P-40 what-if

[tomo pauk]

Very true, Clay.
Many US planes were 'designed' with experimental engines in mind, only to found out that it was a complete waste of time money. The Germans also relied at the Jumo 222, with pathetic results after all.

 

[Shortround6]

The proper way to do it would be to start with the paylad (weapons) desired and the performance that is wanted.
As in " we want a 1000lb weapons load to go 350mph at 20,000ft and climb to 20,000ft in 8 minutes. Range to be not less than 500miles at 200mph. Landing and take-off speeds to be compatable with standard existing airfields. Design Structural strength is to be 'X' Gs positive and 1/2 'X' Gs negative with an ultimate strength of 'X'+50% to be equiped with standard instraments and radio YYY, etc."
Designer then tries to figure out what engine and what sized airframe will give the desired performance. Sometimes the lowest price will also enter into it.
In some cases it took a second engine choice to make the airplane work (both Zero and Hellcat).

It has been said that combining a new airframe with a new engine is a recipe for failure

 

[Shortround6]

The concept was sort of an "essentials only-type" fighter plane. Guns and that's it.
They wanted to do the smallest package possible, so it was developed from the standpoint of a "formula 1" type of race plane, modded for military use.
It was to be powered by a small V-12, thus the reason for setting the pilot so far back.
They promised "500 cubic inches, 500HP", but that version couldn't be developed in time, so a lower (350) HP version was used for testing instead.
Performance suffered because of this and the plane was passed up for that reason..

...or so I've heard/read

Elvis

Could you please give a source or two for this?

I have developed an interest in this airplane due to a long argument about it on another board (I was against it) and I am rather amazed at the amount of contradictory and/or down right false information about on the web and in some books.

 

[Clay_Allison]

The proper way to do it would be to start with the paylad (weapons) desired and the performance that is wanted.
As in " we want a 1000lb weapons load to go 350mph at 20,000ft and climb to 20,000ft in 8 minutes. Range to be not less than 500miles at 200mph. Landing and take-off speeds to be compatable with standard existing airfields. Design Structural strength is to be 'X' Gs positive and 1/2 'X' Gs negative with an ultimate strength of 'X'+50% to be equiped with standard instraments and radio YYY, etc."
Designer then tries to figure out what engine and what sized airframe will give the desired performance. Sometimes the lowest price will also enter into it.
In some cases it took a second engine choice to make the airplane work (both Zero and Hellcat).

It has been said that combining a new airframe with a new engine is a recipe for failure

I know you start with a "requirement" issued from the government, but if you want a plane that can be delivered on time and in quantity, you'd better start your program to FILL that requirement with a power plant that you know will be there.

 

[Shortround6]

I know you start with a "requirement" issued from the government, but if you want a plane that can be delivered on time and in quantity, you'd better start your program to FILL that requirement with a power plant that you know will be there.

Like the above mentioned Zero and Hellcat?

Both prototypes used engines that were in production yet didn't deliever the required performance and had to switch to another engine.

Or the FW 190?

Engine it was designed for never made it into production.

P-39, P-40 and P-38 were designed around an engine that had at least passed a type test even if it wasn't really in "production". 7 engines delivered in 1937 and 14 in in 1938.

Or the Hawker Typhoon/Tornado design started with the Sabre, the Vulture was added early in the design proccess, first flew with the Vulture but we all know how that engine turned out Later proposals include 3 additional engines, one of which was the Bristol Centaurus. THe last made it to hardware stage on the Tornado airframe. Strange that the final fighters produced of this family used the Centaurus.

THis is just fighters somewhat of the top of my head.

Some goverment requirements specified which engine was to be used.

 

[Clay_Allison]

Like the above mentioned Zero and Hellcat?

Both prototypes used engines that were in production yet didn't deliever the required performance and had to switch to another engine.

Or the FW 190?

Engine it was designed for never made it into production.

P-39, P-40 and P-38 were designed around an engine that had at least passed a type test even if it wasn't really in "production". 7 engines delivered in 1937 and 14 in in 1938.

Or the Hawker Typhoon/Tornado design started with the Sabre, the Vulture was added early in the design proccess, first flew with the Vulture but we all know how that engine turned out Later proposals include 3 additional engines, one of which was the Bristol Centaurus. THe last made it to hardware stage on the Tornado airframe. Strange that the final fighters produced of this family used the Centaurus.

THis is just fighters somewhat of the top of my head.

Some goverment requirements specified which engine was to be used.

I'm not saying that these things never ever worked out. The M.B. 2-5, the entire hyper-engine project (XP-55, 49, 67), P-75, XP-58 are all designs that suffered at the hands of experimental engines.

 

[Elvis]

Clay,

You say you start with an engine and design a plane around it.

Actually, you start with a mission or a mission requirement and then you see if you have anything in the exisiting inventory that will satisfy that requirement/mission.
If you have nothing, then you see if you can't modify something in the existing inventory to satisfy the requirement/mission.
Having failed that, then, you compile the specs for filling that requirement/mission and send out the offer to your known manufacturers and they design something they think will fill that requirement/mission (and I'll not travel the path that results from none of your known manufactures having the ability/knowledge to design something to satisfy the requirement/mission. However, that is an additional option).
Then you decide who best fills the requirement, have trials, then you induct the winner into your inventory.

