P-40 Warhawk/Kittyhawk

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archerynut

Recruit
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Feb 22, 2009
Calgary
ever since i can remember, i have had a spot for this plane somewhere. that big intake on the bottom, the sharks mouth, it all goes together to make a plane that meant business more than anything else. all over the internet, its talked about as being one of the toughest, most reliable of the early war fighters. along its design history is talk of having been equipped with a rolls royce/packard merlin. this engine, in most cases, seemed to "make" the plane it was installed in. so why did they short change the p-40 by equipping it with the Allison instead? was it a matter of logistics or just convenience? with the merlin, it could have been a truly amazing airplane that would have performed brilliantly at ANY altitude that combat would have taken place. to look back at its combat record, i can't help but think the quality of the pilot is what made the p-40 what it is thought of being today. they had the training and they "had right on their side"!
 
Allison was American engine. So, it was just natural to install it into US airframes.

I'd love to see what a R-2600 could do in the P-36 offspring, rather then the Merlin in the same plane.
 
The problem with 'spots' is the tendency to look at the object of your affection through rose-tints

The Merlin was fitted, in the P-40F and L versions, with the L making vigorous attempts to shed weight. All of this certainly improved the P-40 but I would stop short at calling it an 'amazing aeroplane that would have performed brilliantly at any altitude'. By 1943, the P-40 was an old, heavy design, outmoded by more modern a/c that more accurately addressed the new requirements of aerial warfare. The P-40 stayed in production far longer than it should have done largely because it was cheap, not because it was amazing or brilliant.

The P-40 wasn't short-changed, the Allison was the perfect engine to address the requirements that the a/c was designed for - low-level engagements. The Allison was a good low altitude engine at the beginning of the war and returned with a vengeance at the end of the war in its -119 configuration to become a good high altitude engine.

You're not alone in your affection for the P-40, it was an honest airplane and it was there when it was needed.
 
Will it fit? The R2600 radial is relatively large and heavy.

R1830 twin radial.
48.03 in diameter.
1,250 lb dry weight.

R2600 twin radial.
55 in diameter.
2,045 lb dry weight.

Allison V1710 liquid cooled V12.
41.18 in height.
1,445 lb dry weight.
 
Russians managed to re-engine the LaGG-3 with a heavier and bulkier engine in order to get the La-5; plus the one extra cannon weighted more then 2 Skash MGs that got removed.
Dry weight: M-105: 620 kg (1,365 lb) (LaGG-3)
Dry weight: M-82-112 model: 860 kg (1,894 Ib) (La-5)
Japanese have also went through similar trouble to re-engine the Ki-61 to produce Ki-100.

It would require some thinkering to mount the R-2600 in the P-36 airframe, but that's why we have engineers. The removal of engine MGs and the sinchronisation gear would help too.
 
Another factor that led to the limited production of P-40Fs (around 1300 units) was that by the time the Packard V-1650-1 engine had already been prioritized for use in the P-51 Mustang.
 
tomo pauk said:
It would require some thinkering to mount the R-2600 in the P-36 airframe, but that's why we have engineers. The removal of engine MGs and the sinchronisation gear would help too.
Click to expand...

The R-2600 was about 800 lbs heavier than the r-1830 and 6.5" larger in diameter. With the assoiated structural enforcements we do talk about a netto weight increase in the area of 1500 +-100 lbs. in total for the P-36 with r-2600. More serious are the unadressed cg-shift fwd., which would tend to make the P-36 very nose heavy. It requires basically a complete new design of the fuselage.
The P-36 would then weight in loaded over 7.500 lbs! Wingload would increase by 25% from 25.3 to ~31.6lbs/ft^2. Takeoff and landing speed inreases, handling will be more difficult with longer turn times and more severe torque effects during taxiing.
On the plus side You will have 1600hp instead of 1050/1200hp aviable.
Power/weight ratios would be basically unchanged due to the increased weight of the r-2600 installation.
Frontal area and wetted area are now significantly larger and thus more drag will be generated by the same airframe. It´s difficult to project a top speed but judging from France´s disappointing experiences with the Br-695 series and these engine changes, I doubt that You would see drastically improved performances unless a major aerodynamic clean up takes place. You end up with a plane which has basically the same performance but is more difficult to handle and consumes more fuel (=less range).
 
Okay,
The R-2600 weights some 360kg more then the R-1830. Now we need to reduce that difference, since the hull MGs, their ammo and the sinchro gear are deleted. My guess is that we save around 100 kg, so the difference is about 260 kg. Much smaller then proposed 680kg, and very much close to the LaGG-3/La-5 conversion.

