| Home | Privacy | Contact |

Airplane Flying Handbook
Transition to Complex Airplanes
CONTROLLABLE-PITCH PROPELLER

| First | Previous | Next | Last |

Airplane Flying Handbook

Preface

Table of Contents

Chapter 1,Introduction to Flight Training
Chapter 2,Ground Operations
Chapter 3,Basic Flight Maneuvers
Chapter 4, Slow Flight, Stalls, and Spins
Chapter 5, Takeoff and Departure Climbs
Chapter 6, Ground Reference Maneuvers
Chapter 7, Airport Traffic Patterns
Chapter 8, Approaches and Landings
Chapter 9, Performance Maneuvers
Chapter 10, Night Operations
Chapter 11,Transition to Complex Airplanes
Chapter 12, Transition to Multiengine Airplanes
Chapter 13,Transition to Tailwheel Airplanes
Chapter 14, Transition to Turbo-propeller Powered Airplanes
Chapter 15,Transition to Jet Powered Airplanes
Chapter 16,Emergency Procedures

Glossary

Index

Since the recommendations given in the AFM/POH are
based on the airplane and the flap design combination,
the pilot must relate the manufacturer's recommendation
to aerodynamic effects of flaps. This requires that
the pilot have a basic background knowledge of flap
aerodynamics and geometry. With this information, the
pilot must make a decision as to the degree of flap
deflection and time of deflection based on runway and
approach conditions relative to the wind conditions.

The time of flap extension and degree of deflection are
related. Large flap deflections at one single point in the
landing pattern produce large lift changes that require
significant pitch and power changes in order to
maintain airspeed and glide slope. Incremental
deflection of flaps on downwind, base, and final
approach allow smaller adjustment of pitch and power
compared to extension of full flaps all at one time. This
procedure facilitates a more stabilized approach.

A soft- or short-field landing requires minimal speed at
touchdown. The flap deflection that results in minimal
groundspeed, therefore, should be used. If obstacle
clearance is a factor, the flap deflection that results in
the steepest angle of approach should be used. It
should be noted, however, that the flap setting that
gives the minimal speed at touchdown does not
necessarily give the steepest angle of approach;
however, maximum flap extension gives the steepest
angle of approach and minimum speed at touchdown.
Maximum flap extension, particularly beyond 30 to
35°, results in a large amount of drag. This requires
higher power settings than used with partial flaps.
Because of the steep approach angle combined with
power to offset drag, the flare with full flaps becomes
critical. The drag produces a high sink rate that must
be controlled with power, yet failure to reduce power
at a rate so that the power is idle at touchdown allows
the airplane to float down the runway. A reduction in
power too early results in a hard landing.

Crosswind component is another factor to be
considered in the degree of flap extension. The
deflected flap presents a surface area for the wind to
act on. In a crosswind, the "flapped" wing on the
upwind side is more affected than the downwind
wing. This is, however, eliminated to a slight extent
in the crabbed approach since the airplane is more
nearly aligned with the wind. When using a wing low
approach, however, the lowered wing partially
blankets the upwind flap, but the dihedral of the wing
combined with the flap and wind make lateral control
more difficult. Lateral control becomes more difficult
as flap extension reaches maximum and the
crosswind becomes perpendicular to the runway.

Crosswind effects on the "flapped" wing become more
pronounced as the airplane comes closer to the ground.
The wing, flap, and ground form a "container" that is
filled with air by the crosswind. With the wind striking

the deflected flap and fuselage side and with the flap
located behind the main gear, the upwind wing will
tend to rise and the airplane will tend to turn into the
wind. Proper control position, therefore, is essential
for maintaining runway alignment. Also, it may
be necessary to retract the flaps upon positive
ground contact.

The go-around is another factor to consider when
making a decision about degree of flap deflection
and about where in the landing pattern to extend
flaps. Because of the nosedown pitching moment
produced with flap extension, trim is used to offset
this pitching moment. Application of full power in
the go-around increases the airflow over the
"flapped" wing. This produces additional lift
causing the nose to pitch up. The pitch-up tendency
does not diminish completely with flap retraction
because of the trim setting. Expedient retraction of
flaps is desirable to eliminate drag, thereby allowing
rapid increase in airspeed; however, flap retraction
also decreases lift so that the airplane sinks rapidly.

The degree of flap deflection combined with design
configuration of the horizontal tail relative to the
wing requires that the pilot carefully monitor pitch
and airspeed, carefully control flap retraction to
minimize altitude loss, and properly use the rudder
for coordination. Considering these factors, the pilot
should extend the same degree of deflection at the
same point in the landing pattern. This requires that a
consistent traffic pattern be used. Therefore, the pilot
can have a preplanned go-around sequence based on
the airplane's position in the landing pattern.

There is no single formula to determine the degree of
flap deflection to be used on landing, because a
landing involves variables that are dependent on each
other. The AFM/POH for the particular airplane will
contain the manufacturer's recommendations for
some landing situations. On the other hand,
AFM/POH information on flap usage for takeoff is
more precise. The manufacturer's requirements are
based on the climb performance produced by a given
flap design. Under no circumstances should a flap
setting given in the AFM/POH be exceeded
for takeoff.

CONTROLLABLE-PITCH PROPELLER

Fixed-pitch propellers are designed for best efficiency
at one speed of rotation and forward speed. This type
of propeller will provide suitable performance in
a narrow range of airspeeds; however, efficiency
would suffer considerably outside this range. To
provide high propeller efficiency through a wide
range of operation, the propeller blade angle
must be controllable. The most convenient
way of controlling the propeller blade angle is by
means of a constant-speed governing system.

 

11-3