I seem to have been absent from this forum for a couple of days- I had to check into the local hospital to see what was wrong when I found myself in agreement with one of Nick's posts..........
I have always thought that far too much emphasis was placed on engine failure scenarios, both from aircraft design and crew training points of view. As Nick quite rightly says, most accidents are not caused by engine failures but by some other unanticipatable chain of disconnected circumstances that happen to come together at the wrong time (phew - long sentence!).
Unfortunately for Nick and myself, there is an argument (that I can almost go along with but not quite) that, whilst it is accepted that engine failures do not cause significant numbers of accidents, that is at least one source of accident that can be dealt with pretty robustly by technology / expenditure. Other mutifarious sources of accident are much harder or impossible to fix - so lets concentrate on the ones we can fix!
This opinion seems to be held by those who charter our aircraft, so regardless of what Nick or I think, it must be given credence. Here the S92 appears to score well as its installed single engine power to weight ratio is second only to the AB139. Assuming that modern aircraft's rotor systems are pretty much as efficient as each others, you would think this is a good measure of single engine performance.
But of course things are never quite as simple as that! If we are looking at stay-up-ability in the cruise on one engine, there is little to choose between the 92 and the 225 and, without rigorous analysis my inclination would be that the 92 wins here (ie higher % gross weight at high density altitude at Vy than the 225).
However performance in the OEI OGE hover is a different matter. Surprisingly the 92 is quite bad at this and at around 30 deg C nil wind the 225 has about 1000 lbs better payload than the 92 (which is getting close to zero payload in SAR configuration). For a while I couldn't work out be this could be - surely the 92's rotor system wasn't desparately inefficient, disc loadings are similar etc. Then it dawned on me that in the hover, its the plan view that determines drag to the rotor downwash. Whilst the 225 has the usual Super Puma mediocre sort of drag, the 92, with its flat topped fueslage (is it a discarded design by Shorts Belfast?) and huge sponson area must surely present massive drag to the downwash.
This is very significant to any civil SAR operators. Its rather embarrasing to fall into the sea during SAR training, and even though that engine failure is a pretty remote probability, civil SAR operators that I know limit training to safe single engine hover weights. On the 92 with its current engines that T4.5 limit somewhere just above absolute zero, you just couldn't safely SAR train in other than cold weather - not much use if you live in the Middle East, or even England's south coast on a nice day.
More relevant to the N Sea, this must have some knock-on effect on performance with the approach of the end to performance class 2 with exposure time offshore. During the critical part of an offshore takeoff at low speed before reaching Vtoss, there must be a substantial downwash component to the relative airflow and the 92 is likely to suffer from high drag to airflow from this direction. Just how significant this could be I'm not sure - have SK or EC done any flight testing or even modelling to see how they shape up to the new proposals?
We seem to have got off my favourite subject of windows somehow, but in case anyone was interested, the S92's windows are about 14.5" by 19" whilst the smallest of the 225's are 17.5" by 28". Not interested -well try measuring you shoulder width (hips for the ladies) and see if its more or less than 14.5" - if more then don't forget to twist round on your side before trying to get out of a 92 underwater!