Stall Characteristics
Different airplane designs can result in different stall characteristics.
The pilot should know the stall characteristics of the airplane being flown and the manufacturer’s recommended recovery procedures.
Factors that can affect the stall characteristics of an airplane include its geometry, CG, wing design, and high-lift devices.
Engineering design variations make it impossible to specifically describe the stall characteristics for all airplanes; however, there are enough similarities in small general aviation training-type airplanes to offer broad guidelines.
Most training airplanes are designed so that the wings stall progressively outward from the wing roots (where the wing attaches to the fuselage) to the wingtips.
Some wings are manufactured with a certain amount of twist, known as washout, resulting in the outboard portion of the wings having a slightly lower AOA than the wing roots.
This design feature causes the wingtips to have a smaller AOA during flight than the wing roots.
Thus, the wing roots of an airplane exceed the critical AOA before the wingtips, meaning the wing roots stall first.
Therefore, when the airplane is in a stalled condition, the ailerons should still have a degree of control effectiveness until/unless stalled airflow migrates outward along the wings.
Although airflow may still be attached at the wingtips, a pilot should exercise caution using the ailerons prior to the reduction of the AOA because it can exacerbate the stalled condition.
For example, if the airplane rolls left at the stall (“rolls-off”), and the pilot applies right aileron to try to level the wing, the downward-deflected aileron on the left wing produces a greater AOA (and more induced drag), and a more complete stall at the tip as the critical AOA is exceeded.
This can cause the wing to roll even more to the left, which is why it is important to first reduce the AOA before attempting to roll the airplane.
The pilot must also understand how the factors that affect stalls are interrelated.
In a power-off stall, for instance, the cues (buffeting, shaking) are less noticeable than in the power-on stall.
In the power-off, 1G stall, the predominant cue may be the elevator control position (full up elevator against the stops) and a high descent rate.
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