Like many others I've been struggling to make sense of what happened in this accident, with its range of apparently conflicting evidence. As it happens I know a bit more about buildings than I do about helicopters, and I've been wondering just how the rather unusual roof structure of the pub might react to a 3 tonne object falling almost vertically on it. Given that the roof appears in the crash area to be a combination of timber joists laid between two very large rolled steel joists (RSJ), this might be expected, at least initially, to be somewhat "elastic" to something falling on it.
Could it possibly be that the 135 initially landed predominantly above one of the RSJs, damaging its underside but bouncing back into the air briefly before landing back slightly further ahead over the timber section, which it perforated this time?
This sequence might explain those few seconds of silence described by witnesses in the pub as occurring between the initial bang and the main collapse of the ceiling/roof.