Radio-Instruments
Basics
NDB
Propagation
300.000 km / s
162,000 NM / s
1 NM / 6.17 ms
Antenna
Simplest one: dipole antenna.
Wave length
300/MHz = Wavelength (m)
Frequency
300/Wavelength (m) = Frequency(MHz)
Frequencies:
190 – 1750 kHz
most common: 250 – 450 kHz
two types
NDB L
NDB E Airport / Airways A2A
Coast A1A
cone of confusion: 50°
VOR
Letter code:
3 Letter → Enroute NDB
2 letter → Locator for ILS
(ILS Code: i + 2 letter of NDB)
Range:
En-route: 50-100NM
Locator: 10-25 NM
Homing / Holding: 50NM
ADF
Use:
first turn in ANT to hear the IDENT
if hear IDENT switch to ADF
if no → switch to BFO
if u hear IDENT switch to ADF
if not → fuck off it's an thunderstorm
Errors
Quadrantal error (highest at bearing of 45°,135°,225°,315°)
night effect
Mountain effect
Coastal refraction
no failure warning
Frequencies
108.00 to 117.95 MHz spacing 50 kHz
108.00 to 112.00 MHz
→
Terminal Range 50 NM
share with ILS
ILS use the “odd” numbers at
first decimal figure
112.00 to 117.95 MHz
→
en-route Range 200NM at 25.000 ft
Cone of confusion: 40°
Radio-waves
pic 3.6
2 Signals
same frequency but one FM and on AM
first signal is the reference
second signal sends an different signal ever 1° around the
VOR. The receiver compare both and determine the radial
ILS
Errors
Scalloping → fading cause by reflection of the signal
Aircraft error due to deviation
all errors together not more than 5% in DOC
designate operation coverage
Definition
Pilot interpreted runway approach aid
descending to decision altitude than make a visual flight
landing → no auto-landing
no ground assistance required once established
pic 4.1
Categories
Device performance categories
CAT I
provides accurate guidance information from coverage limit
down to 200ft
CAT II
provides accurate guidance information from coverage limit
down to 50ft or less above horizontal plane containing runway
threshold
CAT III
provides accurate guidance information from coverage limit
down to 0 ft and along surface of the runway
Operational performance categories
CAT I → DH 200ft / RVR 550m
CAT II → DH 100ft / RVR 300m
CAT IIIA → DH <100ft / RVR 200m
CAT IIIB → DH <50ft / RVR 75m
CAT IIIC → no limits (full auto-landing)
Components Ground
Localiser transmitter
localiser signal (VHF)
carrier-wave between 108.00 – 111.95
AM 90 Hz and 150 Hz
coverage 8° to both sides to 10NM forward
pic 4.3/ pic 4.7
transmitter situated around 300m from the upwind end of
runway
Glide path transmitter (UHF)
carrier-wave connected with localiser freq.
Again modulated 90Hz and 150Hz
coverage depends on the glidepath:
0.45 above surface and 1.75
pic 4.4/ pic 4.7
marker beacons → Range checkpoints
Components in aircraft
ILS Indicator
All dots represent 1° to each side so if 2 dots than every dot is
0.5°
full deflection up / down → 0.7° of glideslope6
Listen to the IDENT – Thunderstorms don't send IDENTs
pic 5.1
MLS
Marker beacons
For the range during an ILS approach
CAT I → 2 beacons
CAT II / III → 3 beacons
up to 3000ft
Frequency 75 MHz
pic 4.2
DME
Distance measurement equipment
adjusted to be zero at touchdown
one DME perhaps serve several runways
Limitations
Signal co-reception causing “scalloping”
unpredictable bending of beam
Ground effect restricts use in mountains
large permanent fixtures for each RW
low rate of landing and restricted vehicle movement (to avoid to
much metal in the signal)
only 40 channels
Difference ILS → MLS
ILS
MLS
Fix approach path
Free choice
Allows curved approach
Single Aircraft
approach
Coverage
Multiple approach
Horizontal +- 40°
Vertical 0.9°- 20°
20NM (sometimes: 30NM)to 20,000ft → allows steeper
approaches
in this range the Signal to Noise Ratio has to be 3:1
Principle
Time Referenced Scanning Beam (TRSB)
narrow beam scan the airspace (two seperated transmitter, but
in one caseing)
additional a DME/Precision 12 times better than a normal DME
the system told the aircraft where it is in space and the aircraft
create its own glidepath
Frequency
5031 – 5091 MHz (SHF) 200 channel, 300kHz spacing
Preamble
First Information send from System to the aircraft:
IDENT
Azimuth offset and distance from threshold
Equipment performance level
Azimuth and elevation beam with
DME/P distance offset and channel
Elevation height offset an distance from threshold
Limitations
Obstacle etc. still a problem
but no restrictions in the sitting of the transmitter.
