European regulators have raised a new roadblock to delay Robinson’s four-year quest to obtain certification for the R66 light-single helicopter, says chief executive Kurt Robinson.

Cracked locking nuts found on several R66s have been traced to a manufacturing flaw that causes hydrogen embrittlement, Robinson says.

However, the issue is wider than just the Robinson fleet and has come in for new scrutiny from the US Federal Aviation Administration (FAA) and the European Aviation Safety Agency (EASA), Robinson says.

Though certificated by the FAA in 2010, the R66 remains barred from European sales while EASA continues to investigate the problem, Robinson says.

Robinson is unwilling to guess a timeframe for EASA’s final decision. "I’m optimistic, but I was optimistic a year ago,” Robinson says.

EASA, however, has overcome its objections to the R66 that delayed its European type certification.

The FAA granted the R66 a waiver from a requirement to have a back-up to the primary hydraulics system in case a chip or small particle jams a control valve. EASA initially did not accept the FAA’s determination that the R66 would be controllable even without hydraulic power assistance for the flight controls.

But EASA is now no longer concerned about the hydraulics issue for the type, Robinson says.