The ITV online report currently gives the most detail about this sad event.
ITV - Derriford accident.
When compared to the routine air ambulance visits there is not much to choose between S-92A and AW189 downwash. These are not the largest visitors as there is a report on a Merlin having landed there. It appears to me that the shape of the pad and the surrounding ground is more complex than most ground level helipads and there is a possibility that may have played a role in what seem to be TWO accidents resulting from the same hazard.
Whatever the details, having sat through a number of reports and presentations about people being blown over to their deaths by helicopters, I hope that this is the moment that more people in the UK, and elsewhere, take this hazard more seriously. When I write 'more people', I mean the CAA, the MCA, aircraft operators, local authority planners and hospital management. (In my experience, SAR Commanders have been particulary attentive to the hazard their downwash produces during take-offs and landings. However, the whole point of our national SAR regulations is that it shifts the risk profile for the benefit of the person rescued.) At SMR, and our friends at MREW & MRI, this hazard is already taken extremely seriously and it is thoroughly briefed for and trained for whenever possible.