34-48-03
ú ú 02 Page 7 ú Nov 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù.AIRPLANES WITH EFIS ú
34-48-03
úú 02 Page 8 ú Nov 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
(a) (b) (c)
OF ATTITUDE SPHERE
FACSIMILE
LRRA VALID WHEN RA = DH, RA NUMERICALLRRA VALID. AIRPLANE ALT BELOW 2500' LRRA VALID. AIRPLANE 200' OR LOWER VALUE AND LETTERS DH AND NUMERICALAND ABOVE 1000'. RISING RUNWAY APPEARS BUT NOT 150'. RISING RUNWAY MOVES UP VALUE BLINK (YELLOW) FOR 3 SECONDS,ONLY IF RA IS 2500' OR BELOW AND WHEN AIRPLANE DESCENDS BELOW 200'.
THEN RA VALUE (YELLOW) IS ONLY DISPLAYED.
VOR/ILS VALID. WORD ALT (WHITE) (VOR/ILS AND RA VALID).
RISING RUNWAY ALTITUDE POSITION UNDERAPPEARS AT 1500', BLINKS FOR 3-SECONDS AIRPLANE SYMBOL SHOULD COMPARE WITH RA VALUEWHEN RA REACHES 1500', THEN REMAINS (VOR/ILS AND RA VALID).
IN VIEW UNTIL REMOVED AT AIRPLANE ALTITUDE OF 500'.
EADI Radio Altitude/Decision Height Displays Figure 4
A09832
A
737-300/400/500MAINTENANCE MANUAL
(8)
Operation of both frequency counter and driver circuits is identical. The amplifier input to a frequency counter is converted to a dc analog voltage which is proportional to the input frequency (altitude). This voltage is amplified by a driver and the driver output is the dc altitude voltage supplied to external using equipment. The output from one drive is supplied to the height indicator and the output from the other driver is available for use by other airplane systems. In addition, the output from the two drivers is applied to the receiver-transmitter high and low altitude trip circuits.
(9)
Operation of all six fixed altitude trip circuits in the R/T is identical. The dc altitude input voltage from the driver is compared to a reference voltage (altitude trip setting). If the input voltage exceeds the reference voltage, the trip relay remains de-energized. When the input voltage is less than the reference voltage, the trip relay is energized. The output from each altitude trip circuit is a ground signal to using equipment. Not all available trip circuits are used. Each trip circuit may be adjusted to a fixed setting.
(10)
The dc altitude voltage from the receiver-transmitter is applied to the height indicator pointer drive comparator. The comparator compares this voltage with the voltage from the altitude pointer potentiometer. If there is a voltage difference, the comparator supplies an error signal to the servo-amplifier. The amplifier output signal drives the servomotor which repositions the altitude pointer potentiometer until the comparator output error signal is nulled. The potentiometer and altitude pointer are both geared to the servomotor. This causes the altitude pointer to be positioned to the proper altitude.
(11)
The receiver-transmitter dc altitude voltage is also supplied to the height indicator adjustable trip (decision height (DH), comparator. The comparator compares this voltage with the voltage from the adjustable trip DH potentiometer. As long as the airplane altitude exceeds the altitude of the adjustable trip (DH cursor) setting, the trip relay and DH light(s) will remain de-energized. When the airplane altitude is slightly less than the altitude of the DH setting, the trip relay will be energized causing the DH light to illuminate at the Captain's or F/O's ADI and height indicator, as applicable.
(12)
The receiver-transmitter provides a dc altitude voltage to each pilot's ADI. On the ADI, the radio altitude bar provides an additional altitude display to the pilots from approximately 200 feet to touchdown. The altitude voltage is routed through a relay that is energized by the LRRA system flag alarm signal. If the LRRA system fails, the relay is de-energized and a bias voltage is switched to the altitude meter to bias the bar out of view.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH EFIS ú
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ú ú 01 Page 9 ú Mar 15/92
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
(13) Depressing the test switch energizes the test relay. One set of relay contacts routes a test signal from the calibration loop mixer to the receiver circuits where it is processed in the same manner as a normal altitude signal. The other set of contacts applies a dc voltage to test circuits in the AID calibration unit to bring the dc altitude to the predetermined test altitude. During self-test, each height indicator should display the test altitude.
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