...at which point you start the whole process over again when you find that in the meantime, the mission / mission requirement has changed and the recently inducted design is no longer suitable for anything other than a now obsolete mission / mission requirement.
-----------------------------------------------------------------------------

Shortround6,

Re: Bell XP-77 info.

No single, quoteable source.
Just info I've gleaned over the years.

Times change and half of what we learned as "fact" in our youth turns out to be "not fact".
Forgive me if I haven't kept up with the latest findings.

Did I read your last post correctly, though?
You state that you've recently gained interest in the plane, due to misinformation you're reading about it on the web?
.....wouldn't "recently gained interest" mean you didn't really know anything about it before, mainly due to lack of interest, but am now gaining information on?
In which case, how do you know the information you're reading is incorrect and how do you know the information you're using as a comparitive is correct?




Elvis

 

[Shortround6]

Elvis,
By recently I mean in the last year to year and half.

Some mistakes can be pretty obvious. Like one book claiming the plane was to be armed with two 20mm cannon and two .50cal MGs. Nobody else makes such a claim and trying to figure out were the guns would go makes it pretty clear that this is a mistake.
Other claims don't fall on a common time line. Like claims the plane did 330 mph while armed with a single 20mm cannon and two .50cal MGs. The requirement for the cannon was dropped to allow for a bomb or drop tank to be carried almost 2 years before the first prototyype even flew. Peaple may argue over wither the prototype actually carried any guns at all but why would it carry the 20mm on test flights almost 2years after it was decided not to install it at all?
I have also tried to gather as much information as I could about the Ranger engine due to an arguement on another Board about light fighters in general. For sources on this I rely on Several old editions of "Jane's all the world's aircraft", several editions of Wilkinsons "aircraft engines of the World". FAA type cetificates on line and some other old books about airplane engines. By double checking such information one can usually spot misprints like rated altitude being off by 10,000ft or so
In another thread on this board I noted that the climb rates for the XP-77 don't seem to agree with themselves. An Intial climb rate of 3,600fpm and time to 9,000ft of 3.7 minutes just don't fit together. Unless the intial climb was done at a power setting that could only be held for one minute and the remaining time to 9000 ft had to be done at a much lower power setting?
Some accounts say the the design was called the "Tri-4" for "400 hp, 4000 pounds, 400 mph". but even in 1936 the Ranger was rated at 420HP and 1941 it was rated at 520HP at 9,600ft. Where the 400hp comes from is a mystery to me. Most acounts claim the Ranger with a special superchager was supposed to supply either 500 or 520 hp at 27,000ft which doesn't explain the "Tri-4" either.
If the engine used was supposed to supply 520hp at 12,000ft then why is the max speed given at only 4,000ft in much thicker air? The plane should have gone faster in the less dense air at 12,000ft unless there was a problem with the engine?

Maybe there are expantions for these questions and I just haven't seen them

 

[Clay_Allison]

Some mistakes can be pretty obvious. Like one book claiming the plane was to be armed with two 20mm cannon and two .50cal MGs. Nobody else makes such a claim and trying to figure out were the guns would go makes it pretty clear that this is a mistake.

maybe confusion with the vague and mysterious Tucker XP-57?

 

[Shortround6]

Possiable but book devotes half a page of text to the XP-57 and a full page 3 view drawing.
Gives two armament options for the XP-57.
Almost a full page of text to the XP-77, a full page 3 view and 3 photos.

 

[Clay_Allison]

Possiable but book devotes half a page of text to the XP-57 and a full page 3 view drawing.
Gives two armament options for the XP-57.
Almost a full page of text to the XP-77, a full page 3 view and 3 photos.

I still say you never go with lesser engines. it's a waste of production capacity. "Cheap" Aero engines are still too expensive and the workers building them need to work on real engines.

Building a light fighter is great, just make it the lightest package you can that has everything you need, like the Zero and the Ki-43.

 

[Elvis]

Shortround6,

Thanks for clarifiying your sources.
I see what you're getting at.
Yes, definately some descrepencies.
As for testing an engine rated @ 12K ft, at 4K ft., I've heard many times, from different sources, that the engine that was supposed to go in the XP-77 wasn't available at the time testing was scheduled, so they went with a less powerful version.
The jist I got was that it was hoped that the more powerful engine would be available by the time testing ensued.
That could explain why the plane was tested at the lower altitude, although, that does seem like a really low test altitude.
Weird.
-------------------------------------------

Building a light fighter is great, just make it the lightest package you can that has everything you need, like the Zero and the Ki-43.

Yep, I think that's the best approach.



Elvis

 

[Altea]

Going from therory to practice always has a few problems.
Given the usual + or - of a few % in both individual aircraft wieght and engine power due to production tolerances comparing the results of just one set of numbers and declaring the therory bad doesn't seem to fair.

