ACCIDENT RECOVERY


into the main-rotor disc, snapping the outermost 500 mm (20 in.) off two blades. This tilted the main-rotor disc out of its normal plane until the main rotor severed the tail boom, rendering the aircraft uncontrollable. The left rear door was wrenched from its hinges as the aircraft spun and was also struck by the remaining main-rotor blades. As the helicopter slowed, the remain- ing cargo was flung from the opening the door left behind. The entire chain of events, from door opening to final impact, lasted barely 20 seconds.


The Response After the accident, the TAIC was informed that doors on the same helicopter had opened on four other flights in the preceding two weeks. One involved the left rear door, the other three the right front. None were reported via the operator’s safety management system or recorded in the ship’s technical logs. All were resolved safely after precautionary landings. In an interim report in December


2018, the commission issued safety recommendations that included a reminder of the importance of reporting accidents and incidents. Nationwide, reports of doors opening increased thereafter but quickly tailed off again, dropping from 42 in 2019 to just 14 in 2022. Interviews with maintenance staff


found that they were unfamiliar with the manual chapter that detailed procedures for inspecting door seals, latches, and hinges—perhaps because that chapter was listed as specific to three related models but not the MD 500D. Routine checks during 100- hour inspections largely consisted of latching the doors, then trying to push them open from inside. The manufacturer stated that


62 POWER UP SEP 2024


all parts eligible for replacement on condition—that is, without service-time limits—had a minimum life of 20,000 hours. The door latch assemblies in the accident helicopter were original to the aircraft, which had flown almost 19,500 hours. The mechanism in the left rear door,


which largely escaped damage, and those in the other three doors (intact aside from fire damage) all showed enough wear in the various latches and linkages to create significant “slop” in their operation. In response, MD Helicopters revised


its maintenance manual to clarify and detail procedures for checking the “proper operation of latching and lock- ing mechanisms.” The TAIC found that this adequately addressed the safety risk and declined to issue further recommendations. The 2018 interim report also called


attention to the risks posed by keeping loose items in the cabin. The operator generally didn’t secure cargo in the MD 500D when it was flown with the doors on, instead trying to pack items tightly enough to prevent them from moving in flight. They had previously experimented with cargo nets but found that they created other hazards (not specified in the report). Following the accident, they fitted the replace- ment helicopters with cargo pods mounted between the skids with their contents packed in heavy plastic zip- pered bags. New Zealand’s civil aviation author-


ity (CAA) issued a safety message in November 2018 reminding operators to secure loose items in helicopter cabins, a response the TAIC found sufficient to address the immediate safety risk. Finally, to guard against “risk nor-


malization of helicopter doors opening in flight,” the commission made a safety recommendation to the CAA


on Dec. 12, 2018, urging the authority to remind operators of their obligation under Civil Aviation Rules (CAR) Part 12 to report accidents and incidents. The CAA accepted this recommendation and issued a series of related publica- tions in 2019 and 2022. In addition to detailing the regulatory requirements, the CAA assured operators that their reports would not serve as the basis for any enforcement actions unless “reporting is patently incomplete or reveals reckless or repeated unsafe behavior.” The TAIC also recommended that


the CAA “revise the rules, notes, and guidance” to CAR Part 12 “to make it clear that a door opening in flight is a safety issue and to take steps to address occurrences that are not being promptly reported to the CAA.” The CAA agreed to revise the notes and guidance but considered a rules change to be beyond its jurisdiction, referring the commission to the sec- retary for transport. Accordingly, on Jun. 12, 2024, the TAIC forwarded its recommendation to the secretary.


The Takeaway “The trouble with getting away with something,” it’s been said, “is that it makes you think you’ll get away with it.” Door latches aren’t the most critical systems of a turbine helicopter, but their failure still carries potential for mayhem. An open door can usually be handled without much drama … usually. Cargo wedged against the cabin


structure ought to stay put unless turbulence shakes something loose or that structure suddenly changes. And incremental increases in multiple risks can ratchet up the overall level of haz- ard to an extent that may be difficult to appreciate at the time. David Jack Kenny is a fixed-wing ATP with commercial privileges for helicopter.


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