|
Figure 1 depicts a plane with
tricycle or trike
gear. The rules of thumb for proper
set up are as follows. -The
wider the span between the two main
wheels the more stability
in a crosswind. -The main gear should be
just far enough behind
the cg to allow the plane to set on all
three wheels when at
rest. -The more distance between the nose gear
and main gear
the smoother a turn will be during taxi. The plane
should have
a slight nose high attitude when at rest.
Since the wide stance for crosswind stability is obvious we will
start with why the main gear is placed just behind the cg. In
figure 2 the main gear is far behind the cg. While ground handling
would be excellent in this set up, when it comes time for rotation
and take off 'look out'. Remembering that the plane will always
try
to rotate around the cg and the wheels are too far behind
the cg in
this example so the plane will be forced to rotate
at the gear
location for take off. A lot of ground speed will
have to be gained
to develop enough lift for the mass between
the gear and cg and too
much elevator deflection will be required
for rotation. This
combined will cause the the plane to pop into
the air unexpected
and the wing will have a high angle of attack
and probably result
in a high speed stall.
When landing the plane in figure 2 a
situation can develop which
was discussed with the conventional
gear plane except the trike
gear plane will hippity hop down the
runway bouncing between
the nose and main gear.
Taking
the above into consideration, the distance between the
main gear
and nose gear is pretty well dictated by the distance
between the
cg and nose of the airplane.
The reason for the slight nose
high attitude when at rest is
that it will put the wing at a
positive angle of attack to the
on coming air during take off roll.
As the plane gains speed
more and more lift is developed because of
this positive angle
of attack and when flying speed is achieved,
the plane will lift
off with little or no elevator application.
After lift off the
wing will start aligning itself with the on
coming air and the
plane will be near to straight and level flight
just above the
runway.
As you can see by these examples a
beautiful take off and landing
are evenly spread between pilot
skill and proper set up.
<---Back
to contents
|
