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Kevin J
Banned
The Spitfire V was the first Spitfire operated everywhere before it's opponents withdrew beyond their reach. Forget the rest.
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Let me put it this way:
- The number of aircraft built does not directly correlate with the number of aircraft in combat units. The more you build, the more you can have in combat units, but not all go to those units.
- The number of aircraft in combat units does not directly correlate with the number of sorties. Some units will have higher sortie rates than others, based on their role, location, weather and, doubtless, other factors.
- The number of sorties does not correlate with the frequency of encounters* with enemy aircraft.
- The number of encounters with enemy aircraft does not directly correlate with the number of combats.
The number of victories a given type has is related to opportunity. The Spitfire as a short range interceptor held back in the UK for home defence for the first half of the war does not help it gain a lot of victories.
That the Lutwaffe would generally not engage Spitfires "leaning into France" except on their own, favourable, terms denied the Spitfire opportunities to rack up kills.
That by early to mid 1943 the Luftwaffe would avoid engaging Spitfires because they could not be sure, until perhaps too close, if the Spitfire was V, IX or XII also denied an opportunity to rack up the kills.
That when the Luftwaffe withdrew the bulk of its fighter forces from France to Germany so that they could take on the "Boeings" unhindered from P-47 and Spitfire escorts meant that there was little opportunity for kills.
I assume you mean a metric for an aircraft's effectiveness? I'm not sure there is one, as there are too many variables.
Take your example of aces. Is an aircraft more effective if there have been 20 pilots with 5 kills, or 50 pilots with 2 kills, or 100 pilots with 1 kill?
* by encounters I mean that the pilot can see enemy aircraft.
Think too much is written about boosting the Spitfires bonifidies over P40 and Hurricane.
P40 was used by everyone during WW2 a lot..! It was a more useful versatile plane.
The platform was successful with a radial or the two inline engines installed in it.
Actually the Brits did use the Tomahawk for raids into France and patrolling low level defense interdiction from Germans because of its range.
Not much written about these missions.
Suspect the same 70 inches they were getting out of the P51 was using the same fuel.
The issue with British aircraft was not that they were not good or useful.
They never had the fuel capacity for sustained fight.
Which is where the P40 faired well.
Understated...the P40 would burned 500/600 lbs of fuel off lightening it for better performance.
On the other hand there is too much written about boosting the P-40s bonafides over the British aircraft.
In part because only 29 such missions were ever flown?
It also depends when and where and by which versions of the Tomahawk you are claiming these missions were flown by, more later.
The Tomahawk used the -33 engine and the Mustang used the -39 engine. Due to the better streamlining of the Mustang it was about 25-30mph faster than the P-40 on the same power.
This meant it got slightly more ram. Please also note that the engine chart for the -33 engine that gives just over 61in at sea level (no ram) is down to 52-53in at 5000ft.
The faster speed of the Mustang gave it a better shot at hitting 70in or allowed less over revving of the engine, more later.
Actually you are rather over stating the case, a P-40B that has burned off 600lbs of fuel has 60 US gallons (50 imp gal) left for combat, the return flight and any reserve deemed appropriate.
P-40Bs and Tomahawks up until the IIB version did not carry drop tanks. That capability came with the P-40C and the Tomahawk IIB.
It gives it better range/endurance than the British fighters but not by the margins being claimed.
The suitability of the early Tomahawks and P-40/P-40Bs for combat is subject to question. The P-40 no letter and the Tomahawk Is had no armor, no BP wind screen, no self sealing fuel tanks. Depending on when (late 1940 and early 1941) there is a serious question about their engines. Allison had to rebuild 277 -33 engines for the US Army at company expense to get them up to the rated power at the desired engine life. No mention if the British got any of these early engines or what remedy there was. US flew the unmodified engines at 2770 rpm and lower boost until the engines were overhauled/upgraded.
