby reducing costs and improving profitability.
With flight safety as its foremost consideration, this publication
discusses the factors affecting fuel consumption that can degrade fuel
efficiency, and provides recommendations to improve fuel usage.
FUEL BURN CONTRIBUTION TO OPERATING COSTS
GP-145/1536
Cash Operating Costs (COC) are those that can be related directly to
the operation of a particular airplane on a particular route. It excludes
ownership costs and cargo/passenger related expenses. For a given
route, it has three main components:
− Fixed Costs: fixed expenses of each leg, i.e. landing,
navigation and airport fees.
− Time Related Costs: all the costs that are a function of flight
time, i.e. maintenance costs, crew costs, etc. ($/hour).
− Fuel Related Costs: cost of fuel burned in a given leg ($/kg or
$/lb).
2
REVISION 4
GENERAL
PUBLICATION
FUEL CONSERVATION
TYPICAL OPERATIONAL PROFILE:
All the costs/savings calculated in this publication consider the
following operational scenario:
Flight Profile:
−
−
−
−
−
−
−
−
Climb Schedule: 270 KIAS/M0.56.
Cruise Schedule: M0.78.
Descent Schedule M0.78/250 KIAS.
Route Conditions: ISA, Calm Wind.
Cruise Altitude: FL 370.
Destination and Departure Airport at Sea Level.
Alternate Airport: 200 NM Distant, Sea Level.
Alternate Cruise Altitude: FL 290.
Fuel savings benefits would be less for hot day (e.g.
ISA+15°C) conditions. For further information, operators
should contact EMBRAER and/or Rolls-Royce.
Operator’s Profile:
− Average Load Factor: 70%.
− 20-airplane fleet.
− Utilization: Six legs per day/Six days per week.
− Average Leg Length: 400 NM (1.15 hours average trip time).
Fuel Costs:
−
Average Fuel
US$ 0.45/lb.
Costs:
US$ 3.00/Gal
=
US$ 0.99/kg
=
− Fuel density 0.803 kg/l (6.7 lb/Gal).
Labor Cost:
Men Hour Cost: US$ 50.00 (used on the definition of
Maintenance Tasks cost and Corrective Action cost).
GP-145/1536
−
REVISION 4
3
FUEL CONSERVATION
GENERAL
PUBLICATION
REDUCTION OF FUEL COSTS
Correct flight operations and line maintenance have significant impact
on trip fuel burn. Flight and maintenance crew technical training
information is used as a guideline for their day-to-day routine.
Investments in this area shall be the first and easiest method to raise
awareness and reduce operational costs, via fuel related expenditures.
Consider the following scenarios for the ERJ135/145 Family. Using
FAA and EASA domestic reserves, the typical performance for a
400 NM trip are:
ERJ135
ERJ145
TYPICAL
OPERATIONAL
FAA
EASA
FAA
EASA
PROFILE
RESERVES RESERVES RESERVES RESERVES
TAKEOFF kg
WEIGHT lb
17309
17250
18970
18908
38159
38029
41821
41685
kg
1206
1204
1260
1258
lb
2659
2654
2778
2773
69
69
70
70
TRIP FUEL
TRIP TIME min
400 NM TRIP
4
ERJ135
ERJ145
1% FUEL SAVINGS
PER LEG
kg
12
13
lb
27
29
ANNUAL SAVINGS
(20 AIRPLANE FLEET)
kg
451000
471000
lb
994000
1040000
REVISION 4
GP-145/1536
For ERJ140 and Legacy, consider the fuel consumption information of
ERJ135 to all cases.
Considering an airline using the ERJ135/145 under those operational
conditions (typical for domestic airlines on US and Europe), 1% fuel
saving represents:
GENERAL
PUBLICATION
FUEL CONSERVATION
Note that apparently small amounts of fuel burn reduction lead to
significant annual savings proportionally to the fleet size. In our
example, a 12 to 13 kg (26 to 29 lb) fuel consumption reduction on
each leg is attainable through adequate operational and maintenance
practices.
1% reduction on Fuel Consumption represents potential
savings from approximately US$ 446,000.00 to US$ 466,000.00
(per year/20 airplane fleet)
FUEL CONSERVATION PHILOSOPHY
This publication intends to demonstrate to customer airlines how an
efficient operation of the ERJ135/145 Family can bring potential fuel
savings in their day-to-day operations. It means that all:
−
−
−
Airplane systems must be operated properly.
Airplane systems must be maintained properly.
Airplane performance and operational resources are explored.
Most of the factors that can degrade fuel consumption will be
discussed, aside providing recommendations that improve fuel
mileage. Flight safety is the primary and basic concept in all the
proposed procedures. The systems/areas that have direct impact on
fuel consumption are:
−
−
−
−
−
−
Flight Operations and Performance.
Aerodynamics.
Flight Controls System.
Environmental and Pneumatic Systems.
Electrical System.
Propulsion System.
GP-145/1536
This publication is directed to all those that are or can be engaged in a
fuel conservation program inside an airline. It is mainly divided in two
chapters, Flight Operations and Performance chapter and
Maintenance Practices chapter.
The Flight Operations and Performance Chapter focuses on the
operational environment and it is recommended to be distributed to
Pilots, Flight Operations Engineers and Dispatchers.
REVISION 4
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FUEL CONSERVATION
GENERAL
PUBLICATION
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REVISION 4
GP-145/1536
The Maintenance Practices chapter focuses on maintenance efforts
that can contribute to fuel savings, through specific recommendations
of maintenance actions, practices, policies and procedures. Therefore,
its distribution is mainly recommended to Maintenance Personnel
(Engineers and Mechanics).
GENERAL
PUBLICATION
SECTION II − FLIGHT
PERFORMANCE
FUEL CONSERVATION
OPERATIONS
AND
Correct airplane operation is a key factor to maximize fuel savings,
operational factors may contribute with more than 1% of fuel savings.
Deviations from the optimum lateral and vertical profiles may lead to
fuel burn and trip time increase, causing impact on COC. Some of the
factors that may determine such deviations are:
−
GP-145/1536
−
−
−
−
Air Traffic Control constraints: speeds and altitudes, radar
vectoring away from planned flight path, etc.
Weather deviations.
Pilot’s flying techniques: use of autopilot, speed variations, etc.
Airline Policy.
MEL/CDL items that require altitude and/or speed restriction.
REVISION 4
7
FUEL CONSERVATION
GENERAL
PUBLICATION
OEW INCREASE AND CONTROL
In average, it is expected a natural increase of an airplane’s Operating
Empty Weight (OEW) in approximately 0.15% to 0.25% for each year
of utilization. This value tends to stabilize after 10 years of utilization at
around 2%, and may be caused by many factors, such as:
−
−
−
Dirt and water/humidity accumulation on hidden parts.
Dirt accumulation along airplane’s external surfaces.
Addition of new equipment, such as galley items, manuals, life
vests, rafts, etc.
− Maintenance structural repairs.
A small increase on the airplane’s weight may lead to significant
additional yearly costs. The chart below shows the impact of a 200 kg
(440 lb) increase in the OEW different trip distances:
EXPECTED FUEL BURN INCREASE DUE TO EXTRA 200 KG IN THE OEW
0.70%
TRIP FUEL INCREASE
0.65%
0.60%
E135
E145
0.55%
0.50%
0.45%
200
300
400
500
600
700
800
TRIP DISTANCE (NM)
8
REVISION 4
GP-145/1536
This extra 200 kg could result in up to 15 kg of extra fuel being
consumed in each flight.
GENERAL
PUBLICATION
FUEL CONSERVATION
Considering Typical Operational Profile:
ADDITIONAL FUEL BURN DUE TO 200 kg (440 lb) INCREASE IN
OEW
AIRPLANE
ERJ135
ERJ145
ANNUAL EXTRA FUEL
BURN
262000 kg
577700 lb
299500 kg
660300 lb
ANNUAL EXTRA COST
(US$)
258,600.00
295,600.00
WHAT CAN BE DONE TO PREVENT OEW INCREASE?
Some actions are suggested, but they must be carefully evaluated by
each airline, considering each particular operational scenario and
philosophy. For example:
−
GP-145/1536
Use of fixed Basic Empty Weights (BEWs) increased for
different crew/pantry configurations, according to the type of
the flight, instead of average Basic Operational Weights
(BOWs) with average pantries and calculation of the Flight
Plan by tail number instead of considering the average OEW,
leading to more efficient fuel burn.
− Emergency equipment: Items associated to Overwater
Operations should be placed on board only when necessary
(such as life rafts and life vests).
− Maintenance inspections of thermal/acoustic blankets or other
areas capable of water/moisture accumulation should be
regularly performed.
− Keeps the airplane interior clean, avoiding the accumulation of
dust, garbage or water inside the main cabin hidden areas.
− When added up, items such as magazines, newspapers,
publicity, as well as pillows, blankets and catering in excess
could result in significant additional fuel consumption.
Therefore, the presence of these items in the airplane should
be carefully analyzed.
A weight control program is essential to detect an OEW increase.
REVISION 4
9
FUEL CONSERVATION
GENERAL
PUBLICATION
FLIGHT PLANNING
An optimized flight begins with optimized flight planning. The fuel
conservation policy should be present during dispatch procedures in
order to minimize the Cash Operational Cost of a trip.
In order to do this, some important topics are suggested.
REGULATORY RESERVES AND DISPATCH POLICY
Less onboard reserve fuel means less fuel consumption in flight.
On a typical leg scenario (less than 800 NM or 2 hours flight) the most
significant factor in reserve fuel is the alternate trip fuel, and
meteorological factors have a strong impact on alternate choices.
Consider an alternate airport distance of 200 NM from the destination
airport and also the Typical Flight Profile. The following chart shows
trip fuel variation for every 100 NM increase of distance:
EXPECTED FUEL BURN INCREASE COMPARING WITH AN ALTERNATE
AIRPORT 200NM FAR FROM DESTINATION
5.0%
TRIP FUEL INCREASE
4.0%
3.0%
E135
E145
2.0%
1.0%
0.0%
300
400
500
600
700
800
10
REVISION 4
GP-145/1536
ALTERNATE AIRPORT DISTANCE (NM)
GENERAL
PUBLICATION
FUEL CONSERVATION
Considering Typical Operational Profile:
EVERY 100 NM INCREASE IN
ALTERNATE AIRPORT DISTANCE MEANS
AIRPLANE
ERJ135
ERJ145
ANNUAL EXTRA FUEL
BURN
307000 kg
676800 lb
373000 kg
822300 lb
ANNUAL EXTRA COST
(US$)
303,000.00
368,100.00
EXTRA FUEL CONSIDERATIONS
GP-145/1536
Reliable dispatch information is very important in order to aid the
Captain in defining the final fuel on board for the flight. The suggested
fuel on board calculated by the dispatch systems will consider all the
factors that may interfere with flight safety.
Meteorological factors along the route and at destination are certainly
significant and may be considered on the suggested fuel on board
through the dispatch release analysis.
Adding unnecessary extra fuel increases takeoff weight and leads to
an increase of trip fuel.
