Honest inquiry:

Has anyone been privvy to whether a flight helmet has saved a pilots life? Not fixed wing, but helicopter. 

Thanks. 

Someone did a study once, military it was, I believe.  
the results were significantly in favor of helmets... hence all military helicopter pilots wear helmets... with the exception of Marine one. 

https://apps.dtic.mil/sti/pdfs/ADA372992.pdf

We can only trade anecdotes and personal opinions because:

We probably would not ever find empirical data, peer reviewed, and transparently disclosed.  (Which is what it takes for me to have a firm conclusion in the current culture.)

Anecdote #1:  In Army flight school, they had quite a presentation showing example after example documenting actual accidents and they had the actual helmets available for students to see and touch afterwards.  This was very compelling in favor of helmets. 

Anecdote #2:  I know of one accident where the survivor was wearing a helmet (found to be badly cracked) and one of the decedents was not wearing a helmet nor a seat belt.  The unprotected decedent was same-day released from the hospital and collapsed dead in the ER parking lot -- from a Subdural Hematoma.

Opinion #1:  There is a very significant amount of data proving that full-face motorcycle helmets do indeed save lives. Does this make a believable analogy for helicopter helmets???  My opinion is that it does.

Common sense:  The more protection, the safer we are in aircraft.  There is a practical limit to the amount of protection, but it probably should extend to include helmets.

I know of at least two bird stike incidents that pilots got hit in the face after birds came through the windscreen. Luckily in both cases visors were down. 

It was reported where a pilot died because of facial trama from the cyclic and he was not wearing a helmet.

pretty tall cyclic

Military; co pilot helmet came off, he died, everyone else, minor injuries.  EMS, engine failure hard landing, nurse helmet came off, lived but head injury, everyone else walked away.  I think they work, some designs are better than others, and they have to be fitted and worn correctly. 

There's lots of data supporting the life saving benefits of helmet use in helicopters. If youre looking for supporting documentation to put together a presentation or support safety equipment contact Delta P Aerospace Physiologist   delta-p.com