Most 'Underrated' Aircraft of WW2?

[wuzak]

Alot of good information but don't you think as p39 expert said if they had the 2 stage Allison in production by April 43 and they new that it was commimg it doesn't seem like to much of a jump to think they could have had the q delivered by spring pf 44.

What 2 stage V-1710 production there was in 1943 was allocated to the P-63.

Just read on Wiki that it was intended that one P-63 prototype was to have a Merlin V-1650-3, but the P-51B had priority.

By the Spring of 1944 you had plenty of P-51Bs and P-51Ds were beginning to arrive.

You also had the P-38J/L arriving, the P-47D was impproving and the British were fielding Spitfire IXs, VIIIs (not in Europe) and the XIV.

The role for the Q would have been extremely limited.

 

[wuzak]

Something to consider is that two stage super chargers really didn't arrive on the scene for liquid cooled engines until 1943 or so in any case. (But the USN demanded, and got, two stage setups even as early as the F4F3, a first at that time).

The Spitfire IX was in production in 1942, and saw service by mid year (debuted in combat over Dieppe in August).

It must be also noted that the 2 stage R-1830 had a critical altitude not much better than a single stage Merlin of the same period.

 

[Shortround6]

The Spitfire IX was in production in 1942, and saw service by mid year (debuted in combat over Dieppe in August).

It must be also noted that the 2 stage R-1830 had a critical altitude not much better than a single stage Merlin of the same period.

How much of the R-1830 two stage superchargers performance (or lack thereof) is attributable to poor US superchargers in general, poor design of the P&W unit in particular or poor cooling of the R-1830 (or a limit on the supercharger drive?) is certainly subject to question.
I would note that many engine lists show the engine in the wildcat limited to 2550 rpm in high gear vs 2700rpm in neutral or low gear. I have no real facts on why. just noting that the limit exists.

 

[michael rauls]

Please define "in production" and when.
The engine used in the March 1944 tests of the P-40Q was not built until early 1944. And even then only 4 were built.
There were several different 2 stage Allisons being test during 1943 but actual production doesn't seem to have started until the late summer or fall of 1943.
This is the V-1710-93 used in the P-63A. While a number of P-63s were built and were flying with this engine in the fall of 43 (Oct sees first deliveries) the engine doesn't finally pass it's model test until Nov 27th 1943 and doesn't pass it's WER test until Dec 1943. It took a long time to develop the water injection and improve the pistons and piston rings to withstand the WER.

The V-1710-121 engine used in the March 1944 tests developed hundreds more hp in the low 20,000ft area than the -93 engine did. Using water injection (and 3200rpm courtesy of a 12 counterweight crank) the -121 could pull 75in of MAP at over 20,000ft. The -93 engine was good for for 51.5in at 22,400ft.

So lets see how well our production P-40Q of the summer of 1943 does with about 500hp less at 22,000ft than the test airplane in March of 1944.

Ok fair enough. I had just read a post by Venturi, who seemed to be knowledgeable in the area ( he certainly knows alot more than I do thats for sure) that they had a 2 stage Alison in production in April 43 and that they had it in planes by late 43. I have read this other places(actually I've read they had a 2 stage supercharger for the Alison I think in 40 although it was troubesom from what I read. Don't know if this is true or not) to which has alwas made me wonder why they didn't slap that thing in the p40/ p39 as soon as possible. The 1943 incarnation that is. Ultimately I'm gonna just say both of you certainly know alot more than I do about it so im just gonna read what you both have to say and I'm quite sure I'll learn something. Heck I already have. Quite a few things in fact. Cheers.

 

[Shortround6]

Allison did have a two stage test rig in 1940. However Allison was trying to go from a shop that made 14 engines in 1938 and 46 engines in 1939 to one that made 1178 engines in 1940 and about 6400 in 1941. And not one model of engine but P-40 engines, P-39 engines and turbo P-38 engines and few other oddballs.


You also have the sad fact that US superchargers weren't the best to begin with (General electric had dominated the supercharge market until the late 30s) , RR was the Best in 1938/39 and then took a quantum leap forward when they hired Stanley Hooker, an aerodynamicist. RR and Hooker also got a leg up on two stage superchargers because they had a few parts from the large Vulture engine hanging around they could grab and use as a test rig. Allison had to start working on the first stage from scratch.
Allison did an amazing job with what they had to work with in the beginning, but expecting them to equal RR superchargers is a bit much. Supercharger design at the time was almost as much art as it was science. When Hooker left RR and went to work for Bristol on their jet engine (which was having trouble) He said he thought the Britisol team didn't understand airflow.

