Bearcat vs Corsair

[GregP]

We'll have to disagree on the acceleration, Tomo, and I believe it has been clearly established that the F8F was a great fighter up to about 20,000 feet, so any meaningful comparions would have to come where you would FIND an F8F flying about, and that is not much above 20,000 feet in any case.

It COULD have been made into a high altitude fighter with a 2-stage supercharger or a turbocharger, but that Navy didn't need that capability and never developed it. I see a lot of things attributed in here to the P-51H that, in my own experience, weren't necessarily that way. We have several pilots at the museum who flew P-51H models and they have never expressed any great preference for it over a D. I get the feeling that it COULD be faster and but they really didn't spend much time doing it. It would be nice to see a dedicated thread on the benefits of the H from people who FLEW them, not from paper specifications.

Of interest to me would be the real-world performance and the real-world reliability. It also might be of interest to know the earliest time at which the H COULD have been fielded had it been deemed very important to do so. We KNOW it got to the war late, but COULD it habe gotten there a lot sooner?

That's the part of what-ifs I don't like. Anything is possible to the person suggesting it, but if the premise were have been done in real life, what would have been affected that could produce a negative that would outweigh any potential positive gains?

 

[grampi]

We'll have to disagree on the acceleration, Tomo, and I believe it has been clearly established that the F8F was a great fighter up to about 20,000 feet, so any meaningful comparions would have to come where you would FIND an F8F flying about, and that is not much above 20,000 feet in any case.

It COULD have been made into a high altitude fighter with a 2-stage supercharger or a turbocharger, but that Navy didn't need that capability and never developed it. I see a lot of things attributed in here to the P-51H that, in my own experience, weren't necessarily that way. We have several pilots at the museum who flew P-51H models and they have never expressed any great preference for it over a D. I get the feeling that it COULD be faster and but they really didn't spend much time doing it. It would be nice to see a dedicated thread on the benefits of the H from people who FLEW them, not from paper specifications.

Of interest to me would be the real-world performance and the real-world reliability. It also might be of interest to know the earliest time at which the H COULD have been fielded had it been deemed very important to do so. We KNOW it got to the war late, but COULD it habe gotten there a lot sooner?

That's the part of what-ifs I don't like. Anything is possible to the person suggesting it, but if the premise were have been done in real life, what would have been affected that could produce a negative that would outweigh any potential positive gains?

Considering the "H" model had 600 more HP, and 600 pounds less weight than the "D" model, I don't see how it's performance wouldn't have been much better than that of the "D" model...

 

[GregP]

Let's put this P-51H myth to bed once and for all.

The V-1650-9 that powered the P-51H (and a few V-1650-11s, too) was rated at 1380 HP at full military power at sea level and about 1380 at 19500 feet while the P-51D's V-1650-7 was rated at 1490 HP at full military power at 19400 feet. Both of these ratings were at about 67 inches of Mercury or close to +16 psi boost. So the P-51H didn't make more HP more than the V-1650-7 engine up to full throttle at normal boost pressures at 19400 feet or so. The 2200 HP WEP that the V-1650-9 and -11s were capable of was at 81 inches of mercury or about +25 psi boost, WITH water-methanol ADI injection. The ADI usually lasted about 4.5 – 5.0 minutes and then the Merlin had to be throttled back to 67 inches of Mercury, where it basically equal to the -1, -3, and -7 engines of the D models. The WEP setting for the P-51D didn't use water-methanol injection and was available for 15 minutes or however long the pilot wanted to gamble his engine.

The P-51D was 7125 pounds empty and 10,100 pounds normal weight. The P-51H was 6585 empty and 9500 pounds normal weight. That means both are full internal fuel and armament, but clean. Let's say the weight for comparison purposes is the empty weight plus 65% of the difference between empty and normal weights to allow for takeoff, climb, and cruise to some arbitray point.

That puts the P-515D at 9059 pounds and the P-51H at 8480 pounds. At 19500 feet the P-51D had 1490 HP available and the P-51H had about 1350 HP available at that same height using normal manifold pressures. If the P-51H went to 81 inches, then he had the 2200 HP and was a VERY sprightly performer for about 4.5 – 5.0 minutes, after which he was back to normal manifold pressure and normal rates of climb.

For the record, USAAC Report #TSCEP5E-1898 lists the rate of climb for the P-51H at 3395 feet per minute at 67" of Mercury at low blower critical altitude and 2640 feet per minute at high blower critical altitude. In that particular test, the P-51H ran fine but would not go into WEP as the engine started running rough when they tried, so they used mil power where it ran just fine. I have seen at least two other reports saying the same thing, though obviously many P-51Hs were capable of WEP.

