These aircraft were proposed to offer a simple solution to the problem of increasing fighter performance with the then existing and foreseeable technology. It's a given that not only in Germany and the U.S. at the time, but around the world, money was tight for military services. Assume for the moment that the German leadership recognized the need for a higher performance fighter than those they were already looking at, and in the U.S. the so called 'Bomber Mafia' did not have such a grip on the USAAC/USAAF doctrine. What if the same rate of development had been accorded these aircraft as was used in the 'favored (bomber as well as fighter) designs'? What would this have meant for the air forces that they would contend with in the future?
Kurt Tank FW 187/ Grumman XP5F 1935/1938 et al.
- Thread starter Akuma
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Granted, the two fighters mentioned in the title were much simpler than their respective competitors that entered service. Not that respective performance was great, both did ~330 mph in real life and with then-current engines. Yes, install two V-1710s on the F5F and two DB 601s on the Fw 187 and performance jumps by a considerable margin, but same was true for the 1-engined fighters that received these. Let alone for the actually new fighters' designs.
Also, fleets of two-engined fighters don't mix well with 'money was tight for military services'.
For the Germans - buying the fw 187s instead of MTT's 2-engined fighters is a major boon.
For the Americans - having a simpler to make 2-engined fighter than it was the P-38, with turbo at the back of nacelle and V-1710 in front gives them more of well-performing fighters.
Bomber Mafia was not to blame for XP-37 and XP-39 being flops, though - these were supposed to be half price of what the (X)P-38 was.
yulzari
Staff Sergeant
These aeroplanes, and the Westland Whirlwind, essentially were shortcuts to larger more powerful engines than were available at the time. @ 2,000bhp fighters in a 1938ish design scale whilst the like of the big DB, Vulture etc. were not going to be in real service until late 1942 at the best. Just as the first jet fighters had two engines (Meteor, He 280, Me262) even though soon thereafter they soon got enough power from a single engine for a small fighter (He 162, Vampire,P80).
The ultimate expression of the piston engined shortcut high power twin was the DH Hornet in the 4,000bhp class. In the absence of OTL more powerful engines this was a way to go. It would be quite a thing to see if an alternate Hornet had RR Crecy engines with 6,000bhp and possibly eventually reaching 10,000bhp. It might need something like the Atlas' propellers to transmit that power. Tricky for WW2 materials technology. Contra rotating ones would be more period appropriate. Of course that whole thing would be too late to make a difference by the time it could get to service.
If the projected high power engines are not made and the engineering effort put into earlier jets then the twin engined fighter would make its period brief appearance before the bigger single arrives. Just earlier.
The ultimate expression of the piston engined shortcut high power twin was the DH Hornet in the 4,000bhp class. In the absence of OTL more powerful engines this was a way to go. It would be quite a thing to see if an alternate Hornet had RR Crecy engines with 6,000bhp and possibly eventually reaching 10,000bhp. It might need something like the Atlas' propellers to transmit that power. Tricky for WW2 materials technology. Contra rotating ones would be more period appropriate. Of course that whole thing would be too late to make a difference by the time it could get to service.
If the projected high power engines are not made and the engineering effort put into earlier jets then the twin engined fighter would make its period brief appearance before the bigger single arrives. Just earlier.
- Thread starter
- #4
When the USAAF had a fly-off between the the P-38 and the XP-50 (USAAF version of the XF5F) the XP-50 was the clear winner. I suspect that the main reason the P-38 was chosen was that, due to it's size, the P-38 could be configured to carry a bomb load similar to a light bomber of that period.
Would you be so kind to provide a source for that claim?
- Thread starter
- #6
It has been a while, but I believe I read this in a book that dealt exclusively with the Grumman XF5 and XP50. It might have been one of the series publications that cover individual aircraft. To be fair, the USAAF had apparently settled on the P-38 and were looking at the XP-50 more as a backup rather than a competitor although, according to what I read, this all happened in the very early stages of development of these aircraft.
Reality check:
Lockheed have had hundreds of P-38s ordered by France, UK and USA already in 1940 - before the XP-50 took off for the 1st time, and actual production of P-38s started before the XP-50 took off for the 1st time.
Stuff like 'XP-50 was found to be better than P-38, alas...' (that I can believe you've read in the book) is comfortably along the lines of 390-400 mph XP-39 story, or 425 mph XP-50 story, or the (X)F4U-1 being the 1st 400 mph fighter, or Hellcat being just as fast as Corsair: all of them ended up as not true after there was no answers to the pointy questions, or the answers were opposite to the story.
