R-2600 table

[tomo pauk]

I've taken 55500 ft as the altitude where power drops to 0 HP, ie. 0%; the altitude for 100% power (1450 HP in 2600-13 case) is 13500 ft, as shown at latest table. The lines shouldn't be paralel, but set to converge at those 55.5 kft.

From the performance graph drawn @ US 100K book, P-40K climbs 2000ft/min @ sl ( MIL rating; R-2600 has ~50% advantage under 7-8K here, so it's 3000 ft/min on paper for such 'P-40'), achieving 2250ft/min @ 10K (2.7-2.8 kft for R-2600?), and then slowing to perhaps 1500 ft/min @ 20K (1900 ft/min for 2600). Good as P-38G under 15K, way better than all P-39 @ MIL, nothing to give to P-47 till 1944, under 15K. Better than Allison Mustangs. Comparable with F-4U prior 1945, F-6Fs, or with light F4F-3 (besting F4F-4, of course).
Such naval planes took 8-10min to climb to 20K; 4-6 min less than P-40K. Quite the difference.



Apart from beating 109/Zero @ climb contest (a very small % out of, perhaps, 170 000 of allied fighters produced between 1939-44 was capable to do that anyway; none before Spit IX arrived?), there is a whole bunch of other applications where a rate of climb can be put to a good use, esp. if it's 25% better than what was available yesterday. Or 50% @ really low level.

edit:
I've taken your advice; the red line shows power for R-2600-13 from 2nd FTH & above, blue represents V-1710-39. 900 HP vs. 1200+, at 18.5K for example - it's 1/3rd, not 1/4th bonus. Even the -8 has 25% more power.

[Shortround6]

Yes the R-2600 has more power, it also has more drag.
For a reality check try potting the Merlin V-1650-1 as used in the P-40F. 1120hp at 18,200ft.
Please note that at 20,000ft the "F" could be 40mph faster than an "E". If the R-2600 cannot out perform the "F" by a clear margin it has little or no point.
As far as low altitude goes the -39 engine was finally approved for a WER of 1470hp at sea level. I am not sure what some of the squadrons were actually running before "official" approval came through.
P-40Ks started to be delivered in May of 1942 with -73 engines. These were the engines rated at 1325hp for take off and a WER of 1550hp at sea level. Again "official" approval for this rating was delayed. Altitude performance was unchanged but low altitude performance compared to the R-2600 version shouldn't be a lot different.
Most P-40 performance specs are without WER ratings and climb performance at much over 10,000ft are suspect as climb tests were conducted at military power for the first 5 minutes and then the engines were throttled back to 2600rpm and 38.5in ( under 4 1/2lbs boost) manifold pressure for the rest of the climb to altitude test.

"E"s are coming of the production line in Aug, 1941. "F"s in Jan 1942 and "K"s in May of 1942. "F" prototype flew in Nov 1941. When did work actually start (drawing board) on these Versions and when would the decision to use the R-2600 have to be made? Especially since it would require much more redesign.

[gjs238]

R-2600 powered Boeing 314 Clippers were criss-crossing the Pacific and Atlantic prior to 12/7/41.
Just can't help but wonder that there was potential for an early-war R-2600 powered fighter.
It wouldn't have been a late-war R-2800 beater, but it could have been an early war R-1820/R-1830 beater.

[tomo pauk]

As for 'my' P-40', it would've had R-2600 from day one; meaning: no V-1710s here.

Advantages vs. P-40s you've mentioned:
-vs. F: available 18 months earlier
-vs. WER-capable ones: 1700 HP vs. their 1470/1550; all official & documented; available one year before WER for V-1710s

All of that with 'bomber engine' mounted as-is. No tricky cowlings, no WER (yet).

Yes the R-2600 has more power, it also has more drag.

We all know that

[Shortround6]

Uh, Tomo, 5th production BA series R-2600 isn't delivered until June of 1941. Hardly 18 months before the P-40F. 443 are delivered in all of 1941, 206 of them in Dec.
The "A" series R-2600 offers 1400hp at 11,500ft. 22% more power than the Allison in an P-40E for over 20% more drag. Performance over the Allison not looking good here.
In 1940 Allison built 1149 engines compared to Wright building 1921 R-2600s. In 1941 the numbers were 6402 Allison's compared to about 7500 R-2600s of both types. The 1700hp BA's were built in a brand new factory in Cincinnati.

