Junkers Ju 86

This aircraft was designed and built in the mid thirties, and it had diesel engines.

Now as someone whos on his fourth diesel I have to ask how did they cope with waxing in the cold air at height?

PNK wrote:

Once an engine is hot and running would that suffice?

Not quite,
Waxing will take place in the Diesel fuel tanks unless the tanks are heated. The return pipe from the injector pump will supply slightly heated oil back to the tank, but heating elements are used in modern Truck tanks. I suppose that was a possibility in the late 1930's.

Fuel lines will wax the fuel if they are in a cold air stream, again suitable lagging of those lines are used on trucks. Suitable additives keep modern diesel fuel liquid, back then the normal practice would have been the mixing of spirit fuels such as high octane aviation grade petrol into the Diesel. This would have a detrimental effect on injector pumps if the ratio of Diesel/petrol was wrong.

Thanks for the info, I suspected that may have been the case.

So I have to ask why the built the aircraft with diesel engines? I suppose there were no carbs or spark plugs to worry about.

Dont take my word for it but ....The JU86 was designed as a high altitude recon aircraft. I read or learned somewhere that Diesel engines were used to eliminate contrails. It seems probable as you always get condensation from petrol engined cars in cold weather, My Puegeot diesel only issues a little condensation at first...but that does not explain jet engines, also oilers, and contrails at altitude...hmmmm, theory shot perhaps?

Thats a good point, all my diesel cars have also produced very little condensation.

Ive had another tink about the condensation trails. These only occur between roughly 28000-35000 feet, so there may be no real advantage of diesel engines in this regard.