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airplane’s pitch attitude is decreased below the
horizon, as is normal recovery procedure in most
piston powered straight wing, light airplanes.
Therefore, at the lower altitudes where plenty of
engine thrust is available, the recovery technique in
many sweptwing jets involves applying full available
power, rolling the wings level, and holding a slightly
positive pitch attitude. The amount of pitch attitude
should be sufficient enough to maintain altitude or
begin a slight climb.
At high altitudes, where there may be little excess
thrust available to effect a recovery using power alone,
it may be necessary to lower the nose below the
horizon in order to accelerate away from an impending
stall. This procedure may require several thousand feet
or more of altitude loss to effect a recovery. Stall
recovery techniques may vary considerably from
airplane to airplane. The stall recovery procedures for
a particular make and model airplane, as
recommended by the manufacturer, are contained in
the FAA-approved Airplane Flight Manual for
that airplane.
DRAG DEVICES
To the pilot transitioning into jet airplanes, going faster
is seldom a problem. It is getting the airplane to slow
down that seems to cause the most difficulty. This is
because of the extremely clean aerodynamic design
and fast momentum of the jet airplane, and also
because the jet lacks the propeller drag effects that the
pilot has been accustomed to. Additionally, even with
the power reduced to flight idle, the jet engine still
produces thrust, and deceleration of the jet airplane is a
slow process. Jet airplanes have a glide performance
that is double that of piston powered airplanes, and jet
pilots often cannot comply with an air traffic control
request to go down and slow down at the same time.
Therefore, jet airplanes are equipped with drag devices
such as spoilers and speed brakes.
The primary purpose of spoilers is to spoil lift. The
most common type of spoiler consists of one or more
rectangular plates that lie flush with the upper surface
of each wing. They are installed approximately
parallel to the lateral axis of the airplane and are hinged
along the leading edges. When deployed, spoilers
deflect up against the relative wind, which interferes
with the flow of air about the wing. [Figure 15-18] This
both spoils lift and increases drag. Spoilers are usually
installed forward of the flaps but not in front of the
ailerons so as not to interfere with roll control.
Initial Stall
Deep Stall
Pre-Stall
Relative Wind
Relative Wind
Relative Wind
Pitch Attitude
Flightpath Angle to the Horizontal
Angle of Attack
Figure 15-17. Deep stall progression.
Figure 15-18. Spoilers.
Ch 15.qxd 5/7/04 10:22 AM Page 15-13
15-14
Deploying spoilers results in a substantial sink rate
with little decay in airspeed. Some airplanes will
exhibit a noseup pitch tendency when the spoilers are
deployed, which the pilot must anticipate.
When spoilers are deployed on landing, most of the
wing’s lift is destroyed. This action transfers the
airplane’s weight to the landing gear so that the wheel
brakes are more effective. Another beneficial effect of
deploying spoilers on landing is that they create
considerable drag, adding to the overall aerodynamic
braking. The real value of spoilers on landing, however,
is creating the best circumstances for using
wheel brakes.
The primary purpose of speed brakes is to produce
drag. Speed brakes are found in many sizes, shapes,
and locations on different airplanes, but they all have
the same purpose—to assist in rapid deceleration. The
speed brake consists of a hydraulically operated board
that when deployed extends into the airstream.
Deploying speed brakes results in a rapid decrease in
airspeed. Typically, speed brakes can be deployed at
any time during flight in order to help control airspeed,
but they are most often used only when a rapid deceleration
must be accomplished to slow down to landing
gear and flap speeds. There is usually a certain amount
of noise and buffeting associated with the use of speed
brakes, along with an obvious penalty in fuel consumption.
Procedures for the use of spoilers and/or
speed brakes in various situations are contained in the
FAA-approved Airplane Flight Manual for the particular
airplane.
THRUST REVERSERS
Jet airplanes have high kinetic energy during the
landing roll because of weight and speed. This energy
is difficult to dissipate because a jet airplane has low
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