Why were U.S. pursuit fighters at the start of WW2 of lower performance than European fighters?

Back around 1990 two companies, MDAC and OSC, where running around DC saying that use of surplus ballistic missiles (Titan II and Minuteman II) was a bad idea; the real reason was that would compete with their products (Delta II and Pegasus).

MDAC produced a paper saying that the reason the WWII P-51 had to use a British engine was that the WWI aircraft engines that were offered as surplus after 1918 seriously damaged the US aviation industry so badly that the US was behind the rest of the world when WWII arose. In reality after WWI almost nobody wanted to use a rotary engine, either surplus or new, for a host of reasons. And the OX-5 and Liberty engines left over from WWI really did not last very long in service. In reality the US led the way with the Curtiss D-12 as well as both Wright and P&W radial engines. Ironically it was the British who were using the Liberty engine in WWII, in tanks.

But the V-1710, while an excellent engine, generally lighter than a Merlin as well as simpler and easier to maintain, was outstripped in supercharging. It is obvious that the USAAC was focused on the turbosupercharger rather that mechanical two speed and two stage supercharging. So the P-43 was derived from the Seversky AP-4 rather than the XP-41 and they tried to fit turbos in the XP-37 and XP-39, but failed. Less delusional than the Air Corps, the USN opted to go with the two speed two stage mechanical supercharging for the F4F, F4U and F6F, and that worked out fine for them, if not giving them P-38, P-47 or Merlin Mustang performance. Nonetheless, it is inexplicable to me why Allison did not produce at the very least a two speed supercharger for the V-1710 as well as a two-stage supercharger with liquid intercooler/aftercooler. When they finally did, the result could not be fitted into a Mustang, P-39, or P-40 and had a limited and horrible service record.

I read somewhere that NACA was tasked with improving the V-1710 in WWII and the Government "Feathermerchant" assigned the task complained it was a waste of time working on that piece of junk. Attitudes can be deadly, as is evidenced by the Space Shuttle, which was kept flying at great cost for decades after it was proved to be a failure.

MIflyer said:

Note that almost all US fighters had substantially longer ranges than comparable European counterparts. The reason for this is simple. The USA is an enormous country by European standards. A typical European single seat fighter could not make it across TEXAS without running out of gas. The range requirement made most US fighter larger and heavier.


I heartily agree with Snowygrouch's comments on US supercharging. The USAAF focused on turbosuperchargers, which were the correct soultion purely in technical terms but proved to be impossible to implement except in a few cases. The failure of the US to adopt liquid cooled inter/aftercoolers I find to be inexplicable, but then again I took too much thermodynamics in college.

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The US Army focused on single stage supercharging for primary Pursuit - all the way into 1940 to include P-46, leaving high altitude mission performance to turbo supercharged in-line and radial engines as a Doctrine beginning 1937/1938.
Allison was the only proven high performance in-line engine developer and producer. The V-1710 was a very good engine.
Allison was a small company, limited in R&D capital, reporting to a stingy GMC, and experienced great management difficulties controlling growth..
The AAC/AAF barraged Allison with change requests to V-1710, further diluting R&D resources at Allison to investigate and develop internal 2 stage/2 Speed scheme.
Allison instead devloped auxilary second stage as 'small solution' - which was immediately worthless to existing airframes such as P-39, P-40, P-51, P-38 without major airframe/wing CG changes.
R-R entered the camel's nose under the tent by arranging Packard relationship for US License with AAF and War Board approval.
Packard was ready when NAA immediately followed R-R lead to install Merlin in Mustang airframe - despite Allison (and GMC) resistance.
NAA was ready to accept either 1650-1 or 1650-3 without major airframe changes Required by Allison systems installed in P-40Q and P-63.
Once P-51B/D was bought by AAF, and War Board assigned A-1 priority to NAA for Packard Engines, Allison was toast for further consideration of advanced R&D save the XP-51J as their last hope. When war ended only the P-82 in small quantity was fcst.

