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opposite. Technical Editor's Note: Torque causes the
airframe to rotate opposite of the propeller, therefore,
right-thrust would have no effect on torque reaction. In
fact, most aircraft have their engines set at zero right or
left thrust. The turning effect that torque is blamed for
happens on the ground at relatively slow speeds. Some
claim that the turning effect is due to the P-factor ( or P-
effect), but that claim runs into large difficulties when you
consider that the tricycle geared airframes (the full sized
P-38, for example, before the rotation of one of the
engines is changed) shows the same tendency to turn right
under power while still on the ground.
The flight effects of changes in these Fab Five are
contingent upon whether airframe was been built and
assembled straight and true. A slightly warped wing,
cocked rudder, twisted fuselage, etc., can cause similar
effects and make it difficult to achieve a well-mannered,
predictable model in flight. And everything is a trade-off.
Changing one thing will often require changing something
else. Be prepared for a lot of checking, trial and error. A
good performing plane with no bad habits is worth the
effort. It makes flying enjoyable.
from the Aero RC Club of Flint's newsletter, Flint MI
Tip-to-tip balance
It is either good or it isn’t. You may need help from
another person to check it. Hold the front by the spinner
or propeller shaft and the rear at the center of the
fuselage. It may help to insert a pin or hook at the rear to
aid in suspending the airplane. High wingers should be
held upside-down. If either wing drops, add weight to the
opposite wingtip until balanced. A heavy wing condition
will cause the ailerons to trim with one up and one down.
Fore-to-aft balance
The airplane should balance at a point about 25 to 35%
back from the LE of the wing. This is the envelope or
range of balance that will provide safe, controllable flight.
A tail heavy airplane is unstable in flight, difficult to
control, and if excessively tail heavy, it can be unsafe—a
danger to persons and property.
A nose-heavy airplane may be difficult to trim in flight,
drop the nose when power is reduced, and require a lot
of down elevator when inverted. It’s better to be a bit
nose heavy, however, than the opposite. Flight testing
will determine if a change in balance is desired.
Wing incidence
It is normally a few degrees “positive” for sport flying. This
means the LE of the wing is higher than the trailing edge
in reference to the plane of the elevator. You can hold a
straight edge on top of the elevator surface and draw a
line along the fuselage with an erasable pen as a
reference line. Then measure from this line to the E and
TE to find the incidence. You can plot this on paper and
measure the angle.
Flight performance will indicate if a change is necessary.
Too much positive will make the airplane climb as power
is added, zoom upward when pulling out of a dive, and
tend to climb when turning. Negative, or too little positive
incidence, causes a diving tendency throughout flight.
Engine thrust up or down
A small amount of engine down thrust is common in sport
models. It helps to counteract the climbing effect of
positive wing incidence as power is added without
affecting the glide angle at low throttle. Too much down
thrust may require excessive up trim for level flight, and
may cause the model to nose up when power is cut. Up
thrust will cause the opposite of these.
Engine thrust right or left
Some right engine thrust, usually two or three degrees, is
essential to counteract the torque of the engine. If there is
too little right thrust, the model will pull to the left as it
loses speed in a steep climb. It will also pull to the left at
the top of a loop. Too much right thrust will cause the