Answering the question directed at me:-
Just a smallie for Genghis - is it lawful for me to leave the cluster on my Schweizer 269, G-DRKJ unpainted - just varnished. I know that I couldn't detect the crack on G-ZAPS through the paint and a little dirt. So that is MY FIX. I hope not wrong.
Since you've asked the question publically, I have to publically say I've no rotary wing maintenance qualifications - any RW engineering training I have is on the design and certification side, so no idea about the specific legalities I'm afraid.
Having said that, I have regularly in my certification work refused engineering designs specifically because surface treatments were used in fatigue critical areas that I considered had significant potential to hide cracking or (equally seriously) corrosion.
There are specific aircraft surface treatments available that will crack with the substrate (underlying material) and I'd certainly recommend you check what's (a) available, and (b) approved for your aircraft.
Incidentally, dry dirt is a wonderful crack detection tool. It is amazing how often fatigue cracks show up in the surface muck as lines of different colour, long before the crack is visible to the naked eye. I'm a great believer in a qualified person inspecting an airframe immediately before it's washed.
In a wider context
Mr Kenyon. Like many people I've lost friends and colleagues in aviation accidents; however, despite that I can only guess at the personal impact that the loss of your son has had. Could I take an opportunity to express my respect for your approach and attitude, when a lesser man might have simply walked away and tried to forget, or simply descended into vitriol.
If I can be of any assistance in what you're trying to do, not as a rotary wing expert - which I'm not particularly, but as somebody who is a CAA whole-aircraft design signatory and thus familiar with the processes, competencies and personalities that surround this whole thing, as well as a degree of professional credibility as an aeronautical engineer then please drop me an Email.
We all have to detail with the CAA, and this underlying attitude, competence (or lack thereof) and approach needs knocking on the head before it further impacts other areas, as much as for the safety of Hughes 300 crews.
G