Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: batdog on August 13, 2001, 10:01:00 AM
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I was wondering...since we have Niki's,Dora's P-51D's and such... why dont we have a P-47M or N? I copied this off a web site... the M appeared in 44.
The P-47M was a special high-speed version of the Thunderbolt specifically evolved to counter the Fieseler Fi 103 (V-1) buzz bomb and the new jet- and rocket-powered fighters that were entering service with the Luftwaffe.
Four P-47D-27-RE airframes (serials 42-27385/27388) were taken off the production line at Farmingdale and fitted with the Pratt & Whitney R-2800-57(C) engine equipped with a larger CH-5 turbosupercharger. This new engine offered a war emergency power of 2800 hp at 32,500 feet with water injection. Air brakes were fitted underneath the wings to aid in deceleration during dives. These four converted P-47Ds were redesignated YP-47M.
This new engine installation was ordered into production in September 1944 for the last 130 P-47D-30-RE aircraft delivered by Farmingdale, the aircraft being subsequently redesignated P-47M-1-RE. The serial numbers of the 130 P-47M-1-RE Thunderbolts built were 44-21108/21237
The first P-47M was delivered in December 1944, and they were rushed to the 56th Fighter Group in Europe. However, engine problems delayed their use until the last few weeks of the war in Europe. Underwing racks were not fitted, as the P-47M was meant to be operated strictly as a fighter.
Performance of the P-47M-1-RE included a maximum speed of 400 mph at 10,000 feet, 453 mph at at 25,000 feet, and 470 mph at 30,000 feet. Initial climb rate was 3500 feet per minute at 5000 feet and 2650 feet per minute at 20,000 feet. Range (clean) was 560 miles at 10,000 feet. Armament was six or eight 0.50-inch machine guns with 267 or 425 rpg. Weights were 10,432 pounds empty, 13,275 pounds normal loaded, and 15,500 pounds maximum. Dimension were wingspan 40 feet 9 3/8 inches, length 36 feet 4 inches, height 14 feet 7 inches, and wing area 308 square feet.
Sources:
American Combat Planes, Ray Wagner, Third Enlarged Edition, Doubleday, 1982.
The American Fighter, Enzo Angelucci and Peter Bowers, Orion Books, 1987.
War Planes of the Second World War, Fighters, Volume Four, William Green, Doubleday 1964.
United States Military Aircraft since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.
The Republic P-47D Thunderbolt, Aircraft in Profile, Edward Shacklady, Doubleday, 1969.
Famous Fighters of the Second World War, Volume I, William Green, 1967.
Thunderbolt: A Documentary History of the Republic P-47, Roger Freeman, Motorbooks, 1992.
Hers's some info on the N...
The P-47N version of the Thunderbolt was the last version to be manufactured in quantity. It was a specialized long-range version built specifically for service in the Pacific theatre.
Four P-47D-27-RE airframes (serials 42-27385/27388) had been taken off the production line at Farmingdale and fitted with the Pratt & Whitney R-2800-57(C) engine driving a larger CH-5 turbosupercharger. This engine could produce a war emergency power of 2800 hp at 32,500 feet with water injection. These aircraft had been redesignated YP-47M and served as the prototypes for the P-47M series.
However, the war in the Pacific required fighter ranges even greater than did operations over Germany. In pursuit of better long-range performance, in mid-1944 the third YP-47M prototype (42-27387) was fitted with a new "wet" wing of slightly larger span and area. The aircraft was redesignated XP-47N. For the first time in the Thunderbolt series fuel was carried in the wings, a 93 US gallon tank being fitted in each wing. When maximum external tankage was carried, this brought the total fuel load of the XP-47N up to an impressive 1266 US gallons. This fuel load make it possible for a range of 2350 miles to be achieved.
The new wing also incorporated larger ailerons and squared-off wingtips. These innovations enhanced the roll-rate of the Thunderbolt and improved the maneuverability. The dorsal fin behind the bubble canopy was somewhat larger than that on the P-47D. However, the increased fuel load increased the gross weight of the aircraft. In order to cope with the increased gross weight, the undercarriage of the XP-47N had to be strengthened, which increased the weight still further. The maximum weight rose to over 20,000 pounds.
The XP-47N flew for the first time on July 22, 1944. Such was the USAAF confidence in the Thunderbolt design that they went ahead and ordered 1900 P-47Ns in June 20, 1944, even before the first XP-47N had flown.
The P-47N was destined to be the last version of the Thunderbolt to be manufactured. The first P-47N-1-RE appeared in September of 1944, and 24 were delivered by year's end. The P-47N-5-RE and subsequent batches had zero-length rocket launchers added. The R-2800-77 engine was installed in late production models such as the P-47N-25-RE.
The P-47N gave excellent service in the Pacific in the last year of the War, particularly in escorting B-29 Superfortress bombers in raids on the Japanese mainland. P-47Ns were able to escort the bombers all the way from Saipan to Japan and on many other long, overwater flights.
A total of 1667 P-47Ns was produced by the Farmingdale plant between December 1944 and December 1945, when the Thunderbolt line finally closed down. 149 more P-47Ns were built by the Evansville factory. V-J Day cancellation of 5934 Thunderbolts brought production of the type abruptly to an end.
Performance of the P-47N-5-RE included a maximum speed of 397 mph at 10,000 feet, 448 mph at at 25,000 feet, and 460 mph at 30,000 feet. Initial climb rate was 2770 feet per minute at 5000 feet and 2550 feet per minute at 20,000 feet. Range (clean) was 800 miles at 10,000 feet. Armanent included six or eight 0.50-inch machine guns with 500 rpg and two 1000-lb or three 500-lb bombs or ten 5-inch rockets. Weights were 11,000 pounds empty, 16,300 pounds normal loaded, and 20,700 pounds maximum. Dimension were wingspan 42 feet 7 inches, length 36 feet 4 inches, height 14 feet 7 inches, and wing area 322 square feet.
Serials of the P-47N were:
44-87784/88333 Republic P-47N-1-RE Thunderbolt
44-88334/88883 Republic P-47N-5-RE Thunderbolt
44-88884/89083 Republic P-47N-15-RE Thunderbolt
44-89084/89283 Republic P-47N-20-RE Thunderbolt
44-89284/89450 Republic P-47N-25-RE Thunderbolt
45-49975/50123 Republic P-47N-20-RA Thunderbolt
Sources:
American Combat Planes, Ray Wagner, Third Enlarged Edition, Doubleday, 1982.
The American Fighter, Enzo Angelucci and Peter Bowers, Orion Books, 1987.
War Planes of the Second World War, Fighters, Volume Four, William Green, Doubleday 1964.
United States Military Aircraft since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.
The Republic P-47D Thunderbolt, Aircraft in Profile, Edward Shacklady, Doubleday, 1969.
Famous Fighters of the Second World War, Volume I, William Green, 1967.
Thunderbolt: A Documentary History of the Republic P-47, Roger Freeman, Motorbooks, 1992.
[ 08-13-2001: Message edited by: batdog ]
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Yup, addition of the M model would be very nice for Jug lovers.
Not to nitpick, but there is also info out there that says that the prototype for the M was in existence over a year prior to the V-1 threat.
"With the coming of June '44, something besides the invasion of France was on the minds of the people of Britain. On night of June 12-13 the Germans launched the first of over 6,700 V-1 flying bombs. This was the first of Hitler's Vengeance Weapons. They created near panic in Britain. While not exceptionally effective weapons in a strategic sense, they were effective at pulling RAF resources away from prosecuting the war to defending the airspace over Britain. Moreover, the V-1 (and later V-2 ballistic missile) did more to hurt British home front morale than did the air Blitz of 1940-41. The British government turned to the United States for assistance.
Eventually, Republic was informed of the British request for a high speed interceptor specifically to chase down and destroy the V-1. Remarkably, Republic already had a solution in hand. This would take the form of the the incredibly fast P-47M-1-RE. Let's go back more than a year and see how Republic came to have this speedster in their vest pocket when the British inspired inquiry arrived."
"The XP-47M was, essentially, developed collaterally with the XP-47J. The J was fitted with a high output version of the P&W R-2800. Specifically, the R-2800-57. This engine made 2,800 hp @ 2,800 rpm at 35,000 feet. This is in War Emergency Power. The aircraft actually attained 507 mph at an altitude of 34,300 feet. 2,800 hp is 133% of rated power. At military power (100%), the XP-47J could sustain 470 mph. 435 mph was attained at 81% of it's rated power (1,700 hp). All performance figures were obtained at 34,300 feet. The J model was an especially good climbing fighter too. It had a climb rate at sea level of 4,900 fpm. At 20,000 feet, it was still rocketing up at 4,400 fpm, and got there in 4 minutes, 15 seconds. Time to 30,000 feet was only 6 minutes, 45 seconds. Now that's an interceptor! Yet it had a usable range of 1,075 miles. Rather impressive performance. Nor was this a stripped down hotrod. It was fully armed and carried ballast in the wings equal to 267 rds per gun. The aircraft was flown to a height of 46,500 feet and was capable of a bit more."
