18th Oct 2011, 15:36
A question for a proper spanner god, does the CFM56 oil system (specifically -2 model, but I doubt they differ greatly) use supply oil for the pressure gauge pick-off, or supply v sump px? I suspect the latter, from checking pipework, yet find no reference in my tech pubs ( a reference would be appreciated, Google has not really helped so far...). What is the advantage or benefit of using supply v sump as the indication? - I believe the 211 uses the latter as well?
Thanks for any help!
18th Oct 2011, 17:05
a) The latter
b) It gives the actual pressure in the system, that is the difference between the pump out put and what it is working against in the sumps/gearbox.
18th Oct 2011, 17:08
Thankyou spanners, much appreciated.
18th Oct 2011, 17:15
The CFM-56-2-C in the DC-8 70 series receives its oil pressure indication from between the oil pump output (after the filter) and to the bearings, upstream of the oil flow to the accessory case.
The LOW OIL PRESS lite also indicates bypass of the filter downstream of the scavenge pumps.
Disclaimer: I'm just a pilot, but with the oil system schematic right next to me. :ok:
18th Oct 2011, 18:03
Desert, thanks. My schematic is similar, but I suspect is just that, a schematic. Having looked around a part dressed engine this afternoon, it had extra pipework connected to the sump system, hence the search for further explanation. Thanks again.
18th Oct 2011, 23:35
This is CFM-3 system for Airbus:-
Oil pressure is always measured before the bearings where it is needed.. So, the oil press transmitter for ECAM and Low oil press s/w and oil filter clog s/w are after the main press supply pump and main oil filter before splashing into Fwd & Aft bearing sumps, AGB TGB.
Oil temp sensor for ECAM is the cooled oil after coming out from the oil tank before going to the supply pump. However, there is another oil temp sensor for ECU.