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The context of this thread is prior-1942, so waiting for the R-2800 and the P-47 isn't a viable solution, unless there is another what-if scenario to dramatically speed their development.
Exactly. The P-51 could easily perform all low level activity including tactical support. While not the best tactical support aircraft it performed quite well in this role. And, if the AF had been willing, just about any Merlin could have been inserted to allow the P-51 to outperform all ETO aircraft at whatever time the engine was installed. Delaying the second aircraft to allow development of the 2800 provides all the aircraft you would need to partner with the P-51. The Allied war machine would suffer in '42, but really start to get its legs under it in '43.As long as it is a 'what if' based on objective judgment of an airframe potential in early 1940 to go to war with in 1942, and setting priorities around both producing the airframe/engines with an eye toward improvement....
I would select XF4U/XP-51A as the foundation and move to license the Merlin, focus on R2800 extentions - and steal the FF then the Mg 151 to arm both... or extend the M2 to 60 cal/15mm to get minimum explosive round capability.
and steal the FF then the Mg 151 to arm both... or extend the M2 to 60 cal/15mm to get minimum explosive round capability.
Not really, you would have to see the pictures.
Both the saddle pack (which replaced all the rear canopy in back of the metal framing and covered the original intake, and bulged out to the sides considerably--really ugly) and the belly pod (it looks like a jet booster pod, big hole in the front end) contained both turbo and intercooler. As I have said before, speed below rated altitude was cut by 40-45mph.
They look like "add-ons". a plan to make a pack to modify existing aircraft rather than build it in?
If they could have stuffed a turbo into the P-39, why didn't they?
Please look at the P-39E and P-63 for what Bell engineers though was needed for a two stage supercharger and they still didn't have an intercooler (they wanted one but the sub contractor couldn't deliver).
Why build long fuselages and bigger wings if you could get the engines in a P-39?
The P-39/P-63 concept has a problem. The engine is just in back of the CG with the pilot on the CG with the guns in front (and nose wheel) there is no place for fuel in the fuselage without doing something silly like sticking it the tail. The wing center section and wing roots were full of radiator and oil cooler and landing gear. This pretty much leaves the wing lading edge and middle for fuel. You want the fuel tanks centered on about 25-30% of the wing cord. other locations lead to handling changes as the fuel burns off. Many aircraft had instructions as to which fuel tanks should be used first. P-39 already had a CG problem with the ammo, the plane handled differently with full ammo and empty.
You can have a lot of unused volume in an airplane. that doesn't mean you can stick what ever you want where ever you want.
As far as the intercooler goes, it may have been a sub contractor to Allison that failed to provide a satisfactory unit. The subcontractor was a radiator company. I don't know who designed the intercooler on the XP-39 but that was obviously fouled up.
The P-39 was a small , well streamlined aircraft. It's drag figures are second best next to the Mustang of all US fighters. Anything you do to it that increases frontal area or increases the amount of air that flows through ducts is going to increase the drag. NACA thought that the original XP-39 needed as much as 7000cu ft of air per minute for the intercooler, and that is for a 1150 hp engine. Over 8000 cu ft per minute for the 1325 engines used in later P-39s? Actually you don't need cu ft of air per minute, you pounds of air per minute which means you need twice the cu ft of air at 20,000ft or so than you do at sea level. Fixed ducts won't do it, you need an adjustable duct.
This was the problem with all turbo charged planes (and planes with two stage superchargers) they were slower at low altitudes where a single stage super charger could provide the air needed by the engine and only got faster than the single stage planes when they reached an altitude at which the single stage couldn't provide the same (or close) total boost. The two stage supercharged plane always had more drag.
A P-51A pulling 1480hp (WER) was about 20mph faster than a P-5B using 1450-1485hp at 5,000 to 10,000ft. It is only above 11,000-12,000 that the P-51 B starts to out run the A.
Now those Bell mock ups may have been higher drag than a more integrated installation may have been but but a turbo P-39 was going to be slower (20-30mph?) than the non turbo version up until 12,000-15,000ft.
No problems with your estimates. Again, it's the good numbers of good performers @ 20K that 'we' are lacking prior (mid?) 1943.
added: How about P-39(N?, Q?) with the -81 engine (the one from P-51A). Feasible for mid 1943. Or the P-40 with that, along with some weight drag reduction - in hindsight makes more sense than Curtiss producing P-47s that weren't used
All good alternatives SR - but wouldn't it more fun to break the German patents?