Aircraft Systems and Aerodynamics Flashcards

What is 'adverse yaw' and how do conventional ailerons cause it?

Answer: Yaw opposite to the intended turn direction, caused by increased drag on the rising (up-aileron) wing

Adverse yaw occurs because the down-going aileron (on the rising wing) produces more induced drag than the up-going aileron, yawing the nose away from the direction of turn.

What is the effect of a forward CG on aircraft stall speed?

Answer: Forward CG requires a higher angle of attack (and thus higher airspeed) to balance the greater nose-down moment, slightly increasing stall speed

A forward CG creates a greater nose-down pitching moment that must be balanced by tail-down elevator force, effectively reducing net lift and requiring a slightly higher angle of attack and airspeed to maintain level flight.

In a turbofan engine, what does 'bypass ratio' describe?

Answer: The ratio of air mass flowing around the core to air mass flowing through the engine core

Bypass ratio is the ratio of the airflow that bypasses the engine core (through the fan duct) to the airflow that passes through the combustion core, with high bypass ratios giving better fuel efficiency.

What is 'Dutch roll' in aircraft dynamics?

Answer: A coupled oscillation of yaw and roll that is characteristic of swept-wing aircraft with weak directional stability

Dutch roll is a coupled, oscillatory yaw-roll motion that can occur when an aircraft has strong dihedral effect (roll stability) relative to its directional (yaw) stability, common on swept-wing aircraft.

What does a 'V-n diagram' (flight envelope) illustrate for a commercial pilot?

Answer: The structural load factor limits across the aircraft's operating airspeed range

A V-n diagram plots load factor (G) against airspeed, showing the boundaries of the flight envelope within which the aircraft can be operated without exceeding structural limits.

What is the 'P-factor' (asymmetric blade effect) in a single-engine aircraft with a clockwise-rotating propeller (viewed from behind)?

Answer: Left-turning tendency at high power/low airspeed because the descending right blade has a higher angle of attack and produces more thrust

At high power and low airspeed with a nose-high attitude, the descending right propeller blade has a greater angle of attack than the ascending left blade, producing more thrust on the right side and yawing the aircraft left.

What is the purpose of 'winglets' on modern transport aircraft?

Answer: To reduce induced drag by limiting wingtip vortex formation without a large increase in wingspan

Winglets effectively increase the aspect ratio aerodynamically without a large physical span increase, reducing the energy lost to wingtip vortices and thereby decreasing induced drag and improving fuel efficiency.