P-40 what-if

[Shortround6]

The P-26 sounds right, thank you.

Aerodynamic loads increase with the square of the speed so the forces acting on the 300mph P36 would have been about 62% higher than the 235mph P-26. (level speeds not dive

THe two spar wing might be a bit lighter but both wings have to carry the same loads. If built to an ultimate load factor of 12G the wing of a 6000lb fighter is going to have another 66,000lb of sand bags, steel plates,etc placed on it, hung from it in static testing.

The faster a plane goes the more the leading edge of the wing tries to twist up. the wing structure has to resisit this twisting. A 2 spar wing cannot just use 2 spars of the same size/weight/shape as the 5 spar wing unless it uses heavier ribs or spaces them closer together and/or uses heavier wing skinning.

You aren't going to get something for nothing. THe 5 spar wing may cost more to fabricate and it might be more damage resistant. one spar damaged you 4 others carring the lad. of course with 5 spars the likily hood of one of them getting hiit goes up

There may be a weight difference, I just dont believe it is going to be as great as some peaple seem to think.

 

[Elvis]

LOL!
Leave it Shortround to turn the answer to a simple "Yes-or-No" question into a 5000 word essay.
God bless ya, Shortround.


Its ok, I'll just stay mystified.



Elvis

 

[Clay_Allison]

The P-26 sounds right, thank you.

Aerodynamic loads increase with the square of the speed so the forces acting on the 300mph P36 would have been about 62% higher than the 235mph P-26. (level speeds not dive

THe two spar wing might be a bit lighter but both wings have to carry the same loads. If built to an ultimate load factor of 12G the wing of a 6000lb fighter is going to have another 66,000lb of sand bags, steel plates,etc placed on it, hung from it in static testing.

The faster a plane goes the more the leading edge of the wing tries to twist up. the wing structure has to resisit this twisting. A 2 spar wing cannot just use 2 spars of the same size/weight/shape as the 5 spar wing unless it uses heavier ribs or spaces them closer together and/or uses heavier wing skinning.

You aren't going to get something for nothing. THe 5 spar wing may cost more to fabricate and it might be more damage resistant. one spar damaged you 4 others carring the lad. of course with 5 spars the likily hood of one of them getting hiit goes up

There may be a weight difference, I just dont believe it is going to be as great as some peaple seem to think.

I had always thought that the P-40 was similar in size to the spitfire, since it wasn't (just too big) I think it's worthwhile to adjust the requirements to emphasize speed and power loading over all other concerns.

One thing I think that would be possible is just shrinking the plane. Trimming it but keeping it balanced to the same scale. This would reduce internal fuel capacity but I am a big proponent of drop tanks and the Bf 109 made good use of them throughout the war.

The P-40 was a big sturdy plane, there's no reason not to make it a small sturdy plane with the same horsepower as the big one. It would reduce unassisted range and I'm sure shortround can come up with some other trade-offs that would have to be made, but I think it would be worth it to get a real honest-to-god dogfighter into the war in 1942.

By the way I do agree that these decisions would have to be made pretty early in the process (ca. 1937 when Curtiss was first looking at mating the V-1710 to the P-36 and reports were coming back from Spain about the Bf 109)

 

[Elvis]

Clay,

Courtesy of Warbird Alley...

Specifications: (P-40N):
Engine: 1360hp Allison V-1710-81 inline piston engine
Weight: Empty 6,000 lbs., Max Takeoff 11,400 lbs
Wing Span: 37ft. 4in.
Length: 33ft. 4in.
Height: 12ft. 4in.

]

Specifications (Mk VA):
Engine: One 1,478-hp Rolls-Royce Merlin 45 V-12 piston engine
Weight: Empty 4,998 lbs., Max Takeoff 6,417 lbs.
Wing Span: 36ft. 10in.
Length: 29ft. 11in.
Height: 9ft. 11in.

