(b)
Tilt axis rotation and position sensor
(c)
Pitch resolver
(d)
Roll axis rotation and position sensor
EFFECTIVITY
AT ALL; AZ ALL; LH ALL; CONFIG 1 AF 157, 161; 01 Page 20 IB406 THRU 499 Sep 25/94
34-43-00
D. Control
(1) The weather radar system requires 115 volts ac, 400 Hz from the essential radio bus and number 2 radio bus. The system is placed in operation by setting the mode switch to STBY to allow filament warmup. If any other mode is selected, the filament warmup period will take place prior to assuming the selected mode.
WARNING: DO NOT OPERATE WEATHER RADAR WHILE THE AIRPLANE IS BEING
_______ REFUELED OR DEFUELED AND DO NOT OPERATE IN ANY RADIATING MODE WHILE A FUELING OPERATION IS BEING CONDUCTED WITHIN 300 FEET OF THE ANTENNA OR AN EXPLOSION MAY OCCUR.
PERSONNEL MUST NOT ENTER AN AREA CLOSER THAN 50 FEET OF A RADIATING ANTENNA OR INJURY TO PERSONNEL MAY OCCUR.
CAUTION: WHEN THE WEATHER RADAR IS OPERATED IN ANY MODE OTHER THAN
_______ STANDBY OR TEST, DIRECT THE NOSE OF THE AIRPLANE SO THE FORWARD 180-DEGREE SECTOR IS FREE OF LARGE METALLIC OBJECTS (HANGARS, TRUCKS, OTHER AIRPLANES, ETC.) FOR A DISTANCE OF 300 FEET AND TILT THE ANTENNA UPWARD 14 DEGREES OR DAMAGE TO RECEIVER MAY OCCUR.
DO NOT OPERATE WEATHER RADAR IN TEST MODE UNLESS ATTITUDE REFERENCE SYSTEM (INU-1 AND 2) HAS ATTAINED AT LEAST COARSE ALIGN STATUS AND IS PROVIDING VALID STABILIZATION SIGNALS. THIS IS TO PREVENT ANTENNA FROM BUMPING REPEATEDLY AGAINST STOPS.
(2)
After approximately 3 minutes, the weather radar system may be operated in the TEST mode with system 1 or 2 selected.
(3)
The ground test procedure is contained in 34-43-00, Adjustment/Test (Operational Test).
EFFECTIVITY
AT ALL; AZ ALL; LH ALL; CONFIG 1 AF 157, 161; 01 Page 21 IB406 THRU 499 Sep 25/94
34-43-00
WEATHER RADAR SYSTEM - DESCRIPTION AND OPERATION
________________________________________________
1. General_______(See figures 1 and 2.)
A. The weather radar system is a navigation system which uses the reflective effect of microwave pulses on material substances to obtain a picture of conditions ahead of the aircraft at ranges up to 300 nautical miles. Weather radar operation is based on the fact that rainfall (generally associated with storm cells) reflects a radar beam in proportion to the moisture concentration, appearing as lighted areas on the radar indicator. During iso-echo contour mode of operation, the areas of heavy rainfall are displayed as dark spots in lighted areas on the indicator.
B. The weather radar system operates in the X-band and has a penetration range through relatively light intervening rainfall to detect distant rainfall storm areas at ranges up to 300 miles. When the aircraft is approaching a storm area, the rain gradient indicated by iso-contouring is of primary importance.
C. The weather radar system consists of two identical systems, one of which may be in use with the other system in a standby mode. On passenger airplanes, two identical receiver/transmitters (R/T) are installed on the weather radar shelf (E5) in the forward equipment center as shown in Fig. 1. On freigher airplanes, two identical R/Ts are installed below the compartment floor on the centerline of the nose cargo door section as shown in Fig. 1. A waveguide switch connects the selected R/T to the antenna through the waveguide. When a GND TEST/NORMAL switch is provided on the control panel (See Fig. 1), the waveguide switch directs the R/T output into a dummy load when the GND TEST position is selected. The antenna is a split-axis dual antenna with two identical drive systems. A single control panel controls operation of the weather radar, enabling R/T selection, mode selection, testing, receiver sensitivity adjustment (GAIN), and tilt angle selection. The captain and first officer have indicators with storage CRT's and adjustable filters (polaroid type) for brightness control.
D. Weather radar system number 1 operates from the essential radio bus 115-volt ac 400-Hz, single-phase, and number 2 uses the 115-volt ac number 2 radio bus. No dc power is required.
E. The weather radar system has three types of self-test provisions; on-line monitoring for automatic fault indication, operator-actuated test for further fault identification (and/or adjustment of the display) and technician-actuated tests for fault isolation. The on-line monitoring at the control panel consists of ANT/RT fault lights. Selecting the TEST mode on the control panel causes the injection of self-test signals, which generate a test pattern on the indicator and also allow the operator to adjust the display prior to flight. The R/T remains in the receive mode and no transmissions are caused by the TEST mode. The technician-activated tests provide for testing the antenna stabilization circuits and R/T by use of test switches and lights at the R/T.
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