Aerodynamics and Aircraft Systems Flashcards

What distinguishes Fowler flaps from plain flaps in terms of aerodynamic effect?

Answer: Fowler flaps increase wing area and camber by sliding aft before rotating down

Fowler flaps first translate rearward to increase wing area and then rotate downward to increase camber, producing large gains in maximum lift coefficient with relatively modest drag increases.

Thrust reversers on jet aircraft reverse thrust by:

Answer: Redirecting exhaust gases forward using blocker doors and cascade vanes

Thrust reversers deploy blocker doors that obstruct the rearward exhaust path and cascade vanes that redirect the flow forward and outward, producing a net retarding force.

A higher bypass ratio in a turbofan engine generally results in:

Answer: Better fuel efficiency and lower specific fuel consumption at subsonic cruise

High bypass ratio turbofans accelerate a large mass of air to a relatively low velocity, which is thermodynamically more efficient than accelerating a small mass to high velocity, reducing specific fuel consumption.

In a multi-engine aircraft, the 'critical engine' is defined as the engine whose failure:

Answer: Most adversely affects aircraft performance and handling characteristics

The critical engine is the one whose failure produces the greatest adverse yawing moment and reduces controllability the most, typically due to P-factor and thrust line asymmetry.

Gyroscopic precession in a rotating propeller causes the aircraft to react to a pitch input by:

Answer: Yawing 90 degrees in the direction of propeller rotation ahead of the applied force

Gyroscopic precession causes a force applied to a spinning gyroscope to manifest as a movement 90° ahead in the direction of rotation; for a clockwise (from pilot's view) propeller, a pitch-up input causes a yaw to the right.

Flight spoilers (as opposed to ground spoilers) are primarily used in flight to:

Answer: Assist roll control and act as speed brakes without large pitch changes

Flight spoilers augment aileron roll control (by spoiling lift on the descending wing) and can be symmetrically deployed as speed brakes, offering drag without major pitch trim changes.

What is the purpose of vortex generators installed on aircraft wing surfaces?

Answer: To re-energize the boundary layer and delay flow separation at high angles of attack

Vortex generators create small vortices that mix high-energy free-stream air into the sluggish boundary layer, delaying flow separation and stall, particularly on aircraft with thick or swept wings.