Free SIFT Army Aviation Information Questions and Answers 1 — Questions and Answers
Question 1: A thrust is produced by
- The fuselage of a helicopter
- The tail rotor of a helicopter
- The main rotor of a helicopter
- The engine(s) of a helicopter (Correct answer)
Correct answer: The engine(s) of a helicopter
Thrust is the force that propels an aircraft. In a helicopter, the engine(s) are responsible for generating the power that drives the main rotor system. It is the rotation of these main rotor blades, powered by the engine(s), that creates the aerodynamic forces, including both lift and thrust, necessary for flight.
Question 2: Which of the following does not refer to a typical helicopter control?
- Throttle
- Collective
- Dual (Correct answer)
- Cyclic
Correct answer: Dual
The primary flight controls of a helicopter are the collective, which changes the pitch of all main rotor blades simultaneously to control altitude; the cyclic, which changes the pitch of individual blades cyclically to control direction; and the anti-torque pedals (or tail rotor control), which control yaw. 'Dual' is not a standard flight control component.
Question 3: Which of the subsequent is not a typical helicopter taxi maneuver?
- Ground Taxi
- Hover Taxi
- Air Taxi
- Rotor Taxi (Correct answer)
Correct answer: Rotor Taxi
Standard helicopter taxi maneuvers include Ground Taxi (moving on wheels), Hover Taxi (moving slowly above the ground, typically below 20 knots and 20 feet AGL), and Air Taxi (moving faster and/or higher than a hover taxi, but still below normal cruising flight). 'Rotor Taxi' is not a recognized or typical term for a helicopter taxi maneuver.
Question 4: During takeoff, blade flapping is utilized to:
- Counter a vortex ring state
- Counter dissymmetry of lift (Correct answer)
- Increase the speed of forward flight
- Decrease the speed of forward flight
Correct answer: Counter dissymmetry of lift
During forward flight, the advancing rotor blade (moving in the direction of flight) experiences higher airspeed and thus more lift than the retreating blade. This phenomenon is called dissymmetry of lift. Blade flapping, where the blades move up and down, is a crucial mechanism that allows the rotor system to equalize lift across the rotor disc, thereby countering dissymmetry of lift and maintaining stable flight.
Question 5: Another name for settling with power is
- Coaxial rotor maneuver
- Vortex ring state (Correct answer)
- In ground effect
- Emergency landing
Correct answer: Vortex ring state
Settling with power is a dangerous aerodynamic condition where a helicopter descends into its own downwash, causing the rotor blades to operate in turbulent air that has already passed through the rotor. This leads to a significant loss of lift and control, even with power applied. This condition is also commonly known as a vortex ring state.
Question 6: An mechanical angle called an angle of incidence exists between
- The angle of incidence is the angle between the chord line of an airfoil (such as a helicopter rotor blade) and the plane of rotation. It is the angle at which the blade is set or tilted relative to the airflow or the direction of motion. The angle of incidence affects the amount of lift and drag produced by the blade.
- The chord line of the blade and the circular plane in which it rotates (Correct answer)
- The main rotor and the tail rotor
- The chord line of the blade and the fuselage
Correct answer: The chord line of the blade and the circular plane in which it rotates
The angle of incidence, also referred to as the blade pitch angle, is a critical mechanical angle in helicopter aerodynamics. It is defined as the angle between the chord line of a rotor blade (an imaginary line from the leading to the trailing edge) and the circular plane in which the rotor blade rotates. This angle is adjusted by the pilot to control the amount of lift generated.
Question 7: A pilot can ______ by moving a cyclic.
- Alter the pitch of main rotor blades
- Alter the length of main rotor blades
- Decrease altitude
This question is incomplete as the correct answer option is missing. However, a cyclic control in a helicopter allows the pilot to alter the pitch of individual main rotor blades at specific points in their rotation. This differential pitch change tilts the rotor disc, which in turn controls the direction of the helicopter's flight (forward, backward, or sideways).
A thrust is produced by