Warm up an engine

Read that the IJN ran their aircraft engines from start cold on the deck to warm up for 15 minutes.

The hangers didn't have enough ventilation to warm them indoors.

So what the warm up procedure and what's the minimum time needed to do this safely. This is relevant to how fast the IJN could get off a strike package.

15 minutes seems like a long time to me for air cooled engines.

You have to warm up the whole oil supply.

Warm up times could/would vary based on Outside Air Temp.. As stated above, ALL of the oil needs heated to a specific temp before flying, which includes the 10, 20, 30, etc. gallon oil tank as well. As an example, the AT-6 (R 1340-AN-1) oil temp needs to be 40C minimum/95C maximum for takeoff. Each engine manufacturer would differ.

Our CJ-6 needs 130ºC for CHT and 35ºC for oil temp. On a cold morning, that can take 10 minutes even with the cowl gills closed, so 15 minutes for a large radial wouldn't be excessive - it could be even longer.
And as others have said, the oil takes the longest to come up to temperature as you've got so much to heat up. For example, I can get the engine to 130 for taxying, and taxy to the runway, with the oil just reaching temp when I get there for run-ups.

As for warming them indoors, besides electric heater elements (not sure if these were available during WW2), I don't think there is any way to heat an engine safely indoors, regardless of the ventilation.

I would think in the South Pacific in the summer time it would be "warm" even at night. 15 minutes is a long time when you are trying to launch.

Cheers,
Biff

BiffF15 said:

I would think in the South Pacific in the summer time it would be "warm" even at night. 15 minutes is a long time when you are trying to launch.

Cheers,
Biff

Click to expand...

It takes longer than you think to get the oil from 20 to 40 degrees. The Tiger moth, even during summer, you have time after starting it to get your passenger kitted up, get you kitted up, get them into the aircraft, then get yourself in the aircraft before it gets to operating temp.

Could engine oil be stored outside the aircraft, heated and pumped into the engine? What about the electric block heaters us Canadians have in our oil pans? On my old Triumph I had a magnetic heater that I affixed to the outside of the oil tank. It would heat that oil up to running temp in the coldest riding weather.

For what it's worth, the USN's wartime Aircraft Characteristics and Performance datasheets, in the calculation of the aircraft's combat radius under various conditions, included the fuel consumed in 20 minutes of warm-up time.

Admiral Beez said:

Could engine oil be stored outside the aircraft, heated and pumped into the engine? What about the electric block heaters us Canadians have in our oil pans? On my old Triumph I had a magnetic heater that I affixed to the outside of the oil tank. It would heat that oil up to running temp in the coldest riding weather.

Click to expand...

You're talking about a heater big enough to heat 20-30 gallons of oil quicker than a 2000+ cu. in. engine.
How big a heater do you think that would be ? How much of a electrical demand would that make on a carriers electric generating capacity.
You can't compare that to heating 4 or 5 quarts in your Triumph.
Or if you kept the oil separate and warm, can you imagine trying to add that much oil to 10-20 fighters or a flight deck at dawn.
The mechanics started the engines, by the time the pilots had done their preflight, and got all strapped in, probably used up a good part of that 15 minutes anyhow.
It takes me over 5 minutes to get in a race car , ( through the window) all straps tight, helmet tight, gloves on, etc. and I've been doing it 20 years.
The way they did it was the best way to get it done. because you want more than just the oil warm.

The way the Russians did it on Eastern front winters was to put a sort of tent around the engine, and built a fire below the engine, no kidding.
I doubt that would work too well on a carrier.

I would assume that the IJN had poor lubrication oils in the 1940s in comparison to today

Admiral Beez said:

Could engine oil be stored outside the aircraft, heated and pumped into the engine?

Click to expand...

That is how the IJN planned to get around the engine warm ups on their I-400 submarines.
Dont know if it ever happened though

tyrodtom said:

The mechanics started the engines, by the time the pilots had done their preflight, and got all strapped in, probably used up a good part of that 15 minutes anyhow.

Click to expand...