RADAR
Advantages
Higher accuracy and higher reliability
High capacity (more runways than ILS)
Freedom to choose sitting
more available channels
Wide 3-D coverage
More efficient in terminal areas
Higher traffic density allowable
Different Types
RADAR: Radio Detection and Ranging
Primary radar
Energy reflecting by a target (e.g. Aircraft)
all power from Tx
secondary radar
Target replies to an interrogation
Power shared by both
important: 6.17µs/NM
DME
Function:
Secondary radar system
aircraft transmit an “request” with a random “train” of pulse
pairs and starts timing. Pules are 12µs appart
starts with 150pules/sec
after 15,000 pules/sec down to 60pps
when lock on DME than 25-30 pps
Groundstation: send exactly this train of signals back to the
aircraft. With a 50µs delay and +- 63MHz
962 – 1213 MHz → 252 Channels
126 X-Channels + 126 Y-Channels
X-Channels 1-63 low Band
Aircraft trans. 1025 – 1087 MHz
Ground repl. 962 – 1024 MHz (-63MHz)
X-Channels 64-126 High Band
Aircraft trans. 1088 – 1150 MHz
Ground repl. 1151 – 1213 MHz (+63MHz)
Y-Channels change aircraft freq. To Ground and Ground to
Aircraft
DME provides slant range (line of sight)
Slant range error is only significant when aircraft range < 3x
aircraft heigh
Co-located with VOR
Only when:
Approach aid: 30m / 100ft
enroute: 600m/ 2000ft
IDENT: 4 Times the VOR Ident → 3 times normal 4th slightly
higher than the other.
Airborne equipment:
interrogator and indicator
omnidirectional blade antenna
limitations:
saturated (service only provide to 100 aircrafts)
after Saturated cut off the 30 weakest aircraft down to 70 in
service)
range exceeded
Equipment unserviceable
accuracy
Accurate 95%
0.25 NM plus 1.25 % of distance measured(01.01.1987)
0.2nm since 01.01.1989
SSR
information contain: range, bearing, heigh
Secondary surveillance
radar
Interrogation freq. 1030 MHz
directional antenna, Ground
Response Freq. 1090 MHz (+60MHz) omnidirectional antenna,
aircraft. (info also for TCAS)
sending information are framed by F1 and F2 (20.3 µs apart)
and SLS (Side slope suppression signal)
Framing Pulses spaced 20.3µs
12 Pulses can be send in this time → 2^12 → 4096
combinations
Spacing P1 – P2 always fix 2 µs
Spacing P1 – P3 for mode determination
Spacing P1 – P3 → 8 µs for mode A
21 µs for mode C
SLS:
Modes
stronger than all side slopes
weaker than the main beam
A+B
Only AC-Ident
C
Height up to 128,000 ft
altimeter send: 100ft
D
Experimental
S
Use for Datalink
much more information can be obtained
24 Bit address → more than 16 million
possibilities
Special squwaks:
1200 general VFR (USA)
7000 general VFR (Germany)
7500 unlawfull interference
7600 radio-failure
7700 trouble in heaven
2000 enter in a transponder area from a non- transpondnecessary area
possible codes 0000 - 7777
Advantages:
less power necessary
hole bunch of information can be send.
