Bearcat vs Corsair

[wuzak]

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

Greg, the -34 was the same as the -34W, only without ADI. The figures White has for the -34/-34W are without ADI and are the same for both versions.

The F8F-2 was a couple of years later (1947) and not really contemporary with the P-51H.

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

Autorised ADi mixtures for the R-2800 (from White):

• Methyl Alcohol 50%/Water 50%
• Methyl Alcohol 60%/Water 40%
• Methyl Alcohol 25%/Ethyl Alcohol 25%/Water 40%
• Methyl Alcohol 60 parts/Water 40 parts/Anti-Corrosion Oil 1 part

So straight water was not authorised for the R-2800.

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.

The V-1650-9 had 215hp more at WEP in MS gear to an altitude 3,750ft higher. And 40hp more at WEP in FS gear at an altitude 8,250ft higher. Basically it had more power more of the time.

The 66 (~V-1650-7) seems to have more power for normal climb than the Merlin 110-114 (~V-1650-9). It is 35hp in MS gear, but 7,000ft lower. The advantage in hp is greater in FS gear at 110hp, but so is the altitude difference at 11,000ft. The two engines are rated for different heights, but I suspect that the -7 has the advantage in normal power mainly in MS gear - in FS gear its peak is only a few thousand feet above the -9s MS peak, so possibly the two would be about equal at that point. Basically the -9 has the advantage for most of the altitude range.

Add that to the weight advantage and it isn't hard to see that the H woudl climb better than the D.

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 have shown that the -9 has a significantly higher FTH in both MS and FS gears. There were a number of mechanical improvements in the -9 over the -7 which helped increase the FTH, increase the hp and allow for more boost.

The -9 should handle 81inHg (+25psi) without ADI (since Rolls-Royce Merlins could) - 100/150 fuel required, of course. ADI allowed the -9 to use 91inHg
(+30psi) for even more power.

It is my understanding that WEP was limited to 5 minutes mainly because of oil and coolant temperatures, the cooling circuits not designed for such high powers (if they were they would be very large and draggy).

The pilot could use WEP multiple times - but would have to let the system cool before using it again.

As for the radials, the 2100 HP was max at 2800 - 2850 rpm with water. With ADI that went up, and later R-2800s that went into the Bearecat could make a few hundred more.

Well since there weren't later military Merlins, particularly not the Packards, later R-2800s are irrelevent to the discussion.

The -30 could make 2250 HP dry.

In 1947. White gives the maximum power as 2,300hp @ 2,800rpm for the -30W, but doesn't say at which height. It is shown as 1,600hp @ 22,000ft, or very similar to the V-1650-9 dry (1,620hp @ 21,750ft).

The RM.17SM could make 2,200hp @ 2,000ft and 2,100hp @ 15,000ft dry (type tested rated power) - in 1944/45.

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.

The R-2800 with 2,800hp flew with the P-47M and N.

As for test bench engines, what of it? The RM17SM ran 2620hp on the test bench (3,150rpm, +36psi/103inHg, ADI).

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.

Late in the war with ADI.

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.

And the P-51H can climb at nearly 4,000fpm at that altitude.

http://www.wwiiaircraftperformance.org/mustang/p-51h-booklet-pg15.jpg

Left hand chart is for 81inHg (+25psi) boost and should be without ADI.

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.

It depends in what situation.

As the Bearcat was designed as an interceptor its primary goal was to get to altitude quickly. You won't be languishing around using the lower 30 minute climb rating when you have but a few minutes to get to the required altitude.

If, on the other hand, you were setting off for a long escort mission there is no need to flog the engine during the climb. There isn't quite the urgency.

 

[wuzak]

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.

The CA-15 recorded 500mph after a shallow dive. The top level speed was 460mph. About the same as a Spitfire 24, Martin-Baker MB5 and Hawker Sea Fury.

 

[GregP]

Is there a good book on the CAC-15?

I have only seen what I have seen on it, and it isn't really very much.

As for that giant reply above, I'll have to read it later. Have some things to do just now.

 

[GregP]

Hi Wuzak,

The P-51 was introduced to active service in 1942 and was retired from active service by 1951, with some air National Guard units retaining them later than that. P-51H: The first USAAF flights were from 4-14 Apr 1945 and 222 had been delivered by 30 Jul 1945. The last P-51H rolled out of the plant in Nov 1945.