REVISION 4
11
FUEL CONSERVATION
GENERAL
PUBLICATION
The following chart below shows the impact of adding extra 200 kg
(440 lb) of fuel for different trip distances:
EXPECTED FUEL BURN INCREASE ADDING 200 KG OF EXTRA FUEL
0.70%
TRIP FUEL INCREASE
0.65%
0.60%
E135
E145
0.55%
0.50%
0.45%
200
300
400
500
600
700
800
TRIP DISTANCE (NM)
Considering Typical Operational Profile:
ADDITION OF 200 kg (440 lb) OF EXTRA FUEL MEANS
ERJ135
ERJ145
12
ANNUAL EXTRA FUEL
BURN
262000 kg
577700 lb
299500 kg
660300 lb
ANNUAL EXTRA COST
(US$)
258,600.00
295,600.00
REVISION 4
GP-145/1536
AIRPLANE
GENERAL
PUBLICATION
FUEL CONSERVATION
OPTIMUM CRUISE ALTITUDE
GP-145/1536
The Optimum Cruise Altitude is the pressure altitude, for a given
weight and speed, that provides maximum specific range, it is also
reasonable to define the Optimum Cruise Altitude as the altitude at
which the entire flight fuel burn is minimized (i.e., minimizing Climb +
Cruise + Descent fuel).
For trip distances longer than 400 NM, the ERJ135/145 Family
optimum altitude is equal to the maximum operating altitude of
37000 ft. For shorter trip distances refer to the AOM’s Flight Planning
section.
REVISION 4
13
FUEL CONSERVATION
GENERAL
PUBLICATION
The chart below shows the impact of flying below the optimum altitude
for several trip distances.
EXPECTED FUEL BURN INCREASE FLYING BELOW FL370
(OPTIMUM ALTITUDE)
30%
TRIP FUEL INCREASE
25%
20%
15%
E 135
E 145
10%
5%
0%
400
500
600
700
800
TRIP DISTANCE (NM)
Considering Typical Operational Profile:
ADDITIONAL FUEL BURN FLYING 2000 FT
BELOW OPTIMUM ALTITUDE
ERJ135
ERJ145
14
ANNUAL EXTRA FUEL
BURN
1423000 kg
3137150 lb
1200000 kg
2645500 lb
ANNUAL EXTRA COST
(US$)
1,404,400.00
1,184,300.00
REVISION 4
GP-145/1536
AIRPLANE
FUEL CONSERVATION
GENERAL
PUBLICATION
CRUISE SPEED SELECTION
Long Range Cruise (LRC) tables and Maximum Speed Cruise (MSC)
tables are provided in the AOM’s Flight Planning section.
−
LRC tables are recommended for flights in which fuel
consumption is a significant factor. The chart below illustrates
Mach versus specific range for several weights and altitudes
at LRC.
MACH AND SPECIFIC RANGE IN FUNCTION OF WEIGHT AND ALTITUDE
FOR E145 IN LRC
0.570
SPECIFIC RANGE (NM/kg)
0.530
0.490
0.450
0.410
0.370
0.330
0.290
0.250
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
MACH
−
MSC tables are used in flights in which minimum trip time is a
significant factor.
GP-145/1536
Depending on the operator’s time related costs, intermediate speed
schedules may be chosen in order to minimize Cash Operational
Costs. Other speed tables may be provided through the INFLIGHT
PERFORMANCE SOFTWARE.
REVISION 4
15
FUEL CONSERVATION
GENERAL
PUBLICATION
The following charts show the impact of flying at lower Mach numbers
than M0.78, which is the cruise regime used in this document, during
cruise for the Typical Operational Profile.
EXPECTED FUEL BURN REDUCTION OF FLYING M0.74 INSTEAD OF M0.78
IN CRUISE
0.0%
TRIP FUEL IMPACT
-0.5%
-1.0%
E135
E145
-1.5%
-2.0%
-2.5%
-3.0%
200
300
400
500
600
700
800
TRIP DISTANCE (NM)
EXPECTED TRIP TIME INCREASE OF FLYING M0.74 INSTEAD OF M0.78 IN
CRUISE
TRIP TIME INCREASE
4.0%
3.0%
2.0%
E135
E145
1.0%
0.0%
200
300
400
500
600
700
800
16
REVISION 4
GP-145/1536
TRIP DISTANCE (NM)
GENERAL
PUBLICATION
FUEL CONSERVATION
EXPECTED FUEL BURN REDUCTION OF FLYING M0.76 INSTEAD OF M0.78
IN CRUISE
0.00%
TRIP FUEL IMPACT
-0.25%
-0.50%
E135
E145
-0.75%
-1.00%
-1.25%
-1.50%
200
300
400
500
600
700
800
TRIP DISTANCE (NM)
Considering the Typical Operational Profile (37000 ft cruise altitude)
there is no difference in Trip Time between M0.76 and M0.78 regimes
for routes of 200 NM and shorter distances.
EXPECTED TRIP TIME INCREASE OF FLYING M0.76 INSTEAD OF M0.78 IN
CRUISE
TRIP TIME INCREASE
2.0%
1.5%
1.0%
E135
E145
0.5%
0.0%
300
400
500
600
700
800
GP-145/1536
TRIP DISTANCE (NM)
REVISION 4
17
FUEL CONSERVATION
GENERAL
PUBLICATION
EXPECTED FUEL BURN REDUCTION OF FLYING LRC INSTEAD OF M0.78
IN CRUISE
0.0%
TRIP FUEL IMPACT
-1.0%
-2.0%
E135
E145
-3.0%
-4.0%
-5.0%
200
300
400
500
600
700
800
TRIP DISTANCE (NM)
EXPECTED TRIP TIME INCREASE OF FLYING LRC INSTEAD OF M0.78 IN
CRUISE
12.0%
TRIP TIME INCREASE (%)
10.0%
8.0%
6.0%
E135
E145
4.0%
2.0%
0.0%
200
300
400
500
600
700
800
18
REVISION 4
GP-145/1536
TRIP DISTANCE (NM)
GENERAL
PUBLICATION
FUEL CONSERVATION
Considering Typical Operational Profile:
ADDITIONAL FUEL BURN FLYING M0.78 INSTEAD OF M0.76 IN
CRUISE
ANNUAL EXTRA FUEL
ANNUAL EXTRA COST
AIRPLANE
BURN
(US$)
299500 kg
295,600.00
ERJ135
660300 lb
224600 kg
221,700.00
ERJ145
495200 lb
ADDITIONAL FUEL BURN FLYING M0.78 INSTEAD OF M0.74 IN
CRUISE
AIRPLANE
ERJ135
ERJ145
ANNUAL EXTRA FUEL
BURN
599000 kg
1320600 lb
449200 kg
990400 lb
ANNUAL EXTRA COST
(US$)
591,200.00
443,400.00
GP-145/1536
ADDITIONAL FUEL BURN FLYING M0.78 INSTEAD OF LRC IN
CRUISE
ANNUAL EXTRA FUEL
ANNUAL EXTRA COST
AIRPLANE
BURN
(US$)
1347800 kg
1,330,200.00
ERJ135
2971400 lb
748800 kg
739,000.00
ERJ145
1650800 lb
REVISION 4
19
FUEL CONSERVATION
GENERAL
PUBLICATION
FUEL TANKERING
Fuel tankering is a procedure adopted by airlines when there is a high
fuel price differential between origin and destination airports and, if it is
cost effective, the airline will load additional fuel at the origin airport in
order to minimize (or even avoid) refueling at the destination airport,
reducing the total fuel cost.
Fuel tankering information is provided on chart format in EMBRAER
AOM Flight Planning Section. Fuel surplus tables are provided for LRC
and M0.78, as function of trip distance.
The following factors must be observed:
− The amount of fuel tankered must be such that the total fuel
remaining at the end of the flight shall not exceed the
minimum fuel required for the next flight, unless a fuel
tankering analysis has been done for a multi-leg flight.
− Tankered fuel may not cause the airplane’s weight to exceed
the maximum takeoff and landing weights;
− Due to increased landing weights, additional maintenance
costs may be expected as a result of fuel tankering. Tire and
brake wear are the most affected items. In order to
compensate, some operators adjust the break-even fuel price
on destination by another factor. This factor is usually
“empirical” and is determined by airlines based on each
maintenance costs and is not considered in AOM charts;
When a quick analysis of the fuel tankering feasibility is required, it is
recommended that the Operator generates a quick reference table to
be consulted by Flight Dispatchers and Pilots, during the calculation of
the fuel required for takeoff, for example:
FUEL TANKERING - QUICK REFERENCE TABLE
ERJ 145 - LRC
Origin Dest
AAA
AAA
AAA
BBB
BBB
CCC
DDD
DDD
BBB
CCC
DDD
CCC
DDD
BBB
AAA
FFF
Distance Reference
(NM)
FL
350
600
850
500
650
500
700
800
350
350
370
350
350
350
370
370
Fuel
Burn
Surplus
Price at
Origin
(US$/Gal)
Price at
Dest
(US$/Gal)
Break Even
Price
(US$/Gal)
FUEL
TANKERING
3.5%
3.5%
8.5%
5.0%
6.5%
5.0%
7.0%
8.0%
3.50
3.50
3.50
4.80
4.80
4.00
4.50
4.50
4.80
4.00
4.50
4.00
4.50
4.80
3.50
3.70
3.63
3.63
3.83
5.05
5.13
4.21
4.84
4.89
ECON
ECON
ECON
NOT ECON
NOT ECON
ECON
NOT ECON
NOT ECON
20
REVISION 4
GP-145/1536
TABLE ABOVE IS ILLUSTRATIVE AND VALUES PRESENTED SHOULD NOT BE USED IN REAL
OPERATION.
GENERAL
PUBLICATION
FUEL CONSERVATION
IN FLIGHT PROFILE
GROUND OPERATIONS
APU USE ON GROUND
Considering an average aviation fuel price of US$ 3.00/Gal, the cost of
APU energy is many times greater than GPUs expenditure. From a
fuel conservation point of view, it is far better to use a GPU as an
electrical power source when the airplane is parked.
However, operators should verify if APU continuous use at the gate
instead of GPU is the best option, considering:
−
−
GP-145/1536
APU main components fail by cycle;
APU may provide pneumatic pressure to the packs on the
ground when no other sources are available (such as external
air carts);
− GPU power is sometimes leased from handling companies
and may be charged by the hour.
When continuous APU ground use is a choice, it is recommended that,
whenever possible, APU usage time be minimized. It should be
shutdown after engines start and start up only after landing, if required.
Also, the tradeoff between engine fuel versus APU usage, accounting
for APU fuel plus APU cycle charges, should also be investigated by
each airline, aiming at knowing when it is cost effective to maintain the
engines running while waiting for ground service.
For ground and in-flight APU consumption information, refer to the
AOMs Flight Planning section.
REVISION 4
21
FUEL CONSERVATION
GENERAL
PUBLICATION
AIR CONDITIONING USE ON THE GROUND
The pneumatic air supplied by the APU may be used for air
conditioning on the ground, with the airplane parked. The APU fuel
flow economy between use maximum electrical load only instead of
maximum electrical and pneumatic is 0.47 kg/min (1.04 lb/min).