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- #8
Shortround6
Major General
I believe the key word was "ordered".
However, according to one book.
Plane.................order date........order number.........first flight/delivery
XP-38..................6/23/37.......................1...............................1/27/39
YP-38..................4/27/39.......................13............................9/17/40
P-38.....................9/20/39.......................29............................6/41
P-38D..................9/20/39.......................36............................8/41
Model 322........6/5/40..........................150.........................
P-38E..................8/30/40........................210.........................11/41
XF5F-1................6/30/38.......................1.................................4/1/40
XP-50...............11/25/39.......................1.................................2/18/41
Some of these don't line up with some other sources, like the orders for the 322 was later enlarged and then canceled/transferred back to the US.
I would note that the XP-50 was destroyed during a test flight on 5/4/41 or less than 3 months after first delivery leaving little room for a fly off in the 20 hours of flight time it had gained in it's existence.
However, according to one book.
Plane.................order date........order number.........first flight/delivery
XP-38..................6/23/37.......................1...............................1/27/39
YP-38..................4/27/39.......................13............................9/17/40
P-38.....................9/20/39.......................29............................6/41
P-38D..................9/20/39.......................36............................8/41
Model 322........6/5/40..........................150.........................
P-38E..................8/30/40........................210.........................11/41
XF5F-1................6/30/38.......................1.................................4/1/40
XP-50...............11/25/39.......................1.................................2/18/41
Some of these don't line up with some other sources, like the orders for the 322 was later enlarged and then canceled/transferred back to the US.
I would note that the XP-50 was destroyed during a test flight on 5/4/41 or less than 3 months after first delivery leaving little room for a fly off in the 20 hours of flight time it had gained in it's existence.
Yes.
In April 1940, British and French combined order was for 667 of turbo-less Lightning I fighters, while the USAAF order in that time was 80 of P-38s ('normal' ones, with turboes). In June 1940, British took over the French order, that was changed - the final 524 of the fighter was to be Lightning II - fighters with turboes.
(per "Vee's for victory", pg. 140; FWIW, the same book puts the "390-400 mph XP-39" myth into the trash can)
Geoffrey Sinclair
Staff Sergeant
- 894
- Sep 30, 2021
Pre 1940 USAAF orders, 1 XP-38, 13 YP-38, then 66 aircraft which became 29 P-38, 1 XP-38A, 36 P-38D. The 30 August 1940 P-38 order was for 410 aircraft, built as P-38E, F , F-4, F-4A and F-5A. Another 197 P-38 were ordered on 15 September.
Order A-242 was placed for 667 Lockheed model 322 plus the equivalent of another 133 in spares, 417 for France, 250 for Britain, which became 143 P-322 and the rest built as P-38.
Order A-242 was placed for 667 Lockheed model 322 plus the equivalent of another 133 in spares, 417 for France, 250 for Britain, which became 143 P-322 and the rest built as P-38.
- Thread starter
- #12
Yes, I read that the xp38 was ordered in 1937 and that xf5, from which the xp50 was derived, was ordered around June 1938 with the USAAF ordering the xp50 in 1939. The main point I wanted to explore here was how apparently the engineers at Focke Wulf in 1935 and the engineers at Grumman in 1938 seemed to come up with very similar solutions in their quest for a higher performance fighter of that period. It is reasonable to assume that in both cases, they were giving some thought to the ideas behind these designs before the proposals were put forward.
Alpakinator
Recruit
- 5
- Oct 3, 2023
Hello, I'm new to the forum, and one of the things I'll be trying to do is to gather sources for fixing inaccuracies in War Thunder. Could you provide sources contradicting XP-50 425 mph claims and XP-39 390-400 mph claims? I'd really aprreciate them.
The XP-39 is easy - take a look at pg. 84 to 85 of 'Vee's for victory' book, and especially at the graph at pg. 85 that gives 340 mph at 20000 ft for the 'original airplane [XP-39]'. No wonder, the XP-39 was draggy affair, with Cd0 = 0.0329.
The XP-50 - I have no firm data that it never did 425 mph, however there is also no firm data that it did. As a reality check, we can look at the P-38J, that bested 420 mph mark with 2 x 1600 HP (ie. 2 x 400 HP more than the XP-50 was supposed to have), while without the drag of the R-1820s to act as airbrakes.
added: the figures for the XF5F are even more funny, to be polite - it is/was trumpeted as capable of doing 383 mph at S/L (= faster than a P-47D with water injection and 150 grade fuel - 2800 HP - by about 40 mph), while the USN data sheet gives just above 310 mph at S/L.
