There has been a cautious welcome for the US Federal Aviation Administration's proposal to modify an airworthiness directive (AD) requiring inspection of Bell 47 rotor blade grips for cracks.
The emergency AD, which was issued in August last year, has effectively grounded the US fleet of over 1,000 Bell 47s because of a critical shortage of replacement grips.
In response to protests, the FAA has issued a notice of proposed rulemaking (NPRM) for a revised AD, which would increase the inspection interval from 100h to 300h, but require operators to use eddy current, rather than dye penetrant, inspection techniques because it is better able to detect small cracks.
"Overall, this NPRM is a vast improvement over the previous Bell 47 blade grip ADs," says the Experimental Aircraft Association. Concerned that the NPRM does not address the "critical shortage" of spares, the organisation is pressing the FAA to extend the grip retirement life from 1,200h to 2,500h using the 300h eddy current inspections.
Source: Flight International