In a typical 30-min turn around time, if using APU with maximum
electrical load only, 14 kg (31 lb) of fuel per ground stop can be saved
when comparing with pneumatic and electrical supply operation.
Considering the Typical Operational Profile:
APU Operations on the ground with electrical load and no
pneumatic bleed means:
528000 kg (1164000 lb) fuel economy ~ US$ 521,100.00
potential savings (per year/20 AIRPLANE fleet)
22
REVISION 4
GP-145/1536
Operators should evaluate the cost of using external air source when
compared to the APU cost. In the case of APU usage on ground it is
recommended to take bleed load only from one pack unless required
for cabin comfort.
GENERAL
PUBLICATION
FUEL CONSERVATION
SINGLE ENGINE TAXI
Single engine taxi can be performed in order to save fuel. Some
considerations should be given to evaluate the feasibility of this
procedure, such as:
−
Ramp weight and ramp gradient: heavier airplane and/or
positive ramp slopes demand more power.
− Taxi time to active runway.
− Engine warm up and cooling down period.
− Higher crew workload.
The start of the second engine should preferably be performed with
the airplane static, since engine start while taxiing may lead to higher
Pilot workload.
On single engine taxi, the fuel flow is approximately 300 kg/h
(661 lb/h). For dual engine taxi, fuel flow is presented on AOM’s Flight
Planning section, APU and Engine Fuel Consumption. Based on these
numbers, for each 1 minute of single engine taxi instead of a dual
engine taxi, approximately 2 kg of fuel is saved.
Considering that for the Typical Operational Profile, in each leg
10 minutes of single engine taxi is performed, instead of dual engine.
Savings are presented on the table below:
10 minutes of single engine taxi per leg means:
748800 kg (1650819 lb) of fuel economy ~ US$ 741,000.00
potential savings (per year/20 AIRPLANE fleet)
GP-145/1536
During taxi in, it is preferable to shut engine number 1 down. For more
information refer to EMBRAER Flight Operations Publications.
REVISION 4
23
FUEL CONSERVATION
GENERAL
PUBLICATION
TAKEOFF
Lower flap selections will provide lower fuel consumption on takeoff.
The higher the flaps retraction altitude (beginning of the 3rd segment),
the higher the fuel consumption during the takeoff path.
Acceleration Altitude
The minimum flaps retraction altitude is the lowest value that can be
used for acceleration and flaps retraction and is defined by each
regulation (for example: FAA requires 400 ft and JAA/EASA requires
800 ft). This value is selectable in the TAKEOFF ANALYSIS program.
If obstacles along the takeoff flight path require higher altitudes in
order to meet regulatory clearance requirements, the software also
automatically increases this altitude.
CLIMB
The climb phase has a huge impact on fuel consumption when
considering short and medium range flights since it represents from
20% to 40% of the trip time, registering fuel flows 40% greater than on
cruise phase.
Climbing with reduced thrust will increase fuel consumption because it
would extend time spent at lower altitudes where the fuel flow is
higher. Therefore, reducing thrust during climb will not save fuel. On
the other hand, using thrust settings higher than CLB will severely
penalize engine life.
EMBRAER recommends the following standard climb speed schedule:
24
270 KIAS or M0.56 (whichever occurs first) above 10000 ft.
240 KIAS below 10000 ft.
REVISION 4
GP-145/1536
−
−
FUEL CONSERVATION
GENERAL
PUBLICATION
ANALYZING DIFFERENT CLIMB SCHEDULES
Lower climb speeds result on higher rates of climb and, consequently,
less time is spent to reach TOC. On the other hand, distance flown in
cruise will increase.
Higher climb speeds result on lower rates of climb and, consequently,
more time is spent to reach TOC. On the other hand, distance flown in
cruise will decrease.
Based on the information brought by the previous paragraphs, the
climb phase shall not be analyzed separately. The impact over the
total trip fuel is the best way to check a climb schedule.
INITIAL CRUISE
ALTITUDE
0.
/M
kia
ias
0
0k
28
27
ALTITUDE
s
/M
0.5
6
60
TOC
2
90
0.
65
/M s/M
s
ia
kia 0 k
0
3
0.
65
HIGHER CLIMB
SPEEDS
DISTANCE
EM145AOM000055A.DGN
GP-145/1536
The following charts show the trip fuel differences when using different
climb schedules above 10000 ft, compared with the standard climb
profile (270 KIAS/M0.56) for ERJ145 and ERJ135:
REVISION 4
25
FUEL CONSERVATION
GENERAL
PUBLICATION
ERJ-145 EXPECTED FUEL BURN INCREASE COMPARING DIFFERENT
CLIMB SCHEDULES TO 270 KIAS / M 0.56
TRIP FUEL INCREASE
4,0%
3,5%
280 KIAS / M0.60
290 KIAS / M0.65
3,0%
300 KIAS / M0.65
2,5%
2,0%
1,5%
1,0%
0,5%
0,0%
300
400
500
600
700
800
TRIP DISTANCE (NM)
ERJ-135 EXPECTED FUEL BURN INCREASE COMPARING DIFFERENT
CLIMB SCHEDULES TO 270 KIAS / M 0.56
TRIP FUEL INCREASE
4,0%
3,5%
280 KIAS / M0.60
290 KIAS / M0.65
3,0%
300 KIAS / M0.65
2,5%
2,0%
1,5%
1,0%
0,5%
0,0%
300
400
500
600
700
800
26
REVISION 4
GP-145/1536
TRIP DISTANCE (NM)
GENERAL
PUBLICATION
FUEL CONSERVATION
Compared to 270 KIAS/M0.56 climb schedule, the climb schedules
shown on the graphics above presented a reduction in trip time of up
to 1 minute.
For 200 NM of trip distance, the airplane does not have performance
to climb with the 290 KIAS/M0.65 schedule or higher to FL 370, so it
was not considered in this chart.
CLIMB SPEEDS LOWER THAN 270 KIAS/M0.56
Climb schedules defined by speeds lower than 270 KIAS/M0.56 were
also analyzed and either presented negligible gains in terms of trip fuel
or an increase in fuel consumption.
Considering Typical Operational Profile, comparing 290 KIAS/M0.65
and 270 KIAS/M0.56 Climb Schedules:
GP-145/1536
ADDITIONAL FUEL BURN DUE TO CLIMB WITH
290 KIAS/M0.65 INSTEAD OF STANDARD CLIMB SPEED
SCHEDULE
ANNUAL EXTRA FUEL
ANNUAL EXTRA COST
AIRPLANE
BURN
(US$)
936000 kg
923,800.00
ERJ135
2063500 lb
1050000 kg
1,036,300.00
ERJ145
2314850 lb
REVISION 4
27
FUEL CONSERVATION
GENERAL
PUBLICATION
CRUISE SPEED MANAGEMENT
Speed variations above the planned speeds may lead to significant trip
fuel burn. Speed measure has a large impact on specific range.
The crew should ensure, during walk around that the pitot tubes, TAT
probes and static ports are clean and free of obstructions, so that it
may provide correct speed, Mach number and TAT calculations. The
impact of flying with a speed 1% faster in terms of TAS (M0.01),
compared with planned cruise speed is:
EXPECTED FUEL BURN INCREASE OF FLYING M0.01 (~ 1% TAS
VARIATION) FASTER THAN PLANNED CRUISE SPEED
0.6%
TRIP FUEL INCREASE
0.5%
0.4%
E135
E145
0.3%
0.2%
0.1%
0.0%
200
300
400
500
600
700
800
TRIP DISTANCE (NM)
28
REVISION 4
GP-145/1536
As long as the fuel is burned, the airplane gross weight decreases and
some adjustment is required on the thrust lever to maintain the
planned speed. The variation of 1% in terms of TAS is expected to
occur for every 1000 kg (2200 lb) of fuel burned in cruise phase.
FUEL CONSERVATION
GENERAL
PUBLICATION
EXPECTED FUEL BURN INCREASE OF FLYING M0.01(~ 1 TAS
VARIATION) FASTER THAN PLANNED CRUISE SPEED
AIRPLANE
ANNUAL EXTRA FUEL
BURN
ANNUAL EXTRA COST
(US$)
150000 kg
ERJ135
148,000.00
330700 lb
112300 kg
ERJ145
110,800.00
247600 lb
The values above are valid for several cruise speeds and not only to
the Typical Operational Profile.
LATERAL NAVIGATION OPTIMIZATION
Lateral navigation has impact on trip fuel and time, but deviations from
planned flight path may occur due to ATC requirements or
meteorological conditions.
Consider a lateral flight path length only 1% longer than that planned
for the trip. For typical flight speed schedule and optimum flight level,
extra fuel is found for different leg lengths:
EXPECTED FUEL BURN INCREASE FLYING EXTRA 1% ON MISSION
LENGTH
1.0%
TRIP FUEL INCREASE
0.9%
0.8%
E135
E145
0.7%
0.6%
0.5%
0.4%
200
300
400
500
600
700
800
GP-145/1536
TRIP DISTANCE (NM)
REVISION 4
29
FUEL CONSERVATION
GENERAL
PUBLICATION
Route planning should always be performed considering the shortest
(and feasible) distance between origin and destination airports.
Considering Typical Operational Profile:
ADDITIONAL FUEL BURN DUE TO 1% INCREASE
ON LEG DISTANCE
AIRPLANE
ERJ135
ERJ145
ANNUAL EXTRA FUEL
BURN
375000 kg
826725 lb
375000 kg
826725 lb
ANNUAL EXTRA COST
(US$)
370,100.00
370,100.00
DESCENT
30
REVISION 4
GP-145/1536
Even though descent fuel consumption has a minor impact compared
with other flight phases, it is important to plan a correct descent profile.
Less fuel is burned during descent phase at higher speeds (late
profiles) once descent time becomes shorter, however comparing
different schedules in flight idle descent, the trip fuel consumption will
increase in this case once descent distance is reduced and cruise
distance is stretched.
GENERAL
PUBLICATION
FUEL CONSERVATION
As an example, the following chart shows the trip fuel difference when
comparing the following flight idle descent schedules:
−
−
(Lower speed regime) Mmo or 250 KIAS (whichever occurs
first) above 10000 ft and 240 KIAS below 10000 ft.
(Higher speed regime) Mmo or 300 KIAS (whichever occurs
first) above 10000 ft and 240 KIAS below 10000 ft.
EXPECTED FUEL BURN INCREASE COMPARING DESCENT WITH
250 KIAS/M0.78 (LOW SPEED) AND 300 KIAS/M0.78 (HIGH SPEED)
1.7%
TRIP FUEL INCREASE
1.5%
1.3%
E135
E145
1.1%
0.9%
0.7%
0.5%
200
300
400
500
600
700
800
TRIP DISTANCE (NM)
GP-145/1536
Considering a flight idle descent, higher speed schedules will increase
the trip fuel.
It is important to mention that very early descents will also cause trip
fuel increase. In case the best profile can not be used, it is preferable
to start slightly early than late, because the optimum profile can still be
reached.
REVISION 4
31
FUEL CONSERVATION
GENERAL
PUBLICATION
The Flight Level Change mode will provide fixed rate of descent.
However, this procedure will lead to trip fuel increase because it
requires thrust application.
