Dual Engine Failure
Dual engine failure is a situation that demands prompt action regardless of altitude or airspeed. Accomplish recall items and establish the appropriate airspeed to immediately attempt windmill restart. There is a higher probability that a windmill start will succeed if the restart attempt is made as early as possible (or immediately after recognizing engine failure) to take advantage of high engine RPM. Use of higher airspeeds and altitudes below 30,000 feet improves the probability of a restart. Loss of thrust at higher altitudes may require driftdown to lower altitude to improve windmill starting capability.
The inflight start envelope defines the region where windmill starts were demonstrated during certification. It should be noted that this envelope does not define the only areas where a windmill start may be successful. The dual engine failure checklist is written to ensure flight crews take advantage of the high RPM at engine failure regardless of altitude or airspeed. A subsequent APU start may be initiated as soon as practical for electrical power and starter assist start attempted if the rapid restart does not succeed. Initiate the rapid relight recall procedure before attempting an APU start for the reasons identified above.
EGT during rapid restart may exceed the limit displayed by EICAS for one-engine starts. During relight attempts with both engines failed, use the Standby Engine Indicator takeoff EGT placard limit even if EICAS remains powered. A hung or stalled in-flight start is normally indicated by stagnant RPM and/or increasing EGT. During start, engines may accelerate to idle slowly but action should not be taken if RPM is increasing and EGT is not near or rapidly approaching the SEI limit.
Note: When electrical power is restored, do not confuse the establishment of
APU generator power with airplane engine generator power at idle RPM
and advance the thrust lever prematurely.
Engine Severe Damage Accompanied by High Vibration
Certain engine failures, such as fan blade separation can cause high levels of airframe vibration. Although the airframe vibration may seem severe to the flight crew, it is extremely unlikely that the vibration will damage the airplane structure or critical systems. However, the vibration should be reduced as soon as possible by reducing airspeed and descending. As altitude and airspeed change, the airplane may transition through various levels of vibration. In general, vibration levels decrease as airspeed decreases; however, at a given altitude vibration may temporarily increase or decrease as airspeed changes.
If vibration remains unacceptable, descending to a lower altitude (terrain permitting) allows a lower airspeed and thus lower vibration levels. Vibration will likely become imperceptible as airspeed is further reduced during approach.
The impact of a vibrating environment on human performance is dependent on a number of factors, including the orientation of the vibration relative to the body. People working in a vibrating environment may find relief by leaning forward or backwards, standing, or otherwise changing their body position.
Once airframe vibration has been reduced to acceptable levels, the crew must evaluate the situation and determine a new course of action based on weather, fuel remaining, and available airports.
Flight Controls
For any flight control problem, consider the possibility of higher airspeed on approach, longer landing distance, and a different flare picture and landing technique.
For non-normal landings, position two white reference airspeed bugs at VREF and single white reference airspeed bugs at the flap 5 maneuvering speed and the flap up maneuvering speed.
Leading Edge or Trailing Edge Device Malfunctions
Leading edge or trailing edge device malfunctions can occur during extension or retraction. This section discusses all flaps up and partial or asymmetrical leading/trailing edge device malfunctions for landings.
All Flaps and Slats Up Landing
The probability of both leading and trailing edge devices failing to extend is remote. If a flaps up landing situation were to be encountered in service, the pilot should consider the following techniques. Training to this condition should be limited to the flight simulator.
After selecting a suitable landing airfield and prior to beginning the approach, consider reduction of airplane gross weight (burn off fuel) to reduce touchdown speed.
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本文链接地址：757 Flight Crew Training Manual 机组训练手册(88)
