In case of bevel gear failure, the top part of the bevel gear continues transmitting the power to the main
rotor, but all the meshing loads are transferred to the upper bearing.
Following the investigations conducted on the 2 bevel gears, it was found that this bearing and the meshing
part of the bevel gear were in good condition after having operated during
almost 10 minutes after failure. Supported by the calculations performed, EUROCOPTER is therefore
confident that in similar cases, the 30 flying minutes permitted by the Flight Manual after activation of the
emergency lubrication can be performed without worsening of the scenario.
Nevertheless, EUROCOPTER will launch tests to demonstrate the latter. Pending the results of these tests,
a new procedure requiring immediate landing is defined for this specific case.
The whole SB is worth a good read. Bottom line at the moment EC thinks the shaft can last 30 mins in this condition, but untill they can prove it an immediate landing is require.