Can anyone tell me the procedure for loss of XMSN oil in the S-92.In particular, is there a requirement to idle back on an engine?
Loss of MGB PRESSURE is your subject here, and there are a number of indications and causes, so maybe not quite as simple as loss of XMSN oil, but once the MGB pressure drops below 35psi the red warning light appears and you get an audio warning. One is to then manually operate the MGB OIL BYPASS switch within 5 secs. This then bypasses the oil from the cooling system, which consists of teflon hoses and a radiator, routing it directly back into the MGB. This system is the "known" weakness and is stated as "vulnerable to leaks" in the OM! The procedure is therefore to "hope" this is where the leak was, bypass it and descend to MSA and hope you get no further indications. Get some further indications and you can assume maybe guess 1 was incorrect so you get another go, but dont take too long about it. These would include a further drop in MGBP, a HYDS failure - as there is a hydraulic module drive gear taken off the input drive shaft - therefore indicating impending drive shaft fail, maybe an AC failure, or any loud and unusual noises or a combo of ACC and/or INPUT CHIPS. If guess one was wrong, then we can give guess 2 a go and maybe see if there is anything indicating with the ACC modules or INPUT modules. An INPUT CHIP at this stage will certainly result in bringing an engine back, but only if it is suspected that the failure is here. By this time I suspect most of us are looking to get down and hopefully onto the solid ground PDQ but a ditching is also on the cards if nothing solid is available. If all this is getting a bit confusing we can also consider the possibility that there is a problem in one of the dual vane pumps. These use one element for pressure feed and one for scavenge feed. It has been suggested that if one element fails, in particular the scavenge, then the oil can be sucked out by the pressure feed! Now i am lost. Unfortunately this also cools the AC gens, so things are going from bad to worse once more. Again, looking for somewhere to land.
All in all the situation is not very good, and there is a good deal of room for confusion. There are one or two on this forum who have some much better first hand experience of this, so can maybe explain it better.