"Right out of the starting gate, the XP-47M the horse to beat in terms of speed. The XP-47M proved to be nearly as fast as the XP-47J. 488 mph was obtained on at least one flight. The official maximum speed is 470 mph. However, over-boosting the engine could tweak another 15 to 20 mph out of the big fighter. Some may find this next tidbit hard to swallow, however, the test documents still exist.
During durability testing of the C series R-2800 by Republic, it was decided to find out at what manifold pressure and carburetor temperature caused detonation. The technicians at Republic ran the engine at extreme boost pressures that produced 3,600 hp! But wait, it gets even more amazing. They ran it at 3,600 hp for 250 hours, without any failure! This was with common 100 octane avgas. No special fuels were used. Granted, the engines were largely used up, but survived without a single component failure. Try this with Rolls Royce Merlin or Allison V-1710 and see what happens.
As mid June of 1944 arrived, so did the first of Germany's Vengeance weapons. Flying at speeds right around 400 mph., the V-1 was not easy to intercept prior to flying over populated areas, where knocking it down could have a worse effect than leaving it alone. Many of the RAF's latest fighters were thrown into intercepting the "Buzz Bombs", preferably over the English Channel. Tempests, late Mark Spitfires and even the jet powered (but not especially fast) Meteors were put to work intercepting the deadly "Doodle Bugs"."
"Upon the USAAF being informed of the XP-47M, three YP-47M development aircraft were immediately ordered. These were built using P-47D-27-RE fighters straight off the production line. Having already logged hundreds of flights with the XP-47M, beginning in mid 1943, Republic had a big leg up in terms of development time. Actual production P-47M fighters used the P-47D-30-RE as the basic airframe.
The production P-47M fighters did not reach operational status until after many of the V-1 launch sites were over-run by Allied ground forces. Deployed to 3 squadrons of the 56th Fighter Group, the new fighter likely did not chase very many flying bombs. Inasmuch as most aviation historians claim that the P-47M was designed specifically to intercept the V-1, it will come as a surprise to them to learn that the prototype existed more than a year before the first V-1 was launched at Britain. Moreover, the P-47D, deployed in large numbers, was certainly fast enough to overtake the V-1. It was only coincidence that the XP-47M and the R-2800 C series engines were available when the V-1's began falling on London.
The new M models also suffered a fair amount of teething troubles. The C series engines suffered from high altitude ignition leaks and burned pistons. The 56th kept many of their older D models until the new M had its bugs corrected. Nonetheless, once sorted out, the P-47M was the fastest propeller driven fighter to see combat service in any Air Force in the ETO. Capable of speeds up to 475 mph, the M was a true "hotrod"."
I clipped and pasted the parts about the M model from this website:
http://home.att.net/~historyzone/Seversky-Republic7.html (http://home.att.net/~historyzone/Seversky-Republic7.html)
Modelling an M shouldn't be that hard, as it was based on the D-30, which we already have.
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At the rate HTC adds aircraft there is no doubt we will get them. The only question is when?
Hooligan
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Cool though they are, we curentaly have more US stuff than any other Nation,I think we nead to let Japan, Itatly and Rusha, catch up a bit before adding another P 47, err US plane.
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S!
I love my Jugs but...
I don`t see the point of adding an aircraft like the P47M which only totaled around 300 aircraft in service, when planes like the Spit IXLF (over 3,000 produced) or the 109G6 with the DB605AM (methanol), or the P-47D Razorback with the paddleblade prop are not modelled.
The same with the Do-335. This is a prime example of a prototype which was irrelevant in terms of wartime service.
And if the rumour of the P-51H turns out to be true, then the Sim might as well be re-named `Secret Weapons of Everybody", since we`ll no doubt be getting Bearcats and every other experimental one-off production model which ever hit the design board in the `40`s.
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S!
I take back my comments on the P-47N. There were a large number produced, and it saw quite a bit of service against Japan.
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Uhhh Brady, they tend to model more than ONE plane per release... :)
xBAT
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Yeah Batdog, but I tend to agree with Brady on this one...
If HTC can release anything BUT US and German planes for the next couple of releases (German Hvy bomber is an exception) the planeset will be that much better for it
SKurj
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Ahh but if they add the P-47M as a perk, at least the USAAF will have something to chase the Me 262 around with.
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Well, if you take a step back I seriously doubt that they ie HTC are going to suddenly add a plane to whatever they are adding now.
IF for whatever reason they do decide to add this 47 it will be in later versions.Also lets not forget that I am a 47/38 driver and I am very biased of course. It WOULD though make the JUG more feasiable for the MA when facing the likes of the more common better planes of the latewar set.
xBAT
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Funny thing is, batdog, we had NO clue the Jug was even in the works when they introduced it. Just a new version, and BAM! "Hey! They added a P-47!" :cool:
HTC is capable of adding a last second surprise, just to blow people's minds. They sure blew mine that day. ;)
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xBat, I too mostly fly Jugs, we have 3 now... I am happy with what we have and don't mind sacrificing the M/N at the moment so that the planeset can get filled out.
SKurj
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Originally posted by Buzzbait:
S!
I love my Jugs but...
I don`t see the point of adding an aircraft like the P47M which only totaled around 300 aircraft in service, when planes like the Spit IXLF (over 3,000 produced) or the 109G6 with the DB605AM (methanol), or the P-47D Razorback with the paddleblade prop are not modelled.
Only 125 P-47M aircraft were constructed. Initially, none were fitted with underwing pylons to limit aero drag. However, since these aircraft did not begin combat operations until after the V-1 threat had largely abated, they were pressed into routine escort and interdiction service with the 56th FG. While they lacked the pylons, the wiring, plumbing and hardpoints were in place. So, most of the fighters had pylons fitted at the 8th AF overhaul facility and were soon flying daily ops until the surrender.
While the superlative M would be a hoot to fly and would be just about the most potent piston engine aircraft in the AH stable, it really was not deployed in the adequate numbers to justify its inclusion while so many more significant aircraft have yet to be modeled. Now, if HTC decided to include the much more common N model, that's a different story. Being very nearly as fast as the M, the P-47N benefitted from its redesigned wing with slightly greater range than the P-51D and a higher rate of roll than any model of the P-47D.
It is my opinion that there are many other aircraft that should be considered before the P-47M or N are added to the plane set.
Yet, extremely limited production fighters such as the Ta 152 have been added, which baffles me. Especially when some of the more common Spitfire models have yet to be included. Moreover, the very limited selection of Allied Naval aircraft should be addressed as well.
My regards,
Widewing
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Originally posted by eddiek:
Funny thing is, batdog, we had NO clue the Jug was even in the works when they introduced it. Just a new version, and BAM! "Hey! They added a P-47!" :cool:
HTC is capable of adding a last second surprise, just to blow people's minds. They sure blew mine that day. ;)
It wasn't even a new version--it was a patch when they introduced the jug. :)
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"Only 125 P-47M aircraft were constructed"
Nitpicking here, but 130 were produced.
The 56th FG recieved them in December '44 and started using them in January. They had a lot of teething problems, mainly due to the electrical system.
It's worth noting that while loking at the factory performance, the 56th had already modified the wastegate on their existing P-47D's to the same manifold pressure as the P-47M (72"),so I'm not sure how big an improvement the P-47M really was. (The improved turbosupercharger would certainly have helped, though).
Also, while most books state that the P-47M only had 6 .50 cals, it was used with 8. (I dont know if they were installed at the factory or field).
The P-47N uses the same engine as the M, the main difference being the new wet clipped wing, improving the rollrate significantly.
While the pure performance numbers might not look as impressive as the M, one has to remember that it was carrying almost double the amount of fuel.
Daff
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Give me either one of these awesome beasts to kill 262's with please. :)
Guys... how about an American perk? We don't have one. I want one bad. The 47M or N would be the perfect choice.
BTW... I wouldn't be totally surprised if HTC slipped one into this build without telling us anyway. :D
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Originally posted by Daff:
It's worth noting that while loking at the factory performance, the 56th had already modified the wastegate on their existing P-47D's to the same manifold pressure as the P-47M (72"),so I'm not sure how big an improvement the P-47M really was.
This tale just goes on and on. Why don't you post somekind of hard evidence that the P-47Ds with R-2800 B-series engines could be succesfully hot rodded above say 65" without overheating problems and limiting service life of the engine to the couple hours. And if these hot rodded P-47Ds really existed, why they did not use them for V-1 hunt? Why on earth the P&W redesigned whole engine for the C-series if similar performance was available reliably with B-series engines? Why the Republic made the P-47M if the D could do same? The Pilots of the 56th FG were certainly pissed when they downgraded to the unreliable P-47M :D
gripen
[ 08-15-2001: Message edited by: gripen ]
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Originally posted by gripen:
This tale just goes on and on. Why don't you post somekind of hard evidence that the P-47Ds with R-2800 B-series engines could be succesfully hot rodded above say 65" without overheating problems and limiting service life of the engine to the couple hours. And if these hot rodded P-47Ds really existed, why they did not use them for V-1 hunt? Why on earth the P&W redesigned whole engine for the C-series if similar performance was available reliably with B-series engines? Why the Republic made the P-47M if the D could do same? The Pilots of the 56th FG were certainly pissed when they downgraded to the unreliable P-47M :D
gripen
[ 08-15-2001: Message edited by: gripen ]
Jealousy :)
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Same principle applies to all here, gripen.