IMO, the Customer is first on the hit list for 'why not' - as AAF overwhelmed Allison V-1710 development resources.
AAF is also second on the list because they failed to see the benefits of a 2S/2S Allison retrofit V-1710 with integral supercharger to evolve the P-39 and P-40 to broader utility - favoring Turbo approach for P-38 and P-47.
GMC is third on the list, but must be forgiven for investment enthusiasm into Allison R&D if the key (and only) major customer was consumed by indifference

Thanks for that post. I wondered about the backstory on why the Allison was lame.
It wasn't. I always imagined the WW II defense contractors whose names I recognize as giant factories (a la Willow Run). That Allison was a relatively small company is a surprise. I can see how a small company could be overwhelmed by a barrage of change orders. I experienced that myself pre-railroad days.

buffnut453 said:

. The same problem would occur for overloaded P-51s if they were bounced just after take-off. Yes, the P-51 could jettison drop tanks but that would make the CofG issue even worse...unless the pilot could selectively dump fuel from the overload tank. I don't know if the latter was possible.

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Well there is bounced just after take-off and there is bounced just after take-off.
The P-51s were supposed to warm up and take off one of the main tanks, I believe it was the left, and at some point right after take-off (wheels and flaps are up, enough altitude is gained to go around if there is engine trouble) the switch was made to the rear tank, once the rear tank had been drawn down to about 55 gallons (this will not give the absolute max range but allows unrestricted maneuver after dropping the tanks) the change is made to one of the drop tanks and is switched back and forth to keep the aircraft in balance. By the time planes formed up, climbed to 25,000ft or so and started on the part of the flight to got to the rendezvous with the bombers you would have gone though the 30 gallons from the rear tank.
manual for the F-51 says 15 gallons warm up allowance and using normal power it took 24 minutes to get to 25,000ft with either a pair of 500lb bombs or a pair of 75 gallon tanks. Total fuel burned was 52 gallons so that is 15 from main, 30 from the rear tank and 7 gallons from one of the drop tanks. If the Mustangs were getting jumped 24 minutes after take-off (91 miles without circling) something was going very wrong. They hadn't made it to the Dutch/Belgian coast.

buffnut453 said:

. The RAF managed with the -2 design and protected tanks so why not an upgraded F2A-2?

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I don't think anybody was very happy with the protection given to the fuel tanks on the F2A-2 or the British Buffalos. The F2A2 may not have had any or used a CO2 bottle to cut down on the fumes in the tank to prevent fires. didn't do anything for the fuel leaking out.
The British were supposed have wrapped the existing tanks (the main spars) with horse hide and some mixture of glue/rubber?
I don't know if it was 360 degrees or just the front, back and sides. I have no idea if there was much or any clearance between the two spars and top and bottom wing plating.
At any rate the USN wanted the same type of internal fuel bladder/sealant that the rest of the US planes were getting. Apparently they could not do it (or it was even more expensive that fitting the 3 extra tanks) and the F2A-3 was born.

A small threadjack but could the Buffalo have been marginally better if it was built by anybody else and with the specified engines? I'm assuming that allegations of sabotage might also have been reduced.
I think I just answered my own question.

SaparotRob said:

Thanks for that post. I wondered about the backstory on why the Allison was lame.
It wasn't. I always imagined the WW II defense contractors whose names I recognize as giant factories (a la Willow Run). That Allison was a relatively small company is a surprise. I can see how a small company could be overwhelmed by a barrage of change orders. I experienced that myself pre-railroad days.

