HIGH PERFORMANCE AND COMPLEX AIRPLANES

Transition to a complex airplane, or a high performance
airplane, can be demanding for most pilots without previous
experience. Increased performance and increased
complexity both require additional planning, judgment,
and piloting skills. Transition to these types of
airplanes, therefore, should be accomplished in a
systematic manner through a structured course of
training administered by a qualified flight instructor.
A complex airplane is defined as an airplane equipped
with a retractable landing gear, wing flaps, and a
controllable-pitch propeller. For a seaplane to be
considered complex, it is required to have wing flaps and
a controllable-pitch propeller. A high performance
airplane is defined as an airplane with an engine of more
than 200 horsepower.

WING FLAPS

Airplanes can be designed to fly fast or slow. High
speed requires thin, moderately cambered airfoils with
a small wing area, whereas the high lift needed for low
speeds is obtained with thicker highly cambered
airfoils with a larger wing area. [Figure 11-1] Many
attempts have been made to compromise this
conflicting requirement of high cruise and slow
landing speeds.

Since an airfoil cannot have two different cambers at
the same time, one of two things must be done. Either
the airfoil can be a compromise, or a cruise airfoil can
be combined with a device for increasing the camber of
the airfoil for low-speed flight. One method for varying
an airfoil's camber is the addition of trailing edge flaps.
Engineers call these devices a high-lift system.

FUNCTION OF FLAPS
Flaps work primarily by changing the camber of the
airfoil since deflection adds aft camber. Flap deflection
does not increase the critical (stall) angle of attack, and
in some cases flap deflection actually decreases the
critical angle of attack.

Deflection of trailing edge control surfaces, such as the
aileron, alters both lift and drag. With aileron
deflection, there is asymmetrical lift (rolling moment)
and drag (adverse yaw). Wing flaps differ in that
deflection acts symmetrically on the airplane. There is
no roll or yaw effect, and pitch changes depend on the
airplane design.