 

[michael rauls]

What 2 stage V-1710 production there was in 1943 was allocated to the P-63.

Just read on Wiki that it was intended that one P-63 prototype was to have a Merlin V-1650-3, but the P-51B had priority.

By the Spring of 1944 you had plenty of P-51Bs and P-51Ds were beginning to arrive.

You also had the P-38J/L arriving, the P-47D was impproving and the British were fielding Spitfire IXs, VIIIs (not in Europe) and the XIV.

The role for the Q would have been extremely limited.

Sounds like thats the why of the why didn't get the q going earlier or just a 2 stage for the N. Just so many ro go around at that point and they were allocated elsewhere. If it were up to me I think I'd have funneled those twards the p40 considering where the respective types were ultimately headed but I would venture to guess I'm about to find out the reasons that may have not been practical.

But the USAAC had specified that the V-1710 be a single-stage.

Once the design is put into production, one simply cannot wave a magic wand and make changes.

Ok I'm honestly confused. Yes I've read that they specified the Alison early on be single stage but also that there was a two stage supercharger that, if I understand correctly could be used on the same engine with little or no modification by spring 43 and I have seen both views expressed here by people that obviously know alot more than me about this. The two views, unless I'm missing something here( always possible) would seem not to conflict unless Alison presented the army with the 2 stage and they said no thanks but this doesn't seem to be the case as they were used in the p63. My thoughts would be either way, if the 2 sage were ready by early 43 an the army said no thanks or if it were ready by then but Curtis chose not to instal the 2 stage it would seem to be a posibly less than optimal desision either way. Again, maybe(probably) I'm missing something here but thats the way it looks to me. Would verry much like your additional thoughts on this.

 

[MiTasol]

The major issue is that Curtiss was too busy building existing variants for a decent price, than in investing in r&d, and sacrificing production line space for changeover. They were above all a business and were more than a bit hidebound. Unfortunately the P40 never received the updates which would have kept it competitive, however it should not be overlooked that it could easily have been so, given the same foresight and effort which kept other airframes of similar vintage in the front running throughout the war - like the 109 or Spitfire.

Yep, and spending a lot of time and effort developing aircraft that had no future which is why they died so soon after the war

 

[GrauGeist]

Yep, and spending a lot of time and effort developing aircraft that had no future which is why they died so soon after the war

Sorry to disappoint, but Curtiss-Wright is still in business and has diversified into several venues while still being grounded in the Aerospace industry.

 

[MiTasol]

Ok I'm honestly confused. Yes I've read that they specified the Alison early on be single stage but also that there was a two stage supercharger that, if I understand correctly could be used on the same engine with little or no modification by spring 43 and I have seen both views expressed here by people that obviously know alot more than me about this. The two views, unless I'm missing something here( always possible) would seem not to conflict unless Alison presented the army with the 2 stage and they said no thanks but this doesn't seem to be the case as they were used in the p63. My thoughts would be either way, if the 2 sage were ready by early 43 an the army said no thanks or if it were ready by then but Curtis chose not to instal the 2 stage it would seem to be a possibly less than optimal derision either way. Again, maybe(probably) I'm missing something here but that's the way it looks to me. Would very much like your additional thoughts on this.

One major issue is that the two stage engine is significantly longer than the single stage engine.

That means typically that the firewall has to be moved aft which means the oil tank & probably other parts have to be relocated to keep the Centre of Gravity where it needs to be OR the rear fuselage has to be extended and equipment that is forward moved aft for the same reason.

The firewall and forward fuselage mount are attached to the front wing spar so moving the firewall aft means significant changes to the wing as well.

Moving equipment aft is restricted by available space and the rear fuselage is already full of the largest fuel tank (62.5 gals with 51 + 32 gals in the wing) of total internal fuel of 145 gals, radio, hydraulic pump and tank, etc.

Extending the fuselage aft not only involves significant redesign but reduces manoeuvrability unless other changes are made which further effects the ability for units to use existing spares and training.

Therefore all options involve major redesign, not minor fiddling, which is why the P-63 is a whole new aircraft and so much longer etc than the P-39.

 

[MiTasol]

Sorry to disappoint, but Curtiss-Wright is still in business and has diversified into several venues while still being grounded in the Aerospace industry.

