Warm Up Times of Radial Engines.

[Viper2000]

Originally Posted by ElAurens

Was that a cold start as in the first start of the day?

And what was the weather like?

A "cold" start in the summer near Atlanta is a very different animal from a (genuinely) cold (and probably wet) start during a British summer, let alone (for example) a Russian winter...

[drewpee]

I don' know about aircraft engines but air cooled motorcycle engines warm up quicker than liquid cooled. Air cooled only have the sleeves and cooling fins to heat. With liquid cooled you have twice the amount of metal in the block and heads. Then there's the coolant and radiator reservoir. Ride a liquid cooled bike hard to soon and you get unnecessary wear and stress.

[BP_Tailspin]

Originally Posted by zipper

Here's a P-47 cold start with two mins to taxi.

Two minutes before he Taxied but how long before he was ready for Takeoff ?

At 4:24 he taxied behind the C47 blocking the camera mans view, and one second later at 4:25 the P47 was taking takeoff. The camera man had to plenty of time to reposition for a better view of the takeoff because the P47 was at the far end of the runway (out of sight) warming up for 20 to 30 minutes before the camera man filmed the take off.

lol - ok, guys. NOTE: I was there BUT did not shoot this video.

It was the end of May in Atlanta. Was comfortably warm, not hot by any stretch, and slightly humid. It was the first start of the day for the Jug. The video is clipped but it was not a twenty or more minute delay to takeoff, more like fifteen. The taxi was nearly half of that with run-up the majority of the other half. Even with the paddle blades there isn't an awful lot of airflow from the prop on the ground so the danger is almost always (unless in the snow, of course - lol) overheating before takeoff. Heavy bombers at large bases lining up for massive raids would sometimes adopt the technique of taxiing on inboards, then switching to outboards and then back again to control temps (and that's with paddles). The bat handles on the early F4U, as a contrast, required rather quick, deliberate action on the ground in the Pacific, as you might imagine.


... AND ... once you're good for 1000+ rpm (40C) you're good to go, temp wise. What might hold you back a little is if you are paying for it (you just can't baby your $75000 motor too much, eh?). The taxpayer was swapping out the engine in a couple hundred hours (at least, hopefully) during the war so they did what they did back then (i.e. use 70" for takeoff). Ground crew run-ups prior to missions were as much or more a systems check as engine warm-up.

[Crumpp]

The purpose for warming an engine is to get the oil warm so that the bearing surfaces are lubricated properly.

True but even more important is the fact aircraft engines have what is called a "choke grind" cylinder.

That means the cylinder is wider at the base and narrower at the head when cold. When warmed up, the head is hotter than the base so it expands and the cylinder walls become straight.

If you operate your engine without it being warm, then you are really putting excessive wear on the head, pistons, and rings.

Originally Posted by Crumpp

True but even more important is the fact aircraft engines have what is called a "choke grind" cylinder.

That means the cylinder is wider at the base and narrower at the head when cold. When warmed up, the head is hotter than the base so it expands and the cylinder walls become straight.

If you operate your engine without it being warm, then you are really putting excessive wear on the head, pistons, and rings.

Yes. That's a good point, but what I'm saying is that on the engines I've run by the time the oil is warmed up enough to rev up the engine the cylinder head temps are good to go. That's all.

[TomcatViP]

Basically the cylinders need to absorb the heat first before the engine start heating the oil.

Hence when the oil temp is good, the cylinders are already fit to go