Principles of Flight practice questions

Answer: B) A height equal to about one wingspan

Ground effect normally becomes detectable within about one wingspan of the surface. The reduction in upwash, downwash, wingtip vortices and induced drag gets larger as the wing descends further, for example about 50 percent at one-tenth of the span.

• AIncorrect. This height is well above where the surface changes the airflow around the wing in any meaningful way. Ground effect is normally detectable only within about one wingspan.
• BCorrect. FAA guidance says ground effect normally occurs up to a height equal to one wingspan above the surface. It becomes stronger as the wing gets closer to the ground.
• CIncorrect. At one-tenth of the span, induced drag is reduced by about 50 percent. However, ground effect is already detectable higher up, at about one wingspan.
• DIncorrect. For a typical light airplane, 500 feet AGL is many wingspans above the surface. Ground effect is tied to wingspan and appears much closer to the ground.

Answer: B) Less air flows over the rudder, so the same deflection produces a smaller aerodynamic force

Control effectiveness depends on airflow over the surface. At low airspeed, a given rudder deflection produces less force, so larger inputs are needed, though propeller slipstream at high power helps somewhat.

• AIncorrect. Lower airspeed reduces aerodynamic forces on the control surface, so the controls usually feel lighter or 'mushy', not harder to deflect. Full deflection is still available but produces less force.
• BCorrect. With less airflow over the control surfaces, each control input produces less force. Larger control movements are needed for the same response, although propeller slipstream at high power can partly restore rudder authority.
• CIncorrect. Slipstream over the tail is strongest at high power and low airspeed. That is why some rudder authority remains in slow flight at high power.
• DIncorrect. Maneuvering speed relates to structural loads from full or abrupt control deflection. Rudder travel stops do not change with airspeed below VA.

Answer: C) A horizontal surface ahead of the wing

• AIncorrect. That's a flap.
• BIncorrect. That's a winglet.
• CCorrect. It provides pitch control or lift.
• DIncorrect. That's for helicopters.

Answer: B) Skidding; reduce rudder pressure toward the inside of the turn

A ball toward the outside of the turn means a skid caused by too much rudder into the turn. It is corrected by easing that rudder pressure, i.e. by stepping on the ball toward the outside.

• AIncorrect. A slip shows the ball toward the inside of the turn, not the outside. Adding inside rudder here would make the existing skid worse.
• BCorrect. A ball toward the outside shows a skid: too much rudder into the turn, so the rate of turn is too high for the bank angle. 'Stepping on the ball' means easing off the inside rudder (applying rudder toward the outside), which recenters the ball.
• CIncorrect. The condition is wrong. A slip displaces the ball toward the inside of the turn, and it is corrected with more inside rudder or less bank.
• DIncorrect. The condition is right but the correction is backward. Excess inside rudder caused the skid, so adding more would increase the skid and the risk of a cross-controlled stall.

Answer: A) A coupled rolling and yawing oscillation that occurs when the dihedral effect is stronger than directional stability

Dutch roll is a coupled roll-yaw oscillation that occurs when the dihedral (lateral stability) effect outweighs directional stability. Spiral instability is the opposite case, and yaw dampers are commonly used to control Dutch roll.

• ACorrect. Dutch roll is a combined rolling and yawing oscillation. It typically happens when the dihedral (lateral stability) effect is more powerful than directional stability. It is usually dynamically stable but objectionable, and yaw dampers are often used to suppress it.
• BIncorrect. This describes spiral instability, which comes from the opposite balance: strong directional stability and a weak dihedral effect. It is a divergent spiral, not an oscillation.
• CIncorrect. This describes the phugoid, a longitudinal (pitch) oscillation. Dutch roll is a lateral-directional motion about the roll and yaw axes.
• DIncorrect. This describes a spin, which requires a stall. Dutch roll can occur in normal unstalled flight after a disturbance such as a gust or a rudder input.

Answer: C) Newton's third law

• AIncorrect. That's gases.
• BIncorrect. That explains lift.
• CCorrect. The airplane reacts opposite the propeller.
• DIncorrect. That's electricity.

Answer: B) It reduces it, improving cruise efficiency

• AIncorrect. Aft CG reduces tail-down force.
• BCorrect. Stability also decreases.
• CIncorrect. CG location changes tail force.
• DIncorrect. That isn't typical.

Answer: D) A slow tendency to bank further and spiral down

• AIncorrect. That isn't spiral instability.
• BIncorrect. That's lateral stability.
• CIncorrect. That's longitudinal behavior.
• DCorrect. Strong directional stability can cause it.

Answer: D) Relative wind

• AIncorrect. It's relative wind.
• BIncorrect. That's pitch attitude.
• CIncorrect. That's angle of incidence-related.
• DCorrect. It isn't the pitch attitude.

Answer: D) How close the wing is to the critical angle

• AIncorrect. That's the heading indicator.
• BIncorrect. That's the attitude indicator.
• CIncorrect. That's the airspeed indicator.
• DCorrect. It warns of stalls at any speed.