Reluctant Poster
Tech Sergeant
- 1,630
- Dec 6, 2006
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The figures are from a test and the test plane had the five .50s. Not that the rest of the planes did.
The plane was even slower at 60 in.
402.5mph, were the 440mph comes from is anybody's guess.
as far as conservatism goes, it would be the other way. You can't lie about physical effects like compressibility. It either happens at a certain speed or it doesn't. If the plane will actually do 440mph and you "lie" about it because you are being conservative you are going to get people killed.
The P-38 was a 1938 design. It is little wonder that a newer plane could have less drag, especially at 400mph because you are running into compressibility effects in drag all over the airplane, not just wing lift.
and again, it is important to remember the altitude. The test P-38J could hit 413mph at 24,000ft using 60in. The superchargers would not deleiver 70in at that height but in the thinner air the plane pickup about 10mph of speed over the 19,800ft height.
Actually the cooling air for the exhaust is fed and discharged from several fixed vents in the belly cowling. These definitely could have been improved. Ditto the exhaust for the oil coolers and waste gates.The P-47 concealed the turbocharger within a shroud. There are no extraneous intakes. All the air for the induction system including the intercooler comes from the chin intake which also serves the oil coolers. A very slick arrangement.
In such a small slick plane, quite remarkable.The P-47 concealed the turbocharger within a shroud. There are no extraneous intakes. All the air for the induction system including the intercooler comes from the chin intake which also serves the oil coolers. A very slick arrangement.
I was specifically referring to intakes not vents. The combustion air, intercooler air and oil cooler all are drawn from the chin. I am not aware of any intakes elsewhere on the fuselage.Actually the cooling air for the exhaust is fed and discharged from several fixed vents in the belly cowling. These definitely could have been improved. Ditto the exhaust for the oil coolers and waste gates.
Sorry to quote myself, but I didn't submit this to Wikipedia. I meant to say that I copied and pasted it else where (in a thread talking about Mustangs vs V1 flying bombs). But it does show two ways to try and do the same thing using what was available or would be available soon.I posted this copied and pasted quote from Wikipedia (though it cites official reports and info) and shows that while NA worked on maximizing the airframe and later adding more power, the British were looking at boosting power while making as few changes to the basic airframe as possible.
"While North American was concentrating on improving the performance of the P-51 through the development of the lightweight Mustangs, in Britain, other avenues of development were being pursued. To this end, two Mustang Mk IIIs (P-51Bs and P-51Cs), FX858 and FX901, were fitted with different Merlin engine variants. The first of these, FX858, was fitted with a Merlin 100 by Rolls-Royce at Hucknall; this engine was similar to the RM 14 SM fitted to the XP-51G and was capable of generating 2,080 hp (1,550 kW) at 22,800 ft (7,000 m) using a boost pressure of +25 lbf/in2 (170 kPa; 80 inHg) in war emergency setting. With this engine, FX858 reached a maximum speed of 455 mph (732 km/h) at 17,800 ft (5,425 m), and 451 mph could be maintained to 25,000 ft (7,600 m). The climb rate was 4,500 ft/min (22.9 m/s) at 1,600 ft (486 m) and 4,000 ft/min (20.3 m/s) at 13,000 ft (3,962 m).[60]
FX901 was fitted with a Merlin 113 (also used in the de Havilland Mosquito B.35). This engine was similar to the Merlin 100, fitted with a supercharger rated for higher altitudes. FX901 was capable of 454 mph (730 km/h) at 30,000 ft (9,100 m) and 414 mph (666 km/h) at 40,000 ft (12,200 m).[61]"
Yes - the primary distiction in allowable loads between B/D & H was 7G allowable for B/D versus 4G for H landing gear (including tires).Just read some of the Building the P-51 Mustang book I got over the weekend, and it suggested that the H model would've likely had to have operated from well prepared runways vs the D model because of the landing gear. Any truth to this, and what could've been done about it? I'd suggest a lightened version of the D's or maybe even the F-82's landing gear.
I'd say that this is the only concession that should be made to those who said that the H was "weaker" than the D model (otherwise it was just as strong if not stronger in terms of airframe). I always thought that the H's landing gear looked a bit spindly, especially in comparison to the rest of the aircraft. Not to mention that there was simple logistics involved for Korea. Only 555 P-51Hs got made vs almost 7800 D (and 1500 nearly identical K's), plus I heard that for every P-51D that got made, almost three more could be built from spares. Not sure if that held true for the H model, or even the F-82.Yes - the primary distiction in allowable loads between B/D & H was 7G allowable for B/D versus 4G for H landing gear (including tires).
The stress analysis to determine limit loads for the B/D included inspection of spar and local carry through structure, whereas the H it was not necessary except to check off all the boxes for load limits.
Additionally, can't put a D gear into an H wing without major re-design of LE for the straight LE of the H.
These were major questions when finalizing decision not to use H in Korea. In addition it was still important to ADC as the H had far more range than F-94 and F-86. IIRC most of the H's that existed in central US were moved to west coast National Guard unit squadrons.
The H was a 'lightened version' of the D. The only choice to lighten the D was to reduce fuel fraction at takeoff.
Agreed. Actually the H was stressed at 7.5 G Limit loading or full internal combat gross weight of 9600 pounds. The P-51B at same max internal gross wight of 9600 pounds has a 6.66 g Limit load based on original 8000 design gross weight. The D , 6.33 g Limit load.I'd say that this is the only concession that should be made to those who said that the H was "weaker" than the D model (otherwise it was just as strong if not stronger in terms of airframe).
