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General Forums => Aircraft and Vehicles => Topic started by: Widewing on November 25, 2003, 06:49:15 PM

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Widewing on November 25, 2003, 06:49:15 PM

"As far as the 109, all of the German pilots loved that plane, but the FW-190 was harder to shoot down. Just like the controversy over the P-51 and P-47. The P-47 was faster; it just did not have the climb and range the Mustang did. But it had speed, roll, dive and the necessary ruggedness that allowed it to do such a great job in the Ninth Air Force. As far as aerial kills go, we met and beat the best the Luftwaffe had when we first got there. It was the P-47 groups that pushed them back, as I said before. The P-51s had the advantage of longer range, and they were able to hit even the training schools, hitting boys just learning to fly. As the war dragged on, many of the old German veterans had been killed--so much of the experience was gone. As far as the 109 versus 190 argument, the 109 had the liquid-cooled engine whereas the 190 had an air-cooled radial engine, much like ours. One hit in the cooling system of a Messerschmitt and he was going down. Also, none of the German fighters were as rugged as a P-47. When I was badly shot up on June 26, 1943, I had twenty-one 20mm cannon shells in that airplane, and more than 200 7.92mm machine-gun bullets. One nicked my nose and another entered my right leg, where the bullet split in half. I still have those two little pieces, by the way; they went in just under the skin. I had been hurt worse playing football and boxing. However, I had never been that scared, I'll tell you that. I was always scared--that was what made me move quick. "Hub" Zemke liked the P-51 because it had great range, but he put one in a dive and when he pulled out he ripped the wings off that airplane--that was how he became a POW. Adolf Galland, who was a very good friend of mine and who I had known since 1949, flew the Me-262 and loved it, but he still swore by the 109, although it was still easier to shoot down."

When Johnson states that the P-47 was faster than the Mustang, he is using his hotrodded P-47D-5-RE "Lucky", S/N 42-8461 for reference. Johnson's crew chief (Pappy Gould) worked magic on the R-2800. Johnson repeatedly claimed he could pull 72" of MAP and reported airspeeds of 470 mph TAS. Squadron-mates agreed that Johnson's Jug was far faster than any other P-47 in the 61st FS. Lt. Joe Powers flew Johnson's Jug on an escort mission and was horrified at the thought of pulling 72" MAP when Gould briefed him on the airplane. Powers reportedly firewalled the throttle on the return leg and was stupified at the speed. He simply ran away from the rest of the squadron. Even though Johnson's Jug was fitted with water injection, Johnson never used it. In an interview for the P-47 Pilots Association newsletter, Johnson stated, "I didn't need it, it was fast enough."

For the record, Johnson eliminated two of the top Luftwaffe aces in the west.

On October 8, 1943, he shot down and killed Hans Philipp. Philipp was the 12th highest scoring Luftwaffe ace of the war and was credited with 206 kills when he died. I believe that Philipp was the leading scorer flying in the west at the time of his death (although most of his victories came in the east).

On March 2, 1944 Johnson shot down and killed Egon Mayer (of JG 2), 102 kills, all in the west.

My regards,

Widewing

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: FUNKED1 on November 25, 2003, 07:15:37 PM

Are those Johnson's words or Johnson's words as told to/filtered by/revised by Martin Caidin?

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Nod on November 25, 2003, 07:58:47 PM

I read once by another pilot.......can't rember his name right now but he said "you know every pilot out there thinks his plane is the best and to him it is........well exept for the P-40 pilots"

In other words don't belive a pilots BS, I have read books where they belived the P-39 was the best plane of the war....yah i have to admit that the P-39 was ok, but it can't compete with a late model P-51, P-47, Spit, Yak, or a N1ki

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: davidpt40 on November 25, 2003, 08:04:16 PM

Quote

ub" Zemke liked the P-51 because it had great range, but he put one in a dive and when he pulled out he ripped the wings off that airplane--that was how he became a POW.

I thought he bent his prop up on the ground and had to land near a German airfield.

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Kweassa on November 25, 2003, 08:39:47 PM

The prop bending was Mr. Gabreski

Title: Re: Bob Johnson's observation of Luftwaffe fighters
Post by: HoHun on November 25, 2003, 11:39:47 PM

Hi Widewing,

>Also, none of the German fighters were as rugged as a P-47.

I'd say Johnson lacked the basis for a fair comparison as he (hopefully) didn't shoot down enough P-47s to get a good average ;-)

>When I was badly shot up on June 26, 1943, I had twenty-one 20mm cannon shells in that airplane, and more than 200 7.92mm machine-gun bullets.

While this was impressive, I'd attribute that more to luck than to anything else. German experience was that the four-engined bombers went down after an average of 25 x 20 mm hits, and they were recognized as a lot tougher than the P-47. I'm sure some four-engined bombers returned safely with a multiple of these average 25 cannon hits, too.

>Johnson repeatedly claimed he could pull 72" of MAP and reported airspeeds of 470 mph TAS.

As the P-47 achieved it's top speed at very high altitude, the compressiblity error of the airspeed indicator was considerable. As this phenomenon doesn't seem to have been included in the typical WW2 fighter pilot training, I consider it likely that the 470 mph figure lacked the compressiblity correction.

