Flaperons

The Mosquito (glider) has an unusual arrangement, not flaperons, but quite
related.
The ailerons and flaps move together when commanded by one lever. That's
quite common on 15meter ships. The ailerons move independently of the flaps
for aileron control. When you pull a different lever, for airbrake, the
flaps deflect
downward and a spoiler comes up (the spoiler is hinged at it's trailing edge
and
actually pushes the flap down) but the ailerons do not move. Then you can
move
the ailerons up and down in unison with the lever that I first mentioned
while at
the same time can be moved like normal ailerons. The ailerons have
differential
as well, more up than down. It is quite a system. The drag range is very
large.
The stall speed is hardly changed at all between flaps up and down.
Typically
I will takeoff with the flaps and ailerons full up. It makes a distinct
difference in
roll authority. After landing the first order of business is to get the
ailerons up
for this better aileron authority. By modulating the flaps/speed brake you
can
control your landing roll considerably (on hard surface). I must note - just
because the stall speed doesn't change much with speed brakes it doesn't
mean that the lift isn't changed much. The way we do stalls is not measuring
your descent rate, it is measuring the speed at which you lose the ability
to
control the aircraft.


Nils Rostedt wrote in message ...
"Lou Parker" wrote in message
. com...
I just don't get it. Can anyone successfully explain how flaperons
work? Are they better or worse than seperate flaps? What are the pro's
and con's? It seems to me if one fails you have no recovery.
Lou

I'll try ;-)

Flaperons are control surfaces that look like full span ailerons. They work
both as ailerons (i.e. move in opposite directions when the stick is moved)
and as flaps (i.e. move in the same direction when the flap handle is
moved).
There is a mechanical "mixer" device connected to the stick and flap handle
that transmits the movement to the control surfaces so that they move as
described above.

The advantage, in theory, is that you can have effective, full span
ailerons
at the same time with effective full span flaps that can bring the stall
speed down. To get the same effect with conventional control surfaces, the
flaps need to be of more exotic design such as the split or Fowler type
flaps.

The main disadvantage is that when the flaps are in use you get an
increased
adverse yaw moment, which may make steering more difficult during approach.
Also, as the flap deflection angle is limited compared to conventional
flaps, the drag increase (speedbrake effect) is smaller. This means the
airplane floats longer in ground effect on landing, making short field
landings more difficult.

A pilot friend had a Rans S-10 Sakota with flaperons. He told me he rarely
used the flap function, preferring to sideslip on approach.

The French DynAero MCR-01 high performance plane (Ban-Bi in the US) was
originally designed (in the microlight/UL version) with double slotted
flaperons to comply with the stall speed requirement of 35 knots (65 km/h)
even with a very small wing area. After a few years, they were able to
tweak
the wing design to fulfil the stall speed requirement also with a
conventional arrangement with ailerons and double slotted flaps, and this
is
the current configuration.

A number of airplanes (gliders in particular) have ailerons which are
connected with the flaps and move with them. In these planes, the main idea
is to be able to reduce drag with negative deflection of the ailerons
together with the flaps. But I'd hesitate to call them flaperons in this
case, where the wing also has separate flaps.

Please correct me if I got something wrong, my practical exeprience of
flaperons is limited to radio controlled model airplanes ;-)
// N