I guess I mispoke.

As far as I am aware the Curtiss Aeroplane division of Curtiss-Wright have not built any new designs under the Curtiss name since about 1946/47 and I am not aware of any other aircraft where they were a major component manufacturer either since then. As far as I know one of the last projects started by Curtiss Aeroplane was the failed Curtiss-Bleecker helicopter.

C-W was formed about 1930 and Curtiss Aeroplane and Motor was one of the half dozen or so Curtiss and Wright companies incorporated into C-W. To the best of my knowledge the division called Curtiss Aeroplane has ceased to exist but I am most willing to be corrected.

 

[wuzak]

One major issue is that the two stage engine is significantly longer than the single stage engine.

That means typically that the firewall has to be moved aft which means the oil tank & probably other parts have to be relocated to keep the Centre of Gravity where it needs to be OR the rear fuselage has to be extended and equipment that is forward moved aft for the same reason.

The firewall and forward fuselage mount are attached to the front wing spar so moving the firewall aft means significant changes to the wing as well.

Moving equipment aft is restricted by available space and the rear fuselage is already full of the largest fuel tank (62.5 gals with 51 + 32 gals in the wing) of total internal fuel of 145 gals, radio, hydraulic pump and tank, etc.

Extending the fuselage aft not only involves significant redesign but reduces manoeuvrability unless other changes are made which further effects the ability for units to use existing spares and training.

Therefore all options involve major redesign, not minor fiddling, which is why the P-63 is a whole new aircraft and so much longer etc than the P-39.

It is unlikely that the firewall would change position.

The P-40Q was lengthened forwards, so the weight had to balanced by relocating equipment, or by adding mass balances.

It is a good point you make about the length of the engine. The extra length of the 2 stage V-1710 compared to the standard V-1710, or even the 2 stage Merlin was not insignificant.

 

[michael rauls]

One major issue is that the two stage engine is significantly longer than the single stage engine.

That means typically that the firewall has to be moved aft which means the oil tank & probably other parts have to be relocated to keep the Centre of Gravity where it needs to be OR the rear fuselage has to be extended and equipment that is forward moved aft for the same reason.

The firewall and forward fuselage mount are attached to the front wing spar so moving the firewall aft means significant changes to the wing as well.

Moving equipment aft is restricted by available space and the rear fuselage is already full of the largest fuel tank (62.5 gals with 51 + 32 gals in the wing) of total internal fuel of 145 gals, radio, hydraulic pump and tank, etc.

Extending the fuselage aft not only involves significant redesign but reduces manoeuvrability unless other changes are made which further effects the ability for units to use existing spares and training.

Therefore all options involve major redesign, not minor fiddling, which is why the P-63 is a whole new aircraft and so much longer etc than the P-39.

Ok the whole thing makes some sense now. That they chose to keep the existing production lines going instead of doing the re-design to accommodate the supercharger. I'm no expert but certainly seems to me that while it's at least understandable it was not, in my opinion, the best decision as I think it was venturi said with the same foresight and effort that kept other types of similar vintage competitive Curtis could have had the airframes ready to go in spring 43 when the 2 stage became available.

 

[wuzak]

Ok the whole thing makes some sense now. That they chose to keep the existing production lines going instead of doing the re-design to accommodate the supercharger. I'm no expert but certainly seems to me that while it's at least understandable it was not, in my opinion, the best decision as I think it was venturi said with the same foresight and effort that kept other types of similar vintage competitive Curtis could have had the airframes ready to go in spring 43 when the 2 stage became available.

The 2 stage was barely available for the P-63 in the Spring of 1943.

Not going to be many available for P-40Q.

And I'm not real sure where the P-40s being pumped out of the production lines were going. Some no doubt to refit existing P-40 squadrons, some to replace losses and probably many for training squadrons.

Not sure what the point of the P-40Q would have been.

 

[P-39 Expert]

Ok fair enough. I had just read a post by Venturi, who seemed to be knowledgeable in the area ( he certainly knows alot more than I do thats for sure) that they had a 2 stage Alison in production in April 43 and that they had it in planes by late 43. I have read this other places(actually I've read they had a 2 stage supercharger for the Alison I think in 40 although it was troubesom from what I read. Don't know if this is true or not) to which has alwas made me wonder why they didn't slap that thing in the p40/ p39 as soon as possible. The 1943 incarnation that is. Ultimately I'm gonna just say both of you certainly know alot more than I do about it so im just gonna read what you both have to say and I'm quite sure I'll learn something. Heck I already have. Quite a few things in fact. Cheers.

