AHC: USAAC/AAF 2.0

Since the previous alt-USAAC/AAF thread is too old to continue, and some people can't take a hint, here is another go. Starting with this with XP-39 supposed performance:

...
Not true. The prototype performance speed was 390 mph at operational altitude of 20,000 feet which was 10 mph slower than initial target. The NACA target (Arnold's direct interference here) was 430 mph and was never achieved because the scoop arrangement precluded it. In an attempt to remove boundary turbulence and drag, the scoop was eliminated. Goodbye turbocharger and goodbye HA performance. Kelsey and Saville, the two AAC officers working with Bell objected to that idiocy. Kelsey was transferred to England and Saville shut up and soldiered. Bell was unable to modify the already cramped fuselage interior to wind-tunnel the Allison, so....

340 mph @ 20000 ft for the XP-39 as-is. Thus shipped immediately to NACA, when they did thier job and came out with a host of recomendations to lower the drag, in order to bring the aircraft to either 390 mph at 20000 ft (turbo in conjunction with V-1710) or 400 mph at 13500 ft (gear-driven S/C only). Without guns, protection, radios.

93px.jpg


Whole doc can be accessed here.
So with option a) let's have simple P-39 already in 1941 in production, or option b) wait for Bell to modify the turbo version and have fighters in 1942 in production, Army picked option a.

Lundstrom wrote about EVERY US fighter existent in use in the Pacific up to Midway and into Guadalcanal. That actually includes every active bird in the US fighter line. It also includes many shoddy or outclassed British fighters the Japanese tore to bits like the Spitfire and the Hurricane. Of the fighters in that theater, the best available was the F4F at the time. Slower and not as agile as the Spitfire; it had the virtue of being able to climb and dive well enough and with team tactics was just tough enough to survive Zeros in the hands of an average pilot, which is not true of the other allied planes offered; including the P-40 and the Spitfire. Additionally, while the British used P-40s (and whatever else they could get.) it was not because they did not want the F4F; it was because the USN and Marine Corps had first call on every Grumman made bird during those months. Production was not ramped up to miracle levels until Guadalcanal.

Spitfire was not shoddy nor out-classed in Asia/Pacific.
F4F delivery was 1/7th of P-40 delivered in 1940 and 1941 - 430 vs. 3026. Includes the hopeless versions with 1-stage engines. There was no F4F in 1939 in any unit. P-40 was much faster than Oscar, and barely slower than Zero, while the F4F was slower by 30 mph than Zero and barely faster than Oscar.
F4F did not killed IJN,, let alone IJA on it's own. USA have had Allies with their equipment, radars, exccellent dive bombers in SBD, better multi-engined A/C, teamwork, longer bench, far better & more numerous AAA, damage control, and there were also P-40s and P-38s around. All of those combined killed the Japanese.

This from a gentleman who misstates the development of the P-39? Okay, whatever you wish. But the history of the bird is as I stated, not as you claimed.

Matthews, Birch. Cobra! Bell Aircraft Corporation 1934–1946. Atglen, Pennsylvania: Schiffer Publishing, 1996 pp. 85-87

Post a facsimile of a real test of XP-39 so we can see how actually it was fast.

So explain why it, the Skua is replaced by the Dauntless as soon as the FAA could get some?

From P-36 to Dauntless? Neither SBD, nor Skua, nor Roc, or god forbid Airacuda were capable to solve the USAAC problem of outdated fighters in mid/late 1930s. The P-36 and P-40 solved it in 1939-41.

First; why not teach something as an aside, so that the mistake is not repeated. Second; considering that it takes 6-10 years from aerial concept to flying metal (B-17, an example was designed in 1933, but not op-evaled as ready until 1940-41) what is untrue? The P-51 is the 100 day exception that already was based off the North American and NACA previous research and still took 3 years to finally evolve inti the P-51D

I like the P-51 very much, actually I think it was a mistake that it was not embraced by AAC in a more swift manner. That still does not make it a choice for the Army units in 1939-41 because of non availability.

About how the P-40 was regarded by USN in mid-1942:

...Another aspect of
the attack that proved inadequate was fighter escort. To Fletcher the folding wing F4F-4s
represented no improvement over the fixed-wing F4F-3s, except more F4F-4s could be
carried. He echoed the call of Halsey and others of the urgent necessity'' for detachable fuel
tanks to increase their effective attack radius beyond 175 miles. Spruance and Browning
rated the Grumman Wildcat "greatly inferior'' in comparison with the nimble Japanese
Zero. On 20 June Nimitz relayed their fears to King, noting the "extreme and apparently
increased superiority performance of 0 fighters'' was mitigated only by the vulnerability
of Japanese planes and the superior tactics of the U.S. Navy fighter pilots. "Overall results
have been bad and will be serious and potentially decisive with improvement that must
be expected in enemy tactics.'' Remarkably he called for army Curtiss P-4OF Warhawk
fighters to replace navy F4F Wildcats and Brewster F2A Buffaloes in all marine fighting
squadrons defending forward bases and even asked that the P-4OF "or comparable type"
be tested for carrier suitability
; In the meantime the F4F-4s must be lightened, and their
ammunition supply increased even should that require reverting to four guns in place ofsix.
The swift introduction ofthe Vought F4U-1 Corsair fighter was an"absolute priority.'' Thus
after Midway the top fleet commanders experienced a serious crisis of confidence over the
effectiveness of the basic U.S. carrier fighter, a worry that would soon influence Fletcher's
most controversial command decision...

Lundstrom, Black Shoe carrier Admiral, p.200
 
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Yes, you've told those were expected by 1942. That does not solve AAF fighters issues in 1939-41, the P-36 and P-40 do.
Bell bungled XP-39, the aircraft (340 mph at 20000 ft) was slower unarmed and with turbo than Spitfire I that had no turbo and was armed. The 1st recomedation by NACA was: get rid of turbocharger system, the installation is too draggy. So they did and got a functioning fighter by 1941.

Remember that?

From the quoted citation you made Tomo Pauk and the chart, it plainly reads that it missed its target of 400 MPH; not 340. And in addition:

XP-39 developments
The XP-39 made its maiden flight on 6 April 1938. at Wright Field, Ohio, achieving 390 mph (630 km/h) at 20,000 ft (6,100 m), reaching this altitude in only five minutes. However, the XP-39 was found to be short on performance at altitude. Flight testing had found its top speed at 20,000 feet to be lower than the 400 mph claimed in the original proposal.

