Airplane Stability Flashcards

Questions and Answers

What determines the longitudinal stability of an airplane?

The relationship of thrust and lift to weight and drag.

The location of the CG with respect to the center of lift. (correct)

The effectiveness of the horizontal stabilizer, rudder, and rudder trim tab.

An airplane said to be inherently stable will

Require less effort to control (correct)

Not spin

Be difficult to stall

Changes in the center of pressure of a wing affect the aircraft's

Lift/drag ratio

Aerodynamic balance and controllability (correct)

Lifting capacity

An airplane has been loaded in such a manner that the CG is located aft the aft CG limit. One undesirable flight characteristic a pilot might experience with this airplane would be

Difficulty in recovering from a stalled condition Signup and view all the answers

What causes an airplane (except a T-tail) to pitch nosedown when power is reduced and controls are not adjusted?

The downwash on the elevators from the propeller slipstream is reduced and elevator effectiveness is reduced. Signup and view all the answers

What is the effect of advancing the throttle in flight?

Both aircraft groundspeed and angle of attack will increase. Signup and view all the answers

Loading an airplane to the most aft CG will cause the airplane to be

Less stable at all speeds Signup and view all the answers

Study Notes

Longitudinal Stability

Longitudinal stability is primarily influenced by the location of the center of gravity (CG) relative to the center of lift.
Positive stability is achieved when the center of lift is behind the center of gravity, causing the tail to generate a downward force that counters potential nose-down pitches.

Inherent Stability

An inherently stable airplane resists disturbances and returns to its original flight condition more easily.
Such airplanes require less effort to control and are generally more forgiving in turbulent conditions, making them harder to stall and less likely to spin.

Center of Pressure Effects

The center of pressure (CP) is where lift forces on the wing are concentrated and shifts depending on the angle of attack.
As angle of attack increases, CP moves forward, while it moves aft at lower angles, affecting the aircraft's aerodynamic balance and overall controllability.

Center of Gravity and Stall Recovery

An airplane with its CG loaded aft of the limit faces difficulties recovering from stalls, particularly at low speeds.
Control diminishes as the CG shifts backward, making stall recovery increasingly challenging and uncertain.

Pitching Due to Thrust Reduction

Reducing power (except in T-tail configurations) results in a decrease in downwash on the elevators, thus diminishing their effectiveness, leading the nose to pitch down.
The reduced thrust diminishes the negative lift from the tail, contributing to this pitch down tendency.

Effects of Advancing Throttle

Advancing the throttle increases both groundspeed and airspeed, leading to a pitch-up effect and an increase in angle of attack.
This increase in lift allows the aircraft to climb once the opposing forces of lift and weight are in equilibrium.

Center of Gravity and Stability

Moving the center of gravity toward the aft limit reduces stability at all flight speeds.
Maintaining a proper forward CG is crucial for ensuring controllability and stability throughout all phases of flight.

Description

Test your knowledge on the longitudinal stability of airplanes with these flashcards. The quiz covers key concepts, such as the position of the center of gravity and the effectiveness of stabilizing surfaces. Sharpen your understanding of airplane aerodynamics!