Perhaps I can provide a little input to the ongoing discussion over SI reports and the MAAIB.
I absolutely agree that the aircraft accident investigators have to be independent of those carrying out Service Inquiries. In the past (in one service) they were, to a degree. The RN's arrangements for Boards of Inquiry into accidents ran something like this:
1. FONAC (FAA's two star) would direct that a Board be convened, normally within 24 hours of an accident. Board members would be drawn from units and stations not involved with the accident.
2. President of Board decided whether an investigation was required, and if so (almost always) the RN's Accident Investigation Unit (AIU) would be requested to carry out said investigation. Usually within hours of FONAC order.
3. Board of Inquiry suspended.
4. AIU carried out investigation, prepared report, submitted report to Board of Inquiry.
5. Board reconvened, carried out Inquiry using AIU report and calling witnesses as required. Report of the Board, submitted to FONAC, referenced the AIU report.
The thing to note was that the AIU reported to a two star post in MOD(RN), not to FONAC. Also note that their report was compiled independently, and always sat separately to the Board's eventual report.
Also note that Haddon-Cave explicitly praised the RN's system for accident investigation, and recommended it as a template for use across military aviation. Downstream staff work and plain skulduggery ended up creating the MAAIB as an integral part of the MAA, and resulted in the almost unreadable SI reports we see these days.
I'll say here that I don't for one moment claim that the RN system was perfect. But, the independence of the AIU within the setup was well understood and respected across the FAA, as was the expertise within the AIU. It's no surprise that the main horsepower of the MAAIB came from the AIU. (It's also no surprise that the new MAAIB required a full Colonel in charge, against the Lt Cdr who very effectively headed up the RNAIU).
The current 'fix' whereby the MAAIB answers to the three star head of the DSA is better than it being part of the MAA, but not much, as it still locates the MAAIB within the organisation that 'owns' the MAA. This inhibits it from presenting criticism of the MAA. Also, incorporating MAAIB activities within the SI process compromises their independence.
My suggestion - remove the MiAAIB from the DSA, establish it as a separate agency reporting direct to SoS for Defence. SIs call on it as required, and MAAIB reports are prepared and published as separate documents.
Best Regards as ever to all those accident investigators making the system work as best they can,
Engines