SAS,
That paper contains useful information on tail rotor drive failure and “stuck pedals” but it does not cover the very unusual situation suffered by the Leicester crew.
(I can’t imagine a situation where any helicopter in normal operational flight would need full negative tail rotor pitch).
During a normal Class A rearwards climb, such as this was, the pilot would have been applying a large amount of positive tail rotor pitch.
The aircraft mechanical controls failure suddenly gave him the maximum possible opposite tail rotor input. As I said before, I doubt very much that any pilot would have been able to recover from that situation. I’ve seen it in a simulator many times, both as a handling pilot and watching (and trying to assist and train from the instructor point of view).
This was far more severe than stuck pedals or even total loss of tail rotor power through drive shaft failure and even more so because the aircraft was in a low IAS climb, in accordance with that type of departure. The only hope would be to rapidly achieve full auto rotation and even if that was achievable (it probably wasn’t because of the rapid onset of a high yaw rate) the pilot would still be trying to deal with uncontrollable yaw at very low level - and in the dark!
For those pilots not familiar with helicopters, the closest analogy I can think of in fixed wing terms is for an aeroplane with a high torque propellor engine to be in a minimum IAS climb. The pilot is keeping the aircraft straight using ant-torque rudder. A mechanical failure causes sudden full opposite rudder to be applied, causing a high rotational spin to develop with full pro spin rudder jammed on.