On August 29, 2001, the FAA issued final AD 2001-17-17. The AD, intended to detect and correct cracks in Bell 47 main rotor blade grips, requires eddy current inspections at 300 hour intervals and places a service life of 1,200 hours on blade grips.
The AD affects more than 1,000 Bell 47 helicopters on the U.S. registry. Owners and operators of Bell 47s continue to voice serious concerns regarding repetitive inspection intervals, TIS limitations, and the availability of replacement parts.
AOPA agrees that, in this particular situation, the potential for in-flight separation of a main rotor blade and subsequent loss of control of the helicopter warrants airworthiness action. However, AOPA maintains that repeated main rotor disassemble/reassembly at 200-hour TIS intervals may substantially increase the probability of induced, undetected damage to the main rotor system. Further, AOPA maintains that there is little data to substantiate the FAA's current mandatory 1,200 hour TIS blade grip retirement life. Further, AOPA recommends that the FAA continue to issue AMOCs allowing repetitive inspections in lieu of retirement at 1,200 hours TIS.
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