There is no temp limit on its own in isolation that would require a land immediately. High MGB oil temp (above 130) will have clear cause and the temperature is a symptom of the main problem. This will be lack of pressure. High oil temp with pressure below 5 psi is a land immediately. This would be caused by a double pump failure. Single pump will not cause a large change in pressure, but is acceptable to be a low as 5 psi. Additionally the AC generators are cooled by MGB oil, so high temperatures theoretically could cause a loss of AC, so it is required to start the APU.
Complete loss of pressure cause by loss of oil would unlikely indicate a very high temp as it is measured by a wet bulb system, ie there must be oil in the gearbox for it to measure its temp.
Last edited by 26500lbs; 5th Oct 2013 at 14:46.