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high altitude wave activity. Although autothrottle logic provides for more
aggressive control of speed as the airplane approaches VMO or MMO, there are
some windshears and wave activity speed changes that are beyond the capability
of the autothrottle system to prevent short term overspeeds.
When correcting an overspeed during cruise at high altitude, avoid reducing thrust
to idle which results in slow engine acceleration back to cruise thrust and may
result in overcontrolling the airspeed or a loss of altitude. If autothrottle
corrections are not satisfactory, temporarily deploying partial speedbrakes can
assist in reducing speed and avoiding the need for idle thrust.
During descents at or near VMO/MMO, most overspeeds are encountered after
the autopilot initiates capture of the VNAV path from above or during a level-off
when the speedbrakes were required to maintain the path. In these cases, if the
speedbrakes are retracted during the level-off, the airplane can momentarily
overspeed. During descents using speedbrakes near VMO/MMO, delay retraction
of the speedbrakes until after VNAV path or altitude capture is complete. Crews
routinely climbing or descending in windshear conditions may wish to consider a
5 to 10 knot reduction in climb or descent speeds to reduce overspeed occurrences.
This will have a minimal effect on fuel consumption and total trip time.
When encountering an inadvertent overspeed condition, crews should leave the
autopilot engaged unless it is apparent that the autopilot is not correcting the
overspeed. However, if manual inputs are required, disconnect the autopilot. Be
aware that disconnecting the autopilot to avoid or reduce the severity of an
inadvertent overspeed may result in an abrupt pitch change.
During climb or descent, if VNAV or FLCH pitch control is not correcting the
overspeed satisfactorily, switching to the V/S mode temporarily may be helpful in
controlling speed. In the V/S mode, the selected vertical speed can be adjusted
slightly to increase the pitch attitude to help correct the overspeed. As soon as the
speed is below VMO/MMO, VNAV or FLCH may be re-selected.
Note: Anytime VMO/MMO is exceeded, the maximum airspeed should be noted
in the flight log.
Tail Strike
777-200 - 777-300ER
Tail strike occurs when the lower aft fuselage or tail skid (as installed) contacts the
runway during takeoff or landing. A significant factor that appears to be common
is the lack of flight crew experience in the model being flown. Understanding the
factors that contribute to a tail strike can reduce the possibility of a tail strike
occurrence.
October 31, 2006
777/787 Flight Crew Training Manual
Non-Normal Operations
Copyright © The Boeing Company. See title page for details.
8.24 FCT 777/787 Preliminary (TM)
787-8
Tail strike occurs when the lower aft fuselage contacts the runway during takeoff
or landing. A significant factor that appears to be common is the lack of flight
crew experience in the model being flown. Understanding the factors that
contribute to a tail strike can reduce the possibility of a tail strike occurrence.
Note: Anytime fuselage contact is suspected or known to have occurred,
accomplish the appropriate NNC.
Takeoff Risk Factors
Any one of the following takeoff risk factors may precede a tail strike:
Mistrimmed Stabilizer
This usually results from using erroneous takeoff data, e.g., the wrong weights, or
an incorrect center of gravity (CG). In addition, sometimes accurate information
is entered incorrectly either in the flight management system (FMS) or set
incorrectly on the stabilizer. The flight crew can prevent this type of error and
correct the condition by challenging the reasonableness of the load sheet numbers.
Comparing the load sheet numbers against past experience in the airplane can
assist in approximating numbers that are reasonable.
Rotation at Improper Speed
This situation can result in a tail strike and is usually caused by early rotation due
to some unusual situation, or rotation at too low an airspeed for the weight and/or
flap setting.
Trimming during Rotation
Trimming the stabilizer during rotation may contribute to a tail strike. The pilot
flying may easily lose the feel of the elevator while the trim is running which may
result in an excessive rotation rate.
Excessive Rotation Rate
Flight crews operating an airplane model new to them, especially when
transitioning from an airplane with unpowered flight controls to one with
hydraulic assistance, are most vulnerable to using excessive rotation rate. The
amount of control input required to achieve the proper rotation rate varies from
　
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本文鏈接地址：787機組訓練手冊Flight Crew Training Manual 787(133)