Flare and Touchdown
These techniques discussed are applicable to all landings including crosswind landings and slippery runway conditions. Unless an unexpected or sudden event occurs, such as windshear or collision avoidance situation, it is not appropriate to use sudden, violent or abrupt control inputs during landing. Begin with a stabilized approach on speed, in trim and on glide path.
When the threshold passes under the airplane nose and out of sight, shift the visual sighting point to the far end of the runway. Shifting the visual sighting point assists in controlling the pitch attitude during the flare. Maintaining a constant airspeed and descent rate assists in determining the flare point. Initiate the flare when the main gear is approximately 20 feet above the runway by increasing pitch attitude approximately 2° - 3°. This slows the rate of descent.
After the flare is initiated, smoothly retard the thrust levers to idle, and make small pitch attitude adjustments to maintain the desired descent rate to the runway. Ideally, main gear touchdown should occur simultaneously with thrust levers reaching idle. A smooth power reduction to idle also assists in controlling the natural nose-down pitch change associated with thrust reduction. Hold sufficient back pressure on the control column to keep the pitch attitude constant. A touchdown attitude as depicted in the figure below is normal with an airspeed of approximately VREF plus any gust correction.
Note: Do not trim during the flare or after touchdown. Trimming in the flare increases the possibility of a tailstrike.
Landing Flare Profile
The following diagrams use these conditions:
.
3° approach glide path
.
flare distance is approximately 1,000 to 2,000 feet beyond the threshold
.
typical landing flare times range from 4 to 8 seconds and are a function of approach speed
.
airplane body attitudes are based upon typical landing weights, flaps 30, VREF 30 + 5 (approach) and VREF 30 + 0 (landing), and should be reduced by 1° for each 5 knots above this speed.
Typically, the pitch attitude increases slightly during the actual landing, but avoid over-rotating. Do not increase the pitch attitude after touchdown; this could lead to a tail strike.
Shifting the visual sighting point down the runway assists in controlling the pitch attitude during the flare. A smooth power reduction to idle also assists in controlling the natural nose down pitch change associated with thrust reduction. Hold sufficient back pressure on the control column to keep the pitch attitude constant.
Avoid rapid control column movements during the flare. Do not use pitch trim during flare or after touchdown. Such actions are likely to cause the pitch attitude to increase at touchdown and increase the potential for a tailstrike. Do not allow the airplane to float; fly the airplane onto the runway. Do not attempt to extend the flare by increasing pitch attitude in an attempt to achieve a perfectly smooth touchdown. Do not attempt to hold the nose wheel off the runway.
Bounced Landing Recovery
If the airplane should bounce, hold or re-establish a normal landing attitude and add thrust as necessary to control the rate of descent. Thrust need not be added for a shallow bounce or skip. When a high, hard bounce occurs, initiate a go-around. Apply go-around thrust and use normal go-around procedures. Do not retract the landing gear until a positive rate of climb is established because a second touchdown may occur during the go-around.
Bounced landings can occur because higher than idle power is maintained through initial touchdown, disabling the automatic speedbrake deployment even when the speedbrakes are armed.
Normal Touchdown Attitude
The following figures illustrate the effect of airspeed on body attitude on touchdown. It shows normal touchdown attitude for flaps 30. If flare control and thrust are excessive near touchdown, the airplane tends to float in ground effect.
With proper airspeed control and thrust management, touchdown occurs at no less than VREF - 5. The illustration shows that touchdown at a speed significantly below VREF seriously reduces aft fuselage-runway clearance.
Touchdown Body Attitudes
757-200
757-300
Body Clearance at Touchdown
The following figures show aft fuselage-runway clearance in relation to pitch angle with all main gear tires on the runway.
Body Clearance above Ground
757-200
Pitch Angle (Degrees)
14 12 10 8 6 4 2 0 0 20 40 60 80 100 120 140
MainGearStrutsExtended MainGearStrutsCompres
ed
(0) (51) (102) (152) (203) (254) (305) (356) Clearance - inches (cm)
757-300
Pitch Angle (Degrees)
14 12 10 8 6 4 2 0 0 20 40 60 80 100 120 140
Exte Aft Bodynde d Tail Ski d
T ail S trike Pro ximity
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本文链接地址：757 Flight Crew Training Manual 机组训练手册(69)
