Sheet/corrugated metal oil cooler LE air intake - how good/bad for 'other' planes?

[tomo pauk]

When one reads a bit about the Avia B 35/135 ( 'Czech Spitfires' (TM by yours truly)), one things catches the eye - the curious looking oil cooler. It was not featuring an air inlet, but the outer side of the cooler was a sheet/corrugated metal around which the airstream was flowing. You can note it on this picture, the grayish surface at the inner part leading edge. (also here)
At the opposite wing leading edge, the carburetor air intake was located, the installation as such was seen at He-100, F4U and DH Hornet, to name a few. In this picture, a rectangular-shaped entry to the intake can be seen, protected by some netting. (also here)

Wonder how much the installation(s) like this were to improve streamlining (where feasible, of course), earning some speed in process?

 

[Shortround6]

The problem with the finned oil tank in the leading edge of the wing is that is really has limited cooling ability. It may have worked on 800-1000hp engines but the more powerful engines need more surface area and there is no way to adjust it. A 20 minute climb to altitude at climbing speed vs high speed dash?
I believe the Hawker Hurricane used an oil tank in the leading edge but without fins?

Some racing planes of the 30s used an oil tank with one side exposed to the air stream but it really wasn't good enough ( especially on the in line air cooled engines which got rid of a lot of heat through the oil) and many racers had to slow down on later laps as the engine and oil temp climbed.

 

[tomo pauk]

The air-cooled inlines were not too mcuh in use in ww2, though.
At the Avias, the oil cooler was placed at just only at the port wing - stick another of the same size at starboard wing and use (stream oil through it) it when oil temp is demanding that, in a 1500 HP plane? SHould make also a bit more redundant system?

 

[Shortround6]

The point is you have only the surface of the tank to cool the oil, increased by putting fins on the tank. Oil cooler has the surface area of either the tubes running through the honey comb

or through the fins of a fin type cooler like a car radiator. You can get a lot more cooling per minute from a proper oil cooler than from a tank or finned tank.

You also cannot keep an oil tank/cooler in reserve as the oil will be too thick to flow properly when introduced into the oil circuit leading to engine failure. no multi grade oils in WWII

Aircraft engine oil was often SAE 50 or 60 which is why they spent so much time warming up the engines on the ground before trying to take-off.

 

[tomo pauk]

Good points, I've just read that Avias used outer surface of the oil tank as a cooler. Interestingly enough, the late examples were using smooth instead of corrugated outer skinning.
So for an engine with greater power one should probably use two such tanks/radiators.

added: now that we're at it, can anybody shed some light at the oil cooler of the MS-406?

 

[nuuumannn]

The Hurricane's oil cooler was in the centre of the radiator as a circular section seen here in this rear view.

On the Spitfire, one half of one of its underwing radiators was an oil cooler. This is a Spit XIV, so the radiators are rather large.

 

[tomo pauk]

Thanks for the pictures.
For single-stage Spitfires, the oil cooler was a 'stand alone' round item under one wing, under other it was the engine's cooling radiator. WIth advent of 2-stage engines, the oil cooler was of rectangular shape, positioned ring behind inter-cooler radiator.

 

[nuuumannn]

Yep, I have a photo of one of those too, if only I could find it...