I do not have the details, but the AD issued has effectively grounded much of the 47 fleet until operators can get the replacements, which are (as I understand it) both scarce and expensive.
There are some who believe the AD was yet another Knee-Jerk reaction.
EAA Thinks Emergency AD on Bell 47s Premature
EAA President and CEO Tom Poberezny has appealed directly to FAA Administrator Jane Garvey to rescind Emergency Airworthiness Directive (AD) 2000-18-51, which has effectively grounded more than 75 percent of registered Bell 47 helicopters in the United States since it was issued on August 31, 2000.
In his Nov. 22, 2000, letter to the Administrator, Poberezny criticized the FAA decision to issue the Emergency AD. "In the rush to produce the Emergency AD, proper public reviews and research was not undertaken by the FAA Rotorcraft Directorate," he said. As a result, some 970 out of 1,250 registered Bell 47s have been, EAA feels, unnecessarily grounded.
The Emergency AD was issued after two accidents that occurred outside the U.S. were attributed to cracked rotor grips. The Emergency AD mandates a 200-hour interval, repetitive Non-Destructive Inspection (NDI) of all Bell 47 main rotor grips, as well as the retirement of grips after 1,200 hours of service.
In one of the accidents, which occurred in Canada in 1998, a main rotor blade grips failed at about 100 feet and the Bell 47-G2 crashed. The Canadian Aviation Investigation Report (#A98O0214), which was released on June 22, 2000, found that the grip (which had 207 hours since new) failed at the threaded area.
Further, extensive pitting, determined to be a result of the manufacturing process, was found in the area of the thread roots and adjacent surfaces of the threads. As a result of its investigation, the Transportation Safety Board of Canada did not change the 300-hour inspection or the 2,500/5,000-hour retirement intervals.
Because AD 2000-18-51 is an Emergency AD, there was no NPRM, and the FAA never requested comments or blade grip-usage data from U.S. operators.
The Emergency AD cites a 70 percent failure rate of these grips, yet a search of Service Directory Reports in the U.S. shows no failures and only a few cracked grips. FAA’s AD author said the field service data was from Australia.
Based on industry and public concerns over the Bell 47 Emergency AD, EAA requests:
1) Emergency AD No. 2000-18-51 and the AD’s Final Rule (Docket # 2000-SW-35-AD) be rescinded until the FAA applies U.S. Bell 47 historical data to its decision process.
2) The Rotorcraft Directorate hold regional public meetings to address the Bell 47 blade grip concerns.
3) The comment period for the Bell 47 AD, Final Rule, be extended for 60 days, so that EAA can ensure that all Bell 47 owners/operators are informed of the final rule and that they have an adequate period to comment to it. EAA mailed the Final Rule to owner/operators on Nov. 27, 2000.
In the 50-year history of the Bell 47, there has never been a U.S. accident as a result of a cracked blade grip, according to information EAA and other owners/operators have gathered. What's more, there has never been a cracked grip found during the prior blade grip 2,500-hour (wood blades) or 5,000-hour (metal blades) retirement life and inspection process.
"EAA does not understand the need for an Emergency AD based on two accidents that occurred outside the country, given that the U.S, Bell 47 blade grip shelf life and inspection process has had a flawless history," said Poberezny. "EAA believes that the Rotorcraft Directorate has acted hastily and without obtaining necessary input from the operators of the aircraft."
EAA has taken the lead in attempting to bridge the information gap that exists regarding the issuance of Emergency AD 2000-18-51.
On Nov. 17, EAA mailed an in-depth survey to all 1,132 registered Bell 47 owner/operators to determine blade grip history on aircraft maintained per FAA regulations and procedures.
As of Nov. 29, EAA has received 40 completed surveys. The key answers were (1) The FAA never contacted them to determine U.S. blade grip usage history and (2) Not one owner/operator has ever heard of a cracked blade grip on Bell 47s maintained by FAA-certified mechanics.
Don't know the current status, sorry.
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Marc
[This message has been edited by RW-1 (edited 30 January 2001).]