Bell 47 operators are awaiting the US Federal Aviation Administration's response to a two-day summit held at the end of January on an airworthiness directive (AD) which has grounded the 1,000 aircraft on the US register.
August's emergency AD requires operators to inspect the main rotor blade grips for fatigue cracks every 200h and to retire them after 1,200h. The AD was prompted by the failure of a blade grip on a Bell 47G. Analysis revealed cracks in 70% of grips inspected. US-registered Bell 47s are used mainly for agriculture and recreation.
Components for the 1950s-vintage helicopter are no longer in production, forcing operators to ground aircraft. Rather than put the original grip back in production, Bell is working on an improved design, but says this will not be available for a year because of the lead time on castings.
Bell 47 operators, the Experimental Aircraft Association and Helicopter Association International are pressing the FAA for relief from the AD, pointing out that Australian and Canadian inspection and retirement intervals are around twice as long as the FAA's.
Source: Flight International
