V1 is the takeoff decision speed, following critical engine failure, from which a decision to continue results in:
- a takeoff distance tp a height of 35ft at V2 that won't exceed the usable takeoff distance
- the speed from which a decision to bring the aircraft to a full stop will not exceed the accelerate-stop distance avaialble
For some takeoff performance calculation modules, when the parameter for V1/Vr Choice is set to 0, a range of v1 is calculated. Most output options however only present one v1, so a choice has to be made. By default, the printed v1 will be the balanced field v1 when it's within range. If a balanced v1 does not lie in the valid range, either minimum or maximum v1 will be printed, whichever is closer.
When a range of v1 is available the 'user' (performance department or IT engineer) can specify which v1 to print based on a scale of 0-1, thus:
v1(printed) = (scalar x (v1 max - v1 min)) +v1 min
Output Calculation Example:
MTOW 75000 based on:
Field limited 78438
Tire Speed Limited 86183
Climb Limited 75000 (2nd)
Obstacle Clearance Limited 75426(V1 min), 77380(V1 bal) 77899(V1 max)
Brake Energy Limited 86183(V1 min) 86183(V1 bal) 86183(V1 max)
Speeds for MTOW:
V1 min = 141.8
V1 bal = 148.8
V1 max = 150.6
Vcmg = 99.3
Vmbe = 168.9
Vr = 150.6
V2 = 155.7
Notes:
Minimum V1 is limited by obstacle clearance
Maximum V1 is limited by Vr
One Engine Inoperative Runway Distances:
Takeoff Run 8266 (V1 min) 7390 (V1 std) 7176 (V1 max) 8765 (Available)
Takeoff Distance 9030 (V1 min) 8154 (V1 std) 7940 (V1 max) 9065 (Available)
Accelerate-Stop Distance 7344 (V1 min) 8154 (V1 std) 8376 (V1 max) 8965 (Available)