B
Low Range Radio Altimeter System Component Location
Figure 1
EFFECTIVITY
CONFIG 1 AZ ALL; IB 406-499 799 Page 2
34-33-00
Apr 25/88
(2) The warning flag appears and covers the dial in the vicinity of the 100-foot indication when a malfunction occurs in the system. The altitude pointer is driven underneath the pointer mask at altitudes above 2500 feet and when a malfunction occurs in the system. The DH control knob adjusts the position of the DH index on the altitude scale thereby selecting the altitude at which the DH light on the HI and ADI operate.
C. Collins 339H-2 Height Indicator
(1)
The operating controls and indicators on a vertical scale HI consist of the following: DH index set/push-to-test control knob, DH numerical value counter, DH index tape, DH stationary reference, servo driven altitude tape which is read against a stationary airplane reference symbol, and a warning flag. Upper limit of the DH numerical counter is 499 feet. The altitude tape (scale) is graduated in feet and is black above 2500 feet and striped below zero feet. Self test of the LRRA system is initiated by pressing the SET/TEST Knob.
(2)
The DH index at the side of the altitude tape is manually positioned by rotating the SET/TEST knob to the desired DH altitude as displayed by the digital counter. The DH index is a triangle on a tape that moves with the altitude display tape after DH is set.
(3)
The DH counter provides a 3-digit indication of the adjusted DH 0 to 499 feet. When the SET/TEST knob is adjusted to a DH above 499 feet, the digital counter is hidden by a black mask. When the knob is adjusted to a DH below 0 foot, the digital counter is hidden by a striped mask.
5. ADI Displays
____________
A. A DH light is located on each pilot's ADI. The light is connected in parallel with the DH light of the height indicator located on the same instrument panel. The DH light has a press-to-test feature.
B. The rising runway symbol displays both radio altitude and localizer deviation. Radio altitude is presented by the distance between the top edge of the runway symbol and the base of the fixed airplane symbol. Localizer deviation is presented by the runway symbol moving left or right across a horizontal scale (Ref 34-31-00).
6. Operation
_________
A. Functional Description
(1) Altitude measurement operation (Fig. 3)
(a)
The LRRA system provides altitude data when 115-volt ac power is supplied to the receiver-transmitter. Low voltage power is then supplied to all circuits in the receiver-transmitter and to the height indicator power supply. The system is turned on by closing its circuit breaker(s).
(b)
The modulator generates a 100-Hz signal which is converted to a square wave and then applied to a triangular wave generator. The triangular wave frequency modulates an oscillator signal in the transmitter. The resultant signal is amplified and frequency multiplied to produce the nominal
4.3 GHz transmitter output signal.
EFFECTIVITY AZ ALL; IB 406-499
CONFIG 01 Page 3 Aug 25/88
34-33-00
LRRA System Block Diagram
Figure 2
EFFECTIVITY CONFIG 1 AZ ALL; IB 406-499 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航2(58)
