Translational lift
Encyclopedia
Translational lift is a transitional state present as a helicopter
moves from hover to forward flight. This state provides extra lift
, most typically, when the airspeed reaches approximately 16-24 knots, but is present with any horizontal flow of air across the rotor , and therefore can be present without any forward motion of the aircraft, given prevailing wind conditions.
The most common example of the effect is this: a helicopter might be slightly overloaded for take off so that it cannot hover. Liftoff can still be achieved if the helicopter has enough of a straight runway to make a "Running take off" where the pilot will slowly accelerate the helicopter across the ground until translational lift speed is achieved, extra rotor-disc lift is produced, and the aircraft will begin to climb.
In Robert Mason’s book, Chickenhawk
, Mason describes a situation where an aircraft, loaded with 2500 pounds of high explosives, was above gross weight and should have been unable to achieve flight, was actually "coaxed" into flight via the "Running Take Off".
Helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...
moves from hover to forward flight. This state provides extra lift
Lift (force)
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...
, most typically, when the airspeed reaches approximately 16-24 knots, but is present with any horizontal flow of air across the rotor , and therefore can be present without any forward motion of the aircraft, given prevailing wind conditions.
The most common example of the effect is this: a helicopter might be slightly overloaded for take off so that it cannot hover. Liftoff can still be achieved if the helicopter has enough of a straight runway to make a "Running take off" where the pilot will slowly accelerate the helicopter across the ground until translational lift speed is achieved, extra rotor-disc lift is produced, and the aircraft will begin to climb.
In Robert Mason’s book, Chickenhawk
Chickenhawk (book)
Chickenhawk is Robert Mason's narrative of his experiences as a UH-1 Iroquois helicopter pilot during the Vietnam War. The book chronicles his enlistment, flight training, deployment to and experiences in Vietnam, and his experiences after returning from the war.- Writing, Publishing, and Reaction...
, Mason describes a situation where an aircraft, loaded with 2500 pounds of high explosives, was above gross weight and should have been unable to achieve flight, was actually "coaxed" into flight via the "Running Take Off".