There's a lot of talk in the little aeroplane world at the moment specifically about this accident and report...
https://assets.publishing.service.go...GARB_02-18.pdf
Not unusually for little aeroplane accidents, the paucity of data means that investigators can at best just offer some indications of possible cause, and there's no certainty to this. However, the suggested "least unlikely" cause is that there was an inadvertent sudden input on a mechanical pitch trim lever located between the seats.
The argument if not overwhelming, is strong. AAIB show that a 2.7cm trim lever movement could create 2g (delta 1g), and there was 7.2cm of movement left. A very crude extrapolation says that therefore full sudden back-trimmer might have caused a delta-g of about 3.4g from 1g. Limit load is 4g, and you'd expect a 1.5 safety factor.
So, in an aeroplane that you'd expect to suffer catastrophic structural damage at 6g or thereabouts, this sudden pitch trimmer input might have caused around 4.4g. And of course, all of this is very much in the "gross extrapolation" area, so a structural failure in this way certainly doesn't look impossible (nor does the possibility that this is a complete red herring of course).
So - question. has anybody seen anything of this nature in certification / testing / other types. The potential for a problem does at least seem to be demonstrated by this AAIB report. Also the fact that the vast majority of aeroplanes with mechanical trim systems use wheels - where it's physically impossible (usually) to make sudden step trimmer inputs, suggest that somebody has thought along these lines before.
Has anybody any prior experience of the issue, or any useful thoughts they care to share?
G