Helicopter Flight Principles

• The auxiliary (tail) rotor of a helicopter allows the pilot to compensate for or accomplish torque and directional control.
• Vertical flight of a helicopter is controlled by cyclic pitch changes (changes in horizontal plane).
• A reduction in anti-torque thrust causes the tail to pivot in the direction of torque rotation around the main rotor axis.
• In rotorcraft external-loading, the ideal cargo release location is through the center of gravity at all times.
• The acute angle formed by the chord line of a wing and relative wind defines the angle of attack.
• In forward flight, a helicopter in cruise configuration changes direction by tilting the main rotor disk in the desired direction.
• Checking main rotor blade tracking determines the relative position of the blades during rotation.
• In a hovering helicopter with a tail rotor, directional control is maintained by varying the pitch of the tail rotor blades (forward, backwards, or sideways).
• In single-rotor helicopter forward horizontal flight, the angle of attack of the advancing blade is less than the retreating blade.
• Main rotor blades that don't cone by the same amount during rotation are out of track.
• One purpose of the freewheeling unit between the engine and helicopter transmission is to automatically disengage the rotor from the engine in case of engine failure.
• Torque direction is opposite of rotor blade rotation on helicopters.
• The purpose of the free-wheeling unit in a helicopter drive system is that it disconnects the rotor whenever the engine stops or slows below the equivalent of rotor RPM.
• Movement about the longitudinal axis or "roll" in a helicopter is effected by movement of the cyclic pitch control .
• Movement about the lateral axis or "pitch" in a helicopter is effected by movement of the cyclic pitch control .
• Wing dihedral generally contributes most to stability of the airplane about its lateral axis.
• Other than the manufacturer maintenance manual, an aircraft type certificate data sheet can determine primary flight control surface deflection for an imported aircraft reassembled after shipment.
• If a pilot reports an airplane flies left wing heavy, the condition may be corrected by increasing the angle of incidence of the left wing, or decreasing the angle of incidence of the right wing, or both.
• The vertical fin of a single-engine, propeller-driven airplane that is rigged properly will generally be parallel to both the longitudinal and vertical axes.
• Good longitudinal stability should have a minimum tendency to pitch.
• As airfoil's angle of attack increases, the center of pressure will move toward the leading edge.
• The angle of incidence is that acute angle formed by a line parallel to the wing chord and a line parallel to the longitudinal axis of the aircraft.
• An airplane's center of lift is usually located aft of its center of gravity to improve stability about the longitudinal axis.
• Directional control about its vertical axis: rudder.
• Elevators of a conventional airplane are used to provide rotation about the lateral axis.
• Washing-in the left wing of a monoplane for rigging corrections after a flight test will mean both drag and lift will increase due to increased angle of attack.
• Fowler flaps increase the wing area and change the wing camber.
• If the right wing of a monoplane is improperly rigged an increased angle of incidence than designated by the manufacturer's specifications, the airplane will be off balance both laterally and directionally.
• A wing's chord is measured from the leading edge to trailing edge.
• When an airfoil's lift increases, the drag will also increase.

Helicopter control relies on manipulating rotor systems. The tail rotor manages torque and direction. Vertical flight is achieved through cyclic pitch adjustments, and forward movement involves tilting the main rotor.