Regards,

Henning (HoHun)

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Widewing on November 26, 2003, 12:31:40 AM

Quote

Originally posted by FUNKED1
Are those Johnson's words or Johnson's words as told to/filtered by/revised by Martin Caidin?

Johnson's words, recorded in an interview for Military History magazine, just days before he left for Lawton, Oklahoma where he died on December 27, 1998.

I had several long phone conversations with Bob in the weeks before he left to visit his relatives (in Lawton). I've posted part of those recorded conversations to this board in the past.

A few months before he passed on, Bob's book was re-released having been re-edited by Johnson and having added some material. He sent me a copy. It's still available from Honoribus Press, located in the town where Bob retired, Spartanburg, South Carolina. ISBN 1-885354-050-3. About $17 in softcover.

My regards,

Widewing

Title: Re: Re: Bob Johnson's observation of Luftwaffe fighters
Post by: Widewing on November 26, 2003, 01:19:34 AM

Quote

Originally posted by HoHun
Hi Widewing,

>Also, none of the German fighters were as rugged as a P-47.

I'd say Johnson lacked the basis for a fair comparison as he (hopefully) didn't shoot down enough P-47s to get a good average ;-)

>When I was badly shot up on June 26, 1943, I had twenty-one 20mm cannon shells in that airplane, and more than 200 7.92mm machine-gun bullets.

While this was impressive, I'd attribute that more to luck than to anything else. German experience was that the four-engined bombers went down after an average of 25 x 20 mm hits, and they were recognized as a lot tougher than the P-47. I'm sure some four-engined bombers returned safely with a multiple of these average 25 cannon hits, too.

>Johnson repeatedly claimed he could pull 72" of MAP and reported airspeeds of 470 mph TAS.

As the P-47 achieved it's top speed at very high altitude, the compressiblity error of the airspeed indicator was considerable. As this phenomenon doesn't seem to have been included in the typical WW2 fighter pilot training, I consider it likely that the 470 mph figure lacked the compressiblity correction.

Regards,

Henning (HoHun)

Hiya Henning!

Bob had a few Jugs shot up, he also killed a lot of 190s and 109s. There is little doubt that the P-47 was a very stout aircraft, generally over-engineered as compared to the P-51. Of all allied fighters in the ETO, the P-47 had the best loss per sortie ratio by a considerable margin. And keep in mind that the P-47 spent the last 9 months of the war down in the weeds flying close support ann interdiction where the flak is severe. If you have seen photos of the P-47C Johnson brought home (twenty-one 20mm hits), you realize that this was one rugged fighter. And yes, he was lucky that the hits were not concentrated in one locale. Yet, his tale was common-place.

As to the speed of his P-47; Pratt & Whitney tech reps were largely responsible for giving Gould the secrets of horsepower production in the R-2800. Engines with the same wastegate modifications were tested at P&W and produced in excess of 2,700 hp on the dynometer, and did so for hundreds of hours at full throttle. The later "C" series R-2800 (used in the P-47M and N) generated 3,600 hp during similar endurance testing. It should not be a surprise that a P-47D-5-RE should attain similar speeds to the P-47M with 2,800 hp with slightly greater drag. Gould also filled all gaps in seams and waxed Johnson's Jug to reduce parasite drag.

By the Spring of 1944, there wasn't a P-47 in the 56th that hadn't been field modified like Johnson's. Ask any of the surviving crew chiefs. When 150 octane fuel became available in early '44, 72" MAP became the standard for combat operations. While this setting was never incorporated into the standard issue pilot's manual, it is easily found in 8th AF Fighter Command technical bulletins and operational instructions.

I have a great photo in my collection of a 56th FG P-47 sitting on 9th AF airfield in Belgium. It suffered a turbo failure and the pilot landed at the nearest field. Surrounded by 9th AF Jugs, the 56th fighter stood out. It was waxed and as clean as it was when delivered. Contrasting this were the filthy, beat-up Jugs of the 9th AF.

I believe Johnson's observation was accurate, and it is supported by the others in his squadron at the time (61st FS).

My regards,

Widewing

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: F4i on November 26, 2003, 03:16:17 AM

Dang, Wide...I didn't know that you spoke with these pilots.  I'm searching for your old posts with recorded transcripts from previous conversations.  Now, wherrrrrrre are they?!?  :)

TBolt

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Oldman731 on November 26, 2003, 06:59:30 AM

Thanks for posting this, Widewing.  Didn't know that RSJ had re-done his book, will have to look for it.

- oldman

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: -ammo- on November 26, 2003, 08:38:18 AM

Thx WW

Title: Re: Re: Re: Bob Johnson's observation of Luftwaffe fighters
Post by: HoHun on November 26, 2003, 01:28:48 PM

Hi Widewing,

>There is little doubt that the P-47 was a very stout aircraft

There's little doubt that the Fw 190 was a very stout aircraft either. I don't think shooting at and killing type A while getting shot at and surviving in type B is a valid comparison method.

>Yet, his tale was common-place.

Do you mean that there were more P-47s who returned with 21 x 20 mm hits?

>It should not be a surprise that a P-47D-5-RE should attain similar speeds to the P-47M with 2,800 hp with slightly greater drag.

I'm sure you're aware of the F4U-4 comparison report which has data on a P-47D of a subvariant that has been subject to some discussion on this forum.