Of course, we do have the added weight that is not at the centre of gravity of plane. Luckily, the added weight is pretty close to the CoG, so we'll compensate it by adding removing lighter stuff* aft of the pilot seat.
My guesstimate is that the plane would be 25-30% heavier then P-36 (with additional enforcements, wing guns engine added weight), but with 50-60% more HP.


*armor, radio, fuel etc.
 
The added weight is IN FRONT OF THE COG. Removing weight from BEHIND OF THE COG does make things worser! You need to elongate the hull and install dead weights (armour?) as far aft as possible to counter this. Or You move the wing forward.
Remember also that it´s engine dry weight, not netto weight increases. The support frames needs to be enforced to cope with the heavier loads and torque effects produced by the larger engine, too.
 
I think the 30L R1830 engine could have been developed further. With a better supercharger and other improvements you could probably achieve 1,400 hp. In addition you clean up the P36 airframe to make it more streamlined. Together these improvements should push the top speed up to about 375mph. This keeps the P36 competitive through 1942.
 
Because during the war, we were pumping as much equipment off the assembly lines as quickly as possible, thus every single piece of equipment was strictly prioritized.
The Merlin's went into the P-51, because it was just a better and faster airplane that could pack a heavier punch.
Even with the Allison, early P-51's were faster than contemporary P-40's...and the P-40 had already been through a few "developmental changes" by that time.
FWIW, the Merlin that did make it into the P-40's were lower powered versions, making about 1300HP, and they didn't last long in the P-40. I think by the "K", they were back to outfitting them with Allisons.
Why? I don't know. Probably more "prioritizing".
The P-40 was a good honest airplane and one of the most successful designs of the war.
Early on, when we really had nothing else, it delivered a heck of a punch and gave us time to get our inventory "up to speed", but in the end, the 51 could just do everything better...outfitting it with the Merlin was just icing on the cake.



Elvis
 
What do you think of outfitting that P-36 with an R-2000?
1425HP in the same sized package as the 1200HP R-1830.
The problem with all of this, may lie in sheer aerodynamics.
I know the Navy tried outfitting the R-2000 to the F4F (which also used the R-1830) and found that performance just didn't change enough to make the swap worth it.
It did help lead to the development of the F6F, though.
I wonder if the same would hold true with the P-36.
....remember, one advantage the P-40 had over the 36 was much less frontal area, thus it was more aerodynamically efficient.



Elvis
 
Sounds good to me.

However you still need to make the P36 more aerodynamic if you want it to have a higher top speed. Otherwise you will only improve the acceleration and rate of climb.
 
davebender said:
Why was ANY American aircraft equipped with the Allison rather than the superior RR Merlin engine?
Click to expand...
Allisons were in fact available in quantity, and it was not a bad engine in its' own right. I'd say the late Allison mark that powered the P-82 Twin Mustang was as good as any Merlin. The real question is why the stupid USAAF delayed domestic development of a good two-stage supercharger.
 
A later mark of 1830 would have been fine, it developed 1200 horsepower in the F4F with the -86.

The P-40 was ridiculously overweight for a fighter. It was a ground attack plane with some self defense capability from the beginning.

If the P-36 had been given later marks of engine and not overarmored so badly it might have been a better performer than the P-40 in fighter vs. fighter duels.
 
davebender said:
Sounds good to me.

However you still need to make the P36 more aerodynamic if you want it to have a higher top speed. Otherwise you will only improve the acceleration and rate of climb.
Click to expand...
True, thus my comments on aerodynamics.
...maybe if you used the big R-1340/R-2000 cylinders with the bottom end of the R-1535.
This would create an "R-1886" (possibly rounded up to "R-1890", for publications sake).
I know the Twin Wasp Jr. was about 6" narrower than the Twin Wasp, so if the fueslage was left alone, this would mean the cowling could be built in a more conical shape, aiding aerodynamics.
How much of a difference it would make overall?
I don't know.



Elvis
 
later in the development, like after they moved the machine guns from the cowling to the wings, i read they added almost 200 pounds of armour to the airplane, around the cockpit area. what would this have been? like heavy steel plating or something else bullet/shrapnel resistant?
 
Was the PW radial suitable for a Fw190/Sea Fury style close cowl? That was found to be the most aerodynamic way to cowl a big radial, maybe a model project in there?
 
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