That means the P-51D had a weight to power ratio of 6.08 pounds per HP while the P-51H had a ratio of 6.14 pounds per HP at the same manifold pressure. Pretty damned equal if you ask me, and I know you didn't. The P-51D could get to 1700 HP WER without ADI and sustain that for three times or more longer than the finicky P-51H could.

At WEP the P-51D had a weight to power ratio of 5.33 pounds per HP while the P-51H could get as low as 3.85 pounds per HP for a very short time IF WEP was available and was then back to 6.14 pounds per HP and normal manifold pressures.

So, YES, the P-51H could get some sparkling numbers, but not for very long. When it was out of ADI the two planes were VERY equal with the P-51D still having a non-ADI WEP available.

Bottom line is YES, the P-51H could put up sparking numbers for a very short time. After that time it wasn't any better than the P-51D and the P-51D could still go to WEP and out-perform the P-51H once the P-51H's ADI was gone.

The Bearcat's empty weight (F8F-1) was 7070 pounds and 9600 loaded. If we use the same 65% of the difference, the test weight is 8714 pounds with 2300 HP on tap. The comparative weight to power ratio is 3.79 pounds per HP and the Bearcat is still climbing at 3060 feet per minute at 20000 feet even though it isn't a "high altitude" fighter.

You can favor the P-51H all day; I'll stick with the Bearcat, especially since it's great big HP advantage was NOT using ADI and was avilable as long as you had fuel. Admittedly, that wouldn't be for too long relative to the P-51H, but it also wasn't restricted to only a few minutes of high power.

Please don't take this wrong. I love the P-51, all models including the P-51H. But the P-51H wasn't the all-conquering hero that it is usually made out to be except for 4.5 - 5.0 minutes IF the ADI works, and then it is hell on wings for a short time after which it back to P-51D type numbers VERY rapidly.

 

[wuzak]

Given that the V-1650-9 was basically the same as the Merlin 130/131 in the Hornet, I can't see how your numbers add up.

The 130/131 was rated at >2000hp without ADI.

The RM.17SM was rated at 2,200hp @ 2,000ft MS gear and 2,100hp @15,000ft FS gear without ADI (pased type test but didn't go into production).

Wiki lists the Packard Merlin performances as:

• V-1650-1: 1,390 hp (1,040 kW); Based on Merlin 28, used in P-40 Kittyhawk and Curtiss XP-60 fighters
• V-1650-3: 1,280 hp (950 kW); Based on Merlin 63.
• V-1650-5: 1,400 hp (1,000 kW); Experimental.
• V-1650-7: 1,315 hp (981 kW); Similar to Merlin 66, primary powerplant of the P-51D Mustang.
• V-1650-9: 1,380 hp (1,030 kW); 2,218 hp WEP with Water methanol injection.
• V-1650-9A: 1,380 hp (1,030 kW);
• V-1650-11: 1,380 hp (1,030 kW); Modified fuel system.
• V-1650-21: 1,380 hp (1,030 kW); Opposite rotation for P-82 Twin Mustang

I wouldn't mind seeing a graph of power vs altitude for the F8F-1 and the P-51H. Both at WEP or normal power, so we can see what the power difference really is.

 

[GregP]

Hi Wuzak,

They don't have to add up. They are from "Allied Aircraft Piston Engines of WWII" by Graham White. I extracted the HP from two data points that were about the same height lower and higher than the V-1650-7 engine. It is very close and any difference would be small.

The -9 was 1380 HP at sea level, 1500 HP at 13750 feet and 1210 HP at 25800 feet. I extrapolated the HP at about 19400 feet so they would be at the same altitude. Both are at about 67 inches of MAP. The 2200 was at 81 inches with ADI and was not allowed to go to WEP without ADI or the engine would fail almost immediately. When they do that at Reno these days, they fail almost immediately, too. That is WITH hot rod parts, not stock Merlin rods that self destruct at just about 2400 - 2800 HP or so. That's why Voodoo and Strega are both running Allison G-series rods ... so they DON'T self destruct, even at 4000 HP.

The -7 was rated at 1700 HP WEP at 6400 feet and 1490 at 19400 feet without ADI.

Both from multiple sources.

I don't condsider Wiki a source. It may be something to quote as a start to a discussion, but I wouldn't trust Wiki for a recipe for a muffin. Graham White I trust one hell of a lot more ...

