I believe this is the up to date Emergency Procedure that would have been reviewed by the Crew and the Cougar Ops folks during the conversation they held by radio during the descent to 800 feet.
I have added the bold print and underlining.
Do you 92 drivers out there concur in this is the procedure you have been taught and are expected to conform to by your operator?
MAIN GEARBOX OIL SYSTEM FAILURE
Symptom:
MGB OIL PRES or MGB OIL HOT or MGB CHIP or ACC 1 CHIP or ACC 2 CHIP or MGB OIL PRES
GEARBOX OIL PRESSURE aural alert.
Confirming:
NOTE
The confirming steps only apply to low oil pressure or high oil
temperature.
There are no confirming steps for chip indications.
Symptom:
Main gearbox oil pressure is less than 35 psi
or
Main gearbox oil temperature is greater than 130 degrees.
WARNING
BYP must be selected within 5 seconds after the MGB OIL
PRES warning has illuminated to ensure an adequate
quantity of oil remains in the gearbox.
DO NOT activate BYP
if the warning is not illuminated.
CAUTION
When the MGB BYP mode is activated by the crew, the MGB
oil temperature will increase. The temperature is expected to
increase into the red operational range, this indication
should not be considered a secondary indication for
determination of landing immediately.
CAUTION
The main AC generators are cooled by main gearbox oil. Loss
of cooling oil may result in mechanical failure of the generators
and loss of main electrical power.
NOTE
The MGB BYPASS caution will illuminate when BYP is selected. As
the MGB oil pressure stabilizes, the switch should be left in the BYP
position. The MGB BYPASS caution and MGB OIL PRES warning
will remain on until the rotor is shut down after landing.
NOTE
After MGB bypass switch is activated, MGB oil pressure should
stabilize or fluctuate in the range of 5 to 25 psi. Gearbox temperature
will slowly increase into the red zone.
NOTE
Either a massive main gearbox oil leak or the failure of a main gearbox
oil pump may cause the MGB OIL PRES warning light to illuminate.
NOTE
If the MGB OIL PRES warning illuminates, the MGB OIL PRES
caution will not be illuminated.
Action:
1. MGB OIL BYP - Select BYP only if the red MGB OIL PRES warning illuminates.
2. Descend to minimum safe altitude.
3. APU CTRL — ON.
4. APU GEN — ON.
5. Land as soon as possible.
If the MGB OIL PRES warning or the MGB OIL PRES caution and any of the following secondary indications of gearbox
failure are observed:
MGB oil pressure below 5 psi
Smoke or fumes in the cabin
Any subsequent hydraulic system failure
Progressively increasing power required to maintain flight
Unusual vibrations or noises.
6. Land immediately.