Regarding the pubs. Many are provided in the form of 'handouts' during training and, yes, you are right, they are not maintained. (As a matter of policy, so few are). But in this context (XX177) I'm talking about basic engineering that hasn't really changed for centuries. The AP that tells you one thread showing, not the 1.5 mentioned by MoD and HSE. (Apply that, and Sean Cunningham would be alive).
MoD has created a problem for itself by continually re-inventing the wheel. We lost our specialist Technical Authors (used to be around 600) and we now have contradictory regulations (e.g. 1.5 threads). Also, if the good book says to use a new stiffnut when loss of torque could lead to the loss of the aircraft, you really shouldn't need to spell out that this also applies to where loss of life could result, but the aircraft survive (e.g. this ejection). Note: stiffnut, not locknut, the term used by the SI. It's important to understand the difference when lives are at stake. And now that I've said this on MoD's Corporate Knowledge website, there will be a frantic re-assessment of said book and in a year's time a quiet amendment. As ever.
The trouble here is overlap, the RAF and the UK always has had a standard of 1 1/2 threads showing, remember, go back 50 years and we were a, if not the leading supplier of aircraft to the World, and the British standard was 1 1/2 threads.
The problem comes when the US started to dominate the industry and their 1 thread standard came into play, the likes of Martin Baker as a global player will have produced their goods to fit the standards of what must be their largest market. The RAF are then in a position of do you teach the 1 thread or 1 1/2 thread standard and bearing in mind that up until lately some aircraft still in service would be using the stricter tolerances, then surely that is the one to teach ( or both), if a bolt is to be tightened to 1 1/2 threads showing but is tightened to the lower figure then the potential is there for a bolt to be undertorqued.. So I can totally understand why accidents like this happen.
A stiffnut is a lock nut, they are one and the same thing, just different terminology, similarly a cotterpin is the same as a splitpin... push bikes apart.
While in the RAF I was taught and still adhere to the principal to replace all used stiffnuts, that was not always the case civilian wise as you could check it still retained a rundown torque.
note.
Advantages of the all metal lock nut are heat and wear resistance. Military and aircraft standards allow this particular style of locknut to be reused up to 15 times, given that the nut will continue to provide some minimum specified prevailing torque (United States' Military Standard 'Mil Std' MIL-N-25027).
http://mgaguru.com/mgtech/restore/rt104d.htm