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1、 Civil Aviation Flight University of China Autopilot 自动驾驶仪Autopilot (AP) Civil Aviation Flight University of China The basic function of the autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without any action being required by the pilot (Once the p

2、ilot has selected the appropriate control mode(s) of the autopilot.). Autopilot Civil Aviation Flight University of China Autopilot Components Autopilot Control The control function allows the pilot to engage and disengage the autopilot, and instruct it to follow selected paths such as navigation tr

3、acks, climbs/descents, and specified altitudes. These paths are normally referred to as modes.Figure 3.5 Civil Aviation Flight University of China Signal Processing The computing capabilities of autopilot systems have improved to the stage where a modern system can command virtually any flight path

4、required. Provided it is within the performance capability of the aircraft. To satisfy various altitude and speed requirements, the signal processing function must be capable of varying the demanded control deflection to suit the situation. Autopilot Components Civil Aviation Flight University of Ch

5、ina Signal Processing Control inputs needed to hold an ILS glidepath at low speed will be different to those needed to maintain altitude and heading whilst in the cruise at high Mach number. To meet these demands, the signal processing function of the AFCS must be suitably programmed and, in additio

6、n to providing an output signal to the controls to satisfy a selected mode (e.g. hold a selected altitude), the processor must constantly analyze inputs to see if the required values are being achieved. Autopilot Components Civil Aviation Flight University of China Signal Processing Sensing systems

7、must provide inputs to the processor about deviations from the selected value. Also, the processor must receive feedback from the control servos to ensure that the commanded control movements have been achieved.Autopilot Components Civil Aviation Flight University of China Servos Electrical signals

8、from the processor command the flight control system to move as needed. Since a modern three-axis autopilot controls the aircraft in all directions, the processor must provide command inputs to three separate servo systems.Autopilot ComponentsAileronProcessorRudderServoServoServoElevatorFeedback Civ

9、il Aviation Flight University of China Flight Controls In response to electrical command signals, the servos move the various control surfaces. Because modern aircraft are very large and may have split controls on each axis (e.g. inboard and outboard ailerons), a number of servomotors may be require

10、d for each axis. Autopilot ComponentsFigure 3.5AileronRudderElevator Civil Aviation Flight University of China Sensing Systems Once the control surface has moved, an alteration to aircraft flightpath will occur. This alteration will then be detected by the appropriate system (e.g. air data computer

11、for a change in speed), which will provide a performance feedback signal to the autopilot processor. In this way, command signals can be varied to ensure that the correct performance is achieved.Autopilot ComponentsFigure 3.5 Civil Aviation Flight University of China Autopilots fitted to modern airc

12、raft feature a unique aural warning and a flashing warning light system which operates whenever the autopilot disengages, either by the pilot selecting the system OFF, or by a failure rendering the autopilot inoperative. Either way, the pilot has to push a cancel button in order to silence the aural

13、 warning and extinguish the flashing light. Disengagement Warning Civil Aviation Flight University of China Figure 3.7Autopilot Control Panel Engage/Disengage Switch This switch engages or disengages the autopilot. The autopilot cannot be engaged if the turn knob is out of the center detent position

14、. The switch is electrically held in the ENGAGE position, and loss of electrical power, or a signal from the autopilot disconnect on the control column, will cause the switch to spring back to DISENGAGE. Civil Aviation Flight University of China Pitch Selector The pitch (mode) selector determines wh

15、ich vertical mode is engaged from the options shown the selector, via : MACH HOLD IAS HOLD VERT SPEED PITCH HOLD Autopilot Control Panel Civil Aviation Flight University of China Pitch Selector When selecting either MACH, IAS, VERTICAL SPEED, or PITCH, the autopilot will hold the value existing when

16、 that mode is engaged. Autopilot Control Panel Civil Aviation Flight University of China Pitch Selector The HOLD modes (Mach, IAS, or PITCH) e inoperative and the pitch mode selector will then revert to the VERT SPEED position, when: the VERT SPEED wheel is moved; ALT HOLD is engaged; and the glides

