Helicopter
Flight Crew Commercial; Flight Crew Rotorcraft
Other / Unknown; Situational Awareness
Aircraft Equipment Problem Less Severe
Flight Crew Overcame Equipment Problem
Aircraft; Human Factors; Procedure
Enroute and [accident scene] landing zone (LZ) arrival conducted in daylight and return flight was completed in dusk light conditions. Medical crew had requested rooftop shutdown for offload of intoxicated patient and shutdown on rooftop LZ was uneventful. Shift Supervisor and additional security personnel were present and pilot assisted medical crew with offload. Pilot secured and physically checked all doors starting on left side around to pilot door on right side and visually inspected all panel latches during a concurrent walk-around inspection. Pilot entered cabin on aircraft right side (behind pilot seat) to shutoff cabin lights left on by medical crew and observed both flight helmets; one located on forward-facing right seat and the other on aft facing left seat. Pilot door remained open during normal startup and was closed after checklist completed for reposition to lower parking LZ. Pilot observed DOOR annunciator light go out with yellow VAR NR and green LANDING LT indications remain on (normal for aircraft takeoff condition). No abnormal noise or other indications were noted. Pilot executed normal takeoff and VAR NR light out upon application of power. Shortly after transition to forward flight and airspeed increase pilot noted minor abnormal vibrations with excessive rotor noise. Pilot had already initiated right turn for reposition to parking LZ and noted vibrations worsened with increased airspeed; however pilot observed no warning or system indications of a problem. Pilot then analyzed vibrations to possibly be a result of a cabin window left open by aircrew and opened pilot door window in an attempt to equalize pressure. Problem persisted and worsened with continued acceleration; pilot reacted with power and airspeed reductions and continued to monitor system status and annunciator lights for any abnormal indication. LANDING LT and no others were on and pilot made a normal landing to parking LZ. Upon landing pilot exited aircraft for walk-around and noticed left cabin door had opened and slid full aft. Normal shutdown completed and further inspection revealed flight helmet on aft-facing left side was missing. Pilot completed post-flight and walk-around and immediately notified [appropriate authorities]. Hospital Shift Supervisor notified campus police who indicated they would notify local police. Area Manager arrived and received a verbal report from incident pilot. Shift Supervisor elected to take aircraft and aircrew out of service for remainder of shift (1 hour early) and accompanied pilot for brief ground search in vicinity of flight path. Helmet was found in close proximity to departure point and at same approximate point pilot initiated right turn for downwind. The lesson is that if something doesn't feel right despite absence of any system or annunciator indication; believe what you feel and what your gut instinct tells you. Be prepared for anything and above all stay focused while you FLY THE AIRCRAFT.
Medical helicopter pilot reported encountering vibration and elevated noise level after rooftop liftoff and during descent to lower level landing area. After landing; pilot discovered left cabin door had come open inflight and a loose crew helmet had departed the aircraft.