Sid447, the Fuel Cooled Oil Cooler is just that, an oil cooler. There is a separate Fuel Heater for heating the fuel. It just happens to use engine oil for heating the fuel
Oil is also cooled by intake air, as the oil tank in the Accessory section has fins that intake air passes over, helping to cool the oil.
Temp limits are not to do with the oil, they are a function of the temp limits of internal components in the engine or gearbox. The oil will not begin to break down until it gets much hotter than the MGB temp limits, but the components are always much hotter than the oil (the oil only carries some of the heat away).
There have been coking issues with some engines, particularly running 2380 oil in high temp locations. The Turbine Scavenge Pump especially was heat soaking after shutdown causing the oil to coke up.
Originally Posted by
Sid447
What is the nominal operating tempurature...
For the AW139 main transmission?
The system has an 82c thermostat, so in a sufficiently well-designed system, shouldn't this temp be maintained in normal S&L flight conditions?
The same oil is used in both the engines and the transmission, yet the engines are ''red-lined'' @ 140c and the transmission @ 110c...
.....Reasons?
Someone mentioned the engines having a fuel-cooled oil cooler....this is more of a heat exchanger with the primary purpose of heating the fuel, it does little, or nothing to cool the engine oil. The engine oil temps (in hot climates) run at around 115 to 125c ....and during the two minute cool down after flight can often reach 140c!