When HMS Glorious discovered Scharnhorst and Gneisenau were approaching the mechanics/handlers were ordered to bring up and arm the five working Swordfish from the hangar. I would have been tempted to break protocol and start them in the hangar or as soon as they reached the deck, though a spinning prop will be dangerous to anyone confined nearby. Poor devils though, they probably needed 40 mins to get the torpedoes fitted, aircraft fueled and engines heated.

Of course a trio of Glorious' Gladiators circling 15-20 km from their carrier would have given enough time for even the most otherwise negligent commander to rouse his aircrews, handlers and fitters to get the Stringbags armed, fueled and oil warmed up in time to launch.

The Pegasus on the Swordfish only required the engine oil to be +15°C (not +5°C) for takeoff. As the action was in June, the engine oil was very likely at temperature prior to startup.

Edit: I spoke out of turn. +5°C was wrong. The Pegasus III.M and XXX has a maximum oil temperature for takeoff of +15°C. The Pegasus X, XVIII, 22, 29, 32, all Perseus, Taurus and Hercules are +5°C.

Regarding Tyrodtom's observation of Russian warm up technique, one book (can't remember which) discussed a Russian mechanic who came in and surrendered. During conversations, he was asked how they warm up engines. He told them they open the cowls and make a fire under them. After much doubting of his story, the Germans allowed him to show them how it was done. One aircraft was moved away and at gunpoint the Russian went through the procedure. The aircraft did not burn and then was started normally. My guess is it was too cold to ignite anything on the aircraft.

At the Planes of Fame, they fly 3 - 4 P-51s, a P-47G, an F4U-1a, a couple of AT-6s, an A6M5 Model 52, a P-40N, A Skyraider, a B-25, a Seversky AT-12, a TBF,an SBD, a replica Fw 190F (R-2800), a P-38J and a few more. All of them warm up for 15 minutes or more between strartup and takeoff, even in summertime in Southern California. In this case, it is a function of the distance from the museum to the active runway and waiting for traffic. There might be a few warbirds that cannot take a 15-minute ground run due to overheating of the coolant but, if we had one, it has been modified to tolerate it since that is the reality.

The P-38 usually requires the radiator doors to be wide open when you taxi in from or out to a flight, but it doesn't seem to cause overheating if you have them open. Perhaps it can if the run gets expended.

When I see films of WWII bombers or fighters launching a big raid, they have maybe 50 or more airplanes running at the same time, in line, waiting to take off. That will take 15 or more minutes, so they did that even back in WWII, at least on big missions. The only warbirds I have heard of that have issues with ground running have coolant issues, not overheated oil issues. In those cases, you can call the tower and tell them you have a limited ground run time and they can usually help you out unless you are at a big airport with a lot of commercial traffic. I've never seen an air-cooled radial have to shut down from temperature issues on the ground. They don't produced enough heat around idle to overtemp rapidly, but would overtemp if operated at higher power on the ground for an ectended period.

The racers at Reno usually have 10 - 15 minutes between startup and takeoff even with race-modified hot-rod engines. Not saying there isn't a definite gound time limit, just observing operation of many warbirds in period films and today, including running for 35+ minutes on the gound several times in succession when you put new rings into a Merlin or Allison. It just doesn't come up as an issue in use.

Simon Thomas said:

The Pegasus on the Swordfish only required the engine oil to be +15°C (not +5°C) for takeoff. As the action was in June, the engine oil was very likely at temperature prior to startup.

Edit: I spoke out of turn. +5°C was wrong. The Pegasus III.M and XXX has a maximum oil temperature for takeoff of +15°C. The Pegasus X, XVIII, 22, 29, 32, all Perseus, Taurus and Hercules are +5°C.

Click to expand...

Given who was in command it wouldn't surprise me if each Swordfish was drained of oil when stored below.

