Flight Controls

Flight Control Artificial-feel System Failure

The aztificial-feel system failure can be indicated by a lightening of stick forces (resulting in over-control), lack of trim response, and poor stick-centering characteristics. If failure of flight control artificial-feel is encountered, proceed as follows:

  1. Airspeed — Reduce. Reduction of airspeed may relieve severe oscillation of the airplane.
  2. If adequate control cannot be maintained — Eject. Ejection is recommended whenever failure of the artificial-feel system is evident by loss of adequate control.

Flight Control Hydraulic System Failure.

Failure of one flight control hydraulic system does not affect the operation of the other system, which assumes the entire load of flight control operation. (Refer to Flight Control Hydraulic Systems in section I.) The mission should be aborted and a landing made as soon as possible; however, under such a condition, flight control operation may be somewhat slower because of reduction of hydraulic flow. If either system fails, the flight system failure warning light will come on. Proceed as follows:

  1. Determine which system has failed. Check each system hydraulic pressure to determine the nature of the failure. Low pressure indicates a pump or line failure with resultant loss of pressure. Normal pressure but with no fluctuation in response to fore-and-aft control movement indicates a blocked or run-around condition. The emergency hydraulic pump will not supplement the No. | system in case of a No. 2 system block.
  2. Land as soon as possible.

During landing approach: 3. Monitor the good system.

  1. Fly long final approach. A long, straight-in, final approach should be used, and rate of descent should be between 1000 and 1500 feet per minute (remaining above safe ejection altitude as long as practical). Reduce rate of descent to below 1000 feet per minute just before flare.
  2. Emergency hydraulic pump lever (RAT) — ON. The emergency pump will automatically come on when engine rpm drops below 40% rpm. Otherwise, it must be turned on manually. Place emergency hydraulic pump lever in ON position to supplement output of the engine-driven hydraulic pump during landing. Keep control movements to a minimum during entry onto final approach and on final.
  3. Use minimum throttle movements.

  4. Use minimum control movements. In case of engine failure, the ram-air, turbine-driven flight control emergency pump must be started during the landing approach to supplement the output of the enginedriven hydraulic pumps, to ensure effective control action while landing. (Refer to Flight Control System Emergency Hydraulic Pump in section VII.) Should the engine freeze, preventing operation of the engine-driven pumps, or if failure of both engine-driven pumps occurs, power in flight control system No. 2 can be supplied by the emergency hydraulic pump. When the emergency hydraulic pump lever is moved forward to ON, utility hydraulic pressure (or pressure from an emergency accumulator) opens the air turbine inlet-outlet doors so that ram-air drives the turbine for emergency pump operation. (The pump lever must be returned to OFF manually, to shut down the pump, if it is no longer needed.)

    Warning

    Because of the reduced total output, unnecessary control movement should be kept to a minimum when the emergency pump is the only source of flight control power. This is an emergency system which will not provide normal maneuvering capability, but is considered adequate for a proficient pilot flying under normal conditions of visibility and turbulence, with adequate runways to permit a well planned approach. Under other circumstances, the pilot’s judgment must prevail.

    Warning

    If complete flight control hydraulic system failure occurs (that is, pressure cannot be maintained by the emergency pump upon loss of the engine-driven pumps, or because of malfunctions in the systems), stick forces become extremely high. As a result, control of the airplane in cruising flight is very difficult, and control at high speeds or during maneuvers is impossible. Therefore, if such a failure is encountered, try to reduce airspeed to about 200 knots, and try to maintain control by steady push or pull force on the stick and by varying thrust settings. If control cannot be maintained, eject. If some control is available, however, and altitude and other conditions permit, attempt to return to a suitable area. Then eject, because extended flight and a landing with such high stick forces should not be attempted under any circumstances.