Naudet posted about the 109 and 190 "pilot comments" about the turn rates. Are we supposed to take their word, just because they were LW fliers? ;)
Widewing posted that he had interviewed USAAF personnel who corroborated the wastegate mods......and he also explained the reason for no "official" documentation. Even in wartime, even when your life depended on your plane's ability to fight and still get you back home alive, you were expected to adhere to "official" policy. Nevermind that turning up the engine power on your plane kept you alive, to "admit" to doing so on an official level meant possible courtmartial. Just goes to show how different the perspective was for the front line pilots and the REMF's. Front line, you did what you had to do to stay alive. REMF's looked at the little #'s on paper and said "make it work with this", even if those #'s made no sense in the real world of combat.
Whether or not you believe it, that is your choice. You don't have to. FWIW, I personally believe things gotten firsthand from pilots who were there. Robert Johnson, Gabreski, others who flew the Jug felt it was at least the equal of anything the Germans had in the air, after the Jug was set up to fight and live. IMO, the P47M was merely the application of the lessons learned in combat, i.e. engine mods for higher performance.........
You say we need hard data. Define hard data for me? Hard data to me means not only factory spec sheets, but also pilot accounts and crewchief/member accounts of what the plane was like. Test pilots did not push the planes to the limits of the flight envelope like combat pilots did. If the crewchief "turned up the wick" on his assigned plane, to be honest, he didn't give a flip about the regs, unofficially, of course. :p His main concern was seeing that bird and it's pilot come back home to roost, and if he had to do it on the sly, so be it.
My thinking is that to get the most accurate picture of what a plane was like, you need to look at both "official" stuff and also the "unofficial" stuff. That way you get a better perspective on what it was like for the pilots, not just what the bean counters "said" it was like.
Though it would cause an uproar, I wish Pyro would set up a Jug just for the CT, with paddle prop, water injection, and higher than stock MAP and HP........just to see how it fared and if it would really honestly upset game balance. To be sure, til they adjusted, the LW guys would be freaking out, but I don't think the plane would be untouchable. It would make it more challenging for sure, but not invincible. And to offset the Jug mods, give the 109G6 the MW50 and GM-1, just to be fair to all involved. But, those are just MY wishes.......... ;)
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Well, nix the above idea for the CT out......
Just got off the phone with HiTech, and I did not realize just how much work would be involved in modifying even seemingly simple performance mods/enhancers. Those guys have to redo the FE, and IMHO, they already do a bang-up job at this game. I kinda feel guilty after making the posts about the performance mods to the various planes........if they added all the stuff we say we want ( and by "we" I mean all of us, LW, USAAF, USN, RAF, IJN, etc.) they would never get anything done.
My suggestion: Fly what ya like, like it is, enjoy it as it is. HTC can't please everyone all the time, and when it gets right down to it, all we are doing is splitting hairs.
Aces High is best sim out there, bar none.
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If these mods to the jug were common then there will be documentary evidence. If you want HTC to model this, then evidence has to be presented to them. I could say that I interviewed both German and US vets and they all agreed that a) the jug could not exceed 100mph or b) that it easily exceeded 500mph. I certainly hope that HTC wouldn't just take my word for it. They need better evidence than just my (or anybody's) word. Surely some of this stuff about modifying waste-gates etc... is written down somewhere in somebody's memoirs, or a Republic memo, or a book about the P-47 etc... Point HTC to the documentation so they can evaluate it and perhaps they will make the mods to the FM some day.
Hooligan
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Originally posted by gripen:
This tale just goes on and on. Why don't you post somekind of hard evidence that the P-47Ds with R-2800 B-series engines could be succesfully hot rodded above say 65" without overheating problems and limiting service life of the engine to the couple hours. And if these hot rodded P-47Ds really existed, why they did not use them for V-1 hunt? Why on earth the P&W redesigned whole engine for the C-series if similar performance was available reliably with B-series engines? Why the Republic made the P-47M if the D could do same? The Pilots of the 56th FG were certainly pissed when they downgraded to the unreliable P-47M :D
I suspect that the reason you are struggling with over-boosted engines is that you don't understand how and when over-boosting occurs.
Simply stated, just because an engine is capable of extreme power output does not mean that it will operated continously at those manifold pressures.
Let's assume that Bob Johnson is accurate when he reports being able to obtain 72 in/hg in WEP. How long would he operate the engine at such high boost pressure? The answer is, minutes.
My car's engine can operate safely at 7,500 rpm, 900 rpm above recommended redline. How often will I do that? Not frequently. Moreover, I won't run the engine at that speed for very long either.
Likewise, a pilot flying a P-47 with reworked wastegates, will only over-boost the engine when faced with an emergency situation. At all other times, he will adhere to normal power settings.
Does this make more sense now?
My regards,
Widewing
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Well by that explanation, HTC would need to do some recoding to make the souped up engine work (on any plane), rather than just allowing higher manifold pressures for unlimited time. As it is now, there is no penalty for running full throttle all the time... engines won't overheat and die on you.
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Widewing, hate to say it, but, the ball is in your hands now.
If I recall correctly, you stated here or on another board that you had interviewed Pappy Gould, Johnson's crewchief, and other pilots who were there.
Maybe it's time to share some of their comments on the P-47 and factory vs actual engine settings? :D PLEASE????? ;)
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"Surely some of this stuff about modifying waste-gates etc... is written down somewhere in somebody's memoirs, or a Republic memo"
First, apperantly all the Republic's documents regarding the P-47 was destroyed when Fairchild bought them up...
Secondly, Johnson did state in an interview that he had the wastegate modified to 72" and could do 300mph IAS @ 30k.
There's one former crew chief on the P-47 Advocates board that's been hinting that a book will coming out shortly, which will explain these things in detail.
About engine life: P&W ran a benchtest, with a a severly overboosted engine, and it ran for a long time (36 hour straight?). While it was certainly ready for the scrapyard afterwards, it did do it without any problems.
Gripen:
"Why on earth the P&W redesigned whole engine for the C-series if similar performance was available reliably with B-series engines? Why the Republic made the P-47M if the D could do same?"
If you re-read my post, you would see it was stated as a question.
Daff
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Daff:
Not all of the republic documents are destroyed. Somebody took some of them home. Some crewchief kept a few folders as memento's and they’re moldering in an old footlocker in his grandson's attic. Some of them ended up in Air force archives. Transcripts of interviews with names and dates etc… exist somewhere.
I really have only one point in this:
Some documentary evidence must exist and if these modifications are going to be modeled in AH a sufficient body of this evidence must be discovered and presented to HTC. This isn’t Widewing’s problem either. He doesn’t even play AH so why should he go to all the work to gather the documents and make them available?
To be useful, any discussion of this issue past this point must take the form of: “Where do we find the necessary documentation so that we can present it to HTC?”
If somebody really wants this change to AH they should be getting in contact with the crewchief you mention and asking to copy his sources.
I wish you the best of luck.
Hooligan
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S!
The discussion of hotrodding of P-47`s etc. is also in this post:
http://www.hitechcreations.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=9&t=002340 (http://www.hitechcreations.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=9&t=002340)
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Well, well, these hot rod tales appear to be my best troll so far here ;) Anyway...
eddiek,
Just look current D-9 thread, first I pointed out with easily verifyable evidence that Naudet's theories about Mustang's and 109s turning performance were wrong or based on selectively choosed data. After that I have pointed out several times that there should be hard data to prove his theories, just like I have done here. And actually I'm willing to believe that some P-47D were really modified without further evidence, but according to my sources, anything over say 62-65" should have showed up in the overhaul statistics. And still, HTC crew have made very clear that there should be data which can be verified. BTW actually there is documented data about field modifications atleast on the Airacobra and P-51.
Widewing,
Be cool!
Daff,
Well, the 56th FG was very near to convert to the P-51 because they had so much problems with the P-47M. Actually some P-51s allready arrived to the units for training. The 56th needed better fighter than the P-47D they had.
gripen
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Originally posted by gripen:
Daff,
Well, the 56th FG was very near to convert to the P-51 because they had so much problems with the P-47M. Actually some P-51s allready arrived to the units for training. The 56th needed better fighter than the P-47D they had.
gripen
All units were replacing their existing AC inventory with Pony's. The 56th was equiped with the P-47 till the end because of circumstance and hi level decisions. As the war closed and the allies were staging op's out of mainland Europe bases, it only made sense for the 56th to stay with the jug. All the parts, labor, and other logistical stuff required to maintain them were present. The pony units that were prior P-38 and P-47 units were for the most part already transitioned to the pony while still in England.
