Basic Aerodynamics To Stability! Principles Trivia Quiz

1. An airplane said to be inherently stable will

Be difficult to stall

Require less effort to control

Not spin

An airplane that is inherently stable means that it has a natural tendency to maintain its equilibrium and resist deviations from its intended flight path. This stability reduces the need for constant adjustments and corrections from the pilot, resulting in less effort required to control the aircraft. In contrast, an unstable airplane would require constant input and effort from the pilot to maintain control. Therefore, the correct answer is that an inherently stable airplane would require less effort to control.

Explanation

An airplane that is inherently stable means that it has a natural tendency to maintain its equilibrium and resist deviations from its intended flight path. This stability reduces the need for constant adjustments and corrections from the pilot, resulting in less effort required to control the aircraft. In contrast, an unstable airplane would require constant input and effort from the pilot to maintain control. Therefore, the correct answer is that an inherently stable airplane would require less effort to control.

2. What determines the longitudinal stability of an airplane?

The location of the CG with respect to the center of lift

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

The relationship of thrust and lift to weight and drag.

The longitudinal stability of an airplane is determined by the location of the center of gravity (CG) with respect to the center of lift. If the CG is located ahead of the center of lift, the airplane will have a tendency to pitch down, while if the CG is located behind the center of lift, the airplane will have a tendency to pitch up. Therefore, the correct answer is that the location of the CG with respect to the center of lift determines the longitudinal stability of an airplane.

Explanation

The longitudinal stability of an airplane is determined by the location of the center of gravity (CG) with respect to the center of lift. If the CG is located ahead of the center of lift, the airplane will have a tendency to pitch down, while if the CG is located behind the center of lift, the airplane will have a tendency to pitch up. Therefore, the correct answer is that the location of the CG with respect to the center of lift determines the longitudinal stability of an airplane.

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

A longer take off run

Difficulty in recovering from a stalled condition

Stalling at higher-than normal airspeed.

If the CG (Center of Gravity) is located aft of the aft CG limit, it means that the center of mass of the airplane is positioned too far back. This can result in an unstable flight condition, making it difficult for the pilot to recover from a stalled condition. When an airplane stalls, it loses lift and starts to descend rapidly. In this case, the aft CG position can exacerbate the stall condition, making it harder for the pilot to regain control and recover the airplane to a normal flight state.

Explanation

If the CG (Center of Gravity) is located aft of the aft CG limit, it means that the center of mass of the airplane is positioned too far back. This can result in an unstable flight condition, making it difficult for the pilot to recover from a stalled condition. When an airplane stalls, it loses lift and starts to descend rapidly. In this case, the aft CG position can exacerbate the stall condition, making it harder for the pilot to regain control and recover the airplane to a normal flight state.

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

Less stable at all speeds

Less stable at slow speeds, but more stable at high speeds

Less stable at high speeds, but more stable at low speeds

Loading an airplane to the most aft CG (center of gravity) position means that the weight is concentrated towards the rear of the aircraft. This causes the airplane to become less stable at all speeds. Stability in an aircraft is determined by the location of the CG relative to the center of lift and the tail. When the CG is aft, the aircraft becomes more difficult to control and is more prone to pitching and yawing motions. This decrease in stability affects the aircraft's performance and handling characteristics, making it less stable overall, regardless of the speed it is flying at.

Explanation

Loading an airplane to the most aft CG (center of gravity) position means that the weight is concentrated towards the rear of the aircraft. This causes the airplane to become less stable at all speeds. Stability in an aircraft is determined by the location of the CG relative to the center of lift and the tail. When the CG is aft, the aircraft becomes more difficult to control and is more prone to pitching and yawing motions. This decrease in stability affects the aircraft's performance and handling characteristics, making it less stable overall, regardless of the speed it is flying at.

5. During a spin to the left, which wing(s) is/are stalled?

Both wings are stalled

Neither wing is stalled

Only the left wing is stalled

During a spin to the left, both wings are stalled. In a spin, the airplane is in an uncoordinated state with one wing having a higher angle of attack than the other. This causes both wings to stall simultaneously, resulting in a loss of lift and a rapid descent. The stalled wings create an imbalance in lift, causing the airplane to rotate around its vertical axis. Therefore, in a spin to the left, both wings are stalled.

Explanation

During a spin to the left, both wings are stalled. In a spin, the airplane is in an uncoordinated state with one wing having a higher angle of attack than the other. This causes both wings to stall simultaneously, resulting in a loss of lift and a rapid descent. The stalled wings create an imbalance in lift, causing the airplane to rotate around its vertical axis. Therefore, in a spin to the left, both wings are stalled.

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

The CG shifts forward when thrust and drag are reduced

The down wash on the elevators from the propeller slipstream is reduced and elevator effectiveness is reduced.

When power is reduced and controls are not adjusted, the down wash on the elevators from the propeller slipstream is reduced. This reduction in down wash decreases the effectiveness of the elevator, causing the airplane to pitch nose-down.

Explanation

When power is reduced and controls are not adjusted, the down wash on the elevators from the propeller slipstream is reduced. This reduction in down wash decreases the effectiveness of the elevator, causing the airplane to pitch nose-down.

7. In what flight condition must an aircraft be placed in order to spin?

Partially stalled with one wing low

In a steep diving spiral

Stalled.

An aircraft must be placed in a stalled condition in order to spin. When an aircraft is stalled, the airflow over the wings is disrupted, causing a loss of lift. In a spin, one wing drops and the aircraft rotates around its vertical axis. This occurs when the aircraft is in a stalled condition and the pilot applies excessive or incorrect rudder input. In this situation, the aircraft enters an uncontrolled descent and rotation. Therefore, being stalled is the flight condition necessary for an aircraft to spin.

Explanation

An aircraft must be placed in a stalled condition in order to spin. When an aircraft is stalled, the airflow over the wings is disrupted, causing a loss of lift. In a spin, one wing drops and the aircraft rotates around its vertical axis. This occurs when the aircraft is in a stalled condition and the pilot applies excessive or incorrect rudder input. In this situation, the aircraft enters an uncontrolled descent and rotation. Therefore, being stalled is the flight condition necessary for an aircraft to spin.