When touting the virtues of the the early P-40s there are four engines to consider even though there are only two model numbers. As mentioned the very early -33 engines had to be upgraded, which included new crankshafts and other parts. The -33 also used the epicyclic reduction gear which Allison had recognized as a weak point pretty early on which is why they designed the spur reduction gear. In testing they were getting failures at around 1300hp with the epicyclic reduction gear, confusingly it was the crankshaft that was failing right behind the front bearing. Ability to use 70in MAP or anything to close to it is highly suspect except in the most extraordinary circumstances.
The -39 engine used in the P-40D/E and Mustang also came in two versions which do not have seperate designations. You have the engines built up until Dec 1941/Jan 1942 and the engines built afterwards. The early engines had shot peened crankshafts and the later engines were both nitrided and shot peened. The late engines also got a new crankcase that was stronger. Pulling 70in in a Mustang with a late -39 engine for 15-20 minutes is absolutely no guarantee that you could do such a thing with an early -33 engine.
The P-40B and the Tomahawk IIA had armor and externally protected tanks, the P-40C and Tomahawk got internally protected tanks and the drop tank. however the internal protection for the tanks cost about 12 gallons of fuel.
For the US some of the published performance specs for the long nosed P-40s are at ridiculously low gross weights. Like filling the tanks with only 120 gallons of fuel.
The published ranges are often "yard stick" ranges. P-40B could fly 805 miles at 202mph at 15,000ft. on 120 gallons of fuel, But only if you could magically levitate the plane to 15,000ft with an already warmed up engine as it was rated at 4 hours endurance at 30 gal an hour on that 120 gallons (speed and climb were figured on an 6,833lb gross weight)
British evaluations are mixed, early versions (Tomahawk Is) are given good ratings for performance (speed, climb maneuverability) but are lacking operational equipment.
British also had a lot trouble with the .50 cal guns in the Early P-40s which tended to limit their firepower.
Mention is made of the fitting of cameras to the Tomahawks for recon/army co-operation and while the pilots of the first squadrons are pleased (they had been Flying Lysanders as late as June 1941). However this book claims that the automatic cameras fitted to the Tomahawks required the plane to fly at 150mph when taking pictures (to get proper overlap? guessing) or misprint? In any case the Tomahawks in these squadrons (eight in winter/spring of 1941/42) were replaced by Mustangs as rapidly as possible.
The early P-40s did do a lot of good work but also had a number of problems. We should be careful not to project some of the capabilities of later P-40s backwards onto them.
On the other hand there is too much written about boosting the P-40s bonafides over the British aircraft.
In part because only 29 such missions were ever flown?
It also depends when and where and by which versions of the Tomahawk you are claiming these missions were flown by, more later.
The Tomahawk used the -33 engine and the Mustang used the -39 engine. Due to the better streamlining of the Mustang it was about 25-30mph faster than the P-40 on the same power.
This meant it got slightly more ram. Please also note that the engine chart for the -33 engine that gives just over 61in at sea level (no ram) is down to 52-53in at 5000ft.
The faster speed of the Mustang gave it a better shot at hitting 70in or allowed less over revving of the engine, more later.
Actually you are rather over stating the case, a P-40B that has burned off 600lbs of fuel has 60 US gallons (50 imp gal) left for combat, the return flight and any reserve deemed appropriate.
P-40Bs and Tomahawks up until the IIB version did not carry drop tanks. That capability came with the P-40C and the Tomahawk IIB.
It gives it better range/endurance than the British fighters but not by the margins being claimed.
The suitability of the early Tomahawks and P-40/P-40Bs for combat is subject to question. The P-40 no letter and the Tomahawk Is had no armor, no BP wind screen, no self sealing fuel tanks. Depending on when (late 1940 and early 1941) there is a serious question about their engines. Allison had to rebuild 277 -33 engines for the US Army at company expense to get them up to the rated power at the desired engine life. No mention if the British got any of these early engines or what remedy there was. US flew the unmodified engines at 2770 rpm and lower boost until the engines were overhauled/upgraded.