The contract spares allocation was usually in order of 20% production article assemblies. The original two P-51Ds were from P-51B-1 spare fuselage and empennage, attched to first two production P-51D wings.I always thought that the H's landing gear looked a bit spindly, especially in comparison to the rest of the aircraft. Not to mention that there was simple logistics involved for Korea. Only 555 P-51Hs got made vs almost 7800 D (and 1500 nearly identical K's), plus I heard that for every P-51D that got made, almost three more could be built from spares. Not sure if that held true for the H model, or even the F-82.
The loaded -51H was 2000 pounds heavier than XP-51F. The F & G were both designed at 7.5/11.25 for combat gross weight.I wonder how similar the H's landing gear was to the F/G models, which though the H was based on them, they were designed for a lower weight due to carrying less fuel. guns, and etc, and also not needing to be re-stressed to the 7+/11+ G limit to account for those increases (which added some weight as well).
Of course, to put a beefier undercarriage on the P-51H might require the wing gaining the "kinked" inner LE that the earlier versions had.
This kind of goes into the "what if" category, but it makes me wonder what a P-51D built to the F/G load standards, keeping the beefy landing gear, and using the H's/LW's aero refinements (radiator scoop, supercharger intake, wing profile) would've been like, or, as discussed elsewhere, an Allison powered version for tactical recon.
P-51H, not F. The F had the 1650-3, exact same as P-51B/D through about March 1944. The G was flown to 495mph at Inglewood testing.Just another lightweight Mustang thought. I did read on here that the XP-51G had a normal gross weight and max gross weight of 800 or so pounds more than the XP-51F it was based off. I know that the H was nearly 2000 lbs heavier than the F due to carrying 6 vs 4 .50 MGs and a 50 gallon fuselage tank, as well as re-stressing to keep the AoA G loadings the same when the increased weight was factored in (the fuselage was also nearly a foot longer due to the engine being moved slightly forward and the rear fuselage also being lengthened a bit). I know that the Merlin RM 14 SM (and the 100 series) was slightly heavier than the Packard V-1650-3/-7 that the F used, but that doesn't account for a 800 lb weight gain alone. So I assume that at least some of that weight difference was due to re-stressing due to increased power to maintain strength loadings.
Strangely, reading that, I remember reading that the G weighed 2-300 pounds less than the F, and had about 200 miles less range. Between what I mentioned above (referring to a post by drgondog, one of our resident Mustang/P-51 history experts who's read tons of development documents) and that the F and G should've carried the same fuel load, those points don't seem to make since, though the info that cites reduced weight and range may be either outdated, based on misinterpreted info, or may've cited the G when set up as an interceptor.
For possible reference to that point, again, drgondog mentioned in a post that the F when run on 90 in Hg supercharger boost (which the Packard V-1650-9 and the Merlin 100s could do on WEP/sprint power) was nearly as fast as the G model when set up as an interceptor. Also remember that North American quoted the G as running 472 mph, while RAE tested the G to nearly 500 mph (either 495 or 498 mph). Granted, the opposite was true of the P-51H (NAA tested it a 487 mph in interceptor trim, while the USAAF at Wright-Patterson observed 472 mph max).
Reading these posts would it be that single engined fighters used for what the H model was designed for had reached their limit and a DH Hornet would be the better choice?, there's only so much you can lighten an aircraft and only so much fuel you can pack into it so would it be a fair argument to say it's time for a twin?.P-51H, not F. The F had the 1650-3, exact same as P-51B/D through about March 1944. The G was flown to 495mph at Inglewood testing.
The AAF testing was performed on the H with still troublesome issues with 1650-9 carburetion, not solved until November 1946,
Actually with 205gal internal fuel both the F and G probably Did have sufficient Combat radius with 75gal external tanks to perform Berlin/Munich range target escort. 205gal is equivalent to 184 plus a 20 gal fuse tan, with slightly more usable fuel, With the lower weight/higher fuel frction and slicker drag wing, the F/G both had lower parasite and induced drag. The Breguet equation for cruise range at constant altitude is directly proportional to L/D - which is superior for the Lightweights.IMO, not really an apples to apples comparison. The DH Hornet (in my opinion at least) was the RAF's equivalant to the F-82 Twin Mustang, as both have similar range, and were designed as very long range escort fighters. The P-51H was a long range single seater that basically took performance of the D model one step further. As pointed out previously, the XP-51F and G carried more internal fuel than the P-51D prior to the B/D getting the 85 gallon fuselage tank. The increased wing tanks carried over to the P-51H production model, which allowed the use of a smaller 50 gallon tank that helped with CG/directional stability on a full fuel load.
Not to mention that the XP-51F/G were designed as the ultimate hot rod single seat interceptor fighters from a performance standpoint. It could do relatively long range missions by 1943 standards as well, but it didn't quite have the range even with drop tanks to get to Berlin or beyond, hence why the B/D got the 85 gallon fuselage tanks (for better or worse), and why the H was built as the ultimate long range single seat fighter that could still be an extremely effective interceptor.
For reference, even the P-51B/D when flown light as interceptors (8600-8800 lb gross weight) could outclimb the Hornet (the Hornet often flew under similar supercharger boost ratings) and were only 15 mph slower when running 72 or 75 in Hg supercharger boost. Biggest improvements that the F/G especially and also the H brought was improved top speed (improved aero for all, including a Meredith radiator that produced excess thrust, more power for the G/H) and improved climb due to lighter weight. Even the P-51H as an interceptor could climb at over 6000 fpm. Not the 7000+ fpm that the F managed under WEP/sprint or what the G did with the Merlin RM 14 SM (basically same engine as the Hornet as far as power specs), but way better than most other piston engined interceptors, and quite a lot better than early jets.
Soon after the Korean War began, several northern New England ANG ADC squadrons gave up their P47Ns for P51Hs.IIRC most of the H's that existed in central US were moved to west coast National Guard unit squadrons