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How can retreating blade stall be avoided?
You can avoid retreating blade stall by not exceeding the never-exceed speed. This speed is designated VNE and is usually indicated on a placard and marked on the airspeed indicator by a red line.
What is \\\"torque\\\"; as it applies to helicopters with a single main rotor system?
In helicopters with a single main rotor system; torque is the tendency of the helicopter to turn in the opposite direction of the main rotor rotation.
Define Total Drag
Total drag is the sum of induced drag and parasite drag.
What is autorotation
Autorotation is the state of flight where the main rotor system is being turned by the action of relative wind rather than engine power. It is the means by which a helicopter can be landed safely in the event of an engine failure.
Which flight control controls blade pitch angle � the collective or the cyclic?
Both! The collective pitch changes each rotor blade an equal amount of pitch no matter where it is located in the plane of rotation (rotor disc) and is used to change rotor thrust. The cyclic pitch control changes the pitch of each blade as a function of where it is in the plane of rotation. Recall that the pitch angle of a rotor blade is the angle between its chord line and the reference plane containing the rotor hub.
What is the principle of gyroscopic precession?
When a force is applied to a spinning gyro; the maximum reaction occurs approximately 90� later in the direction of rotation.
Why does translational lift occur?
As the helicopter accelerates through around 16-24 knots (horizontal velocity); the rotor moves out of its vortices and is in relatively undisturbed air. The airflow is also now more horizontal; which reduces induced flow and drag with a corresponding increase in angle of attack and lift. The additional lift available at this speed is referred to as \\\"effective translational lift\\\" (ETL).
What are the four forces acting upon a helicopter in forward flight?
Lift; Weight; Thrust; Drag
Can translational lift be a factor in hovering or vertical flight?
Absolutely. Translational lift is also present in a stationary hover if the wind speed is approximately 16 to 24 knots. In normal operations; always utilize the benefit of translational lift; especially if maximum performance is needed.
What is retreating blade stall?
At a high forward speeds; the retreating main rotor blade stalls because of a high angle of attack and slow relative wind speed. This situation is called retreating blade stall and is evidenced by a nose pitch up; vibration; and a rolling tendency�usually to the left in helicopters with counterclockwise blade rotation.
What is the main purpose of the tail rotor in a helicopter with a single main rotor?
To counteract the torque of the main rotor.
What is \\\"induced flow?\\\"
As rotor blades produce lift; air is accelerated over the foil and projected (induced) downward. Anytime a helicopter is producing lift; it moves large masses of air vertically and down through the rotor system Induced flow is the flow of air induced through the main rotor system.
About what percentage of the blade radius is driven during autorotation?
The driven region; also called the propeller region; is nearest the blade tips. Normally; it consists of about 30 percent of the radius.
List the main flight controls.
the cyclic pitch control; the collective pitch control; the throttle; (usually a twist grip control located on the end of the collective lever) and the antitorque pedals.
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