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aircraft strikes the runway nose fi rst with suffi cient force
to collapse the nose gear. Pilot attempts to correct a severe
porpoise with fl ight control and power inputs will most
likely be untimely and out of sequence with the oscillations,
only making the situation worse. No attempt to salvage the
landing should be made. Full power should be applied while
simultaneously maintaining directional control and lowering
the nose to a safe climb attitude.
11-30
Wing Rising After Touchdown
In all the proper landing techniques except the soft fi eld, the
nose is lowered after the front wheel touches to put a negative
AOA on the wing and keep the WSC aircraft on the ground.
However, there may be instances when landing in a crosswind
that a wing wants to rise during the after-landing roll. This
may occur whether or not there is a loss of directional control
depending on the amount of crosswind and the degree of
corrective action.
Any time an aircraft is rolling on the ground in a crosswind
condition, the upwind wing is receiving a greater force
from the wind than the downwind wing. This causes a lift
differential. Also, as the upwind wing rises, there is an
increase in the AOA which increases lift on the upwind wing
rolling the aircraft downwind.
When the effects of these two factors are great enough, the
upwind wing may rise even though directional control is
maintained. If no correction is applied, it is possible that the
upwind wing rises suffi ciently to cause the downwind wing
to strike the ground.
In a crosswind, the windward wing should be lowered
slightly as a preventive measure to avoid it from lifting. But
in the event a wing starts to rise during the landing roll, the
pilot should immediately lower the nose while lowering the
wing. The wing should be lowered as soon as possible. The
further a wing is allowed to rise before taking corrective
action, the more wing surface is exposed to the force of the
crosswind.
Hard Landing
When the aircraft contacts the ground during landings, its
vertical speed is instantly reduced to zero. Unless provisions
are made to slow this vertical speed and cushion the impact
of touchdown, the force of contact with the ground may be
so great it could cause structural damage to the aircraft.
The purpose of pneumatic tires, shock-absorbing landing
gears, and other devices is to cushion the impact and to
increase the time in which the aircraft’s vertical descent is
stopped. The importance of this cushion may be understood
from the computation that a 6-inch free fall on landing is
roughly equal to a descent of 340 feet per minute. Within a
fraction of a second, the aircraft must be slowed from this
rate of vertical descent to zero without damage.
During this time, the landing gear together with some aid from
the lift of the wings must supply whatever force is needed
to counteract the force of the aircraft’s inertia and weight.
The lift decreases rapidly as the aircraft’s forward speed is
decreased and the force on the landing gear increases by the
impact of touchdown. When the descent stops, the lift is
almost zero leaving only the landing gear to carry both aircraft
weight and inertia force. The load imposed at the instant
of touchdown may easily be three or four times the actual
weight of the aircraft, depending on the severity of contact.
After a hard landing, the WSC carriage and wing should be
inspected by qualifi ed personnel for airworthiness.
Chapter Summary
All landings should consist of evaluating the wind and
conditions so a proper base and fi nal are planned to land at
or beyond the intended point. After the fi nal approach to the
runway, the roundout is started about 10 to 15 feet high and
is a gradual descent until the rear wheels are inches above
the surface. The rotation is continued as the speed bleeds off
to maintain the wheels one to two inches above the runway
until minimum controlled airspeed at which the WSC aircraft
settles to the ground. A roundout that is too fast, or ballooning
where altitude is gained during the landing, is a common
mistake and should be avoided.
The best landing technique for light wind conditions is with
power brought to idle during the downwind leg of the pattern
before the turn to base. Profi ciency in power-off accuracy
landings with 90° turns, 180° turns, 360° turns, and circling
from above are all important safety procedures.
Crosswinds or landing in turbulence requires more energy,
including power-on approaches with higher airspeeds.
In these conditions, the WSC aircraft can be fl own into
　
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本文鏈接地址：Weight-Shift Control Aircraft Flying Handbook(133)