Specifications (P-51D):
Engine: One 1,695-hp Packard Merlin V-1650-7 piston V-12 engine
Weight: Empty 7,125 lbs., Max Takeoff 12,100 lbs.
Wing Span: 37ft. 0.5in.
Length: 32ft. 9.5in.
Height: 13ft. 8in

Now, what you're proposing, by shriinking down the plane, in order to boost performance, is very similar to what Grumman did in the very late stages of the war.
While the F6F was an absolute Godsend to Naval fliers all over the pacific, the fact remains that it was still a large and heavy aircraft.
Someone at Grumman mused about how much performance would increase, if they could design the smallest possible airframe that was still stout enough to handle the R-2800.
The result was the F8F Bearcat. One of the, if not THE, highest performing propeller driven airplane of the entire war (and it did serve during the war, even if only for a very short time).

...and so, again, courtesy of the good people at Warbird Alley, here are the stats comparing those two planes...

Specifications (F6F-5):
Engine: 2000hp Pratt Whitney R-2800-10W Double Wasp 18-cylinder radial piston engine
Weight: Empty 9150 lbs., Max Takeoff 15,410 lbs.
Wing Span: 42ft. 10in.
Length: 33ft. 7in.
Height: 13ft. 6in.
Performance:
Maximum Speed at 23,500 ft: 380mph
Cruising Speed at 6,000 ft: 168mph
Ceiling: 37,300 ft
Range: 1,530 miles with 150-gallon drop tank
Armament:
Six 12.7mm (0.5 inch) wing-mounted machine guns
Two 1,000-lb bombs, or six 127mm (5-inch) rockets

Specifications (F8F-1B):
Engine: 2,100hp Pratt Whitney R-2800-34W Double Wasp 18-cylinder radial piston engine
Weight: Empty 7,070 lbs., Max Takeoff 12,947 lbs.
Wing Span: 35ft. 10in.
Length: 28ft. 3in.
Height: 13ft. 10in.
Performance:
Maximum Speed at 19,700ft: 421mph
Cruising Speed: 163mph
Initial Climb Rate: 4,570 feet per minute
Ceiling: 38,700ft
Range: 1,105 miles
Armament:
Four 20mm cannon
Hard points for two 1,000lb bombs, or four 127mm (5-inch) rockets, or two 150-gal fuel tanks

Now, would the P-40, altered the same way, show similar increases in performance?
I don't know, but if someone had access to some computer similation programs, it would be interesting to find out.
Seeing how you're setting an early timeline on things this time, maybe the "P-40" (no letter designation) would be the plane to use for testing..



Elvis

 

[tomo pauk]

...
Now, what you're proposing, by shriinking down the plane, in order to boost performance, is very similar to what Grumman did in the very late stages of the war.
While the F6F was an absolute Godsend to Naval fliers all over the pacific, the fact remains that it was still a large and heavy aircraft.
Someone at Grumman mused about how much performance would increase, if they could design the smallest possible airframe that was still stout enough to handle the R-2800.
The result was the F8F Bearcat. One of the, if not THE, highest performing propeller driven airplane of the entire war (and it did serve during the war, even if only for a very short time).
...
Elvis

F8F was a great plane, but:
a) many planes that really served in war were outperforming it - 6 months, or even a full year before the Bearcat flew in units
b) war service of the plane is equal to zero

 

[Shortround6]

One thing I think that would be possible is just shrinking the plane. Trimming it but keeping it balanced to the same scale. This would reduce internal fuel capacity but I am a big proponent of drop tanks and the Bf 109 made good use of them throughout the war.

The Bf 109 did not make good use of them. It turned necessity into a virtue if you can call it that. Needing drop tanks to perform any but the most local/point defence missions might not have meet the requirement of the U.S. Fighting in the Pacific theater with a plane that had the range of a 109 would have been a bit difficult. See Spitfires in the Pacific. Sptifires could also carry larger tanks than 109s, in part because of their larger wing.