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In 1939 when they got the contract for the P-40 fighters they had 25 men in the engineering department and that includes the 2 men who operated the blue print machine.
The original plant built around 1930 (?) was designed with idea of making about 100 engines a month (?)
However due the depression and Wright and P & Ws lock on commercial aviation they had only delivered about 30 engines by the end of 1938.
They built 46 engines in 1939. only about 2 (?) of these were for P-40s. 31 of them were for Bell YFM-1s. Big divergence between orders and deliveries.
They were building new factory buildings to handle the new orders. BUT that same 25 man engineering department was responsible for layout/manufacturing sequence in new plant/s.

.year....................................floor space....................................personnel..........................engines delivered.
1938....................................93,598................................................512...............................................14
1939.................................404,652...............................................1,213.............................................46
1940.............................1,221,660................................................7,437............................................1,175.................352 to the US, 833 to the British.

and from the USAAC,
We want engines with propellers in the back,
We want engines with remote drives in front.
we want normal engines.
We want engines with turbo chargers.
We want engines two speed drives.
We want engines with fuel injection.
We want engines with mechanical two stage supercharging.
BTW we want a W-24 engine using two V-1710s stuck together
We want..........................
We want........

MIflyer said:

Back around 1990 two companies, MDAC and OSC, where running around DC saying that use of surplus ballistic missiles (Titan II and Minuteman II) was a bad idea; the real reason was that would compete with their products (Delta II and Pegasus).

MDAC produced a paper saying that the reason the WWII P-51 had to use a British engine was that the WWI aircraft engines that were offered as surplus after 1918 seriously damaged the US aviation industry so badly that the US was behind the rest of the world when WWII arose. In reality after WWI almost nobody wanted to use a rotary engine, either surplus or new, for a host of reasons. And the OX-5 and Liberty engines left over from WWI really did not last very long in service. In reality the US led the way with the Curtiss D-12 as well as both Wright and P&W radial engines. Ironically it was the British who were using the Liberty engine in WWII, in tanks.

But the V-1710, while an excellent engine, generally lighter than a Merlin as well as simpler and easier to maintain, was outstripped in supercharging. It is obvious that the USAAC was focused on the turbosupercharger rather that mechanical two speed and two stage supercharging. So the P-43 was derived from the Seversky AP-4 rather than the XP-41 and they tried to fit turbos in the XP-37 and XP-39, but failed. Less delusional than the Air Corps, the USN opted to go with the two speed two stage mechanical supercharging for the F4F, F4U and F6F, and that worked out fine for them, if not giving them P-38, P-47 or Merlin Mustang performance. Nonetheless, it is inexplicable to me why Allison did not produce at the very least a two speed supercharger for the V-1710 as well as a two-stage supercharger with liquid intercooler/aftercooler. When they finally did, the result could not be fitted into a Mustang, P-39, or P-40 and had a limited and horrible service record.

I read somewhere that NACA was tasked with improving the V-1710 in WWII and the Government "Feathermerchant" assigned the task complained it was a waste of time working on that piece of junk. Attitudes can be deadly, as is evidenced by the Space Shuttle, which was kept flying at great cost for decades after it was proved to be a failure.

Click to expand...

The space Shuttle was never proven to be a failure.

They had a spectacular accident that was flagged by warning temperature sensors on the o-rings that was overridden and bypassed by ground control. Ignoring a temperature warning is not a design flaw; it is a human decision failure. Turned out to be a valid warning, didn't it?

buffnut453 said:

SR6, you often make this comment about the F2A-3. However, is it fair to ignore the capacity of that tank?

When the F2A-3 entered service, the US was still at peace with peacetime rules for flight authorizations. As such, it makes perfect sense for there to be stencils on an overload tank warning that it should only be filled under certain authorized circumstances.

Take the P-51 as a comparison. It, too, had an overload tank that negatively impacted aircraft handling during take-off and climb-out. During WW2, under wartime flight authorizations, filling that tank was driven solely by mission tasking. I'd bet good money that, in 1946 under peacetime authorizations, that overload tank would only be filled "under special orders." Yet nobody quotes the P-51's maximum range by caveating "special orders" use conditions for the overload tank.