The F8F Bearcat was introduced to active service in 1945 and was retired in 1961 from the VNAF. The first operational squadron was active on 21 May 1945 and it was out of active US Navy service by early 1950. The F8F-2 had the R-2800-30W that could make 2250 HP. F8F-2 Bearcat: Active service in 1948 and retired from active service by the end of 1950.

Neither was combat during the war and both were out of active service within about a year of one another. With no war going on the pace of development was glacial and they were contemporary to all purposes. In fact, ALL of the post-WWII big piston fighters were very firmly rooted in WWII development ... there being almost no development at all after WWII. The F8F-2 was a "fixed" F8F-1, nothing more. They added the -30W engine because it was available ... it was not developed for the Bearcat, it was near the end of the line in fact.

 

[GregP]

About the big reply, we have to disagree. No surprise there, is there?

I can't find any F8F delivered with a -30 or -34 engine, all were of the W variety. Don't really care what was authorized, such as water methanol, they probably used whatever they wanted. Liquid was needed and methanol was antifreeze. If you needed it, then the methanol was vital. If it worked OK without it, you can bet it happened.

Later R-2800's are not irrelevant to the discussion unless you don't want to talk. After the war, the useful life of big pistons was about 5 - 8 years before being sold for scrap, all of it until the Korean war was non-combat. Anything out there during the time they operated is relevant, especially since neither one patipated in WWII combat. Our ONLY comparion is post-war and I choose to make a comparion.


Wayne, I don't care at all what the full throttle height is. The HP ratings at altitude are known and recorded. I have them as well as you do. If you are NOT at those reported altitudes, you interpolate. You can bet none of the "best" ratings are left out of the specs, but if a plane makes 1500 HP at 15000 feet and 1200 HP at 28000 feet, we can all get pretty close at 19000 feet without having a test report in front of us. I can and I know you can. I bet a;most all the frequent responders in here can, too.

The -9 was not allowed to run at 81 inches without ADI. Whatever it should do had nothign whatsoever to do with Rolls Ropyce or the RAF. It was in US service, not British service. I was not talking about RM.17M engines, I was talking about the P-51H. It ran a V-1650-9 and -11 only. No other engines were delivered with the planes or flown in active service.

What do you mean' what of the test engines?" Go read what I wrote. I said the test engines never flew and that's as far as it went. I made no other claims. But I can extrapolate. AN engine taht can make 3400 HP in later lodels can usually make more than rated power and more rpm if called upon in an emergency. That is, all of them probably can except for the Briston Centaurus. It can make more power, but cannot tolerate more rpm without failure. Exceed max rpm by as little as 75 and it will grenade. I know too many people who have done just that! And in privcate hands, too. All of them still flying the Centarurs do NOT exceed rpm limits ... EVER. The Queen's Battle oif Britian Memorial Flight doesn't, either ... EVER. Joe did the cylinders for them recently and spoke with the operations office.

The P-51H cannot climb at 4000 feet per minute at 2000 feet, even at 90 inches. At 67 inches it went from 3370 feet per minute at 13400 feet down to 2400 feet per minute at 23100 feet. At 80 inches it went from 4590 feet per minute at 8300 feet down to 2150 feet per minute at 21500 feet. It could get close to 4000 at 90 inches (but not there) but after initial tests, it was not allowed 90 inches in servcice to the best of my knowledge. The max allowable was 81 inches ... with ADI. All the above numbers were at critical altitude from actual flight test reports. It got worse everyhere else, but that doesn't make for good reading in a sales pitch, does it?

Your chart is a sales pitch for the P-51H and is obviously of modern origin. No original USAAF or USAF chart looks like that. Modern charts created for the internet are not exactly the most reliable charts for historic data.

And the 471 mph was at 90 inches which, again, was cut to 81 inches in service, where the max speed was less.

As for the last paragraph, what are you thinking? In peactime climbing at reduced rates is normal and is done all the time. If you need to push the climb rate, it is for an operational reason related to unknown incoming traffic, and that is no longer peacetime, it is intercept time to address a potential threat to the Naval task force or to the base in question. All bets are off until peaceful intent is established. Otherwise, conserve the equipment and the expendable fuel, and woe be unto you if you drop a drop tank in peacetime without a declared emergency, much less blown an engine and lose the aircraft you signed for due to stupidity.

