What is Delta hinge?
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.
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 hinge in helicopter?
These rotor systems usually have three or more blades. 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 does the pitch horn do?
The purpose of the pitch horn is to give the feathering pitch change mechanism (cyclic/swashplate) a place to attach to the blade. By sticking out from the blade, the pitch horn works as a lever, decreasing the force it takes to change the angle of the blade.
How do you compensate for a dissymmetry of lift?
Compensation for Dissymmetry of Lift in Helicopters – YouTube
What causes dissymmetry of lift?
Dissymmetry of lift is the difference in lift that exists between the advancing half of the rotor disk and the retreating half. 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.
What is a flapping hinge?
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. The flapping hinge may be located at varying distances from the rotor hub, and there may be more than one hinge.
What is flapping and feathering?
Flapping, the vertical up/down movement of the blades, is not directly controlled. What a pilot controls is the blade feathering or pitch angle. Increasing feathering / pitch generally increases the aerodynamic forces on the blades, which changes the flapping.
What is helicopter mast bumping?
Mast bumping is contact between an inner part of a main rotor blade or a rotor hub and the main rotor drive shaft (or ‘mast’). Serious mast bumping in flight usually results in the helicopter breaking up in flight, which is fatal for those on board.
What does a swashplate do?
A swashplate is a device that is used to transmit the pilot’s commands from the non-rotating fuselage to the rotating rotor hub and blades. The fact that the rotor blades are rotating at a very high speed makes the swashplate mechanism’s task more challenging.
Why do helicopters have a never exceed speed?
As a helicopter’s speed increases the airflow becomes more horizontal causing the main rotor rpm to decay. As such, a power-off never exceed speed would prevent the main rotor RPM from dropping too low at high speeds.
Why do helicopter blades flap?
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 do you counteract a dissymmetry of 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.
What causes blade flapping?
When a rotor blade advances toward the front of the helicopter and experiences an increased velocity of airflow, the increase in lift causes the blade to flap up.
What is cyclic feathering?
Cyclic feathering. The mechanical change of the angle of incidence, or pitch, of individual rotor blades, independent of other blades in the system.
What RPM does a helicopter blade spin at?
The blades of an average helicopter on Earth rotate at a rate of 400-500 rotations per minute. The blades of the Ingenuity #MarsHelicopter rotate at a rate of 2,500 rotations per minute.
How long do helicopter blades last?
If you look at the main and tail rotor blades they also have a calendar limit of 12 years. Whichever limit is reached first is when they must be replaced: 12 years or 2200 hours.
Which is the safest helicopter in the world?
The Robinson R44: The Safest Helicopter in the World. We also love the Robinson R44 because each seat is a window seat, so not only are your views phenomenal, but it helps you avoid motion sickness. How much does it cost to build your own helicopter?
What is low-G in a helicopter?
Low-g condition is a phase of aerodynamic flight where the airframe is temporarily unloaded. The pilot—and the airframe—feel temporarily “weightless” because the aircraft is in free-fall or decelerating vertically at the top of a climb. It may also occur during an excessively rapid entry into autorotation.
Can all helicopters auto rotate?
All helicopters must have this capability in order to be certified. Autorotation is possible owing to a freewheeling unit, which allows the main rotor to continue turning even if the engine is not running. In normal powered flight, air is drawn into the main rotor system from above and exhausted downward.
How does a pilot compensate for blowback?
To compensate for blowback, you must move the cyclic forward. A horizontal lift component (thrust) generates higher helicopter airspeed. The higher airspeed induces blade flapping to maintain symmetry of lift.
What is the most difficult helicopter to fly?
As the most technically advanced helicopter in the world, the Apache AH Mk1 was also the hardest to fly…. To train each Apache pilot from scratch cost £3 million (each custom-made helmet alone had a price tag of £22,915).
Can a helicopter survive tail rotor failure?
It is perfectly possible to recover from a tail rotor failure. There are some flight regimes that might lead to a crash with all but the best pilot and some luck. A tail rotor failure in cruise should be survivable, especially if you can find something hard to land on.
What is feathering in 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.
How do helicopters compensate for dissymmetry of lift?
Tandem-rotor helicopters are installed with automatic cyclic feathering systems. At low airspeeds, blade flapping compensates for dissymmetry of lift. As airspeed increases, typically above 70 knots, these systems allow a more level fuselage attitude which reduces stresses on the rotor driving mechanisms.