It's 100% true, i always knew that. It's why it's so tiresome ans uselessness to compare aircraft performance datas.
http://www.ww2aircraft.net/forum/aviation/late-war-fighter-competition-20794.html
Now try to explain it to your friend Soren, einmal!

Especially considering the Russians seemed to have a fair degree of trouble just getting their production planes to perform up to prototype standards. Just which Yak-1 is being compared?

Not only them, it'an universal problem. It's why it makes sens only if you compare with the Yak-1 you have modified. And with some approximation (40kmh~25mph).

Were there anyother changes to the plane that might change the drag, like different oil cooler location or ducting, a different propeller and/or spinner or other modifications besides a better fit and finish on the Prototype Yak-1M vrs a series built aircraft?

Early Yak-1M, did not recieved it's wing tunnel radiators at time, and was tested without them AFAIK in february-march 1943, keeping the Yak-1 one. But there is a discuss about that from specialists...It's true, the Yak-1M "dubbler" was flying faster, 656kmh insted of 638, than our's first Yak-1M.

Doesn't take a lot of genious to replace the wooden longerons with metal ones as the metal became more available later in the war. According to one book this accounts for over the half the weight difference.

I'm not sure, since the La-5 with the more sturdy and big wing gained only 80 kg from that. But it's true that all proportions keeped, a 8% smaller wing should be 26% lighter. It makes 420 - 440 kg from 530-560kg weight reduction.

It worked elsewere, with due reservation of course:
109F/109E.
Il-10/Il-2
D-550/D-520

Anyway, you could turn your problem as much as you like. To overcome the 109F, from the P-40 you have to make a plane smaller and lighter, with some sacrifices in weapons, range, protection matters. Or use a powerfull engine that not exists.
It's much more difficult to gain on the Cd, even impossible.

Regards

 

[Shortround6]

Shortround6,

Thanks for clarifiying your sources.
I see what you're getting at.
Yes, definately some descrepencies.
As for testing an engine rated @ 12K ft, at 4K ft., I've heard many times, from different sources, that the engine that was supposed to go in the XP-77 wasn't available at the time testing was scheduled, so they went with a less powerful version.
The jist I got was that it was hoped that the more powerful engine would be available by the time testing ensued.
That could explain why the plane was tested at the lower altitude, although, that does seem like a really low test altitude.
Weird.
Elvis

According to most sources the engine they hoped for was supposed to give 500-520hp at 27,000ft.
The engine they fitted was supposed to give 520 at 12,000ft for one minute.
Unless they got a dog. It was a standard Navy engine fitted to the Curtiss SO3C if I have things right.

 

[Shortround6]

It worked elsewere, with due reservation of course:
109F/109E.
Il-10/Il-2
D-550/D-520

Anyway, you could turn your problem as much as you like. To overcome the 109F, from the P-40 you have to make a plane smaller and lighter, with some sacrifices in weapons, range, protection matters. Or use a powerfull engine that not exists.
It's much more difficult to gain on the Cd, even impossible.

Regards

Actually as far as the 109F/109E goes there were a number of differences that would affect drag besides the wing.

I am not sure about the IL-10/Il-2 but in the D-550/D-520 comparison the D 550 used a diifferent engine (higher power) in addiation to a few other changes, like a retractable tail SKID instead of a tail wheel.

For a P-40 to best a 109F you need to do both.
Make the P-40 smaller and use a more powerful engine that did not exist at the time.

 

[Elvis]

According to most sources the engine they hoped for was supposed to give 500-520hp at 27,000ft.
The engine they fitted was supposed to give 520 at 12,000ft for one minute.
Unless they got a dog. It was a standard Navy engine fitted to the Curtiss SO3C if I have things right.

Shortround,

As I stated before, all I've ever heard was that the engine they wanted to use wasn't available by the time testing was to commence.
However, I failed to mention that they used the less powerful version, becuase it was already available.
AFAIK, the engine used wasn't a "dog", it was simply less powerful than the version they had designed the plane for.
At the time, they hoped it was "good enough" to get it through the trials period, however, it wasn't and thus the plane failed to pass because it simply couldn't generate the performance required by the Army Air Force for its mission.
Whether those are the engines you mentioned or not, I don't know.



Elvis

 

[Clay_Allison]

How much weight could be saved by stressing the P-40 to only 10 g rather than 12 g ultimate?

 

[Markus]

See the idea of installing a V-1710 with an auxillary stage supercharger has been discussed already.
To save weight I suggest removing two of the six .50 guns. Each gun weighs 70lb, one round 0.3lb. With 235 rounds per gun that saves a total of 280lb. What about laminar flow wings? C&W had designed some for the XP-60.

 

[Colin1]

What about laminar flow wings?

What effect do you think the undercart arrangement is going to have on this? Or are we re-doing that as well?

 

[Shortround6]

See the idea of installing a V-1710 with an auxillary stage supercharger has been discussed already.
To save weight I suggest removing two of the six .50 guns. Each gun weighs 70lb, one round 0.3lb. With 235 rounds per gun that saves a total of 280lb. What about laminar flow wings? C&W had designed some for the XP-60.

The Curtiss company was designing the XP-60 as a P-40 replacement. See:

Factsheets : Curtiss XP-60