The point of the "F" comparison is that if the "F" couldn't do the job needed of air superiority fighter given it's power at altitude, why should we believe the R-2600 version is going to do any better?

[tomo pauk]

R-2600-13 (red, data from latest table) vs. 1610-1 (green, data from graph from US 100K). No competition 'till 10K, with another area of large advantage from 13-17K. In other words, when P-40F arrives at a favorable altitude, 'my' P-40 is already there.
Similar advantage has R-2600 "A" series vs. contemporary V-1710s, continuing equally above 15K (unlike for V-1610).

[gjs238]

If the V-1710 was so much better than the R-2600 (and I'm not saying it wasn't/isn't), then why didn't they use it in lieu of the R-2600 in all applications?

[Shortround6]

Congratulations, you have a one trick pony. It can out climb a P-40, not exactly a ringing endorsement. It can't out run one. Will the dive be any better? It can't out turn the P-40.
And lets examine the climb part a bit more.
Engine is either 600lbs heavier than the Cyclone 9 used the Mohawk or 300lbs or so heavier than a P-40 engine and radiator. It needs a bigger prop, about 440lbs for another 60lbs or so over the P-40E. Fuel could be tricky. with 22% more drag (minimum) you either cruise slower, or for less time or you carry more fuel. A P-40 used about 100-112 G/H at max continuous power (1000hp) while the R-2600 could suck down 180G/H at max continuous (1350HP). The R-2600 could be throttled back to about 1000hp for 115 G/H But that extra drag is going to slow the plane down. Military power for the Allison (1150hp) is about 132 G/H while the R-2600, to use it's 1700-1450hp is sucking over 200G/H. If you want to equal the range or endurance of the P-40E you need 25-40 gallons more internal fuel. Another 150-240lbs not including tanks which can easily go another 75-125lbs.
Using drop tanks only gets you so far. Assuming full P-40E load of 150 US gallons (including rear fuselage tank which may be a no-no for combat) the R-2600 will suck down 17.5 gallons in 5 min for combat, it will suck down another 60 gallons in 20mins at max continuous leaving 50 gallons for about 1 hrs flight at most economical (hope you are out of the combat zone) and leaving 22.5 gallons for reserve and landing (just under 1/2 hr) We haven't added in a bigger oil system either.
Will the US Army buy the lower "G" load limit caused by the extra weight or will they insist on beefing up the structure and adding a bit more weight. Unless you really cut guns and ammo you are going to hit 8-10% heavier than the P-40E real quick. Extra drag in the climb and 10% more weight may make those climb figures look not so good. Better than a regular P-40 yes, but enough to take on a new role instead of being in the same situation?

[Shortround6]

If the V-1710 was so much better than the R-2600 (and I'm not saying it wasn't/isn't), then why didn't they use it in lieu of the R-2600 in all applications?

The V-1710 is better in a fighter, with a bomber you need all the help you can get taking off. You also have enough more drag (either with a twin or a naval torpedo/dive bomber) that the extra frontal area of the R-2600 wasn't that big a deal. The Avenger had a bomb bay under the crew that could house a 22.5in torpedo with the doors closed. It also had a power turret for the rear gunner and a wing with more square footage than an A-20. Sticking a pointy nose on it was like putting lipstick on a pig. A B-25 has a fuselage that will seat two men side by side, two engine nacelles that hide really big tires and gun turrets top and bottom on early ones, OK the bottom one was supposed to retract again enough drag that the engine installations were no longer the major cause of drag. Again, with a 34,000lb plane you need all the power you can get.

Fighter designers jumped over the R-2600 for the R-2800 because, if you were going to bludgeon the air into submitting, you might as well use an engine with 92% of the frontal area of the R-2600 and 250-300 more HP.

[tomo pauk]

Congratulations, you have a one trick pony. It can out climb a P-40, not exactly a ringing endorsement. It can't out run one. Will the dive be any better? It can't out turn the P-40.

