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Airplane Flying Handbook
Transition to Jet Powered Airplanes
STALLS

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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

STALLS

The stalling characteristics of the sweptwing jet
airplane can vary considerably from those of the
normal straight wing airplane. The greatest difference
that will be noticeable to the pilot is the lift developed
vs. angle of attack. An increase in angle of attack of the
straight wing produces a substantial and constantly
increasing lift vector up to its maximum coefficient of
lift, and soon thereafter flow separation (stall) occurs
with a rapid deterioration of lift.

By contrast, the sweptwing produces a much more
gradual buildup of lift with no well defined maximum
coefficient and has the ability to fly well beyond this
maximum buildup even though lift is lost. The drag
curves (which are not depicted in figure 15-13) are
approximately the reverse of the lift curves shown, in
that a rapid increase in drag component may be
expected with an increase in the angle of attack of a
sweptwing airplane.

Stall vs. angle of attack—sweptwing vs. straight wing.
Figure 15-13. Stall vs. angle of attack—sweptwing vs. straight wing.

The differences in the stall characteristics between a
conventional straight wing/low tailplane (non T-tail)
airplane and a sweptwing T-tail airplane center around
two main areas.
• The basic pitching tendency of the airplane at
the stall.
• Tail effectiveness in stall recovery.

On a conventional straight wing/low tailplane airplane,
the weight of the airplane acts downwards forward of
the lift acting upwards, producing a need for a
balancing force acting downwards from the tailplane.
As speed is reduced by gentle up elevator deflection,
the static stability of the airplane causes a nosedown
tendency. This is countered by further up elevator to
keep the nose coming up and the speed decreasing. As
the pitch attitude increases, the low set tail is immersed
in the wing wake, which is slightly turbulent, low
energy air. The accompanying aerodynamic buffeting
serves as a warning of impending stall. The reduced
effectiveness of the tail prevents the pilot from forcing

the airplane into a deeper stall. [Figure 15-14] The
conventional straight wing airplane conforms to the
familiar nosedown pitching tendency at the stall and
gives the entire airplane a fairly pronounced nosedown
pitch. At the moment of stall, the wing wake passes
more or less straight rearward and passes above the
tail. The tail is now immersed in high energy air where
it experiences a sharp increase in positive angle of
attack causing upward lift. This lift then assists the
nosedown pitch and decrease in wing angle of attack
essential to stall recovery.

Stall progression—typical straight wing airplane.
Figure 15-14. Stall progression—typical straight wing airplane.

In a sweptwing jet with a T-tail and rear fuselage
mounted engines, the two qualities that are different
from its straight wing low tailplane counterpart are the
pitching tendency of the airplane as the stall develops
and the loss of tail effectiveness at the stall. The
handling qualities down to the stall are much the same
as the straight wing airplane except that the high, T-tail
remains clear of the wing wake and provides little or
no warning in the form of a pre-stall buffet. Also, the
tail is fully effective during the speed reduction
towards the stall, and remains effective even after the
wing has begun to stall. This enables the pilot to drive
the wing into a deeper stall at a much greater angle
of attack.

At the stall, two distinct things happen. After the stall,
the sweptwing T-tail airplane tends to pitch up rather
than down, and the T-tail is immersed in the wing
wake, which is low energy turbulent air. This greatly
reduces tail effectiveness and the airplane's ability to
counter the nose up pitch. Also, the disturbed,
relatively slow air behind the wing may sweep across
the tail at such a large angle that the tail itself stalls. If
this occurs, the pilot loses all pitch control and will be
unable to lower the nose. The pitch up just after the
stall is worsened by large reduction in lift and a large
increase in drag, which causes a rapidly increasing
descent path, thus compounding the rate of increase of
the wing's angle of attack. [Figure 15-15]

 

15-11