From Sikorsky:
If an impending failure is suspected, the primary consideration is to land the aircraft before the failure progresses to a gearbox seizure or loss of drive to the main or tail rotor,” the SSA continues. Sikorsky writes that a “single” indication of a MGB problem (pilots receive MGB temperature, pressure and chip detection system readings) dictates that the helicopter should land “as soon as practical”. Multiple indications, Sikorsky notes, “dictate that the helicopter should land as soon as possible,” while an impending transmission failure “would necessitate that the helicopter land immediately.”
Okay, so it puts it back on the pilots. Did they suspect an "impending failure" of the transmission? Obviously not. To us pilots, "land as soon as possible" does not necessarily mean "crash the helicopter if you have to." And even a notice to "land immediately" would be a tough call. If you were over unbroken forest with no clearings, would you put the helicopter down in the trees and intentionally crash? Or would you continue on, hoping for some little hole to stick the thing?
In the case of the Cougar pilots, without reading their minds it is quite obvious that they considered the ocean below them to be an unsuitable area to land...ergo, they assumed that doing so would be tantamount to crashing the helicopter. Why else would they have *not* chosen to land immediately? Instead, they chose the "land as soon as possible" option. And it was the wrong one. By the time they got the indications of impending failure, it was probably too late. (Was it when the tail rotor drive failed? Or did everything come apart at roughly the same time?)
Complicating things is the fact that we have no way of knowing if we've had a completely loss of transmission oil, as there is no gauge attesting to its level. All we have is the pressure and temperature gauges - and the temperature gauge may be unreliable if there is no oil to measure the temperature of.
So what could the Cougar pilots have been thinking - in those nine minutes - as they tried to figure out why they had no transmission pressure? Certainly that particular failure (the fractured filter mounting bolts) had not occurred yet, so it wasn't among the possibilities. If only they had some indication that all of the transmission juice was gone...
But... Again, would they still have landed? Would they have assumed that their transmission about about to fail?
This accident illustrates the uncomfortably tight squeezes between the rocks and those hard places we pilots sometimes find ourselves in.