What is special about the shape of a helicopter rotor blade?
The blades of a helicopter are long, narrow airfoils with a high aspect ratio, a shape that minimizes drag from tip vortices (see the wings of a glider for comparison).
What force keeps the blades of a helicopter horizontal in flight?
The rotation of the rotor system creates centrifugal force (inertia), which tends to pull the blades straight outward from the main rotor hub. The faster the rotation, the greater the centrifugal force. This force gives the rotor blades their rigidity and, in turn, the strength to support the weight of the helicopter.
How does a rotor blade work on a helicopter?
The blades are shaped like airfoils (airplane wings with a curved profile) so they generate lift as they spin. Each blade can swivel about a feathering hinge as it spins. Vertical pitch links push the blades up and down, making them swivel as they rotate.
Why are helicopter blades angled?
Air flows more slowly at the hub of a rotor, than at the faster moving tip. So to produce an even amount of lift along the blade, you want a higher angle of attack at the hub than at the tip. That’s achieved by making the rotor with a twist along its length.
Why are helicopter blades not twisted?
Helicopter blades do have twist. The relative air speed increases from blade root to blade tip, and therefore on an untwisted blade lift would increase quadratically from root to tip. Or going the other way, lift would reduce quadratically from tip to root.
How are the aerodynamic forces of the rotor controlled?
Explanation: The aerodynamic forces of the rotor is controlled using the pitch motion which helps in altering the angle of attack of the rotor blade. The change of blade pitch angle is known as feathering motion.
Can a helicopter fly without a tail rotor?
Without the tail rotor or other anti-torque mechanisms (e.g. NOTAR), the helicopter would be constantly spinning in the opposite direction of the main rotor when flying.
How do helicopter blades change pitch?
The collective pitch control is usually found at the pilot’s left hand; it is a lever that moves up and down to change the pitch angle of the main rotor blades. Raising or lowering the pitch control increases or decreases the pitch angle on all blades by the same amount.
Why is the propeller blade twisted?
Propeller Design There is a twist along the length of a propeller blade because the blade speed is much higher at the tip than it is at the root. The twist is necessary to maintain a more or less constant angle of attack along the length of the blade.
What is the purpose of rotor blade flapping?
The advancing rotor blade reaches its maximum “up-flap” velocity at point “A”. The upward flapping of the advancing blade reduces the angle between the blade chord line and the relative wind. This decreases the angle of attack, which reduces the amount of lift produced by the blade.
How thick is a helicopter blade?
The main rotor blade is about 9 m long. The structural part is a hollow extruded spar made of 6061- T6 aluminium alloy (Fig. 1, section view), 4.5 mm thick on average.
What is helicopter aerodynamics?
The correspondence between helicopter aerodynamics and airplane aerodynamics spans beyond the need for free stream flow across an airfoil. Helicopter aerodynamics involves the same forces that arise in airplane aerodynamics, but these forces arise in different ways due to fluid flow across the aircraft.
What is aeroelasticity of helicopter rotor blades?
Helicopter design is truly an interdisciplinary activity and aeroelasticity of the rotor blades is also an important feature in the modeling of the rotor wake. On the blade, the flow can be locally supersonic and shocks can form while downstream of the blade in the wake, the flow is incompressible and vortical in character.
What are the aerodynamics of helicopter?
Before talking about the aerodynamics of helicopters we first have to introduce a few basic principles of aerodynamics. In order to get aircrafts that are “heavier than air” off the ground a force has to act upwards that is as least equal to the weight of the aircraft. This force is called lift and is created by the wings.
What direction do helicopter rotor blades turn?
For helicopters built in the United States, the main rotor blades turn in a counterclockwise direction when viewed from the top. Viewed from the top, as the blades move around the right side of the helicopter, they are moving toward the nose; as they move around the left side of the helicopter, they are moving toward the tail.
What gives the blades of a helicopter their strength?
This force gives the rotor blades their rigidity and, in turn, the strength to support the weight of the helicopter. The centrifugal force generated determines the maximum operating rotor r.p.m. due to structural limitations on the main rotor system.