SASless
How do you determine you have an oil leak on the 92 while in flight? How do you determine the extent of the leak once you determine a leak exists?
I'm not sure if this is trick question(!), but the S-92 is fairly conventional in using an indirect indication based on oil pressure (indirect because you could theoretically lose the pump funtionality but without a loss of oil). In the case of a leak, oil pressure pretty proportional to oil quantity.
55psi is normal on S-92 with a caution light as ~35/45psi
Below 5 psi the Flight Manual calls for Land Immediately.
No that might seem straightfoward when flying an armchair, confusingly that is well down a rather wordy checklist, alongside text that
may have implied other physical symptoms would also have been present and without prior clear instruction to continue to monitor the relatively small gauge.
There is no warning given at the critical 5psi level.
The last press article also hints at a so-called Sikorsky Safety Advisory that came out after Broome but before St John's that implied the Flight Manual was to be changed to eliminate certain requirements to land immediately (in the case of smoke in cabin caused by another type of gearbox failure that has occurred). EASA (and then FAA) both issued safety alerts that the proposed change discussed in that Sikorsky document had not been approved and that proposal to slacken the Flight Manual has since been dropped.
An added challenge is that if one pump fails (as has happened several times on the S-92 so far promting rapid landings) the pressure can drop to 7psi (dependent on the build standard of the oil system). Remember that
2psi delta could be the difference between flying on to a landing site and ditching into an ocean. Now think about the last oil gauge you looked at, remember how small it was and wonder how well calibrated the gauge is...
IMHO Sikorsky have been very lucky to have not had prior ditchings to the various MGB dynamic system failures. BTW is you look in the new CAA CAP800 UK safety review, S-92 features 5 times in a list of recent high-severity events due to MGB foot cracks. These might be technically unrelated failures modes but they share an element in common: the same design team.