 

[wuzak]

The F8F-1 was contemporary with ethe P-51H. Having similar devlopment periods and introduction to service.

The Merlin devlopment in the US was pretty much stopped at the end of WW2. In the UK military developments were stopped too - the RM.17SM didn't go into production, even though it was type tested.

Development continued for the R-2800 post war, however, for both civilian and military purposes. The -30W was a result of that continuing development.

Regarding teh P-51D vs P-51H, the latter was ~1,000lbs lighter empty than the former. Given the same fuel and ammo, the P-51H will still be 1,000lbs lighter. At AUW the difference is around 10% - that's a big chunk of weight.

I have shown that power is better in the -9 for WEP (dry) than the -7, and that climb power is better over most altitudes.

So with less weight, more power and some improvement to aerodynamic details the H must climb and accelerate better than the D.

 

[GregP]

Hi Wuzak,

The P-51 was introduced to active service in 1942 and was retired from active service by 1951, with some air National Guard units retaining them later than that. P-51H: The first USAAF flights were from 4-14 Apr 1945 and 222 had been delivered by 30 Jul 1945. The last P-51H rolled out of the plant in Nov 1945.

The F8F Bearcat was introduced to active service in 1945 and was retired in 1961 from the VNAF. The first operational squadron was active on 21 May 1945 and it was out of active US Navy service by early 1950. The F8F-2 had the R-2800-30W that could make 2250 HP. F8F-2 Bearcat: Active service in 1948 and retired from active service by the end of 1950.

Neither was combat during the war and both were out of active service within about a year of one another. With no war going on the pace of development was glacial and they were contemporary to all purposes. In fact, ALL of the post-WWII big piston fighters were very firmly rooted in WWII development ... there being almost no development at all after WWII. The F8F-2 was a "fixed" F8F-1, nothing more. They added the -30W engine because it was available ... it was not developed for the Bearcat, it was near the end of the line in fact.

 

[wuzak]

I can't find any F8F delivered with a -30 or -34 nengine, all were of the W variety.

The -30W is a -30 engine, just with ADi added.
The -34W is a -34 engine, just with ADI added.

The ratings for the -30W and -30 are identical when ADI is not in use.
The ratings for the -34W and -30 are identical when ADI is not is use.

The ratings I posted earlier are for the -34 and -34W, and are not with ADI.

Don't really care what was authorized, such as water methanol, they probably used whatever they wanted. Liquid was needed and methanol was antifreeze. If you needed it, then the methanol was vital. If it worked OK without it, you can bet it happened.

So they used whatever the hell they liked? So much for testing and tuning at the factory.

Later R-2800's are not irrelevant to the discussion unless you don't want to talk. After the war, the useful life of big psitons was about 5 - 8 years before being sold for scrap, all of it until the Korean war was non-combat.

Of course later R-2800s are irrelevent. It's like comparing a Spitfire Mk IX with a later version of the Merlin with the Spitfire Mk II and Bf 109E.

Things are improved and tweaked over time. 2 years extra development would have been handy for the V-1650 in the P-51H.

Wayne, I donlt care at all what the full throttle height is. The HP ratings at altitude are known. If you are NOT at those altitudes, you interpolate. You can bet none of the "best" ratings are left out of the specs, but if a plane makes 1500 HP at 15000 feet and 1200 HP at 28000 feet, we can all get pretty close at 19000 feet without having a test run in front of us. I can and I know you can. Don't go there.

You can interpolate between two points in the same supercharger gear. You cannot interpolate between the power in MS gear and the power in FS gear. There is a drop off in power after FTH (point of max power in that gear) until a gear change, where the power rises again until the next FTH is reached.

You also cannot interpolate power from a point below FTH to a point above FTH.

The -*9 was not allowed to run at 81 inches without ADI. Whatever it should do had nothign whatsoever to dop with Rolls Ropyce or the RAF. It was in US service, not British service.

This supports your view that 80inHg was only to be used with ADI. Which is strange, since the -7 was rated for +25psi boost dry.

Now the V-1650-7 was rated RM.10SM. The -9 was rated RM.16SM.

The R = Rolls-Royce, M = Merlin, S = fully supercharged, M = medium suprcharged.