As originally specified by Kelsey and Saville, the XP-39 had a turbo-supercharger to augment its high-altitude performance. Bell cooled the turbo with a scoop on the left side of the fuselage. Kelsey wished to shepherd the XP-39 through its early engineering teething troubles, but he was ordered to England. The XP-39 project was handed off to others, and in June 1939 the prototype was ordered by General Henry H. Arnold to be evaluated in NACA wind tunnels to find ways of increasing its speed, by reducing parasitic drag. Tests were carried out, and Bell engineers followed the recommendations of NACA and the Army to reduce drag such that the top speed was increased 16%. NACA wrote, "it is imperative to enclose the supercharger within the airplane with an efficient duct system for cooling the rotor and discharging the cooling air and exhaust gases." In the very tightly planned XP-39, though, there was no internal space left over for the turbo. Using a drag buildup scheme, a number of potential areas of drag reduction were found. NACA concluded that a top speed of 429 mph could be realized with the aerodynamic improvements they had developed and an uprated V-1710 with only a single-stage, single-speed supercharger.

At a pivotal meeting with the USAAC and NACA in August 1939, Larry Bell proposed that the production P-39 aircraft be configured without the turbocharger. Some historians have questioned Bell’s true motivation in reconfiguring the aircraft. The strongest hypothesis is that Bell’s factory didn’t have an active production program and he was desperate for cash flow. Other historians mention that wind tunnel tests made the designers believe the turbocharger installation was so aerodynamically cluttered that it had more disadvantages than advantages.

The Army ordered 12 YP-39s (with only a single-stage, single-speed supercharger) for service evaluation and one YP-39A. After these trials were complete, which resulted in detail changes including deletion of the external radiator, and on advice from NACA, the prototype was modified as the XP-39B; after demonstrating a performance improvement, the 13 YP-39s were completed to this standard, adding two .30 in machine guns to the two existing .50 in guns. Lacking armor or self-sealing fuel tanks, the prototype was one ton (900 kg) lighter than the production fighters.

The production P-39 retained a single-stage, single-speed supercharger with a critical altitude (above which performance declined) of about 12,000 feet (3,660 m). As a result, the aircraft was simpler to produce and maintain. However, the deletion of the turbo destroyed any chance that the P-39 could serve as a medium-high altitude front-line fighter. When deficiencies were noticed in 1940 and 1941, the lack of a turbo made it nearly impossible to improve upon the Airacobra's performance. The cure for the drag problem was worse than the drag itself. In later years, Kelsey expressed regret at not being present to override the decision to eliminate the turbo.

After completing service trials, and originally designated P-45, a first order for 80 aircraft was placed 10 August 1939; the designation reverted to P-39C before deliveries began. After assessing aerial combat conditions in Europe, it was evident that without armor or self-sealing tanks, the 20 production P-39Cs were not suitable for operational use. The remaining 60 machines in the order were built as P-39Ds with armor, self-sealing tanks and enhanced armament. These P-39Ds were the first Airacobras to enter into service with the Army Air Corps units and would be the first ones to see action.

Now then for the other claim: Spitfire vs. Zero.

Again.

No. 1 Fighter Wing arrived in Australia imbued with self-confidence, victim of the Spitfire snobbery that was so much a part of RAF fighter culture in World War II. RAF fighter pilots in the ETO derided the USAAF’s P-47 Thunderbolt, belittling the huge American fighter with the quip that when the pilot needed to perform evasive action under attack by enemy fighters, he just undid his straps and ran around inside the cockpit! This knee-jerk reaction negative impression ignored the P-47’s massively powerful Pratt and Whitney R-2800 engine and its associated turbocharger, which gave the big American machine superior performance in the tactically-critical altitude band above 25 000 feet.

When RAAF Spitfire pilots like Keith ‘Bluey’ Truscott were posted back to Australia for assignment to the RAAF’s newly-formed Kittyhawk squadrons, they similarly dismissed the heavy American fighter. Alongside the P-40’s trickier handling near the ground, Truscott admitted that it had good combat characteristics, but churlishly complained that you couldn’t ‘make it dance’ like a Spitfire. Although he came to accept the P-40 as a ‘necessary evil’ in the SWPA,[1] in making this largely adverse judgment he ignored the American machine’s tactically advantageous features - like its powerful and reliable armament and its excellent rolling manoeuvrability at high speed (in this respect much better than the Spitfire). With all his experience, he should have realised that air combat would not be decided by close-in dogfighting with enemy fighters, whether against the Germans over Europe or against the Japanese over New Guinea. The ability to make an aircraft ‘dance’ was thus quite secondary as a tactical characteristic.

To make matters worse, the Japanese had a fighter aircraft which could ‘dance’ even better than the Spitfire, a fact which was very well known even at the time, and about which the newly-arriving Spitfire pilots were warned. This was established beyond any doubt during comparison trials in August 1943 between one of the RAAF’s Spitfire VCs and a Model 32 Zero that had been captured in New Guinea and rebuilt at Eagle Farm airfield in Brisbane.

The Model 32 Zero, with its squared-off wingtips, was regularly encountered both over Darwin and New Guinea in 1943. Known to the allies by the reporting name ‘Hap’ to distinguish it from the round-wingtipped ‘Zeke’, the Model 32 was an improved model over the original Model 21 with which the Imperial Japanese Navy had fought its 1941-42 air offensives. The chief difference lay in its more powerful Mitsubishi Sakae 21 engine, which developed 1130 hp (as compared with 940 hp in the Model 21). The more powerful engine was heavier, requiring a reduction in fuel capacity from 518 litres to 470, and more thirsty; thus range was less than that of the earlier model. Both the newer and older types were encountered over Darwin.

Nonetheless, it was a Model 32 Zero that was captured and rebuilt, permitting the trials to occur in August 1943. The 1130hp of the Model 32’s Sakae 21 engine was quite comparable to the 1210 hp of the Spitfire’s Merlin 46, but the Model 32’s weight was much less – 5155 lb compared to the Spitfire’s 6883 lbs. As a result of this structural lightness, the Zero had both a superior power loading (4.5 lb/hp versus 5.6 lb/hp) and a lower wing loading (22 lb/ft2 versus 28 lb/ft2).