I do not doubt however that the 56th would have been transitioned if the war would have went on. Parts and logistics to support the large number of existing P-51 units could be divied out to them.
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Originally posted by eddiek:
Widewing, hate to say it, but, the ball is in your hands now.
If I recall correctly, you stated here or on another board that you had interviewed Pappy Gould, Johnson's crewchief, and other pilots who were there.
Maybe it's time to share some of their comments on the P-47 and factory vs actual engine settings? :D PLEASE????? ;)
Actually, I conducted several long telephone interviews with Bob Johnson several months before his unexpected death while visiting family in Lawton, Oklahoma. Bob related that Pappy Gould had incorporated some changes to the waste gates (Probably involving either stretching, replacing or shimming the springs) that allowed the engine to pull insanely high manifold pressures. Gould also hand polished exhaust ports, carefully fitting intake tubes and exhaust stacks to maximize flow characterisitics. Gould also waxed Johnson's Jug to a high gloss, using fillers to eliminate surface irregularities in the skin of the fighter. This last item was good for 5-8 mph on any WWII vintage fighter. Other factors include prop indexing. All P-47s arriving in a combat zone did so with the props indexed for 93 octane fuel. This was because there were many locations away from the war zone where 100-130 avgas was not available. Smart crew chiefs would immediately re-index the prop, which would allow the highest MAP to be pulled. I do not believe that the USAAF ever issued a technical directive that this be done. Largely because the possibility still existed that lower octane fuels may still be used.
I will be contacting the president of the P-47 Pilots Association to see if he has any members that can shed additional light and be specific about field modifications.
By the way, you asked me about Republic's testing of the C series R-2800 engines, where they ran the engines a very high boost, generating up to 3,600 hp. The test documentation survived in the custody of C. Hart Miller until it was obtained by Lowery Brabham. With the death of Brabham, his papers became the property of his family, who still maintained the materials as late as 1994. The aicraft used to perform the extreme high power tests was S/N 42-27385. Subsequent to completing the testing, both the airframe and R-2800-57 were judged to be "war weary". The worn out engine was returned to Pratt & Whitney for teardown and evaluation, the Jug was relagated to hack duty. This was largely due to using this aircraft to test the new dive flap installation. As a result, the airframe had been subjected to more than 100 high speed dives, frequently exceeding Mach .80, or damn near 600 mph. Dr. Herb Fisher performed many high speed dives while testing transonic props for the Propeller Division of Curtiss-Wright. He established the P-47's terminal dive velocity at an insane Mach .83, which is really honkin'. I have some of that test data and have posted it on the web.
My regards,
Widewing
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Allison V-1710 could do 72" MAP in it's standard form, no mods necessary. RAAF pilot said he pulled six feet of mercury for about 15 minutes while running from Japanese fighters in his P-40. Reason he could do that is because that engine(like most US and UK engines) had no automatic boost control. This sort of thing is probably why we don't have 100% realistic engine controls.
[ 08-16-2001: Message edited by: juzz ]
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Many thanks, Widewing. The opportunity to interview many of these people has passed, and I apologize if I am imposing on you. You just seem to have made all the right connections, and already have a lot of information in hand, or have knowledge as to where it is.
Thanks again. :D
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The aircraft actually attained 507 mph at an altitude of 34,300 feet.
LOL, mach 0.76 in a level flight with a prop driven plane.
Even the world record machines didnīt reached more than mach 0.6 - 0.65.
Donīt believe everything. At mach 0.76, no propeller will produce much power anymore.
niklas
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Originally posted by niklas:
LOL, mach 0.76 in a level flight with a prop driven plane.
Even the world record machines didnīt reached more than mach 0.6 - 0.65.
Donīt believe everything. At mach 0.76, no propeller will produce much power anymore.
niklas
Niklas, I suggest you rethink your statements. These numbers were recorded by calibrated airspeed indicators, oscillographs and instrument cameras. Moreover, the performance numbers were signed-off by the USAAF, who supervised the prototype testing, which was initially performed out of Republic's Farmingdale, Long Island facility. 507 mph at 34,300 feet was certified by the USAAF. Later, when the aircraft was tested at Langley, it could only manage 489 mph. A tear-down inspection of the R-2800-57 revealed burned valves on virtually every cylinder, eventually determined to have been caused by an improperly rigged mixture control.
If you find the XP-47J incredible, consider the XP-72. This prototype achieved 490 mph @ 25,000 ft, and did so with an engine making nearly 500 hp less than the production version (R-4360). Rate of climb was just about 5,300 fpm and engineering estimates placed maximum speed at greater than 510 mph.
My regards,
Widewing
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your calibrated airspeed indicator may work correctly at normal mach numbers, but not at mach numbers > 0.6. And film cameras only film the error, so what?
Dive Tests usually recorded the altitude loss over time, this was often the only possible method to get TAS.
If you want to fly relly fast with transsonic speeds, then fly LOW!
490mph @ 25k makes more sense than 507mph@34k!
http://buerger.metropolis.de/luftwaffe/flight/compressibillity/flight_compress.html (http://buerger.metropolis.de/luftwaffe/flight/compressibillity/flight_compress.html)
read those pages, youīll find even the critical mach number for the P47 in it...
niklas
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Originally posted by niklas:
your calibrated airspeed indicator may work correctly at normal mach numbers, but not at mach numbers > 0.6. And film cameras only film the error, so what?
Oh, I see now... The engineers at Republic and Langley were idiots! Who would have guessed?
The fact is that the XP-47J was fitted with a 22 inch long extended air-data probe precisely for the purpose of eliminating error.
Dive Tests usually recorded the altitude loss over time, this was often the only possible method to get TAS.
Incorrect. In the case of the XP-47J, an air-data probe with pressure transducers and onboard analog time correlated recording via oscillograph and film were used to collect speed data. This data was then reduced postflight by precision calibrations with corrections for bias, compressibility, and position error. This data was then analyized by a team of four engineers and reviewed by NACA. Virtually the same equipment and methodology was employed to confirm the first supersonic flight of the Bell XS-1 (X-1)just 4 years later. NACA employed one addition tool to support their conclusions. This was a theodolite radar, producing yet another analog record. A radar was not used to track the XP-47J. However, all the radar did was to confirm, not establish actual airspeed.
If you want to fly relly fast with transsonic speeds, then fly LOW!
490mph @ 25k makes more sense than 507mph@34k!
Are you saying that true airspeed is less at 34,300 ft than it is at 25,000 feet, based solely upon altitude?
http://buerger.metropolis.de/luftwaffe/flight/compressibillity/flight_compress.html (http://buerger.metropolis.de/luftwaffe/flight/compressibillity/flight_compress.html)
read those pages, youīll find even the critical mach number for the P47 in it...
I am quite familiar with Gus Pappas. During his tenure at Republic, he was instrumental in cleaning up the design of the XP-47B, as well as the P-43 and XP-47 (Allison powered lightweight prototype never advancing beyond mockup). If my memory serves me well, Pappas was one of the advocates who insisted that it would be impossible for an aircraft to exceed Mach 1 due to the enormous pressure rise associated with transonic speeds. Obviously, he was very wrong. I believe that it was Pappas who refused to accept German research into swept wings, and lost much of his luster when the relatively low powered XP-86 slipped through Mach 1 with ease.
His remarkable claim that the P-47 could reach Mach .90 was conclusively proven wrong when post war (1947-49) testing of a P-47D-30-RE established beyond doubt that the Thunderbolt could not exceed Mach .833 under any circumstances. Why? Because at this speed the propeller enters the deep transonic range, with the shock wave quite literally preventing air flow through the prop. In effect, the propeller becomes a giant circular airbrake.
My regards,
Widewing
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I didnīt called the engineers idiots.
Where did the calibration happened? Near sealevel, with 20°C?? How can you know that at -80°C in very thin air, where ice particles etc. can influence the instrument, everything is working still as good as near sealevel?
They did a radar tracking? How did they know about the current wind in 35k?
Are you saying that true airspeed is less at 34,300 ft than it is at 25,000 feet, based solely upon altitude?
This can happen, yes. Itīs all a function of mach number in those heights with such high speeds.
The german comet had itīs top speed in only 10000ft, though his engine produced more thrust in 20k compared to sealevel.
Pappas was not the only one who didnīt see a way to pass through the barrier of sound. People of this time had sometimes strange ideas, some even thought that the only way to do it is with the help of nuclear energy.
the Thunderbolt could not exceed Mach .833 under any circumstances. Why? Because at this speed the propeller enters the deep transonic range, with the shock wave quite literally preventing air flow through the prop. In effect, the propeller becomes a giant circular airbrake.
Exactly. And you want to tell me that the Thunderbolt did mach .76 in a level flight, without the help of gravity? Just look at the mach number of the propeller tip...
I would like to see the naca report, or some original graphs, but i would be suprised if you can show me some docs.
niklas
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Hmm so know we are refuting the results of an actual testflight?...guess Yeager never did break the soundbarrier, then :D
The winds will be irrelevant, if you do a IAS to CAS conversion...and it doesnt get much colder than -56 C' @ 34k. (As the temperature pretty much stops dropping above 24k).
