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Time Out
17th Sep 2003, 11:33
News Report from Canada.com

HALIFAX (CP) - The Canadian investigator of a military helicopter crash that killed two pilots is warning the international aviation authority to toughen inspections of the aircraft before another fatal accident occurs.

Maj. Jim Armour said in an interview Tuesday that he's asked the Federal Aviation Administration to tell operators of the Bell 412 to frequently check the rear rotor blades for tiny nicks, using bright lights and magnifying lens.

Otherwise, he said, "the possibility of having a failure of this nature still exists" on one of the thousands of military or civilian versions of the aircraft flying in locations around the world.

The Canadian Forces adopted the inspection practices recommended by Armour weeks after a Griffon, the military version of the Bell 412, crashed on July 18, 2002, in northern Labrador.

Members of the military's flight safety directorate identified an almost invisible nick in the aircraft's rear rotor blade - which stabilize the helicopters - as the cause.

The nick led to metal fatigue and the blade broke into three pieces during a routine search-and-rescue mission. The helicopter plunged to the wooded ground, causing the death of two pilots and injuring two crew members.

Since then, all of the blades of the 99 aircraft in the Canadian military's Griffon fleet have been sent for X-ray examinations and are given inspections every 12½-hours.

Armour said his draft report is circulating in the aviation community for comment and is "what I consider to be my final perspective on the accident."

The article is quite a bit longer. Here's the link to the full article.

Full article (http://www.canada.com/ottawa/story.asp?id=1D674CDF-552B-41C1-ABB6-4CECAD771F80)

Vfrpilotpb
19th Sep 2003, 03:24
If this Major has proved this "Nick" problem was the cause to this fatal incident, surely this would affect all tail rotors, of all helicopters, not just that particular model.
After all tail rotors mainly operate in a pretyy hostile area and most T/R that I have seen, looked like they had been prepared for repainting by contact with abrasive particles in the air.

Perhaps someone will explain more of the technical stuff regarding the abrasion and its possible outcome!!

Lu Zuckerman
19th Sep 2003, 04:04
To: Vfr

Aircraft manufacturers in general will establish the level of wear, abrasion and impact damage for propellers and rotor blades. They will also establish the extent of acceptable wear and or damage and the location of the damage or wear. They will also establish the corrective procedures to be used to remove or repair the damage or wear. They will also establish the blade removal criteria and whether the blades can be repaired at the factory or, if they should be scrapped.

It does not require a lot of time for a dent or nick to manifest itself into a crack and total failure. See my post on the CG HO3S blade fracture and the failure of the blade on the Marine HRS. Both on the Robinson blade thread.

:E