K41991
Flight Recorder System Component Location  5D1 
31-24-03  Figure 1  Feb 20/85 
Page 2 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

E.  The flight recorder system is composed of: one recorder, an accelerometer, a trip and date encoder panel and a test module. The recorder is installed above the ceiling panels at station 947, left of the airplane centerline. An underwater locator beacon unit is installed on the flight recorder front panel. It is a battery-powered unit, which activates immediately upon immersion in water. The accelerometer is installed near the airplane center of gravity on the aft side of the left main wheel well forward bulkhead at station 663. Access to the accelerometer is through the wheel well. The test module and the trip and date encoder panel are installed on aft overhead panel P5 in the control cabin.
F.  The recorder uses electronic bus 115 volts ac obtained through a circuit breaker on load control center P18. The test module logic circuits use 28 volts dc obtained from the flight recorder dc circuit breaker supplied by the battery bus on load control center P18. The master dimming and caution circuits supply power for the flight recorder failure warning light on the test module (Ref Chapter 33, Control Cabin Lighting).
2.  Flight Recorder Test Module
A.  The flight recorder test module contains a flight recorder failure warning light, a test switch, an auto on-off circuit and electronic circuits which are part of the stall warning system, mach warning system and master caution system. Only those components related to the flight recorder system will be described.
B.  The push-to-test flight recorder failure light provides indication of an inoperative flight recorder when illuminated. A ground for the light is completed through a de-energized system status relay in the flight recorder whenever power is not available to the flight recorder, or a fault is detected.
C.  A transistorized auto-on-off circuit and relay complete 115 volts ac power to the flight recorder. The transistor circuit is normally conducting when ground power is on the airplane and the airplane engines are inoperative; the relay is pulled in and power is disconnected to the flight recorder. The relay can become de-energized, thus completing power to the flight recorder, in any one of three ways. Starting either one of the airplane engines causes an engine oil pressure switch to close thus grounding the transistor and causing the relay to open. If the airplane is airborne and both engines should be shut down, a ground is provided through the landing gear and lever latch relays, keeping the transistor circuit grounded and thus the flight recorder still operating. A test switch on the flight recorder test module may be used to operate the flight recorder during ground maintenance checkout.
5C9 
Feb 20/84  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  31-24-03 Page 3 

3.  Trip and Date Encoder
A.  The trip and date encoder supplies signals to a trip and date information to the recorder which records the data on the recorder tape in a pulse sequence indicative of the trip and date information. The panel contains a tape time remaining indicator (not used), an EVENT push button, a REPEAT push button and an indicator light. The panel also contains six manually operated rotary switches which may be used to select a coded trip number of up to four digits and a date number of two digits. Numbers from 0 to 9 may be selected with each control. The unit contains a motor, switching disc assemblies, relays and circuitry which develop event, trip, and date signals as selected by the front panel controls. The trip and date recording cycle requires 15 minutes; the indicator light on the encoder is on whenever the encoder is cycling. Pressing the REPEAT push button will cause the trip and date information to be recorded again. Pressing the EVENT push button causes the trip and date circuits in the recorder to operate for as long as the push button is held. The EVENT button must not be operated while the trip and date data is being recorded. The encoder uses 115 volts ac and 28 volts dc obtained from the flight recorder.
B.  The encoder will operate as soon as power is supplied to the flight recorder. When 115 volts ac is applied to the encoder motor (which drives the switching discs) through de-energized relay Kl, the encoder begins its 15-minute cycle and the indicator light is illuminated. Voltage is applied to the binary trip and date circuits in the flight recorder in a sequential series corresponding to the numbers set up on the encoder. A switching disc set to the number seven will then complete seven pulses to the circuits which then apply seven pulses to the recorder. Each disc is rotated in turn until all information is recorded. At the end of the cycle, the stop contact on switching disc stops the encoder and extinguish the indicating light. Pressing the REPEAT button starts the encoder cycle again. When power is no longer available to the flight recorder and encoder the encoder is reset for an automatic cycle whenever power is returned to the system.
　
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