When touting the virtues of the the early P-40s there are four engines to consider even though there are only two model numbers. As mentioned the very early -33 engines had to be upgraded, which included new crankshafts and other parts. The -33 also used the epicyclic reduction gear which Allison had recognized as a weak point pretty early on which is why they designed the spur reduction gear. In testing they were getting failures at around 1300hp with the epicyclic reduction gear, confusingly it was the crankshaft that was failing right behind the front bearing. Ability to use 70in MAP or anything to close to it is highly suspect except in the most extraordinary circumstances.
The -39 engine used in the P-40D/E and Mustang also came in two versions which do not have seperate designations. You have the engines built up until Dec 1941/Jan 1942 and the engines built afterwards. The early engines had shot peened crankshafts and the later engines were both nitrided and shot peened. The late engines also got a new crankcase that was stronger. Pulling 70in in a Mustang with a late -39 engine for 15-20 minutes is absolutely no guarantee that you could do such a thing with an early -33 engine.
The P-40B and the Tomahawk IIA had armor and externally protected tanks, the P-40C and Tomahawk got internally protected tanks and the drop tank. however the internal protection for the tanks cost about 12 gallons of fuel.
For the US some of the published performance specs for the long nosed P-40s are at ridiculously low gross weights. Like filling the tanks with only 120 gallons of fuel.
The published ranges are often "yard stick" ranges. P-40B could fly 805 miles at 202mph at 15,000ft. on 120 gallons of fuel, But only if you could magically levitate the plane to 15,000ft with an already warmed up engine as it was rated at 4 hours endurance at 30 gal an hour on that 120 gallons (speed and climb were figured on an 6,833lb gross weight)
British evaluations are mixed, early versions (Tomahawk Is) are given good ratings for performance (speed, climb maneuverability) but are lacking operational equipment.
British also had a lot trouble with the .50 cal guns in the Early P-40s which tended to limit their firepower.
Mention is made of the fitting of cameras to the Tomahawks for recon/army co-operation and while the pilots of the first squadrons are pleased (they had been Flying Lysanders as late as June 1941). However this book claims that the automatic cameras fitted to the Tomahawks required the plane to fly at 150mph when taking pictures (to get proper overlap? guessing) or misprint? In any case the Tomahawks in these squadrons (eight in winter/spring of 1941/42) were replaced by Mustangs as rapidly as possible.
The early P-40s did do a lot of good work but also had a number of problems. We should be careful not to project some of the capabilities of later P-40s backwards onto them.
Interesting, peacetime little of this showed up as urgent to get fixed.
The same technology to improve reliability are the same used in my drag racing engines.
IMO the Allison was the better stronger easier to build platform than the Merlin.
One question; At what speed does the ram affect an engine performance?
actually 1940 and 1941 were a desperate scramble to get new designs into production and increase production overall. Granted the US was not involved in a shooting war but you can't be too lackadaisical and improve production numbers as fast as Allison (and P&W and Wright) did.
Allison from the end of 1938 to the end of 1939 increased their floor space by 4 times, number of employees almost 2 1/2 times and engine production over 3 times (from 14 to a whopping 46) By the end of 1940 the floor space went up 3 times over 1939, employees went up about 6 times and engines delivered for the year went to 1175. In 1941 production went to around 6400 with 1100 built in Dec alone. Back in 1937-38 the Allison engineering dept consisted of 25 people and that included 2 men who ran the blueprint machine.
Think this is correct.
300 mph ISA at Sea Level the Ram would be same 300 mph IAS at 20,000 ft.
This where I start to get out of my expertise (such as it is) as you have 29.92in pressure at sea level vs 13.75in at 20,000ft and the air is 0.5327 times as dense.
You do have the same speed of air flow but the mass is different and the pressure ratio may be different (or pressure rise in the intake duct?)
On the other hand there is too much written about boosting the P-40s bonafides over the British aircraft.
In part because only 29 such missions were ever flown?
It also depends when and where and by which versions of the Tomahawk you are claiming these missions were flown by, more later.
The Tomahawk used the -33 engine and the Mustang used the -39 engine. Due to the better streamlining of the Mustang it was about 25-30mph faster than the P-40 on the same power.
This meant it got slightly more ram. Please also note that the engine chart for the -33 engine that gives just over 61in at sea level (no ram) is down to 52-53in at 5000ft.
