Takeoff is the first phase of flight, when an aircraft lifts off from the runway or other surface.
Takeoff is when an aircraft lifts off the ground and is the first phase of flight. Takeoff techniques vary depending on the aircraft and the runway or other surface, but a typical takeoff in an airplane has four stages:
- Lining up (or positioning): taxiing onto the runway and lining up with the centerline
- Rolling: applying power and increasing speed to the point where the aircraft is creating enough lift to fly
- Rotation: lifting the nose of the aircraft to initiate the actual lift-off from the ground
- Climb-out: climbing to an initial minimum altitude before making any maneuvers such as turning
Aircraft always take off into the wind if possible, because it reduces the groundspeed required to become airborne; e.g. if an aircraft requires an airspeed of 60 knots to take off and there is a headwind of 20 knots then the groundspeed at takeoff is reduced to 40 knots. A lower groundspeed at takeoff means that the aircraft can lift off sooner, requiring less runway, and also means that less braking is required in the event of a rejected-takeoff.
A departing aircraft lines up on the runway centerline before beginning the takeoff roll, to make sure that in case of crosswinds or control issues there is maximum space available on both sides of the aircraft. The aircraft may start rolling immediately or it may wait on the runway before starting the roll (in an ATC environment, the pilot may be instructed to "line up and wait").
The takeoff roll begins when the aircraft starts accelerating to reach takeoff speed. The required speed can vary depending on the aircraft's configuration (e.g. with or without flaps). When the aircraft reaches takeoff speed, the pilot rotates (lifts the nose) to start the actual flight. Larger aircraft also have a "decision speed" referred to as $V_1$, where the aircraft is not yet able to rotate but has passed the point where it is still possible to abort the takeoff in the remaining runway length.
After rotation the aircraft starts its initial climb and during this phase of takeoff the pilot configures the aircraft for the climb by setting an appropriate airspeed, retracting flaps and undercarriage (if applicable) and performing any other required actions.
This tag is appropriate for all questions about takeoff techniques and procedures, legal regulations on takeoffs and so on.