The US National Transportation Safety Board (NTSB) is recommending that the US Federal Aviation Administration undertakes a fatigue evaluation/damage tolerance analysis of the Eurocopter BK117 helicopter's vertical fin structure, to ensure that the inspection requirements of an airworthiness directive (AD) are adequate to detect cracks.

Last year, the FAA grounded BK117s and BO105s so that tension-torsion straps contained in the main rotor head could be inspected and replaced as required. The AD followed the crash of a BK117, operated by a hospital, on 17 July, 1999. A main rotor blade separated, killing three crew.

Source: Flight International