From the R-2800-C power graph in that comparison report, it can be estimated that increasing boost from 64" Hg to 72" Hg that might give as much as a 300 HP gain.

At the same time, the ciritical altitude drops. From the P-47D high-speed power chart, the critical altitude for 2900 HP can be estimated as about 26500 ft.

At this altitude, running at 64" Hg boost yielding 2600 HP, the P-47D referenced in this report achieves a speed of 438 mph. Increasing boost to 72" Hg and power to 2900 HP would give us a calculated top speed of 454 mph.

Still very impressive, but far from the 470 mph you mentioned.

(Just how far? Well, the P-47D in question would need no less than 3200 HP to get there. And my calculations actually neglect the transsonic drag rise that at these speeds begins to make itself felt.)

>I believe Johnson's observation was accurate, and it is supported by the others in his squadron at the time (61st FS).

Well, I do actually agree that Johnson's observation was accurate.

While he reported a true air speed of 470 mph, he certainly didn't have a TAS-recording instrument on the dashboard of his P-47. He probably read the air speed indicator to get IAS, applied the position error correction to get CAS, and then used his calculator to transform it into TAS.

I do, however, think Johnson's observation was incomplete.

One important step in determining TAS is converting CAS to EAS, accounting for the compressibility error. As far as I can tell, this was not usually part of the training of WW2 fighter pilots in any air force. Though engineers were well aware of it, pilots generally were not.

470 mph TAS at 26500 ft would result from 267 KCAS with no compressibility correction. However, 267 KCAS are only 258.5 KEAS, so the correct TAS figure is actually 455 mph.

This is so close to the rough estimate of the speed for a P-47D with 72" Hg that I'm surprised myself :-) There's actually a fair margin of error in my estimate so please don't take the exact mph figure as the final word on P-47D performance!

However, I have no doubt that Johnson's belief that his P-47 could actually achieve 470 mph TAS is wrong.

Not by a fault of his own, I hasten to add - I'm convinced his training hadn't provided him with the background on compressibility, which actually was the leading edge of contemporary research. Engineers and test pilots needed to know about it, but for fighter pilots it was largely irrelevant anyway.

Fighter pilots had to know and respect the redline speeds of their aircraft, and all manuals I have seen give these speeds with the compressibility error already figured in so that the pilot wouldn't have to think about the conversion in combat. The Me 262 was actually given an airspeed indicator indicating TAS directly for most of the speed range, and IAS only for low speeds.

That made perfect sense at the time, but it has to be remembered when drawing conclusions from the pilots' accounts.

Regards,

Henning (HoHun)

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: F4i on November 26, 2003, 02:28:37 PM

Is it just me?  Or, does it seem like Wide & HoHun are the same person with a split personality?  :D

Allow me to write you a new Rx...

TBolt

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: gripen on November 26, 2003, 03:28:13 PM

Hm... Well, early B-series R-2800 (21?) and 72" without water injection sounds quite high. Water injection system in the P-47 worked automaticly (IIRC it started to work at given MAP say 54" or something). I have so far seen reference for 66" with grade 100/150 (R-2800-59, early models a lot less) and 70" with water but I have not seen evidence that 8th AF got that fuel before summer -44. Officical rating with water for the B-series was 58" at spring 1944 (grade 100/130).

Philipps shot down has been under discussion on various forums and AFAIK there is no consensus if it was Johnson or Bombers or someone else. At least AFHRA lists no claims for Johnson at March 2, 1944 (Mayer shot down).

gripen

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Widewing on November 26, 2003, 06:58:44 PM

Quote

Originally posted by gripen
Water injection system in the P-47 worked automaticly (IIRC it started to work at given MAP say 54" or something).

Philipps shot down has been under discussion on various forums and AFAIK there is no consensus if it was Johnson or Bombers or someone else. At least AFHRA lists no claims for Johnson at March 2, 1944 (Mayer shot down).

gripen

Prior to the P-47D-11-RE, all P-47s fitted with water injection used a manual switch to turn on the pump. Problem was that in the heat of combat many pilots forgot to flip the switch. Johnson's Jug in this case was a P-47D-5-RE. P-47D-10-RA Jugs received the new G.E. C-21 turbocharger, but still retained manually operated water injection. This changed with the P-47D-11-RE, which had the new turbo and automatic WEP water injection (per Bodie).

Johnson has specifically mentioned the manual water injection switch during several interviews.
 
As to Egon Mayer... You are absolutely correct. I pulled my 56th FG history out and compared facts with a later publication that claimed Johnson nailed Mayer. Not only did Johnson not shoot down Mayer, but he was grounded for a physical ailment for most of the period in question.

In fact, the opposite nearly occured... It was Egon Mayer who stumbled upon Johnson's battered Jug and emptied his guns into it! Mayer, having fired the last of his last ammunition, flew alongside Johnson staring at the Thunderbolt in disbelief. He gave a wave, rocked his wings and headed for home. He apparently claimed Johnson as a kill, certain the wrecked fighter would never reach England.

Anyway, I shot an e-mail off to the author of the piece where he claims Johnson shot down Mayer. His initial response was that his research shows Johnson was the guy. Impossible for Robert Johnson.. Maybe some other Johnson. Either way, he is incorrect because Johnson's next mission was on March 8, not March 2 as he asserts. On March 2, only 6 Luftwaffe fighters were claimed by 8th AF fighters, and all of those appear to have been brought down by P-51s.

