Stall Warning System Component Location 513
27-32-0 Figure 1 (Sheet 1) Jun 20/85
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
G10448
516 Stall Warning System Component Location
Aug 15/77 Figure 1 (Sheet 2) 27-32-0
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
3. Flap Position Transmitter
A. The flap position transmitter receives the synchro signal from the airflow sensor and modifies it for trailing edge flap position. The combined signal is then passed to the stall warning module. Two flap position transmitters are mounted in the flap drive train. (See figure l.) One cam and synchro in the right transmitter only serves the stall warning system.
4. Stall Warning Module
A. The stall warning module utilizes the combined output from the angle of airflow sensor and the flap position transmitter to control the operation of the control column shaker. (See figure 2.) The module is located in the P5 aft overhead panel. The module contains two amplifiers, a demodulator, a failure sensing circuit, a test circuit, an air/ground relay and a shaker test switch. A failure light labeled OFF on the face of the module will illuminate when system power failure or vane heater failure occurs. The test circuit is controlled from a three position toggle switch on the face of the module. The toggle switch has a positive NORMAL mode, a positive HTR OFF mode and a momentary TEST mode. The shaker test switch is located on the back of the module. This test switch may be used as a ground check to isolate a system failure to the control column shaker motor.
B. With the stall warning system activated and with the engines not running, the OFF light will be illuminated. Operating the three position toggle switch to the TEST position will provide a check of the stall warning system operation. Depressing the switch will activate the control column shaker, extinguish the OFF light and actuate the motor-driven test indicator. Failure of the OFF light to extinguish or the test indicator to rotate, indicates a failure within the stall warning system. Releasing the switch from TEST position will illuminate the OFF light, deactivate the shaker motor and stop rotation of the test indicator. Placing the toggle switch in HTR OFF mode will isolate the power source to the airflow sensor vane heater. This will enable handling of the airflow sensor while the system is in a simulated flight condition. With the toggle switch in HTR OFF mode the OFF light will stay illuminated.
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27-32-0 Page 4 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Aug 15/71
C. The air/ground relay in the stall-warning module is actuated by two relays located in the E3 electronics compartment (Fig. 2). These relays are controlled by proximity switches on the right main gear oleo. Compressing or extending the landing gear actuates the switches. The primary function of the air/ground relay in the stall warning module is to provide an inhibit signal to prevent operation of the shaker prior to liftoff and after touchdown.
5. Control Column Shaker
A. The control column shaker applies vibrations to the control column when energized by a signal from the stall warning module (Fig. 1 and 2). The shaker is clamped to the forward face of the captain's control column. The unit comprises a motor and a coaxially-mounted weighted ring assembly. Energizing the dc motor rotates the out-of-balance ring assembly. The resulting vibrations are transferred to the control column to give the required shaking action. Power to the shaker motor is obtained from the No. 1 dc electronics bus through the STALL WARN DC circuit breaker on panel P18.
6. Operation
A. With the airplane on the ground and the No. 1 engine running, electrical power applied at the circuit breakers and with the stall warning circuit breakers closed, the stall warning system is energized and 115 volts ac is applied to the vane heater. Depressing the toggle switch on the overhead panel to TEST, will activate the control column shaker and rotate the test indicator to verify a functional system. Releasing the TEST switch will deactivate the shaker and de-energize the test indicator motor (Fig. 1 and 2). At the point of liftoff, the landing gear relays de-energize the air/ground relay in the stall warning module which removes the inhibit signal to provide normal system operation. At any time after liftoff, should a signal representing an approaching stall condition develop, the stall-warning module will apply 28 volts dc to the control column shaker to provide the necessary warning. The stall warning system is designed to provide a warning at a minimum of 7 percent above airplane stall speed.
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