The US Federal Aviation Administration has proposed to mandate a series of actions already recommended by Sikorsky aimed at preventing a main gearbox oil pump failure on the airframer’s S-92 helicopter.
The proposals include automating a process to switch a bypass valve if oil pressure drops below 2.4bar (35psi), and installing a sensor that would detect an oil pressure drop and alert the pilot, the notice of proposed rulemaking issued on 23 July says.
The FAA would also require software changes to give the pilot visual and aural warnings of an oil pump failure in the S-92's main gearbox.
Publishing the draft rule in the Federal Register is the first step in the FAA’s rulemaking process. The public now has a chance to comment on the rule until 22 September.
Sikorsky has already advised S-92 operators to make the same hardware and software changes in a series of service bulletins issued by the company from 2011 to 2013.
The bulletins and rulemaking process were launched following the 2009 crash of an S-92 off Newfoundland, Canada in which 17 people died, due to a loss of oil in the main gearbox.
The FAA document also discloses another incident of a leaking oil pump.
The S-92’s manual requires the pilot to manually switch the bypass valve within 5s of an oil pump failure alert. In this case it took the pilot significantly longer to make the manual switch, the FAA says.
The incident persuaded the FAA that the manual process was impractical, which led to the recommendation to automate the switch.