Balanced Field Length (BFL) ≈ Aeroplane Reference Field Length (RFL)

[Ref AC 120-62 (FAA), ISBN: 978-0-470-74077-4, CASA (Australia)]

What’s Balanced Field Length (BFL)?

Balanced field length is a field length where the distance to accelerate and stop is equal to the take-off distance of an aeroplane experiencing an engine failure at the critical engine failure recognition speed (V1). (definition of CASA, in Australia) 

Balanced Field Length refers to the runway length (or runway plus clearway and/or stopway) where, for the takeoff weight, the engine-out accelerate-go distance equals the accelerate-stop distance.  (by definition in FAA AC 120-62)

Balanced Field Length (for a given takeoff weight) is defined as the distance required to accelerate to V1 and safely stop the aircraft on the remaining runway or continue the takeoff so as to reach V2 by 35 feet above the takeoff surface at the end of the runway. (reference from  ISBN: 978-0-470-74077-4)

Another way to describe BFL is that TODA = ASDA, the end of the clearway is the stopway.


Takeoff distance available (TODA)

  • length of the takeoff run available plus the length of any clearway available
    (TODA = TORA + clearway)


What’s Aeroplane Reference Field Length (RFL)?

Aeroplane reference field length is the minimum field length required for take-off at 1) maximum certificated take-off mass (MTOW), 2) ISA – sea level, standard atmospheric conditions, still air and 3) zero runway slope, as shown in the appropriate aeroplane flight manual prescribed by the certificating authority or equivalent data from the aeroplane manufacturer. Field length means balanced field length (BFL) for aeroplanes, if applicable, or take-off distance in other cases. (definition of CASA, in Australia) 


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