These differing technical characteristics determined the pattern of relative performance between the two machines, as shown by the tactical trials conducted by two experienced RAAF fighter pilots in flying trials conducted over three flying days[2]. Flight Lieutenant ‘Bardie’ Wawn DFC and Squadron Leader Les Jackson DFC flew against one another in both aircraft, and what they found was not encouraging.

They found that the Zero had a lower rated altitude than the Spitfire, 16 000 feet against 21 000 feet, which delivered the Spitfire a good speed advantage at height – it was 20 knots faster at 26 000 feet. However, as had already been noted by RAF Fighter Command in Europe, the Spitfire had relatively slow acceleration, and thus the Zero was able to stay behind the Spitfire within gun range while the Spitfire gradually accelerated away out of range. Even in a dive the Spitfire still accelerated too slowly to avoid the Zero’s gunfire. Climbing away was also not an option, as the Spitfire’s climb superiority was too slight (not to mention the slow acceleration problem once again).

The only offensive solution for the Spitfire was to attack from a height advantage, to maintain a high IAS on the firing pass, to fight on the dive and zoom, and to pull high speed G. Slowing down, or being caught while flying slowly, would clearly be very dangerous, for the Spitfire would be unable to evade. Above 20 000 feet, so long as the Spitfire started with a 3-4000 feet height advantage, the Spitfire could make dive and zoom attacks with impunity.

The height advantage of the Spitfire VC was also shown by the British machine’s superior operational ceiling. Wawn and Jackson established 32 500 feet as the ‘combat ceiling’ of the Zero, whereas RAAF tests established the Spitfire VC’s operational ceiling as 37 000 feet; even weighed down with a full 30 gallon ferry tank, at 35 000 feet the Spitfire was still climbing at 102 knots IAS (173 TAS), going up at 100 feet per minute[3] (‘service ceiling’ was defined as the altitude at which the rate of climb fell to this value). The superiority of the Spitfire’s ceiling is corroborated by its 5000 feet higher rated altitude, by 1 Fighter Wing’s demonstrated tactical employment of the Spitfire at heights up to 33 500 feet, and by the Zero pilots’ avoidance of the height band above 30 000. The pattern established in these tests confirmed the findings of operational experience over Darwin, where the Spitfires were always able to dominate the upper height band without Japanese challenge.

The Zero developed its maximum speed of 291 knots at its rated altitude of 16 000 feet. The Spitfire produced 290 knots at 15 000 feet, confirming that below 20 000 feet the two types were more evenly matched in speed performance. Given the Zero’s much superior acceleration, in practice this meant that the advantage tipped more heavily in favour of the Zero at these lower altitudes. In comparative tests at 17 000 feet, the Spitfire was again unable to safely draw away from the Zero. The unanimous conclusion of Wawn and Jackson was that ‘the Spitfire is outclassed by the Hap at all heights up to 20,000 feet’.

As was already well known, the Zero had all the advantages in combat manoeuvrability at slower speeds. This was a product of the Japanese machine’s superior power loading and lower wing loading. The Zero stalled at only 55 knots, whereas in clean configuration the Spitfire stalled at 73. Being able to fly more slowly while still under complete control meant the Zero could fly tighter turns without stalling out. The stall speeds cited apply to straight and level flight at 1G – hardly a realistic scenario in combat, where pilots would typically stall out of accelerated turns. In a modest 3G turn, the Spitfire would stall at 130 knots IAS, which equates to a TAS of 242 knots at 20 000 feet. At 6G (a hard turn or pull out at high speed, with the pilot blacking out), the Spitfire stalled at 184 knots IAS, which equated to 257 knots TAS at 20 000 feet, and 294 knots at 30 000. The latter was only 11 knots less than the Spitfire’s maximum speed at that height (at the emergency power settings of 3000 rpm and plus 2 ½ pounds boost), so it is clear that as height increased, the pilot found himself stuck in an increasingly narrow corner of the flight envelope, until any attempt to pull G would result in an instant high speed stall. This helps to explain the high incidence of Spitfires stalling and spinning out of combat turns over Darwin in 1943.

Spitfire VC Stalling Speeds[4] (see table at citation)

By contrast, the Zero’s lighter weight meant that it would always be superior in all tight manoeuvres. Obviously, the Zero also stalled out under G, but the tests showed it to have superb handling characteristics in hard turns, with no tendency to spin out of high speed stalls (implying that it was superior to the Spitfire in this respect). Although Spitfires endeared themselves to pilots by their sweet flying qualities, it is clear that the Zero too had impeccable manners.

If a Spitfire followed a Zero around in a loop, it would stall out at the top, and could only stay behind the Zero for ¾ of a horizontal turn. In short, it was too easy for a Zero to evade a Spitfire at medium altitudes and below, by simply performing any vertical manoeuvre or hard turn. This meant it would be very difficult for a Spitfire to get a shot at a manoeuvring Zero. The only practical firing opportunity for Spitfire pilots would come in a bounce.

Neither aircraft had a good roll rate at high speed, due to their ailerons locking almost solid in the airflow. However, in this respect the Zero was even worse than the Spitfire, which permitted a glimmer of encouragement for the Spitfire pilot: the Zero could not get into a firing position behind the Spitfire if the latter evaded in diving aileron turns at high speed. Other than the downward break, no other evasive manoeuvre by the Spitfire was likely to work, although a vertically-banked climbing turn was difficult for the Zero to follow. Otherwise, the Zero could follow the Spitfire through any manoeuvre below 220 knots, and could use its slow turning advantage to get onto the Spitfire’s tail after 2 ½ hard turns.

It was only at higher speeds that the Spitfire started to enjoy a relative advantage. Because the Zero’s controls stiffened up even more rapidly than the Spitfire’s, the Zero had great difficulty in following the Spitfire through high speed manoeuvres where the pilot pulled a lot of G. From about 290 knots, the Zero had great difficulty following the Spitfire through diving aileron rolls. The conclusion was that the Spitfire was more manoeuvrable above 220 knots, while the Zero was the better below that speed. Reflecting this set of opposite characteristics was the fact that the Zero’s standard evasive manoeuvre was the very opposite to that of the Spitfire – upwards rather than downwards, in the form either of a climbing turn or a vertical aerobatic manoeuvre like a loop, stall turn or Immelmann.

