In addition to what ericferret was saying: People need to consider the reliability benefits of modern technology.
When I flew the SK, for every hour airborne, it needed approx 10hrs maintenance. When the Merlin came into service every hour airborne required 80....yes 80hrs maintenance. I believe (talking to my neighbour who is a Merlin AEO that this figure is now down to around 45-60hrs.
I am led to believe the S92 is around 4hrs maintenance for every hour airborne.
When I flew the AS355 the ratio was 1 airborne: 2 maint. Then I flew the EC135P1: 1hr airborne to 45 mins maintenance.
The 139 and 189 have the same cockpit (ish)...how logical is that
Only took 60yrs to work that one out.
So 8 engineers will suffice for 95% of the jobs at site. A floating crew sweeps up the rest.