Exactly. The engine (actually just the second stage, as the actual power section of the engine was exactly the same as other comtemporary Allisons) was in series production in April '43, the P-39 and P-40 were in series production since '41, so why was this engine not used?

 

[P-39 Expert]

The 2 stage was barely available for the P-63 in the Spring of 1943.

Not going to be many available for P-40Q.

And I'm not real sure where the P-40s being pumped out of the production lines were going. Some no doubt to refit existing P-40 squadrons, some to replace losses and probably many for training squadrons.

Not sure what the point of the P-40Q would have been.

Actually the two stage Allison was available in spring of '43, but the P-63 airframe was not.

Availability was there, the ENGINES were rolling off the line, the separate second stage had just started production.

P-40 production was going to our allies and to training squadrons.

The point of the P-40Q was to make it a high altitude plane that could operate above 25000' instead of a low altitude plane that could barely get to 20000'.

 

[michael rauls]

The 2 stage was barely available for the P-63 in the Spring of 1943.

Not going to be many available for P-40Q.

And I'm not real sure where the P-40s being pumped out of the production lines were going. Some no doubt to refit existing P-40 squadrons, some to replace losses and probably many for training squadrons.

Not sure what the point of the P-40Q would have been.

The way I'm looking at it anyway the point of the Q would have been that if the p40 was qoing to continue to be delivered then alot of guys got short changed flying m or n instead of a q(not that the m and n weren't good planes). However,. not to be overly dramatic but it's reasonable to think some probably lost there lives due to the lesser performance, at least to me. I gues ot comes down to for me, if you are going to shut down p40 production all together and have Curtis build say p51s( wouldn't that be ironic) then fine there is no point in a p40Q but if we are going continue to equip literally thousands of guys with p40s then they deserve the best p40 that money and effort can buy. I understand there were hurdles to doing this as there is in all aircraft development but to me they were worth jumping to give thpse guys the best we could. Thats how I see it anyway.

 

[swampyankee]

Sorry to disappoint, but Curtiss-Wright is still in business and has diversified into several venues while still being grounded in the Aerospace industry.

It is, however, nowhere near as significant as it was before WWII or in the 1950s.

 

[Shortround6]

Ok, trying to get a few of us on the same page. Good pictures hard to find on the internet so bear with me.

Allison chose to use the fluid coupling and drive shaft to drive the auxiliary stage independently from the engine stage.

This is a post war turbo compound, delete the exhaust piping and the "stuff" to the right of the inlet elbow in the middle of mass on the right.
Allison added a lot of length to the engine when they added the 2nd stage.

If somebody has any real production numbers for the two stage Allisons over the spring and summer of 1943 it would be nice to post it as some of the stuff being posted here sure conflicts with what is said in "Vees for Victory".

I would also note that in a P-40 pilots manual from 1943 they tell the pilots being issued the manual that P-40s will no longer be issued to new squadrons.

The engine that went into the P-63s did not pass it's model test (variation of type test) until Nov 27th 1943 and any P-63s built and flying up until then did so with restrictions placed on the engines. Hardly what you want for planes being issued to combat units. This is certainly not only time that this happened but it is not common.
I would also note that while this two stage engine in the early P-63 was a fearsome beast at low altitude with water injection it was hardly the powerhouse above 20,000ft that some people are making it out to be.
1150hp at 22,500ft is hardly great performance in 1943, let alone at the end of 1943. A Merlin 46 with a single stage supercharger could make 1100hp at 22,000ft at some point in 1942.
Please note the engine in the P-40F and L could make 1120hp at 18,500ft. It weighed 1510lbs dry. The two stage Allison weighed about the same dry.
But if you want to use the extra power you need bigger radiators and oil coolers. You may want a bigger prop.

Not all Allison two stage engines were created equal. It seems that people want to take the power ratings from 1944 (or later) and somehow back date them to the experimental engines of early 1943 and declare them production ready.