The -7 and -9 were not developed in isolation from Rolls-Royce. They were developed in consultation with them, as can be seen by them having the Rolls-Royce development rating.

I was not talking about RM.17M engines, I was talking about the P-51H. It ran a C-1650-9 and -11 only. No other engines were delivered with the planes.

You were talking of bench and development engines. Of which teh RM,17Sm is one.

What do you mean' whay of the test engines?" Go read what I wrote. I said the test engines never flew. That's as far as it went. I made no other claims.

So why put it in?

The P-51H cannot climb at 4000 feet per minute at 2000 feet. At 67 inches it went from 3370 feet per minute at 13400 feet down to 2400 feet per minute at 23100 feet. At 80 inches it went from 4590 feet per minute at 8300 feet down to 2150 feet per minute at 21500 feet. It could get close to 4000 at 90 inches but, after initial tests, was not allowed 90 inches in servcice. The max allowable was 81 inches ... with ADI. All the above numbers were at critical altitude from flight test reports. It got worse everyhere else, but that doesn't make for good reading in a sales pitch, does it?

Here is some data for the P-51D and P-51H climb rates at 67.0inHg:

Alt (ft)	P-51D MAP	P-51D ROC	P-51H MAP	P-51H ROC
0	67	3600	67	3200
4800	67	3600
5000	66.5	3575	67	3285
10000	56.3	2925	67	3350
13800			67	3395
15000	47.2	2275
16000	67	3200
19000	67	3200
20000	65.2	3050	67	3060
25000	55.5	2375	67	2750
26700			67	2640
30000	46.4	1700	59.4	2275
35000	37.7	1000	49.4	1510
40000	29.8	325	40.6	440
41600	27.5	100

P 51D Performance Test
P-51H Performance Test

Note that the FTH (critical altitude) for the -7 in D is 4,800ft in MS and 19,000ft in FS gear. Gear change is at ~15,000ft.
The FTH for the -9 was 13,800ft in MS and 26,700ft in MS gear. Not sure when teh gear change was, as the data shows the manifold pressure maintained up to FTH in FS gear.

The -7 is shown to be a lower altitude engine, hence the better RoC down low. But its advantage is short lived.

The P-51D climbs to 20,000ft in 6.6 minutes, the P-51H in 6.1 minutes. The D gets to 30,000ft in 10.9 minutes, the H in 9.85. The D is faster to 10,000ft, 2.9 minutes vs 3.0.

Both had wing racks but no external load. The take-off weight for the D was 9,760lbs, including 21USG of oil, 185USG fuel and full ammo.
The takeoff weight of the H was 9,484lb with "full fuel" and ballast for full ammo load. Given the empty weight difference, teh H was relatively more heavily loaded for these tests.

This shows the hp of the engines and highlights the different characteristics of the -7 and -9.

Alt (ft)	V-1650-7 MAP	V-1650-7 hp	V-1650-9 MAP	V-1650-9 hp
0	67	1780	67	1503
4800	67	1730
5000	66.5	1720	67	1548
10000	56.3	1470	67	1590
13800			67	1622
15000	47.2	1232
16000	67	1580
19000	67	1500
20000	65.2	1455	67	1320
25000	55.5	1225	67	1340
26700			67	1347
30000	46.4	1025	59.4	1209
35000	37.7	855	49.4	1012
40000	29.8	700	40.6	830

Your chart is a sales pitch for the P-51H.

Maybe so, but WEP is used for teh F*F's excellent climb rate too. No doubt including ADI.

And the 471 mph was at 90 inches which, again, was cut to 81 inches in service, where the max speed was 467 mph or so.

I'm sure that the MAP was cut during service because the war was over. The RAF did the same - no point flogging the engines any more than they have to.

As for the last paragraph, what are you thinking? In peactime climbing at reduced rates is normal and is done all the time. If you need to push the climb rate, it is for an operational reason related to unuknown incoming aircraft, and that is no longer peacetime, it is intercept time to address a potential threat to the task force. All bets are off until peaceful intent is established. Otherwise, conserve the equipment and the expendable fuel, and woe be unto you if you drop a drop tank in peacetime without a declared emergency.

Peace time climb rates don't reflect the aircraft's capability. That said, it is entirely in keeping with what I said in my last paragraph - it depends on the situation.

