Skymaster Arctic Circle Ditching.

[Dale Campbell]

I to installed M-20 air/oil seperators on my 337H 6 years ago. This was due to a oil slick found on the belly and tail area. I also insulated the breather line from engine to M-20 including M-20 down the exit pipe on both engines. My rear engine always ran much hotter than the front engine, which is normal for 337. In summer I fly with cowl flap door partially open when tempature above 85 degree. In winter rear runs about 180-200 degree. The front engine runs 180-200 in summer but ran 160-170 in winter. I now install a plate above front engine oil cooler for winter to get the engine above 180 degree. Without the plate I was holding water in oil and could see droplets on dip stick. No problem now with plate installed. My bird is normally asperated so anything above 13,000 feet is out of the question and I live and fly in Pennsylvania and mostly fly 500 mile radius of Pa, so I do not experiance any super cold air.

[sunnysky]

BILLSHEILA is on the right lines I think.
Several years ago I was flying my 337G from France to the UK. It was a much much colder than ISA day. Seem to remember something like minus 20c at 12000feet. We had been in the cruise for over two hours when I noticed the rear engine oil temp gauge "going off the clock". The problem was confirmed by low oil pressure. I reduced power on the rear and started a descent. The intention was to divert to Cardiff in Wales. At about 7000feet the oil temp started to reduce together with an increase in pressure. Power was gradually increased and the engine ran normally and the flight continued to Leeds Bradford.
I reported the problem to the Chief Engineer at Knight Air ( who were very "au fait" with the 337 ) and we concluded that there is a thermo valve in the oil cooler which stops oil going thro' the cooler when cold. In this instance because ambient was minus 20 or so, the cooler had shut off, then causing the oil to overheat then the low pressue. If there is then congealed cold oil in the cooler, the valve will not open to let the hot oil through. Then overheating. The only reason oil started to flow thro' the cooler again was due the the rise in ambient temperature.
Hope all this makes sense.!! It's my input for what its worth !!
Sunnysky

[Ernie Martin]

The report, however, is that they had a decrease (not increase) in oil temperature, which differs from your experience. Might be the same issue if oil temp was measured at the cooler in their aircraft and in the engine in yours.

Ernie

[sunnysky]

Hmm. Must say I didn't understand the bit about decreasing oil temperature in their report. Usually when you have decreasing OIL PRESSURE (as they state) you have a high oil temp ?
Maybe some clarifacation on the oil temp situation would help.
Your point Ernie on on where the oil temp is sensed. Surely its the same in all 337s ? Apart from the turbo ones maybe ?

[Ernie Martin]

I assumed the same, that all 337s measure oil temp at the same location, BUT a different measuring point seems the only way that your experience and theirs has the same cause. Also, is it possible that electronic engine monitors put the probe at a different point than the stock gauges?

Ernie

[Skymaster337B]

I'm starting to like the oil cooler theory. My question is, what type of oil was used? Straight weight or multi-viscosity synthetic oil? Personally, I only use synthetic oil and it makes a big difference how fast the oil pressure rises on a very cold day.

I also find it rather odd that the operator and maintenance manuals don’t establish a cold weather limitation…they both generally discuss colder weather starting procedures. There is an option for an oil dilution system, but that is for starting during cold weather and not while operating at altitude. The operator's manual says to watch engine temps during a cold weather descent…i.e, don’t chop the throttle. But the big paradox is I remember seeing optional cold weather plates the restrict airflow thru the front cowl and also out the rear cowl…but can’t find any info about it in either the operator or maintenance manual. It makes me wonder if Cessna really didn’t even want to mention cold weather flying for some reason.

[sunnysky]

Yes. I;ve heard about "winterisation" kits, but can't find out much about them.
Sunnysky