Top Flite TOPA0145 - Manual (Page 4)

COMPETITION-MINDED MODELERS
We designed our P-39 Airacobra from scale three-
view drawings supplied by Scale Model Research
(address follows) and photos taken of various P-39
Airacobras. The scale of your Gold Edition P-39
Airacobra is 1 to 6.5.
If you plan to enter your P-39 Airacobra in scale
competition, this kit qualifies for Fun Scale and the
Sportsman and Expert classes in Sport Scale. Fun
Scale and Sport Scale have the same flight
requirements where you must perform ten maneuvers,
five of which are mandatory. The other five are up to
you–easy stuff like cycling your landing gear, a slow,
low "inspection pass" with flaps extended, or maybe a
touch-and-go. If you have never competed in a scale
contest, you could start out in Fun Scale. In Fun Scale,
the only documentation you need for static judging is
any proof that a full size aircraft of this type, in the
paint/markings scheme on your model, did exist. A
single photo, a kit box cover, even a painting is
sufficient proof! If you're interested, contact the AMA
for a rule book which will tell you everything you need
to know. Look in the back of the AMA magazine (Model
Aviation) for a schedule of events.
If you are not concerned with a scale trim scheme you
can make a variation of the one on the box, or design
your own. If you are going to compete in scale
competition use the photos in your documentation
package as a guide for your trim scheme.
DOCUMENTATION
Three view drawings and photo packs of full size
P-39 Airacobras are available from:
Scale Model Research
3114 Yukon Ave, Costa Mesa, CA 92626
(714) 979-8058
Fax: (714) 979-7279
SCALE ACCURACY
The Top Flite P-39 Airacobra is a faithful reproduction
of the full size aircraft, with a few exceptions:
1. The size of the horizontal stab / elevators has been
increased by about 10% to improve pitch stability.
2. The size of the vertical fin / rudder has been
increased by about 10% to improve yaw stability.
3. The position of the retractable landing gear has
been moved 1/2" [13mm] aft to allow a scale 4"
[100mm] wheel to clear the wing spar.
POWER
With the .61 2-stroke engine the model will fly very well.
The .61 will provide more power than the model needs
for a scale speed, but you will appreciate the extra
power when vertical maneuvers are being performed.
FLIGHT CHARACTERISTICS
During our flight testing we found no bad
characteristics in this airplane. Take-offs were
straightforward with good ground handling. The plane
was airborne in approximately 100' [30m]. Once the
plane is flying it goes exactly where you point it. Rolls
are very scale-like with the low rate settings. At high
rate it can roll more like an aerobatic sport plane.
Power-off stalls were very soft and predictable with
only the nose dropping in the stall. There was no
tendency for the plane to tip stall. Landings were
straightforward with or without the flaps. Without flaps
you should maintain a bit more airspeed on your
approach. With full flap deployment the plane slows
very nicely and allows for a very soft landing. Unlike
some models, the P-39 Airacobra does not exhibit
any pronounced ballooning when flaps are deployed.
A full flap landing will generally require a little steeper
approach than an approach without flaps. Try setting
up your approach from a slightly higher altitude than
you might typically use for a landing without flaps.
Deploy full flaps and gradually decrease the power.
Keep the nose down and maintain a consistent
approach to the beginning of the runway. When you
are over the runway threshold pull off all power and
the plane will settle in nicely to final touchdown. If you
have never flown with flaps this is an excellent
model to learn with. The extra effort to construct the
P-39 Airacobra with flaps is well worth the effort when
the model is completed.
Flaps
Your P-39 Airacobra is designed to incorporate
scale split flaps; however, flaps are optional and
not necessary for an excellent flying experience.
Without flaps, the takeoff roll is a bit longer and the
landing speed is slightly faster. If you do not wish
to build the flaps, just disregard parts of the
manual involving flap construction.
The flaps are not difficult to build, but they do
require good craftsmanship to fit and operate well.
Flaps add nicely to the model's flight characteristics
and scale appearance. Trim changes were not
needed for our prototype when flaps were
extended. The only exception was when they were
deployed when flying at full power. The trim
corrections are discussed later in the manual during
radio set up and you will find more information on
the use of the flaps in the flying section.
For flaps you will need one additional standard servo.
PROPELLERS
We did our test flying using Top Flite ® Power Point ™
Propellers and an OS .61FX engine. Initial test
flights were with the 12x6 and 12x8. As with any
model, you may experiment with different propellers
to find out what type and pitch works best for you.
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