Overall, the summary from the comparative trials was not encouraging:

'Both pilots consider the Spitfire is outclassed by the Hap at all heights up to 20 000 feet…The Spitfire does not possess any outstanding qualifications which permit it to gain an advantage over the Hap in equal circumstances.'[5]

The conclusions of Wawn and Jackson only corroborated the earlier evaluation conducted by 1 Fighter Wing HQ[6] after combat experience over Darwin, which found that the Spitfire had a higher maximum speed, that it was more manoeuvrable at high speed, and that it could be dived to a greater speed. It followed that the only sensible offensive tactics were the dive from height followed by a zoom climb for a re-attack. The recommended evasive tactic when under attack was to break downwards into a vertical dive at full power, while yawing the aircraft violently by uncoordinated use of the rudder and/or ailerons to put the Zero pilot off his aim. Once the speed had built up (presumably 300 knots), the pilot should start rolling into downward aileron turns to obtain a clean separation from the Zero.

Rightfully, a whole generation of pilots learned to treasure the Spitfire for its delightful response to aerobatic manoeuvres and its handiness as a dogfighter. However, it is odd that they had continued to esteem these qualities over those of other fighters in spite of the fact that they were of only secondary importance tactically. As the Germans had showed the RAF fighter squadrons, the most decisive superiority in fighter combat came through some combination of height, speed, and firepower, not tight turning or manoeuvrability. Thus it is doubly ironic that the Spitfire’s reputation would habitually be established by reference to archaic, non-tactical criteria, and that the new Japanese opponent would trump every one of the Spitfire’s purported trademark virtues: in effect, ‘whatever you can do, I can do better’.

Read more at the citation.

USA have had Allies with their equipment, radars, exccellent dive bombers in SBD, better multi-engined A/C, teamwork, longer bench, far better & more numerous AAA, damage control, and there were also P-40s and P-38s around. All of those combined killed the Japanese.

In the only area where it mattered for the British...

On 26 March 1945, in a last action near Trondheim, during Operation Prefix, Wildcat VI's from 882 Squadron (Acting Lieut Comdr RA Bird RN) off Searcher, escorting a flight of HMS Queen’s 853 Squadron (Lieut Comdr JM Glaser, RN) Avengers along the coast, were jumped by a flight of eight III Gruppe JG 5 Me 109Gs. The Wildcats pilots claimed three of the Me 109Gs shot down and two damaged at a cost of one Wildcat damaged. Bird, who had previously shared in two victories with 881 Squadron (as noted above, ½ credit for a Potez 63 on 6 May 42 near Diego Suarez operating off Illustrious and ½ credit for a BV 138 on 8 July 1943 while operating off Furious), was credited with one 109 shot down and one damaged. This brought Bird’s wartime total to 2 victory credits and 2 for credits for damaged aircraft. Also credited individually for downing a 109 in this action was Sub-Lieut AF Womack. Sub-Lieut’s JAP Harrison and RF Moore split an additional credit for one more 109 plus and Harrison claimed an additional damaged. Credits appear to match losses in this action. As near as can be determined from available Luftwaffe loss lists, there were indeed three 109’s lost: #412398 (Fw Jaeger), #782139 (Uffz Rösch), and #782270 (Fw Dreisbach). Rösch and Dreisbach were rescued; Jaeger, who had survived an earlier crash on 16 February, was killed when his plane went down. One other 109 crashed, (pilot unknown) on landing, however the information available does not indicate if the crash was due to pilot error or from battle damage; damage to this plane was evaluated as 25%. Available Luftwaffe credits lists show no claims from this action.

Historically as far as tearing the guts of Japanese aviation out, the biggest single killer was the F6F Hellcat with ~ 5,130 victories. As for kills per type of the 3 best US aircraft in the war by tally:

P-51 ==> 5,954 all theaters but mainly ETO.
F6F ===> 5,135 mainly Pacific
P-38 ==> 3,785 mainly Pacific

As for US air to air kills, the USN leading theater was the Pacific; 12,666
For the USAAF it was the ATO: 13,623 broken down between heavy bombers; 6,098, medium bombers; 108 and fighters 7,422

In the ETO, it can be argued that the RAF is the primary killer until 1944, after which it is the USAAF. Overall war totals when summed up; about 50/50.
German losses were ~ 78,000 lost through use,

Shot down or lost to enemy action (German records);

21,452 single engine fighters
12,037 bombers
15,428 trainers
10,221 twin-engine fighters
5,548 ground attack
6,733 reconnaissance
6,141 transports

Curiously the ground attack and recon birds are concentrated in two theaters by loss, the eastern front and in the Med. Most of the single engine fighters and twins are killed in the air defense battles over France and metro Germany. Bombers are everywhere. Trainers are in the east! Transports seem to be east front predominant too.

Ellis, John (1993). World War II - A statistical survey. Facts on File. p. 258. ISBN 0-8160-2971-7

In the Pacific, Japan lost somewhere between 50,000 - 60,000 aircraft with ~ 19,000 -20,000 shot down. Their records are incomplete and lousy.

The Russians are horrible;

17,900 bombers shot down,
23,600 ground attack (mainly Sturmoviks),
46,800 fighter aircraft of all types, and
18,100 other types splashed

But on top of combat losses over 60,000 were wrecked by "operational use".

Krivosheev, G. I. (1997). Soviet Casualties and Combat Losses. Greenhill. pp. 255, 258, 259. ISBN 1-85367-280-7.

And I thought their tank forces were slaughtered!


Ellis again p. 259

Main effort and cause for Japanese air losses in the Pacific was the United States Navy which is not surprising since USN AAA accounted for some 3,700 kamikazes and attack aircraft as well as those planes its fighter forces downed.

