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Why begin with a good basic trainer
design? It is possible to learn RC piloting on any type of model, but
sport or Scale aircraft react quickly to control inputs, leaving less
time for the new pilot to plan the next control inputs. Also, takeoff,
in-flight, and landing speeds can be higher with the more reactive
models.
Sport and Scale airplanes demand more from the pilot than most basic
trainers. In addition, their higher airspeeds and quicker control
responses mean that this "more from the pilot" must happen more quickly.
This requirement that the pilot be "further ahead of the airplane" makes
learning to fly RC with a sport airplane more difficult and time
consuming.
There are so many excellent sport ARF designs that make great advanced
trainers or second models that many new pilots want to use them as their
basic trainers. This is possible, but sport aircraft have certain
drawbacks in that capacity.
Although high-wing advanced trainers such as the Midwest Aerobat, which
is shown, may resemble basic trainers and even have similar wing
loadings (the weight each square foot of wing area must support), their
design criteria are different, as are their wings' airfoils.
The Aerobat and its cousins, which include Hobbico's Avistar, Hobby
Lobby's Bonnie 20, and Hangar 9's Arrow, feature symmetrical (or semisymmetrical) wing airfoils that have less lift than equivalent
flat-bottom trainer airfoils. I will explain why shortly. A symmetrical
wing is curved equally on the top and bottom, and a semisymmetrical wing
is curved on the bottom but more so on the top.
The symmetrical wing allows for easy inverted flight, Outside Loops
(loops with the airplane upside-down, performed using down-elevator),
faster aileron response, and good Snap Roll/Spin performance. But
landing speeds are higher and the symmetrical-airfoil wing is more
responsive, making these second aircraft sensitive to control inputs.
The symmetrical airfoil actually has slightly less air drag than an
equivalent flat-bottom wing. This means that the aircraft gains more
airspeed than a basic trainer if the student pilot lets the nose drop in
a turn. Aerobatic trainers will not "balloon" as much (raise the nose
and climb) in this situation as basic trainers would. That is a plus for
them.
However, the increasingly rapid descent in the turn usually causes the
new pilot to input substantial up-elevator, causing the aircraft to
rocket upward or tighten the radius of the turn. Learning to make level
turns is the first step in becoming an RC pilot, and aerobatic trainers
make that more difficult.
These second airplanes are designed to take a newly soloed pilot beyond
basic flight and into the exciting world of aerobatic flying—not to be
the best basic trainer.
Some Scale aircraft would seem to be ideal basic trainers and do use
flat-bottom airfoils, but they are better suited as second models. The
Piper Cub, for instance, is extremely short coupled; the tail is close
to the wing, given its wing's large span and width (wing chord). Without
perfectly set aileron differential, one aileron moves upward much
farther than the other moves downward, and the Cub needs coordinated
rudder/aileron input to make proper turns. Coordinated turns and aileron
differential can be daunting for most new RC pilots and is seldom
necessary in a basic trainer.
The Cub's short fuselage and narrow landing gear make ground handling
troublesome for new pilots. Its light wing loading and large wingspan
compound landing difficulties because the aircraft tends to land on the
main gear and keep the tail up. This usually means that the wing drops
to one side, pulling the aircraft off in that direction, or the model
ends up on its back.
Yes, a new pilot can begin on a Cub or similar Scale model,
but learning is easier on a basic trainer that is designed expressly for
teaching RC piloting.
Click on photo to view large image with caption
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