Warm up an engine

[ThomasP]

Two other points.

The Japanese engine oils were similar in quality to the other nations.

The RN/FAA did not drain the oil out of their aircraft when stowing them below (I know you were being sarcastic Admiral Beez, but others may not). They did, however, normally drain the aviation fuel from the aircraft when stowing them below. This was done to prevent/reduce the chance of fires in the hangar. This also prevented the warm-up of engines in the hangar.

 

[Koopernic]

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.

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.

I worked in Kiruna Sweden for a while while working at the Iron Ore Mines. The car parks at all of the hotels had a standard outlet for keeping automobiles pugged in over night. Both the engine and the passenger compartment was kept warm. The power draw I think was 300W. (Narvik is less than an hour from this, its where Operation Wilfred tried to cut of the German Iron ore supply)

The Russians diluted their oil with petrol and the Germans copied them. Once the engine was up to heat the petrol evaporated off.

 

[tyrodtom]

We seem to be mixing systems to warm the oil up enough to start the engine, with systems with enough power to warm the entire engine so it can develop full power safely.
Warming the oil so it flows enough to lubricate may speed the overall warmup some, but the engine internals ( pistons, rings, cylinder walls, etc.) need to be hot and expanded before you go to full power, or parts break.
About the only way to do that dependably is to run the engine.

 

[DerAdlerIstGelandet]

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.

Electric heaters are common but you still have to warm the engine up further after starting. When I used to fly up north with temps regularly below freezing we would keep the aircraft hangared over night. We would preflight in the hangar as much as possible, but sometimes could not, or sometimes the flight would be delayed. We would put electric heaters inside the cowlings, but they would not raise the temp to operating levels. They just kept the oil at a temp you can start the engine at.

 

[gumbyk]

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.

We've got one fitted, but don't use it. It's a pad that gets stuck onto the outside of the tank. We stopped using it after it almost caused a fire though!

 

[Koopernic]

We've got one fitted, but don't use it. It's a pad that gets stuck onto the outside of the tank. We stopped using it after it almost caused a fire though!

I'm curios what caused the fire precisely? Was there a 5 Y analysis you are aware of?

It sounds like an aftermarket retrofit. Engine and airframe makers need to incorporate them as a properly engineered solution. Lube and grease system heaters are often rubbish in any industry. Folks regard them as a simple device and won't spend money on them because they don't perceive the risks of a poorly engineered product.. You can spend anywhere between $150 to $2500 on a heater for a 44gallon or 200L grease drum. I've seen the cheap ones cause a drum to smoke and others to blow a 1 mm hole in the side. A heater pack should be either so low in power and power density and so well fitted it can't overheat or incorporate 2 failsafe thermal cut out devices, say a thermostat and a positive temperature coefficient cutout.

Even Jets need to warm up. The Pratt & Whitney PW1000G geared turbofans needed 8 minutes to warm up at one point, 2-3 minutes worse than previous generations negating some fuel savings. (Now fixed incidentally). There is low hanging fruit in fuel savings in preheating oil and electric ground taxiing wheras engine and airframe makers struggle to get 0.5% savings.