Out-climbing another plane (even if that's P-40) is good thing in my book. I'd say it's capable to outrun the P-40, ditto for out-diving it.

And lets examine the climb part a bit more.
Engine is either 600lbs heavier than the Cyclone 9 used the Mohawk or 300lbs or so heavier than a P-40 engine and radiator. It needs a bigger prop, about 440lbs for another 60lbs or so over the P-40E.
Fuel could be tricky. with 22% more drag (minimum) you either cruise slower, or for less time or you carry more fuel. A P-40 used about 100-112 G/H at max continuous power (1000hp) while the R-2600 could suck down 180G/H at max continuous (1350HP). The R-2600 could be throttled back to about 1000hp for 115 G/H But that extra drag is going to slow the plane down. Military power for the Allison (1150hp) is about 132 G/H while the R-2600, to use it's 1700-1450hp is sucking over 200G/H. If you want to equal the range or endurance of the P-40E you need 25-40 gallons more internal fuel. Another 150-240lbs not including tanks which can easily go another 75-125lbs.
Using drop tanks only gets you so far. Assuming full P-40E load of 150 US gallons (including rear fuselage tank which may be a no-no for combat) the R-2600 will suck down 17.5 gallons in 5 min for combat, it will suck down another 60 gallons in 20mins at max continuous leaving 50 gallons for about 1 hrs flight at most economical (hope you are out of the combat zone) and leaving 22.5 gallons for reserve and landing (just under 1/2 hr) We haven't added in a bigger oil system either.
Will the US Army buy the lower "G" load limit caused by the extra weight or will they insist on beefing up the structure and adding a bit more weight. Unless you really cut guns and ammo you are going to hit 8-10% heavier than the P-40E real quick. Extra drag in the climb and 10% more weight may make those climb figures look not so good. Better than a regular P-40 yes, but enough to take on a new role instead of being in the same situation?

While I do appreciate the analysis:
Planes with substantially more powerful engines tended to be heavier, draggier & suck more fuel vs. lighter & cleaner ones. Yet, those planes were favored vs. lighter & cleaner competition in most of the cases.

[davparlr]

In my opinion, the discussion is on the wrong airframe. The P-66 with a similar engine as the P-36G, was almost 20 mph faster and climbed about 500 ft/min more than the P-40. Now put in the 2600 into the P-66, which should not be any more difficult than putting in a V-1710 in place of a PW on the p-36. The added 30 to 40% power should easily off set the added 750 lbs of weight and slight increase in diameter, increasing climb and top speed. The similar designed F4U-1 with 200 more hp at altitude was capable of 417 mph. This configuration could have indeed been a formidable competition to the Bf-109 and maybe the Fw-190.

[Shortround6]

Tomo, go back to the Hawk 75A-4. 323mph at 15,000ft with a Wright Cyclone 9 (G205A) giving 1200hp at sea level and 1000hp at 14,200ft. using the cube law for power needed, it would have needed 1331hp to do 355-356mph. That is with absolutely no increase in drag. Considering the increase in weight and drag the likelihood of a R-2600 powered Hawk getting past 360mph at 15,000ft seems remote.
A Commercial Hawk with a Cyclone G105A engine giving 1100hp Military at 1500ft was good for 258mph at sea level. Trying for a 20% increase in speed (310mph) would require 1900hp.
Now maybe I am misinterpreting the power (no Military rating when the brochure was put out?) and the plane did 258mph with the rated output of 900hp. It still needs 1550hp to do 310mph at sea level in that case. Once again with the increase in weight and drag of the R-2600 I don't see any real advantage over the P-40.
Why don't you figure the weight of your R-2600 Hawk. Use the weight figures from the H75-A manual on this website and the figures in "Americas Hundred Thousand" for parts of the P-40, some better weight figures for the Cyclone 9 engines can be found in the Buffalo section of the book.