Of course, you are free to disagree as you have, but I'm not very far off the mark if at all. Too many people who flew them say the same thing. I REALLY trust the guys who flew them. They loved the 5 minutes of ADI and after thaht it was a stock P-51D or close to it with a bit more speed .... maybe 450 mph versus 435 - 437 at best P-51D altitude. That isn't enough extra for ME to build it at all, and certainly not enough to warrant a wartime production interruption.

As I've said on numerous occasions, top seeds are for test pilots. The only time service pilots see top speed is ina dive or in a deliberate training exercise to reach top speed. Other than that they rarely ever get above takeoff and climb power except in combat. If I was 500 miles from home over Berlin, I would NEVER use WEP. If I had to goose it a bit I would, but getting home would, for me, preclude long stints at WEP that ultimately destroys a Merlin. The only question is when.

They'll criuse and run at Mil power for a LONG time, but WEP is very hard on them.If you broke the throttle wire to go into WEP, it was a sign for your crew chief to change engines ... assuming he liked you.

You may well disagree and have wanted it in serial production at the earliest possible date. I'd understand while being a dissenter. For the 5 minutes of ADI, I might agree. After that, it was nothing but a production interruption that was not acceptable to the actual wartime people in charge until very late war ... or it would have entered service sooner.

It didn't.

ALL the Merlins that made 2000+ HP did so at elevated boost and sometimes elevated rpm. They'll tolerate the rpm and the boost to a point and then give up.

The engines in Streaga and Voodoo cannot go 8 laps (64 miles) at full race power. They CAN go 8 laps at reduced power, and have been optimized for that by very judicious use of stronger rods, custom parts, custom pistons, frequent main bearing replacement, and modern ignition and mixture control. You might recall that the world record 1930s Merlin predecessor engines from Rolls Royce were expected to run at full power for all of 15 minutes, after which all bets were off.

Wartime Merlins used essentially the same parts and weren't far from the Buzzard and R internally. Better, yes, incrementally. Wildly different? No.

 

[cimmex]

Thank you Greg for this informative post 63. Very credible!

 

[GregP]

Hi Cimmex,

Thanks!

The P-51H is held up as a high standard and it COULD do very well if the ADI was still there and working. After that is was a bit better than the P-51D, but not a lot. To be so it needed the extra power that ADI and the boost increment afforded.

The Ta 152 could ALSO do VERY well if everything was perfect. I have a hard time believing that it was perfect most of the time as very few ever flew in combat and it USUALLY takes some time to work out the kinks in a new plane whether it is British, U.S., Japanese, or German ... or anyone else's for that matter. Maybe the Ta 152 was the exception and everything was perfect right off the drawing board, I can't say. But after the ADI ran out, the Ta 152 was back to P-51D type speeds and climb rates (426 - 435 mph or so and 3200 - 3400 feet per minute climb rates or so). So it was NOT a bad plane by any stretch of the imagination.

The Fw 190D / Ta 152 series and the late war P-51s were quite equal after the nitrous and water methanol ran out. The thing working against the D models was sheer volume of Allied fighters in the air compared with the number of Fw 190Ds in the same airspace. While the boost was there, either the P-51H or the Ta 152 was necessarily slightly better depending on altitude and starting position, but the two never fought so we can't say which was superior under full boost ... it is a true "what if." The Fw 190 and Ta 152C were better at rolling than ANY Allied planes, but that is not decisive in itself since they also had a vicious stall and could not turn with some Allied fighters near the stall/cornering limit, especially at low altitude since if it DOES stall, it would usually invert and spin into the ground ... not a good outcome for the Focke Wulf driver. The P-51D did that, too, but gave the pilot a very good stall buffet warning before it happened. I've ridden in a P-51D when the owner was practicing for a flight review. He didn't stall it but DID fly stall approaches, and it does shake enough to warn you unless you are on drugs or are just not paying attention.

Not too sure about the LONG wing Ta 152H's roll rate, but it HAD to slow down from the dazzling radial Fw 190 and Ta 152C roll rates due to span if nothing else. I belive the Ta 152 had more engine boost time than the P-51H did ... about 15 minutes as I recall, maybe incorrectly.

My biggest "observation" about the Ta 152 C or H is the low number fielded, which made them ineffective against 1000+ plane bomber and fighter streams. They would run out of ammunition after several attacks if nothing else, but they WOULD have attracted a lot of Allied attention after a firing pass and there were a LOT of P-51s around to answer the challenge.

One on one they are as good as the best we had, maybe slightly better (assuming equal pilots), especially in armament and when the boost is available. Not all the Germans were Erich Hartmann and not all the U.S. pilots were Richard Bong, either.

