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In aviation,rotation refers to the action of applying back pressure to a control device, such as ayoke,side-stick orcentre stick, to lift the nose wheel off the ground duringtakeoff. An aircraft moves at any given moment in one or more of threeaxes: roll (the axis that runs the length of the fuselage), pitch (the axis running laterally through the wings), andyaw (the vertical axis around which the front of the aircraft turns to the left or right whilst its rear turns toward the opposite direction). Displacement along any of these axes is a form of rotation, but the term "rotation" in relation to takeoff is limited to the moment during which the aircraft's nose rises from the ground: the aircraft rotates around itslateral axis.
The first critical speed during takeoff (at which a pilot must decide whether to continue with takeoff or abort it) is called the "decision speed", orV1, beyond which it would be unsafe to abort the takeoff. Rotation is begun at the speed known asVR. Rotation at the correct speed and to the correct angle is important for safety reasons and to minimise takeoff distance.[1] After rotation, the aircraft continues to accelerate until it reaches its liftoff speedVLO, at which point it leaves therunway. After liftoff, a speedV2 will be called out, being the speed at which the aircraft is able to climb at a sufficient rate to reach its cruising altitude, and therefore at which the gear will be retracted.[2] Early or over-rotation can cause atailstrike, which can damage the underside of the tail unless prevented by a protection device such as a tailskid or tail bumper. A certification test is required to show that a new aircraft design will still take off safely with the tail dragging on the runway. Using a higher VR will increase tail clearance and reduce the probability of tailstrike. Over-rotation can also result in loss of lift, causing astall.
Rotation applies totricycle gear aircraft rather than those withconventional gear (tailwheel aircraft). The on-groundangle of attack of the wing has to be established during the design phase. The main and nose-gear leg lengths are chosen to give a negative angle of attack relative to the ground. This ensures the wing will have negative lift until thepilot rotates the aircraft to a positive angle of attack. During landing, the reverse happens when the nose-wheel touches the runway and the wing assumes a negative angle of attack with no lift.
For aircraft with a tailwheel, the pilot initially pushes forward on the yoke during the takeoff run, lifting the tailwheel off the runway, and the aircraft lifts off the runway once sufficient speed is achieved.[3]
