outside air temperature
 

Dear Troels:

Thank you for your description of the flight. I was wondering if you read the outside air temperature at 11,000 feet during the cruise portion of the flight. The absolute minimum I would calculate would be -10C at Wabush minus 3C per 1000 ft = -43C assuming dry adiabatic lapse rate. Given the moisture at the departure, the actual ambient temperature could have been higher, perhaps between -28C and -43C at 11,000 ft altitude.

Did you see any variations in fuel flow before failure?

Regards,

Brian

Patricia Bell, of CBC News sent me a link to a story she did on this. It includes an audio of Troels speaking to Patricia.

Of note, there are comments by two different crews who spoke to them when they declared their Mayday.

http://www.cbc.ca/canada/north/story...-survivor.html

The comments are located here, and linked to in the above story

http://www.cbc.ca/news/yourbeststuff...ayday_rep.html

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.

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.

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.

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.

Is insulation enough?
 

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

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.

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??

What was the time lapse between engine failures???

The rear engine would generate enough heat to keep the rear breather from freezing

After inspecting the rear engine area with Larry, I retract the statement above. We think that the rear breather could freeze.

The forward engine failed first. This engine was factory new in 2000 and had been running 470 hrs since then. 5 minutes later the rear failed. The rear engine was Mattituck overhauled in 1996 and had a little more than 800 hrs running time since the overhaul.The rear has breather outlet just behind the prop. I saw no oil on the windshield.

I know that Continental is now working with The Canadian NTSB on the subject.

Troels.

I bought my 1966 Skymaster 2 year ago, and with all used machine there were some repair to be done. I notice that when the aircraft sat after flying, small pools of oil would appear under the front wheel well and also when dropping my gear doors, oil was in there also. I asked my A&P about it and his response was that the seals on Continental engines tended to leak and there wasn't much I could do about it except to keep adding oil. My engines have about 2200 hours each, so at the time I took him at his word. Besides, I had other repair to work on.

Last Christmas, I flew from Colorado to California to test the aircraft after my repair had been made. The trip out to California was uneventful as was the scenic flight for my friends around the San Francisco bay area. On the way back to Colorado, I landed in Nevada for refueling. Didn't notice anything out of the ordinary. It was already cold (about 25 degree F on the ground) when I took off again. Over the Utah/Colorado boarder I passed through a cold air mass I was expecting and my OAT drop from 20 deg F to below -15 deg F in about 20 minutes. It was so cold, my heater could keep me warm and I had to put on my winter coat, which was in reach (I couldn't reach the gloves which were way in the back). By the time I landed in Colorado Springs I found my rear spinner cone and broke off and there was oil all over my horizontal stabilizer.

Besides the spinner cone being a pain (I mention it somewhere in the messages), it turns out those seal used on my valve covers started leaking and my oil just passed out past the propeller and out the back. I lost 4 quarts of oil during that flight. If I continued the flight, I would have lost it all. After fixing the seals, I have had any pools of oil leaking anywhere.

I wonder if flying into very cold weather with degraded valve cover gaskets allows oil to leak out of the engine and it just flow along with the airflow out the bottom of the aircraft on the front engine and out past the propeller for the rear engine. There would be no visual confirmation. You won't see an oil pressure drop until your almost out of oil and you never see a temperature rise in the oil (because there is less of it to absorb heat) or Cylinder head temperature rise due to the extremely cold weather. When all the oil is gone, your engine seizes.

Just my opinion at this point. I've included a picture my friend took of my front nose wheel and you can see the oil around the chocks. It doesn't do this anymore.

Karl

I have had the Skymaster 10 yrs now and engine leaks have mostly been the gaskets under the valve covers. At some point they were discovered to be poorly installed and old so I had them all replaced. Leakage has been nearly zero. The new ones did require some retightening a couple of times, probably due for a check agin. Have had some minor leaks of the gaskets you describe but not a problem.

If the valve covers required safetywire to lock the nuts down, then we wouldn't have this discussion. I've used RTV on these gaskets and find that helps alot.