The P-40 was a big sturdy plane, there's no reason not to make it a small sturdy plane with the same horsepower as the big one. It would reduce unassisted range and I'm sure shortround can come up with some other trade-offs that would have to be made, but I think it would be worth it to get a real honest-to-god dogfighter into the war in 1942.

Since you asked

reducing the wing size, From an old book "The Airpalne and it's Engine" by Chatfield, Taylor and Ober. at least 5 edtions and can be found on E-bay for 10-20 dollars.
"A reduction in wing area of 25 percent would increase the minimum speed by 15 percent but the maximum only about 3 percent. climb is slightly increased. Take-off run is increased."

So for a 350mph airplane you can gain about 10mph top speed for about a 13 mph increase in stalling speed. You are heading for a boom and zoom plane and not a dogfighter.

A smaller plane might have a more cramped cockpit. Not as much of a problem in a shorter ranged fighter as a long range one.

There were 2 attepts at "smaller P-40s" the P-46, which was actually a bit schizophrenic in try to cram a bigger war load into a smaller airframe and the Republic P-47A.

This design (never went past mock-up) is usually glossed over in most histories of the P-47 and understandably at is bears no realtionship with the P-47B.

As originally proposed it was to weigh 4,900lbs using the V-1710-39 engine (same as P-40 D/E) and armed with the typical pair of .50 cal guns with 200rpg. The 115 sq ft wing may have posed a few problems though. With no armour or self sealing tanks ( and weight escalation) it was decided that this was not what was wanted and a revison to a 6,150lb design was made. 30ft wing span, 27'6" length and a wing area of 165 sq ft. Multiple .30 cal guns were added to the wings, empty weight was supposed to be 4,790lbs with a speed at 15,000ft of 400mph and climb to that hight in 4.8 minutes. Again climbing weight estimates and combat reports from Europe cast doubts on actual performance and wither this design was what was really wanted. Some details of this design are sketchy and conflicting.
[/QUOTE]

 

[renrich]

The F8F was not an altered F6F any more than the F6F was an altered F4F. The F8F was a completely different design other than the engine which was seriously uprated. As far as other aircraft in the same time period outperforming the Bearcat, that depends on where. The Bearcat was a 440-450 mph airplane at low altitudes and could climb like a homesick angel. I doubt any other contemporaries could do that. That type of performance is why the Bearcat has excelled on the air racing circuit.

 

[VG-33]

Del:

 

[VG-33]

Hello

Since you asked

reducing the wing size, From an old book "The Airpalne and it's Engine" by Chatfield, Taylor and Ober. at least 5 edtions and can be found on E-bay for 10-20 dollars.
"A reduction in wing area of 25 percent would increase the minimum speed by 15 percent but the maximum only about 3 percent. climb is slightly increased. Take-off run is increased."

So for a 350mph airplane you can gain about 10mph top speed for about a 13 mph increase in stalling speed. You are heading for a boom and zoom plane and not a dogfighter.

Well, after theory let's see on practice what it does to the Yak1M from the serial Yak-1.

Reduction from 17,15 to 14,85 m² ( 15% less) wing aera produced

25 mph speed increase
1-2 mph stall speed increase
20% gain in climb speed

Of course there was a 250 kg weight reduction. Small increase in wingload and P/W ratio.

The Yakovlev design bureau genious was to reduce the wing size altogether with the plane weight.

Regards

 

[Clay_Allison]

The figure I'd go for with the P-40 is a power loading of at least 0.20 hp/lb. The Spitfire, Bf 109, and Mustang were all in the .21-.23 range in later models, the Zero had a power loading of .18, the P-40 an unacceptable .14.

 

[Shortround6]

Hello



Well, after theory let's see on practice what it does to the Yak1M from the serial Yak-1.

Reduction from 17,15 to 14,85 m² ( 15% less) wing aera produced

25 mph speed increase
1-2 mph stall speed increase
20% gain in climb speed

Of course there was a 250 kg weight reduction. Small increase in wingload and P/W ratio.

