At another forum, a member (who is usually well-read) pointed out to a possible weakness of the radial engines installed in interceptors that opearted under short notice, namely that it took ~15 min to warm them up before taking off (as noted at 'Shattered sword' per that poster), vs. ~5 min for the liquid cooled engines. Anyone has some firm data on this topic?
Aircraft engines warm-up times?
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SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
I would think it would be the other way around. I would like to hear from someone who knows too.
cvairwerks
Senior Airman
Warm up time depends greatly on the engine installation and ambient temps for the operating location.
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Same airfield, same (summer) day, interceptors (fighters) in service under short notice.
Maybe it has to do with the fact that liquid cooled engines have a thermostat that opens only after the cooling fluid has reached a certain temp, while in air cooled the cooling is continuous and can be influenced only by a certain extent with the cowling flaps.
For sure, temp fluctuates more in air cooled engines than in a liquid cooled with thermostat valve, with all that follows.
For sure, temp fluctuates more in air cooled engines than in a liquid cooled with thermostat valve, with all that follows.
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cvairwerks
Senior Airman
When I said location, I was meaning actual physical location. Warm up time at a location in North Africa is going to be way different than the Aleutians. Some locations, there isn't going to be any appreciable differences, while others, there might be. I know the radials I've flown, all want oil temps above a certain number before any major power excursions, no matter the installation. You could use cowl flaps to help oil temps warm up quicker in the winter, but the difference in warm up times for us was not that great. When I worked on Mustangs, we just looked for a rise over ambient on coolant temps before applying anything more than the power required to taxi. I never was the PIC on a Mustang, but we were within coolant temp limits after even our shortest taxi, which was about 1/2 mile at most. Firing up the L-10A, we had oil temps in the green within about 3-4 minutes in the summer on some pretty tired R-985's, long before we were ready to taxi.
Deleted member 68059
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I think its not sensible to make blanket statements, as there are too may variables with the installation and so on. However, for the Fw190, this was the conclusions in that particular respect by British Technical Intelligence.
Snautzer01
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What year was that that tid bit from? And for what air frame? Captured? Just curious not challaging ofcourse.
GregP
Major
From some old reading on airfield strategy, I saw a description once where the crew chiefs started and warmed up the aircraft very early in the morning (a couple of hours before takeoff, anyway), and kept them warm by running them every 20 minutes until time for regular takeoff. This was for a Bf 109 airfield. I do not know that I heard the same for Fw 190 airfields, but when the Chino museums fly a radial aircraft, they generally have to start up and then taxi for over a mile before takeoff, and then usually wait for traffic. I doubt they waited for traffic in WWII, and they didn't have to taxi far, so the warmup time would be just running where you started it.
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Deleted member 68059
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1942
Snautzer01
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Armins bird i guess. Figures. I do think you read the Bf 109 test by the same people.
When my father instructed in T-6's, he said that the ground crew warmed up the aircraft and checked that there were no squawks before the students arrived. If you wanted interceptors on alert, it stands to reason that you wouldn't want the pilot to jump in the cockpit and discover that he had a maintenance issue so I imagine that their aircraft had been checked out.
Deleted member 68059
Staff Sergeant
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Correct, Fw190 A-3
Snautzer01
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That explains it. Did you read the bf 109 report by the same?
Deleted member 68059
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I have AFDU reports on the 109F and 109G, together with translated French reports of the 109E, which specific one do you refer to ?
33k in the air
Staff Sergeant
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For what it's worth, the Standard Aircraft Characteristics publications, in the calculation of combat radius, allow 10 minutes for engine start, warm-up, and take-off.
The Aircraft Characteristics and Performance publications, in the calculation of combat radius for Navy fighters, allow 20 minutes for engine start and warm-up, and 1 minute for take-off.
The Aircraft Characteristics and Performance publications, in the calculation of combat radius for Navy fighters, allow 20 minutes for engine start and warm-up, and 1 minute for take-off.
Zippythehog
Senior Airman
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- Jan 7, 2017
When I flew freight in a Chieftain during the winter, we warmed the engines within 30 minutes of departure. I would imagine that interceptors would receive similar treatment.
YakMan
Airman
The critical thing with warm up is achieving oil temperature rather than cylinder head temperatures. I work with radials and have no experience with liquid cooled aero engines but I would hazard it is oil temperature you need with them over coolant temperature.
With our radials the cylinders heat up pretty quickly whereas even in summer, the SAE50 mineral oil can take 15 to 20 mins of high idle running to achieve takeoff temperature of 60degC with a do not exceed temperature of 80degC. The 50 oil is like treacle when it is cold and if you try to take off with cold oil the thick oil simply cannot draw into the oil pump inlet fast enough so the pump will cavitate and then you at best pumping oily foam to the big end bearing and at worst, nothing. Once the oil is up to temp it is far more 'runny' and can flow into the pump inlet with no bother. Once the oil is up to temp it will hold it for quite a while after shutdown, far longer than the air cooled cylinders do which cool quickly. I have often wondered myself how interceptors negotiate the need to take off with warm oil.
With our radials the cylinders heat up pretty quickly whereas even in summer, the SAE50 mineral oil can take 15 to 20 mins of high idle running to achieve takeoff temperature of 60degC with a do not exceed temperature of 80degC. The 50 oil is like treacle when it is cold and if you try to take off with cold oil the thick oil simply cannot draw into the oil pump inlet fast enough so the pump will cavitate and then you at best pumping oily foam to the big end bearing and at worst, nothing. Once the oil is up to temp it is far more 'runny' and can flow into the pump inlet with no bother. Once the oil is up to temp it will hold it for quite a while after shutdown, far longer than the air cooled cylinders do which cool quickly. I have often wondered myself how interceptors negotiate the need to take off with warm oil.
There is oil dilution available to deal with the thick oil issue, but its not used now, because it comes with its own issues.
Our CJ-6 has a 130ºC CHT minimum and 35ºC Oil temp minimum before operating over 1,000 RPM. With everything closed it will always reach CHT first. The frustrating thing is that the vernatherm opens at 35º, so just when you reach temp, it opens and dumps a whole lot of cold oil out of the cooler, and brings it back down 3-4 degrees.
Thanks, I have always wondered about the difference, the air cooled motorcycle engines I had would be sizzling after 30 minutes on tick over.
