4.  Flight Recorder Test Module
A.  The flight recorder control panel, part of the FLIGHT RECORDER AND MACH AIRSPEED WARNING MODULE, contains a TEST NORMAL switch and an OFF light.
B.  The push to-test flight recorder OFF light, when illuminated, provides indication that the flight recorder is inoperative. A ground for the light is completed through a de-energized power relay in the flight recorder when flight recorder power is not available, or when ground is completed by a 15-second time delay circuit if the tape in the flight recorder is broken or fouled.
C.  A transistorized auto-on-off circuit and relay provides 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 not running. The relay is energized and power is not provided to the flight recorder. The relay will become de-energized thus providing 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 all engines should be shut down, a ground is provided through the ground sensing relay (AIR/GND), 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.
5.  Trip and Date Encoder Panel (if installed)
A.  The trip and date encoder supplies 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 RECORDING HOURS REMAINING indicator, an EVENT push button, a REPEAT push button and an indicator light. The panel also contains six manually operated levers 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 are 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 event binary in the recorder to operate for as long as the push button is held. The EVENT button must not be operated while trip and date data is being recorded. The encoder uses 115 volts ac obtained from the MACH AIRSPEED WARNING module and 28 volts dc obtained from the flight recorder.
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B.  The encoder will operate when 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 K1, 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 pulse marks on the recorder tape. 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.
6.  Operation (Fig. 2)
A.  Parameter Inputs
(1)  
The UFDR receives inputs from sensors and signals from other airplane systems. The inputs are grouped as analog and discrete, and are listed as follows:

(2)  
Analog Inputs

(a)  
Accelerometer 1) The accelerometer provides acceleration signals to the UFDR. 2) The accelerometer receives 26-volt ac power from the UFDR.

(b) 
 Synchro Input Sources 1) Altitude and airspeed signals from the air data computer. 2) Compass heading information from compass system.

(3) 
 Discrete Inputs

(a)  Ground keying signals are received from each VHF communication transceiver.

(4) 
 UFDR Functions

(5)  
The data is sequentially recorder on eight channels. The read/write channels are operated by the track select circuit and the tape transport by the microprocessor. During recording, the tape moves two steps forward and one step back. The tape speed stabilizes on the initial step. Recording takes place on the second step which is followed by a back stroke for verification. The data recorded on the preceding second forward step is read for playback and verification during the current first forward step.
　
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