In contrast, there seems to be little doubt about Hans Phillipp. Johnson shot down a Bf 110, and then, alone, attacked four Fw 190s. He obliterated the lead 190. Most historians concur that the facts reported by the Luftwaffe pilots flying with Phillipp and Johnson's account are in agreement in detail as well as location and time of day. I believe that historians Raymond Tolliver and Trevor Constable discovered this and verified it as fact.

My regards,

Widewing

Title: Re: Re: Re: Re: Bob Johnson's observation of Luftwaffe fighters
Post by: Widewing on November 26, 2003, 07:08:20 PM

Quote

Originally posted by HoHun
Hi Widewing,

At this altitude, running at 64" Hg boost yielding 2600 HP, the P-47D referenced in this report achieves a speed of 438 mph. Increasing boost to 72" Hg and power to 2900 HP would give us a calculated top speed of 454 mph.

Still very impressive, but far from the 470 mph you mentioned.

(Just how far? Well, the P-47D in question would need no less than 3200 HP to get there. And my calculations actually neglect the transsonic drag rise that at these speeds begins to make itself felt.)

Heya Henning,

Then, how do you account for the P-47M-1-RE and P-47N-1-RE recording CORRECTED speeds of 475 and 467 mph respectively on 2,800 hp? These weren't massaged aircraft but fighters selected at random from the production line for testing.

My regards,

Widewing

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Pongo on November 26, 2003, 07:48:43 PM

Certainly it seems that the Jug pilots tore the experten heart out of the LW in the west.

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Halo on November 26, 2003, 08:12:53 PM

Fascinating info, Widewing, thanks.  I've always been a Jug fan since as a little kid I used to watch them being test flown and their guns zeroed at the massive Evansville, Indiana, factory.

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Widewing on November 26, 2003, 10:53:17 PM

Bob Johnson Interview: Part 1

A few months before Robert Johnson died (December 27th, 1998), I conducted nearly five hours of telephone interviews with Bob over the course of three weeks. I managed to record all but the first hour. During our conversations, we discussed the tactics he employed while battling the Luftwaffe. The following are some excerpts of our discussions.

CCJ: I have read an article about you and the tactics you used, that described you as one of the first fighter pilots to truly fight in the vertical plane.

RSJ: I don't know about that, there were others who fought that way.

CCJ: But not in the Thunderbolt....

RSJ: No, I guess not, at least when we first went operational.

CCJ: Can you describe how you used vertical maneuvering to your advantage, especially in the heavy-weight Jug?

RSJ: I think that you need to understand that everyone thought that the P-47 was a deathtrap. RAF pilots told us that we wouldn't have a chance against single-engine fighters. Those of us who had been flying the P-47 for a while knew otherwise, but there was nothing we could say that would convince the British, or the guys in the 4th.

CCJ: Guys of the 4th? You mean the 4th Fighter Group?

RSJ: Yeah. They were not at all happy trading in their Spitfires for the Thunderbolt.

CCJ: Didn't the 56th surrender their P-47s to the 4th after you arrived?

RSJ: Yes, we were told that we would be getting new planes.

CCJ: I'll bet that struck a nerve in the 56th.

RSJ: It sure did. We already had hundreds of hours in P-47Bs and Cs. No other group of pilots in the ETO had anywhere near our experience in the Thunderbolt. So naturally, we were not happy to hand them over to another Group. In retrospect, it was obviously a good idea. We realized as soon as we got into combat that there was no substitute for actual combat missions under your belt. Anyway, we trained the 4th on the Thunderbolt and then waited for what seemed like forever, to get our new planes.

CCJ: To get back to tactics, how did your tactics evolve?

RSJ: My tactics were rooted in what I had learned flying the P-47 in the States. We could always find some Navy Corsairs over Long Island Sound. We would bounce them, or they would try to bounce us. Usually, we had the advantage in height so the Corsairs were a lot busier than us.

CCJ: I take it that you seldom let an opportunity to jump them go waste?

RSJ: No, we usually went straight for them.

CCJ: Didn't they see you rolling in?

RSJ: Sometimes. We tried to use the sun to hide in. If they didn't spot us, we would lay it on them good. Their first hint that we were there was when we tore through them at high speed and zoomed back up above them.

CCJ: How did they react?

RSJ: They would usually scatter every which way. We would come back down on them again, but they would be alert now and break into us.

CCJ: I guess that is the point where it would break down into a big brawl?

RSJ: It did at first. The Corsair was just a fast as the Thunderbolt was around 20,000 ft., and it was very maneuverable. As we mixed it up and lost altitude, the Corsair became a real handful to outfly with our P-47Bs. I discovered that the Corsair pilots did not like fighting up hill. What I mean is, they would not or could not follow you if you pulled the nose up into a steep climb. I realized that the Corsair couldn't climb any better than the P-47, and would tend to spin out of a vertical stall. I also found that that any P-47, even the P-47B, could out-dive the Corsair. So that gave me two important advantages that I would use every chance I got.

CCJ: So these mock dogfights helped you learn how to exploit the inherent strengths of the Thunderbolt.