As these were warplanes, what they do in peace time is of little interest. What they are capable of in combat conditions is. You can bet your bottom dollar that if the US was still at war with Japan into 1946 that the P-51H would climb gently when going off on B-29 escort missions. If, however, they were set up to intercept high altitude fast moving raiders they would use a combat climb, and use teh ADI to get up there PDQ.

 

[wuzak]

Just to show you I can interpolate, I have filled out the missing values for the jp table.

Alt (ft)	V-1650-7 MAP	V-1650-7 hp	V-1650-9 MAP	V-1650-9 hp
0	67	1780	67	1503
4800	67	1730		1546
5000	66.5	1720	67	1548
10000	56.3	1470	67	4590
13800		1289	67	1622
15000	47.2	1232		1564
16000	67	1580		1515
19000	67	1500		1369
20000	65.2	1455	67	1320
25000	55.5	1225	67	1340
26700		1157	67	1347
30000	46.4	1025	59.4	1209
35000	37.7	855	49.4	1012
40000	29.8	700	40.6	830

 

[GregP]

I'm surprised you argee with what I said, and I'm assuming you meant P-51, not P-61. If we're talking about the Black Widow, all before is for naught and isn't even on topic. Personally, I've never made a typo! That's my joke for the post.

About the graphs of HP versus height, they don't advertise the bad points, they always spec at the best points. Nobody gives you the lower HP numbers ... they always give the best, meaining the top of all the lines, just before they decrease. But you know that.

I mentioned the test stand engines because I wanted to. I think like me, not like you, and reserve the right to do that just like you do. But you know that.

Later R-2800's are not irrelevant since they served alongside the P-51H's concurrently until both were gone. Concurrent service MAKES them relevant. Neither of these birds fought in WWII, so a WWII timeframe is uttrerly irrelevant by definition ... they weren't there and didn't fight in that war. What IS relevant is the fact they were in service at the same time in peacetime. Being peacetime, neither got much development that ever made it to the service squadrons. They basically served as delivered until retired and sold as surplus or overhauled and sold to other nations.

I am talking about US airplanes using US-built Merlins, not anything Rolls-Royce ever made. We didn't use RR engines ... we used Packard Merlins. The limitations of their operation were different due to having different national air arms dictating the limits, and the parts are mostly NOT interchangeable between British and US Merlins. Some are, not all. We blew up our fair share of Merlins, as did the British. Mostly not since the Merlin is a great engine if ever there was one and was quite reliable if treated well, but they DID fail, and they failed catastrophically mostly at WER power or working up to it. Hence the desire to save the engine by all crew chiefs and pilots who were away from a friendly airfield or countryside.

The point I was trying to make about cruise climb is thaht nobody much climbed at WER unles they were in combat. They would climb at reduced power or, at most, normal power. Not mil power or WEP/WER. But you know that and are protesting just to protest. We aren't all that far apart and you know that, too.

You just like to disagree somewhat like I do at times, too. I have no doubt the P-51H COULD climb very well if pushed hard. The data prove that. My point was that the Bearcat could be pushed hard, too. When it is, the P-51H doesn't get away except very slightly in top speed. In acceleration, climb, roll, and turn, the P-51H is no better than the F8F ... -1 OR -2, and is really not as good in many areas. A bit speedier, but only at the risk of blowing the engine, which nobody would do unless combat dictated it.

But you know that, too.

Cheers!

 

[wuzak]

About the graphs of HP versus height, they don't advertise the bad points, they always spec at the best points. Nobody gives you the lower HP numbers ... they always give the best, meaining the top of all the lines, just before they decrease. But you know that.

I don't know what you mean.

The numbers I posted are for WEP (dry), with maximum boost of +18psi. It shows when the power is lower as well as higher. Not sure what you mean by "bad points".

I am talking about US airplanes using US-built Merlins, not anything Rolls-Royce ever made. We didn't use RR engines ... we used
Packard Merlins. The limitations of their operation were different due to having different national air arms dictating the limits, and the parts are mostly NOT interchangeable between British and US Merlins. Some are, not all. We blew up our fair share of Merlins, as did the British. Mostly not since the Merlin is a great engine if ever there was one and was quite reliable if treated well, but they DID fail, and they failed catastrophically mostly at WER power or working up to it. Hence the desire to save the engine by all crew chiefs and pilots who were away from a friendly airfield or countryside.

