I am part of a team developing a Cessna 172 P model for FlightGear, an open source free flight simulator. We are now trying to improve the oil pressure and temperature simulation, and we have a question concerning the behaviour of the oil pressure at startup. The oil pressure gauge in the model P ranges from 0 PSI until 115 PSI, with a green arc region between 50 PSI and 85-90 PSI. What we are trying to figure out is in which circunstances the needle should be in the green arc region.
I have checked many different checklists for the 172 and many state that the throttle should be at 1000 RPM for the oil check, so that the oil pressure should be at least 50 PSI. On the other hand, the 1982's POH does not state that the oil check should happen at a particular RPM; it only says that the throttle should be
OPEN 1/8 INCH on p. 4-7. But the POH is quite confusing concerning this issue, since it simply says
Oil Pressure -- CHECK but not that the oil should be on the green arc. To add more confusion to it, on p. 4-12 it says:
After starting, if the oil gauge does not begin to show pressure within 30 seconds in the summertime and about twice that long in very cold weather, stop the engine and investigate.
So nothing again about the green arc or 50 PSI, just about the gauge being alive. This is perhaps the reason those checklists include the 1000 RPM figure, perhaps the engine is not able to give 50 PSI or more of oil pressure when at idle (aprox. 750 RPM in the case of our model).
- in the Cessna 172P, at which RPM should the oil pressure be equal to or above 50 PSI?
- what is the procedure for oil pressure check, should it be done at 1000 RPM or at idle throttle?