The fatal crash was caused by a nick the width of a human hair near the tail rotor and there have been six other incidents with similar aircraft.

"It is strongly felt that, barring the development of a simple, reliable and practical non-destructive test for this component, the practicality of continuing to safely operate the CH-146 fleet with this damage-intolerant (tail rotor) in field conditions in which the (Canadian Forces) normally operates is highly questionable," says the report, which makes 39 safety recommendations.  

Two pilots died on July 18, 2002, when the tail rotor came off a Griffon in mid-flight. The chopper was based at 5 Wing Goose Bay in Labrador.  

"We're saying we have information and data in the report that says you really need to look at the basic design of this component, the basic inspections associated with the component, and is it really meeting the goal of an air-worthy product?" Maj. Jim Armour, the lead investigator, said in an interview.  

Since the deaths of Capt. Colin Sonoski and Capt. Juli-Ann Mackenzie, the Canadian Forces has put in place stringent inspection procedures, including the use of optical micrometers and magnification to check tail rotors for minute cracks after every 12 hours a helicopter is in the air.

"We are safer today than we were before the accident," Armour said.  

However, in the field in Bosnia or Afghanistan "the practicality is certainly a question we have," he said. "We would like to see a more damage-tolerant component."  

A spokesman for Bell Helicopters was unaware of the report. No one else from the company was available for comment Monday.

It also goes beyond Canadian jurisdiction to urge the Federal Aviation Administration in the United States to look at the problem and reconsider the certification of the helicopter, noting there have been seven tail rotor failures on Bell 412 series aircraft.  

The Griffon helicopter was returning to the 444 Search and Rescue Squadron at Canadian Forces Base Goose Bay when the tail rotor came off. The helicopter spun out of control before crashing about 16 seconds after takeoff from a remote fuel cache north of Goose Bay.  

Both pilots were killed instantly. A search-rescue technician and flight engineer were seriously injured. The tiny defect near the rotor had been present for more than 76 hours of flight prior to the accident, but visual inspections recommended by the manufacturer failed to detect it.  

The report said the investigation also highlighted a major concern with the flow of information within the aviation community.  

While the Defence Department was aware of other tail rotor failures on two Bell 412 aircraft, the Canadian Forces investigation team was unaware of another four failures of this type of tail rotor for more than two years after the July 2002 crash, said the report.  

"While it is understood that not all nations and aviation organizations embrace free and open reporting, this poor flow of information is very disturbing," said the report.  

It also cites concerns with pilot training, noting that similar training problems were identified in the crash of a CH-12401 on the deck of HMCS Iroquois in February 2003, and recommends better training for military pilots on how to deal with such a malfunction.  

The Canadian Forces has 86 CH-146 Griffon helicopters in its fleet. They are used as support for the army and in search and rescue.  

The helicopters are based in Goose Bay, N.L., Gagetown, N.B., Bagotville, Que., St-Hubert, Que., Valcartier, Que., Petawawa, Ont., Borden, Ont., Edmonton and Cold Lake, Alta.  

                                    © The Canadian Press, 2005