New Zealand investigators have highlighted the dangers involved with doors opening in flight following the 2018 fatal crash of an MD Helicopters MD500D.

The helicopter (ZK-HOJ) had departed from Wanaka aerodrome with a pilot and two wildlife officials at 10:53, according to the Transport Accident Investigation Commission’s final report into the 18 October 2018 crash.


Source: Transport Accident Investigation Comission

A loose latch on the left-hand door led to the accident

“The helicopter had just departed from the perimeter of the aerodrome when it started to break up in flight, began spinning while descending near vertically and caught fire after it struck the ground,” says the commission.

The crash killed all three aboard the helicopter. The cause was “very likely” the left-rear door opening unexpectedly and a pair of loose overalls exiting the cabin.

The overalls struck the tail rotor, leading to the tail rotor assembly detaching from the boom and striking two of the helicopter’s five main rotor blades.

“That caused the outer sections of those two adjacent main rotor blades to break off,” says the commission.

“The tail boom was then struck by a main rotor blade and subsequently failed, resulting in the tail section separating and the helicopter becoming uncontrollable.”

The comission estimates that the entire sequence took 14s.

In its report, the commission states that left-rear door’s latch was worn and outside the manufacturer’s tolerances.

It also observed that the operator, Alpine Helicopters, did not have a policy of securing items within the cabin. Moreover, there were no requirements to report door-opening events, suggesting a lack of understanding about the potential consequences.

“A helicopter door opening in flight presents a significant risk to the helicopter and its occupants,” says the commission.

“It is important that pilots report all incidents of doors opening unexpectedly in flight. Unsecured items in helicopters can be fatal. Doors opening unexpectedly in flight are a known risk, which is why pilots should ensure all items are appropriately secured.

Following the crash, MD Helicopters updated is manual and guidance for doors. The operator also requires pilots to secure items in cargo pods in or in special bags under the seats.

“The lessons drawn from this tragic accident are that pilots must promptly report any unusual events when airborne, and operators need to enforce stringent cargo securing practices; aircraft manufacturers should provide clear instructions for maintenance, and regulators should ensure regulations are clear to all concerned,” says the commission.