Seems like there's a double standard at play here when comparing the much-loved P-51 and the unloved F2A-3.

Click to expand...

Not sure what you are referring to? The standard procedure from day one of production Mustangs - Start engine with fuel selector to LH main - which had reverse feed to LH Main for overflow return. If engine shut off the fuel would drain back. After warm up and take off and formation assembly, every one would switch to fusetank to reduce the tank (if completely filled to 85 gal) by 30+ gallons to 55/60 for safe CG limits. Then switch to external 'auxiliary' tank of choice (usually RH to offset fuel burned in LH main). After drop tanks released the process was usually to swith to RH Main to once again offset LH Main drained at warm up and take off.

Save extreme long range requirements the SOP for P-51B/C/D/K with 85 gal fuse tank was to fill only 55 to 60 gal. For That condition the fuselage tank was last in the useage profile - with Left Main (takeoff), Right Auxiliary/Left auxiliary until dry, RH main/LH main to maintain roll balance for ease of trim until dry - then switch to fuse tank. I recall my father saying that he often landed with more than 40 gal in fuse tank - even for Berlin/Munich missions in which there was no combat, Also missions in which fuel remained in 110gal auxiliary tanks just because he/they wanted to deny germans steel donations. Impregnated tanks rarely made it past the midway mark.

In peacetime conditions the Fuselage tank was rarely filled. For many training command flights, with or without fuse tank - the P-51 mains would be filled to 50 gallons each ("Fighter Condition").

For earliest models (Mustang I) model the capacity for each main was slightly less (85 vs 92) but the tanks were contiguous. Only for Mustang I was there an internal auxiliary tank (s) - Kits were provided to install pumps and two cells totalling 27 gal. I Do not know if the presence of the internal auxiliary tanks changed SOP. I suspect not, but cannot confirm.

Maximum Range for Ferry and Combat Radius purposes pretty much follow the above procedures except to note that desired plan was to reduce the wing fuel to near zero and save the last of the fuselage tank for reserve.

Maybe I mis-interpreted your comment?

Shortround6 said:

The US fighters were designed for more range/fuel capacity. But it was for transfers, not combat.

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From the 1939 Curtiss Hawk 75 manual/Sales Booklet, seems that more than just transfers were possible


That's max fuel and max bombload. That was unusual for the period

Was this for Curtiss trying to offer more capability for export sales, given the USAAC dalliance with the P-35?

From some season that has not been explained, at least in the public eye, the US pursuits/fighters stopped carrying bombs after the P-35 didn't start again until P-40C (?).

Curtiss was selling planes all over the place and their customers wanted fighters that could double as ground attack aircraft. Many of the Curtiss Hawk biplanes could carry a pair of 116lb bombs or a number of smaller ones and that was with a 600-700hp engine.

However the ability to carry one or more bombs under the center of gravity did not always translate into being able to perform combat maneuvers with a full load of fuel.
P-36s and Hawk 75s carried a tank if about 60 gallons behind the pilots seat, this tank did not change location throughout the production of the P-40, However the fuel load did.
In the P-36/Hawk 75 the rear tank was supposed to be empty or nearly so when doing maneuvers, French crashed at least one and possibly more when they tried to fill the tanks.
IN the P-40s with the long V-12 engines and extra weight the prohibition on combat maneuvers with with rear tank full went away. During the rest of the P-40 history the tank situation changed around a bit. In a P-40E or K the planes took off on the forward tank. Then switched to the rear and burned it down, then switched to the middle tank (under the pilots seat) and used the forward tank for reserve/landing. P-40F&L with the heavier Merlin engine were supposed to keep 25-30 gallons in rear tank at all times and use that fuel for reserve/landing. P-40Ls and early N took out the forward tank to lighten the plane and kept the standard behind the seat tank.

I don't know what some of the other US fighters did but the P-39 had all of it's internal fuel in the leading edge of wing, so no CG change with different fuel loads, one drop tank on the CG.