The faster speed of the Mustang gave it a better shot at hitting 70in or allowed less over revving of the engine, more later.
Actually you are rather over stating the case, a P-40B that has burned off 600lbs of fuel has 60 US gallons (50 imp gal) left for combat, the return flight and any reserve deemed appropriate.
P-40Bs and Tomahawks up until the IIB version did not carry drop tanks. That capability came with the P-40C and the Tomahawk IIB.
It gives it better range/endurance than the British fighters but not by the margins being claimed.
The suitability of the early Tomahawks and P-40/P-40Bs for combat is subject to question. The P-40 no letter and the Tomahawk Is had no armor, no BP wind screen, no self sealing fuel tanks. Depending on when (late 1940 and early 1941) there is a serious question about their engines. Allison had to rebuild 277 -33 engines for the US Army at company expense to get them up to the rated power at the desired engine life. No mention if the British got any of these early engines or what remedy there was. US flew the unmodified engines at 2770 rpm and lower boost until the engines were overhauled/upgraded.
When touting the virtues of the the early P-40s there are four engines to consider even though there are only two model numbers. As mentioned the very early -33 engines had to be upgraded, which included new crankshafts and other parts. The -33 also used the epicyclic reduction gear which Allison had recognized as a weak point pretty early on which is why they designed the spur reduction gear. In testing they were getting failures at around 1300hp with the epicyclic reduction gear, confusingly it was the crankshaft that was failing right behind the front bearing. Ability to use 70in MAP or anything to close to it is highly suspect except in the most extraordinary circumstances.
The -39 engine used in the P-40D/E and Mustang also came in two versions which do not have seperate designations. You have the engines built up until Dec 1941/Jan 1942 and the engines built afterwards. The early engines had shot peened crankshafts and the later engines were both nitrided and shot peened. The late engines also got a new crankcase that was stronger. Pulling 70in in a Mustang with a late -39 engine for 15-20 minutes is absolutely no guarantee that you could do such a thing with an early -33 engine.
The P-40B and the Tomahawk IIA had armor and externally protected tanks, the P-40C and Tomahawk got internally protected tanks and the drop tank. however the internal protection for the tanks cost about 12 gallons of fuel.
For the US some of the published performance specs for the long nosed P-40s are at ridiculously low gross weights. Like filling the tanks with only 120 gallons of fuel.
The published ranges are often "yard stick" ranges. P-40B could fly 805 miles at 202mph at 15,000ft. on 120 gallons of fuel, But only if you could magically levitate the plane to 15,000ft with an already warmed up engine as it was rated at 4 hours endurance at 30 gal an hour on that 120 gallons (speed and climb were figured on an 6,833lb gross weight)
British evaluations are mixed, early versions (Tomahawk Is) are given good ratings for performance (speed, climb maneuverability) but are lacking operational equipment.
British also had a lot trouble with the .50 cal guns in the Early P-40s which tended to limit their firepower.
Mention is made of the fitting of cameras to the Tomahawks for recon/army co-operation and while the pilots of the first squadrons are pleased (they had been Flying Lysanders as late as June 1941). However this book claims that the automatic cameras fitted to the Tomahawks required the plane to fly at 150mph when taking pictures (to get proper overlap? guessing) or misprint? In any case the Tomahawks in these squadrons (eight in winter/spring of 1941/42) were replaced by Mustangs as rapidly as possible.
The early P-40s did do a lot of good work but also had a number of problems. We should be careful not to project some of the capabilities of later P-40s backwards onto them.
A few inaccuracies as follows:-All basically true but a couple of points, first in general about new fighters...
The Spitfire and Bf 109 initially also lacked armor or self sealing tanks and got some in stages, I know the Spit got a 'bullet resistent' windscreen in 1939 and a little bit of armor, but this was just 3mm thick on the fuel tanks, barely enough to stop a .357 at close range let alone a 20mm cannon. Some time in mid 1940 they started adding a reasonable amount of pilot armor, externally 'sealed' tanks around the same time and true self sealing tanks a bit later. The first Hurricane Mk I's also lacked armor which was added around the same time (in mid 1940). I could be wrong but I think some Spits and Hurricanes flying in first couple of months of the BoB did not actually have armor. A 'modern' level of armor with added pilot protection and some coverage for the ammunition boxes was incorporated into the much maligned Spit V series some time in 1941. I'm not certain but I think the first real bullet proof windscreens were being experimented with around that time too.
