The helicopter crash off Nova Scotia that killed three Canadian Forces airmen on July 13 cannot be blamed on a faulty tail rotor, investigators say.

Canada's fleet of Cormorants has had problems with cracked tail rotors, but Lt.-Col. Colin Goodman said Wednesday there's no evidence that's what caused this crash.

The damaged Cormorant was brought to the Shearwater military base after the crash.
(Preston Mulligan/CBC)

"When you saw the tail rotor blades still on the tail rotor assembly, that was a firm indication that the tail rotor assembly did not disintegrate to cause the accident," he told CBC News.

There was damage to the assembly, Goodman added, but that likely happened when the chopper crashed into the ocean.

The accident happened while the CH-149 Cormorant search-and-rescue helicopter was on a routine training exercise near Canso.

Local fisherman were on a boat waiting for someone to be lowered from the chopper when they heard a loud bang, then voices yelling for help.

Blinded by the thick fog, the crew of the Four Sisters followed the cries and pulled two airmen out of the water and two others from the partially submerged helicopter.

Divers found the three other crew members dead inside the Cormorant.

'Modest, everyday heroes'

At a memorial service Tuesday, Sgt. Duane Brazil, 39, of Gander, N.L., Master Cpl. Kirk Noel, 33, of St. Anthony, N.L.,  and Cpl. Trevor McDavid, 31, of Sudbury, Ont., were remembered as "modest, everyday heroes."

Goodman said he's confident investigators will be able to determine what caused the crash because of the large amount of evidence available to them.

The Cormorant's flight data recorder and cockpit voice recorder have been sent to Ottawa for analysis, and the crew members have been interviewed.

In many cases, Goodman said, aviation disasters are the result of several things going wrong at once.

"It's a common saying in flight safety that it's a Swiss cheese, and when the holes in the Swiss cheese slices line up, that's when you have an accident," he said.

"It could be on the maintenance side ... it could be on the human error side, sometimes it's a lack of practice or someone has passed on an inappropriate way of doing something."

Questions were raised about the tail rotor shortly after the crash, because of the fleet's history of problems.

Both the Canadian chopper and its British counterpart, the Merlin, have had trouble with the tail rotors.

In October 2004, cracks were spotted inside the tail rotor of a Cormorant, forcing the entire Canadian fleet to operate under severe flight restrictions.