Finally, Browning was a no-good drunken incompetent staffer who did not even know the operational characteristics of USN aircraft as he proved at Midway with his botched flight op orders and Spruance did not fly (He finally overruled Browning by talking to the pilots directly.) How the hell are these two supposed to know aircraft characteristics or make judgments? At least Spruance finally talked to his aviators. The criticism of the 6 gun F4s after Midway was valid and it was the pilots who told Fletcher and Spruance about it. The admirals did not have first hand flying experience.

P-40s would never be carrier suitable. Too fragile and their engines unsuitable.

In the meantime the F4F-4s must be lightened, and their ammunition supply increased even should that require reverting to four guns in place ofsix.
The swift introduction of the Vought F4U-1 Corsair fighter was an "absolute priority''.


The F4U had teething troubles; mainly stall spins and left wing drop in landing attempts. The plane bounced during a trap or a landing and the pilot could not see coming down on the wires or touching down on a landing strip. The Pratt blew oil onto the windscreen when the cowl flaps were opened. Perfect plane for the Marines! The British are credited with its carrier use, but the USN worked out the kinks on the Great Lakes independent of the British and carrier-qualed it by mid-43, same time as the British figured out the bird. The Marines flew it for a year, before it reached the fleet's flattops by late 43 early 44. They had more need. (Solomon Islands.)
 
Remember that?

From the quoted citation you made Tomo Pauk and the chart, it plainly reads that it missed its target of 400 MPH; not 340. And in addition:

I remember, no worries - the XP 39 was good for 340 mph (the 'Original airplane' line in the graph), was immediately shipped to NACA, where they tested it and concluded that it will be going much faster once the steps are carried out. One option (line named 'Modified airplane with supercharged engine' in the graph) will retain turbo, but it will be harder to pull than another option (line named 'Modified airplane with altitude blower') will be easier to pull, sacrificing the hi-alt speed. The non turbo option was choosen, thus XP-39B sans turbo, YP-39s and P-39C.
The XP-39 with drag coefficient of 0.0329, even draggier than the radial-engined XF4-F3 with 0.0269, or as draggy as the Douglas XBT-2: NACA report
Barely less draggy than the biplane F3F-2.

I reckon it that you don't have facsimiles of test reports that will put XP-39, as-is, making 390 mph.

Now then for the other claim: Spitfire vs. Zero.
Again.
Read more at the citation.
In the only area where it mattered for the British...

The articles number the good and bad points of each fighter, making recomendations and conclusions. Eg: "To summarize, in view of the whole circumstances surrounding the brief engagement, and despite the fact that both height and numbers favored the Zekes, I regard the Spitfire as a superior aircraft generally, though less maneuverable at low speeds. In straight and level flight and in dives the Spitfire appears faster." from Caldwell. Or, advices to keep the height and speed up, dive, make firing pass, zoom climb, repeat - same as any Allied recepy to combat Japanese.

Finally, Browning was a no-good drunken incompetent staffer who did not even know the operational characteristics of USN aircraft as he proved at Midway with his botched flight op orders and Spruance did not fly (He finally overruled Browning by talking to the pilots directly.) How the hell are these two supposed to know aircraft characteristics or make judgments? At least Spruance finally talked to his aviators. The criticism of the 6 gun F4s after Midway was valid and it was the pilots who told Fletcher and Spruance about it. The admirals did not have first hand flying experience.

P-40s would never be carrier suitable. Too fragile and their engines unsuitable.

The passage I've quoted shows that USN was not satisfied with F4F.
 
Tomo,

Had not seen this topic earlier. My first professional employer after college was Princeton prof., aero textbook author and literally lifelong mentor and friend, Daniel O. Dommasch. In the late forties, Dan was employed by Bell Aircraft in their helicopter development program and after hours worked with Tex Johnson and Bob Woolams in the "Skyways Unlimited" Thompson Trophy air race project. Two Airacobras were extensively modified (Dan did the propeller analysis and integration) and one won the 1946 race. Later, it demonstrated the fastest closed course speed at Cleveland, far in excess of both P-51s and SuperCorsairs, despite the thick wing. Many lunch hour conversations were devoted to the P-39 and its undeveloped potential. No time today to get into details, but think about how the rear mounted engine could have exhaust augmented a Meredith radiator installation in the rear fuselage.

Dynasoar
 
Tomo,

Had not seen this topic earlier. My first professional employer after college was Princeton prof., aero textbook author and literally lifelong mentor and friend, Daniel O. Dommasch. In the late forties, Dan was employed by Bell Aircraft in their helicopter development program and after hours worked with Tex Johnson and Bob Woolams in the "Skyways Unlimited" Thompson Trophy air race project. Two Airacobras were extensively modified (Dan did the propeller analysis and integration) and one won the 1946 race. Later, it demonstrated the fastest closed course speed at Cleveland, far in excess of both P-51s and SuperCorsairs, despite the thick wing. Many lunch hour conversations were devoted to the P-39 and its undeveloped potential. No time today to get into details, but think about how the rear mounted engine could have exhaust augmented a Meredith radiator installation in the rear fuselage.

Dynasoar

Goes without saying that I'm all ears for the juicy details on those particular P-39s (and P-39s in general), granted the 'Vee's for victory' does cover them a bit.
BTW - the P-39s were with thinner wing than P-51s, let alone the F4Us. The P-39s were ones of the sleekest fighters of ww2.

I got so excited when I saw this thread. Thought it was going to be about the USAAF surviving to modern day.

Sorry for disapointment. I have no problems with anyone making that timeline.
 
The P-39. With the available technology of the time I believe a liquid cooled based intercooler should have been developed to fit into that compact airframe. This is not so different from the liquid cooled aftercooler system used on the two stage supercharger Merlins in the P-51. In the ducting between the turbo-supercharger and the carburettor the liquid fed heat exchanger is installed. The tubing from the heat exchanger is run to a small radiator on the inside of the fuselage just behind the engine. A small duct and rear exit flap completes the installation. By adjusting the exit flap and possibly the electric coolant pump speed it will regulate the compressed air temperature.

A little more complex and slightly more heavy than the air cooled intercooler but much less bulky and much less draggy. Perfect for the Airacobra. Now pull the 4 .30s from the wings to permit an increase in the wing fuel tankage. Replace the 37mm with a HS 20mm cannon and you have a first rate high altitude interceptor.
 
