SIFT Aircraft Components and Controls 3 — Questions and Answers
Question 1: What is the function of the swashplate assembly in a helicopter rotor system?
- Converts engine torque directly to lift
- Transmits cyclic and collective pitch inputs to the rotating rotor blades (Correct answer)
- Controls fuel mixture to the engine
- Connects the tail rotor driveshaft to the main gearbox
Correct answer: Transmits cyclic and collective pitch inputs to the rotating rotor blades
The swashplate translates non-rotating pilot inputs from the cyclic and collective into changing blade pitch angles as the rotor turns.
Question 2: During a coordinated turn in a fixed-wing aircraft, the ball in the turn coordinator should be:
- Displaced to the outside of the turn
- Displaced to the inside of the turn
- Centered (Correct answer)
- Irrelevant during turns
Correct answer: Centered
A centered ball indicates that the turn is coordinated, meaning rudder input matches the bank angle and there is no sideslip.
Question 3: What is the purpose of leading edge slats on a fixed-wing aircraft?
- Reduce induced drag at cruise speed
- Increase the wing's camber and delay stall at high angles of attack (Correct answer)
- Generate reverse thrust on landing
- Provide roll control at low speeds
Correct answer: Increase the wing's camber and delay stall at high angles of attack
Leading edge slats extend forward from the wing leading edge to increase camber and allow airflow to remain attached at higher angles of attack, lowering stall speed.
Question 4: The 'anhedral' wing configuration (wings angled downward from root to tip) is primarily used to:
- Improve lateral stability
- Improve high-speed performance by reducing lift
- Reduce lateral (roll) stability for improved maneuverability (Correct answer)
- Increase ground clearance for engines
Correct answer: Reduce lateral (roll) stability for improved maneuverability
Anhedral reduces the dihedral effect, lowering roll stability and making the aircraft more responsive in roll, often used on highly maneuverable or swept-wing aircraft.
Question 5: In a semi-rigid rotor system, what is the purpose of the 'flapping hinge'?
- Allows the blade to change its pitch angle
- Allows the blade to flap up and down to equalize lift across the rotor disk (Correct answer)
- Locks the blade during autorotation
- Attaches the blade to the swashplate
Correct answer: Allows the blade to flap up and down to equalize lift across the rotor disk
The flapping hinge allows each rotor blade to move up (flap) on the advancing side and down on the retreating side, balancing the dissymmetry of lift.
Question 6: What does the term 'gyroscopic precession' mean in the context of helicopter rotors?
- The rotor spinning faster as altitude increases
- A force applied to a spinning disk results in movement 90° later in the direction of rotation (Correct answer)
- The tendency of the rotor to stop when engine power is lost
- An increase in blade pitch during autorotation
Correct answer: A force applied to a spinning disk results in movement 90° later in the direction of rotation
Gyroscopic precession causes an applied force on a spinning rotor to take effect 90° ahead in the direction of rotation, which must be accounted for in blade pitch control inputs.
Question 7: Spoilers on a fixed-wing aircraft are primarily used to:
- Increase lift during takeoff
- Disrupt airflow over the wing to reduce lift and increase drag (Correct answer)
- Control pitch attitude at low speed
- Provide directional control on the ground
Correct answer: Disrupt airflow over the wing to reduce lift and increase drag
Spoilers extend upward from the upper wing surface to disrupt airflow, destroying lift and adding drag, used both as speed brakes in flight and ground spoilers on landing.
SIFT Aircraft Components and Controls 3
What is the function of the swashplate assembly in a helicopter rotor system?