Test flights of the Xtreme A.R.F. F- 100 were easy because the kit came with good control throw
and CG recommendations. Stick to the suggested settings and test flights should go well.
The BobCat XL is a
but be aware that on
test flights, even the
most unusual things
can fail. The elevator
hinges pulled out
because the epoxy
failed to fully cure. It
survived to fly again.
Finding the right setup
by Jim Hiller
It’s getting close to that time again—time for pilots to test-fly new jet models that hey have built for this season. The setup routine also begins again. This will be my second time setting up an Xtreme A.R.F. Vixen. The last one
was a prototype. This time I know the center of gravity (CG) and control throws
that I want, which lowers my stress level.
When setting up a new model for its maiden flight, aircraft manufacturers often
suggest which control throws to use and the CG location. I hope these numbers
are based on a good setup developed by a qualified pilot. I have test-flown many
airplanes with good setup numbers, and when the setup of the model is matched to
those figures, I get straightforward test flights.
The problem is that not all manufacturers have accurate setups—only those that
are close enough to get you through a test flight. This depends on the knowledge of
the pilot used to determine the recommended setup.
I cannot say enough about the
importance of getting the CG correct.
Any extra weight is worth it to get the
balance in the correct spot.
Throughout the last few years, I have
test-flown several prototypes, and for
some reason, several of them started
tail-heavy. It’s an annoying situation,
but one that can be dealt with if proper
control throws are available.
A tail-heavy airplane can be flown if
you make a smooth takeoff and don’t
force the model off of the ground
early. Make sure you have plenty of
speed before lifting off.
The problem with a tail-heavy
airplane is landing. As it slows on the
final approach, the tail will continue to
drop and the airplane will reach slow
speeds and possibly even stall, fall to the
ground, and wipe out the landing gear.
I’ve seen this with modern jet setup
recommendations that were established
with an emphasis on maneuverability,
not friendly flying.
A nose-heavy model requires a lot
of pull on the elevator to lift off. After
liftoff, the excess elevator often results in
a snap roll on takeoff. Sure this setup is
smooth, but when it comes time to land,
the nose-heavy condition can leave you
with another problem: a shortage of up-elevator travel to hold the nose up.
Some models require additional
weight to get the CG correct. Scale
models of the de Havilland Vampire,
for example, often require nose weight.
Proper CG is important and the extra
weight has minimal effects on the flying
Sometimes, additional tail weight is
necessary. I have two jets in my fleet to
which I had to add tail weight to get the
CG right. Putting in the effort to get the
balance right pays off with easier test
Next is control throw setup.
should be your starting point. With some
manufacturers, the recommendations
are more than safe suggestions—they are
actually top-quality numbers established
to get the best flying setup for that
Which models come with well-developed setup recommendations? Get
to know the kit manufacturers—those
that fly their
those that sell
what comes out of
109 Model Aviation MARCH 2016 www.ModelAviation.com