After Level Off
Recheck the pressurization system and evaluate the situation. Do not remove the crew oxygen masks if cabin altitude remains above 10,000 feet. Determine the new course of action based on weather, oxygen, fuel remaining, medical condition of crew and passengers, and available airports. Obtain a new ATC clearance.
Stall Recovery
The objective of the approach to stall recovery maneuver is to familiarize the pilot with the stall warning and correct recovery techniques. Recovery from a fully developed stall is discussed later in this section.
Approach to Stall Recovery
The following discussion and maneuvers are for an approach to a stall as opposed to a fully developed stall. An approach to a stall is a controlled flight maneuver; a stall is an out-of-control, but recoverable, condition.
Approach to Stall Recovery Command Speed
As the airplane is decelerated to the desired initial condition for the approach to stall, set command speed to the maneuver speed for each selected flap setting. For the approach to stall in the landing configuration, set command speed to VREF 30
+ 5 knots.
Initial Buffet-Stall Warning-Stall Buffet
Approach to stalls are entered with thrust set appropriate for an airspeed decrease
of 1 knot per second. During the initial stages of a stall, local airflow separation results in initial buffet giving natural warning of an approach to stall. A stall warning is considered to be any warning readily identifiable by the pilot, either artificial (stick shaker) or initial buffet. Recovery from an approach to stall is initiated at the earliest recognizable stall warning, initial buffet or stick shaker.
Lateral and Directional Control
Lateral control is maintained with ailerons. Rudder control should not be used because it causes yaw and the resultant roll is undesirable.
Effect of Flaps
Flaps are used to increase low speed performance capability. The leading edge devices ensure that the inboard wing stalls prior to the outboard wing. This causes the nose of the airplane to pitch down at the onset of the stall.
Effect of Speedbrakes
For any airspeed, the angle of attack is higher with speedbrakes up. This increases initial buffet speed and stick shaker speed but has a lesser effect on actual stall speed.
Entry
To save time, thrust levers may be closed to allow a more rapid deceleration. Target thrust for the configuration should be set approaching selected speed.
Some thrust is used during entry to provide positive engine acceleration for the recovery. The airplane is maintained in trim while decelerating. Level flight or a slight rate of climb is desired.
Landing Gear
If the entry has been made with the landing gear extended, do not retract it until after the recovery.
Flaps
Do not retract flaps during the recovery. Retracting the flaps from the landing position, especially when near the ground, causes an altitude loss during the recovery.
Recovery
Recover from approach to a stall with one of the following recommended recovery techniques.
Ground Contact Not a Factor
At the first indication of stall (buffet or stick shaker) smoothly apply maximum thrust, smoothly decrease the pitch attitude to approximately 5 degrees above the horizon and level the wings. As the engines accelerate, counteract the nose up pitch tendency with positive forward control column pressure and nose down trim. (At altitudes above 20,000 feet, pitch attitudes of less than 5 degrees may be necessary to achieve acceptable acceleration.)
Accelerate to maneuvering speed and stop the rate of descent. Correct back to the target altitude.
Ground Contact a Factor
At the first indication of stall (buffet or stick-shaker) smoothly advance the thrust levers to maximum thrust and adjust the pitch attitude as necessary to avoid the ground. Simultaneously level the wings. Control pitch as smoothly as possible. As the engines accelerate, the airplane nose pitches up. To assist in pitch control, add more nose down trim as the thrust increases. Avoid abrupt control inputs that may induce a secondary stall. Use intermittent stick shaker as the upper limit for pitch attitude for recovery when ground contact is a factor.
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本文链接地址：757 Flight Crew Training Manual 机组训练手册(79)
