Winter & Piston Engines

[iflyforpie]

I never use boost pumps on any of the TCM engines I fly for takeoff. Usually they run like crap even on the ground if you happen to forget to turn it off (or hit any of the very similar looking battery/generator,, landing/taxi, nav/strobe split switches installed on various Cessnas instead ).

Which kind of begs the question.... why do Lycs run fine with a boost pump going and no fuel return, while TCMs rich out with a fuel return?

[Big Pistons Forever]

The 421 is the same - fuel boost pumps off (center)
down (low) or high (up). I remember checking a
nice young fellow out on a 421 and I told him to
turn the electric boost pumps off on the ground,
set them to low for takeoff, and only use high
after an engine failure.

.

Depends on whether MEB 88-3 has been performed. If it has not then the POH says to put the switch on high. The pump will "supposedly" run on low unless a pressure drop is detected in which case the pump will automatically switch to high. Unbelievably after numerous engine failure caused by the pump switching itself to high even though the engine driven pump was still operating resulting in the engine failing due to grossly too much fuel, it still is not an AD.

Personally I won't fly any Cessna twin that has not had the MEB performed on the basis if the owner is too stupid to do this obviously vital mod, he probably has been neglecting other important maintenance items....

[Colonel Sanders]

The laundry list of accidents that have been
caused by their electric boost pump flooding
their TCM engine on takeoff (at WOT!) is
jaw-dropping.

READ THE POH

[pelmet]

I wonder who would even come close to priming for 30 seconds in the engines concerned. It took about 2 or 3 seconds to get 60 lbs/hour on the 337, maybe a few more. Maybe someone could prime, then be interrupted prior to turning over the engine and after a while prime again adding more fuel to the certain cylinder had not had the original prime drain out and then a hydraulic lock problem would be closer to happening.

In other words, I suspect that it is a very rare event but still one that is good to be aware of.

[GyvAir]

I wonder who would even come close to priming for 30 seconds in the engines concerned.

I've observed people being tutored to "prime until you see xxlbs on the indicator and it's running on the ground" as indication of adequate priming. There's always room for misinterpretation on such instructions. If the person doesn't have a sense of what normal priming is, or doesn't know/remember where they should be looking, the manifold drain valves are stuck shut/plugged... I can see how a green pilot might end up priming for 30 seconds or more. Clearly such a person shouldn't have been cut free on the type if they're that unfamiliar with the systems.. we all know that never happens.

[OntheNumbers]

Sorry to derail back to the original subject but this just came in this morning's Avweb newsletter:

http://www.avweb.com/news/features/What ... 257-1.html

Contains links to PDFs by Lycoming and Continental on the subject as well.

[pelmet]

"The Discovery Air Fire Services Cessna 337G, C-FBNX was in cruise flight near Dryden, ON, when the pilot noticed the rear engine (Lycoming I-0360-G) oil pressure begin to drop. The pilot shut down the engine, declared an emergency, and returned to Dryden where the aircraft landed safely. The drop in oil pressure was traced to the congealing of the oil in the oil cooler due to the cold ambient conditions."

I have seen a winter kit for the front engine but not the rear one. I wonder what the OAT was?

[GyvAir]

The CADORS update basically states that they were accidentally running a summer weight oil.
The OAT recorded at the airport at the time was -17 C

[Colonel Sanders]

1) C337 has TCM IO-360, not Lyc
2) pour point of 15w50 is -40C
3) pour point of W100 is -20C

[iflyforpie]

Youch! I've never really worried about the rear engine being too cold on the Skymaster. Usually it is the other way around. On both installations the oil cooler is fairly sheltered... unlike a lot of IO-520s.

[pelmet]

The CADORS update basically states that they were accidentally running a summer weight oil.
The OAT recorded at the airport at the time was -17 C

Interesting. So the OAT could have been much less at altitude. Good reminder of checking for proper oil prior to operation.

Continental engine is correct. TSB error.

[Colonel Sanders]

IFP has a good point that I'd forgotten - typically
the rear engine on the 336/337 runs hotter.

Must be something about the plumbing.

PS Running summer straight-grade oil in the
very cold winter will often cause oil to congeal
in the constant-speed prop hubs, too.