The following chart shows the trip fuel difference when comparing
descent in 3° FPA with Flight Level Change mode versus flight idle for
M0.76/300 KIAS speed schedule.
EXPECTED FUEL BURN INCREASE COMPARING DESCENT WITH 3° FPA
FLC MODE VERSUS FLIGHT IDLE FOR A GIVEN SPEED SCHEDULE
2.00%
TRIP FUEL INCREASE
1.75%
1.50%
E135
E145
1.25%
1.00%
0.75%
0.50%
300
400
500
600
700
800
TRIP DISTANCE (NM)
Considering Typical Operational Profile:
32
REVISION 4
GP-145/1536
ADDITIONAL FUEL BURN DUE TO DESCENT WITH 3° FPA
FLIGHT LEVEL CHANGE MODE INSTEAD OF FLIGHT IDLE
ANNUAL EXTRA FUEL
ANNUAL EXTRA COST
AIRPLANE
BURN
(US$)
692600 kg
683,600.00
ERJ135
1526900 lb
599000 kg
591,200.00
ERJ145
1320500 lb
GENERAL
PUBLICATION
FUEL CONSERVATION
HOLDING
Holding is a maneuver that should be performed at the minimum fuel
consumption speed.
The holding tables for clean configuration are provided in the AOM’s
Flight Planning Section. They are calculated for the minimum fuel
consumption condition, leveled flight, further providing minimum
maneuver margin of 1.3 Vs or 200 KIAS under icing conditions.
Considering fuel conservation aspects, flying a holding pattern with
flaps extended should be avoided since it significantly increases fuel
consumption. For flaps 9°, fuel flow increases by approximately 8.5%.
APPROACH AND LANDING
The fuel consumption in the approach phase is influenced by two main
factors:
−
−
ATC requirements;
Pilot’s flying techniques.
ATC requirements are a function of airspace capacity and traffic flow
management and they are beyond Flight Crew control. Regarding
flying techniques, some factors may be evaluated:
−
Level flight at a constant speed always requires thrust
application and shall not be performed unless necessary.
− Knowledge of the deceleration rates of the airplane helps to
manage the energy on idle approach planning.
The table below shows the deceleration distances required for IDLE
thrust, for speed brakes up or down, with clean configuration:
LEVELED FLIGHT
1000 FPM DESCENT
FLIGHT
SPEEDBRAKES
DOWN (STOWED)
1.2 NM for each 10 kt
Speed reduction
2.0 NM for each 10 kt
Speed reduction
SPEEDBRAKES
UP (DEPLOYED)
0.6 NM for each 10 kt
Speed reduction
1.0 NM for each 10 kt
Speed reduction
GP-145/1536
CONFIGURATION
REVISION 4
33
FUEL CONSERVATION
GENERAL
PUBLICATION
Flaps and Gear extension
It is desirable to minimize the time spent under high drag
configuration. Thus, it is suggested to delay flaps and gear extension
as much as possible, but never extrapolating the stabilized approach
limits stated in the airline policy;
Fuel flow in landing configuration is 150% higher than in clean
configuration.
Flaps Choice
Considering fuel conservation aspects, it is desirable to land with flaps
22° whenever possible. Using Flaps 22°, 10 kg (22 lb) of fuel per
landing can be saved when compared with Flaps 45° landing.
It is recommended to use flaps 45º only where field limit is significant.
The table below shows the minimum field lengths for flaps 22º, at
maximum landing weight, DRY runway and no ice encounter.
FLAPS 22° – MINIMUM FIELD LENGTH
AIRPLANE
MSL
5000 ft
ERJ135
1700 m ( 5580 ft)
2000 m ( 6560 ft)
ERJ145
1850 m ( 6070 ft)
2100 m ( 6890 ft)
SUMMARY
Considering everything previously stated, it should be noted that small
quantities of fuel saved during a flight might seem insignificant when
evaluated separately, but have a huge impact when looking at annual
costs of a fleet.
34
REVISION 4
GP-145/1536
1% fuel savings are easily reached when applying relatively
simple operational procedures during day-to-day operations.
GENERAL
PUBLICATION
FUEL CONSERVATION
The following tables summarize the annual fuel and cost increase for
the most significant factors stated herein, considering the Typical
Operational Profile. The values may vary in function of the Operator
fleet, flight network and fuel prices.
ERJ135 FUEL PENALTIES TABLE
ITEM
Increase of 200 kg on OEW
TRIP FUEL
INCREASE
kg / lb
%
7
15
8
Increase of 100 NM on alternate
distance
18
Increase of 200 kg on FOB
required
15
Flying 2000 ft below optimum
altitude
Flying M0.78 instead of M0.76
Flying M0.78 instead of M0.74
Flying M0.78 instead of LRC
7
38
84
8
18
16
35
36
79
APU Operations on ground with
electrical and pneumatic load
instead of electrical load only
14
High speed climb
290 KIAS/M0.65 above 10000 ft
25
10 minutes of Dual Engine Taxi
per leg instead of Single Engine
Taxi
20
Cruising M0.01(approx 1 TAS
variation) faster than planned
4
Increase of 1% in mission length
Descent with 3° FPA in Flight
Level Change mode
55
44
9
10
22
19
42
10
22
0.68
0.58
3.15
0.68
1.33
2.99
1.17
2.07
--0.33
0.85
1.52
0.85
262000 kg
577700 lb
307000 kg
676800 lb
262000 kg
577600 lb
1423000 kg
3137150 lb
299500 kg
660300 lb
599000 kg
1320600 lb
1347800 kg
2971400 lb
528000 kg
1164000 lb
936000 kg
2063500 lb
748800 kg
1650820 lb
150000 kg
330700 lb
375000 kg
826725 lb
692600 kg
1526900 lb
375000 kg
826725 lb
APROX ANNUAL
EXTRA COST
(US$)
258,600
303,000
258,600
1,404,400
295,600
591,200
1,330,200
521,100
923,800
741,000
148,000
370,100
683,600
370,100
GP-145/1536
Use of Full Flaps on landing
31
0.58
ANNUAL
EXTRA FUEL
REVISION 4
35
FUEL CONSERVATION
GENERAL
PUBLICATION
ERJ145 FUEL PENALTIES TABLE
TRIP FUEL
INCREASE
kg / lb
Increase of 200 kg on OEW
Increase of 100 NM on alternate
distance
Increase of 200 kg on FOB
required
Flying 2000 ft below optimum
altitude
Flying M0.78 instead of M0.76
Flying M0.78 instead of M0.74
Flying M0.78 instead of LRC
8
18
10
22
8
18
32
71
6
13
12
26
20
40
APU Operations on ground with
electrical and pneumatic load
instead of electrical load only
10 minutes of Dual Engine Taxi
per leg instead of Single Engine
Taxi
14
High speed climb 290 KIAS/M0.65
above 10000 ft
28
Cruising M0.01 (approx 1% TAS
variation) faster than planned
3
Increase of 1% in mission length
Descent with 3° FPA in Flight
Level Change mode
Use of Full Flaps on landing
36
31
20
44
62
7
10
22
16
35
10
22
%
0.64
0.79
0.64
2.54
0.48
0.95
1.59
1.12
---
2.22
0.24
0.79
1.26
0.79
ANNUAL
EXTRA FUEL
299500 kg
660300 lb
373000 kg
822300 lb
299500 kg
660300 lb
1200000 kg
2645500 lb
224600 kg
495200 lb
449200 kg
990400 lb
748800 kg
1650800 lb
528000 kg
1164000 lb
748800 kg
1650820 lb
1050000 kg
2314850 lb
112300 kg
247600 lb
375000 kg
826725 lb
599000 kg
1320500 lb
375000 kg
826725 lb
ANNUAL
EXTRA COST
(US$)
295,600
368,100
296,000
1,184,300
221,700
443,400
739,000
521,100
741,000
1,036,300
110,800
370,100
591,200
370,100
REVISION 4
GP-145/1536
ITEM
GENERAL
PUBLICATION
FUEL CONSERVATION
SECTION III – MAINTENANCE PRACTICES
UTILISATION OF MEL AND CDL
MEL – MINIMUM EQUIPMENT LIST
GP-145/1536
The Minimum Equipment List – MEL – allows the dispatch of the
airplane with certain inoperative systems, giving more flexibility to the
day-by-day operations.
However, in such cases, some operational restrictions, procedures or
other limitations may have a significant impact on fuel consumption.
The intention of addressing this issue in this document is to highlight
situations where the dispatch of the airplane based on MEL relieves,
although giving good flexibility, it can bring an increase of fuel
consumption.
The following table shows MEL items that impose some kind of
limitation that have a direct effect on fuel consumption. Percentage of
trip fuel increase and extra fuel cost are based on the defined Typical
Operational Profile.
The extra fuel cost is calculated for one airplane that is dispatched
based on a specific MEL relief, for the entire period allowed by MEL:
REVISION 4
37
FUEL CONSERVATION
GENERAL
PUBLICATION
DESCRIPTION
21-22-04
External Ground
Connector
Check valve
1
0
2
1
2
0
21-25-01
R
E
Q
U
I
R
E
D
Ram Air Valves
FUEL PENALTY
LIMITATION
Flight conducted
at unpressurized
condition
(FL 100)
At or below
FL 250
Flight conducted
at unpressurized
condition
(FL 100)
Flight conducted
at unpressurized
condition
(FL 100)
Flight conducted
at unpressurized
condition
(FL 100)
Flight conducted
at unpressurized
condition
(FL 100)
At or below
FL 250
Flight conducted
at unpressurized
condition
(FL 100)
TRIP
FUEL
INCR
EASE
(%)
EXTRA
FUEL
COST
FUEL
(US$/
FLIGHT)
MEL
TIME
LIMIT
(DAYS)
EXTRA
FUEL
COST
(US$)/
MEL
TIME
LIMIT
46
600
3
10,300
23
300
10
17,200
46
600
10
34,500
46
600
10
34,500
46
600
10
34,500
46
600
10
34,500
23
300
10
17,200
46
600
10
34,500
21-30-00
Pressurization
Control System
(Auto Manual)
2
0
21-31-03
Outflow Valves
(Electropneumatic and
Pneumatic)
2
0
21-32-01
Cabin Pressure
Acquisition
Module
1
0
2
1
21-51-00
Air Cond Pack
System
2
0
2
0
At or below
FL 250
23
300
10
17,200
1
0
At or below
FL 300
23
300
10
17,200
2
1
23
300
10
17,200
2
0
32
400
10
23,900
2
0
46
600
10
34,500
1
0
46
600
10
34,500
21-60-04
35-20-00
36-11-05
52-51-00
38
Cockpit
Automatic
and Manual
Temp Control
System
Passenger
Oxygen System
(AUTO)
Engine Bleed
System
C&D Aerospace
Flight Deck
Security Door
(Press Rel
Latch)
At or below
FL 250
At or above
FL 180 (with
APU)
Flight conducted
at unpressurized
condition
(FL 100)
(without APU)
Flight conducted
at unpressurized
condition
(FL 100) EASA
ONLY
REVISION 4
GP-145/1536
MEL
ITEMS
I
N
S
T
A
L
L
E
D
GENERAL
PUBLICATION
FUEL CONSERVATION
GP-145/1536
The following charts present the trip fuel increase caused by the
altitude limitation on FL250, FL180 and FL100:
REVISION 4
39
40
GENERAL
PUBLICATION
REVISION 4
GP-145/1536
FUEL CONSERVATION
GENERAL
PUBLICATION
FUEL CONSERVATION
GP-145/1536
The total estimated figures indicate that the extra costs related to fuel
consumption due to the MEL operational restrictions are around
US$ 6,000,000 per year (world wide fleet).