Wish we had a real Ta 152 / Fw 190D to fly at our museum! That would be marvelous! We HAVE a replica Fw 190F and it is very cool to see it fly! (flies behind a Pratt Whitney R-2800)

Would be better if we could install a real BMW 801 radial ... WITH the automatic mixture and rpm controls, that is.

You don't happen to HAVE one, do you?

 

[cimmex]

it was not my intention to start a Ta152/ P-51H contest but BTW have you heard about that: "mail from Tehachapi - Mike Nixon / Vintage V12´s is restoring one of the rarest german engines, the powerful Jumo 213 - again Mike is doing a fantastic job ! Thanks to Mike Nixon for sharing this restoration with us".
https://www.facebook.com/pages/MeierMotors-GmbH/196699400376090

 

[tomo pauk]

As Shortround6 says - dont know where to start from

Let's put this P-51H myth to bed once and for all.

The V-1650-9 that powered the P-51H (and a few V-1650-11s, too) was rated at 1380 HP at full military power at sea level and about 1380 at 19500 feet while the P-51D's V-1650-7 was rated at 1490 HP at full military power at 19400 feet. Both of these ratings were at about 67 inches of Mercury or close to +16 psi boost. So the P-51H didn't make more HP more than the V-1650-7 engine up to full throttle at normal boost pressures at 19400 feet or so. The 2200 HP WEP that the V-1650-9 and -11s were capable of was at 81 inches of mercury or about +25 psi boost, WITH water-methanol ADI injection. The ADI usually lasted about 4.5 – 5.0 minutes and then the Merlin had to be throttled back to 67 inches of Mercury, where it basically equal to the -1, -3, and -7 engines of the D models. The WEP setting for the P-51D didn't use water-methanol injection and was available for 15 minutes or however long the pilot wanted to gamble his engine.

Either it is not a myth, or it refuses to go to the bed (just like my older daughter).
When V-1650-9 was using WI, almost 2300 HP was available on 90 in Hg, and ~2150 on 80 in Hg, that is for 1st gear (under 10000 ft). In 2nd gear, it was 1750-1800 HP, depending whether 80 or 90 in Hg was used. Altitude about 20000 ft; the P-51D on 67 in has some 1500 HP at that altitude.
WEP setting (67 in Hg on 130 grade fuel) for the P-51D was available for 5 minutes, not 15 minutes. Military power was using 61 in Hg.
Once the water is gone, the V-1650-9 still has an option to use the 'dry WER' rating, 3000 rpm and 70 in Hg.

The P-51D was 7125 pounds empty and 10,100 pounds normal weight. The P-51H was 6585 empty and 9500 pounds normal weight. That means both are full internal fuel and armament, but clean. Let's say the weight for comparison purposes is the empty weight plus 65% of the difference between empty and normal weights to allow for takeoff, climb, and cruise to some arbitray point.

If I may suggest:
Let's not fill fuselage tank, that would shave 300 lbs from the P-51H, ie. take off weight of is now 9300 lbs, with 210 gals and full ammo load. For the P-51D, it is 85 gals = 510 lbs, for take off weight of 9600 lbs (184 US gals aboard; full ammo)

That puts the P-515D at 9059 pounds and the P-51H at 8480 pounds. At 19500 feet the P-51D had 1490 HP available and the P-51H had about 1350 HP available at that same height using normal manifold pressures. If the P-51H went to 81 inches, then he had the 2200 HP and was a VERY sprightly performer for about 4.5 – 5.0 minutes, after which he was back to normal manifold pressure and normal rates of climb.

Covered above - once the water is out, there is still 'dry WER' available, along with military power for the P-51H.

That means the P-51D had a weight to power ratio of 6.08 pounds per HP while the P-51H had a ratio of 6.14 pounds per HP at the same manifold pressure. Pretty damned equal if you ask me, and I know you didn't. The P-51D could get to 1700 HP WER without ADI and sustain that for three times or more longer than the finicky P-51H could.

Quirk is that P-51H does not need to be run on same manifold pressure as the P-51D. Only 5 min for the WER of the P-51D.

So, YES, the P-51H could get some sparkling numbers, but not for very long. When it was out of ADI the two planes were VERY equal with the P-51D still having a non-ADI WEP available.

Other people, that really flew fighter aircraft, might confirm that 5 minutes is like ages once in air combat? Most engines of the ww2 have had the 'emergency rating' that spanned between 3-5 minutes, nobody complained.

The Bearcat's empty weight (F8F-1) was 7070 pounds and 9600 loaded. If we use the same 65% of the difference, the test weight is 8714 pounds with 2300 HP on tap. The comparative weight to power ratio is 3.79 pounds per HP and the Bearcat is still climbing at 3060 feet per minute at 20000 feet even though it isn't a "high altitude" fighter.