Here is a test from May of 1943 on the XP-63A
http://www.wwiiaircraftperformance.org/P-63/XP-63A_42-78015_FS-M-19-1592-A.pdf

Please note that at this time the engine was rated for about 60in at WEP and could not hold that much above 15,000ft. and was down to 1165hp at 22,500ft including RAM.
Would a P-40 with a similar engine have been an improvement over the P-40N? Yes, but then how many P-40Ns are you willing to give up production wise as you change the production lines over in the summer of 1943? What restrictions would be placed on the engines during the summer and fall of 1943 as they sort out piston and piston ring problems?

And again, please note that the P-40Q as tested used about the same armament as the stripper P-40s, some of which got back the extra guns and/or ammo in the field.

 

[michael rauls]

Ok, trying to get a few of us on the same page. Good pictures hard to find on the internet so bear with me.
View attachment 502452
Allison chose to use the fluid coupling and drive shaft to drive the auxiliary stage independently from the engine stage.
View attachment 502453
This is a post war turbo compound, delete the exhaust piping and the "stuff" to the right of the inlet elbow in the middle of mass on the right.
Allison added a lot of length to the engine when they added the 2nd stage.

If somebody has any real production numbers for the two stage Allisons over the spring and summer of 1943 it would be nice to post it as some of the stuff being posted here sure conflicts with what is said in "Vees for Victory".

I would also note that in a P-40 pilots manual from 1943 they tell the pilots being issued the manual that P-40s will no longer be issued to new squadrons.

The engine that went into the P-63s did not pass it's model test (variation of type test) until Nov 27th 1943 and any P-63s built and flying up until then did so with restrictions placed on the engines. Hardly what you want for planes being issued to combat units. This is certainly not only time that this happened but it is not common.
I would also note that while this two stage engine in the early P-63 was a fearsome beast at low altitude with water injection it was hardly the powerhouse above 20,000ft that some people are making it out to be.
1150hp at 22,500ft is hardly great performance in 1943, let alone at the end of 1943. A Merlin 46 with a single stage supercharger could make 1100hp at 22,000ft at some point in 1942.
Please note the engine in the P-40F and L could make 1120hp at 18,500ft. It weighed 1510lbs dry. The two stage Allison weighed about the same dry.
But if you want to use the extra power you need bigger radiators and oil coolers. You may want a bigger prop.

Not all Allison two stage engines were created equal. It seems that people want to take the power ratings from 1944 (or later) and somehow back date them to the experimental engines of early 1943 and declare them production ready.

Here is a test from May of 1943 on the XP-63A
http://www.wwiiaircraftperformance.org/P-63/XP-63A_42-78015_FS-M-19-1592-A.pdf

Please note that at this time the engine was rated for about 60in at WEP and could not hold that much above 15,000ft. and was down to 1165hp at 22,500ft including RAM.
Would a P-40 with a similar engine have been an improvement over the P-40N? Yes, but then how many P-40Ns are you willing to give up production wise as you change the production lines over in the summer of 1943? What restrictions would be placed on the engines during the summer and fall of 1943 as they sort out piston and piston ring problems?

And again, please note that the P-40Q as tested used about the same armament as the stripper P-40s, some of which got back the extra guns and/or ammo in the field.

Wow, such a wealth of information in your post! It's starting to look, to me at least, like alot of those decisions that may look questionable in hindsight years later at first glance were a little more understandable when you start to drill down into it. I think I personally would have been willing to lose some production to change the production lines over in 43 even for a moderate benefit as I think most upgrades on most planes required this to one degreee or another and I think the pilots deserved the best p40 we could give them if we were going to continue to produce p40s at all( just the way I see it). However, I can certainly see the logic behind the decisions that were made even if they werent the ones I would have made. And ya were did all those p40 ns go anyway? I've read that as you said the p40 would no longer be issued to new squadrons after about mid 43( not sure of the exact data here) but a huge part of p40 production occurred after this. Maybe about half as if memory serves, the N accounted for about half total production ?and was produced from about this time on. And there were front line units using it right up until the end, U.S. in the cbi and alied,Raaf and South African in Europe but it doesn't seem like enough to soak up all that production. Maybe training units and replacement? Doesn't seem like you would need those kind of production numbers for that though.

 

[Shortround6]

P-40Ns were used for lead lease to a host of countries, they were issued to training squadrons in the US (the manual assured new pilots that if they could handle the P-40 in training they could handle whatever fighter the combat squadron they were posted to had) and as a sad commentary, of the last few hundred built, they went directly to storage/scrap. When you are building over 200 a month it is a little hard to turn off the flow over night.
P-40s flew in