Draconis,

Agree that "with the available technology of the time" a dual heat exchanger installation with pumped liquid circulating between them at an intermediate temperature could transfer heat as well as a crossflow air to air system, and with flexibility of component location, possibly at lower drag. The use of counterflow, where the two air flows pass thru a heat exchanger in opposite directions (with no temperature averaging) offers much less exchanger volume (less pressure drop in induction system and less drag on ambient side) for a given rate of heat rejection. The use of a phase change heat transport fluid (as discussed in earlier posts) would isolate each flow-wise increment of the system at maximum delta T (and minimum air pressure drop). The technology existed in the thirties but found broad application in low temperature difference systems for cooling electronics in the sixties and seventies.

Dynasoar
 
@Dynasoar could you describe what the phase change system would look like if it was installed in a !940s type WW2 aircraft application? It sounds promising but I'm having trouble visualizing it.
 
Draconis,

A phase change intercooler would work this way: Imagine a common tube and fin air conditioner condenser heat exchanger. Copper tubes would be horizontal, penetrating perpendicular, vertical aluminum fins. If there was only one row of tubes, they would be connected in vertical serpentine fashion with 180 degree return bends at each end. Typically there could be as many as six horizontal rows of tubes in the direction of air flow (since the condensing refrigerant is at constant temperature (a saturated gas condensing to liquid), more tubing rows would not be effective. Typically, hot refrigerant vapor would enter the HE at the rearmost row (in the direction of cooling air flow) and the condensed liquid would exit from the entering face row. Now for the intercooler.

For simplicity imagine a one row heat exchanger with the horizontal tubing in an ascending serpentine as described above, with the tubing half filled with liquid refrigerant and sealed. Now turn the HE 90 degrees so the tubing runs are vertical. If the top and bottom halves are baffled so separate air flows are impressed on each half, and the airflow through the bottom section is heated, this heat will be rejected to the air flowing through the upper section fins.

The refrigerant in each bottom"U", boils and the saturated vapor rises to condense on the inner wall of the upper U. The condensate returns by gravity and internal surface wicking. Since the condensate is at least two orders of magnitude denser than the vapor, depending on heat input, vertical internal gas flow velocity can increase to approach local sonic. The copper tubes are entirely isothermal.

Now imagine the following: The conductive isothermal tubes, instead of being round in cross section, are oval and as many tubing rows as desired can be added in the direction of airflow (which is opposite in the top and bottom sections). Since each tube row operates at its own temperature (true counterflow) each row is as efficient as any other, so HE optimization is simple. The entire system is much lighter, smaller, requires no pumps and will demonstrate much lower pressure drop (as a "radiator" and as an obstacle in the induction system)

I would expect the package would fit right behind the Airacobra canopy, ahead of the turbo.

Dynasoar.
 
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Perhaps we should 'nudge' Seversky company in designing the P-43 around turboed V-1710 instead of the R-1830? They have gotten the layout right - engine -> pilot -> turbo.
 
Gentlemen,

Somewhere in my archives I've got drawings of Bell fighter projects prior to the P-39 we're familiar with. As I recall, one of them details the original cannon fighter with the forward engine and another shows the earliest mid-engine configuration, both with turbochargers and both with the roll down canopy access, like the later XP-77. I'll look for them today. Will also sketch the proposed counterflow intercooler.

Dynasoar
 
The Soviet no-nonsense 2-engined fighter that perhaps the US would've been even better in producing. Two radials (1100 CV at 6 km each), four 20 mm cannons + 2 LMGs (US might be using 6-8 .50s instead), almost 600 km/h (~375 mph). Size comparison os between the OKO-6(bis), Pe-3 and Bf 110. US version might also use the V-1710, with or without turbo. A better canopy will be nice, though.

oko.jpg
 
A little bit on the heart of an aircraft - it's engine. Let's say that USAAC brass realizes the folly of the 'hi-perf' engines much earlier than it was historically so, and make a tour around the engine makers. End result being the R-2600, R-2180A and V-1710 designs getting finnancial support from, say, 1936 on. Hi-perf engines cancelled, no R-2000, no Wright Tornado, no V-3420. Hopefully this will shave 1/2 a year from the development period of the P&W and Allison. The 1938 sees the XP-40 (V-1710) and Seversky XP-43 (R-2180A + turbo) as winners of new fighters competition.
For production engines, the V-1710 gets a variable-speed drive for the S/C in mid-1941, and a 2-stage version in late 1942. P-40 and P-51 as obvious recipients.
No Airacuda, no P-39, Bell produces a no-nonsense classic twin-engined fighter, powered by non-turbo V-1710 (R-2180 as option), later it becames a night fighter and fighter-bomber. Lockheed makes also a classic twin, turboed V-1710s as powerplant.
 
I'll continue the discussion here, in order not to clog the excellent thread with off-topic stuff.

You forget the intercooler and the pump?
and with the gewgaws:

Maintenance manual... https://aviationshoppe.com/manuals/...tenance_manual/r-1830_maintenance_manual.html

Intercooler on a 1-stage supercharged R-1830. Please, don't make me angry. There was no intecooled 1-stage radial engine in service anywhere. Pump? For what?

Bristol is not RR. Neither is Napier. Their aspiration schemes were at least as good as Curtiss Wright's.

There is no award for being 10th or 13th in something. Napier didn't fly anywhere a 2-stage supercharged engine, Bristol did not in ww2. They did in inter-war period, while Wright 2-stage engine powered the Hellcat prototype (1700 HP will not cut it on the big & heavy fighter), and their turboed engines worked.

Production run is finished (~150 planes) tool jigs are gone. Engine swapout (weight) is not simple. Mods expensive. New TBM on the way. Better suggestion.

N3PB
Developed from:
A-17 (Northrop)
Or
A-33 (Northrop designed for Douglas)

Those three planes are in production, they are in order the Norwegian N3PB torpedo bomber seaplane with a cruise of 160 knots (294 kmh) and endurance of 4 hours at cruise which gives it DOUBLE the strike reach of a Devastator at 30% greater drop speed. This requires some changes in USN doctrine though as the extra fuel is carried in the floats.
The A-17 and A-33 have similar performance to the N3PB but are DIVE BOMBERS and only 2.5 hours endurance in the air at cruise. Their reach is therefore as short as the Devastator. Also they would have trouble carrying a metric ton (tonne) bomb-load so a Mark XIII would be kind of awkward. But in a pinch, already built dive bomber tough, with arrestor gear, they'll do.

