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2.32.5 Pilot-Assist Controls. An AUTO FLT CONT panel (Figure 2-12), in the lower console, contains the con-
trols for operating the pilot-assist servos and actuators. The panel contains SAS 1, SAS 2, TRIM, FPS, BOOST and the FAILURE ADVISORY/POWER ON RESET lights/ switches. STICK TRIM and TRIM REL switches on the cyclic sticks, are manually operated by either pilot or copi-lot.
2.33 AUTOMATIC FLIGHT CONTROL SYSTEM (AFCS).
The AFCS enhances the stability and handling qualities of the helicopter. It is comprised of four basic subsystems: Stabilator, Stability Augmentation System (SAS), Trim Systems, and Flight Path Stabilization (FPS). The stabilator system improves .ying qualities by positioning the stabila-tor by means of electromechanical actuators in response to collective, airspeed, pitch rate and lateral acceleration inputs. The stability augmentation system provides short term rate damping in the pitch, roll, and yaw axes. Trim/ FPS system provides control positioning and force gradient functions as well as basic autopilot functions with FPS engaged.
2.33.1 Stability Augmentation System (SAS).
NOTE
As the vertical gyro comes up to speed or when the system is shutdown, the derived pitch/roll rate signal which feeds SAS 1 will cause small oscillations in pitch and roll SAS actuators. This is a temporary situation and can be eliminated by turning SAS 1 off.
The SAS enhances dynamic stability in the pitch, roll, and yaw axes. In addition, both SAS 1 and SAS 2 enhance turn coordination by deriving commands from lateral accel-erometers which together with roll rate signals are sent to their respective yaw channels automatically at airspeeds greater than 60 knots. The SAS 1 ampli.er circuitry oper-ates on 28 vdc power from the dc essential bus through a circuit breaker marked SAS BOOST providing excitation for the electronic components within the ampli.er. AC power from the ac essential bus through a circuit breaker marked SAS AMPL is also required for normal operation of the SAS. The SAS ampli.er uses the vertical gyro roll output to derive roll attitude and rate for the roll SAS com-mands and an ac-powered yaw rate gyro for the yaw SAS commands. Loss of ac power to the vertical gyro or SAS ampli.er causes erratic operation of SAS 1 due to loss of the reference for the ac demodulators. When this condition is encountered, the pilot must manually disengage SAS 1. In case of a malfunction of the SAS 2 function, the input will normally be removed from the actuator and the SAS 2 fail advisory light on the AUTO FLT CONT panel will go on. If the malfunction is of an intermittent nature the indi-cation can be cleared by simultaneously pressing POWER ON RESET switches. If the malfunction is continuous, the SAS 2 should be turned off. With SAS 1 or SAS 2 off, the control authority of the stability augmentation system is reduced by one-half (5% control authority). Malfunction of the SAS 1 system may be detected by the pilot as an erratic motion in the helicopter without a corresponding failure advisory indication. If a malfunction is experienced, SAS 1 should be turned off. SAS actuator hydraulic pressure is monitored. In case of loss of actuator pressure, or if both SAS 1 and SAS 2 are off, the SAS OFF caution light will go on.
2.33.2 Trim System. When the TRIM is engaged on the AUTO FLT CONT panel, the pitch, roll and yaw trim systems are activated to maintain position of the cyclic and tail rotor controls. Proper operation of the yaw trim requires that the BOOST on the AUTO FLT CONT panel be on. The tail rotor and lateral cyclic forces are developed in the electromechanical yaw and roll trim actuators. Both yaw and roll trim actuators incorporate slip clutches to allow pilot and copilot control inputs if either actuator should jam. The forces required to break through the clutch are 80-pounds maximum in yaw and 13 pounds maximum in roll. The longitudinal force is developed by an electrohy-dromechanical actuator operated in conjunction with the SAS/FPS computer. When the pilot applies a longitudinal or lateral force to the cyclic stick with trim engaged, a combination detent and gradient force is felt. The pilot may remove the force by pressing the thumb-operated TRIM REL switch on the pilot/copilot cyclic grip. The pedal gra-dient maintains pedal position whenever the trim is engaged. By placing feet on the pedals, the pedal switches are depressed and the gradient force is removed. The pedals may then be moved to the desired position and released. The pedals will be held at this position by the trim gradient. The pedal trim gradient actuator also includes a pedal damper. The pedal damper is engaged continuously, inde-pendent of electric power and the TRIM switch on the AUTO FLT CONT panel. Operation of the trim system is continuously monitored by the SAS/FPS computer. If a
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