Daff
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Originally posted by niklas:
I would like to see the naca report, or some original graphs, but i would be suprised if you can show me some docs.
Try:F-47 dive data (http://home.att.net/~Historyzone/DiveChart.html)
My regards,
Widewing
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Daff, ya gotta remember that some folks think the only accurate tests were conducted by the Luftwaffe. Put two test results out in front of them, one conducted by the LW, the other conducted by USAAF, RAF, whatever, and they will dispute whatever the Allied tests show (unless it says a LW plane was better than an Allied one), and claim the LW test as holy and undeniably accurate (unless it shows an Allied plane as better in any way).
If this was the "real world", I might find the arrogance and attitude of Aryan superiority insulting......as it is, it's good for a chuckle and maybe a raised eyebrow.
All the light hearted, and some not so light hearted, claims of total LW superiority, their planes were better in every way, etc....when you start talking about RL things done to the planes, that all changes. Witness the Rumble this year.....which 2 planes were singled out as the cause of the Axis defeat.......P47D-11 and the Spit. RAF fans want a later model Spit, or one closer to RL with correct wings, engine, armament. "You have to perk that" is some LW'ers reply, even tho they have 1944-45 aircraft available to them. :p
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Originally posted by niklas:
I didnīt called the engineers idiots.
Where did the calibration happened? Near sealevel, with 20°C?? How can you know that at -80°C in very thin air, where ice particles etc. can influence the instrument, everything is working still as good as near sealevel?
They did a radar tracking? How did they know about the current wind in 35k?
I believe that you are ill imformed. For starters, temperature will stabilize at just about -56°F, regardless of altitude. Secondly, properly instrumented test aircraft will be fitted with thermocouples to sense outside air temp. I suspect that you don't have any knowledge or understanding about how flight testing is performed, nor the methodology of collecting and evaluating data. No crime in that. However, it does make your argument seem somewhat more than silly.
Exactly. And you want to tell me that the Thunderbolt did mach .76 in a level flight, without the help of gravity? Just look at the mach number of the propeller tip...
Let's stop and think about tip speeds. The XP-47J had a reduction gear ratio of .47 to 1. In other words, the propeller turned .47 revolutions for every revolution of the crankshaft. So, at 2,700 rpm, the prop is turning at 1,269 rpm. Measuring 12.8 feet in diameter, the extreme tip travels roughly 40.2 feet/rev. 1,269/60 = 21.15 rev/sec. Therefore, 21.15 x 40.2 = 850 ft/sec would be the rotational tip speed. The speed of sound at 34,300 ft is very near to 670 mph, or 983 ft/second. Rotational tip speed is right around Mach .87. However, the propeller is also moving forward. It's actual motion is best described as being helical. The equation used to calculate this is: Vtip = Sqrt(Vrotation^ + Vfwdvel^). So,
850^ = 722500 + 743^ = 1274549. The square root of 1274549 = 1,128 ft/second. Therefore, the extreme prop tips are at Mach 1.14 at 507 mph. Working the equation for various blade stations, one discovers that about 17% of the prop is experiencing a substantial drag rise. Nonetheless, the loss of efficiency is somewhat less than that. Don't depend on Gus Pappas' drag rise calculations. They do not account for the chord to thickness ratio of the prop blades, which generally was in the 3-5% range. Compare that to 8% for the Bell XS-1 wing. Indeed, low ratio wings suffer minimally from compressibility, and propellers even less so. The limiting factor as concerns prop driven aircraft was not so much the drag rise of supersonic tip speeds, but the drag rise of the prop disk as a whole.
My regards,
Widewing
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like ive said before..if it was produced during the war but low numbers or v late addition BUT IT SAW ACTION it should be available at resonable/high perk cost.if it didnt see action very expensive perk.Same for all planes.The rarer the harder to get i say.
plus if any plane used too much a temporary perk status.(this being dynamic tour/tour or map/map)
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Originally posted by eddiek:
Witness the Rumble this year.....which 2 planes were singled out as the cause of the Axis defeat.......P47D-11 and the Spit.
Wrong ! It was about pilots, not planes. Rumble was won 15:0 by Allies due to better pilots and squads fighting against poorly organized and harshly put together pilots. Also, many of the experinced types on our side were missing.
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Widewing,
The R-2800 C-series was rated at 2800rpm, I don't know how it was rated at the XP-47J. Also the propeller of the XP-47J seems to be (according to the pictures) similar large one as in the later D models, 13ft or more (spinner is also huge). Then it also should be noted that compressebility starts to affect to the propeller around tip speed mach O.8 see this (http://naca.larc.nasa.gov/reports/1938/naca-report-639/) NACA report.
gripen
[ 08-17-2001: Message edited by: gripen ]
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Widewing, i actually wanted to see docs about the 507mph flight.
But if the max. mach number of a p47 was really 0.833, then it confirms my opinion. So thx for the link.
Daff: Noone is interested in the speed that was actually reached in the X-1, and whether the speed claim was 50mph to high or to low compared to the true speed. The important point is that it broke through the barrier of sound. Few people remember the topspeed of the X-1 today.
When you do radar measurements, the wind is not irrelevant. That was my point, not IAS > TAS.
Temperature starts to stop over 36k btw. But -80°C was indeed a bit too much if you compare it to the standard atmosphere :) (though atmosphere conditions can vary a lot)
With 2800rpm the tip is travelling at mach ~1.18. That means from a radius of ~9ft on(70% of total propeller radius) the propeller blade is already moving supersonic.
No way to reach 0,76 in a level flight this way. It would be interesting to read the original report.
niklas
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Originally posted by gripen:
Widewing,
The R-2800 C-series was rated at 2800rpm, I don't know how it was rated at the XP-47J. Also the propeller of the XP-47J seems to be (according to the pictures) similar large one as in the later D models, 13ft or more (spinner is also huge). Then it also should be noted that compressebility starts to affect to the propeller around tip speed mach O.8 see this (http://naca.larc.nasa.gov/reports/1938/naca-report-639/) NACA report.
gripen
This report must be evaluated within the context of its scope. The purpose was to determine the effect of compressibility on props during takeoff and climb. It establishes that prop pitch angles are in the 20°-25° range, not nearly as flat as would be found for maximum speed. This increase in the angle of attack will induce compressibility effects at a considerably lower speed. Moreover, the blade designs tested represent those available long before the Curtiss 834 blade design (used on the XP-47J) existed. This prop was slightly smaller in diameter than the standard unit used on production Jugs. Many historians report that the prop measured 13 ft in diameter, but Higginbotham, who headed the Powerplant Engineering Department insisted that it measured 152 inches in diameter. It had rounded tips, but a chord to thickness ratio of just 4.5% at the outboard stations.
Therefore, NACA report 639 is not directly applicable, and will be misleading when applied to paddle blade props in flat pitch.
One item overlooked when considering the performance of the XP-47J was exhaust thrust. Unlike the P-38 installation, the Jug's turbo layout was not sensitive to back-pressure. Other considerations include the fact that Test Pilot Richie's notes include reference to pulling 72 in/hg MAP on his speed run. Engineers extrapolating the horsepower curve believed that Richie had managed approximately 3,200 hp during the run. We know that the R-2800-57 generated between 400 and 650 lbs of exhaust thrust, which certainly augmented speed capability. In the case of the XP-47J, this was extrapolated up to nearly 800 lbs of thrust at 76 in/hg (72 in/hg is normal WEP rating).
A call to Warren Bodie resulted in his telling of Republic Test Report No. 51 dated January 1945. This test report states that 502 mph was attained after correction. This report was signed off by General L.C. Cragie, Chief of the USAAF Engineering Division. The "Offical Performance Summary of the XP-47J aircraft" should be available via the Air Force Historical Research Agency at Maxwell AFB.
I flew as a Flight Engineer on Convair 240 (C-131F) type aircraft in the mid 1970s. This aircraft was powered by a pair of R-2800 engines and incorporated thrust augmentation utilizing exhaust gases routed rearward through a venturi and diffuser system. A genuine increase of 22 knots airspeed was gained by this harnessing of exhaust gas velocity. You can expect at least that much gain in the XP-47J, perhaps considerably more.
My regards,
Widewing
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Widewing,
If you want to argue that the propeller of the XP-47J acted significantly different at high speeds (something like 80% efficiency around tip speed mach 1) than propellers in that NACA report, why don't you show some verifyable evidence? (please, not your own articles)
Your exhaust thrust argument is also interesting. AFAIK most of the turbocharged engine's exhaust thrust is used for the turbo and wasted in the long piping. Again, evidence please.
But now you claimed at least one reference which at least might be available, thank you.
gripen
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Originally posted by gripen:
Widewing,
If you want to argue that the propeller of the XP-47J acted significantly different at high speeds (something like 80% efficiency around tip speed mach 1) than propellers in that NACA report, why don't you show some verifyable evidence? (please, not your own articles)
Go to: http://naca.larc.nasa.gov/reports/1952/naca-tn-2859/naca-tn-2859.pdf (http://naca.larc.nasa.gov/reports/1952/naca-tn-2859/naca-tn-2859.pdf)
Your exhaust thrust argument is also interesting. AFAIK most of the turbocharged engine's exhaust thrust is used for the turbo and wasted in the long piping. Again, evidence please.