RSJ: Yes, very much so.

CCJ: What about facing the Fw 190 and Messerschmitts?

RSJ: The Focke Wulf reminded me of the Corsair. It was much smaller of course, but they both had similar maneuverability. It wasn't quite as fast, but turned well. It was unusual to find Focke Wulfs above us. Generally, we held the advantage in height.
The Me 109 was another story. They could often be seen up above 35,000 feet.

CCJ: What was the biggest mistake a German pilot could make?

RSJ: Trying to escape in a dive or split-S.

CCJ: Why?

RSJ: Because they were not going to out-run the Thunderbolt in a dive.

CCJ: You could catch them without a problem.

RSJ: I could catch them in nothing flat.

CCJ: Really?

RSJ: Absolutely. One thing about the 190, if the pilot continued his dive below 7 or 8 thousand feet, he could not pull out before he hit the ground. I guess they had compressibility problems or the elevators got too stiff. What ever the problem was, I watched several of them pancake in before they could level off.

CCJ: What about the Thunderbolt?

RSJ: It did not have that problem down that low. Up high, above 25,000 feet, yes, I could get into compressibility and the elevators locked up like they were in concrete. But once you got down to thicker air, you regained control.

CCJ: So, what would you do if suddenly discovered a German fighter on your tail?

RSJ: you mean in close?

CCJ: Yes.

RSJ: That depended a lot on how fast the German was going. If he was moving much faster, I'd simply side-step him by rolling.
The German would whiz right on by and I would firewall the throttle and take off after him. If he was a smart German, he would climb straight ahead. If he was a dumb German, he would try to turn. If he turns, his higher speed will make for a wide turn, and I will cut across and be all over him. If he dives, I can follow and eventually catch up. Now, if the German's speed was close to mine, then I had another emergency maneuver that always worked for me.

CCJ: And, that was?

RSJ: I would pull the nose straight up into a vertical rolling spiral, usually to the left. You would stall out, but so would the guy behind you. That killed his advantage.

CCJ: So, what you are describing sound like a rolling hammerhead stall, right?

RSJ: That's a pretty good description.

CCJ: So what happens next?

RSJ: Well, the enemy would stall first because the Jug's mass allowed to retain its,
er...

CCJ: Energy?

RSJ: Yes, energy. The P-47's mass allowed it to retain its energy better and it stalled a few seconds after the enemy plane. The German would snap over and head down. Except, now I was right behind him and there was no getting away.

CCJ: Wouldn't he still be directly behind you?

RSJ: No. Pulling up so suddenly always caught them by surprise. The second or two that it took for them to react took care of that.

CCJ: Why did you roll?

RSJ: Because that killed my speed faster than the enemy if he didn't, which gained me the advantage of being to his rear as he zoomed up. If he rolled too, that also worked to my advantage because it killed his speed faster than mine.

CCJ: So, you would get the advantage no matter what, if the German also pulled up into a vertical climb. What if he didn't follow?

RSJ: Then he would just fly by. If he still wanted to fight, he could extend out and turn around, but I would be waiting for him.
If he turned either left or right, I would be all over him in a few seconds.

CCJ: The smart Germans just kept on going when you pulled up.

RSJ: I never ran across one smart enough to keep going. They all tried to follow.

CCJ: How many got away after falling for your trap?

RSJ: I really can't say for sure. Some got away because he had friends to cover his tail. Besides, that maneuver was not so much to get him, but to prevent him from getting you. In that respect, it always worked.

CCJ: Much has been written about the incredible roll rate of the Fw 190. Was it as good as they say?

RSJ: The 190 rolled very fast. But, so did the Thunderbolt.

CCJ: But not as quickly as the Focke Wulf.

RSJ: I would say just as fast. I never had a 190 out-roll my Jug. Never.

CCJ: What about a situation where you end up in rolling scissors with a Focke Wulf? Do you follow him by reversing the turn too?

RSJ: No. Whenever you get into a series of reverses, the airplane tends to mush-out a bit when you reverse your turn. The Jug tended to mush a bit more than the 190. The way to avoid this was roll into the reverse.

CCJ: I'm not sure I follow you.

RSJ: Picture this in you mind. The 190 rolls into a hard left. You follow, firing as he crosses your guns. Suddenly, he reverses his turn, hard right. Rather than reverse, you continue rolling left until you are in a right bank, just like the 190. Now, pull hard. No mushing. If he reverses again, you roll left and fire as he crosses your guns. If he doesn't reverse, I pull the nose high and roll out behind him.

CCJ: A high yo-yo?

RSJ: Of a sorts, yes. Continuing the roll simply eliminated the mushing caused by reversing a turn and I would get a clear shot every time the enemy reversed.

CCJ: What you define as the most important things a fighter must know to be successful, relating to air combat maneuvering?

RSJ: It's pretty simple, really. Know the absolute limits of your plane's capabilities.
Know its strengths and weaknesses. Know the strengths and weaknesses of you enemy's fighters. Never fight the way your enemy fights best. Always fight the way you fight best. Never be predictable.

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Widewing on November 26, 2003, 10:55:08 PM

The Bob Johnson interview: Part 2


CCJ: I remember reading where you thought that your P-47 was the fastest fighter in the ETO.

RSJ: I still believe that it was.

CCJ: Really?

