(a)
P6 Main Power Distribution Panel
1) DIM & TEST INDICATOR LIGHTS
(b)
P18 Overhead Circuit Breaker Panel
1) GND PROX WARN
(2)
Install the GPWS control module:
(a)
Connect the electrical connector to the control module.
(b)
Lightly push the control module into the instrument panel.
(c)
Tighten the fasteners that attach the control module to the instrument panel.
(3)
Remove the DO-NOT-CLOSE tags and close these circuit breakers:
(a)
P6 Main Power Distribution Panel
1) DIM & TEST INDICATOR LIGHTS
(b)
P18 Overhead Circuit Breaker Panel
1) GND PROX WARN
(4)
Supply electrical power (Ref 24-22-0).
(5)
Make sure the GPWS control module panel lights are on.
(6)
Remove electrical power if it is not necessary (Ref 24-22-0).
500
Feb 20/91 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 34-42-21 Page 401
LOW RANGE RADIO ALTIMETER SYSTEM - DESCRIPTION AND OPERATION
EFFECTIVITY
GJ ALL EXCEPT B-2509, B-2510
1. General
A. The low range radio altimeter (LRRA) system supplies vertical position information for use by the pilots during approach and landing phases of flight operation. The LRRA system provides an accurate measurement of absolute altitude (height above terrain) from 2500 feet to touchdown. Flag alarm, A/P failure warning, dc altitude, and vertical terrain clearance (altitude trip) outputs are available for use by other systems.
B. The system consists of a receiver-transmitter, two height indicators, two decision height (DH) lights (one on each ADI), transmit antenna, and receive antenna. The location of components is shown on Fig. 1.
C. The system receives 115-volt ac power through circuit breaker RADIO ALTM-1 located on panel P18-1 at the left load control center.
D. The LRRA system supplies flag alarm and dc altitude signals to the autopilot system and flag alarm and 200- and 1500-foot altitude trip signals to the flight director system. Dc altitude and flag alarm signals are supplied to the ground proximity warning system.
2. Receiver-Transmitter (Fig. 1)
A. The receiver-transmitter is located on shelf four of E2 electronic rack. All electrical connections to the receiver-transmitter are made through a connector located on the rear panel. An auxiliary connector located on the front panel is provided for connecting to test equipment.
3. Height Indicator (Fig. 1)
A. Airplane altitude is read from a circular dial which is calibrated from 0 to 2500 feet. Dial calibration is linear from -10 to 480 feet and logarithmic from 480 to 2500 feet. Below 500 feet, the dial is divided into 10-foot increments. Above 500 feet, it is divided into 100-foot increments.
B. The DH control knob is used to adjust the position of the DH cursor to any altitude shown on the dial. The DH cursor setting designates the altitude at which the DH light on each ADI will be energized during airplane descent or de-energized during airplane ascent.
C. The warning flag is solenoid operated and will come into view whenever the solenoid is de-energized.
D. The PUSH TO TEST switch is used to initiate a functional check of the LRRA system.
4. Antenna
A. The antennas are linearly polarized horns. Two identical antennas are used in the system, one for transmitting and one for receiving. The antennas are connected to the receiver-transmitter with coaxial cables and are flush mounted on the lower fuselage centerline of the airplane as follows: receive antenna at station 430, transmit antenna at station 450.
5C8
Oct 20/85 34-48-0 Page 1
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
K77093
Low Range Radio Altimeter System Component Location 5C8
34-48-0 Figure 1 Oct 20/85
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
5. ADI Displays
A. A DH (decision height) light is located on each pilot's ADI and is controlled by the height indicator located on the same instrument panel. The brightness of the light is controlled by the master dim control.
B. The receiver-transmitter supplies a dc altitude signal to the ADI rising runway symbol. The rising runway comes into view at the bottom of the ADI at approximately 200 feet and shows relative airplane altitude from 200 feet to touchdown.
6. Operation (Fig. 2)
A. Altitude Measurement Operation
(1)
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