What is a Delta 3 hinge?

What is a Delta 3 hinge?

A delta-3 hinge is a hinge that is not at a 90-degree angle, it is offset to some degree. When a delta-3 hinge is used in a rotor blade, the blade angle is changed as the blade flaps. This change in angle is because the hinge is offset.

What is Delta hinge helicopter?

Noun. delta hinge (plural delta hinges) (aeronautics) On rotorcraft, a hinge with its axis parallel to the rotor plane of rotation, which permits the rotor blades to flap.

Why do some helicopters have 3 blades?

For smaller helicopters, a two-bladed or 3-bladed rotor system gives the best option as the disk load is easily overcome with fewer blades. This makes design easier, costs less, uses fewer parts and weighs less.

Why are helicopter blades hinged?

The blades are allowed to flap, feather, and lead or lag independently of each other. The horizontal hinge, called the flapping hinge, allows the blade to move up and down. This movement is called flapping and is designed to compensate for dissymmetry of lift.

What is feathering the rotor blade?

Feathering the blade means changing the pitch angle of the blade. By changing the pitch angle of the blades you can control the thrust and direction of the main rotor disc.

What is feathering on a helicopter?

Feathering. The action that changes the pitch angle of the rotor blades by rotating them around their feathering (spanwise) axis. Feathering axis. The axis about which the pitch angle of a rotor blade is varied. Sometimes referred to as the spanwise axis.

What is flapping hinge helicopter?

The flapping hinge ( English flapping hinge ) allows the rotor blade of a helicopter or rotorcraft to move with respect to the rotor circle plane up or down. It prevents overloading of the rotor blade root and the rotor head . Flapping hinges allow the rotor blade to move approx. 35 ° upwards and 5 ° downwards.

How do you counter a Dissymmetry lift?

Dissymmetry of lift is countered by reducing the angle of attack of the advancing blade and increasing the angle of attack of the retreating blade. This is done by blade flapping and cycling feathering. Blade flapping is the primary means of countering dissymmetry of lift.

Why does a helicopter hover left side low?

Helicopters usually hover left side low due to the tail rotor thrust being counteracted by the main rotor tilt. A nose low or high condition is generally caused by loading. Once stabilized, check the engine instruments and note the power required to hover.

What is flapping in helicopter?

Flapping is the vertical movement of a blade up or down to increase or decrease lift in order to compensate for dissymmetry of lift. To equalize lift across the rotor disc, the advancing blade flaps up and the retreating blade flaps down.

What is a flapping hinge?

A hinge connecting a rotor blade to the hub and about which the blade rises and falls (i.e., flaps during its rotation, and thus permits equalization of lift—or rotor thrust) between the advancing-blade half and the retreating-blade half of the rotor disc.

What is blade coning?

Blade coning. An upward sweep of rotor blades as a result of lift and centrifugal force.

What is a delta-3 hinge?

A delta-3 hinge is a hinge that is not at a 90-degree angle, it is offset to some degree. When a delta-3 hinge is used in a rotor blade, the blade angle is changed as the blade flaps. This change in angle is because the hinge is offset.

Why do tail rotors have a Delta 3 hinge?

This change in angle is because the hinge is offset. The delta 3-hinge is commonly used in tail rotors to reduce the degree of flapping that is required. This practice allows for the tail rotor to be closer to the tailboom, ultimately reducing vibration.

What type of hinge is used in the rotors of helicopters?

This type of hinge is used in some main rotors to a lesser degree. The primary deterrent for the use of the delta-3 hinge is the increased stress imposed on the hinge. Principles of Helicopter Flight, 2nd Edition, pg. 96