RSJ: Sure. My second Jug, a D-5 was the best P-47 that ever flew, and I flew them all, including the P-47M which the 56th got near the end of the war.

CCJ: What made this one Thunderbolt so fast?

RSJ: Several things. My crew sanded every joint smooth, and waxed it to a high gloss. Factory technical reps showed my crew chief, Pappy Gould, how to adjust the wastegates to keep the boost pressure higher than normal. My D-5, which I named Lucky, had water injection. I never used the water injection in combat. I didn't need it. From time to time I'd switch it on, push the throttle up to 72" of manifold pressure and the head rest would smack me from behind. I would let her run for a few minutes just for the fun of it.

CCJ: 72 inches!? Did you ever take note of your airspeed during one of those runs?

RSJ: Of course.

CCJ: And....... how fast did it go?

RSJ: I've seen just over 300 at altitude.

CCJ: 300 indicated?

RSJ: Yes.

CCJ: What was your altitude?

RSJ: I guess it was right around 32,000 feet.

CCJ: Geez, that’s well over 450 mph!

RSJ: Oh, I figure closer to 470.

CCJ: Maybe you did have the fastest fighter in the ETO after all.

RSJ: Like I said, Lucky was the fastest.

CCJ: What ever happened to Lucky?

RSJ: She was lost in a mid-air collision over the North Sea. I don't recall the pilot's name who was flying her on that ramrod. I was very upset. Lucky got at least 24 enemy aircraft and was the best Jug I ever flew. She was trouble free and I never had a single abort while flying her.

CCJ: Bob, one final item before I let you go tonight.

RSJ: Sure.

CCJ: Is it true that you flew two 25 hour tour extensions after your 25th victory, and that you never were involved in a single combat during that time?

RSJ: Basically, yes. I took a 25-hour extension with the idea that as soon as I got 2 more enemy aircraft, I would stop there and go home. After the 25 hours were up and I hadn't had a chance to even fire at an enemy airplane, I took another 25 hour extension under the same understanding. Finally, on the last mission of that tour, I got two more and they sent me home.

CCJ: Why do you think that German fighters became so hard to come by at that time. When was that, in April and May of 1944?

RSJ: I can't say for sure, but we now know that the long range of the P-38 and P-51 caused the Luftwaffe to pull back many of their fighter squadrons deep into Germany. This makes sense when you think that we could put up over 600 P-47s for a ramrod. If they pull back beyond the range of the Jugs, we won't see much of them. Another thing was simple bad luck. When the Germans did come up to fight, they attacked the bombers well away from our assigned area. So, it really was a combination of factors.

CCJ: So, what was the date of your last two victories?

RSJ: May 8th, 1944.

CCJ: Well, Bob, I'll let you go now. Thanks for your time. This will make for a terrific article.

RSJ: It was my pleasure.

CCJ: Are you up for another discussion in a week or two?

RSJ: If you don't mind my long stories, sure. You can call almost anytime.

CCJ: Believe me, it's an honor for me. By the way, Art Heiden, you remember me talking about Art, Art wants to talk to you about Jack. Do you mind if I pass your number to him?

RSJ: Please do.

CCJ: Well, thanks again and have a good evening.

RSJ: You to.

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Batz on November 26, 2003, 11:33:59 PM

Quote

In contrast, there seems to be little doubt about Hans Phillipp. Johnson shot down a Bf 110, and then, alone, attacked four Fw 190s. He obliterated the lead 190. Most historians concur that the facts reported by the Luftwaffe pilots flying with Phillipp and Johnson's account are in agreement in detail as well as location and time of day. I believe that historians Raymond Tolliver and Trevor Constable discovered this and verified it as fact.

My regards,

Widewing

There is doudt and Johson's claim doedn't match up with the pilots flying with Philipp. They claim he was shot up and damaged by bombers and was on its way down when they lost sight. They claim the only way a p47 could have claimed a kill is if they chased after him.

In this same engagement Johnson was shot up (rudder cable)and and dove for home.

Quote

apparently Luftwaffe loss records, indicate that Herr Philipp was shot up quite heavily by the American bombers he was attacking. If any P-47 finished him off, it was while his plane was already descending and out of commission. So the German version

His wingman

Quote

On October 8, 1943, the 8th AF dispatched 156 bombers to targets in Bremen and Vegesack. The force was escorted by 250+ Thunderbolts from six different fighter groups.

The Stab Flight of the Geschwader heard Philipp announce a victory over a Thunderbolt. The last tranmission from him was: "Reinhardt, attack!" Feldwebel Reinhardt was Philipp's wingman on this day. He last saw the Kommodore's aircraft disappear in a cloud. Reinhardt was wounded after colliding with an enemy aircraft, but made a successful forced landing. Later that evening, the Geschwader learned that their Kommodore had been shot down and killed.

Johnson may well have shot him down but its not set in stone.

Title: Re: Re: Re: Re: Re: Bob Johnson's observation of Luftwaffe fighters
Post by: HoHun on November 27, 2003, 01:33:00 AM

Hi Widewing,

>Then, how do you account for the P-47M-1-RE and P-47N-1-RE recording CORRECTED speeds of 475 and 467 mph respectively on 2,800 hp?

