Take off

Take off is the phase of flight where an aircraft transitions from moving along the ground (taxiing) to flying in the air (see flight), usually from a runway. Take off is the opposite of landing.

Related Topics:
Aircraft - Taxiing - Flight - Runway - Landing

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For light aircraft, full power is normally used during take off. Large transport category (airliner) aircraft will usually use a derated power takeoff, where less than full power is used. The aircraft is permitted to accelerate to rotation speed (often referred to as Vr) and then rotated off the ground gently. The term rotation is used, because the aircraft pivots or rotates about its the axle of it main landing gear when the flight controls are used to change the aircraft attitude. Usually the rotation is approximately 10 to 15 degrees nose up compared to the position of the nose while on the ground. Autorotation is where an aircraft will do precisely this by itself when it reaches some speed.

Related Topics:
Light aircraft - Transport category - Derated power - Landing gear - Flight controls - Aircraft attitude

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Larger planes (such as commercial jet aircraft) have difficulty generating enough lift at the (comparatively) low speeds encountered during take-off. These are therefore fitted with high-lift devices, such as flaps or slats, which increase the lift of the wing at low speed. These are deployed from the front and rear edges of the wing before take-off, and retracted during climb (usually accompanied by a humming noise from the motors that move them).

Related Topics:
Jet aircraft - Lift - High-lift device - Flaps - Slat - Climb

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The speeds needed for takeof are relative to the motion of the air (air speed). A headwind will reduce the ground speed needed for takeoff. Typical takeoff air speeds for jetliners are in the 130 to 155 knot range (150 to 180 miles/hour, 250 - 290 km/hour.) Light aircraft, such as a Cessna 150, take off at around 55 knots (63 miles/hour, 100 km/hour). Ultralights have even lower takeoff speeds. The speed required varies according to many factors, including airport altitude, outside temperature, aircraft gross weight, power setting, and flap position. Pilots of multi-engine aircraft calculate a decision speed (V1) for each take off that dictates action to be taken in case an engine fails. Below V1 the take off is aborted; above V1 the pilot should continue to take off.

Related Topics:
Headwind - Knot - Cessna 150 - Ultralight

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If an obstacle needs to be cleared, the pilot lowers the nose just until the speed for maximum climb angle is achieved, Vx. If no obstacle needs to be cleared, or once an obstacle is cleared, the pilot further lowers the nose to accelerate to Vy, the speed at which climb is the most rapid. At this point the climb phase of flight begins.

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Gliders take-off using a variety of methods, (see article on gliding), but the most common methods are winching-launching and by being towed behind a light aircraft. Helicopters and some specialized fixed wing aircraft (VTOLs) can take off vertically.

Related Topics:
Gliders - Gliding - Light aircraft - Helicopter - Fixed wing aircraft - VTOL

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See aircraft for more information.

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