Fell 20 Minutes Short Of Gearbox Failure Requirement
During the certification process for the Sikorsky S-92A,
documents show that the aircraft failed a crucial test in which all
the oil is drained from the main gearbox to simulate a loss of oil
during flight. The test aircraft gearbox failed after about 10
minutes, which is 20 minutes short of the FAA standard.
A Sikorsky S-92A went down in March near Halifax, Nova Scotia,
and 17 people on board the aircraft were lost. Oil loss from the
gearbox is being considered as a factor in the accident.
Sikorsky and the FAA say the aircraft was certified after a
bypass valve was installed that would divert oil to the gearbox in
the event of a catastrophic leak, but that bypass is manually
activated by the pilot. A second aircraft was tested with the
bypass installed and activated, and the system performed
well. The gearbox did not fail after several hours of
The Canadian News Service reports that documents obtained
through a Freedom of Information Act request show that Sikorsky and
the FAA agreed that the single point of failure for an oil leak was
the oil intercooler that feeds the gearbox, and that the risk of a
system failure due to a gearbox housing leak was "extremely
unlikely. After the bypass test was successful, the S-92A was
certified by the FAA and EASA.
Sikorsky spokesman Paul Jackson said in an e-mail that the
company had demonstrated to both the FAA and EASA that the
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
Some people familiar with the helicopter, including retired
pilot Per Gram who conducted tests on the S-92 for Norway, said the
FAA should not have certified the aircraft after learning of 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.
The NTSB is still investigating the accident. It said that studs
had broken on an oil filter attached to the main gearbox, resulting
in the loss of a large quantity of oil. The engine ran for 10
minutes and 47 seconds after the oil loss.