What happened
At 1241 local time on 14 September 2025, a Kawasaki Heavy Industries Ltd BK117 C‑1 helicopter with a crew of 3 lifted off from the operator's base in La Perouse, New South Wales, for a local search and rescue flight. Shortly after lift-off, at a height of around 50 ft, the cabin sliding crew door separated from its lower track while the rescue crewmember was holding on to the internal door handle. The door remained in position against the airframe and the crewmember continued to hold the door handle while notifying the pilot of the situation. The pilot immediately commenced a right orbit, climbing clear of the take-off zone before descending and returning to the base for an uneventful landing at 1242.
After the helicopter was secured on the ground, the rescue crewmember was able to re‑seat the door in position on its tracks, and after confirming it was properly closed, the flight resumed the intended mission at 1250.
Door information
The BK117 crew cabin sliding door operates on upper and lower tracks (Figure 1), with front and rear sliding elements running along an upper recessed track. At the door base, front and rear guides engage with an inverted lip and are held in position with sliders on flexible plates.
The crew door is designed to be jettisoned from the helicopter in emergency situations – this is achieved by an internal actuating handle which retracts the 2 upper track rollers, freeing the door from the upper track and allowing it to move outward and downward away from the airframe.
Figure 1: BK117 crew door track detail
Source: Section of Figure 4 from Eurocopter Alert Service Bulletin ASB-MBB-BK117-20-111, annotated by the ATSB
Engineering inspection
The operator reported that an engineering examination of the door mechanism and tracks had found the door sliders and guides to be in a serviceable condition, with no wear exceeding permissible limits. The 2 upper track rollers were found with localised surface wear (flat spots), however, due to the design of the track, this damage would not have affected the door’s security.
The operator’s internal investigation concluded that the door’s emergency jettisoning mechanism had not been activated, however the factors contributing to the door separation had not been identified.
Safety message
Accidents and serious incidents have resulted from the separation of the BK117 crew access door, with the potential for door impact with the main and/or tail rotor assemblies presenting a serious risk to the safety of flight.
Operators and crew of BK117 helicopters and other aircraft with jettisonable doors must ensure that the jettison mechanisms are protected from inadvertent activation during flight.
Periodic inspection of the door operating and jettisoning mechanisms must be conducted in line with the manufacturer's published documentation and service bulletins.
Specific attention is drawn to European Union Aviation Safety Agency (EASA) airworthiness directive AD No. 2011-0107 and Eurocopter (Airbus Helicopters) Alert Service Bulletin ASB-MBB-BK117-20-111 (and related documents) for issues and actions relating to the security of the sliding cabin door.
About this report
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.