[Shortround6]

In my opinion, the discussion is on the wrong airframe. The P-66 with a similar engine as the P-36G, was almost 20 mph faster and climbed about 500 ft/min more than the P-40. Now put in the 2600 into the P-66, which should not be any more difficult than putting in a V-1710 in place of a PW on the p-36. The added 30 to 40% power should easily off set the added 750 lbs of weight and slight increase in diameter, increasing climb and top speed. The similar designed F4U-1 with 200 more hp at altitude was capable of 417 mph. This configuration could have indeed been a formidable competition to the Bf-109 and maybe the Fw-190.

P-36G or P-36C ?
The R-2600 is 6in bigger in diameter and 500lbs heavier dry. 6in on diameter isn't exactly slight. it is the difference between 12.8sq ft of frontal area and 16.1 sq ft.
a few numbers for comparison.
P&W R-1830 at 1200hp----95.2hp per sq/ft of frontal area.
Wright R-2600 at 1600hp--99.4hp per sq/ft of frontal area.
Wright R-2600 at 1700hp--105.6hp per sq/ft of frontal area.
P&W R-2800 at 1850hp----125hp per sq/ft of frontal area.
P&W R-2800 at 2000hp----135hp per sq/ft of frontal area.

Now I will certainly admit that even early war cowlings streamlined things so the actual difference was edit> NOT< edit quite as bad as these figures show but it is not hard to see why the R-2600 was skipped over as a fighter engine.

As far as the "similar designed F4U-1 with 200 more hp at altitude was capable of 417 mph" goes the F4U-1 had a lot more than a 200hp advantage at altitude. at 16,000ft (not including ram) it was good for 1800hp for about a 375hp advantage over Tomo's chart. At 21,000ft (no ram) the F4U-1 was making 1650hp for an almost 550hp advantage. 1650hp vs just over 1100hp.

[elbegaio]

Hi guys, I know i'm a bit late since this conversation dates back to may, but I saw that you published the operating limit chart of wright r-2600-8. I'm working on a project of a flying boat inspired by the Boeing 314 and I need the same chart referred to wright r-2600-3. I searched everywhere on the web, so I ask you if can give me information about where to find this graph (possibly without paying 300$ dollars to buy strange manuals of 1935).

[post76]

i thought military rating was a 15 minute output rating, while WEP or take off power was usually considered a 5 minute rating.
The WEP rating typically gives a lower FTH.


It also had me thinking more of heat, something very relevant to the 5 minute rating.
The V engine has a water cooling system, which for overheating is going to give it a bit more time in the red.
The engine might get hot and overheat but nothing cooks until the water boils off, ie the engine becomes a pressure cooker, and usually you seea head gasket go or hose blow open before any other damage occurs. You can also warp heads and other parts by running hot.
After the water goes, then the oil cooks and the viscosity breaks down to where engine parts start grinding.

In a radial, there is no water to boil off, so the break down of oil viscosity happens much faster and cylinder heads are much more sensitive to damage. Also engine oil is a more of a mixture that burns with the fuel than something that cycles through, if i understand it correctly.
Holding your engine in the red would not be advisable. The advantage is that the engine will also cool off relatively sooner.
In a water cooled engine you'd have to wait for the coolant to reach a "normal" temperature setting which is dependant on radiator efficiency.
If overheating blows a hose, or gasket, you're screwed. A radial just needs to level out and increase airspeed.
Its not really about output, its about heat, and a combat climb is usually the most trying for radials because the output is high but the airspeed is low.

A climbing comparison might actually let the V engine climb longer at higher output but requiring a longer break to cool down, where the radial engine might not climb as long at higher outputs before it needs a short break to cool down some.
The rate of climb has more to do with the aircraft the engine goes on.

Aside from comparing horses, also compare propeller efficiency and design height.
Some planes just perform better at certain heights despite output.
It might fly faster at X,000 ft, but accelerates, zooms, and turns better at X,000 ft.
Consider drag, wing design, and acceleration and don't forget the octane rating.
Their ratings probably has more to do with octane and ram air efficiency something that was not well understood with either engine when they were first put into service.

If it says anything, the Hawk 75 or Mohawk /P-36 was said to climb with.. and had just a slightly wider turning radius than the Zero up to about 8000ft.
While the P-40 could not climb with the Zero or P-36 it out accelerated them (from 200IAS) in level flight up to 15,000ft.