Mandator,
Thank you so much for coming back with this - I could (and should) have done that search myself. Accept my apologies for not doing so.
Looking at the list, there are a number of varying formats and types of DAOS approvals here, which is what you'd expect. Some are general in nature (e.g. 'Aircraft' for BAES), some are specific (look at the approval for Boeing UK). Some are highly detailed down to subsystems (e.g Honeywell).
The one for Marshalls at Cambridge is fairly sketchy, though. it reads:
a. Modifications and special installations in fixed wing aircraft.
b. Modifications and special installations in Viking Glider aircraft
c. Modifications and special installations in helicopters.
d. Special test and support equipment for items a,b and c.
e. Flight testing. Authorised flight testing is Ltd to: Quantitative assessment of aircraft performance and avionic and engineering systems on fixed wing aircraft.
What I can't see there is anything to do with being an approved DA for the Viking structure, or the aircraft, just 'mods and special installations'. There's nothing in the list for the Vigilant, nor do Grob or Slingsby appear elsewhere.
So. The follow up question to all you PPruners out there (including anyone involved in this cluster***k who might want to open up a little) is this. Who is the Approved Design Organisation for the Viking and Vigilant aircraft? Put another way, who issues their Certificates of Design? Or put another (possibly less fair) way, has the RAF been operating these aircraft without an ADO? If the answer to the last is 'yes', one has to then ask the question WTF?
Best Regards as ever to all those who help the discussions along
Engines