Crab, compliance with the gross weight and torque limits may not guarantee safety.
And why not?
It is probable that UK military qual procedures are very similar to US, and in the respect I shall address, that probably is true for the FAA vs CAA processes.
In that qualification process, a flight loads survey is done which, with the approval of the pertinent authority, represents the usage spectrum of the machine in service. The flight loads thus collected are matched against the ground test lab test loads and the component replacement times are established.
But the logging usage spectrum is far different than the military or civil usage spectrum, and so there are problems. There are also some subtle, some not so subtle differences in flying techniques. The so-called " Wenatchee Snatch " maneuver employed by some S-61's is not fiction, and was certainly never envisioned by the USN SH-3 nor the LAA or NY Airways 61 operators is one example. Some sites required logging S-64's to make every max weight approach at a steep/slow condition, ensuring very high N/rev vibration ( and no, not VRS ) and associated loads. They experienced some sheet metal fatigue problems never encountered by the Army. Just a couple of examples.