The first P-40s were about a year behind this development cycle because the US wasn't yet fighting for their life in a war, but this oversight was remedied quickly enough.
Teething problems with new engines were also basically the rule rather than exception. The Allison V-1710 did pretty well for being first deployed in 1937. Everyone underestimated the power and endurance that was really going to be needed in the war, but the Allison did pretty well as they go.
The Tomahawk
We think of the early P-40B and C / Hawk 81 as an American war machine but it's most important service was actually in the hands of the British, and to a lesser extent the Soviets. Their heyday was not at Peal Harbor or with the AVG, but two months earlier in the Western Desert and the Steppes of Russia in October 1941. The first batch (lacking armor and self-sealing tanks, and with only 4 guns) was supposed to be a run of 524, but only 200 were finished for the US order. 140 were supposed to be made for the French, and by April 1940 they were ready and already in French markings* getting finishing touches before being shipped... but the Battle of France ended abruptly in June 1940.
These were sent to England in September 1940, not as Lend Lease incidentally. Most were used as training aircraft, though a few were send to the Middle East as Tomahawk Mk I. As far as I can tell only one squadron No. 112 Sqn RAF, actually got the Tomahawk I starting in July 1941, which even without armor etc. were an improvement over their Gladiators.
Once they did get the armor and self sealing tanks into them the British were much keener on these planes. Curtiss quickly built 110 Tomahawk IIA explicitly for the British, equivalent to P-40B with armor and externally self sealing tanks, but no drop tank plumbing. About ~20 of these were sent strait to the Soviets. Britain asked for some more changes and these were implemented by Curtis as the Tomahawk IIB (P-40C equivalent), heavier and a bit slower but far more robust. The British ordered 930, with 195 being diverted to the Soviets after June 1941. A few were also sent to the Turks. In England, 2 Sqn RAF and 26 Sqn RAF was using Tomahawks briefly for interdiction over France.
Tomahawks in the Western Desert
As I can determine, in addition to ~40 Tomahawk I sent to 112 Sqn in July 1941, ~100 Tomahawk IIA, and ~700 Tomahawk IIB were sent to Egypt in August and September to join the rapidly intensifying war there, starting an expedited training work up. They were assigned to no less than 10 RAF squadrons, 2 SAAF squadrons and 1 RAAF (3 Sqn). The need was pressing. I./JG 27 had been deployed to Africa since April 1941 and were taking a heavy toll on the Gladiators, Hurricanes, Lysanders and Blenheims of the DAF, and II./JG 27 deployed to Libya at the end of September doubling their numbers.
In October about half of these RAF units went operational with the Tomahawk II and it immediately started taking a toll on enemy aircraft. The Italians retired their older Cr 32s from combat and relegated Cr 42s to fighter bomber duties. The Germans pulled Bf 110 from fighter operationas and asked for the newer Bf 109F-2 to replace their older "Emils" at an accelerated rate. Tomahawks were immediately engaged in heavy fighting covering Operation Crusader and the retreating forces after the battle of Tobruk in November, and allied victories at Capuzzo and Ed Duda in December. DAF policy was to protect the bombers and concentrate on ground support, but they would fight when attacked. After a battle on Nov 22, 1941 over Bir Hachim in which 20 Bf 109F-2s engaged 13 Tomahawk IIB's of 112 RAF and 3 RAAF, losing 4 Bf 109s, the German's changed policy not to engage this type in close air combat, but instead to focus exclusively on hit and run attacks. They still had an advantage, but they couldn't press home their attacks as much as previously.
