NTSB calls for immediate inspections of Bell 407s


The accident aircraft’s tail boom with the 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. NTSB Image

The U.S. National Transportation Safety Board (NTSB) has issued urgent recommendations asking American and Canadian aviation regulators to require both immediate and more frequent inspections of certain components on Bell 407s.

The NTSB identified the urgent safety issue during its ongoing investigation of the June 8 crash of a Bell 407 near Kalea, Hawaii, in which the tail boom separated from the fuselage during an air tour flight. In that accident, investigators located the tail boom more than 700 feet from the rest of the helicopter, which crashed in lava-covered terrain. The pilot and two passengers were seriously injured; three other passengers received minor injuries.

An examination of the helicopter wreckage revealed 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, one fitting with multiple fatigue fractures and two fittings with overload fractures.

What you need to know

The NTSB said it is concerned that there may be additional Bell 407s with missing or fractured tail boom attachment hardware, and the potential for catastrophic failure warrants immediate and mandatory action.

The accident aircraft's aft fuselage, with the upper-left tail boom attachment fitting. NTSB Image
The accident aircraft’s aft fuselage, with the upper-left tail boom attachment fitting. NTSB Image

It said the 300-hour inspection interval the manufacturer required for the tail boom attachments may not detect missing or fractured hardware before the tail boom separates from the fuselage, since the accident occurred just 114 hours following the last inspection, which did not turn up any anomalies.

Accordingly, it has urged the Federal Aviation Administration 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.”

Aviation regulators should require the operators to report their findings to their respective regulatory authority, the NTSB said.

  
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