Warm up of a particular plane in in particular conditions is one thing, air forces and carrier fleets need to plan missions and calculate possibilities. 15 or 20 minutes for warm up can be also be used in the general calculation of fuel consumption or the planning for a carrier mission for position of the fleet or disposition of recon planes.

gumbyk said:

Our CJ-6 needs 130ºC for CHT and 35ºC for oil temp. On a cold morning, that can take 10 minutes even with the cowl gills closed, so 15 minutes for a large radial wouldn't be excessive - it could be even longer.
And as others have said, the oil takes the longest to come up to temperature as you've got so much to heat up. For example, I can get the engine to 130 for taxying, and taxy to the runway, with the oil just reaching temp when I get there for run-ups.

As for warming them indoors, besides electric heater elements (not sure if these were available during WW2), I don't think there is any way to heat an engine safely indoors, regardless of the ventilation.

Click to expand...

Admiral Beez said:

Could engine oil be stored outside the aircraft, heated and pumped into the engine? What about the electric block heaters us Canadians have in our oil pans? On my old Triumph I had a magnetic heater that I affixed to the outside of the oil tank. It would heat that oil up to running temp in the coldest riding weather.

Click to expand...

An electric heater would be simple and perfect. A BMW 801D2 had 55L in its tanks. (13.6 imp galls or 14.55 US gal). I don't think any other engine would vary much.

A simple 300 watt heater element or 'cartridge' not much bigger than a light bulb would keep this warm. It would simply be screwed into a tapped hole side of the oil tank, the hole would be maybe 3cm. One wouldn't even need a thermostat. It would take hours to heat up the oil but the idea is to have it ready. A more rapid heat up could be achieved with a more powerful element and a simple bimetallic thermostatic switch. Once the tank has achieved temperature the electric power could be switched to blowing hot air through the engine cowling. We use a 375 Watt element on a reducer gearbox in the mining industry that weighs half a ton.

Below is ducted heating equipment hastily developed for the Ju 52. The He 111 generally didnt need this due to its fuel injected engines.

I think there may be some confusion going on here about what is normally required to warm-up an engine that can be started at the ambient air temperature - and what may be required to warm-up the engine/engine oil before the engine can be started in the ambient air temperature.

Starting an engine in -40°F/-40°C for example, was problematic in WWII, because of oil thickening due to the cold. At low temperatures it was not uncommon practice among all(?) the WWII combatants to warm up the engine as a whole - with the oil in it - using some form of external heater. There were purpose designed heaters (an example of which Koopernic just posted above) - electric, kerosene, gasoline - used for this purpose, and if necessary simple fires using whatever was available would be employed. Some form of enclosure to contain the heated air was usually used if available and practical.

Somewhere on the internet, I once ran across a video of several B-17s (somewhere in England) starting their engines during cold weather, with cloth enclosures/tents surrounding the engine nacelles. The cloth enclosures/tents were there to contain the heat output of the kerosene heaters set up under the engines.


Once the engine is started, the normal engine warm-up period begins. The engine will have to be run until the minimum oil temperature required for TO is reached (ie a minimum of 15°C for the Pegasus III.M in the up-thread example given by Simon Thomas).


Depending on the weather where you live, you may see examples of this type of thing in everyday life. The abrupt temperature changes when driving from one one region of the US into another region will sometimes catch over-the-road truckers by surprise. Here in Minnesota for example, it is not uncommon to see diesel powered semi-trucks immobilized along side the road when there are sudden temperature drops due to the arctic air masses moving south. The standard commercial diesel fuel (diesel #2) normally used will 'gell' at about 15°F/-9°C. This can occur even when the truck is running and moving, and becomes more likely to do so as the temperatures drops further. When this happens heaters will sometimes be set up below the appropriate areas of the truck to heat the diesel fuel tanks.

Even with ~modern engine oils, it may be necessary to heat the engine oil in the same manner if the temperature drops below about -20°F/-29°C.

Usually the heaters will be of the electric or kerosene type, but just this winter I saw at least one trucker using charcoal briquettes in heating pans (designed for the purpose) set-up below the engine and fuel tank.

In Alaska, using heaters to heat the engine/engine oil is relatively common. During a winter cold snap in Alaska, for the people without engine heaters of some sort, it is not uncommon for the vehicle to be immobilized for several weeks.