This data can be found in the document listed earlier. Get a copy. Oops, I forgot, you want everyone else to to do your leg work, right?
My regards,
Widewing
[ 08-18-2001: Message edited by: Widewing ]
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Widewing,
That NACA document really contains data about a propeller which could do very well at high tip speeds and the propeller of the Thunderscreech or Tu-95 might do even better. But actually I was interested about the proppeller of the XP-47J which resembles those propellers in the NACA 639 (blade shape, thick profile at the root). Also your own statement that the proppeller of the P-47 (similar late Curtiss design?) worked like a air brake at mach 0.83 speaks against your own arguments.
Which mentioned source supports your claim that exhaust thrust gained at least 22knots for the XP-47J after losses in the turbo and piping?
BTW a book called the Secret Years by Tim Mason claims that the Mustang III did it's top speed (450mph@28k) at reduced rpm (2800) due compressibility.
gripen
[ 08-19-2001: Message edited by: gripen ]
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Originally posted by gripen:
Widewing,
That NACA document really contains data about a propeller which could do very well at high tip speeds and the propeller of the Thunderscreech or Tu-95 might do even better. But actually I was interested about the proppeller of the XP-47J which resembles those propellers in the NACA 639 (blade shape, thick profile at the root). Also your own statement that the proppeller of the P-47 (similar late Curtiss design?) worked like a air brake at mach 0.83 speaks against your own arguments.
This is exactly what I expected from you. Let's be honest, if an American stated that the sun rises in the east, you would require documentation and argue "how can you you prove this if it's overcast?" Just another Luftwaffe Mafia troll.
I present you with verifiable documentation, you pooh-pooh it stating that doesn't represent the Curtiss design (as if you actually had a clue what your were talking about, but we know better). You refer back to a report of tests with obsolete, mid- 1930s propeller designs. The report I cite was declassified and released in 1952, but written in 1947, is a rewrite of an earlier report declassified and released in 1948 but written in 1943. There is usually a 3 to 5 year lag between the internal report being written, and it's being released to the public. Indeed, some reports released in 1947 discribe tests conducted in 1941.
For the balance of your uninformed comments, I suggest you review the drag rise curve for various propellers, and you will see that virtually every design suffers at speeds above Mach .80, and this always becomes the greatest factor in limiting speed.
Which mentioned source supports your claim that exhaust thrust gained at least 22knots for the XP-47J after losses in the turbo and piping?
Your reading comprehension skills require some polishing. I never made any such claim. I reported the speed gain via exhaust thrust augmentation for the Convair 240.
For reference, see Bodie's "Republic's P-47 Thunderbolt", page 232. Also see Republic Test Report No.51.
BTW a book called the Secret Years by Tim Mason claims that the Mustang III did it's top speed (450mph@28k) at reduced rpm (2800) due compressibility.
I do not know where Mason gets his data from, but the USAAF defined the Mustang's (P-51B) maximum speed at 430 - 450 mph depending which test report you read. However, each test reports the use 3,000 rpm. Furthermore, the fact that the Mustang's propeller measures just 11'2" or 11'1" in the case of the Aero Products prop (on the Dallas built P-51D, designated P-51K), it seems highly unlikely that compressibility was a noteworthy factor.
My regards,
Widewing
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Widwing, i think you know very well that your 2859 report is no help in a discussion about a high speed flight in 35k.
They tested the propeller at forward mach numbers of ~0,6, while the XP-47J claims a mach number of 0,76.
They even mention in the report:
"The highest tip speeds ... were obtained at comparatively low forward speed, and it should be pointed out that such data may not be adequate when used in estimation efficiencies for higher forward speeds because the radial variation of Mach number will not be correct"
If you look at real flight tests with higher forward mach numbers (usually 0,7) and high tip mach numbers, you can see a significantly higher loss of propeller efficiency (1784 report, or L4L07)
Furthermore they tested in a wind tunnel near ground under ideal conditions. No thin air, no icing problems, no yaw movements etc..
400lb exhaust thrust for a usual supercharged engine with 2000hp in 30k is realistic. 800lb with 3000hp for a tubocharged is imo a bit too much, the energy for the turbo is not for free.
Nevertheless, if you compare the thrust "produced" by the weight during dive tests (14000lb) to 800lb, it still canīt explain imo the high mach number of 0,76. I know that the gradient of drag/mach is steep after the critical mach number, but the difference between 0,76 and 0,833 is imo too small to be realistic.
niklas
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A normal P-47 that produced 2800 hp @ 34000' would be expected to reach 530 mph. The fact that it *only* does 504 or whatever, means that compressibility or loss of propeller efficiency *is* in effect.
The 530 mph figure was extrapolated from a P-47 being capable of 420 mph @ 25000' with 2000 hp in *standard* atmosphere.
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Widewing,
The propeller described in the NACA 2859 is very much different if compared to one in the XP-47J and this can be verified simply from the pictures.
Your statement about exhaust thrust can be verified above ("You can expect at least that much gain in the XP-47J, perhaps considerably more.")
The sources used by Mason are well known and publically available; A&AEE reports which are available from the Public Records Office or the library of the Boscombe Down.
Mason writes:
"The effect of propeller tip speed was measured and a reduction of 200rpm (reducing tip Mach No from 1.07 at 3000rpm to 1.03 at 2800) gave an increase of 10mph (true)."
There is also similar claim about the Corsair Mark II (F4U-1D) but no exact values for the speed increase or engine ratings:
"It was found that reducing to climb rpm increased high level speeds and climb, caused, it was thought, by high propeller tip speed of mach 1.165 at 33000ft and low intake efficiency, particularly in the climb."
gripen
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yes wells, and if we try to explain everything with extrapolations and simple formulas, weīll come f.e to the result that with 800lb thrust from the exhaust gases, the P47 wouldnīt have needed a propeller at all in 35k to fly :)
btw, thatīs the reason why i donīt understand that some people donīt want jets. Every prop driven plane, especially with turbocharger, is so close to a jet, if you compare the mechanical design. And they used the backpressure of the exhaust gases, which made them all "little" jets. But this is OT for this thread ;)
Itīs obvious that the mach effect was the limiting factor. I just donīt want to believe 0,76. And i want to see the original report :)
niklas
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Originally posted by niklas:
Widwing, i think you know very well that your 2859 report is no help in a discussion about a high speed flight in 35k.
They tested the propeller at forward mach numbers of ~0,6, while the XP-47J claims a mach number of 0,76.
They even mention in the report:
"The highest tip speeds ... were obtained at comparatively low forward speed, and it should be pointed out that such data may not be adequate when used in estimation efficiencies for higher forward speeds because the radial variation of Mach number will not be correct"
If you look at real flight tests with higher forward mach numbers (usually 0,7) and high tip mach numbers, you can see a significantly higher loss of propeller efficiency (1784 report, or L4L07)
Furthermore they tested in a wind tunnel near ground under ideal conditions. No thin air, no icing problems, no yaw movements etc..
400lb exhaust thrust for a usual supercharged engine with 2000hp in 30k is realistic. 800lb with 3000hp for a tubocharged is imo a bit too much, the energy for the turbo is not for free.
Nevertheless, if you compare the thrust "produced" by the weight during dive tests (14000lb) to 800lb, it still canīt explain imo the high mach number of 0,76. I know that the gradient of drag/mach is steep after the critical mach number, but the difference between 0,76 and 0,833 is imo too small to be realistic.
niklas
Niklas, I doubt that the forward velocity is significant when the sum of rotational and forward velocity are considered.
You would be surprised at the relatively low loss of velocity in a turbo system. A properly designed turbo system, that is. According to one source, the turbo hood was instrumental in increasing exhaust velocity, while the CH-5 turbo, being designed for high back-pressure systems, had only a minor effect on said velocity. Our own work with centrifical type systems clearly demonstrated a significant pressure rise in front of the unit, but little change in velocity down stream. Granted, these were not turbo systems, but the comparison seems to survive reasonably well. Again, the system vent is critical to function. Generally, there is little available to aid in the research of the design of the P-47's turbo hood.
As to the difference in drag between the two numbers under discussion, examine a drag rise curve. You will see that drag rise between .76 and .83 is huge.
My regards,
Widewing
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Originally posted by gripen:
Widewing,
The propeller described in the NACA 2859 is very much different if compared to one in the XP-47J and this can be verified simply from the pictures.
Yada, yada, blah, blah, blah.....
The Curtiss 834 was designed specifically to minimize drag rise at high sub-sonic speeds. Fisher wrote on the extensively in the late 1940s. Moreover, the 836 paddle blade used on production aircraft also followed this approach.
Your statement about exhaust thrust can be verified above ("You can expect at least that much gain in the XP-47J, perhaps considerably more.")
