A balanced field takeoff is a condition where the accelerate-stop distance required (ASDR) is equal to the takeoff distance required (TODR) for the aircraft weight, engine thrust, aircraft configuration and runway condition. For a given aircraft weight, engine thrust, aircraft configuration and runway condition the shortest runway length that complies with safety regulations is the balanced field length.
The rejected takeoff initial actions speed V1, or critical engine-failure recognition speed (Vcef), is the fastest speed at which the pilot must take the first actions to reject the takeoff. At speeds below V1 the aircraft may be brought to a halt before the end of the runway. At V1 the pilot must continue the takeoff even if an emergency is recognized.
To achieve a balanced field takeoff, engine power is selected to provide enough acceleration so that at the lowest possible speed to continue the takeoff the remaining necessary takeoff distance with one engine not working is equal to the remaining & necessary accelerate-stop distance.
The balanced field length is the shortest field length at which a balanced field takeoff can be performed.
Factors affecting the balanced field length include:
- the mass of the aircraft – higher mass results in slower acceleration and higher takeoff speed
- engine thrust – affected by temperature and air pressure but reduced thrust can also be deliberately selected by the pilot
- density altitude – reduced air pressure or increased temperature increases minimum take off speed
- aircraft configuration such as wing flap position
- runway slope and runway wind component
- runway conditions – a rough or soft field slows acceleration, a wet or icy field reduces braking
Read more about Balanced Field Takeoff: Regulatory Background
... Aviation regulations, especially FAR 25 and CS-25 (for large passenger aircraft) require the takeoff distance and the accelerate-stop distance to be less than or equal to the ... The speed below which takeoff must be aborted upon engine failure is called V1 ... the runway length is no longer than the balanced field length only one value for V1 will exist ...
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