Hi Phantasm,
The Police and HEMs Guys wear helmets principly as a result of a Police SE Jetranger crash in Glasgow which I believe hit a building and a crewmember died as a result of a head injury. It is now a requirement in the PAOM and the Exemptions for HEMs.
North Sea Pilots do not wear helmets (With the exception of SAR crews), despite the fact that during the Brent spar crash it was reproted that one of the crew was incapacitated by a bump on the head during the impact with the sea.
Also reported in the Cormanrant alpha disaster that the co-pilot (who survived the crash) was believed to have subsequently become incapacitated by a bump on the head whilst in the sea, believed to have been caused by the liferaft flipping over and possibly the inflation bottle hitting his head.
However, many NS pilots do not wish to wear helmets as the sheer length of time spent in them would be very uncomfortable and for the PAX which do not wear helmets it would look strange to them loking forward at 2 pilots wearing helmets.
My undersrtanding of the Regulators view is that the requirement to wear helmets is a function of the risk assessed during the tasks that the helicopter is undertaking. Powerline work, Police and HEMs all been subjected to different risks than say the North Sea crews are during the course of their work.
The North Sea may be viewed as being the closest helicopter relative of the scheduled airline services, but with one very notable exception, we operate to Performance Class 2 (With Exposure Period during Landing and Take-off offshore) which effectively means that in extermis, if a engine fails, the helicopter will crash (In extremis remember).
The risks of this crash ever happening are mitigated by other operational requirements of the both the machine and the crew,. For example, the helicopter and engines must have a reliability programme in place supported by an on board Health and Usage monitoring System and the profile flown must be acceptable to the Authority (which is based on computer modelling to minimize as much as possible the exposure period during landing and take-off).
These requirements seem to work well when applied by a responsible operator.
As an ex Army Pilot who has also worked Police and HEMs it did feel very strange to start my North Sea career with a pair of HI-FI headsets on my lugs, but taken on balance I would not welcome a move to helmets for the job I am now doing.
Hope this helps clarify the arguments somewhat.