What is an autorotation in a helicopter?

Autorotation. In a helicopter, an autorotative descent is a power-off maneuver in which the engine is disengaged from the main rotor disk and the rotor blades are driven solely by the upward flow of air through the rotor. [Figure 11-1] In other words, the engine is no longer supplying power to the main rotor.

What is effective translational lift?

Effective translational lift (commonly referred to as ETL) is a term used to describe the airspeed at which the entire rotor system realizes the benefit of the horizontal air flow. This happens when the helicopter’s rotor disc moves completely out of its own downwash and into undisturbed air.

What is autorotation in a spin?

For fixed-wing aircraft, autorotation is the tendency of an aircraft in or near a stall to roll spontaneously to the right or left, leading to a spin (a state of continuous autorotation).

Do all helicopters have autorotation?

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.

What causes most helicopter crashes?

Potential causes are numerous, but some of the most common causes of helicopter crashes include: Manufacturing defect/product liability. Aircraft design defect. Aircraft maintenance negligence.

What are two advantages of helicopters?

We will now enlist 5 advantages that make air transportation by helicopter the best option for short distance travels to transport passengers or internal/external cargo:

• Time and speed.
• Procedures.
• Safety.
• No physical barriers.
• Ease of access.

Why do helicopters take off forward?

The rotor blades are pitched lower in the front of the rotor assembly than behind it. This increases the angle of attack — and creates lift — at the back of the helicopter. The unbalanced lift causes the helicopter to tip forward and move in that direction.

What are the three phases of a spin?

Spins are typically described as passing through phases: departure, post-stall gyration, incipient spin, developed spin, and recovery.

How did Kobe Bryant’s helicopter crash?

The Sikorsky S-76B helicopter was flying at about 184 mph (296 kph) and descending at a rate of more than 4,000 feet (1,219 meters) per minute when it slammed into the hillside and ignited, scattering debris over an area the size of a football field. The victims died immediately.

How are the aerodynamics of autorotation used in flight?

Aerodynamics of Autorotation During powered flight, the rotor drag is overcome with engine power. the engine fails, or is deliberately disengaged from the rotor system, some other force must be used to sustain rotor RPM so controlled flight

How does the drag of an autorotation helicopter work?

When the inflow up through the rotor combines with rotational relative wind, it produces different combinations of aerodynamic force at every point along the blade. In the driven region, the total aerodynamic force acts behind the axis of rotation, resulting in an overall dragging force.

How does autorotation affect the size of the driven region?

The size of this region varies with blade pitch setting, rate of descent, and rotor RPM. When the pilot takes action to change autorotative RPM, blade pitch, or rate of descent, he is in effect changing the size of the driven region in relation to the other regions. Between the driven region and the driving region is a point of equilibrium.

How is the direction of movement seen in aerodynamics?

In classic aerodynamics, the aerodynamic force is seen through the direction of movement (the vector of speed V); its perpendicular to V component is called lift Ry and its opposite to V component is called drag Rx.