The parts were mostly interchangeable between Rolls-Royce and Packard Merlins. Packard for US service used SAE spline prop shafts wheras RAF bound engines used the SBAC spline shaft. The supercharger gearbox was different (Farman on RR built aircraft and epicycic on Packards) and the carby was different.

Rolls-Royce drove the development of the Merlin, and Packard mostly followed.

I have no doubt the P-51H COULD climb very well if pushed hard. The data prove that. My point was that the Bearcat could be pushed hard, too. When it is, the P-51H doesn't get away except very slightly in top speed. In acceleration, climb, roll, and turn, the P-51H is no better than the F8F ... -1 OR -2, and is really not as good in many areas. A bit speedier, but only at the risk of blowing the engine, which nobody would do unless combat dictated it.

You said several posts ago that the P-51H wasn't that big an improvement over the P-51D, especially in climb rate. I'm quite sure I proved that wrong.

As for the F8F-1, all its performance figures that are trumpeted are when being pushed with ADI and WEP, including its climb rate. So if the F8F's performance figures used are with maximum power (max MAP and ADI) then why shouldn't the P-51H's.

One thing to note is that the F8F had a low altitude engine, whereas the P-51H had a high altitude engine.

 

[drgondog]

The P-51H airframe was superior to the P-51D/B airframe - period.

The 1650-9 engine was the 1650-3 with heavier construction to be able to withstand higher boost pressures plus water injection plus Simmonds Boost Control unit for better management of boost pressures set by the pilot - at all altitudes. The engine had a speed density injection type carburetor.

The 1650-9A was simply the same engine with WI removed.

The P-51H was a superior airframe which resulted in a.) less weight, b.) lower weight for full combat load, c.) lower drag wing, d.) more directional stability at both take off and all flight regimes, e.)no aft cg issues due to extending the fuselage ~ 13" and reducing the fuselage tank from 85 gallons to 50 and increasing the wing tanks from 180 to 205. The P-51H had better visibility over the nose for deflection shooting as well as taxi, take off and landing. The P-51H was slightly more economical in cruise speeds than the P-51B with the 1650-3 and superior to the 1650-7 when comparing P-51B/D with full combat load to P-51H full combat load. The throttle and RPM settings were slightly different from each other at different altitudes, depending on engine differences in comparisons.

the P-51H out climbed the P-51B and P-51D at same power settings and far exceeded both in service ceiling at normal power and comparable internal load. The placard for the -9 at 80" was 7 minutes and this stress was common without engine changes, particularly while testing the P-51H climb to 25,000 feet (=6.7min @ max power from SL) as an interceptor.

The wing area of the P-51H was 236 sq ft compared to the B/D of 233 so one can expect that turn performance is also slightly better based on lower wing loading due to a.) Gross Weight and b.) greater wing area.

The post war saw removal of the WI capability as the P-51H was retired from interceptor role and steered toward Fighter Bomber tasking as they moved into National Guard and Reserve units. The engines were then the -9A. The P-51D's also used -9A from time to time as they do today.

The F8F is the only conventional fighter built in US that is comparable/slightly better/slightly worse than the P-51H



The P-51H was superior structurally as it was designed for actual target Gross Weight in combat operations, whereas the P-51B/D had both grown significantly over the original XP-51 design loads and stress allowances.

There is a big difference in trying to do comparisons based on Warbird operations versus combat ops -with respect to fuel and use of WEP. It is disingenuous to make comparisons between different warbirds or even racers as both of those categories are out of the envelopes flown by combat pilots -simply because nobody wants to risk blowing up an engine or failing the bird structurally.

As usual I have a different experience anecdotally from Greg in that I never talked to an Air Force pilot that flew both that liked the P-51B/D over the H.

 

[Shortround6]

Something to remember about today's war birds (and perhaps even more true with warbirds in the 60s/70s) is that they often flew with the wrong engines. How many flew with the correct self sealing fuel tanks (30-70 year old rubber?) armor and weapons load (how many carry ballast if the guns are dummies?

Many a F4U or P-47 used to fly with ex commercial airline R-2800 "C" series engines (DC-6, Convair 340/440) as they were cheap and easy to find vs the "correct" B series engines. I have no Idea what the engine situation was in F8F-1s but the F8F-2s used a special "C" series engine ONLY used in the F8F-2.