No clutter
Disadvantage:
not as accurate as a primary radar
Errors
Garbling – two or more A/C just in line and closer then 1.7 NM
to Ground station
Fruiting – two SSR on same frequency
Relies on reflection of transmitted Electromagnetic Radiation
(EMR)
Primary Radar
use the same antenna for transmission an receive
→ only on function is possible
minimum detection range: pulse length
maximum detection rang: due to power
2x range (send /receive) 16x power is necessary
PRP/I = Pulse recurrence period / interval
time between two pulses = 1/PRF
PRF = Pulse recurrence frequency = Pulses per second = 1/
PRP
maximum unambiguous range:
Range = PRP/12.34µs ( 2 ways → 2*6.17µs/nm)
therefore more power (range) needs a longer bleep → a
greater minimum
1 second = 1,000 milliseconds = 1,000,000 microseconds (µs)
Weather Radar Function
Required
Frequency: 9000MHZ (SHF) Range: 300NM
stabilized on Roll and Pitch axes
Pressurized A/C
non-pressurized A/C >5.700kg
non-pressurized A/C > 9 approaved seats
Two types of RNAV
L NAV (horizontal navigation) correspond with RNP
V NAV (vertical navigation) correspond with RVSM
Area Navigation
(RNAV )
Accuracy
B-RNAV →
P-RNAV →
Basic RNAV (5NM accuracy in 95% / RNP5)
Precision 1NM in 95% / RNP1
(EU Standard requirement above FL200)
RNAV Level
2D
3D
4D
VOR/DME
rho - theta
Electronically move a given/real VOR/DME on the required
track, along a Radial of the VOR/DME
this has to be done before departure (Pilot or OPS)
Horizontal guidance (3 satellites)
like 2D with vertical guidance (4 satellites)
like 3D with a timing function (standard for big A/C)
gives the possibility to track the flight and make a
guess where it will end
this new created Way-point is called phantom Waypoint
Accuracy 5° in 95%
DME/ DME
rho - rho
Rho-rho RNAV
more accurate than VOR DME 1.25% or 0.2NM
best solution for RNAV → therefore standard in aviation
the system choose automatically the 2 best DME (best cut,
not strongest / best signal!!)
Display:
any navigation Display.
HSI → Dots a NM (2 Dot system/10NM → 1 Dot 5NM off
track) Display shows NM to Way-point
GNSS
Global Navigation
Satellite System
GPS Global Positioning System -US (DoD) based on WGS84
GLONASS Global Orbiting Navigation Satellite System –
Russia
Galileo – EU System, no military or government control
available 2017/2018
Augmentation systems
Wide area → WA DGNSS
satellite based augmentation system (SBAS) more accurate
than GNSS less than LGNSS, because the time for sending
the correction via satellite is to long
local area → LA GNSS
ground based augmentation system (GBAS) system, most
accurate system. Direct transmission of the correction to the
receiver. More and more accurate when the receiver moves
towards the transmitter ( time for signal travel will shorten)
DGNSS
differential Global
Navigation Satellite
System
Segments of GPS
GDOP
Geometric dilution of
precession
P DOP → position → H DOP: +-13m /95%
V DOP: +-22m / 95%
T DOP → Time: +- 40ns
Control segment
situated in Colorado Springs
master control station, Monitor station and Ground antenna
Space Segment
24 satellites/ space vehicles
21 + 3 spare
satellites orbites the earth in 12 hours / ½ sidereal day
average height from earth 20200 km
Broadcast on UHF
sending an pseudo-random noise (PRN)
two carrier frequencies L1 and L2
L1 for civil service 1575.42 MHz
L2 only for military service 1227.6 MHz
L1 carrier for C/A code 1023 MHZ and P code (military)
L2 carrier only for P code
Broadcast contains
1. SV position
2. SV clock time
3. SV clock error
4. Information on ionosphere propagation
5. supplementary information
user segment
Receiver →
