Vr
Target Theshhold Speed (TTS) is calculated as 1.3 Times the stalling speed in the configeration at the time.
How is Vr calculated? Obviously the lee way between stall and Vr will be less than that used for TTS, because the main wheels are still on the ground and the aircraft is still accelerating.
The Question is raised because of the appalling accident recently at Brum, some witnesses have said the aircraft dropped a wing at liftoff so could the EFIS have shown the wrong Vr because of a fault or wrong programming.