I don't know if some of the warbirds flying now have gone back to more "historical" engines but if they have it is even more reason not flog the engines to no good purpose. The "C" series engines having much better cooling, strong parts and in the later engines even different length connecting rods.

 

[wuzak]

I have no Idea what the engine situation was in F8F-1s but the F8F-2s used a special "C" series engine ONLY used in the F8F-2.

The F8F-2's R-2800-30W was an E-series engine according to White.

 

[Shortround6]

You are correct. I was in a hurry

The only other "E" series engine was the one used in the F4U-5 and it used a totally different supercharger.

The "C" series engine used in the F8F-1 was also used in a number of other military aircraft and while it may be close to a certain model commercial engine I don't know which one it would be.

 

[GregP]

We'll have to disagree on the superior airframe part. But that's OK. I still like them all. At similar boost the D and H perform similarly. If you add a 2200 HP V-1650-11 at 81 inches to a P-51D, I bet you get great performance, too.

Before you trash me too badly for that statement, you might recall the two fastest P-51s in the entire history of the planet are both P-51Ds. That would be Voodoo and Strega in no particular order. They aren't exactly "stock," but neither are they P-51Hs either.

There are numerous small aerodynamic changes to be sure, but the biggie is a 3850 HP Dwight Thorne-inspired hybrid engine that has a Merlin engine case and cranksahft, but not much Merlin anything else. The rods are Allison G-series, the pistons are custom, and the valves are very likely custom, too. The mags have been replaced and the generator is new along with numerous other small bits.

It says "Rolls Royce" on the T-shirt and valve covers, but it just ins't the case in reality.

As for rate of climb, you might recall that a stock grumman F8F-1 Bearcat seta record in 1946 by climbing from a standstill on the runway to 10,000 feet in 94 seconds. That is in military condition, with armament and no modifications. The current rate of climb record is held by Rare Bear, set in 1972, and is standstill to 3000 meters in 91.6 seconds. Mustangs, including the P-51H aren't in the record book for rate of climb, but it is littered with Bearcats.

The current world seppd records is held by a Rare Bear at 528.33 mph. Several planes today, including the Bear, can break that record. The reason it hasn't been broken to date is the cost of doing so. There is no other reason for not besting that record. Rare Bear, Strega, and Voodoo can all hit 540 mph straight and level on the course. It is a question of whether or not they DO so while staying together for a backup run in the other direction.

 

[drgondog]

We'll have to disagree on the superior airframe part. But that's OK. I still like them all. At similar boost the D and H perform similarly. If you add a 2200 HP V-1650-11 at 81 inches to a P-51D, I bet you get great performance, too.

No question - but recall that the handling characteristics of the B/D increasingly degraded with increased HP (ditto the 109 and 190 - hence one of the reasons for the plug in the 190D. The increased fuselage length of the H solved not only the aft cg problem but also high speed yaw issues that led to all the mods to the B/D such as reverse rudder boost, etc. It also made take off more benign with respect to rudder feed.

As to other aspects of the airframe, your contention would be that the P-51D combat Gross weight Limit load of 6.6G is somehow superior to the comparable 7.5G of the P-51H? OK. Or that the lowered thrust line and top of cowl giving the pilot more visibility over the nose is not a notable airframe differentiation? Or the ability to carry a full fuel load in the aft tank of the P-51H with no adverse aft CG issues not a notable airframe distinction? Or the increased yaw stability across the performance envelope of the H over the B/D not worthy of a 'Plus"?

Before you trash me too badly for that statement, you might recall the two fastest P-51s in the entire history of the planet are both P-51Ds. That would be Voodoo and Strega in no particular order. They aren't exactly "stock," but neither are they P-51Hs either.

You may recall how few H's exist to toy with as racers as well as the aerodynamic mods that have brought Voodoo and Strega to the efficiency they have and perhaps contemplate that nothing about them lends to long range escort or fighter bomber tasking. I also suspect that Hinton would not look favorably on racing P-51D's with full internal fuel including aft fuselage tank as a condition for the race.

