Nick, the aircraft was a RN Sea King and they were going on a long range job (about 240 nm from the Scilly Isles). They calculated that flying at their Vmax (the term used in our Operating Data Manuals) they would not have enough time on-scene for the winchman to recover the casualty.
So, rather than accept that they could not do the job (The rescue coordination centre would have then sent an RAF Sea King which has better range) they flew in excess of their calculated figure (probably around 105kts at MAUM) to improve the situation. Once they had completed the job (and flown home from the hospital in a technically unserviceable aircraft) they justified their exceedance of the Vmax by stating that it was inside the manufacturers 10% allowance. No such allowance exists in the Release to Service or the Operating Data Manual.
Discuss....