Therefore, to rectify a MEL item as quickly as possible is not only a
good practice in order to minimize the impact in maintenance and
operation, but also a required action to avoid incurrence of extra costs
due to the increased fuel consumption.
Good practices to expedite the MEL items rectification may involve
analysis of occurrences at each airline and logistics evaluation for
strategically provisioning critical parts in the main maintenance bases.
REVISION 4
41
FUEL CONSERVATION
GENERAL
PUBLICATION
CONFIGURATION DEVIATION LIST – CDL
The CDL allows the dispatch of airplane with missing parts or
equipment. However in such conditions, the aerodynamic performance
of the airplane is affected, and increases fuel consumption.
A detailed analysis of the impact of missing parts is presented in item
“Aerodynamic Deterioration”, “Missing Parts – CDL” in this document.
AERODYNAMIC DETERIORATION
Aerodynamic deterioration results in increased aerodynamic drag,
which is one of the most severe penalties regarding fuel consumption.
The higher the drag, the higher the thrust required to keep the airplane
flying properly, which leads to increased fuel consumption and
reduced specific ranges.
Undetermined drag penalties may arise through the years, when the
airplane is subjected to line operations. Deviations from “book
performance” may possibly be caused by various surface distortions,
such as:
−
−
−
−
−
−
−
−
−
−
42
REVISION 4
GP-145/1536
Mismatched doors and windows;
Mismatched access panels;
Mismatched rivets;
Leaking seals;
Improper aerodynamic sealing;
Skin roughness;
Dirt accumulation on external surfaces;
Out-of-rigging control surfaces;
Deteriorated painting;
Mechanical wear and improperly executed external repairs.
The effect of small degradations is cumulative and may lead to
significant additional fuel consumption after years of use. A wellmaintained airplane is expected to have 0.5% of drag degradation
after 10 years of use.
These drag penalties and deteriorations shall be treated by the
appropriate maintenance practices and are supposed to be controlled
after some years.
In practical terms, the impact of 1% drag degradation in fuel
consumption (trip fuel increase) is shown in the following chart:
GENERAL
PUBLICATION
FUEL CONSERVATION
The aerodynamic analysis conducted in the topics of this document is
based on “trip fuel” increase (in terms of %), which is used to quantify
the increase in fuel consumption, later transformed in additional fuel
costs. The term “fuel penalty” refers to the increasing of fuel
consumption in terms of “trip fuel” and associated costs.
The impact of 1% of drag degradation on fuel consumption
considering the assumed Typical Operational Profile is presented in
the table below. The extra fuel burn and extra fuel cost are calculated
for one airplane for one year period.
ADDITIONAL FUEL BURN DUE TO
1% DRAG DEGRADATION
AIRPLANE
kg
20550
22500
lb
45304
49603
ANNUAL
EXTRA COST
(US$/ACFT)
20,300
22,300
GP-145/1536
ERJ135
ERJ145
ANNUAL EXTRA FUEL
BURN (PER ACFT)
REVISION 4
43
FUEL CONSERVATION
GENERAL
PUBLICATION
MISSING PARTS – CDL
The Configuration Deviation List – CDL allows the dispatch of the
airplane with missing parts and give to the airline flexibility in the dayby-day operations. Those parts have to be reinstalled at earliest
possible opportunity.
However, the missing external parts cause changes on the
aerodynamic flow and consequently, aerodynamic drag and fuel
consumption increase.
The following table summarizes the relevant missing items that may
impose fuel penalties. Percentage of trip fuel increase and extra fuel
cost are based on the defined Typical Operational Profile. The extra
fuel cost is calculated for one airplane for one year period.
CDL ITEMS
MISSING PART
Nose hydraulic
compartment access
Pneumatic start connection
access
APU access door
Inspection light protective
lens
Navigation light protective
lens (no winglet)
Main landing gear door
(fairing)
Main landing gear door
(main)
Fueling panel access door
Waste service door
Potable water service door
External power connection
access door
External main door control
access door
FUEL PENALTY
TRIP FUEL
EXTRA FUEL COST
INCREASE
(US$/ACFT/YEAR)
(%)
0.28
6,500
0.09
2,000
0.12
2,800
0.10
2,300
1.76
41,000
0.45
10,500
0.83
19,300
0.07
0.08
0.07
1,600
1,800
1,600
0.02
450
0.02
450
44
REVISION 4
GP-145/1536
NOTE: All data derived from theoretical calculations.
GENERAL
PUBLICATION
FUEL CONSERVATION
As an example, flying with one of the navigation light protective lens
missing means an extra fuel consumption cost of approximately
US$ 41,000.00 per airplane per year.
As in MEL practices, to rectify a CDL item as quickly as possible is,
therefore, not only a good practice to minimize the impact in
maintenance and operation, but also a required action to avoid
incurrence of extra costs due to the increased fuel consumption.
Good practices to expedite the CDL items rectification may involve
analysis of occurrences at each airline and logistics evaluation for
strategically provisioning critical parts in the main maintenance bases.
AERODYNAMIC SMOOTHNESS
The drag degradation is directly affected by the location of
aerodynamic deterioration on the airplane. There are regions on the
airplane where aerodynamic smoothness is more important. Those
regions are called critical areas. The critical areas are those where
significant changes on local pressure gradient are present. Surface
distortions in the critical areas may lead to significant increment of the
overall drag of the airplane because they may cause a separate flow,
thus abruptly increasing drag penalties.
Other aspects like boundary layer thickness and local airspeeds are
also important and may significantly influence local drag increase.
Other high sensitivity areas are those submitted to higher local
airspeeds. Generally they have very thin turbulent boundary layers
and high adverse pressure gradients. Some examples of such areas
are:
Wings;
Flaps and Slats;
Spoilers;
Ailerons.
GP-145/1536
−
−
−
−
REVISION 4
45
FUEL CONSERVATION
GENERAL
PUBLICATION
Critical Areas
The airplane external surface is divided into two areas:
Aerodynamically critical AREAS IA AND IB and Aerodynamically noncritical AREA II (following figure).
AERODYNAMICALLY CRITICAL AREAS IA AND IB requires a high
degree of aerodynamic smoothness. These AREAS are described as
follows:
¾ Area IA:
Internal surface of the nacelle inlet duct, from the lip skin leading
edge up to the fan.
¾ Area IB:
−
−
−
−
−
−
−
−
−
Fuselage: region 1, 2 and 3;
Nacelle: internal region (from inlet region up to frame 69) and
external region (from lipskin leading edge up to 50% nacelle
length);
Pylon: On upper and lower pylon surfaces, from leading edge
up to frame 69;
Wing: Inboard region (on upper and lower surfaces and from
leading edge up to spar 3) and Outboard region (on upper and
lower surfaces and from leading edge up to spar 2);
Flaps: On upper and lower surfaces, from flap leading edge up
to 30% chord;
Flaps vane: On upper and lower surfaces, from vane leading
edge up to 100% chord;
Horizontal tail: On upper and lower surfaces, from leading
edge up to 45% chord;
Vertical tail: On left and right surfaces, from leading edge up to
41% chord;
Elevator: On upper and lower surfaces.
46
REVISION 4
GP-145/1536
AERODYNAMICALLY NON-CRITICAL AREA II is not critical for
smoothness and it comprises the external surfaces not covered by
aerodynamically critical areas IA and IB.
GENERAL
PUBLICATION
FUEL CONSERVATION
Source: SRM 51-10-01
GP-145/1536
AERODYNAMIC AREAS CLASSIFICATION
REVISION 4
47
FUEL CONSERVATION
GENERAL
PUBLICATION
Parasite drag influence
The parasite drag may be defined as the drag not caused by lift.
Excluding the drag from airplane shape and weight, which is
unavoidable, parasite drag represents approximately 10% of the total
drag and is the one kind of drag that can be controlled and reduced
through preventive maintenance methods.
Basically, the relevant items related to parasite drag are:
−
−
−
−
Discrete items such as: antennas, lights, etc;
Mismatched surfaces;
Internal airflow through leaks, gaps, seals, etc;
Rough surfaces and waviness.
Recommendation:
All antennas must be installed so as to maximize the best fit
and fair considerations. This includes attention to the detail
of sealing compound applications where required.
Source: IATA - FUEL CONSERVATION THROUGH AIRCRAFT MAINTENANCE, 2000
Gaps and Steps
48
REVISION 4
GP-145/1536
Gaps and steps occur in mismatched joints between two panels on
external surface of the airplane. Typically those discrepancies can be
found in skin panel joints, ridge or depression between sealant and
skin surface, around access panels, doors, windows and others.
Gaps and steps cause increase in drag, resulting in extra fuel
consumption.
GENERAL
PUBLICATION
FUEL CONSERVATION
The definition of some types of gaps and steps are shown in the
following figure:
STEP AND GAP DEFINITIONS AND SIGN CONVENTION FOR
NORMAL STEPS
GP-145/1536
Source: SRM 51-10-01
REVISION 4
49
FUEL CONSERVATION
GENERAL
PUBLICATION
As per the Structural Repair Manual (SRM), the allowable steps and
gaps for skin joints are shown in the following table and figure.
50
REVISION 4
GP-145/1536
[1] FD: FLIGHT DIRECTION.
[2] ALL GAPS BETWEEN FIXED SURFACES SHOULD BE FILLED WITH APPROPRIATE
SEALANT AND SMOOTHED.
THE MAXIMUM ALLOWABLE RIDGE OR DEPRESSION BETWEEN THE SEALANT AND THE
SKIN SURFACE IS SHOWN IN FIGURE 3.
[3] 1.1 mm ON 80% OF RADOME PERIMETER;
1.4 mm ON 20% OF RADOME PERIMETER.
[4] 2.5 mm ON 80% OF APU COWLING PERIMETER;
3.0 mm ON 20% OF APU COWLING PERIMETER.
GENERAL
PUBLICATION
FUEL CONSERVATION
ALLOWABLE JOINTS BETWEEN FIXED SURFACES
Source: SRM 51-10-01
ALLOWABLE RIDGE OR DEPRESSION BETWEEN SEALANT AND
SKIN SURFACE
Source: SRM 51-10-01
Recommendations:
Ensure all aircraft external surface is in a fair condition,
performing periodical inspections to assure all joints, doors
and panels are free from gaps and steps. Ensure proper
sealing for aerodynamic smoothness where applicable.
GP-145/1536
Source: IATA - FUEL CONSERVATION THROUGH AIRCRAFT MAINTENANCE, 2000
REVISION 4
51
FUEL CONSERVATION
GENERAL
PUBLICATION
Missing Fillet Sealing
Although missing fillet sealing are allowed in some regions of the
airplane, they affect aerodynamic smoothness, causing an increase in
drag and fuel consumption.