Edit, also note the "Very slight reduction speed, climb and load factors" phrase. This was an advertising brochure, not a pilot's manual.
I can stick over 1/2 a ton of cargo in a small pick-up truck for a Very slight reduction speed, hill climb and gas milage factors" according the salesman at the dealership

GregP said:

The space Shuttle was never proven to be a failure.

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It certainly was a failure in that it never came close to living up to its original design goals. Its reusable elements were supposed to reduce launch costs compared to expendable rockets, but in fact it ended up costing more. It was supposed to be able to support up to 60 launches per year, part of how it would reduce costs, but it never achieved anything close to that many launches per year.

It was an impressive bit of technology, and could do things other launch vehicles could not. But it fell far short of what it was intended to be, for a variety of reasons.

33k in the air said:

It was supposed to be able to support up to 60 launches per year, part of how it would reduce costs, but it never achieved anything close to that many launches per year.

It was an impressive bit of technology, and could do things other launch vehicles could not. But it fell far short of what it was intended to be, for a variety of reasons.

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A big reason might be expecting a one-month turnaround per ship in a five-ship fleet, which is what 60 launches a year implies. 'Twas a good effort all the same.

Shortround6 said:

The P-51s were supposed to warm up and take off one of the main tanks, I believe it was the left, and at some point right after take-off (wheels and flaps are up, enough altitude is gained to go around if there is engine trouble) the switch was made to the rear tank, once the rear tank had been drawn down to about 55 gallons (this will not give the absolute max range but allows unrestricted maneuver after dropping the tanks) the change is made to one of the drop tanks and is switched back and forth to keep the aircraft in balance.

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Rear tank down to 35G, no maneuvers or even tight turns until then.

drgondog said:

So by the end of 1940, the YP-38 has been flown; 24 P-39C delivered;

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The P-39C began acceptances in January 1941.

The USAAF fighter program, late 1930's to 1940. Mostly ignoring any contracts for cancelled aircraft and any diversions. The A program was approved June 1940, the B program approved September 1940, the AC program was pre war.

