"They do seem content to leave the S-92 without a full 30 minute capability which is a great concern but at least they are:
1) confirming that the S-92 has an MGB no better then aircraft a generation before it
2) that the marketing of the S-92's safety was hype
3) the 'social media' discussions by 'senior Sikorsky managers' (discussed in the TSB report) rubbishing other types were, at best, grossly misguided
One would at leat hope Sikorsky have the commercial sense to develop the S-92 to match the capability that their competitors have or that their competitors will be required to demonstrate in the products they are currently developing."
squibb66,
There are some changes that Sikorsky can make to the existing S-92 gearbox that might actually give it a 30 minute run-dry capability. Designing a gearbox to achieve a run-dry capability is ultimately an exercise in heat transfer. There are some new types of gear steels (C61/C64) that have been developed in the last 2 or 3 years, which have a very high tempering temperature (up to 900degF vs. 400degF for conventional gear steels). Having a gear steel that maintains its hardness/strength at high temps is a critical factor in achieving gearbox loss-of-lube operational capability.
The critical gears in the S-92 gearbox could have their material replaced with these newer C61/C64 alloys, without any other dimensional changes. So it would be a "drop-in" replacement. Of course the C61/C64 alloys are also much more expensive than conventional aircraft-grade gear steels, and require different processing. But the additional thermal margin provided by C61/C64 gear alloys might be enough to give the S-92 gearbox a full 30 minute run-dry capability. The only question being would Sikorsky management accept the cost involved?
Last edited by riff_raff; 1st Jul 2011 at 02:14.