Expensive? A 1-engined A/C? Please, spare me of those jokes. How much it will take for the N3PB to acquire retracting U/C?
The Mk 13 torpedo is 2000 lb. The A-33 can't take off with it, let alone the A-17, that is before we contemplate taking off from a carrier. Drop speed is dictated by torpedo, not by aircraft.
Why moving the goal post with alternative dive bomber?

P-47N was an end of run, more expensive than the P-51. And it took Kartvelli four tries to get to that Jug. This tortured path started with the P-35 which was okay (Engendered the Reggiane line of Re-2000 series as a byproduct) but needed replacement urgently by 1939. The first attempt was the XP-41 (Seversky with Kartvelli) which went nowhere fast when the army bought into Kartvelli's P-43 Lancer. That plane came out of the Severski AP1-AP9 line of development off the basic P-35 airframe, which is why his name keeps popping up. The Lancer had no armor and its gun armament was a catastrophe, but aside from those faults and short range it was a good airplane for 1937, though made in 1941.

Enter the P-47. This plane had armor, a good gun pack and four hours in the air at cruise. From D to N took SIX iterations to get all the bugs out. By 1945 it, as the N, could escort Superforts from Iwo to Tokyo (double time from D model) and back, but so what? At $87,000 a copy? The P-51 at $55,000 a copy could do the same and was a better dogfighter.

Four tries? There was no R-2000 in 1937 when the P-35 was mooted, nor the turbo was mature enough. That already the P-47C did not have enough of range is fault of USAAC for not ordering it with wing racks from get-go. The P-47D was the 1st Allied fighter that was able to fly to Lubeck, Germany, in daylight and beat whatever LW could've thrown at them, by Autumn of 1943. By mid-1944, it was good for 600 miles of combat radius. P-47N was good for 1000-1300 mile radius, not range (link), the P-51D for 700-850 miles.



Yeah, too bad. It would have helped in the lean years to have the P-38 (another option was Pratt and Whitney radials, lose maybe 10% speed but gain in engine reliability and range) ready to beat up on the Axis when a "forked tailed devil" would have been the RX.

But that carries us away from the Mark XIII torpedo and delivery options for it. The Devastator was a no-go after 1939. Three options (all Jack Northrop designs) existed as plug-ins before Grumman delivers her baby. Which one do you like?

The R-1830 on P-38 will make it slower. The R-2000 is too late, and still no advantage. R-2800 is too big & heavy, not a drop-in replacement for the V-1710. Running late and problems with aerodynamics were more pressing problems than engines (though those could use tweaking a lot). R-2180A? That might be interesting.
Devastator with better engine makes plenty of sense if the bugs are rooted from Mk 13. Otherwise, go all-out with dive bombers for the USN CVs. I'm not fond on any proposal of the three as replacements for the Devastator.
 
I'll continue the discussion here, in order not to clog the excellent thread with off-topic stuff.

Intercooler on a 1-stage supercharged R-1830. Please, don't make me angry. There was no intecooled 1-stage radial engine in service anywhere. Pump? For what?

Pratt_1830.png


s no award for being 10th or 13th in something. Napier didn't fly anywhere a 2-stage supercharged engine, Bristol did not in ww2. They did in inter-war period, while Wright 2-stage engine powered the Hellcat prototype (1700 HP will not cut it on the big & heavy fighter), and their turboed engines worked.

What did I say about aspiration? See below.

Expensive? A 1-engined A/C? Please, spare me of those jokes. How much it will take for the N3PB to acquire retracting U/C?

An entire defunct production line reconstituted to build and or re-jig just 150 aircraft? You better believe that is expensive. Ever hear of the Super Hornet?

The Mk 13 torpedo is 2000 lb. The A-33 can't take off with it, let alone the A-17, that is before we contemplate taking off from a carrier. Drop speed is dictated by torpedo, not by aircraft.

Both could lug 1800 pounds aloft. 200 pounds added (the Mark XIII and the 200 pound safety pad is doable with a C-4 catapult.)

Why moving the goal post with alternative dive bomber?

1. The "dive bombers" already have tough enough airframes to handle carrier abuse. Army planes of the era had a 1.4 burden rating so the safety pad is in, though not ideal.
2. I'm getting rid of the tail gunner and pop gun. There's your torpedo loft.
3. The N3PB doesn't lose its floats. Why delete gas tanks from a cruiser float plane? I suggested the USN might have to change its doctrine (and some equipment) a bit. Four cruisers + four float planes = torpedo/scout squadron. Not every Japanese idea was crazy.

Four tries? There was no R-2000 in 1937 when the P-35 was mooted, nor the turbo was mature enough. That already the P-47C did not have enough of range is fault of USAAC for not ordering it with wing racks from get-go. The P-47D was the 1st Allied fighter that was able to fly to Lubeck, Germany, in daylight and beat whatever LW could've thrown at them, by Autumn of 1943. By mid-1944, it was good for 600 miles of combat radius. P-47N was good for 1000-1300 mile radius, not range (link), the P-51D for 700-850 miles.

P-35, P-41, P-43, P-47. P-47 C-N (rearrange the fuel tanks, fix the guns jam problem, fix the port stall, fix the canopy, replumb the drop tank lines, fix the canopy again).

And if the P-47 was so good, why was the P-51 kept on and the P-47 retired? (See below).

As for the Regianne 2000, the guys who designed that air frame before the war worked for...

Seversky on the P-35.

Hours endurance not "range".

P-47N performance test results.

Just one little tidbit.

H. Longitudinal stability of the P-47N decreases with an increase in altitude and becomes objectional at high altitudes.

For a high altitude escort that is a bolo.

The R-1830 on P-38 will make it slower. The R-2000 is too late, and still no advantage. R-2800 is too big & heavy, not a drop-in replacement for the V-1710. Running late and problems with aerodynamics were more pressing problems than engines (though those could use tweaking a lot). R-2180A? That might be interesting.

