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the turn. Precision error is not apparent on the ADI because the IRS is
the source of attitude information.
Dutch Rolls
When a swept-wing aircraft is subjected to yaw, a dutch roll condition can result
due to the forward-moving wing developing more lift than the other wing, which
is losing some lift due to its relative direction of movement. Normally the yaw
dampening system of the B737 prevents a dutch roll condition from developing.
Recovery from a dutch roll is accomplished by applying aileron into the rising
wing followed by a return to the neutral aileron position. The combined effect
of the aileron and spoiler deflection serves to destroy the developing lift on the
forward-moving wing. The initial required aileron deflection will depend on the
severity of the roll. In most cases, however, the control wheel should initially be
displaced approximately 45 degrees. Subsequent corrections should be
progressively less. Full speedbrakes aid in dutch roll damping. The use of
rudder during recovery from a dutch roll is not recommended.
Sec. 3 Page 352
Rev. 11/15/02 #41 Continental
737
Flight Manual
Stalls
General
Stall speed is defined as the minimum steady flight speed in any given
configuration at which a constant altitude can be maintained (or the minimum
steady flight speed at which the angle of attack for maximum lift is attained).
During initial stages of stall, local airflow separation results in buffeting, giving
natural warning of an approach to a stall.
Initial buffet is caused by airflow separation. Stall warning is considered to be
any warning readily identifiable by the pilot, either artificial (stick shaker) or
initial buffet (stabilizer shake, aileron shake, or wing shake). Recovery from an
approach to stall will be initiated at the earliest recognizable stall warning,
initial buffet, or stick shaker.
Lateral and Directional Control:
· Lateral control is maintained with ailerons and spoilers, which remain
effective throughout the maneuver.
· Rudder control should not be used to help maintain wings level. A rudder
input will cause yaw and the resultant roll due to yaw is undesirable.
Effects of Flaps
The B737 incorporates an auto-slat system. The auto-slat system provides
improved handling qualities at high angles of attack during takeoff or approach
to landing. When trailing edge flaps 1 through 5 are selected, the leading edge
slats are in the EXTEND position. As the aircraft approaches the stall angle, the
slats automatically drive to the FULL EXTEND position, prior to stick shaker
activation. The slats return to the EXTEND position when the pitch angle is
sufficiently reduced below the stall critical attitude.
With the trailing edge flaps up, the slats remain in the retracted position during
the stall.
With flaps up, the aircraft exhibits normal stall characteristics. As airflow
separation begins to occur, a light buffeting is felt which continues to increase
as angle of attack is increased. As the stall is continued beyond initial buffet,
any sideslip that develops will have a tendency to include roll-off. Heading and
wings level attitude can effectively be controlled with lateral control inputs.
737
Flight Manual Continental
Sec. 3 Page 353
Rev. 11/15/02 #41
With flaps down, the stall characteristics are very docile. The auto-slat system
fully extends the leading edge slats when approaching stall angle of attack if the
flaps are in the takeoff range. Light buffeting is felt as airflow separation begins
to occur, which continues to increase as angle of attack is increased. There is
very little roll-off tendency, and the normal lateral controls remain effective,
even at full stall.
Tailoring of the leading edge devices ensures the inboard wing will stall prior to
the outboard wing resulting in a nose down pitch tendency at stall.
Approach to Stalls Maneuver
The pilot will accomplish the IN-RANGE checklist prior to demonstrating the
stall recoveries. Trim as required throughout the maneuver.
Note: If stalls are accomplished in actual aircraft training, do not trim below
maneuvering speed for flaps selected, set the start switches to CONT,
and select G/A in N1 limit.
Required Configurations
1. Clean
2. Turning, flaps 5, gear down, 20 degrees bank
3. Landing, flaps 30, gear down
Purpose and Desired Results
1. Understand and recognize an impending stall condition.
2. React with judgment and procedures to counteract the impending stall.
3. Accelerate to maneuvering speed for the configuration with minimum
altitude loss or gain.
Approach to Stalls
1. Clean Stall - Reduce power to approximately 40% N1.
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