Q-116: I’ve heard that operating flaps can be added to model
aircraft and that they can provide roughly the same advantages they do on
full-scale aircraft, namely provide more lift at low flying speeds, especially
when landing.
Being pretty much a beginner in the RC hobby I would like try flaps to possibly
make my landing approaches easier (slower) for me.
A-116: Operating (or deployable) flaps have been used on RC models for
years, with considerable success. The flaps are located inboard of the regular
aircraft ailerons. The ailerons produce the model’s roll motion by banking it
left or right. Concurrent with that “roll action,” the inboard flaps can be
deployed to add lift to the wing, allowing the airplane to be slowed more than
normal, without stalling.
Adding operating flaps to your airplane will take additional time and result in
some added complexity. You will need an extra channel function on your RC
transmitter and receiver, along with an extra servo to work the flaps.
Then you must decide how far you want to drop, or deploy, the flaps. If there is
too much downward angle, your model will tend to pitch down. That pitch-down
(nose-down) tendency must be immediately compensated for with up-elevator
control at the time of flap deployment. The farther down you drop the flaps, the
more elevator compensation you will need.
I recently reviewed the electric-powered Hobby Lobby Lipol-One ARF that features
inboard operating flaps. (You can find the complete article on AMA’s online
magazine Sport Aviator at www.sportaviator.com.) I’m including several photos
showing how the flap servo can easily be added to your aircraft.
You can use an auxiliary proportional control channel on your transmitter to
operate the flaps. Doing that, you will be able to position them to any angle
you want, from 0° downward to 45° or 50°. If you choose to use the retract
channel switch, as I did, the flaps simply deploy to their maximum position. You
get nothing in between, but even that is worth the extra effort.
If you own a computer-type transmitter and have a six-channel receiver, you can
try a variation of flap control known as “flaperons,” In this configuration, two
flap servos are employed. One is attached to each of the two flaps. The flaps in
this case are not confined to an inboard position but can be extended much
farther out on the wing. You end up with a combined aileron and flap function.
The transmitter is set for “flaperons.” When you move the aileron control stick,
the ailerons will work differentially, providing roll control to your airplane.
Moving an auxiliary channel lever on your transmitter will deploy both ailerons
downward; this creates a flap effect. Yet while doing this, the ailerons
continue to operate.
This scheme does work, although, admittedly, there are some limitations to how
far you can go with the aileron and flap functions. But added flap control can
provide considerable flying fun and is worth the extra effort and complexity to
install.