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useable fuel limit, and similar items. The Glider Flight
Manual (GFM) or Pilot’s Operating Handbook (POH)
provides useful information about recommended
power settings and target airspeed for best angle of
climb, best rate-of-climb, best cooling performance
climb, and level flight cruise operation while under
power. If full-throttle operation is time limited to
reduce engine wear, the GFM/POH describes the recommended
operating procedures. Aircraft performance
limits include weight and balance limits,
minimum and maximum front seat weight restrictions,
maximum permitted airspeed with engine extended,
maximum airspeed to extend or retract the engine, flap
operating airspeed range, airbrake operating airspeed
range, maneuvering speed, rough air speed limitations,
and never exceed speed.
The engine heats up considerably during takeoff and
climb, so cooling system mismanagement or failure
can lead to dangerously high temperatures in a short
time. An overheated engine cannot supply full power,
meaning climb performance will be reduced. Extended
overheating can cause an in-flight fire. To minimize
the chances of engine damage or fire, monitor engine
temperatures carefully during high power operations,
and observe the engine operating limits described in
the GFM/POH.
Many self-launch gliders have a time limitation on full
throttle operation to prevent overheating and premature
engine wear. If the self-launch glider is equipped with
cowl flaps for cooling, make certain the cowl flaps are
set properly for high-power operations. In some selflaunch
gliders, operating at full power with cowl flaps
closed can result in an overheated, ruined engine in as
little as 2 minutes. If abnormally high engine system
temperatures are encountered, follow the procedures
described in the GFM/POH. Typically, these require
reduced power along with higher airspeed to enhance
engine cooling. Cowl flap instructions may be provided
as well. If these measures are ineffective in reducing
high temperatures, the safest course of action may be to
shut down the engine and make a precautionary landing.
A safe landing, whether on or off the airport, is
always preferable to an in-flight fire.
Handling limitations for a given self-launch glider
may be quite subtle and may include minimum controllable
airspeed with power on, minimum controllable
airspeed with power off, and other limitations
described in the GFM/POH. Self-launch gliders come
in many configurations. Those with a top-mounted
retractable engine and/or propeller have a thrust line
that is quite distant from the longitudinal axis of the
glider. The result is that significant changes of power
settings tend to cause substantial pitch attitude
changes. For instance, full power setting in these selflaunch
gliders introduces a nose-down pitching
moment because the thrust line is high above the longitudinal
axis of the glider. To counteract this pitching
moment, the pilot should hold the control stick back.
If power is quickly reduced from full power to idle
power while the control stick is held steady, these gliders
tend to pitch up considerably. The nose-up pitching
moment may be vigorous enough to induce a stall!
During climb-out, the pilot should hold a pitch attitude
that results in climbing out at the desired airspeed,
adjusting elevator trim as necessary. Climbs in selflaunch
gliders are best managed with smooth control
inputs and, when power changes are necessary, smooth
and gradual throttle adjustments.
When climbing under power, most self-launch gliders
exhibit a left- or right-turning tendency (depending on
whether the propeller is turning clockwise or counterclockwise)
due to P-factor. P-factor is caused by the
uneven distribution of thrust caused by the difference
in the angle of attack of the ascending propeller blade
and the descending propeller blade. Use the rudder to
counteract P-factor during climbs with power.
Turns are accomplished with a shallow bank angle
because steep banks result in a much-reduced rate of
climb. As with all turns in a glider, properly coordinating
aileron and rudder results in more efficient flight
and a faster climb rate. The pilot should clear for other
air traffic before making any turn.
Detailed engine shutdown procedures are described in
the GFM/POH. A guide to shutdown procedures is
described below, but the GFM/POH is the authoritative
source for any self-launch glider.
Engines reach high operating temperatures during
extended high-power operations. To reduce or elimi7-
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Glider Flying Handbook(68)