I haven't seen anything as detailed as the F4U-4 comparison report including the P-47M and -N (and after a quick look, some of my general books don't agree with the top speeds you quoted), so I'm unable to comment these figures.

Regards,

Henning (HoHun)

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: gripen on November 27, 2003, 08:54:48 AM

Here is couple NACA reports for additional info on R-2800. RM E6J08 (http://naca.larc.nasa.gov/reports/1946/naca-rm-e6j08/) is about pre-ignition limits with various fuels (28R is grade 100/130 and 33R is 110/145) and different spark-plugs (no water injection). Report 873 (http://naca.larc.nasa.gov/reports/1947/naca-report-873/) is about cooling of the R-2800 on high altitudes, it explains quite well why the P-47 tend to overheat at high altitude climbs. Overall it seems that 72" MAP might have been possible with right fuel (no water) but just for very short periods because overheating would have been pretty much instant without water injection.

Another interesting piece of data is ETO kill claim part (http://www.maxwell.af.mil/au/afhra/wwwroot/aafsd/aafsd_pdf/t167.pdf) of the USAAF statistical digest. Before January 1944 US fighters did not claim so many kills but after that claims steadily rise. Turning point appears to be the Big Week and after that claims still increased and continued in the same level until September. Basicly early P-47 operations did not affect a lot to Luftwaffe, seems that it was combined pressure on all fronts during summer 1944 which broke back of the Luftwaffe.

gripen

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Batz on November 27, 2003, 09:16:22 AM

Geesh

Total heavy bomber kills in the air 6,098
Total Fighter kills in the air 7,422

April 45

3,703 aircraft killed on the ground...........

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Widewing on November 27, 2003, 11:50:03 AM

Quote

Originally posted by gripen
Here is couple NACA reports for additional info on R-2800. RM E6J08 (http://naca.larc.nasa.gov/reports/1946/naca-rm-e6j08/) is about pre-ignition limits with various fuels (28R is grade 100/130 and 33R is 110/145) and different spark-plugs (no water injection). Report 873 (http://naca.larc.nasa.gov/reports/1947/naca-report-873/) is about cooling of the R-2800 on high altitudes, it explains quite well why the P-47 tend to overheat at high altitude climbs. Overall it seems that 72" MAP might have been possible with right fuel (no water) but just for very short periods because overheating would have been pretty much instant without water injection.

Another interesting piece of data is ETO kill claim part (http://www.maxwell.af.mil/au/afhra/wwwroot/aafsd/aafsd_pdf/t167.pdf) of the USAAF statistical digest. Before January 1944 US fighters did not claim so many kills but after that claims steadily rise. Turning point appears to be the Big Week and after that claims still increased and continued in the same level until September. Basicly early P-47 operations did not affect a lot to Luftwaffe, seems that it was combined pressure on all fronts during summer 1944 which broke back of the Luftwaffe.

gripen

Thanks for the links to the test reports, it is interesting reading. I seriously doubt that NACA abused these engines as severely as did combat pilots. Once engaged, most pilots pushed everything forward and never even glanced at temp gauges until the fight was over. Engine changes were extremely common, pilots came home with all manner of engine damage from burned valves, to melted sparkplug electrodes, to melted piston crowns. It's a wonder more didn't go down over France and Germany. One pilot in the 357th never accumulated more than 20 hours on an engine before he trashed it by overboosting for sustained periods. Finally, the extremely irritated Group C.O. ordered the pilot to assist in all engine changes. Suddenly, his engine (Merlin) ceased to be abused....  ;)

During early to mid 1943, only a handful of Fighter Groups were operating out of Britain. Towards the end of the year, the number of groups skyrocketed. In addition, the Luftwaffe generally ignored fighter sweeps. By early '44, there were enough long-range P-38s and P-51s that their effect began to take a much greater toll on the Luftwaffe. Still, the vast majority of fighters continued to be P-47s until mid 1944 when the P-51 began replacing the P-47s (not just supplementing them) in the 8th AF.

Here's a chart showing which groups flew what and when the deployed. Not that deployment does not mean operational. It usually took anywhere from 2 to 8 weeks before a new unit was declared operational. The yellow lines on the chart indicates the date when the squadron was released as operational.

(http://home.att.net/~ww2aviation/8thAF1.gif)

My regards,

Widewing

Title: Re: Re: Re: Re: Re: Re: Bob Johnson's observation of Luftwaffe fighters
Post by: HoHun on November 27, 2003, 01:14:09 PM

Hi Widewing,

Before we lose sight of it:

>Then, how do you account for the P-47M-1-RE and P-47N-1-RE recording CORRECTED speeds of 475 and 467 mph respectively on 2,800 hp?

Where's you rspeed data from, and where's the evidence compressiblity correction has been applied to it?

Regards

Henning (HoHun)

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: HoHun on November 27, 2003, 01:23:53 PM

Hi Widewing,

>Once engaged, most pilots pushed everything forward and never even glanced at temp gauges until the fight was over.

Even with pushing everything forward, 72" Hg gives you no more than 300 extra HP (you only claimed 200 HP) over 64" Hg.

Starting from 2600 HP, that's around 10% of power gain, which yields around 3% of extra speed.

To get to 470 mph TAS, Johson's P-47 would have had to go at 456 mph TAS at standard power settings. And that below its optimum altitude, so the total top speed must have been even higher.