Let's not use the 65% rule of the thumb. The Bearcat already has only 185 US gals aboard, ie. less than P-51H with only wing tanks full. Meaning the take off weight of 9670 lbs, per SAC table. 370 lbs greater than the P-51H, or thereabout with P-51D. At 20000 ft, the P-51H climbs at 3600+ fpm, or more than 20% better than the F8F-1.
At 30000 ft, it is ~1250 fpm (F8F-1) vs. 1900 fpm (P-51H). At 10000 ft, it is 4200 vs. 4250 fpm, minimal advantage for the P-51H. All values for the P-51H are with fuselage tank empty (ie. for total of 210 gals).

You can favor the P-51H all day; I'll stick with the Bearcat, especially since it's great big HP advantage was NOT using ADI and was avilable as long as you had fuel. Admittedly, that wouldn't be for too long relative to the P-51H, but it also wasn't restricted to only a few minutes of high power.

2300 HP was used for take off. Without ADI, F8F-1 drivers have 2100 HP on disposal at 3000 ft, and 1700 HP at 16000 ft. Surely beating the V-1650-9 wihout ADI. However, at 20000 ft, there is only 1500 HP available, vs. 1400 for the -9; not enough to overcome the disadvantage in weight and drag vs. the P-51H.
At 30000 ft, it is 1000 HP vs. 1200 for the V-1650-9. In case both F8F-1 and the P-51H are using ADI, the P-51H has more power in 10-20 kft belt.
The F8F-1 could not use max power ratings for 'as long as you have the fuel' neither. Max continuous is not equal to military power.

Quite a bit of data about the F8F-1 and P-51H are available on the Williams' site and here (F-51H, per post-was nomenclature)

edit: the RoC figures I've posted are from SAC sheets, and actually are for 260 gal fuel (ie. all 3 internal tanks full), not just for 210 gals as stated above

 

[Bad-Karma]

Seems to me its a classic example of Interceptor vs Escort. F8f dominating down low with the P51H being dominant up high.

 

[GregP]

Hi Cimmex!

Do you happen to know what the Jumo 213 is going into? Maybe a Focke-Wulf? I'd really lover to hear it run. Always liked the numbers for the Jumo 213. I'll bet Steve Hinton knows. If I manage to find out, I'll post it. Mike is also overhauling a DB 601 that came out of a Bf 109E that was found at the bottom of a Russian lake. We have the airframe at the musuem and it belongs to a private party. The engine was in good shape except for the nosecase which, being Magnesium, was gone. The owner had a new one made from Aluminum. The owner is unsure whether to restore this one or to use it as a template to build another one from scratch.


Hi Tomo,

we'll have to disagree, but that's OK. I got my weight numbers from multiple sources, including Boeing (who bought and owns what used to be North American Aviation some time back).

Tell you what, do a comparion atfer the P-51D and P-51H have both been airborne and in cruise for 3 - 4 hours or so and see what you come up with. The HP numbers for the V-1650-9 come from Graham WHite's excellent book. The source you use won't matter, it'll be close even if slightly different. The -7 and -11 were not cleared for elevated WEP MAP without ADI. Without the ADI they were to be run at 65 - 67 inches of MAP ... close to +16 psi of boost. At that level of boost they were VERY equal to the V-1650-1, 3, 7 engines.

Whether or not the R-2800 required ADI was largely dependent on the myriad dash number. I have the R-2800 book and will gladly look up the HP for any dash number if anyone is interested. Some WEP powers were wet (ADI) and and some were dry (no ADI). Several had two WEP number for both wet and dry.

The 3000 feet per minute climb at 20000 feet for the F8F-1 came from a flight report and I doubt if very many Bearcats ever got that high except as an exercise. The flight report was for a clean airplane with pilot, fuel, and ammunition and no drop tanks or external ordnance. The Bearcat could get that way by taking off with drop tanks, using them and dropping them. I was trying to do some figuring under similar conditions ... full internal load, clean airplane, and fuel about 1/2 to 3/4 full at some point in the flight. What I didn't do was to figure it by fuel flow. Instead I chose to take empty weight and use 65% of the normal loaded weight number. The F8F didn't get into combat for the U.S.A. in the WWII era and several years afterwards, but did for the French in Indochina. When the French fought with them, they were always down low, even performing ground attack. Had they been using P-51Hs, the same would have been true so any comparisons would have been at low altitude anyway.

