Warbird Information Exchange

The abnormally cold conditions in the South this week brought up some cold weather operations questions.

The T-6G manual mentions priming 4-6 strokes and rapid priming to promote vaporization. Anyone have any proven techniques to pass on? Throttle use or setting, continuing to prime? Determining if it is flooded or not? Condensation on spark plugs? Seems like airplanes with a switch starter (instead of a foot switch) take one hand out of the loop when it would be nice to have two.

How about hot start?

Ken

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"Take care of the little things and the big things will take care of themselves."

Cold starts in cold temperatures require more fuel than normal. Primers are different from plane to plane as no two T-6s are alike. You just have to find a happy primer stroke count for your application. Throttle position should just be cracked as usual. Keep RPMs low (500) at start up to control high oil pressure due to thick oil.

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Live to fly, Fly to live.....

The amount of pumps of prime will be dependent on which primer you have installed, a large or small bore, your engine, and your starting technique. Someone says 4 shots and they have a large bore could be 8 shots with a small bore. If you have a G model 6, it will take a while for the oil to come up to temp as they do not have oil cooler shutters, if it is really cold, a oil tank heater might be a good idea.

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Matt Gunsch, A&P, IA, Warbird maint and restorations
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Very good information above..........but, I usually wait till April.

(It is no fun taxiing around on ice in these here parts. )

VL

Vlado, I keep telling you to bring the 6 out here, was only 80 today with clear skies.

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Matt Gunsch, A&P, IA, Warbird maint and restorations
Jack, You have Debauched my sloth !!!!!!
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Plus a pre heat of the engine or electric heating pads on the oil tank help the engine.
I have had good luck with around 8 pumps when cold. Parker primer as stock.
I don't pump the hand pump while starting nor do I prime while cranking.
I've pumped up pressure in the carb and pumped while priming. Then set throttle, with a switch to engage starter I crank and waIT 4 blades, turn on the mags to both and when it starts feed the mixture in. With a foot starter it's set the parking brake and follow the same procedure using your foot.
All I've dealt with are easy starting. If the prop is pulled back at shutdown you have to watch throttle position and be ready to pull it back if it bangs.
Good luck.

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Rich Palmer

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Thanks for the inputs!

Anyone have any techniques on leaving a loaded shot in the primer and adding during the start?

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"Take care of the little things and the big things will take care of themselves."

Why ? now you have a load of fuel in the primer that if the engine starts you have to do something with, it is easy enough to operate the primer if you need more.

51fixer, I have seen a number of 6s that unless the mixture is set to rich when using the wobble pump, they pour gas on the ground, I have always started with the mixture full rich as it is a float style carb, not much different than a cessna.

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Matt Gunsch, A&P, IA, Warbird maint and restorations
Jack, You have Debauched my sloth !!!!!!
We tried voting with the Ballot box, When do we start voting from the Ammo box, and am I allowed only one vote ?
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Something else to add to the above on real cold weather starts is to prime and then wait a few minutes for the cold fuel to vaporize and mix with the cold dense air better. Waiting will also allow the fuel vapors to flow back through the upper intake pipes back into the diffuser/blower and potentially allow the prime to be drawn in to the lower cylinders during starting.

As mentioned above I can't emphasize enough the importance of low RPM's just after start on real cold days. Especially when using straight weight oils as that thick oil pushed through the passages with higher than idle RPM will push its way out of the weak spots in your system namely the oil cooler, weak hoses and even your new oil filter.

Frankly on all radials you should start with absolute minimum RPM on every engine start to allow oil to flow and build pressure. Bring the RPM up only as necessary for smooth operation (below 1000) until oil temps are above 40 degrees centigrade.

I've seen problems with the Fram spin on filter cartridge on the Airwolf filter kits being internally damaged on very cold starts because of the cold oil hydraulic issue. The Fram filter has its own internal bypass but it seems this can be overwhelmed by thick oil and it will crush the element. As a general rule when you open your filter for particulate inspection the pleats of the filter should be straight and not wavy or certainly not kinked. If they are you have problems from either excessive contamination or possibly damage from cold weather starts.

If anyone wants photos of the damage I have been referring to I cand send or post them. Just let me know.

I hope I didn't take this thread in the wrong direction.

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I've seen and heard of quite a bit of these issues with Fram and other cheap filters in the automotive world too. The cartridges will collapse and the oil bypasses, the seams will split, or sometimes they'll even come apart and push the filter media through the engine. There were quite a few cases about ten years ago where Fram filters were coming apart on our Cummins trucks pushing filter media into the J jets that cool the pistons and causing piston damage. I expect sub zero 15w40 in a Cummins would be comparable to a cold aircraft engine.

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Complicating matters even further is that the brand on the outside of the filter may have very little to do with the actual manufacturer. Fram, or whoever, will contract filters to a price point, and may switch makers and features like bypass valves and internal pleats without changing part numbers.
On the automotive side of things this has been a known thing for a while, and it's worthwhile to sacrifice a filter every once in a while to make sure the filter you are using is still well made.
This shouldn't be too much of an issue since everyone in aviation cuts open their filters at every oil change to inspect them (right guys, every time?) and you can note changes in construction.

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I'd say this is a good discussion. Low RPM on any recip start should be good at any temp unless your particular engine demands otherwise. Since the experts say most wear occurs on start and while waiting those brief moments for oil pressure, every revolution you save is theoretically wear you save as well.

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"Take care of the little things and the big things will take care of themselves."

I know this one is old hat, but it bears repeating loud and often.
Sitting kills engines. The way to achieve the greatest longevity is to exercise the engine often. ie, GO FLY.
The only thing that will kill engines faster than sitting is periodic short runs. the classic, "I went out and started it up every month to keep the oil moving."
When the engine runs it produces water vapor. Unless the oil is thoroughly heated to operating temperature to drive the moisture out, the water vapor condenses, mixes with various acidic compounds also made by a running engine, and corrodes the guttyworks pretty badly.

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Lest Hero-worship raise it's head and cloud our vision, remember that World War II was fought and won by the same sort of twenty-something punks we wouldn't let our daughters date.

The people at Covington Engine said to run the engine for at least 30 minutes to help burn off the water in the oil and case walls...

My best results for the hot start: Mag switch on, throttle 1/2" or a little less, three full strokes with the Throttle, spin the starter and it lights right off. The book warns against using prime for a hot start, also against using the wobble pump during start. Also using the wobble pump with the mixture off dumps the fuel right on the ground..

Other Ken