As they were on radar, they must have been at altitude - NOT Scud running. I find the implied criticism of the pilot in that assumption unacceptable.
The crash site is on the direct Dundee - Tiree track. Although on radar, there's no mention of a distress call or squawk. Am I correct in thinking both occupants were PPLs, and instrument qualified? When, as a 45 hours solo PPL, I got into cloud on my first trip to Mull, I aviated and my student pilot pax grabbed the mic and communicated. We survived.
Something drastic happened to make this aircraft descend at what hillwalkers described as a steep angle.
Some years ago, south of Inverness, a C172 was turned upside-down, and lost several thousand feet before recovery, in VMC. The airframe was found to be undamaged, but engine oil was lost. That is beyond what IMC unusual attitudes train for.
As they were only about half way, the Tiree weather is irrelevant to the accident, but their timing looks good from the data in a previous post
The accident is reported as about 14.00. That I assume is local - Z+1.
SA 04/04/2015 14:20-> METAR EGPU 041420Z AUTO 31010KT 9999SCT005/// BKN014/// 10/09 Q1025=
SA 04/04/2015 13:50-> METAR EGPU 041350Z AUTO 31010KT 9999 SCT005///SCT015/// BKN024/// 10/09 Q1025