Graham Warwick/WASHINGTON DC
The US Federal Aviation Administration is revising an airworthiness directive (AD) that has effectively grounded the US fleet of Bell 47 helicopters.
After meeting with various groups, including the US Experimental Aircraft Association and Helicopter Association International, representing the operators of more than 1,000 Bell 47s still in service, the FAA plans to issue a revised AD in March. The revisions are unlikely to meet all the demands of operators.
The original AD, issued in August last year, requires main rotor blade grips to be inspected for cracks every 100h and retired after 1,200h. Because replacement grips are not available, this has essentially grounded the fleet.
Operators want the FAA to extend the inspection interval to 300h and restore the service life to 2,500h. The FAA has agreed to review data that might support extending the inspection interval, but has given no guarantee the revised AD will provide relief.
Meanwhile, due to the parts shortage for the 1950s vintage helicopter, the FAA says it will continue to allow grips to remain in service to 2,500h with additional recurring inspections. But once parts supply meets demand, grip life will be reduced to 1,200h, the agency says.
Bell has agreed to produce a limited number of grips to the original design as an interim measure while it qualifies an improved design. Original design parts will become available in March and new design grips late in the third quarter.
Source: Flight International