The table below shows areas where missing fillet sealing is allowed.
Resealing procedures should be performed as quickly as possible;
some high speed tape may be required until sealant is replaced.
[1] EXCEPT FOR ITEMS 7 AND 8
Source: SRM 51-10-01
Mismatched Doors and Panels
52
REVISION 4
GP-145/1536
Doors, windows and access panels should always be installed flush
with the skin. The same should occur around all kinds of joints to avoid
steps, which contribute to increased drag and fuel consumption.
During airplane aerodynamic inspection, the lines where the doors,
windows and access panels meet the fuselage should be observed for
flushness.
GENERAL
PUBLICATION
FUEL CONSERVATION
Specifically for the main and service doors, there is a special
recommendation. When the door flushness is checked on the ground,
it is recommended that the door is adjusted with a negative step of
around 2 mm inside the fuselage. That is necessary to guarantee the
flushness after fuselage pressurization.
EXAMPLE OF TYPICAL STEP AROUND DOORS AND ACCESS
PANELS
Some simple actions during inspection of the airplane fuselage may
help to identify steps around doors, panels and windows. It is
recommended to include this practice during line maintenance checks.
Recommendations:
Access panels should always be installed flush with the skin.
Ensure all access panels are installed in a fair condition,
ensuring smooth flow over the edges of the access panel and
all doors, joints, windows, etc. Ensure that seals are correctly
installed and in airworthy condition.
Source: IATA - FUEL CONSERVATION THROUGH AIRCRAFT MAINTENANCE, 2000
GP-145/1536
The following table shows the estimated extra fuel cost due to
mismatched doors in the ERJ145 airplane family, also indicating
appropriate maintenance references (preventive / corrective actions)
for minimizing this issue. Percentage of trip fuel increase and extra
fuel cost are based on the defined Typical Operational Profile. The
extra fuel cost is calculated for one airplane for one year period.
REVISION 4
53
FUEL CONSERVATION
GENERAL
PUBLICATION
FUEL PENALTY
MISMATCHED
DOOR
APU access
door
Main landing
gear door
(auxiliary)
ESTIMATED
COST OF
PREVENTIVE
ACTION
(US$)
TRIP
FUEL
INCRE
ASE
(%)
EXTRA
FUEL
COST
(US$/ACFT/
YEAR)
0.04
900
52-40-04-400- 801
A Tail Cone Access
Door - Installation
50
450
32-10-07-400-801-A
Auxiliary Door
Assembly of the Main
Landing Gear Installation
250
32-10-06-400-801-A
Main Door Assembly of
the Main Landing Gear
- Installation
300
0.02
MAINTENANCE
ACTION
(AMM REFERENCE)
Main landing
gear door
(main)
0.02
450
Nose landing
gear door
0.05
1,100
32-20-05-400-801-A
Door of the Nose
Landing Gear Installation
200
1,100
52-44-01-820-801-A
Rear ElectronicCompartment Door Adjustment
100
2,800
52-31-00-700-801-A
Baggage-Door
Actuating and Locking
Mechanism Operational
Test/Adjustment
400
6,300
52-18-00-820-806-A
Main Door-to-Fuselage
Skin Gap – Adjustment
52-18-00-820-807-A
Main Door-to-Fuselage
Skin Step - Adjustment
500
Rear electronic
compartment
access door
Cargo door
Main door
0.05
0.12
0.27
54
REVISION 4
GP-145/1536
NOTE: Fuel penalty estimative is derived from theoretical calculations.
GENERAL
PUBLICATION
FUEL CONSERVATION
Missing Door Seal Section
A missing door seal can be responsible for air leak that causes
disturbances in the external air flow and also has to be compensated
for by an increase in engine compressor air bleed, thus increasing fuel
consumption.
Recommendations:
Damaged seals allow air to leak out and may cause disrupted
air flow along the fuselage;
It is important to review pilot reports for cabin and cargo door
complaints. Inspect all doors for optimum fit and fair
condition. Ensure door seals integrity. Eliminate any sources
of pressure leaks;
The inspection for door seals should be done with the door
opened, looking for seal damage. The same inspection could
be done with the door closed, just to analyze dirt on the
fuselage.
Source: IATA - FUEL CONSERVATION THROUGH AIRCRAFT MAINTENANCE, 2000
Skin Dents and Waviness
− Skin Dents:
Skin dents are damage on the fuselage or on other external
surfaces. As all other aerodynamic deterioration, they cause drag
increase resulting in extra fuel burn.
−
GP-145/1536
Aerodynamic Surface Waviness - Critical and Non critical
Areas:
Skin sheet waviness is defined as the ratio of height (H) to length
(L) shown in the following figure.
REVISION 4
55
FUEL CONSERVATION
GENERAL
PUBLICATION
56
REVISION 4
GP-145/1536
TYPES OF WAVINESS
GENERAL
PUBLICATION
FUEL CONSERVATION
The waviness height (H) is the greater deviation from the loft line.
The waviness length (L) is the greatest distance between the
points that limit the wave extension. The waviness height (H) is a
function of the waviness length (L) and should be measured
perpendicularly to the loft line, at the measurement point. The
waviness aerodynamic smoothness requirements should comply
with the chart shown in the following figure.
ALLOWABLE HEIGHTS FOR WAVES
Source: SRM 51-10-01
Recommendations:
Simple dents can cause a fuel penalty which are not costly in
terms of fuel consumption however are very expensive to
repair.
If the dent or waviness is within the Structural Repair Manual
tolerances, no action is necessary just for aerodynamic
reasons.
Perform a regular preventive inspection on critical areas and
evaluation of cost and benefits for repair of a dent or waviness
in non-critical areas.
GP-145/1536
Source: IATA - FUEL CONSERVATION THROUGH AIRCRAFT MAINTENANCE, 2000
REVISION 4
57
FUEL CONSERVATION
GENERAL
PUBLICATION
Skin roughness
Skin roughness such as waviness, gaps, deteriorated paint / decals
and rough surface may cause a significant fuel penalty, besides
damage the airline’s commercial image.
− Surface Roughness - Critical and Non critical Areas:
The surface roughness is related to the depth of the grooves and
the size of grains on the surface, depending on the surface
finishing operation. The maximum acceptable surface roughness
for each aerodynamic smoothness area is specified in table below:
AREA
IB - Critical
II – Non-Critical
Wing Leading Edge
Horizontal Stabilizer Leading
Edge
Nacelle Inlet Duct
MAXIMUM ROUGHNESS
(Ra) [1]
3.2 µm (126 µin)
5 µm (200 µin)
10 µm (400 µin) [2]
[1] RA (ARITHMETICAL AVERAGE DEVIATION) IS THE AVERAGE OF THE ORDINATE
ABSOLUTE VALUES OF EFFECTIVE PROFILE IN RELATION TO THE CENTER LINE, IN A
SAMPLING LENGTH (CUTOFF). USE MINIMUM SAMPLING LENGTH (CUTOFF) OF 2.5 mm (0.10
in).
[2] MAXIMUM ACCEPTABLE ROUGHNESS FOR EROSION-AFFECTED AREA. THE MAXIMUM
AFFECTED AREA IS LIMITED TO 10% OF THE ZONE AREA (SEE AMM 6-30-00/1, FOR THE
ZONE AREA).
To measure the roughness use a roughness meter, as available, or
compare with sandpaper grit according to the table below of
Roughness & Sandpaper Grit:
58
SANDPAPER GRIT
220
320
REVISION 4
GP-145/1536
ROUGHNESS
10 µm (400 µin)
5 µm (200 µin)
GENERAL
PUBLICATION
FUEL CONSERVATION
Recommendations:
Any rough surfaces must be identified and returned to a
smooth condition. Any discrepancies caused by hydraulic or
fuel leaks must be corrected;
Ensure that flaps are not dented or damage. Rough surfaces
alone will increase drag;
Inspect all control surface for maximized fit and fair positions.
Ensure correct flush fasteners are installed on all surface.
Rough surfaces from any leaks must be corrected;
Inspect all areas of the aircraft for both hydraulic and fuel
leaks that can degrade surface finish. Rectify leak areas and
return surface finish to specification;
Inspect drain systems. Eliminate any source of leaks and
ensure surface integrity of surfaces affected;
Inspect cockpit windshield to ensure best fit and fair with the
fuselage nose section structure. Any uncured sealant that may
have migrated from the sealed area must be removed and the
surface area cleaned;
An aircraft wash and polish program can produce clean
smooth airflows over the surfaces enhancing fuel burn
figures;
Particles and fluid leaks adhering to aircraft skin contribute to
drag. Frequently aircraft washing is beneficial.
Investigate all reported fuel quantity discrepancies, ensuring
that problems possibly related to contaminated probes are
eliminated.
GP-145/1536
Source: IATA - FUEL CONSERVATION THROUGH AIRCRAFT MAINTENANCE, 2000
REVISION 4
59
FUEL CONSERVATION
GENERAL
PUBLICATION
External Repairs
External damages, especially in the aerodynamically critical areas,
induce an increase drag. It is normally difficult to replace an external
patch by an internal one, but if access has already been gained during
an inspection, installing an internal patch could be preferable, since it
also has less impact on an airline’s commercial image.
Recommendations:
Wherever possible try to install an internal patch repair
instead of an external one;
When possible, replace external repairs with internal ones.
Wherever possible, use the aerodynamically ideal fastener, as
recommended by SRM or EMBRAER engineering.
External Dirt accumulation
Dirt accumulation along an airplane’s external surface removes energy
from the boundary layer airflow, increasing friction drag and thus
increasing fuel consumption.
A very dirty airplane is estimated to produce a decrease of
approximately 0.1% in specific range. Also the same magnitude of
degradation is expected for bad surface conditions, such as lack of
consistent paint or different roughness.
Regular cleaning, polishing and washing require only few hours of
maintenance work, and are far cheaper when compared with the
impact of having a dirty airplane throughout the year.
Recommendations:
An aircraft wash and polish program can produce clean
smooth airflows over the surfaces enhancing fuel burn
figures.
Source: IATA - FUEL CONSERVATION THROUGH AIRCRAFT MAINTENANCE, 2000
60
REVISION 4
GP-145/1536
Consider that, for the ERJ135/145 Family, drag increments due to
missing parts are small when compared with other sources. Isolated,
they mean much less than 1% in trip fuel increment. Dirt increments
play a more important role in total drag, as well as surface mismatches
and air leaks.
GENERAL
PUBLICATION
FUEL CONSERVATION
Extra Weight
Extra weight may be accumulated in an airplane during its life cycle
due to several aspects such as external and internal dirt accumulation,
extra paint layers, interior moisture accumulated and many others.
This increases the airplane Operating Empty Weight (OEW) and also
increases fuel consumption while reducing payload capacity.
FUEL PENALTY
EXTRA (KG)
50
80
100
150
200
TRIP FUEL
INCREASE (%)
0.14
0.22
0.27
0.42
0.56
EXTRA FUEL COST
(US$/ ACFT/ YEAR)
3,300
5,200
6,500
10,700
13,100
The effect of weight increase on airplane fuel consumption is
presented on Section II – Flight Operations and Performance, OEW
Increase and Control.