Tomahawks in Russia
At the same time, in October, about 200 Tomahawk IIA and IIBs sent to Russia earlier in the year went into action in the critical battles at Moscow and Leningrad fronts. There they scored many victories and the Soviet squadrons that flew them became guards units. By February however nearly all of the remaining Tomahawks were grounded due to maintenance issues associated with the Winter. But considering the razor thin margins by which the Soviets were able to slow and then stop the German advance in these two cities, and the high number of claims (compared to other Soviet squadrons) made by the Tomahawk units, it's reasonable to assume they did play a role in this outcome. If those had been just another handful of I-16 or Mig-3 squadrons, who knows? Maybe the battle could have tipped the other way. So compared to the brief battles in Hawaii and the exploits of the AVG, as important as those were, these Campaigns in foreign use were far more important air battles (in my opinion), in the sense that the Tomahawk actually played a significant role, if only as a 'speed bump', in slowing down the German onslaught on two fronts.
Interestingly when the first Kittyhawks first arrived around Dec 1941, (with again nearly the whole production run of 560 Kittyhawk I / P-40D going to the British), they were not as well liked by the pilots. With the extra weight from the 6 heavy machine guns and other gear, and the lower factory rated engine settings, they were more sluggish, definitely losing a step in terms of climb rate (just under 2,000 fpm vs. 3,000 fpm for the Tomahawk) and speed. It wasn't until increased power settings, not just actual full fledged overboosting as increased manifold pressure used for most regimes. This seems to have been sorted out by around April or May of 1942, after which the performance of the Kittyhawk I and IIA (P-40E) greatly improved, and with it the fortunes of the hard pressed DAF. This incidentally coincides nicely with the improvements made to the V-1710-39 starting around Dec 1941.
Oh and yes, overboosting
Incidentally, there seems to be more and more of these books coming out now about WWII air combat where they actually check the records from both sides. I just got another new one which I really liked called "South Pacific Air War". The first volume is out with two more coming in November, according to Amazon. This first volume covers just two months - March and April of 1942, and centers mostly on the exploits of a couple of USAAF medium bomber (B-25 and B-26) squadrons and 75 Sqn RAAF (Kittyhawk IA) in defending Port Morseby in New Guinea, and on their Japanese opponents in two A6M squadrons, one of them the elite and famous Tainan Air Group, and two units of G4M medium bombers.
The brave and hard suffering pilots of 75 Sqn had very little training on type before being thrown into the breach, so to speak, and got few re-inforcements before being rotated out for a rest in May 1942 having used up almost all of their aircraft about a third of their pilots. They did well at first but by the 5th or 6th week of combat, after the second Japanese fighter group had joined the battle, and with almost every pilot suffering dysentery or malaria or both, they were really suffering. One Aussie pilot seems to have perhaps discovered a hidden capability in his aircraft that saved his life, which I will now share with you here. This is from page 164 describing an engagement on 26 April, the day after ANZAC Day. A flight of four Kittyhawks had just attacked 7 A6M2s of Tainan Kokutai who were doing a sweep over Port Morseby. The Japanese pilots turned into the attack and engaged, and none were hit sufficient to cause any real damage in the initial bounce. The Kittyhawks dove to disengage but maybe didn't have enough room to dive, instead getting chased around the harbor by the angry Tainan Ko pilots. The rest is directly from South Pacific Air War, Volume II:
"The most excitement was had by Michael Buttler in [Kittyhawk Ia] A29-48, who found himself chased through the Port Moresby foothills by a lone Zero. Then as he emerged over the sea, other Zeroes joined the chase until he had five on his tail. By dangerously overpowering his engine he could just draw away from them at around 300 miles per hour. But then he'd have to relax the power slightly and the Zeros would gain on him and fire ranging shots. Butler later estimated this went on for 120 miles before he got back to Morseby.
..."I thought "Now, bust you," I'd lost them... I thought they'd turned inland but would wait for me to try to land at Seven Mile. So I thought "Well, I'll trick you. I'll land at the civil 'drome.' So I ... landed at Three Mile instead. I was absolutely stonkered. I got out of the aeroplane. I couldn't talk. A Yank came up to me and I think I smoked about half a packet of cigarettes before I was sensible.... I've never been so scared in my life and I was really in a mess."
