mod 4

The rotor of a helicopter provides three basic fiunctions:

• a) generation of vertical lifting force(thrust) in oppose to aircraft weight b) generation of horizontal propulsive force for forward flight c) Means of generating forces and moments to control the altitude and position of the helicopter.
• retarding force created by development of lift and the movement of an object through the air
• is defined as flowing parallel, opposite the axis of rotation of the rotor and distinctly perpendicular to the leading edge of the rotor blade.
• As disc loading increases, greater the ________ you need to control the speed of the rotor.

Airfoil

• The direction of the relative wind is relative to the attitude, or position, of the airfoil and is always parallel, equal, and opposite in direction to the ___________.
• provides aerodynamic force when it interacts with a moving stream of air.
• distance from the rotor hub to the blade tip.
• The production of _____ is based upon the airfoil creating circulation in the airstream (Magnus Effect) and creating differential pressure on the airfoil (Bernoulli's Principle).

Symmetrical

• the curvature of the airfoil's upper and lower surfaces.
• opposes lift and is caused by the downward pull of gravity.
• this type of airfoil is very stable, which helps keep the blade twisting and flight control loads to a minimum.
• The result of this effect is a tendency for the helicopter to roll slightly to the right as it accelerates through approximately 20 knots or if the headwind is approximately 20 knots.

Symmetrical

• retarding force created by development of lift and the movement of an object through the air
• When a helicopter is at rest, the blades will ________ because of a lack of centrifugal stiffening.
• provides aerodynamic force when it interacts with a moving stream of air.
• meaning both the upper and the lower surfaces had the same camber (curvature)

droop

• In fluid dynamics, the momentum theory or disk actuator theory is a theory describing a mathematical model of an ideal actuator disk, such as a propeller or helicopter rotor, by _________ , _______ and _________.
• provides aerodynamic force when it interacts with a moving stream of air.
• When a helicopter is at rest, the blades will droop because of a lack of _______________.
• When a helicopter is at rest, the blades will ________ because of a lack of centrifugal stiffening.

centrifugal stiffening

• When a helicopter is at rest, the blades will droop because of a lack of _______________.
• the ratio of the load supported by the main rotor system to the actual weight of the helicopter and its contents.
• It is caused by the fact that in directional flight the aircraft relative wind is added to the rotational relative wind on the advancing blade and subtracted on the retreating blade.
• As the induced flow increases, the angle of attack _________.

Droop Stops

• When a helicopter is at rest, the blades will ________ because of a lack of centrifugal stiffening.
• occurs as the rotor blades begin to lift the weight of the helicopter.
• these are used to prevent the blades from hitting the fuselage when starting up or shutting down.
• A single main rotor helicopter, during the hovering flight, appears to drift in the same direction as the thrust of antitorque rotor. This drifting tendency is called ______________________.

Droop Stops

• The direction of this wind is relative to the attitude, or position, of the airfoil and is always parallel, equal, and opposite in direction to the flight path.
• used to limit blade travel both up and down.
• refers to a principle of gyroscopes that states when a force is applied to a spinning object, the maximum reaction occurs approximately 90 degrees later in the direction of rotation.
• TRUE

upwards stops

• utilized to restrict excessive blade sailing when starting the helicopter up in a wind.
• In a no-wind condition over a solid, smooth surface the ground effect is at its ____________.
• when the rotor blades speed up or slow down as the center of gravity moves closer or further away from the axis of rotation.
• an upward sweeping angle of the rotor blades as a result of lift and centrifugal force.

Reflexing

• these are used to prevent the blades from hitting the fuselage when starting up or shutting down.
• the resulting movement or deflection of a rotating object when a force on this object is applied.
• done on asymmetrical airfoils wherein the trailing edge is bended to create the same features as symmetrical airfoils.
• when the rotor blades speed up or slow down as the center of gravity moves closer or further away from the axis of rotation.