| Home | Privacy | Contact |

Airplane Flying Handbook
Transition to Complex Airplanes
WING FLAPS

| 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

Pitch behavior depends on flap type, wing position,
and horizontal tail location. The increased camber
from flap deflection produces lift primarily on the rear
portion of the wing. This produces a nosedown
pitching moment; however, the change in tail load
from the downwash deflected by the flaps over the
horizontal tail has a significant influence on the
pitching moment. Consequently, pitch behavior
depends on the design features of the particular airplane.

Flap deflection of up to 15° primarily produces lift
with minimal drag. The tendency to balloon up with
initial flap deflection is because of lift increase, but the
nosedown pitching moment tends to offset the balloon.
Deflection beyond 15° produces a large increase in
drag. Drag from flap deflection is parasite drag, and
as such is proportional to the square of the speed. Also,
deflection beyond 15° produces a significant nose up
pitching moment in most high-wing airplanes because
the resulting downwash increases the airflow over the
horizontal tail.

FLAP EFFECTIVENESS
Flap effectiveness depends on a number of factors, but
the most noticeable are size and type. For the purpose
of this chapter, trailing edge flaps are classified as four
basic types: plain (hinge), split, slotted, and Fowler.
[Figure 11-2]

The plain or hinge flap is a hinged section of the wing.
The structure and function are comparable to the other
control surfaces—ailerons, rudder, and elevator. The
split flap is more complex. It is the lower or underside
portion of the wing; deflection of the flap leaves the
trailing edge of the wing undisturbed. It is, however,
more effective than the hinge flap because of greater
lift and less pitching moment, but there is more drag.
Split flaps are more useful for landing, but the partially
deflected hinge flaps have the advantage in takeoff.
The split flap has significant drag at small deflections,
whereas the hinge flap does not because airflow
remains "attached" to the flap.

The slotted flap has a gap between the wing and the
leading edge of the flap. The slot allows high
pressure airflow on the wing undersurface to energize
the lower pressure over the top, thereby delaying flow
separation. The slotted flap has greater lift than the
hinge flap but less than the split flap; but, because of
a higher lift-drag ratio, it gives better takeoff and
climb performance. Small deflections of the slotted
flap give a higher drag than the hinge flap but less
than the split. This allows the slotted flap to be used
for takeoff.

The Fowler flap deflects down and aft to increase the
wing area. This flap can be multi-slotted making it the
most complex of the trailing edge systems. This
system does, however, give the maximum lift
coefficient. Drag characteristics at small deflections
are much like the slotted flap. Because of structural
complexity and difficulty in sealing the slots, Fowler
flaps are most commonly used on larger airplanes.

Four basic types of flaps.
Figure 11-2. Four basic types of flaps.

OPERATIONAL PROCEDURES
It would be impossible to discuss all the many airplane
design and flap combinations. This emphasizes the
importance of the FAA-approved Airplane Flight
Manual and/or Pilot's Operating Handbook
(AFM/POH) for a given airplane. However, while
some AFM/POHs are specific as to operational use of
flaps, many are lacking. Hence, flap operation makes
pilot judgment of critical importance. In addition, flap
operation is used for landings and takeoffs, during
which the airplane is in close proximity to the ground
where the margin for error is small.

 

11-2