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• During the takeoff roll, the weathervaning tendency,
although present, is much less due to
the rapid acceleration to liftoff airspeed.
• After liftoff, the glider tends to drift toward
the downwind side of the runway. The
stronger the crosswind, the greater the glider’s
tendency to drift downwind.
After liftoff, the glider pilot should establish a wind
correction angle toward the upwind side of the runway
to prevent drifting downwind. This prevents downwind
drift and allows the glider to work upwind of the
runway during the climb-out. When the towline is
released at the top of the climb, it will tend to drift back
toward the centerline of the launch runway, as shown
in Figure 7-19 on the next page. This helps keep the towline
from fouling nearby wires, poles, fences, aircraft,
Start Rotation
200 ft. AGL
Deck Angle
Fully Established
Launch is Nearing
Maximum Prudent Height
Release Imminent
Figure 7-18. Ground launch takeoff profile.
7-16
and other obstacles on the side of the launching runway.
Should the glider drift to the downwind side of
the runway, the towline may damage items, such as
other aircraft, runway lights, nearby fences, structures,
and obstacles.
GROUND TOW LAUNCH—
CLIMB-OUT AND RELEASE PROCEDURES
The pitch attitude/airspeed relationship during ground
launch is unique. During the launch, pulling back on the
stick tends to increase airspeed, and pushing forward
tends to reduce airspeed. This is opposite of the normal
pitch/airspeed relationship. The wings of the glider
divert the towing force of the launch vehicle in an
upward direction, enabling rapid climb. The greater the
diversion from horizontal pulling power to vertical lifting
power, the faster the airspeed. This is true, provided
the tow vehicle is powerful enough to meet the energy
demands the glider is making on the launch system.
COMMON ERRORS
• Improper glider configuration for takeoff.
• Improper initial positioning of flight controls.
• Improper use of visual launch signals.
• Improper crosswind procedure.
• Improper climb profile.
• Faulty corrective action for adjustment of air
speed and porpoising.
• Exceeding maximum launch airspeed.
• Improper towline release procedure.
ABNORMAL PROCEDURES, GROUND LAUNCH
The launch equipment operator manages ground
launch towline speed. Because the launch equipment
operator is remote from the glider, it is not uncommon
for initial tow speed to be too fast or too slow. If the
towline speed is too fast, the glider will not be able to
climb very high because of excessive airspeed. If the
towline speed is too slow, the glider may be incapable
of liftoff, possibly stall after becoming airborne or
once airborne be incapable of further climb. The pilot
should use appropriate signals to direct the launch
operator to increase or decrease speed. The pilot must
anticipate and be prepared to deal with these situations.
In the event these abnormal situations develop,
the pilot’s only alternative may be to release the towline
and land straight ahead.
Wind gradient (a sudden increase in wind speed with
height) can have a noticeable effect on ground
launches. If the wind gradient is significant or sudden,
or both, and the pilot maintains the same pitch attitude
the indicated airspeed will increase, possibly exceeding
the maximum ground launch tow speed. The pilot
must adjust the airspeed to deal with the effect of the
gradient. When encountering a wind gradient the pilot
should push forward on the stick to reduce the indicated
airspeed. [Figure 7-20] The only way for the
glider to resume climb without exceeding the maximum
ground launch airspeed is for the pilot to signal
the launch operator to reduce tow speed. After the
reduction of the towing speed, the pilot can resume
normal climb. If the tow speed is not reduced, the
glider may be incapable of climbing to safe altitude.
Ground launch may be interrupted by a ground launch
mechanism malfunction. Agradual deceleration in rate
of climb and/or airspeed may be an indication of such
a malfunction. If you suspect a launch mechanism
malfunction, release and land straight ahead.
EMERGENCY PROCEDURES—
GROUND LAUNCH
The most common type of problem is a broken towline.
[Figure 7-21] When there is a towline failure, the
Crab into crosswind during ground tow climb-out. Towline
will drift toward runway centerline after release.
Figure 7-19. Ground launch crosswind drift correction.
　
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本文鏈接地址：Glider Flying Handbook(65)