The Yakovlev design bureau genious was to reduce the wing size altogether with the plane weight.

Regards

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.
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?
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?

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.

 

[Elvis]

reducing the wing size, From an old book "The Airpalne and it's Engine" by Chatfield, Taylor and Ober. at least 5 edtions and can be found on E-bay for 10-20 dollars.

"A reduction in wing area of 25 percent would increase the minimum speed by 15 percent but the maximum only about 3 percent. climb is slightly increased. Take-off run is increased."

So for a 350mph airplane you can gain about 10mph top speed for about a 13 mph increase in stalling speed. You are heading for a boom and zoom plane and not a dogfighter.

Shortround6,

Did the section of the book you quoted on the affects of shrinking down a wing mention exactly how the wing was "shrunk", for them to come to those conclusions?
In other words, was the wings proportionally shrunk in all dimensions? was it made shorter? was it made narrower, etc.
I ask, because the only thing the quote states is that the wing area is shrunk by 25%. I don't see anything on how it was shrunk.

Also, did YOU calculate the change in stall characteristics, or did you get that from the book, as well?
I ask because I see nothing quoted about a change in stall speed.

Lastly, isn't the "blueprint" for a purpose built dogfighter a plane that has a high power loading with a low wing loading...or do I have that backwards?

Just curious.



Elvis

 

[Shortround6]

No, the book didn't say how it was shrunk. I would assume shrunk in all dimensions because you do get different results from wings of equel area if they have very different aspect ratios. talking about lift caracteristics in general here. See Spitfires for changes in flying characteristics that can't quite be explained by simple changes in square footage.

I calculated the stall speed myself based on a 90mph stall speed. I may be mistaking minimum speed for stall speed

"reduction in wing area of 25 percent would increase the minimum speed by 15 percent "

You maybe correct in "built dogfighter a plane that has a high power loading with a low wing loading..."

But if you shrink the wing more than you shrink the weight you get a high power loading with a high wing loading..... or at least a higher wing loading than you started with. Please note the proposed XP-47A with it's 165sq.ft. wing would have had a higher wingloading than a P-40 operating at 8500lbs.

Minimum speed (or stalling speed, in either case you are no longer flying) changes with altitude. In the thinner air at high altitudes the plane has to fly faster to get the same amount of lift. And if you are trying to turn the minimum speed goes up again.
You might have a "vertical" dog fighter but not a "horizontal" dogfighter.

 

[Elvis]

Thanks. That's all I wanted to know.


Elvis

 

[Elvis]

...oh yeah, and y'all knew someone would bring this up...

Elvis

 

[Clay_Allison]

...oh yeah, and y'all knew someone would bring this up...

Elvis

Terrible concept. the light fighter concept is fine if you mean the lightest possible fighter that can handle your best engine.

That pathetic Bell XP-77 had a proposed power loading of .129, on par with a dive bomber.

 

[Elvis]

...tee-hee-hee.




Elvis

 

[Colin1]

Terrible concept. the light fighter concept is fine if you mean the lightest possible fighter that can handle your best engine.

That pathetic Bell XP-77 had a proposed power loading of .129, on par with a dive bomber.

I like the tricycle undercarriage
I understand that cancelled out propeller torque on take-off - not that that is likely to upset that little bird.
Don't quite understand how the cockpit ended up so far back and what were they going to gun it up with, air rifles?

 

[Elvis]

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

 

[Clay_Allison]

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

It's hindsight and all, but they did it all backwards. You start with an engine, then you tailor an airframe to it. Even though the Bf-109 was designed around the Jumo 210 and evolved to use the Db-601 it was still an inverted V-12 of the same approximate size.

We can think of quite a few planes that failed to reach production because of engine delays, and a few examples where with a proven powerplant to rely on, planes have jumped from paper to production in weeks or months.

If you rely on an experimental power plant to make your idea work you can often find yourself in possession of a windless kite.

In any case I wouldn't want to go up in a 500 horsepower egg crate to fight against real fighters.