HALIFAX - A test to certify the model of helicopter involved in a fatal crash off Newfoundland showed it would remain airborne for "around 10 minutes" - about one third of the time required - if oil leaked from its gearbox, aviation regulators say.
Weeks after the crash of Cougar Flight 491 in March, European aviation authority documents revealed that the gearbox of the Sikorsky S-92A model hadn't passed a test that required it to run for 30 minutes without oil in order to meet a safety standard set by the U.S.-based Federal Aviation Administration.
According to additional documents obtained by The Canadian Press on the same Aug. 6, 2002, test, the gearbox fell about 20 minutes short of the goal when it was run at moderate speeds after oil was rapidly drained.
But Sikorsky says it has proven to aviation authorities that the chances of an oil leak from the gearbox housing is extremely unlikely and that the installation of a bypass valve resolves the only identifiable cause of a main gearbox oil leak.
The documents, obtained from the FAA through access-to-information legislation, outline a discussion between American and European aviation regulators on tests of the gearbox.
The European regulators said the test showed a loss of oil would mean the helicopter could only stay in the air for "around 10 minutes," a finding Sikorsky does not dispute.
FAA spokesman Les Dorr said the test, meant to simulate a "catastrophic loss of lubrication," was stopped at that point.
After the test, Sikorsky and the FAA agreed that the only clear risk for an oil loss would come from an oil cooler that fed into the gearbox.
A second test was then conducted on Nov. 16, 2002, to see if a bypass valve - which pilots would activate by pushing a button - would provide oil to the gearbox if the cooler were to fail. The system worked well and the gearbox kept going for hours.
Sikorsky spokesman Paul Jackson said the company demonstrated to the FAA and European regulators that the probability of a leak from the gearbox housing was "extremely remote" and that installation of the bypass valve "addressed the only identified, non-extremely remote possibility for a main gearbox oil leak.
"It is very important to note that while the Cougar accident was indeed a very tragic event, the worldwide S-92 fleet has about 185,000 operational hours without any other incidents involving this injury," Jackson said in an email.
But in the documents, the European regulators question whether the cooler would be the only likely source of oil leakage, and they asked for information on other possible failures on the main body of the gearbox itself.
Sheldon Peddle, a union leader representing the oil workers who still fly on the helicopters off Newfoundland, said the 30 minute dry-run test is an industry standard which allows pilots more time to react and the possibility of reaching either land or an oil platform.
Peddle said 10 minutes "may meet the legal definition of whatever the FAA has in the regulation," but his view is that it "doesn't meet the expectation people in the industry would have."
Per Gram, a recently retired pilot who tested the S-92A in Norway, said he believes the FAA shouldn't have allowed the certification after it learned of the results from the first test.
"I disagree fully with the FAA for allowing Sikorsky to pass that test on that basis," he said, referring to the second test of the bypass valve.
He said he believes the 30-minute standard should have been maintained for certification purposes of the Sikorsky S-92A.
"It (10 minutes) doesn't allow for human error ... as a passenger, I'd be scared stiff if I knew about this," said Gram.
But Jackson said 10 minutes is sufficient because the flight manual for the S-92A requires pilots to "land immediately."
"The S-92A is certified to fly at a maximum altitude of 15,000 feet. At a comfortable descent rate of 1,500 feet per minute, the aircraft could be on the ground in 10 minutes," he said.
Sikorsky documents used to market the aircraft, dated August 2003, said the gearboxes of the S-92A have a "30-minute drive system after oil leak."
Jackson said this claim was valid because Sikorsky's gearbox had passed the second test showing the bypass valve worked.
"That language is fully compliant with the ... requirement to prove 30 minutes of flight after detection of an oil leak," he said.
"We proved this by assessing the probability of a leak from the gearbox housing as extremely remote."
The Transportation Safety Board is still investigating the cause of the Cougar Flight 491 crash, which killed 17 people.
But the independent agency has said that studs had broken on an oil filter attached to the main gearbox, resulting in the loss of a large quantity of oil.