Incredibly, Butler had survived without a single hit to his aircraft. Overall there were no losses to either side in this combat, although four Zeros had again receive minor damage."
The bold emphasis is by me. Sounds like he discovered overboosting right there in April 1942. Managed to do it for a while too, sounds like about 25 minutes on and off, probably watching the temperature gauge. Probably wouldn't have pushed the throttle past the stop if he wasn't in such dire peril. But I bet it wasn't the last time he used that trick, seeing as he survived the war.
*just imagine if the Battle of France had started 3 months later... the French would have had a lot more to use and not just the Tomahawk, but the Tomahawks would have probably made a difference since the Hawk 75 was the top scoring fighter for the French. I think the VG-33 and about 200 more D.520s might have helped too.
IMO Allison should have built the 2 Stage 2 Speed supercharger.
Installed it just gave it to Curtis to put in the P40 and Allison Mustang
Curtis was already constructing the P40Q and P60.
Still not finding performance numbers with British 100/130 octane fuels used in P40 or early Mustangs boosting at 70 inches.
A few inaccuracies as follows:-
140 Tomahawk I's to Army Co-operation Command
5 ME RAF ME Tomahawk squadrons, one Marine squadron and IIRC initially 4 Kittyhawk squadrons, 10 overall by end 1942.
The Spitfire and Bf 109 initially also lacked armor or self sealing tanks and got some in stages, I know the Spit got a 'bullet resistent' windscreen in 1939 and a little bit of armor, but this was just 3mm thick on the fuel tanks, barely enough to stop a .357 at close range let alone a 20mm cannon. Some time in mid 1940 they started adding a reasonable amount of pilot armor, externally 'sealed' tanks around the same time and true self sealing tanks a bit later. The first Hurricane Mk I's also lacked armor which was added around the same time (in mid 1940). I could be wrong but I think some Spits and Hurricanes flying in first couple of months of the BoB did not actually have armor. A 'modern' level of armor with added pilot protection and some coverage for the ammunition boxes was incorporated into the much maligned Spit V series some time in 1941. I'm not certain but I think the first real bullet proof windscreens were being experimented with around that time too.
Great info with documentation. Do you by any chance have the rest of the pages or only page 1?Here is an Allison Official report about visiting the British after hearing about the Mid-East RAF (66") and Australia Pacific RAAF (70") using un-approved boosting (60") they were using on the -39 and -73 engines!
LINK- Service Use of high Power Outputs on Allison V-1710 Engines December 1942
Allison letter confirms by December 1942 it was known units were boosting their V1710 allisons to 70" giving around 1780hp at sea level! (only possible by overspeeding engine to 3200rpm on the "low altitude" 8.8 supercharger) Allison warned not to use this boost setting on the newer 9.6 supercharger gearing (P-40M/N?).
RE: Spitfire (and Hurricane) fuel tank armour - yes it was only 10-swg duralumin, but the angle of incoming fire is key. At 200 yards that thickness is capable of deflecting .303-in AP rounds impacting up to 13 degrees, which is very useful protection vs. enemy defensive gunners.
The protective value of the bullet-proof windscreens was essentially the same from the beginning, the revisions mainly concerned lessening the impact on aircraft performance.
With regard to Tomahawk overboost - there's no "discovering" overboost. Early US fighters didn't have automatic boost control, so as soon as you "discovered" the throttle in pilot training you discovered how to overboost the engine. All you had to do was not heed the restrictions from the manual.
Great info with documentation. Do you by any chance have the rest of the pages or only page 1?
If you apply these power settings to the P39D and also remove 500 pounds of guns, ammo and equipment, then factor in the cold weather they operated in, it would sure explain how the P39 was able to handle a 109 or even a 190 at low altitude.
Thank youThat one is on WWIIAircraftPerformance.org, along with the other equally interesting one about Mustangs using the same engine. The Allison memo (3 pages) is here:
http://www.wwiiaircraftperformance.org/P-40/V-1710_Service_Use_of_High_Power_Outputs.pdf