radar altimeter presentation
TRANSCRIPT
ALTIMETER1. Barometric Altimeter
QNH QFE QNE
2. Radar altimeter
RADIORADAR
Invented In 1924 by Lloyd ESPENSCHIED
In 1938, in cooperation with Bell Labs, United Air Lines used it as a terrain avoidance device
RADAR ALTIMETER
Provides distance between plane and ground below it
RADIO ALTIMETER
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Measures altitude above the terrain
LRRA
RA
DH Annunciator
Decision Height Bug
Failure Warning Flag
Altitude Pointer
TEST Push Button
DH SET Knob
COMPONENTS
Accuracy: ± (3%+5’) in landing attitudeFrequency: 4200-4400MHz It uses SHF band
Antenna has a lobe of about 80°
It can detect height correctly up to bank angles of about 40°
For landing as pitch and roll do not normally exceed 20°
Radar Altimeter Antenna
METHODS USE IN RADAR ALTIMETRY
• Radiation consists of a series of discrete pulses• By transmitting radio waves downward• Interpreting the time it takes for the waves to reflect
back
• Sends out a continuous transmission wave• Distance = size of shift in signal's frequency• The greater the shift the further the distance
travelled• Ground proximity warning
1.PULSE MODULATED RADAR
2.FMCW
OPERATION
• It is a CW radar system • Separate transmit and receive antennas• Single antenna is not reliable
Principle Of Radar Altimeter
• Frequency modulated continuous wave
• It uses the principle of RADAR
• Speed, distance and time are related
• S=VT• Radio waves are transmitted towards the ground and
the time it takes them to be reflected back and return to the aircraft is timed
Military Applications1 To fly quite low over
the land and the seaTo avoid radar detection To avoid targeting by anti-aircraft guns
To avoid surface-to-air missiles
Terrain-following radar, which allows fighter bombers to fly at extremely low altitudesIn modern fighter aircrafts, forward terrain looking radars are also used F/A-18 Super Hornet warplanes flown by the Americans and by the Australians
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For approach and landing
In low-visibility conditions
In automatic landings
Allowing the autopilot to know when to begin the flare maneuver Radar Altimeters give data to the auto throttle
Give readings up to 2,500 feet (AGL)
Almost all airliners are equipped with radar altimeters
Concorde and the British Aircraft Corporation BAC 1-11
ATR 42 and BAE Jetstream series)
1Civil Application
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