Rotor Configuration & Flight Controls PDF

BASIC HELICOPTER & PROPELLER DESIGN...

BASIC HELICOPTER & PROPELLER DESIGN Rotor system, rotor configuration and flight controls Prepared By Engr. Shiara Denise M. Valencia Rotor System The helicopter rotor system is the rotating part of a helicopter that generates lift. A rotor system may be mounted: - horizontally, as main rotors are, providing lift vertically; - vertically, such as a tail rotor, to provide lift horizontally as thrust to counteract torque effect.  For TILT ROTORS, the rotor is m ounted on a nacelle that rotates at the edge of the wing to transition the rotor from a horizontal mounted position, providing lift horizontally as thrust, to a vertical mounted position providing lift exactly as a helicopter.  The swash plate assembly consists of two parts — the upper and lower swash plates. The upper swash plate connects to the mast, or rotor shaft, through special linkages. As the engine turns the rotor shaft, it also turns the upper swash plate and the rotor blade system. The lower swash plate is fixed and doesn't rotate. Ball bearings lie between the upper and lower swash plates, allowing the upper plate to spin freely on top of the lower plate. Control rods from the upper swash plate have a connection point on the blades, making it possible to transfer movements of the upper swash plate to the blades. Control rods attached to the lower swash plate connect to the cyclic- and collective-pitch levers. Blade grips connect the blades to a hub. ROTOR BLADE MOVEMENTS Main rotor systems are classified according to how the main rotor blades are attached and move relative to the main rotor hub. FEATHER FLAP LEAD - LAG ROTOR BLADE MOVEMENTS LEAD – LAG FEATHER FLAP DRAG ROTOR BLADE MOVEMENTS Blade Flap The ability of the rotor blade to move in a vertical direction. Blades may flap independently or in unison. Blade lead or lag The fore and aft movement of the blade in the plane of rotation. It is sometimes called hunting or dragging. Feathering The action that changes the pitch angle of the rotor blades by rotating them around their feathering (spanwise) axis. CLASSIFICATION OF ROTOR SYSTEM Main rotor systems are classified according to how the main rotor blades are attached and move relative to the main rotor hub. rigid semirigid fully articulated CLASSIFICATION OF ROTOR SYSTEM Semi rigid A semirigid rotor system is usually composed of two blades that are rigidly attached to the main rotor hub. The main rotor hub is free to tilt with respect to the main rotor shaft on what is known as a teetering or flapping hinge. This allows the blades to flap together as a unit. As one blade flaps up, the other flaps down. CLASSIFICATION OF ROTOR SYSTEM Semi rigid The teetering hinge allows the main rotor to tilt. The feathering hinge enables the main rotor angle’s to change. CLASSIFICATION OF ROTOR SYSTEM rigid the blades are rigidly attached to the rotor hub. They cannot flap or lead-lag, but they can be feathered. rigid rotor systems may become more common because the system is fundamentally easier to design and offers the best properties of both semirigid and fully articulated systems. CLASSIFICATION OF ROTOR SYSTEM rigid The rigid rotor system is very responsive and is usually not susceptible to mast bumping like the semirigid systems because the rotor hubs are mounted solid to the main rotor mast. This allows the rotor and fuselage to move together as one entity and eliminates much of the oscillation usually present in the other rotor systems. CLASSIFICATION OF ROTOR SYSTEM CLASSIFICATION OF ROTOR SYSTEM rigid CLASSIFICATION OF ROTOR SYSTEM rigid CLASSIFICATION OF ROTOR SYSTEM Fully articulated Fully articulated rotor systems allow each blade to lead-lag (move back and forth in plane), flap (move up and down about an inboard mounted hinge) independent of the other blades, and feather rotate about the pitch axis to change lift). CLASSIFICATION OF ROTOR SYSTEM Fully articulated CLASSIFICATION OF ROTOR SYSTEM Fully articulated CLASSIFICATION OF ROTOR SYSTEM Fully articulated Flight Controls FLIGHT CONTROLS FLIGHT CONTROLS COLLECTIVE The collective, operated by the pilot with the left hand, is pulled up or pushed down to increase or decrease the angle of attack on all of the rotor blades simultaneously. This increases or decreases lift and moves the aircraft up or down. FLIGHT CONTROLS COLLECTIVE Collective changes the pitch angle of all the main rotor blades collectively. FLIGHT CONTROLS THROTTLE The engine throttle control is located on the hand grip at the end of the collective. FLIGHT CONTROLS THROTTLE The throttle controls the power produced by the engine, which is connected to the rotor by a transmission. The purpose of the throttle is to maintain enough engine power to keep the rotor rpm within allowable limits to produce enough lift for flight. FLIGHT CONTROLS CYCLIC The cyclic is the control “stick” located between the pilot’s legs. It can be moved in any direction to tilt the plane of rotation of the rotor blades. This causes the helicopter to move in the direction that the cyclic is moved. FLIGHT CONTROLS CYCLIC The control is called the cyclic because it can vary the pitch of the rotor blades throughout each revolution of the main rotor system (i.e., through each cycle of rotation) to develop unequal lift (thrust). FLIGHT CONTROLS FOOT PEDALS The foot pedals control the pitch of the tail rotor blades thereby balancing main rotor torque FLIGHT CONTROLS HELICOPTER FLIGHT CONTROLS FLIGHT CONTROLS