Skymaster Arctic Circle Ditching.

[Diamond Service]

The indicated OAT at 11000 feet was -31 C. I did not see anu variation in fuel flow. The engine never misfired or vibrated up until the point of failure.

Troels.

[Diamond Service]

The way I see it we must have lost the engine oil. The decreasing oil temperature followed by loss of oil pressure means no more oil to me. I know that the breather lines from the outlet to the rear baffle was not insulated. I still have pictures showing that. Maybe the breather line was blocked due to the low outside temperature and the oil pumped out somewhere because of that. I was not aware that it is a good idea to insulate the breather line. I have previously owned two Aztecs and the breather line on a Lycoming are behind the baffle on the rear part of the engine. This is pure speculation but maybe some of you have some experience on the subject.

Troels.

[WebMaster]

Advisory Circular AC 91-13C covers cold weather operation of aircraft.

Section 4, d. says the Oil Breather requires special consideration. Frozen breather lines can create numerous problems.

My Skymaster had baffles that attached inside the front engine cowling, to reduce the amount of air flowing over the engine, during cold weather operations. Unfortunately, I don't have access to the POH anymore, but I seem to think these were for operations below 20 degrees F.

The whole AC is interesting reading for those who operate in cold weather.

[skymstr02]

I've seen an aircraft that the breather line froze over, the crankcase pressure built up, and blew the crankshaft seal out, then the mess began.

[billsheila]

So is all that is required to have some insulation over the line to prevent this problem?

[Skymaster337B]

The oil breather line should have a knoch cut into it about an inch or two above the end to counter a frozen line. If the engines were recently overhauled perhaps the shop replaced that line but didn't read the maintenance manual about ensuring that knock was there. That knoch is why most Skymaster belly's are dirty. It's a necessary evil.

[WebMaster]

What about the rear engine??
My memory is that the rear vapor line goes up and out the rear of the cowling, adjacent to the prop. Would that line also get frozen up??