You're right. However, this is not rocket science. An aircraft with more than twice the the flat plate area, and three times the weight, producing about 700 lbs of exhaust thrust gained 22 knots in airspeed. Is it not reasonable to expect the XP-47J to gain at least this much? Even if you limit the total thrust to 400 lbs, it should still gain more than 22 knots. Whether or not the calculated value of 765 lbs was attained, is irrelevant to the fact that 400 lbs should produce a substantial speed increase, that is not effected by prop tip speed, but by power output alone.
The sources used by Mason are well known and publically available; A&AEE reports which are available from the Public Records Office or the library of the Boscombe Down.
Mason writes:
"The effect of propeller tip speed was measured and a reduction of 200rpm (reducing tip Mach No from 1.07 at 3000rpm to 1.03 at 2800) gave an increase of 10mph (true)."
Once I was able to find some time, I ran Mason's numbers and produced the following
theoretical tip speeds at 440 and 450 mph at 28,000 ft.
440 mph, 3,000 rpm (1,500 rpm for the prop) rings out as Mach 1.079. 450 mph at 2,800 rpm (1,400 for the prop) shows Mach 1.041.
This tells me two things.
1) Mason's numbers are spot on.
2) The theoretical formula is very accurate.
So, this tends to indicate that the XP-47J might have gone even faster had Richie reduced his rpm..... Not exactly the point you were hoping to make, is it? :D
My regards,
Widewing
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Widewing,
You should show evidence that the propeller of the XP-47J did well at Mach 1.18, so far you have not. But the A&AEE tests show that the problem existed at much lower tip speeds.
Your exhaust thrust statement was very much of from reality.
Your tip speed calculations are again wrong, because you are using wrong reduction gear ratio (the Mustang III had 0.479 reduction gear).
And the tests of the A&AEE clearly prove that propellers (1943 era) loss large amount of their efficiency a lot before mach 0.8, therefore there can't be huge difference in propeller efficiency (from positive to negative) between Mach 0.76 and 0.83.
You are wasting bandwidth.
gripen
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Originally posted by gripen:
You are wasting bandwidth.
gripen
:rolleyes:
Well, somebody sure is. I don't think it's WW, though.
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Originally posted by gripen:
Widewing,
You should show evidence that the propeller of the XP-47J did well at Mach 1.18, so far you have not. But the A&AEE tests show that the problem existed at much lower tip speeds.
Why is it that you cannot consider the possibility that the speed recorded reflected prop thrust loss? After all, the speed has been accepted by virtually every aviation authority extent. Obviously you have an agenda that precludes rational thinking if it undermines your "a superior race produces superior aircraft" mentality.
Your exhaust thrust statement was very much of from reality.
Nonsense. Kindly prove otherwise.
Your tip speed calculations are again wrong, because you are using wrong reduction gear ratio (the Mustang III had 0.479 reduction gear).
Then Mason's numbers are, in fact too high.
And the tests of the A&AEE clearly prove that propellers (1943 era) loss large amount of their efficiency a lot before mach 0.8, therefore there can't be huge difference in propeller efficiency (from positive to negative) between Mach 0.76 and 0.83.
There is a huge difference... Here's a novel idea, try researching it beyond superficial reading.
You are wasting bandwidth.
There's bandwidth a'plenty. However, it does appear that I am wasting my time discussing anything with you. Again, you have an agenda, and will ignore anything that conflicts with it. I suppose the next thing I can expect from you is a denial that the holocaust happened, right?
Indeed, you are the typical weasel who behaves rudely in the safety of cyberspace. So, do us all a favor and sod off.....
Widewing
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Widewing,
Well, if you read carefully what I have written in this discussion, you will notice that I have not questioned 500mph speed claim by the Republic. Infact I'm mostly having fun and also collecting nice written material for future discussions about the supposed 3200rpm rating of the P-38L and propeller tip speeds in that case. That exhaust thrust discussion just came as a nice little bonus. And actually some respected aviation writers seem to have some doubts about that mach 0.76 claim like F.H. Dean.
And then to the exhaust thrust. First it should be noted that you made a statement so it's generally your problem to prove it. But anyway, here you are. The Mustang could gain in the best case 30-40mph for it's top speed by the exhaust thrust which in that case was somewhere around 300-400lbs. It should be noted that the in-line engines can utilize exhaust thrust better than the radial engines because the exhaust stacks can be made very short, which means that the thrust pulse from the cylinder can be used more efficient without hammering this pulse to the walls of the long piping typical for the radial engines. This is probably one of the main reasons why mechanically supercharged in-line engines did better than similarly supercharged radial engines at high altitudes despite both utilized exhaust thrust. So in the case of the XP-47J we can assume that in the best case there is something like 600-800lbs thrust available before the piping and turbo. Normally the turbo charged engines can't utilize exhaust thrust very well but in the case of the XP-47J the exhaust of the turbocharger was constricted to create backpressure to utilize exhaust thrust at least in some degree (as you correctly noted). So to this point everyone agrees, but now to the losses. First this backpressure itself causes a little loss in the cylinder exhaust, but not much, maybe couple %. More important loss is caused by the nature of the closed system itself when varying pressure of the exhaust pulses is transformed to the steady backpressure, this means that a large part of the peak pressure of the exhaust pulse is hammered to the walls of the pipes. Again it's difficult to estimate amount of the loss but 10-30% might be close. Then comes that long piping itself which cause some loss, not very much, couple % again. Then comes the turbo which needs something like 700-800hp at 34k, and that might eat 40-50% of the remaining exhaust thrust. So good estimate for the available exhaust thrust should be somewhere around 200-400lbs, probably closer smaller value.
So in the best case there was about same exhaust thrust available as for the Mustang but much higher drag coefficient (XP-47J about 0.036 at mach 0.75 vs P-51D about 0.022 at mach 0.70) and about 50% more drag area. The net gain might be around 10-20mph in the very best case. But why to speculate when there is data available, the USAAF published at 1946 a report which discussed these issues (Final Report of Developement, Testing and Acceptance of the Republic XP-47J airplane). Actually one of the main issues discused in the report was back pressure and temperature of the exhaust system which caused a lot problems and also might caused performance differences between the tests of USAAF and manufacturer. Anyway, the difference between these test was about 12mph which fits to the estimates very well.
You still need some exercise in the tip speed calculations. You must know conditions to calculate exact mach values.
Well, actually I was hoping to see at least 50 lines about how great knowledge you have about these things and how minimal my knowledge is. But I was not disapointed when I saw that nazi and weasel stuff, thanks.
Toad,
I admit that I have been wasting bandwidth here and I also admit that I have been kidding someone. But as you probably know, discussing about the XP-47J is overall waste of bandwidth because it probably never flys in the AH. BTW did you know that I teached tip speed and roll rate theories to CC/Widewing? Want a prove? Try Google...
gripen
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Let's do "how many angels can dance on the head of a pin" next. Please, can we, huh, can we puh-leez?
:rolleyes:
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Originally posted by gripen:
Widewing,
Well, if you read carefully what I have written in this discussion, you will notice that I have not questioned 500mph speed claim by the Republic. Infact I'm mostly having fun and also collecting nice written material for future discussions about the supposed 3200rpm rating of the P-38L and propeller tip speeds in that case.
Well Harri, those of us who know you understand that you take great joy out of being a troll.
BTW, the P-38 has serious trouble with tip speeds at altitude, only exacerbated at full rpm. You might notice that the P-51J, powered by a mechanically supercharged version of the P-38's V-1710-119, also suffered by tip speed losses at 3,200 rpm.
(that's right, North American used full rpm limits) This problem would have been partially offset had the WPB accepted the P-38K with its .423 reduction gear and "paddle" blade props. According to Tony Levier, the K was about 40 mph faster at 40,000 ft than the P-38J-1-LO, on less horsepower.
That exhaust thrust discussion just came as a nice little bonus. And actually some respected aviation writers seem to have some doubts about that mach 0.76 claim like F.H. Dean.
I happen to know Diz Dean. He's a very nice man, sneaking up on 80 years old. Nonetheless, no one in the industry would classify Diz as a "writer". He's skilled at compiling data, making sense of test reports and explaining the engineering. However, a writer he isn't.
Now, where does he express doubts about Mach .76?
And then to the exhaust thrust. First it should be noted that you made a statement so it's generally your problem to prove it.
Says who? I offered the figures quoted by Higginbotham. He was the engineer in charge of Republic's powerplant engineering department. Proving what he wrote is easy, I have a copy of the letter. Proving their theory is not my concern. However, I put a great deal more credibility into Higginbotham's numbers than yours. He was there doing the testing.
Why is it every discussion with you results in you dropping your pants and producing a ruler? Any time someone makes a technical error, you attempt to pound them over the head with it. Are you insecure? There must be some deep-rooted cause of your dickhead behavior. I know the cure, but you're not up to it.....
(snip)
Well, actually I was hoping to see at least 50 lines about how great knowledge you have about these things and how minimal my knowledge is. But I was not disapointed when I saw that nazi and weasel stuff, thanks.
