The National Transportation Safety Board issued urgent recommendations on Friday asking American and Canadian aviation regulators to require both immediate and more frequent inspections of certain components on Bell 407 helicopters.

“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,” said NTSB Chair Jennifer Homendy. “We’re calling on regulators to act immediately – before there’s another accident.”

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.

In the report containing the urgent recommendations, the NTSB said it was “concerned that 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.”

The NTSB also 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, the agency 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.”

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

The report is available at https://www.ntsb.gov/investigations/AccidentReports/Reports/AIR2210.pdf.

The preliminary report​ ​for the ongoing investigation of the Kalea, Hawaii, accident was published June 22. The public docket for that accident was opened Oct. 31.