Given criteria (see post), what's the best radiator arrangement for a single seat/single engine fighter?

[BarnOwlLover]

Given that you have an aircraft that uses a liquid cooled engine, and a certain list of criteria, what would be the best radiator housing arrangement for a single seat, single engine fighter?

Criteria:

--Aircraft has to have provision to carry fuselage mounted cameras (ports out to the side/sides and, preferably, ventral).
--Conversion for being a dual control trainer with minimal changes beyond adding the second cockpit.
--Allowing for max fuel capacity (wings and/or fuselage) while maintaining CG (radiator(s) can be used to balance CG as well)
--Present a minimum of drag (at least some useful use of the Meredith effect preferred)
--Optimum (if possible) balance of aero efficiency, cooling efficiency, and ease of servicing and maintenance.

 

[SeaWorldOrBust]

I'm inclined to say in the wing root as with the Mosquito, Hornet and some apparently promising Hawker Tempest/Fury prototypes. Of course the Mustang radiator is an obvious answer as well, but may impede the ventral camera. At least as important to placement though is the design of the radiator itself. Clever placement only does so much if it's twice as big as it needs to be.

 

[wlewisiii]

It must be the way they did it in P-39 since the cameras can then go in the armored nose ...

What?

 

[Sisu]

Given that you have an aircraft that uses a liquid cooled engine, and a certain list of criteria, what would be the best radiator housing arrangement for a single seat, single engine fighter?

Criteria:

--Aircraft has to have provision to carry fuselage mounted cameras (ports out to the side/sides and, preferably, ventral).
--Conversion for being a dual control trainer with minimal changes beyond adding the second cockpit.
--Allowing for max fuel capacity (wings and/or fuselage) while maintaining CG (radiator(s) can be used to balance CG as well)
--Present a minimum of drag (at least some useful use of the Meredith effect preferred)
--Optimum (if possible) balance of aero efficiency, cooling efficiency, and ease of servicing and maintenance.

It sounds like you are describing a Mustang -- I believe that F-6Ds and such had a vertical camera position just behind the scoop and in front of the tailwheel. The Temco TF-51Ds worked well as a trainer, other than being ugly (making a P-51 ugly is a good trick!). I guess the fuel/CG thing might not fit a Mustang, but does it matter, given that Mustang pilots did fine with the fuselage tank when they knew what they were doing?

What am I missing here?

 

[SeaWorldOrBust]

What am I missing here?

I suppose only that the OP seems to be implying he wants a new design, lol

 

[BarnOwlLover]

If you look at how the ventral radiators are located on say a Yak-3 or a Mustang is that there's enough room behind the pilot for a second seat (with fuselage fuel tanks removed on the P-51).

Also, is there a "good way" to have Spitfire type radiators other than the Spiteful or Me-109 solutions?

 

[wlewisiii]

TF-51 ...

North American TF-51D Mustang - The Collings Foundation

Fast, well made with the ability to fly long distances, the North American P-51 Mustang became one of the world’s most successful and recognizable aircraft. The bombing missions over the skies of Europe were taking very heavy losses from Luftwaffe fighters. The allied aircrews desperately needed...

www.collingsfoundation.org

 

[PlasticHero]

How much lift (if any) is lost by a wing root radiator? I mention this because jet engine intakes used to be in the wing but later went to pylon mounts. Increase in engine diameter? I like the idea of having the radiator ahead or behind the wing because of compressibility issues. (i have no specific aerodynamic knowledge)

 

[SeaWorldOrBust]

If it's well designed it will actually improve lift, as the outlet will increase pressure beneath the wing. It's been suggested that that was actually one of the factors in the Mosquito's high altitude performance.

 

[tomo pauk]

It's been suggested that that was actually one of the factors in the Mosquito's high altitude performance.

[citation needed]

 

[BarnOwlLover]

Uhm, I didn't mention anything about the the Mosquito's high altitude performance anywhere in this thread.

 

[SaparotRob]

Were you thinking about it?

 

[SeaWorldOrBust]

[citation needed]

I only say "it's been suggested" because I don't remember by whom, where or how reliably. May well be bullshit, though intuitively I think it makes some sense.

 

[tomo pauk]

I only say "it's been suggested" because don't remember where or how reliably.

Kinda my point.

 

[SeaWorldOrBust]

Okay well I'll be sure to qualify my statements more carefully next time.

 

[SaparotRob]

I learned that the hard way.

 

[BarnOwlLover]

If we're going to go the ventral radiator route, what would the best arrangement be: what the P-51 used, or maybe a refined version of what the Yak-3 or later Yak-9s used?

 

[SeaWorldOrBust]

My impression was that the Yak radiators weren't that special — and in fact given the cooling difficulties they had with later versions of the klimov (which still weren't excessively powerful), may have actually been rather poor. It seems to me the relatively high speeds the later Yaks achieved for their power were primarily a function of their exceptionally small size. I imagine a more refined version of that radiator layout would probably be more or less comparable to a Mustang radiator, and I have to admit a Yak-3 with a Mustang-style radiator is a pretty intriguing prospect as it would not only reduce drag on the already slippery little Yak, it may allow the VK-107/108 to function properly without overheating. Given the already impressive performance prototypes with those engines achieved, reducing drag on top of it could land you with a very competitive late/post war fighter, and that's before considering further development potential of the Klimov with higher octane fuels. I imagine had the jet not come along that's probably more or less the direction development would have gone, but thus it ever was for the promising late-war piston fighter. Though the larger Yak-9 may be a better candidate for all the roles we're talking about here.

 

[z42]

I mention this because jet engine intakes used to be in the wing but later went to pylon mounts. Increase in engine diameter?

For multi-engine subsonic jets, yes I think the reason for pylons is that once bypass engines (turbofans) were invented and it was quickly discovered that fuel efficiency was strongly correlated with the bypass ratio, the engines just didn't fit into the wing roots anymore. Also you see the pylons jut out a bit in front of the wing, I think this is in order to ensure that engine gets clean airflow to prevent compressor stalls. For a longer version of this argument see Tradeoffs in Jet Inlet Design: A Historical Perspective | Journal of Aircraft (you can find the article free IIRC on the authors university site).

 

[z42]

If it's well designed it will actually improve lift, as the outlet will increase pressure beneath the wing. It's been suggested that that was actually one of the factors in the Mosquito's high altitude performance.

Hmm, that's an interesting argument! But OTOH, if you have the outlet in a high pressure region, then you'll have more backpressure in the radiators and thus more drag from the radiators. I don't have any numbers showing anything either way, so just idly speculating..