76 P-35 Program AC Funds PR Contract AC-8892 Dated 30-Jun-36, accepted from July 1937
3 P-36 Program AC Funds PR Contract AC-9045 Dated 7-Aug-36, accepted May 1938
209 P-36 Program AC Funds PR Contract AC-10136 Dated 30-Jul-37, accepted starting September 1938
1 XP-37 Program Experimental Funds Experimental Contract AC-9555 Dated 16-Feb-37, accepted July 1937.
13 YP-37 Program AC Funds PR Contract AC-10535 Dated 11-Dec-37, 1 in May, 1 in Oct and 10 in Nov 39, 1 in Jul 40.
1 XP-38 Program Experimental Funds Experimental Contract AC-9974 Dated 23-Jun-37, accepted October 1939
66 P-38 Program AC Funds PR Contract AC-13205 Dated 16-Sep-39, YP-38 accepted September 1940 to June 1941, P-38 from June 1941
290 P-38 Program A Funds PR Contract AC-15646 Dated 30-Aug-40
197 P-38 Program B Funds PR Contract AC-15646 Dated 16-Sep-40
1 XP-39B Program Experimental Funds Experimental Contract AC-10341 Dated 7-Oct-37, accepted December 1939
80 P-39 Program AC Funds PR Contract AC-13383 Dated 12-Dec-39, YP-39 accepted September to December 1940, P-39C starting January 1941.
120 P-39D Program A Funds PR Contract AC-15675 Dated 9-Sep-40
1 XP-40 Program AC Funds PR Contract AC-10136 Dated 30-Jul-37, accepted December 1938.
524 P-40 Program AC Funds PR Contract AC-12414 Dated 26-Apr-39, P-40 acceptances starting in June 1940
540 P-40 Program A Funds PR Contract AC-15802 Dated 13-Sep-40
1 XP-41 Program AC Funds PR Contract AC-8892 Dated 30-Jun-36, P-35 with Turbo, accepted March 1939
XP-42 P-36A development, 1939
13 YP-43 Program AC Funds PR Contract AC-12635 Dated 27-Apr-39
80 RP-43A Program AC Funds PR Contract AC-13380 Dated 12-Dec-39
54 RP-43 Program B Funds PR Contract AC-15850 Dated 13-Sep-40
XP-44 Republic project, 80 ordered but changed to P-43.
P-45 = P-39C
2 XP-46 Program Experimental Funds Experimental Contract AC-13447 Dated 17-Jan-40, first flight 2 Feb 41, accepted Feb 43
1 XP-47B Program Experimental Funds Experimental Contract AC-13817 Dated 17-Jan-40, accepted April 1942
225 P-47 Program A Funds PR Contract AC-15850 Dated 13-Sep-40, acceptances starting December 1941, 6 built to end April 1942.
XP-48 Douglas Project only
1 XP-49 Program Experimental Funds PR Contract AC-13746 Dated 22-Jan-40, P-38 development, first flight 11 Nov 42 accepted Jul 43
XP-50 = Grumman F5F-1
2 XP-51 Program Experimental Funds Experimental Contract AC-15471 Dated 30-Sep-40. Being furnished by the contractor at no cost to the Government as a result of Foreign Release, accepted without engines August 1942.
XP-52 Bell Project only
XP-53 Curtiss P-46 development Project only
2 XP-54 Consolidated Program Experimental 1941, 1942 Funds Experimental Contract AC-15019.SA 1 Dated 8-Jan-41 (1st aircraft, second ordered on 17 March 1943). Accepted Nov-43 and Aug-45
3 XP-55 Program Experimental Funds Experimental Contract AC-29013 Dated 10 July 1942, accepted March 1945
1 XP-56 Program Experimental Funds Experimental Contract AC-15021 Dated 22-Jun-40, Northrop project only.
XP-57 Tucker Project only
1 XP-58 Program Experimental Funds Experimental Contract AC-15867 Dated 14-Oct-40. Being furnished by the contractor at no cost to the Government as a result of Foreign Release, accepted Dec-44.
P-59 Airacomet, not ordered until 1 October 1942.
1 XP-60 Program Experimental Funds Experimental Contract AC-18551 Dated 29-May-41, another 3 ordered under AC-28113 dated 24 July 1942. Acceptances between Jul-42 and Jun-44
2 XP-61 Program Experimental Funds Experimental Contract AC-17442 Dated 30-Jan-41, accepted July and August 1943.
1 XP-70 Program AC Funds PR Contract AC-12967 Dated 30-Jun-39, accepted July 1942, program heavily delayed by problems fitting turbo superchargers.

The 1941 Experimental program contained 1 P-39E, 2 P-51B, 1 XP-54, 1 XP-56, I XP-61, 2 XP-62 and 2 XP-63. The fighters ordered on the A and B programs as ultimately delivered

GregP said:

The space Shuttle was never proven to be a failure.

They had a spectacular accident that was flagged by warning temperature sensors on the o-rings that was overridden and bypassed by ground control. Ignoring a temperature warning is not a design flaw; it is a human decision failure. Turned out to be a valid warning, didn't it?

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Depends on how you define failure, I guess. It got people and cargo into orbit, and most of the time got them back, so was it a success? I would argue it was a severely compromised design, partially by focusing on the entirely wrong things. E.g. "Has to fly like a plane after reentry!" arguably shouldn't be even in the top 10 list of important issues in spacecraft design. This resulted in issues like:

• Not having an escape mechanism for large parts of the ascent envelope. Compare with a traditional design with a capsule on top equipped with an escape tower. One could argue that the Challenger accident could have been survivable with such a setup.
• Mounting the orbiter with it's very vulnerable heat shields on the side of the tank rather than on top. Which quite directly led to the Columbia accident.
• A kerolox 1st stage + hydrolox 2nd/3rd stages would have been a more efficient design than the 1st/sustainer stage hydrolox + SRB.