 

[cimmex]

hi Greg
Well, I found this in a German aviation forum. Most members speculate that the engine is for a Flugwerk D-9 replica. AFAIK two of them are around and at least one is owned by Jerry Yagen

 

[cimmex]

double post

 

[GregP]

Hi Cimmex,

That makes perfect sense, and is about what I figured. There is almost no point in overhauling a Jumo 213 unless you intend to actually run it. After an overhaul, if an aviation engine of large displacement sits around for as litle as 5 years, it needs another overhaul before you try to run it. That being said, overhauling a Jumo 213 almost has to mean it is going into an aircraft.

I heard the Fw 190D-13 that Doug Champlin run once. They didn't have the high-speed unit for throttle control, so it only ran at idle power, but it DID run and sounds different from the usual Allison and Merlin V-12s we hear most of the time. That aircaft is now in Paul Allen's collection in Seattle, Washington.

We DO get to hear the Argus inverted V-12 that is in our Pilatus P-2 every once in awhile and it has a unique sound to it, too. If anyone is interested, I can get pics tomorrow as Saturday is my volunteer day at the museum. In fact, if you like I can get pics of ALL the German items there and post tomorrow or Sunday.

The Pilatus has a couple of interesting features. It is Swiss, of course, and they are frugal if nothing else. They had a group of Bf 109s due to retire when they decided to make a trainer, and they took the landing gear and instrument panels from the Bf 109s and used them directly on the P-2s. The left main gear is the Bf 109s right main ghear and vice versa, and it folds inward! Pics on the way ...

 

[tomo pauk]

Hi Tomo,
we'll have to disagree, but that's OK. I got my weight numbers from multiple sources, including Boeing (who bought and owns what used to be North American Aviation some time back).

I have no problems with your weight numbers for the weights, they are as good as it gets.

Tell you what, do a comparion atfer the P-51D and P-51H have both been airborne and in cruise for 3 - 4 hours or so and see what you come up with. The HP numbers for the V-1650-9 come from Graham WHite's excellent book. The source you use won't matter, it'll be close even if slightly different. The -7 and -11 were not cleared for elevated WEP MAP without ADI. Without the ADI they were to be run at 65 - 67 inches of MAP ... close to +16 psi of boost. At that level of boost they were VERY equal to the V-1650-1, 3, 7 engines.

On 130 grade fuel, the max manifold pressure, without ADI, was 67 in Hg for the V-1650-9.
70 in Hg should be on 145 to 150 grade fuel, at least that is my understanding. Same for the 90 in Hg - uses ADI and 145 to 150 grade fuel. A chart with different engine power settings resulting powers: pic. On 67 in Hg, the power was about the same as what V-1650-3 offered - no wonder, since the supercharger size and gearing were pretty much the same, and the engine RPM was same.

Whether or not the R-2800 required ADI was largely dependent on the myriad dash number. I have the R-2800 book and will gladly look up the HP for any dash number if anyone is interested. Some WEP powers were wet (ADI) and and some were dry (no ADI). Several had two WEP number for both wet and dry.

About the R-2800-34W: it did have ADI, useful up to about 15000 ft. No ADI - no WER here. Was also true for the other R-2800s, at least war-time examples, I'll bow to superior data, however.
The ADI for the V-1650-9 was useful up to ~25000 ft, so was for the R-2800-18W (late war version, 2-stage S/C, used on the F4U-4).

The 3000 feet per minute climb at 20000 feet for the F8F-1 came from a flight report and I doubt if very many Bearcats ever got that high except as an exercise. The flight report was for a clean airplane with pilot, fuel, and ammunition and no drop tanks or external ordnance.

The SAC (link) for the F8F-1 also shows 3000 fpm at 20000 ft. Achieved with fully combat-capable aircraft, so full ammo internal fuel.

The Bearcat could get that way by taking off with drop tanks, using them and dropping them. I was trying to do some figuring under similar conditions ... full internal load, clean airplane, and fuel about 1/2 to 3/4 full at some point in the flight. What I didn't do was to figure it by fuel flow. Instead I chose to take empty weight and use 65% of the normal loaded weight number.

This is why I didn't followed you on the 65% thumb rule - I've simply listed the related performance figures for it, for the 'combat weight'. They are very good, and will put any Merlinized P-51 in troubles under 10000 ft, but not above 15-20 kft.