17、lope is captured.Autopilot Control Panel Civil Aviation Flight University of China Vertical Speed Wheel When VERT SPEED is selected on the pitch mode selector, the aircraft pitch attitude is controlled by the pilot rotating the VERT SPEED wheel (sometimes called the pitch wheel) . This is the basic

18、pitch mode of the autopilot. Autopilot Control Panel Civil Aviation Flight University of China Vertical Speed Wheel The VERT SPEED wheel is indexed in 500 ft increments and rotates automatically to match current vertical speed when the pitch selector is in any mode other than VERT SPEED, whether the

19、 autopilot is engaged or not. This ensures a smooth transition when the autopilot is engaged. Autopilot Control Panel Civil Aviation Flight University of China Vertical Speed Wheel Any movement of the VERT SPEED wheel will cause a corresponding attitude change to achieve the selected rate of climb o

20、r descent, as indicated by the scale on the wheel. In pitch modes other than VERT SPEED, any pilot-induced movement of the pitch wheel will override the selected pitch mode, and the pitch mode selector will revert to VERT SPEED. VERT SPEED is INOP when glideslope is captured or autopilot is disengag

21、ed.Autopilot Control Panel Civil Aviation Flight University of China ALT Hold Altitude hold is a sub-mode of the VERT SPEED wheel. ALT HOLD will command the autopilot to adjust the pitch attitude to hold the present altitude. On most autopilots any pre-selected altitude to be acquired on climb or de

22、scent is entered via a separate controller, and the autopilot VERT SPEED wheel will move to ALT HOLD as the selected altitude is captured.Autopilot Control Panel Civil Aviation Flight University of China ALT Hold ALT HOLD will disengage if: GO AROUND is selected; glideslope is captured in APP AUTO m

23、ode; APP MAN is selected; VERT SPEED wheel is moved from center detent position; or autopilot is disengaged.Autopilot Control Panel Civil Aviation Flight University of China NAV Mode Selector It allows the pilot to connect the autopilot to the required navigation system for automatic steering. Navig

24、ation modes available are: AUX NAV NAV/LOC TURN KNOB AUTO G/S MAN G/S Autopilot Control Panel Civil Aviation Flight University of China NAV Mode Selector Selection of AUX NAV programmes the autopilot to respond to signals from a secondary navigation receiver, such as INS. The NAV/LOC selection progr

25、ammes the autopilot system to respond to signals from the primary VHF navigation system so that it will acquire and follow a selected VOR radial or localizer track. The autopilot must be steered towards the selected course. Positioning the navigation mode selector to TURN KNOB allows the pilot to st

26、eer an aircraft by using the turn knob; this is the basic roll mode of the autopilot. Autopilot Control Panel Civil Aviation Flight University of China NAV Mode Selector AUTO G/S arms the autopilot system to maintain the current pitch and roll modes until the selected localizer track is intercepted,

27、 after which the autopilot will track the localizer. When the glideslope is captured, the pitch mode selector will revert to VERT SPEED, and the autopilot will control the aircraft to follow the glideslope and its associated glidepath. Some autopilots will not capture the glideslope unless the local

28、izer has been captured first. Autopilot Control Panel Civil Aviation Flight University of China NAV Mode Selector MAN G/S arms the autopilot to immediately intercept the localizer at a programmed intercept angle, usually 30, and to climb or descend, as appropriate, to intercept and track the glidesl

29、ope. Some autopilots will not respond to MAN G/S from above the glideslope, and in this case, the pilot must use the pitch wheel to institute a descent of sufficient magnitude to intercept the glideslope.Autopilot Control Panel Civil Aviation Flight University of China TURN Knob The turn knob allows

30、 the pilot to steer the aircraft without disconnecting the autopilot. Movement of the turn knob out of its detent will override any current NAV mode, and the NAV mode selector will revert to TURN KNOB mode. Once out of the detent position, the turn knob will remain at its displaced position, and the

31、 aircraft will continue to turn in the direction commanded by the turn knob. The knob must be centered manually to return to level flight. The turn knob must be in the detent position before the autopilot can be engaged, or before another NAV mode can be selected.Autopilot Control Panel Civil Aviation Flight University of China HDG SEL When selected, this button engages a heading function which commands the autopilot to