Emergency Inspection Called by NTSB for Bell 407 Helicopters

The board urged the FAA and Transport Canada to order examination of tail boom assemblies.

The National Transportation Safety Board (NTSB) is urging immediate and more frequent inspections of Bell 407 helicopters stemming from an accident that took place in Hawaii in June involving a tour helicopter.

The recommendation issued Friday asks both U.S. and Canadian aviation regulators to require both immediate and more frequent inspections of certain components on Bell Textron Inc.’s Bell 407 helicopters.

According to the NTSB, the crash of a Bell 407 near Kalea involved an inflight separation of the tail boom. The main wreckage of the tour helicopter was found 700 feet from the tail boom which came down in lava-covered terrain.

Tail boom with fractured remains of attachment fittings and hardware. Upper-left attachment hardware (bolt, washers, and nut) was not present. The lower left, lower right, and upper right attachment hardware (bolt, washers, and nut) remained installed. [Courtesy: NTSB]

The pilot and two passengers were seriously injured in the crash. Three other passengers received minor injuries.

“We’re calling on regulators to act immediately—before there’s another accident,” stated NTSB Chair Jennifer Homendy. “With hundreds currently in service, the Bell 407 helicopter is a popular model among tour operators, police departments, air ambulance providers, and many others, which is why our finding is so urgent.”

Investigation Leads to Recommendation

During the examination of the helicopter wreckage, the NTSB found that the upper left attachment hardware—installed in one of four fittings that attaches the tail boom to the fuselage—was missing and could not be located at the accident site. The remaining three fittings and hardware were found with the tail boom, and one fitting had multiple fatigue fractures and two fittings presented overload fractures.

In the recommendation the NTSB noted, “There may be additional Bell 407 helicopters with missing or fractured tail boom attachment hardware, and the potential for catastrophic failure warrants immediate and mandatory action.”

Aft fuselage with upper-left tail boom attachment fitting. [Courtesy: NTSB]

The current inspection interval for the tail boom per the manufacturer’s recommendation is 300 hours. The NTSB noted the accident occurred just 114 hours following the last inspection of the helicopter tail boom and did not turn up any anomalies. 

The NTSB is urging the FAA and Transport Canada to require Bell 407 operators to conduct an immediate inspection of the tail boom attachment hardware and to reduce the inspection interval from 300 hours to a more conservative number to “increase the likelihood of detecting fractured attachment hardware before a catastrophic failure can occur.”

The NTSB further asked the aviation regulators to require the operators to report their findings to their respective regulatory authority.

The NTSB released the preliminary findings on the accident earlier this year. The final report has yet to be compiled.

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