E. Altitude and airspeed data are obtained from the air data computer. The air data computer provides a single three-phase synchro signal representing airspeed and both coarse and fine synchro signals representing altitude. These signals, along with synchro reference voltages provided by the air data computer are used by servomechanisms to position cams which position the scribers.
F. The heading, airspeed, altitude and acceleration scribes are caused to press against the tape periodically by a pressure bar, thus marking the tape in a rectilinear fashion. Heading, airspeed, and altitude are recorded at 1-second interval. Acceleration is recorded 1.8 times per second. The scribes assume their new positions during that time in which they are not pressed against the tape. The other three scribes are solenoid-operated and record continuously. One solenoid-operated scribe provides the north-south reference lines, and the second scribes the 1-minute timing marks. The third scribe records radio transmission on any of the airplane radios. The radio transmission signal is dc ground provided to the recorder by the diode module in the audio accessory unit when any radio transmitter is keyed.
G. The front panel of the recorder contains the pitot static connections and the time remaining indicator. The indicator indicates the number of hours of tape remaining on the spool. A door on the front provides access for removal and installation of the magazine assembly. The recorder uses 115-volt, 400-Hz ac. Monitor circuits in the recorder unit monitor input power and tape motion. They provide a ground to turn on the failure light if power is removed or if tape motion is stopped.
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31-24-01 Page 8 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Nov 15/79
6. Operation (Fig. 2)
A. The flight recorder will start automatically as soon as power is supplied to load control center P18 and an engine is started. Either one of the engines' oil pressure switches will complete the circuit to activate the recorder whenever they are started. The landing gear lever latch relays complete a parallel circuit with the oil pressure switches whenever the airplane is airborne; thereby, providing backup control to keep the recorder operating in case of engine failure. The recorder may be operated manually for ground maintenance checks by pressing the flight recorder test button on overhead panel P5. The flight recorder failure warning light (push-to-test type), adjacent to the test button, will be illuminated whenever: flight recorder power fails, power is on the airplane and both engines are shut down, or the magazine is removed.
B. When power is supplied to the flight recorder, externally supplied information is applied to mechanically position the scribes. As the foil advances, a pressure bar depresses the four parameter scribes onto the recording foil for a short time, thus scribing the foil in a rectilinear fashion. The heading ambiguity scribe, (trip and date) reference scribe record continuously. Since the recording foil travels at a controlled rate, a time base is provided for the recorded information.
C. The trip and date encoder operates in conjunction with the flight recorder to place coded information on the recording tape to identify trip, date and events. When the flight and date digital levers on the encoder are positioned, they set up circuits to the trip and date solenoid scribe. When power is supplied to the recorder and the encoder REPEAT button is pressed, the encoder goes through a 15-minute recording time cycle and then shuts off. The switching disk assembly supplies 28 volts dc to the recorder reference solenoid in an on-off sequence as selected by the thumbwheel switches. The amber light will be illuminated whenever the trip and date recording cycle is in process. The REPEAT button can be pressed to start a new cycle at any time after the first 15 minutes of recorder operation. The REPEAT button must be held in until the amber light remains on when the button is released (about 9 seconds). If the recorder power is interrupted during the recording cycle the encoder will stop but will continue from the stopped position when power is restored. An event may be scribed on the tape by pressing the EVENT button after the initial trip and date data have been recorded. The EVENT button should not be pressed until at least 5 minutes after the encoding cycle has been completed to prevent confusion between recorded encoding data and event data. The EVENT button should be held for 5 seconds or longer and then released for 9 seconds or longer. About 20 seconds should be left between coded numbers.
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