Devastator with better engine makes plenty of sense if the bugs are rooted from Mk 13. Otherwise, go all-out with dive bombers for the USN CVs. I'm not fond on any proposal of the three as replacements for the Devastator.

Unless that is a Twin Hornet, forget the Pratt R-2180. I might opt for the Yellow Jacket.

Three choices, and a doctrine change...

Jack Northrop was a good solid engineer. Given the existing US choices and the need for an interim 1200 HP (900 Kw) engined aircraft speculated with a drop speed requirement of 300 kmh at 500 meters for the fragile Mark XIII torpedo, the best is the N3PB. Second best is the A-17. Those are the best two candidates for a torpedo lugger. I think the A-33 has a too serious thick air vibration problem. (wing flutter).

Heck; if I could figure out a way to put a torpedo under a Dauntless, don't you think I would have?
 
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Again - there was no such thing as intercooler (or aftercooler, or whatever you call it) on a 1-stage supercharged radial in ww2 or before. Nor there was an intercooler/aftercooler on a 1-stage S/Ced V12 in ww2 and before, bar one or two versions of Jumo 211 (J and ??)
The 2-stage supercharged versions of R-1830, R-2800 and R-2600 were with intercooler, that was located between the supercharging stages. Merlin introduced intercooler with 60 series, it was located between 2nd S/C stage and cylinders. Allison V-1710 was with intercooler only in turbo versions on the P-38 in service, while 1- and 2-stage versions were without intercooler.
If you are going to post pictures that are supposed to prove your point, the vague gaphics from 21st century aren't helping.
If you don't believe me, register and post at ww2aircraft.net or at http://www.enginehistory.org/ and ask there. Or drop a question to https://oldmachinepress.com/.

What did I say about aspiration? See below.

I'm sorry. Your track record about the 1930s-40s aviation techicallities is not something to boast around.

An entire production line reconstituted to build and or re-jig just 150 aircraft? You better believe that is expensive. Ever hear of the Super Hornet?

Super Hornet got new wing and LERX, extra part of fuselage, new tail, electronics, new intakes. Not the things I've suggested for the uprated Devastator.

Both could lug 1800 pounds aloft. 200 pounds added (the Mark XIII and the 200 pound safety pad is doable with a C-4 catapult.)

1. The "dive bombers" already have tough enough airframes to handle carrier abuse. Army planes of the era had a 1.4 burden rating so the safety pad is in, though not ideal.
2. I'm getting rid of the tail gunner and pop gun. There's your torpedo loft.
3. The N3PB doesn't lose its floats. Why delete gas tanks from a cruiser float plane? I suggested the USN might have to change its doctrine (and some equipment) a bit. Four cruisers + four float planes = torpedo/scout squadron. Not every Japanese idea was crazy.

It is one thing to make a maneuver at high G, another thing is to try to take-off with a 2000 lb torpedo with aircraft that was rated for 1600 lb of external load. The big wing on Devastator, Kate, Avenger or Albacore was there for reason - big payload needs a lot of lift.
You can get rid of the tail gunner in the Devastator if that is such a great idea (don't think it is). A-17 was rated for total bomb load of 1200 lbs. Please, post correct figures if you want to be taken serious.
The N3PB with floats will not replace any CV bomber, without going into the merits of the proposal.

Hours endurance not "range".
P-47N performance test results.
Just one little tidbit.H. Longitudinal stability of the P-47N decreases with an increase in altitude and becomes objectional at high altitudes.For a high altitude escort that is a bolo.

I know that hours of endurance is one thing, range is another.
P-47N got the dorsal fin to cure the problem, just like DH Hornet, P-47D or P-51D.

Unless that is a Twin Hornet, forget the Pratt R-2180. I might opt for the Yellow Jacket.

Jack Northrop was a good solid engineer. Given the existing US choices and the need for an interim 1200 HP (900 Kw) engined aircraft speculated with a drop speed requirement of 300 kmh at 500 meters for the fragile Mark XIII torpedo, the best is the N3PB. Second best is the A-17. Those are the best two candidates for a torpedo lugger. I think the A-33 has a too serious thick air vibration problem.

R2180A was the Twin Hornet, the post-war R-2180E was also called Twin Wasp (along with R-1830 and R-2000).
A-17 will not cut it, the N3PB is no-go for carriers.
 
Tomo, Thank you for reactivating this thread. I had an interesting paleo front engine P-39 drawing ready for submission several weeks ago, but it since has submerged in my clutter. Will look for it again.

About your statement that there were no inter (after) cooled radials during WW2, the "one stage" referring to the close coupled integral engine blower, makes it correct. Frankly, I don't see any entirely practical way to insert heat exchangers into the usual
short intake manifolding tho, if necessary it could certainly be done.. Plenty of turboed radials had intercoolers; B-17, B-24 etc. but they were two stage engines.

Thanks too, for introducing me to NASA TN D-8206. More about this later.

Dynasoar
 
Gentlemen,

Some interesting near direct all-out performance comparisons between WW2 aircraft can be extracted from the results of immediate post war air races- both at sea level (Thompson trophy)and over 2000 miles (Bendix trophy) between 1946 and 1949.

In summary, at sea level over a closed course of 20 miles with 180 degree relatively high g turns at each end, in 1948 a P-39C recorded 418 MPH, with the fastest P-51 at 398. Over the same course a Spitfire XIV ran 360 MPH. In 1949 a much modified P-51C, with wingtip ramjet configured radiators (Sponsored by Walter Beech and Jackie Cochran) qualified at 408. This beautiful "hot rod" was timed at an airshow a few months before, for a four run average over a surveyed one mile course, at 502 MPH.

The 2000 mile Bendix race is more difficult to analyse with the data available to me not distinguishing between non-stop and refueled flights or winds aloft on different years. If there is interest, I'll try to dig this out. The best speeds for different aircraft are P-51C (converted to wet wing for non-stop flight) 470MPH; Lockheed F-5G, 370 MPH; Douglas A-26C, 368 MPH; Bell P-63C, 367 MPH; Mosquito 25, 344 MPH. Suspect that the Lockheed and the Bell made one stop while the others covered the 2000 miles non-stop. (edit) A half hour delay for fuel would have the Lockheed at 408 MPH and the Bell at about 404.

Dynasoar.
 
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