There are numerous small aerodynamic changes to be sure, but the biggie is a 3850 HP Dwight Thorne-inspired hybrid engine that has a Merlin engine case and cranksahft, but not much Merlin anything else. The rods are Allison G-series, the pistons are custom, and the valves are very likely custom, too. The mags have been replaced and the generator is new along with numerous other small bits.

It says "Rolls Royce" on the T-shirt and valve covers, but it just ins't the case in reality.

Hmm - do ya think that Funny Cars or Rails have stock Chevy, Chrysler or Ford engines? or wonder why? There must be a point here but it eludes me.


As for rate of climb, you might recall that a stock grumman F8F-1 Bearcat seta record in 1946 by climbing from a standstill on the runway to 10,000 feet in 94 seconds. That is in military condition, with armament and no modifications. The current rate of climb record is held by Rare Bear, set in 1972, and is standstill to 3000 meters in 91.6 seconds. Mustangs, including the P-51H aren't in the record book for rate of climb, but it is littered with Bearcats.

I don't think I argue this point as I have never seen an attempt to break this record. What I do know is that the spec has the 51H going from SL to 25000 feet in 6.7 minutes and a ROC in the 5500 fpm range in low blower critical altitude. I haven't seen any F8F specs for the climb to 25000 feet so have no basis for comparisons.

The current world seppd records is held by a Rare Bear at 528.33 mph. Several planes today, including the Bear, can break that record. The reason it hasn't been broken to date is the cost of doing so. There is no other reason for not besting that record. Rare Bear, Strega, and Voodoo can all hit 540 mph straight and level on the course. It is a question of whether or not they DO so while staying together for a backup run in the other direction.

And your point is?

 

[GregP]

The current records are held by Bearcats. You are probably right about the Few P-51H models out there, but Steven Hinton Jr. Says Strrega and Voodoo fly just fine with 3850 HP. Naturally they are flying at full down elevator trim at 500 mph, but the H-model would, too.

I can't say what the racers' Cdo is because I don't know, but whatever it is ... it would be hard to best even with an H-model aitrframe. Heck, A modified P-51H might BE faster, but we may never know.

All I can say right now is the Bearcat is definitely on top of the record book, with modified P-51D moels sitting right there, ready to challenge if the money magically appears. In an all-out speed record attempt, I lean toward the Strega-Voodoo side, but we all KNOW the Bear can hit 540 mph in a straight line, too. It wouldn't be an easy victory for any of the three planes.

Regardless of the above, if you are out of ADI, the P-51H performs just about like a P-51D, albeit a bit faster in top speed. Add in the V-1650-11 and the same would be true in climb rate, too, for the P-51D. And the P-51H didn't have much ADI to play with, so it was mostly right in the same perfromance arens as the P-51D.

That was and is my point. The biggest difference between them, performance wise anyway, was the engine and the extra 14 pounds of boost, not the aerodynamics.

 

[wuzak]

That was and is my point. The biggest difference between them, performance wise anyway, was the engine and the extra 14 pounds of boost, not the aerodynamics.

I thought the biggest difference between them was the 1,000lb difference in empty weight?

 

[GregP]

Not at all. The engine makes the difference.

Go to Reno once and ask EVERY unlimited pilot out there and they'll ALL tell you it's the engine. Sure, the rest helps, but only very slightly. A good fillet might add 1 -2 mph, but 400 more HP will blow that out of the water by a LONG way.

The WWII Merlins were making maybe 1,400 HP or more at 5,000 feet. The front running racers are making more than 3,000 more HP at 500 feet and there is NO aeroduynamic modification that comes even close to that. Go look at the speeds in 1964 where almost every racer out there was stock, and then go look at the speeds in 2014 in the Unlimited Gold class, where no single racer is stock. The biggest difference, by a very long mile, is horsepower.

In fact, the ONE Unlimited racer that shows this ina very BIG way is called Miss America. The airframe is largely but not entirely stock, but the plane has had progressively more HP in its various developments. Each and every increase in HP results in a faster plane. All the rest of the mods were quite minor by comparison.

Weight has almost nothing to do with it once the power surplus is enough, despite any protestations to the contrary. Once the power surplus is enough, weight is almost meaningless up to the point where it starts impacting the power surplus significantly. Of course, I'm talking reasonable weights, and am not thinking of a 16,000 pound P-51. If you have one of those, don't try to fly it. Rent it out as ballast or put it in a park for the kids to play on.