曝光臺 注意防騙 網(wǎng)曝天貓店富美金盛家居專營店坑蒙拐騙欺詐消費者

approach airspeed and steepen the approach path.
[Figure 8-32] When the proper approach path has been
intercepted, adjust the power as required to maintain a
Figure 8-31. Right and wrong methods of correction for low final approach.
8-27
Normal Approach Path
Add Power
Nose Up
Hold Altitude
Wrong (Dragging it in with
High Power / High Pitch Altitude)
Intercept Normal Glidepath
Resume Normal Approach
Ch 08.qxd 5/7/04 8:08 AM Page 8-27
PDF Create! 5 Trial
www.nuance.com
stabilized approach. When steepening the approach
path, however, care must be taken that the descent does
not result in an excessively high sink rate. If a high sink
rate is continued close to the surface, it may be difficult
to slow to a proper rate prior to ground contact. Any
sink rate in excess of 800 - 1,000 feet per minute is considered
excessive. A go-around should be initiated if
the sink rate becomes excessive.
SLOW FINAL APPROACH
When the airplane is flown at a slower-than-normal
airspeed on the final approach, the pilot’s judgment of
the rate of sink (descent) and the height of roundout
will be difficult. During an excessively slow approach,
the wing is operating near the critical angle of attack
and, depending on the pitch attitude changes and control
usage, the airplane may stall or sink rapidly, contacting
the ground with a hard impact.
Whenever a slow-speed approach is noted, the pilot
should apply power to accelerate the airplane and
increase the lift to reduce the sink rate and to prevent
a stall. This should be done while still at a high
enough altitude to reestablish the correct approach
airspeed and attitude. If too slow and too low, it is
best to EXECUTE A GO-AROUND.
USE OF POWER
Power can be used effectively during the approach and
roundout to compensate for errors in judgment. Power
can be added to accelerate the airplane to increase lift
without increasing the angle of attack; thus, the descent
can be slowed to an acceptable rate. If the proper
landing attitude has been attained and the airplane is
only slightly high, the landing attitude should be
held constant and sufficient power applied to help
ease the airplane onto the ground. After the airplane
has touched down, it will be necessary to close the
throttle so the additional thrust and lift will be
removed and the airplane will stay on the ground.
HIGH ROUNDOUT
Sometimes when the airplane appears to temporarily
stop moving downward, the roundout has been made
too rapidly and the airplane is flying level, too high
above the runway. Continuing the roundout would
further reduce the airspeed, resulting in an increase
in angle of attack to the critical angle. This would
result in the airplane stalling and dropping hard onto
the runway. To prevent this, the pitch attitude should
be held constant until the airplane decelerates enough
to again start descending. Then the roundout can be
continued to establish the proper landing attitude.
This procedure should only be used when there is
adequate airspeed. It may be necessary to add a slight
amount of power to keep the airspeed from decreasing
excessively and to avoid losing lift too rapidly.
Although back-elevator pressure may be relaxed
slightly, the nose should not be lowered any perceptible
amount to make the airplane descend when fairly
close to the runway unless some power is added
momentarily. The momentary decrease in lift that
would result from lowering the nose and decreasing
the angle of attack may be so great that the airplane
might contact the ground with the nosewheel first,
which could collapse.
When the proper landing attitude is attained, the airplane
is approaching a stall because the airspeed is
decreasing and the critical angle of attack is being
approached, even though the pitch attitude is no longer
being increased. [Figure 8-33]
It is recommended that a GO-AROUND be executed
any time it appears the nose must be lowered significantly
or that the landing is in any other way uncertain.
Figure 8-32. Change in glidepath and increase in descent rate for high final approach.
No Flaps
Full Flaps
Steeper Descent Angle
Increased Rate of Descent
8-28
Ch 08.qxd 5/7/04 8:08 AM Page 8-28
PDF Create! 5 Trial
www.nuance.com
8-29
LATE OR RAPID ROUNDOUT
Starting the roundout too late or pulling the elevator
control back too rapidly to prevent the airplane from
touching down prematurely can impose a heavy load
factor on the wing and cause an accelerated stall.
　
中國航空網(wǎng) www.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：AIRPLANE FLYING HANDBOOK 飛機飛行手冊上(99)