 

[wuzak]

Lumsden Data on V-1650-7 and V-1650-9 on 100/130 grade fuel:

V-1650-7
Takeoff: 1,315hp, 3,000rpm, +12psi
WEP MS: 1,705hp, 3,000rpm, +18psi, 5,750ft
WEP FS: 1,580hp, 3,000rpm, +18psi, 13,500ft

V-1650-9
Takeoff: 1,380hp, 3,000rpm, +14psi
WEP MS: 1,920hp, 3,000rpm, +20psi, 9,500ft
WEP FS: 1,620hp, 3,000rpm, +20psi, 21,750ft

Lumsden doesn't have Normal power for the Packard Merlins, but we can use values for the similar Rolls Royce models:

Merlin 66 (V-1650-7)
Normal MS: 1,415hp, 2,850rpm, +12psi, 8,500ft
Normal FS: 1,310hp, 2,850rpm, +12psi, 18,000ft

Merlin 110-114 (~V-1650-9)
Normal MS: 1,380hp, 2,850rpm, +12psi, 15,500ft
Normal FS: 1,200hp, 2,850rpm, +12psi, 30,000ft

The Merlin 130/131
Normal MS: 1,430hp, 2,850rpm, +12psi, 11,000ft
Normal FS: 1,280hp, 2,850rpm, +12psi, 14,000ft

The V-1650-7 is listed as weighing 1,645lb (746kg) and the V-1650-9 1,690lb (767kg).

The V-1650-7 was a 60-series Merlin, basically similar to the Merlin 66.

The V-1650-9 was a 100 series Merlin with end to end lubrication, overhung first stage supercharger impeller and single point fuel injection (into eye of supercharger impeller). I assume the overhung first impeller reduced losses due to the intake (big improvements in performance were found when the intale to the supercharger was improved by Hooker).

The supercharger impellers were 12.0"first stage and 10.1"second stage for both -7 and -9. The supercharger gear ratios were MS 5.8:1 and FS 7.34:1 for the -7, MS 6.39:1 and FS 8.095:1 for the -9.

So the -9 was a higher altitude rated engine.

Greg mentions the V-1650-1, -3, -7 and -9. The -1 was a 20-series Merlin with single stage two speed supercharger. The -3 was an early 60-series engine, equivalent to the Merlin 63. It lacked the strengthening that the later engines received, and so did not have the capability of higher pressures.

A note about ADI and Merlins: None of the Rolls-Royce Merlins used ADI during the war. The stronger engines (eg Merlin 66) were good for +25psi boost on 100/150 grade fuel without ADI.

According to White, R-2800 Pratt Whitney's Dependable Masterpiece the R-2800-34 had the following performance with 100/130 grade fuel:

Takeoff: 2,100hp @ 2,800rpm
Military LO: 2,100hp @ 2,800rpm, 3,000ft
Military HI: 1,700hp @ 2,800rpm, 16,000ft
Normal LO: 1,700hp @ 2,600rpm, Sea Level
Normal LO: 1,700hp @ 2,600rpm, 8,500ft
Normal HI: 1,500hp @ 2,600rpm, 18,500ft

Unfortunately boost/MAP is not shown.

Boost Pressure/MAP Equivalents:
+12psi = 54.4inHg MAP
+14psi = 58.4inHg MAP
+16psi = 62.5inHg MAP
+18psi = 66.6inHG MAP
+20psi = 70.6inHG MAP
+25psi = 80.8inHg MAP
+30psi = 91.0inHg MAP

 

[GregP]

The Bearcat mostly used the -22W and -34W, not the -34. The F8F-2 used the straight -30.

The -22W and -34W used water injection, not water-methanol, and the -30 made 2250 HP without water.

I wouldn't think you'd want to spend non-combat time climbing at WEP or you won't have any ADI left for combat. That being said, the P-51H climbed almoist exactly like a P-51D unless it was at WEP, which was my point to start with. If you are betting your life on WEP, you'd best be really careful about under what circumstances you use it. So there would be virtually ZERO non-combat use of WEP requiring ADI ... unless it was a peacetime joyride.

Now we all know that these engines (both Allied and Axis) could be run at slightly higher rpm and MAP than the manufacturers recommended as maximum, but these numbers are not published ANYWHERE. They are in the minds of the former crew chiefs and pilots. As it happens I know some of the settings they used for the -7 and -9 Merlins, and they were VERY comparable until the ADI went in and the manifoild pressure went up to 81 inches or so. That's when the -9 and -11 could really shine, but you better be careful how long you make use of it or the crew chief will be changing it before the next flight.

I've heard it said that the -7 could ALSO be flogged at 81 inches and make very comparable power, but it was HIGHL:Y frowned upon by the crew chiefs and squadron commanders because of the engine wear ... and they could tell by looking at the color of the spark plus and exhaust manifolds near the cylinder ports, sort of like on a Harley Davidson motorcycle today. A lean run is VERY apparent on the pipes, and even auto-rich wasn't rich enough for 81" unless the engine was a -9 or -11.