GP-145/1536
Interior and Exterior Dirt Accumulation
The accumulation of dirt in the interior of the airplane may lead to a
significant increase of weight.
Regular interior cleaning during line and heavy maintenance
operations to clean up and remove debris from airplane interior
(mainly below floor and compartments) is a good practice to avoid
excessive increase of weight, thus contributing to reduced fuel
consumption.
On the exterior side dirt accumulation on airplane surfaces may be
caused by dust, debris residues of fluids, drains, runway
contamination and others. While affecting aerodynamically the
performance of the airplane, that also represents some extra
weight, and contribute to increase fuel consumption. Periodical
washing and exterior cleaning of the airplane is a recommended
practice whenever visible dirt has accumulated on the airplane.
REVISION 4
61
FUEL CONSERVATION
GENERAL
PUBLICATION
Paint
Additional paint layers increase airplane weight and make the
surface less smooth due to paint steps. Upon repainting an
airplane, whenever possible it’s recommended to remove the
current paint layer and prepare the surface adequately to receive a
new layer. This will prevent unnecessary airplane weight and
provide a decreased surface roughness.
For the ERJ145, a typical painting layer of about 75 microns
represents around 80 kg in weight. That may vary depending on
the paint scheme.
Thermoacoustic Insulation
Thermoacoustic insulation used in airplane interiors may
accumulate moisture and dirt during airplane operation,
contributing to increased airplane weight. A recommended practice
could be to perform inspections on insulation blankets, typically
during disassembly of interiors.
As reference, the maintenance manual brings the procedures and
recommendations to inspect and clean insulation blankets as per
AMM TASK 25-81-01-300-801-A Thermoacoustic Insulation Pads
– Repair.
Recommendations:
62
REVISION 4
GP-145/1536
Regular review of aircraft Empty Weight does pay dividends.
Aircraft have been known to increase by as much as 1000
pounds in a 5 year period.
GENERAL
PUBLICATION
FUEL CONSERVATION
AIRPLANE SYSTEMS
FLIGHT CONTROLS - RIGGING OF CONTROL SURFACES
Out-of-rig flight control surfaces cause additional drag and may induce
other surfaces to deploy partially, causing even more drag
(reproductive drag).
Out-of-rig flight control surfaces incur one of the biggest fuel penalties,
while the cost of corrective action may be trivial.
In the table below, the most common instances of out-of-rig control
surfaces are presented along with their respective impact on fuel
consumption. The appropriate inspection and corrective maintenance
actions are presented as well. Percentage of trip fuel increase and
extra fuel cost are based on the defined Typical Operational Profile.
The extra fuel cost is calculated for one airplane for one year period:
FUEL PENALTY
OUT-OF-RIG
ISSUES
Flaps not fully
retracted
(1°)
Flap mis-trim
(1°)
Speed brake
partially
extended
(1/2 in)
Ground spoiler
partially
extended
(1/2 in)
Aileron mis-trim
(1°)
TRIP FUEL
INCREASE
(%)
EXTRA
FUEL COST
(US$/ACFT/
YEAR)
1.98
46,000
0.99
23,000
0.07
1,600
0.07
0.17
1,600
3,900
MAINTENANCE
REFERENCE
ESTIMATED
CORRECTIVE
ACTION
(US$)
27-50-00-700801-A
Inboard and
Outboard Flaps
- Deflections
100
27-63-01-700802-A
Spoiler Surface
- Adjustment
250
27-10-00-700801-A
Aileron
Adjustment and
Check
100
GP-145/1536
NOTE: All data derived from theoretical calculations.
REVISION 4
63
FUEL CONSERVATION
GENERAL
PUBLICATION
For example, one flap not fully retracted by 1° and with mis-trim of 1
degree, leads to more than US$ 65,000 penalty per airplane per year.
Nevertheless, a corrective action may cost approximately US$ 100.
Recommendations:
Inspect frequently for aileron rigging that may create
unnecessary drag;
Inspect for spoiler control rigging. Spoilers are a full time
control parameter. So, ensuring better than nominal rigging
enhances performance;
Inspect the flap system rigging for optimum position. These
large surfaces are designed to manage flight regime attitudes
at controlled speeds. Out of tolerance situations will cause
extra fuel burn;
Inspect the rudder control system for optimum rig.
Source: IATA - FUEL CONSERVATION THROUGH AIRCRAFT MAINTENANCE, 2000
AIRSPEED INDICATION ACCURACY
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REVISION 4
GP-145/1536
Instrumentation accuracy, mainly airspeed indication, is an important
component of the fuel saving. Some small deficiencies in airspeed
indication may not be detected by instruments, it will depend on the
precision and kind of equipment, but keeping instrumentation
calibrated to established tolerances will eliminate unproductive effort.
Speed measuring equipment (airspeed indicator) has a big impact on
fuel consumption. With inaccurate indications, one can fly faster or
slower than actual target speed. For example, if the instrument is
indicating slower speeds than actual, the airplane will fly faster than
necessary, leading to unnecessary extra fuel burn.
The following table presents the annual extra cost per airplane. It is
observed that flying 2% faster than planned cruise speed may be
caused by inaccurate instrumentation.
GENERAL
PUBLICATION
FUEL CONSERVATION
FUEL PENALTY
AIRPLANE
ERJ135
ERJ145
TRIP FUEL
INCREASE
(%)
0.7
0.5
EXTRA kg /
ACFT/ YEAR
EXTRA FUEL
COST (US$)/
ACFT/ YEAR
22000
11800
21,800
11,700
The maintenance action to ensure proper calibration of airspeed
indication is described in the functional check of Air Data System in
the Airplane Maintenance Manual – AMM 34-15-00-700-801-A.
Recommendations:
Ensure regular instrument calibration checks to maintain
calibration of airspeed systems. Plugging or deforming the
holes in the alternate static port can result in erroneous
instrument readings in the flight deck. Keeping the circled
area smooth and clean promotes aerodynamic efficiency.
Maintenance operations must ensure the use of proper tooling
to block the static ports.
Source: IATA - FUEL CONSERVATION THROUGH AIRCRAFT MAINTENANCE, 2000
ENVIRONMENTAL AND PNEUMATICS
The ERJ135/145 Family environmental and pneumatic systems
operation and maintenance also have significant impact on fuel
consumption.
Every event that produces higher thermodynamic loads on the packs,
or a higher than normal pressurization air demand, will also require
higher bleed air extraction from the engines. Higher bleed
requirements mean more fuel consumption.
Maintenance factors that affect the Environmental Control System:
−
GP-145/1536
−
Leaks that result in excessive bleed air requirements from
engines;
Component failure and dispatch, that forces the airplane to fly
at lower altitudes where fuel consumption is higher.
REVISION 4
65
FUEL CONSERVATION
GENERAL
PUBLICATION
Leaks
Fuel burn is increased if there are pneumatic system leaks and cabin
air leaks. Costly pneumatic leaks can occur at different locations.
Manifolds, ducts and duct flanges, worn connector seals and valves
are susceptible to leaks, and the fuel penalty for such a waste will
depend on the areas in which they occur, the magnitude of the loss,
the pressure supplied, and the size of the ducting/device.
Overboard leakages of pressurized compartments incur penalties not
only due to the unnecessary loss of bleed pressure, but also due to
the disruption of external airflow. Damage to door seals is the major
contributor in this case, sometimes requiring repair.
ELECTRICAL POWER
Operation of the ERJ135/145 Family electrical system and its
maintenance also has an impact on fuel consumption.
During a flight, considering normal operations, thermal energy from
fuel is converted into electrical energy through engine-driven
generators powered by the engines accessory gearbox.
The higher the electrical loads required for the airplane during a flight,
the more energy it will tap in the form of fuel. More fuel is then
necessary in order to supply the increased electrical demand.
How much fuel does the engine driven generators require to deliver
1kWh to the electrical system?
Assumptions:
−
−
−
Each 1 kg (2 lb) of JET A1 fuel potentially has 6587 kJ of
energy that is equivalent to 1.8291 kWh;
The generators average efficiency is 70%;
Other losses along the distribution system (such as heat,
radiation, inductance, etc.) are estimated to be roughly 50%.
66
REVISION 4
GP-145/1536
Consequently, 0.6404 kWh is effectively delivered to the electrical
system by burning 1 kg (2 lb) of fuel, when using the generators.
GENERAL
PUBLICATION
FUEL CONSERVATION
Considering the average fuel price of US$ 3,00/Gal (or US$ 0,99/kg,
fuel density @ 0.803 kg/l), we can conclude that:
One Hour of generator connected to the electrical system
means:
1.56 kg (3.44 lb) of fuel or US$ 1.54 per each 1 Kw required by
the electrical loads.
IN-FLIGHT OPERATIONS
In-flight electrical loads are a function of:
−
−
Flight Profile.
Operational practices and airline policy.
Flight profile loads are the ones necessary to accomplish normal or
abnormal operations for each flight phase. They are necessary and
shall not be reduced unless required by operational procedures in the
AOM or QRH.
Crew operational practices should be to turn off unnecessary loads.
They are often defined by airline policy and training. Some examples
are:
−
−
−
−
Galley area loads: coffee makers, ovens and lighting.
Passenger cabin lighting during night flights.
Instrument lighting in daylight operation.
Unnecessary use of radar.
GP-145/1536
Each operator shall evaluate which loads may be turned off during a
flight according to their operational profile.
REVISION 4
67
FUEL CONSERVATION
GENERAL
PUBLICATION
ELECTRICAL LOADS
POWER CONSUMPTION
ITEM
(kWh)
Galley Area Lights
0.37
Galley Oven (1 unit)
1.60
Galley G3 Hot Jug (1 unit)
0.27
Courtesy/Stairs Lights
0.18
Ceiling Lights
0.37
Sidewall lights
0.70
Reading Lights
0.24
Cockpit Main Panel Lighting
0.29
Cockpit Flood/Storm Lights
0.18
Cockpit Overhead Panel Lighting
0.19
Wing Inspection Lights
0.30
Logo Lights
0.30
Taxi Light
0.90
Landing Lights (LDG 1+ 2 +
1.50
NOSE)
Windshield Wiper
0.56
Weather Radar / Antenna
0.12
Coffee Maker (1 unit)
0.42
Coffee Brewer (1 unit)
1.20
TOTAL
9.69
The reduction of 2 kWh on electrical loads will represent a saving of
approximately 3 kg (6.7 lb) of fuel or US$ 3.00 per hour of use, when
using generators power.
If considering the Typical Operational Profile:
68
REVISION 4
GP-145/1536
2 kWh reduction on in-flight electrical loads means:
5700 kg (12566 lb) of Fuel ~ US$ 5,600
(per acft/ per year)
GENERAL
PUBLICATION
FUEL CONSERVATION
Recommendations:
To summarize, among other methods, optimization of
electrical power usage is an efficient means of saving fuel.
Airlines should adapt their policies and practices to reduce or
eliminate superfluous loads. While on the ground, alternative
means of generating electricity for the airplane, such as GPU,
should be preferred, in view of its lower costs when compared
to APU use.
