What Is a "Fully Stalled" takeoff?
A &quot;fully-stalled take-off&quot; is an attempted takeoff where the elevator has too much authority. This can cause the aircraft to rotate to an excessive nose up attitude, which can exceed the stall angle of attack, before takeoff speed is attained.
Ventral fins were added to some B707s to improve yaw control, and prevent over-rotation. Over rotation which could lead to a &quot;full stall at takeoff&quot;.
https://en.wikipedia.org/wiki/Boeing_707

The British Air Registration Board refused to give the aircraft a certificate of airworthiness, citing insufficient yaw control, excessive rudder forces, and the ability to over-rotate on takeoff, stalling the wing on the ground (a fault of the de Havilland Comet 1). Boeing responded by adding 40 inches to the vertical stabilizer, applying full instead of partial rudder boost, and fitting an underfin to prevent over-rotation.