BOEING 737MAINTENANCE MANUAL_CHAPTER 22
<P>**** Hidden Message *****</P><P>BOEING 737MAINTENANCE MANUAL</P> <P>AUTO FLIGHT - GENERAL - DESCRIPTION AND OPERATION<BR>1. General<BR>A. The auto flight systems consist of an Autopilot and Yaw Damper System and a Mach Trim<BR>System. Partial provisions for an Auto Throttle System are also installed on the airplane.<BR>B. Autopilot and Yaw Damper Systems<BR>(1) The autopilot system controls the airplane about the pitch and roll axes and provides<BR>automatic airplane stabilization whenever the pitch and roll channels are engaged.<BR>Automatic stabilizer trim, which is a function of the pitch channel, compensates for<BR>changes in airplane trim due to fuel burnoff etc. Each autopilot channel may be engaged<BR>separately and, in some modes, are not dependent upon each other. Various mode<BR>selections enable the pilots to command the autopilot to fly the airplane onto a selected<BR>heading, maintain altitude, or fly to a selected VOR, localizer or OMEGA course as well as<BR>make automatic approaches to runways equipped with ILS facilities. The pilots may also<BR>manually control the airplane in a normal manner with the control wheel/column (control<BR>wheel steering) without disengaging the pitch or roll axes of the autopilot system. Pilots<BR>can then assist the autopilot system in flying to a selected heading or course. Use of<BR>control wheel steering does not disengage either channel of the autopilot system.<BR>(2) The yaw damper system provides airplane stabilization about the yaw axis. Automatic<BR>damping of dutch roll is sensed and corrected for by the yaw damper system whenever<BR>the system is engaged. Rudder deflections are not felt by the pilots since the rudder<BR>pedals are not moved by the yaw damper system. No interlocks are provided between the<BR>yaw damper system and the autopilot system.<BR>(3) The autopilot and yaw damper systems operate in conjunction with hydraulic power<BR>control units which drive the airplane ailerons, elevators and rudder. Refer to Chapter 27,<BR>Flight Controls.</P>
<P>C. Mach Trim System<BR>(1) The mach trim system provides automatic repositioning of the elevators as a function of<BR>mach number. As the airplane enters the mach tuck region, the elevator is repositioned to<BR>provide a new neutral in an upward direction which is proportional to the increase in mach.<BR>The mach trim system operates with or without the autopilot system engaged.<BR>(2) The mach trim system operates in conjunction with the elevator hydraulic power control<BR>units and stabilizer/elevator neutral shift mechanism. Refer to Chapter 27, Elevator and<BR>Tab Control System.<BR>D. Auto Throttle System<BR>(1) The autothrottle system (if installed) automatically monitors airplane airspeed and adjusts<BR>throttle settings to maintain a selected airspeed. The autothrottle system is intended to<BR>assist the pilots in maintaining a constant airspeed when making landing approaches. The<BR>autothrottle system is independent of the autopilot system and operates with or without the<BR>autopilot system engaged.</P>
<P>AUTO FLIGHT-GENERAL - MAINTENANCE PRACTICES<BR>1. General<BR>A. In order to maintain the integrity of the auto flight systems, it may become necessary to replace<BR>electro-hydraulic components on the elevator, aileron, and rudder power control units. This<BR>would involve handling BMS 3-11 hydraulic fluid. The following information is provided to aid in<BR>handling BMS 3-11.<BR>2. BMS 3-11 Handling Procedure<BR>A. BMS 3-11 is the general specification for the fluid that is used in all hydraulically operated<BR>systems. BMS 3-11 is a fire-resistant base fluid to which suitable additives have been<BR>incorporated. All fluids meeting this specification can be intermixed in any amount with no<BR>separation, precipitation or cloudiness. All airplane equipment using BMS 3-11 are identified by<BR>nameplates.<BR>CAUTION: BMS 3-11 FLUID IS NOT COMPATIBLE WITH MIL-H-5606 FLUID. MIXING<BR>THESE FLUIDS, IN ANY AMOUNT, WILL COMPLETELY RUIN THE INTEGRITY<BR>OF THE HYDRAULIC SYSTEM.<BR>B. Areas where hydraulic fluid may leak are designated as possible BMS 3-11 contamination<BR>areas. Special paint and protective finishes are used to prevent damage in these areas. Refer<BR>to Chapter 51, Structures - Protective Finishes.<BR>C. BMS 3-11 has little or no effect on the metals used in aircraft construction up to 240F. Only<BR>materials compatible with BMS 3-11 fluids, such as ethylene propylene, butyl rubber and teflon,<BR>are used for system seals, gaskets, O-rings, and hose linings.<BR>D. Skin irritation in the form of dry or cracked skin may result from prolonged or repeated contact<BR>with BMS 3-11. It also causes painful but temporary irritation to the eyes and may produce a<BR>burning sensation to other sensitive parts of the body. Inhalation of the fluid in the form of spray<BR>of fine mist may cause irritation of the upper respiratory tract. To minimize contact with BMS<BR>3-11, wear gloves, goggles, face shields or safety glasses whenever there is danger of<BR>exposure. If exposure occurs, flush the eyes immediately with water and report to medical for<BR>observation.<BR>WARNING: BMS 3-11 HEATED TO TEMPERATURES ABOVE 450F CAN BE<BR>DECOMPOSED INTO TOXIC FUMES AND GASES. AVOID INHALATION OF<BR>FUMES AND VAPORS FROM OVERHEATED BMS 3-11. IF IT IS NECESSARY<BR>TO WORK IN THESE FUMES AND VAPORS, SAFETY APPROVED EYE AND<BR>RESPIRATORY PROTECTION ARE MANDATORY.</P>