I suppose that I could have dedicated 50 lines as what an accomplished amazinhunk you are. However, your own trolling and condescending words have done that far more efficiently than I could have managed in 100 lines. BTW, where did I refer to you as a Nazi?
Toad,
I admit that I have been wasting bandwidth here and I also admit that I have been kidding someone.
That's double-speak for "trolling". Harri is a master at double-speak, carefully mis-interpreting English text to suit his need.
BTW did you know that I teached tip speed and roll rate theories to CC/Widewing? Want a prove? Try Google...
Geez Harri, "teached"? I admit, Harri did correct some misconceptions about roll rate theory. However, I do not recall ever discussing tip speeds. Unfortunately, Harri never endeared himself to the crowd at rec.aviation.military, for the same reasons he has not done so here. Harri is certainly well educated, and seldom misses an opportunity to point that out. What he lacks are the basic social skills found this side of a rattlesnake's hole. He won't let minor issues such as honesty and truth get in his way either. :rolleyes:
It's amusing, I run into guys like Harri at the gym all the time. Frequently, while I'm sparring, they ask to go a few rounds for a workout. Almost without exception, they attempt to take advantage of the "old man" by stepping up the effort, ignoring club rules about intensity and trying their best to knock me silly. What they don't know, but quickly discover is that the "old man" is in better shape and has much better skills than they. Too bad Harri isn't into competitive boxing... ;)
Naw, that would be too easy...
I am not an aeronautical engineer. Nor do I claim any special knowledge. I do, however, have access to a very large collection of personal correspondence, both written and recorded. In addition, I have access to Warren Bodie's huge collection. When I quote from any of these records, I cannot, nor am I inclined to "prove" what is stated. I am merely reporting what was said or documented. Now, if someone like Gripen has a problem with that, well, tough toejam.
My regards,
Widewing
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I admit that I have been wasting bandwidth here and I also admit that I have been kidding someone.
Was it entertaining for you?
But as you probably know, discussing about the XP-47J is overall waste of bandwidth because it probably never flys in the AH.
I would dare to say 80% of the people who come to this web board to read do so because a love and enthusiasm for WWII era aircraft. Not just because it would be a modelled virtual aircraft in the product.
How much nicer it could have been had you come to participate and share rather than put us all through a bout of self centered, attention seeking exercises.
Westy
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Westy dont you know resonable posts like yours dont at all contribute to their need to fight and fight and prove their sparkling genius and knowledge beyond all doubt........ :)
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Widewing,
Well, all I have done here is asking verifyable and valid sources and corrected some of your errors (like many times before), what's wrong with it?
About Dean's thoughts, see p. 304 in the AHT.
About tip speeds, you know well that I presented the problem to you with the calculations (including forward speed factor for both, normal P-38 and XP-38K) this can be verified with the Google.
About exhaust thrust, I mean your 22 knots gain claim, it was your problem to prove it.
Wow, now I got the a... word. Thanks.
Westy,
All I've done here is asking sources like the HTC crew wants and corrected some obivious errors. I'm sorry if you don't like it.
gripen
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Originally posted by gripen:
Widewing,
Well, all I have done here is asking verifyable and valid sources and corrected some of your errors (like many times before), what's wrong with it?
What's wrong with it? Are you that socially challenged? Re-read your obnoxious "like many times before" and tell me if you aren't blowing your own horn, insinuating that that you are the superior intellect. The simple fact that you never discuss ANYTHING for which you don't have data in front of you says more than all the horse manure you spout. Let's face it, you're an insecure. one dimensional clod. BTW, you're welcome in advance. When you were caught in historical errors, I never pummeled you for it.
About Dean's thoughts, see p. 304 in the AHT.
One vague sentence in a photo caption doesn't offer much in the line of "thoughts".
Nonetheless, he does not offer anything in rebuttal does he? Why not?
About tip speeds, you know well that I presented the problem to you with the calculations (including forward speed factor for both, normal P-38 and XP-38K) this can be verified with the Google.
I have had discussions on this topic with Adrian Camp on the newsgroup. I do not recall any such discussion with you. Can you supply dates and forum?
Wow, now I got the a... word. Thanks.
If it walks like a duck, and quacks like a duck..... You're welcome.
Widewing
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Widewing,
Please be cool. We have discused couple times about tip speeds, forexample try following:
Link (http://groups.google.com/groups?q=Harri+Jordan+P-38+tip+speed&hl=fi&safe=off&rnum=1&selm=3a5bdc63.13884845%40netnews.worldnet.att.net)
Anyway, I am really impressed about your social skills.
gripen
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FACT: Widewing is a proven, well recieved member of the AH community. He has made informative posts on various subject numerous times. He has huge amount of research at his hands, a large amount from Warren Bodie himself.
FACT: Gripen is certainly a well read, knowlegeable indiv about the above discussion. He seems to of developed some sort of hard-on for Widewing though. When ever Widewing post I see a post from Gripen disputing and saying...prove it. This is a rather easy postion to take and it is totaly lacking in risk... which might say alot more that people might see, ie troll?
xBAT
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Batdog,
I have had two discussions here with Widewing and in the both cases I have not started by replying to his message but Widewing have commented mine. In this discussion my first reply to Widewing was "be cool!" and another was a minor correction plus a source link.
gripen
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Grunherz, he even said he was trolling and trying to play around with Widewing. His purpose wasn't any actual discourse for the sake of discussion.
Widewing can take care of himself. I just wanted to add my .02 that I think his shenanigans were pathetic.
Gripen, I'm not falling for "All I've done here is asking sources like the HTC crew wants and corrected some obivious errors. I'm sorry if you don't like it." after the way you went about it and then later admitted to Toad and all you were having "fun" with Widewing.
Westy
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Originally posted by gripen:
Widewing,
Please be cool. We have discused couple times about tip speeds, forexample try following:
Geez Harri, I don't much mention of tip speeds. Moreover, I see absolutely nothing to back up your statement that you have "teached"[sic] me anything about the topic.
Anyway, I am really impressed about your social skills.
As you should be. :D
What bothers people about your behavior can be summed up quickly: You sit on the sidelines of a discussion, with the data necessary to end any debate on hand. Yet, you do not post the data. Rather, you prefer to lay in wait for someone to speculate or make an error. Then, from the trees you gleefully snipe at them with your typical arrogance. As you said, you were "having fun" at someone else's expense. That is very bad form, and indicative of the behavior expected from a dedicated jerk. Generally, when you have made historical errors, I did not jump on you, have I?
Let me use a boxing analogy.
When I am sparring with a fighter, be it a beginner or an experienced boxer, should I notice a defect in form I have two options on how I deal with it. Suppose the fighter dips his shoulder prior to throwing a punch, tipping me off to the impending blow.
My options are:
1) Stop the session and explain the error in form, helping the fighter to correct it.
Or,
2) I take advantage of the error in form to beat him to the punch, or hook over the low shoulder to his head, probably knocking him on his backside.
I choose #1. Why, because it is in the best interests of the young man to correct his faults without him suffering unnecessary punishment.
You on the other hand, would whack him on the head and chortle in self-exhortation.
#1 is the proper attitude for teaching. #2 is the attitude of a self-absorbed love muffin who can only feel good about himself by tearing down others.
Any resemblence to the accused is intentional.
Widewing
[ 08-21-2001: Message edited by: Widewing ]
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Westy,
Yes, I admited fun but that came after W focused on me.
gripen
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Originally posted by gripen:
Westy,
Yes, I admited fun but that came after W focused on me.
Hogwash. You posted this in response to another person's posting
"Well, well, these hot rod tales appear to be my best troll so far here Anyway..."
Typical weaseling, Harri. Why not be honest for a change? You know damn well that you deliberately search out my posts looking for an opportunity to demand some "proofs"[sic]. When you are offered the testimony of a combat pilot or secondary source data, you whine about that not be reliable and demanding original documents. Well, trolls have no right to demand anything. Indeed, you are the perfect example of those who would rather generate heat than light.
Your first post in this thread was an obnoxious reply to Daff, which started out with "This tale just goes on and on." Here you also demanded "Why don't you post somekind of hard evidence..?"
Indeed, your preoccupation with documents excludes the veteran pilots and grounds crews as a viable source of information. Without a doubt, these guys were there, saw and did things that will never turn up in test reports or flight manuals. That's the difference between a historian and your type. The historian (or someone who has been trained as such) excludes nothing relevant to history. This is because history is a giant mosaic, containing many different elements. You manage to eliminate much of those elements, preferring to focus on test data, which you can understand at the expense of first person accounts, which are the backbone of any study of historical events. Remember, all history has its root in human observation. Yes, even flight test reports. Perhaps your aversion to personal accounts results from an inability to relate to such things, a result, no doubt, of the fact that you have virtually no first-hand experience with actual aircraft. Maybe you should consider broadening the scope of your interest. As it is, it appears that you sit at your desk plotting your next ambush. Not much of a life....
Widewing
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Please. Enough. Let this die.
<ahem> Gentlemen.