As for the radials, the 2100 HP was max at 2800 - 2850 rpm with water. Later R-2800s that went into the Bearecat could make a few hundred more. The -30 could make 2250 HP dry. They even made one fan-cooled R-2800 that could produce 2800 HP and another variant that made 3400 HP, but they ran on a test stands (dynamometers) and never flew. Most Bearcats were 2100 or 2250 HP untis, some of the late ones were 2400 HP. I've seen at least three Bearcats personally that the owners said had the 2400 HP unit in them. That was the power level late in the war, and many survivors have been fitted with them. I suppose it you are building one today from parts, you might as well get the best engine.

That doesn't change the fact that I read a flight test report that said a clean Bearcat could still climb at 3000 feet per minute at 20000 feet. Hardly any real Bearcats DID since they would mostly be climbing at reduced cruise-climb power unless they were in combat where all the stops are pulled. The same can be said for ALL the piston fighters.

The numbers we throw around in here are possible but not very likely ..., unless in combat.

 

[pbehn]

Can you compare a merlin in line water cooled v engine with a P&W air cooled engine? The Merlin with a meredith effect radiator had a small frontal area and little cooling drag. The P&W 2800 had massive max horsepower and torque but the frontal area eats horsepower. Horses for courses.

 

[tomo pauk]

The -22W was used only in prototype (maybe). Think we can forgive Wuzak for not typing the 'W' behind '34'

The F8F-2 used the straight -30.

Actually, it was -30W; SAC.

Re. a fan cooled R-2800: it flew, propelling the XP-47J to around 500 mph. Granted, turbo helped to get to that speed. 2800 HP was available (without fan here) for bread'n'butter P-47Ds, with ADI and on 150 grade in the same time. Plus for the P-47M and -N.
Unfortunately, fan cooled R-2800s were not used on the Beacrcat.

The -22W and -34W used water injection, not water-methanol, and the -30 made 2250 HP without water.

Care to back up that it was only water, not water-methanol? What was used as anti-freeze, with alcohol absent?

That doesn't change the fact that I read a flight test report that said a clean Bearcat could still climb at 3000 feet per minute at 20000 feet.

That values is stated in the SAC, no worries.

 

[GregP]

Yah, I can forgive Wuzak for almost anything.

About backing up thw water only, that's what I heard from an old crew chief, and he said they weren't worried about freezing until they had to. That was in the Pacific at 15,000 feet and under while flying around carrier task groups. I suppose you WOULD have to add some antifreeze in the ETO since there IS a winter there as opposed to the South Pacific winter.

We could comare the radial against the liquid-cooled engines, but you'd have to have the drag numbers to do much with it. I believe Drgondog has done some of these comparisons in here in the past, but I can't recall the post title. You can do a seach for it. The words will include cd0 or CDO or zero lift drag coefficient.

I don't want to do it for a general answer because then someone asks somethign specific and you have to ignore it or do it all over again. However, the puiblished top speeds for the fighters, and remember these are at best altitude only, can give you a good feel for the differences. Most radial planes were a bit bigger than most inline planes, with the Bearcat as a notable exception.

The Bf 109 was the classic smallest airframe which could be wrapped around a big engine.

The P-47 was the other end of the spectrum, with the Brits joking that they could take evasive action by jumping around inside the fuselage if attacked. But it was the best or one of the front-running top high altitude fighters of the war. Being big and heavy, it was no slouch at diving away or diving toward anything. The trick was to stay in the middle of the air and avoid the ground.

The fastest aircraft of WWII included the Dornier Do 335 Pfiel, the P-51H at WEP, the Ta 152H at WEP, the Republic XP-72 (a prototype) and the XP-47J. After the war the Commonwealth CAC-15 was also right there at just over 500 mph.

Then we fixated on jets and abandoned big piston engine development work about 1946 or so. The big pistons were hard to work on, expensive to maintain, and ate fuel like crazy, and the civilian market potential was limited at best. So it all made sense economically anyway. I believe the last big piston fighters made included the Douglas Skyraider, Sea Fury, the Hispano Ha.1109, 1110, and 1112 and a few prototypes, of which my personal favorite is the FMA I.Ae.30 Namcu of 1950.

It looks like nothing so much as an all-metal Mosquito / Hornet combination. It was fast at 460 mph and had SIX 20mm cannons! Unfortunately the total population is one prototype. Bet that puppy could lay down some supressing fire!