N. Rotorcraft Fundamentals
What are the basic flight control rigging procedures for a helicopter? (AM.II.N.K4)
1. Place the controls in a set position and clamp or pin in place, 2. place the control surfaces in the specified position using rigging jigs or a precision protractor, and 3. set the maximum travel stops for the controls.
What is the purpose of the stabilizer system in a helicopter? (AM.II.N.K2)
A helicopter is statically stable but dynamically unstable. The stabilizer system restores the helicopter to level flight when outside forces cause it to pitch or roll.
What is meant by a rigid rotor system? (AM.II.N.K5)
A rotor system that has freedom of motion about its feather axis only. The flexibility of the blades is sufficient to provide the needed flapping and dragging.
What is meant by a semirigid rotor system? (AM.II.N.K5)
A two-blade rotor system in which the blades can feather, but cannot flap or drag. The rotor hub is mounted on the mast with a teetering hinge that allows the entire rotor to rock as a unit.
What is the purpose of transmission mount dampening? (AM.II.N.K9)
Extreme low-frequency vibration is associated with pylon rock (two or three cycles per second) and is inherent with the rotor, mast, and transmission system. Transmission mount dampening is incorporated to absorb the rocking.
Why is it important that the blades of a helicopter rotor system be in track? (AM.II.N.K2)
If the blades are not in track, vertical vibration can develop.
What is the function of the collective pitch control of a helicopter? (AM.II.N.K2)
It changes the pitch of all the blades at the same time. The collective pitch controls the vertical flight of the helicopter.
What is the function of the cyclic pitch control? (AM.II.N.K2)
It changes the pitch of the rotor blades at a particular point in their rotation to tilt the plane of the rotor. The cyclic pitch controls the lateral movement of the helicopter.
What is meant by a fully articulated rotor system? (AM.II.N.K5)
It is a rotor system in which the individual blades are free to flap, drag, and feather.
What is the basic cause of low-frequency vertical vibration? (AM.II.N.K8)
One of the main rotor blades producing more lift than the other.
What type of construction is used in rotor blades? (AM.II.N.K7)
Rotor blades can be constructed of aluminum extrusions and sheet metal, composite construction, or a combination of metallic and composite components.
What is usually the cause of high-frequency vibration? (AM.II.N.K8)
The engine, cooling fan, or tail rotor.
What causes dissymmetry of lift produced by the rotor of a helicopter? (AM.II.N.K1)
The forward speed of the helicopter produces dissymmetry of lift. The rotor blade that is traveling forward as the helicopter is flying produces more lift than the blade that is traveling rearward.
What is the basic cause of low-frequency lateral vibration? (AM.II.N.K8)
The main rotor blades being out of static balance.
What is the shape of a cross section of a rotor blade? (AM.II.N.K7)
The shape of a rotor blade is an airfoil, similar to that of an aircraft wing.
What is the function of the tail rotor on a single main rotor helicopter? (AM.II.N.K2)
The thrust from the tail rotor counteracts the torque of the main rotor to control the yaw of the helicopter. The control pedals change the pitch of the tail rotor blades to vary the thrust.
Why do single-rotor helicopters use an auxiliary rotor on their tail? (AM.II.N.K2)
The thrust from the tail rotor counteracts the torque produced by the main rotor.
What is the purpose of a transmission on a helicopter? (AM.II.N.K3)
The transmission system transfers power from the engine to the main rotor, tail rotor, and other accessories during normal flight conditions.
What is the purpose of a helicopter skid shoe? (AM.II.N.K6)
To protect the helicopter landing skid tubes from wear.
What is the most effective way to check a helicopter rotor for dynamic balance? (AM.II.N.K8)
Use a special computerized analyzer/balancer.
