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Oil thermostat - why not universal?

Oil coolers can suffer from the oil becoming like treacle under very cold conditions and blocking the oil system the solution to this is to cover the cooler so it gets restricted cooling air and the oil stays at a viable temperature.

The C152 is badly over cooled for European operation, I have seen the oil temp struggle to get into the green arc during night flying on the winter with an OAT at -15c. Not only does the oil cooler need a plate the cylinder cooling needs winterisation plates.

and blocking the oil system

If there was a thermostatic bypass valve, would this not bypass a viscous-oil-blocked oil cooler?

Shoreham EGKA, United Kingdom

The thermostat valve never entirely by-passes the oil cooler so the oil cooler never gets blocked by thick oil.

In the days of big piston engine airliners the problem was that in very cold conditions the oil cooler would block and the oil bypass the cooler, this would result in the engine overheating because no oil was being cooled. The solution was to never entirely stop the flow to the cooler to ensure the oil never turned to treacle.

They did fit oil cooler flaps to regulate the oil temperature by controlling the airflow entering the cooler, it was one of the flight engineers duties to regulate the oil temperature along with any number of aircraft systems that now would be automatic.

Retuning to the modern ? Piston engine, during winter operation we need to have some control over the airflow through the oil cooler, the C152 being a prime example of an aircraft no doubt developed for hot days in Wichita and vastly over cooled for a cold day in Europe. Take a look at a C152 from the front and then a Robin DR400 with the same engine, you will notice the much bigger cooling intakes.

Robin engines almost never exhibit the corrosion related piston plug shaving that is common on C152’s as the oil temperature during the winter is held at the optimal for water evaporation. There is of course a downside on a +35c day a fully loaded Robin is likely to need to step climb if you are going much above 6000ft to keep the oil temperature within limits.

Hi….It might have been a 160 degree indoor regulator, I checked with a thermometer and it was working at around 140. I was there when the old indoor regulator caused the new high temp alert to go off. Be that as it may, thinking back its conceivable the repairman didn’t introduce sufficient coolant after the work was finished. Regardless it has another indoor regulator.

United States
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