ELBA — A federal warning about tail rotor issues with Bell 429 helicopters was issued the same day as Tuesday’s fatal Mercy Flight crash off Norton Road.

The Federal Aviation Administration issued an updated Airworthiness Directive requiring inspection of the tail rotor pitch linkage assemblies and replacement of some of the related bearings.

Its wording described the condition as unsafe, saying it involved “certain Bell Helicopter Textron Canada Limited…Model 429 helicopters.”

If left untreated, the condition could lead to loss of control, the guideline reads.

Mercy Flight pilot James E. Sauer and instructor pilot Stewart M. Dietrick of Bell Helicopter were flying in a Bell 429 belonging to Mercy Flight on Tuesday around 1 p.m. when witnesses reported hearing a loud boom before discovering the crash.

The helicopter’s tail rotor was found approximately 300 feet from the main wreckage in a debris field approximately 2,000 feet long. National Transportation Safety Board officials said he separated at some point during the incident, but they did not determine when.

The wreckage is sent to a facility in Delaware for analysis as investigators try to determine the cause of the crash.

A tail rotor compensates the torque of the helicopter’s main rotor. A helicopter will quickly develop control difficulties if its tail rotor becomes ineffective.

The airworthiness directive was to come into effect on May 31.

He cited the close examination of the affected helicopters’ pitch link assemblies for cracks or deterioration of the bearing liners, or axial or radial play in excess of allowable limits, as well as the thickness of the sealant.

A first report on the Elba crash is expected in about a week, and a final report will be released in about a year.

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