POWER PLANT
Engine
This chapter contains the tips and recommendations provided by
Rolls-Royce regarding the operation of the AE3007 series engines.
Jet engines are turbo machines, subjected to high internal
temperatures and pressures. Engine wear is accelerated and life
shortened as internal temperatures and the time operating at those
temperatures increases. How the engine is operated in each phase of
the mission will affect its rate of deterioration.
The following pages include guidelines to economical operation for the
Operator to consider in their flight planning.
Key Notes
Operators should contact Rolls-Royce directly with specific questions
on the engine on-wing life and hardware degradation affects of
proposed Flight Operation changes for fuel savings, as well as for any
clarifications to ensure that the proposed Flight Operation changes for
fuel savings will be in compliance with the terms of their agreement(s)
with Rolls-Royce concerning engine services.
Engine operation must comply with approved flight operation
procedures.
General Rule
GP-145/1536
Reducing the engine thrust setting whenever possible will generally
decrease fuel consumption, increase the engine on-wing life, and
reduce engine hardware degradation.
REVISION 4
69
FUEL CONSERVATION
GENERAL
PUBLICATION
Takeoff
Use of the Alternate Takeoff setting is recommended, as engine
onwing life increases and hardware degradation decreases with
reduced engine thrust settings.
Cruise
Reducing Cruise speeds will result in fuel savings. Engine on-wing life
and hardware degradation will be improved with the reduced engine
thrust required for lower Cruise speeds.
Descent
Descents completed with engines in Flight Idle will result in fuel
savings.
Ramp Operations
Completing Ramp Operations with a single engine running provides
significant fuel savings compared to using two engines. There will be
negligible impact on the engine on-wing life and hardware degradation
by using a single engine. There are some operational limitations that
do not allow single engine operation under all conditions.
Maintenance Actions
Periodic engine water-washing and compressor bleed valve system
maintenance may result in fuel savings. Operators should contact
Rolls-Royce directly with specific questions on Maintenance Actions
for fuel savings.
Recommendations:
On wing engine washing can address dirt accumulation within
the compressor. Leakage caused by the bleed air system can
be remedied by on wing engine bleed rigging and additionally
provide up to 2.5% Specific Fuel Consumption (SFC) benefit.
Regular on – wing engine washing can bring as a 1.5% SFC
improvement.
70
REVISION 4
GP-145/1536
Source: IATA - FUEL CONSERVATION THROUGH AIRCRAFT MAINTENANCE, 2000
GENERAL
PUBLICATION
FUEL CONSERVATION
Thrust Reverser
Out-of-rigging Thrust reverser doors cause steps and additional drag,
causing increase of fuel consumption.
In the table below, the issues of out-of-rigging in thrust reverser doors
are presented and their respective impact on fuel consumption. The
appropriate inspection and corrective maintenance actions are
presented as well. Percentage of trip fuel increase and extra fuel cost
are based on the defined Typical Operational Profile. The extra fuel
cost is calculated for one aircraft for one year period:
FUEL PENALTY
OUT-OFRIG
ISSUES
0.16
3,700
0.06
MAINTENANCE
REFERENCE
ESTIMATED
CORRECTIVE
ACTION
(US$)
78-31-01-820-801-A
Thrust Reverser Rigging Procedure
600
1,400
GP-145/1536
Engine
thrust
reverser
door
(1/4 in or
protruding)
Engine
thrust
reverser
door
(1/4 in
recessed)
TRIP FUEL
INCREASE
(%)
EXTRA
FUEL COST
(US$/ACFT/
YEAR)
REVISION 4
71
FUEL CONSERVATION
GENERAL
PUBLICATION
SERVICE BULLETINS
SB
Description
Reason
SB 145-21-0023
AIR CONDITIONING MODIFICATION TO THE LOGIC
OF AIR CONDITIONING
AUGMENTED MODE
Reduction of fuel
consumption due to
reduction of bleed air
required by air
conditioning in certain
circumstances.
SB 145-73-0027
ENGINE FUEL AND CONTROL NEW FADEC WITH SOFTWARE
VERSION B8.0 FOR THE
AE 3007A1P ENGINE
Enhancement of engine
operations performance
will contribute to reduce
fuel consumption.
SB 145-73-0028
ENGINE FUEL AND CONTROL NEW FADEC WITH SOFTWARE
VERSION B8.0 FOR THE
AE 3007A1E ENGINE
Enhancement of engine
operations performance
will contribute to reduce
fuel consumption.
SB 145-73-0029
ENGINE FUEL AND CONTROL NEW FADEC WITH SOFTWARE
VERSION B8.0 FOR THE
AE 3007A1 ENGINE
Enhancement of engine
operations performance
will contribute to reduce
fuel consumption.
SB 145-73-0031
ENGINE FUEL AND CONTROL NEW FADEC WITH SOFTWARE
VERSION B8.0 FOR THE
AE 3007A1/3 ENGINE
Enhancement of engine
operations performance
will contribute to reduce
fuel consumption.
SB 145-52-0013
DOORS - APPLICATION OF
POLYURETHANE FILM ALONG
THE CONTOUR OF THE NOSE
AND MAIN LANDING GEAR
DOORS
Avoidance of delamination
in the contour of the nose
and main landing gear
doors. Delamination
affects aerodynamic
performance (increase
drag) and increase fuel
consumption.
SB 145-53-0009
FUSELAGE - APPLICATION OF
EROSION RESISTENT
POLYURETHANE FILM ON
RADOME AND ON ELECTRONIC
COMPARTMENT, PACK AIR,
HYDRAULIC COMPARTMENT
NACA AIR INTAKES
Avoidance of abrasion /
erosion of the composite
material of radome.
Surface roughness in
critical areas increase fuel
consumption.
72
REVISION 4
GP-145/1536
Some modifications of the airplane may increase or reduce fuel
consumption depending on the modification itself. The table below
shows some examples of service bulletins that can contribute to
reduced fuel consumption.
GENERAL
PUBLICATION
FUEL CONSERVATION
A defined process of Service Bulletin (SB) or Modification evaluation
for voluntary incorporation of items can play a role in the cost/benefit
proposition affecting fleet economics. Even incorporation of the most
desirable item can add weight to the airplane or affect fuel
consumption positively or negatively.
The overall analysis for incorporation of a service bulletin,
besides all technical aspects, should nowadays also include
implications on fuel consumption, either by reducing it or
increasing due to extra equipments, loads, weight and others.
EFFECTS OF CRUISE SPEED SELECTION ON DIRECT
MAINTENANCE COST
EFFECTS OF SELECTING LOWER CRUISE SPEEDS ON THE
DIRECT MAINTENANCE EXPENSES
GP-145/1536
The selection of lower cruise speeds during flight is one of the
suggested operational practices that may contribute to fuel savings, as
described previously in this document.
This practice, while reducing fuel consumption, increases trip time
and, therefore, the accumulation of flight hours, over a period of time
considering that the original flight schedule (flights per day) is
maintained. Consequently, by accumulating more flight hours, the
direct maintenance expense* will increase.
The following chart shows the relationship between the trip time
increase (flying with reduced cruise speeds) and the increase of direct
maintenance expenses* for the ERJ135/145 airplane.
REVISION 4
73
Direct Maintenance Expenses
Increase (%)
FUEL CONSERVATION
GENERAL
PUBLICATION
7%
6%
5%
4%
3%
2%
1%
0%
0%
2%
4%
6%
8%
10%
12%
14%
16%
Trip Time Increase (%)
In the chart above, the operator has to use the average trip time
increase as input (obtained from the airline operations engineering
analysis) and verify the relative increase in direct maintenance
expenses*. To calculate the final figures, the operator has to know
their own actual direct maintenance expenses*, over which the relative
increase (in percentage) should be applied.
Example:
Evaluation of overall impact of reducing cruise speed, flying LRC
instead of M0.78, considering fuel savings and maintenance
expenses.
Assumptions:
Speed Selection: Flying LRC instead of M0.78 in cruise.
Flight profile: Standard flight profile assumed in this document.
Airplane: ERJ145.
Flight Operations Engineering evaluation:
74
REVISION 4
GP-145/1536
Trip time increase: 4% (F.O. engineering calculation).
Trip fuel impact: -1.5% (F.O. engineering calculation).
Fuel Cost savings: US$ 35,000.00 per acft/year.
GENERAL
PUBLICATION
FUEL CONSERVATION
Maintenance evaluation:
Direct maintenance expenses*: US$ 700,000.00 per acft / year
(airline data).
Direct Maintenance Expenses* increase: 1.4% (from the chart,
with 4% of trip time increase).
Direct Maintenance Expenses* increase: US$ 9,800.00 per acft /
year.
(*) Direct Maintenance Expenses are considered as “those
maintenance labor and material expenses directly used in
performing maintenance on an item or airplane.” The direct
expenses does not include indirect maintenance labor and
material expenditures which contribute to the overall
maintenance operations, line station servicing, administration,
engineering, record keeping, supervision, tooling, test
equipment, facilities, etc.
Conclusion:
GP-145/1536
Comparing the fuel cost savings with the direct maintenance
expense increase, it's possible to verify and conclude that in fact
there is a positive benefit of flying LRC instead of M0.78, bringing
overall savings for the company of around US$ 25,000.00 per
airplane per year, using the figures simulated here.
The operator could perform the same evaluation considering its typical
flight profile and actual maintenance expenses. In order to perform a
complete evaluation on the trade-off between fuel savings and
increase in flight time, it is important to understand all costs based on
time, and the direct maintenance cost is very important one. Other
examples are flight crew and cabin crew costs.
Important: The assumptions and figures presented in the example
above are used to help in understanding the concepts and the
evaluation performed. The figures have illustrative purposes only and
operators cannot use them as reference for their particular evaluation
of fuel cost savings and maintenance expense considerations. Airlines
have to perform such evaluation based on their actual flight profile,
fleet utilization and maintenance expenses.
REVISION 4
75
FUEL CONSERVATION
GENERAL
PUBLICATION
SECTION IV − CONCLUSIONS
76
REVISION 4
GP-145/1536
Worldwide, profit margins have been reduced over the years due to
intense competition among airline companies. Careless operation
without the proper attention to factors affecting operating costs can
quickly reduce profit margin.
“Long term” is the key factor to success and the investment in the fleet
must pay off over a certain period. Any difference in operating costs
becomes huge over “a number of years”.
The numbers shown in this publication are surprising. We believe that
they will impress any manager interested in making his airline
profitable. They show how important attention to detail can be to
prevent significant unnecessary costs in the long term.
Fuel saving is the sum of small contributions that seem to be
insignificant when considered separately, but are considerable when
integrated over the years.
A successful Fuel Conservation Program established by an airline is
only effective when all related areas (Maintenance, Flight Crews and
Flight Operations Engineering) work together and are fully aware that
even small tasks and actions might have a significant impact on fuel
savings.
As a best practice, some airlines periodically, implement job rotations
between maintenance and operational management. The main
objective for this action is to avoid some erroneous concerns and to
share knowledge about how some action taken by one department
can affect other. Working “cross functionally” makes it possible to see
that some actions seemingly beneficial from one department’s
perspective can negatively affect the other department and overall
company results.