EIU_EEC
Yes I am sure for the reasons I explained! The PTU is designed to run for hours in a row, this is not a problem as long as there is hydraulic fluid in both the yellow and the green system.
If it would always overheat hydraulic systems after 2 minutes it would hardly be a backup for losing one of the engine driven hydraulic pumps now would it?
Overheat can only happen if one of the hydraulic reservoirs is depleted. This means that one system could drive the PTU into overspeed as the PTU is not driving anything.
But this has been modified through a service-bulletin. The PTU will be inhibited for low reservoir levels. So the simple fact is that it won't run if there is a danger of overheating the other system.
Some info for you:
http://ad.easa.europa.eu/blob/SIB_20...IB_2012-16R1_1
The overheat incident:
http://www.aaib.gov.uk/cms_resources...EZDM_08-09.pdf
Airmann:
We are talking the main hydraulic sources here Green and Yellow im relation to the PTU, the PTU cannot power the blue system. Nor can the blue system power the green or yellow system. Lets Keep it simple ok?
Yes the blue system has an electric pump, but that is hardly relevant, it can also be pressurized by the RAT in case of electric pump failure.