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in a nosewheel-equipped glider is to use the elevator
to lift the nosewheel off the runway as soon as practicable,
then set the pitch attitude so the glider’s main
wheel is the only wheel in contact with the ground. To
avoid porpoising during landing, hold the glider off
during the flare until the mainwheel and tailwheel
touch simultaneously. During rollout, use the elevator
to keep the nosewheel off the ground for as long as
possible.
TAILWHEEL/TAILSKID EQUIPPED GLIDER
OSCILLATIONS DURING LAUNCHES AND
LANDINGS
Some two-seat gliders, self-launch gliders, and singleseat
gliders have a tailwheel. When loaded and ready
for flight, these gliders have the mainwheel and the tailwheel
or tailskid in contact with the ground. In these
gliders, the center of gravity is aft of the main wheel(s).
Because of this, any upward thrust on the main landing
gear tends to pitch the nose of the glider upward unless
the tail wheel or tailskid is in contact with the ground
and prevents the change in pitch attitude.
Upward thrust on the main landing gear can occur in
numerous circumstances. One cause is a bump in the
runway surface during takeoff or landing roll. If the
resultant pitch-up is vigorous enough, it is likely that
the glider will leave the ground momentarily. If airspeed
is slow, the elevator control is marginal. As the
pilot reacts to the unexpected bounce or launch,
overcontrolling the elevator will result in a PIO.
[Figure 8-6]
Improper landing technique in a tailwheel glider also
can lead to upward thrust on the main landing gear and
subsequent PIOs. Landing a tailwheel glider in a nosedown
attitude, or even in a level pitch attitude, can lead
to trouble. If the main wheel contacts the ground
before the tailwheel or tailskid, the compression of
the pneumatic tire and its inevitable rebound will provide
significant upward thrust. The glider nose may
pitch up, the angle of attack will increase, and the
glider will become airborne. As before, overcontrol
of the elevator leads to PIOs.
To prevent this type of PIO, do not allow the glider to
settle onto the landing surface with a nose-down attitude
or with excess airspeed. During the landing flare,
hold the glider off a few inches above the ground with
gentle backpressure on the control stick as necessary.
The speed will decay and the pitch attitude will gradually
change to a slightly nose-up pitch attitude. The
ideal touchdown is simultaneous gentle contact of
main wheel and tailwheel or tailskid. Delaying the
touchdown just a small amount results in the tailwheel
or tailskid contacting the landing surface an instant
before the mainwheel. This type of landing is very
acceptable and desirable for almost all tailwheel gliders
because it makes a rebound into the air very
unlikely. Consult the GFM/POH for the glider being
flown for further information about recommended procedure
for touchdown.
OFF-FIELD LANDING PROCEDURES
Figure 8-5. Pitch attitude power setting relationships
for self-launch glider with engine pod.
Figure 8-6. Pneumatic tire rebound during hard landing.
8-8
The possibility of an off-field landing is present on virtually
every cross-country soaring flight, even when
flying in a self-launch glider. If the engine or power
system fails and there is no airport within gliding
range, then an off-field landing may be inevitable. It
should be noted that many glider pilots who were not
flying cross-country have faced the necessity of performing
an off-field landing. Root causes of off-field
landings while engaged in soaring in the vicinity of the
launching airport include rapid weather deterioration,
a significant change in wind direction, unanticipated
amounts of sinking air, disorientation, or lack of situational
awareness. In these situations, it usually is safer
to make a precautionary off-field landing than it is to
attempt a low, straight-in approach to the airport. If the
glide back to the airport comes up short for any reason,
the landing is likely to be poorly executed and may
result in damage to the glider or injury to the pilot.
On cross-country soaring flights, off-field landings are
not usually considered emergency landings. As a matter
of fact, they are expected and are considered while
preparing for flight. On the other hand, if equipment
failure leads to the necessity of performing an off-field
landing, then the landing can be characterized or
described as an emergency landing. Whatever the reason
for the off-field landing, each glider pilot must be
prepared at all times to plan and execute the landing
　
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本文鏈接地址：Glider Flying Handbook(92)