Sequential – single or dual channel, scan SV one by one
multiplex - single or dual channel move quickly between SV
multichannel best one – monitor several SV simultaneously
GNSS Errors
Services
SPS – standard positioning service using C/A on L1 (civil)
PPS – precise pos. service – only military - code P on L1 + L2
Difference GPS /
GLONASS
GPS - US
6 orbit planes (4 SV)
55° inclination
different signals on common
frequency
GLONASS - Russia
3 orbit planes (8 SV)
65° inclination
one signal on different
frequencies
Ephemies – position of SV on the orbit
SV Clock
Ionospheric Propagation (biggest one)
Tropospheric propagation
receiver noise
multi path reception
GDOP
Aircraft manoeuvre
selective availability → ability to dither the signal
no failure warning → capture that with an additional satellite
US uses 5( 4 normal + 1 checker)
EU uses 6(4 normal + 2 checker)
this called RAIM
Receiver autonomous integrity
monitoring
Radio altimeter Frequencies
Data
4200 MHz – 4400 MHz → centimetric wave length
Sinkrate, height, Aircraft configuration
supply to GPWS, TCAS and automatic landing system
GPWS
Measurement
Frequency modulation.
Two aerials one transmitting one receiving
Data used
Input: CAS from ADC
Radio height, Flap and gear position, glideslope deviation
Takes into account
Descent rate and configuration
Modes
Normal TCAS II
1 excessive sink rate “SINKRATE” “PULL UP”
2 excessive terrain closure rate “TERRAIN” “PULL UP”
3 height lost after T/O “DON'T SINK”
4 unsafe terrain clearance with out landing-configuration
a. TO LOW FLAPS, TO LOW TERRAIN
b. TO LOW GEAR, TO LOW TERRAIN
only in enhanced TCAS II
5 glideslope deviation “GLIDESLOPE”
6
IRS / INS
Inertial Reference System IRS → Ringlaser gyro system
Inertial navigation System acceleration measured in direction of aircraft axis
INS → level plattform and normal gyrosystem
acceleration measured North/sout and East/West
System which is fixed on the fuselage: Strapdown
alignment time in mid-latitudes: 10min
Alignment phase
Required gyros: 3 / accelerometer: 2
Mid latitudes: 10 min for normal / shorter for Ringlaser system
search for vertical, true north, latitude and compare latitude
with entered latitude
schuler plattform → if displace oscillation within 84 min
Ringlaser Gyro
Measurement in different frequencies of two laser beams
Accelerometer
Measurement the acceleration du to gravity and aircraft
acceleration
Data
Out put: Wind direction / speed → Drift + GSPD, Position,
Time, Attitude, true heading
Input: TAS for W/V calculation
Flight warning system
TCAS
Modes
ATT- provides Attitude and Heading even when other modes
failed.
Error
Main error: gyro drift
Position error: 0.5 – 2 NM per hour
Stages
advisory – amber – crew awareness, monitoring and may be
action
Cautions – amber – immediate awareness and subsequent
action will be required
warning – red – immediate recognition and action
Errors
Navigation mode off → only attitude and heading supplies
Information sources
Transponder, Flap position, Radioaltimeter
Information given
TA → Traffic advisories → monitoring → amber solid circle
RA → resolution advisories → action without delay → red
full square
preventive resolution advisories → monitor vertical
speed
Traffic control and
alerting system
Resolution advisories doesn't take in account stall margins !
Symbols
Red full square → resolution traffic
amber full circle → advisory traffic
white/blue solid lozenge → a proximate traffic
RSR
TAR
AWR
ASDE
MHZ
Range RPM
On-route surveillance Radar
1300
300
5
Terminal area radar
3000
75
15
Airborne weather radar
9000
300
Airfield surface detection equipment
30
3
60-120