Who can be held responsible for compensating the Mountain Lifeflight families, and who is immune from suit?   

Maintenance.  If faulty maintenance is proven to be the cause of this helicopter crash, the families can recover against the maintenance company, provided that the families can prove that the maintenance company was negligent.  There is an important exception, however.  The families cannot sue the company that performed the maintenance if that company was Mountain Lifeflight itself.  That’s because the worker’s compensation laws immunize a crew member’s employer from suit brought by the crew member’s family.  More on that here.

Pilot error.  There is no reason to believe that the crash was caused by pilot error.  To the contrary, as discussed here, it looks as though the crash was likely caused by a mechanical failure.  However, assuming for argument’s sake that the crash was caused by pilot error, the workers’ compensation laws prohibit the families from suing either the pilot’s estate or the pilot’s employer.

Design defect.  Other A-Star accidents similar to this one raise the question of whether the crash was caused by the helicopter’s faulty design.  The families are entitled to sue the aircraft’s manufacturer, Eurocopter, and get to the bottom of the design defect issue.  If the families prove that the crash was in fact caused by a defect in the design of the helicopter, then they can hold Eurocopter responsible.

But there is one hurdle the families must overcome before winning a design defect suit.  The accident helicopter, N5793P, was manufactured in 1982.  The General Aviation Revitalization Act, or GARA, immunizes manufacturers from liability from lawsuits arising from aircraft that are older than 18 years.  At first blush, it would seem that the families have no recourse against the manufacturer at all.  But there is an important exception to GARA.   If the accident occurred as a result of a new part that was installed on the aircraft less than 18 years before the accident, the manufacturer can’t assert the defense, no matter how old the aircraft.  And it has been reported that N5793P had been completely rebuilt only a few years before the crash.  Therefore, even though the helicopter was manufactured more than 27 years ago, it’s likely that most critical parts on the aircraft were less than 18 years old, and that GARA won’t protect the manufacturer.