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Shortround6
Major General
You forgot the Italians (IMAM RO 57) and quite probably a few other prototypes/projects in other countries (Soviet Union?) .
Using twin engines was not exactly a novel idea. However unless the designers/engineers are very tricky the gain in speed is often not great. One fuselage + one engine nacelle + 2nd engine nacelle is a lot of drag. Do 335 tried to get around that. Several people tried the two engines, one behind the other, like the Italian Macchi M.C. 72 racer. None of those made it past prototype, and some never actually flew.
However in the 1930s governments were cheap, or trying to build as many single engine planes as they could so using up two engines per fighter (and the needed size cost) was a long shot. There was a little bit of interest in trying to use two smaller engines. The XF5F was proposed with two R-1535 engines with two stage superchargers but P & W canceled development of that engine leaving Grumman scrambling for a suitable engine ( fits and won't make the plane fall over on it's nose) and Grumman was stuck with the R-1820 9 cylinder Cyclone with it's barn door frontal area.
Conventional wisdom was that a twin engine fighter was less maneuverable than single engine fighter, heck some people thought that Biplanes still had a place in modern air combat in 1939/40. Some of the early or small twins didn't much different range/endurance than the single engine fighters. They were not designed as long range fighters.
The P-38 was not small, it was designed for twice the endurance of the P-39. This went out the window (sort of) with the requirement for self sealing tanks cut fuel capacity by 25%.
P-39 suffered even worse.
Be careful with US fighters, in the 30s and very early 40s they were given more internal fuel for ferrying than they could use in combat (loading and CG issues) so their range was more strategic (ease of transfer/relocation) than tactical (escort bombers).
- Thread starter
- #16
While this does not answer your question, it might help in better understanding the possibility of the XP-50 as a better than expected aircraft. Firstly, during WWII, pilots flying the P-38 and P-47 encountered the phenomenon of loss of control at high speed. The following is according to Eric Brown. General James Doolittle approached the the research people at Farnborough and asked them if they could determine the problem. In testing they found that the P-38 had a tactical Mach of .68 and a critical Mach of .70 while the P-47 had a tactical Mach of .71 and a critical Mach of .73. Both the FW-190 and the BF-109 had tactical Machs of .75 and critical numbers of .77. Apparently the early models of the Spitfire and the P-51 had tactical Mach numbers in the .73 area and the later models had their tactical numbers at .77 and higher. Secondly, for that era, it is a common rule of thumb that if an aircraft has a high rate of sustained climb and the same for a dive, then that aircraft can generally be expected to outperform other aircraft in many respects. The XP-50 tests did show better climb rates and at least equal dive rates when compared with those of the P-38 at that time.
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- Thread starter
- #17
I think your point about maneuverability is a good one. During the years leading up to WWII most fighter tactic training revolved around horizontal combat, dog-fighting, while the concept and practice of vertical combat (boom and zoom) was looked down upon if not actually discouraged. However it's self evident that if a twin engine fighter can be carefully designed to give high speed capability while carrying a decent weapons array, then it would be ideal for boom and zoom. Another point, the PW R1535 was around 44 inches in diameter and expected to put out 825 HP at take off while the Curtiss R1820 was 54 inches and putting out 1000 HP ATO. It's true the Curtiss weighed 100 lbs more and it's larger diameter would have created greater drag, but the engineers at that time were incorporating the latest refinements in Nacelle design courtesy of NACA and with the extra 175 HP, a reasonably comparable performance could be expected.
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Shortround6
Major General
A lot of planes had trouble with compressibility. However the Mach speed changed with altitude and some of the planes could recover as they got into lower altitude air (and didn't screw up their trim settings trying to get out of the dive before they got into thicker air). P-40s had trouble with compressibility, they just didn't fly high enough to get in the trouble area very often for example.
XP-50 performance is suspect. How much was proved and how much was "estimated"?
I have no idea where the turbo's were located, where if any, intercooler's were located. Or even, for sure, where the oil cooler was located.
On B-17 for instance you can find the turbo, the carb inlet, the intercooler inlet and the oil cooler inlet.
On the XP-50?????
one or two small exit louvers.
- Thread starter
- #19
Perhaps someone might have a reliable diagram of the XP-50 engine system?
Shortround6
Major General
Old thread for the XP-50
a number of photos, including under construction and mock ups and without cowls on the engine/s.
a number of photos, including under construction and mock ups and without cowls on the engine/s.