<P>1. General<BR>A. The Sperry SP-77 Automatic Flight Control System (autopilot and yaw damper system)<BR>provides automatic operation of airplane flight controls to maintain altitude, attitude and heading<BR>references, yaw damping, automatic tracking and control of omnirange navigation throughout<BR>the various flight regimes, and automatic approach.<BR>B. The autopilot and yaw damper system is characterized by the following features:<BR>(1) Control wheel steering (CWS) for pitch and bank rate maneuvering.<BR>(2) Full time series yaw damping with control cabin self-test and full-time yaw damper position<BR>indicator.<BR>(3) All angle radio beam capture with control wheel steering maneuvering.<BR>(4) Solid state (microelectronic) interlock, and operating circuits.<BR>(5) Plug-in modules on hinged cards for ease of maintenance.<BR>C. The autopilot and yaw damper attains optimum smoothness and stability of control by the use<BR>of error information based not only on the magnitude of the airplane and its control surface<BR>displacements from reference positions and angles, but also on the rate of change of these<BR>displacements. Optimum sensitivity and accuracy in maintaining system integrity are attained<BR>by integrating the displacement errors with respect to time and by making control surface<BR>movement a function of indicated airspeed. The following is a brief explanation of these<BR>principles of operation:<BR>(1) Physically, when a sudden change in airplane or control surface position or angle occurs,<BR>a large rate of change of position exists before there is time for a significant displacement<BR>actually to take place. By applying control forces based on this rate of change instead of<BR>waiting for a significant displacement to build up, the initial control forces are greatest at<BR>the inception of the error and consequently are most effective when needed. Thus,<BR>considerable</P>
<P>corrective action is accomplished before the displacement becomes large and the<BR>possibilities of large deviations from reference conditions are greatly reduced. The rate at<BR>which these displacement corrections take place is damped by input rate information to<BR>assure return to reference conditions with practically no overshoot. When the<BR>displacement error is no longer changing, the rate signals fall to zero and the error existing<BR>at that instance is acted upon by control forces that are proportional only to the error<BR>magnitude. The combination of displacement control and rate control provides the desired<BR>smoothness and stability of operation.<BR>(2) Integration in the autopilot provides an extremely accurate means of automatically<BR>retaining reference flight conditions when sustained or recurring displacement from the<BR>references caused by wind or loading changes exist. A persistent displacement error, from<BR>a flight reference, may exist at such a low level that it will not actuate the associated servo<BR>channel to cause corrective action. Errors of this nature will produce increasing errors in<BR>airplane displacement as they are permitted to remain. Small signal errors are integrated<BR>against time to build up small displacement errors to usable values so they will correct the<BR>error through the associated servo channel. The integrated signal remains at the value<BR>required to overcome the displacement error, compensating for required changes in the<BR>original flight references.<BR>(3) The response of the airplane to control surface movement is aerodynamically a function of<BR>dynamic air pressure. As the dynamic air pressure increases there is a decrease in the<BR>amount of control surface movement required to produce a given change or rate of<BR>change in airplane attitude. Therefore, to maintain accurate control of the airplane at all<BR>airspeeds, continuous adjustment of the autopilot channel control surface gains is<BR>provided.</P> BOEING 737MAINTENANCE MANUAL_CHAPTER 22 好的资料！好的资料！ 111111111111111111111111111111111
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