Flaps
sometimes affect pitch trim. Some airplanes
pitch up (e.g., La 7, DC-3), some pitch down
(FW 190), and some suffer no pitch change at
all (Arado 96B) depending on the wing
design, the chord of the flaps and the
downwash on the tail. In the video example,
this airplane tends to pitch down when flaps
are deployed. This effect is automatically
compensated for by coupling a small amount
of elevator up-trim to the retracts in the
computer radio.
Lowering the flaps increases both lift and
drag. Partial flap increases lift more than
drag. Further increasing flap angle
increases drag more than lift. For a steep
approach, the heavy warbird needs increased
lift for slower flight and it needs
increased drag to limit airspeed in a steep
glide. But flaps can interfere with the
ability to flare—the plane will lose too
much airspeed and slam into the ground.
This is especially pronounced when landing
into a headwind because the wind speed
decreases near the ground. So, as a general
rule, power must be added during the flare
to overcome the excess drag and flatten the
glide. The one exception is the very steep
approach in which the airplane has a surplus
of airspeed anyway. If the plane bounces,
level the nose and add some power to flatten
the glide. In the event of an engine-out
landing (dead-stick in pilot speak), use
take-off flap position unless a very steep
approach is required.
When
learning to use flaps on a new airplane, try
some tight low-speed turns plus power-on and
power-off stalls at altitude. If she goes
into a spin, retract the flaps and let her
dive to build up airspeed before resuming
level flight. If you try to pull out too
soon, before sufficient airspeed is
attained, she may go right back into the
spin.
Flaps
are so much fun. I will never build an
airplane without them.
The
rectangular pattern approach is commonplace
in civilian airports but it is not typical
of military fighter bases. Instead, pilots
fly straight in or even split-S to landing
as required. WW2 landing strips were short
and poorly visible. So the most common
approach was a descending U-turn that held
the inside wing low so that the pilot could
see the entire runway and traffic ahead
until turning final. The video starts in a
typical descending U-turn with gear down and
flaps fully down for a steep final
approach. A long, low approach is just as
dramatic but gives the pilot more time and
space to line up the flight path for a
precise touchdown.
In
the video example, the pilot adjusts the
heading with both rudder and ailerons—notice
the wing wobbles as he lines it up. The
pilot isn’t really that bad; some of this is
crosswind turbulence.
The
video example shows a wheel landing as
opposed to a three-point landing. That is,
the main wheels touch down first and the
tail is slowly lowered as airspeed
decreases. A full-size tail-dragger warbird
typically has forward visibility of the
runway obscured by its big engine, so this
technique gives the pilot a better view.
Also notice how the flaps are raised as soon
as all flying speed is lost. Warbirds of
this era had delicate flaps low to the
ground so debris kicked up by the prop and
wheels tended to damage the flaps when
taxiing with flaps down. To prevent this,
flaps were raised as quickly as possible.
Fly well...
The model in the videos is the
author’s Exact 1/5th Scale Focke
Wulf TA 152H (114” span, 27
lbs). For additional
In-flight Videos and FREE
Downloadable Plans
click the
Andersen Designs tab. |
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