The one thing that the space shuttle managed to do that a traditional approach couldn't was to save the main engines. Probably not enough to offset all the effort. I think in the end they could have done more or less everything the space shuttle did a lot cheaper by just keeping the Saturn V operational.

Anyway, this is getting very off-topic for this forum. There are spaceflight forums where the above points are rehashed over and over.

33k in the air said:

It certainly was a failure in that it never came close to living up to its original design goals. Its reusable elements were supposed to reduce launch costs compared to expendable rockets, but in fact it ended up costing more. It was supposed to be able to support up to 60 launches per year, part of how it would reduce costs, but it never achieved anything close to that many launches per year.

It was an impressive bit of technology, and could do things other launch vehicles could not. But it fell far short of what it was intended to be, for a variety of reasons.

Click to expand...

It certainly was not a failure. I was around when it was being developed, worked on several components, and was ALWAYS aware that the NASA could never make anything cheaper than the thing it replaced. It wasn't in their wheelhouse to spend less. Everyone knew that going in. Well, everyone who wasn't a newbie, anyway. It WAS a reusable launch vehicle, which was the primary goal. Reducing costs was always dependent upon the rebuild processes used. In FY 2010, the cost was $775M for a launch. It was launched 135 times and had 2 accidents.

One was human error (Challenger) and the other was a re-entry failure (Columbia) after some tiles were detached. Considering the number of parts and the number of mission-critical items that could cause failure, that isn't exactly a horrible record. Nobody ever said there weren't risks; there were.

Let's just say that your definition of a failure was resounding success when viewed from another direction and let it go at that. I very certainly do not consider the Space Shuttle to be a failure and would gladly ride one today if it were still going up. But, it isn't.

End of thread drift from me.

marathag said:

Was the A6M Model 21 Zero of 1940 'Combat ready'?
It didn't have self-sealing tanks, armorglass or even armorplate for the seatback like the P-40B had. Sometimes even the Radio was removed.
It did have 950 hp and 156 US gallons of fuel internally, two MGs and two 20mm cannons, and pilot had good visibility.
Not all that fast, but maneuverable and had long range.

I like to bring up that the French Hawk 75s, fairly similar to the Zero in being lightly armed, was also long ranged and maneuverable and lacking armor and self-sealing tanks, did very well against the Luftwaffe in 1939-40

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The Zero was "combat ready" based on Japanese design theory and aerial combat doctrine that specifically saw no need for armor and self sealing tanks.

varsity07840 said:

The Zero was "combat ready" based on Japanese design theory and aerial combat doctrine that specifically saw no need for armor and self sealing tanks.

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Same as US fighters in 1940.

tomo pauk said:

Same as US fighters in 1940.

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I dont know when SS tanks became mandatory but Hurricanes in France had armour fitted there 1939/40.

pbehn said:

I dont know when SS tanks became mandatory but Hurricanes in France had armour fitted there 1939/40.

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I think the tanks were later and they make have been in stages, not all tanks of the three got them at once (at least in existing planes).
BP glass also did not show up at the same time as armor. This is for many air forces.
The Germans were NOT fully equipped with Armor. BP Glass and protected tanks in 1939. In fact a few German aircraft shot down in the BoB in Aug (one Bf 110C recon plane in particular) did not have much in the way of protective equipment when examined. May have isolated but both sides were refitting existing aircraft as time and supplies allowed.

Armor often started as one or two plates behind the pilots seat Which may or may not have had head protection (extended above the shoulders) . Some planes got an armored seat bottom. Some planes got flat plates and some got curves. Some planes got armor or very thick sheet metal at the base of the windscreen.