Where's your evidence for a 460+ mph top speed standard P-47D?

Regards,

Henning (HoHun)

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: HoHun on November 27, 2003, 01:57:55 PM

Hi Widewing,

>Still, the vast majority of fighters continued to be P-47s until mid 1944 when the P-51 began replacing the P-47s (not just supplementing them) in the 8th AF.

The total claims by 8th Air Force fighters amount to 7422.

This is the distribution of the claims over time:

12/1943:   6%
04/1944:  25%
08/1944:  54%
12/1944:  82%
05/1945: 100%

Referring to your chart, 75% of the Luftwaffe fighters claimed by the 8th Air Force were claimed in a period when the P-47 equipped less than 25% of the 8th Air Force's fighter groups.

Only 25% were claimed while the P-47 still equipped the majority of the fighter groups.

Regards,

Henning (HoHun)

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: gripen on November 27, 2003, 04:45:41 PM

Widewing,
Well, I'm quite sure that men at NACA did abuse (http://naca.larc.nasa.gov/reports/1946/naca-rm-e6j08/index.cgi?page0017.gif) R-2800 under tests, just read the report.

About deployment of the P-51 it should be noted that 352nd FG converted partially to P-51 in the beginning of the March and flew operationally, 355th converted fully in March and flew operationally. In addition 363rd FG of the 9th AF flew escort missions with the P-51 in March. In practice there were six FGs flying escort missions with P-51s at March, twice more than operational P-38 groups in ETO at that time and quite close number of P-47 groups.

HoHun,
You should note that 58" rating for the B-series R-2800 is 2300hp with water injection and 64" rating 2535hp with water. The dry rating at given MAP is lower because there is no charge cooling effect of the water injection, amount of this effect is normally couple %.

gripen

Title: Re: Re: Re: Re: Re: Re: Re: Bob Johnson's observation of Luftwaffe fighters
Post by: Widewing on November 27, 2003, 07:48:05 PM

Quote

Originally posted by HoHun
Hi Widewing,

Before we lose sight of it:

>Then, how do you account for the P-47M-1-RE and P-47N-1-RE recording CORRECTED speeds of 475 and 467 mph respectively on 2,800 hp?

Where's you rspeed data from, and where's the evidence compressiblity correction has been applied to it?

Regards

Henning (HoHun)

Please, stop being obtuse.....

Virtually every source extent recognizes the USAAF published test data on the P-47M and P-47N. If you need actual data, see Dean's "America's Hundred thousand", pages 282 and 283.

My regards,

Widewing

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Widewing on November 27, 2003, 08:31:03 PM

Quote

Originally posted by HoHun
Hi Widewing,

>Once engaged, most pilots pushed everything forward and never even glanced at temp gauges until the fight was over.

Even with pushing everything forward, 72" Hg gives you no more than 300 extra HP (you only claimed 200 HP) over 64" Hg.

Starting from 2600 HP, that's around 10% of power gain, which yields around 3% of extra speed.

To get to 470 mph TAS, Johson's P-47 would have had to go at 456 mph TAS at standard power settings. And that below its optimum altitude, so the total top speed must have been even higher.

Where's your evidence for a 460+ mph top speed standard P-47D?

Regards,

Henning (HoHun)

We have an old saying here in America, "says you".

Your calculations tell you that the USAAF's actual test data is incorrect. Pardon me if I giggle.....

Fact: The XP-47J reached 507 mph @ 34,300 feet on 2,800 hp. The same aircraft tested by the USAAF reached only 484 mph, but they admitted that the engine suffered a misfire and loss of turbo efficiency due to an exhaust leak in the collector.

Fact: The USAAF rated the P-47M at 475 mph @ 32,600 feet on 2,800 hp.

Fact: The USAAF rated the P-47N at 467 mph @ 32,400 feet,
450 mph @ 26,000 feet, on 2,800 hp.

Clearly, there's a problem with your calculations if they disagree with empirical test data. Theory is like a smokescreen, it blinds you, yet it lacks any substance.

Someone's full of baloney, and I doubt that it was the USAAF's Experimental Engineering Division. Thanks, but I'll cast my lot with the professionals who actually tested the aircraft, than with some unknown character who has previously shown he has an axe to grind with anything of American origin.

I was wondering, do you actually fly Aces High, or just post on their BBS?

My regards,

Widewing

Title: Re: Re: Re: Re: Re: Re: Re: Re: Bob Johnson's observation of Luftwaffe fighters
Post by: HoHun on November 28, 2003, 02:23:09 AM

Hi Widewing,

>Please, stop being obtuse.....

Please stop being impolite. If you mistake thoroughness for obtuseness, that's your fault only. You were posting speed figures with no altitude given - quite obviously, that's useless for a detailed discussion.

This is your claim:

>>Then, how do you account for the P-47M-1-RE and P-47N-1-RE recording CORRECTED speeds of 475 and 467 mph respectively on 2,800 hp?

I'm quite ready to give you the benefit of doubt, but if you go and use capital letters, then I assume you have something to back up your claim.

>If you need actual data, see Dean's "America's Hundred thousand", pages 282 and 283.

Do you mean this is your source? If it is, does it contain speed and power curves like the F4U-4 comparison?

That would be a useful basis for a thorough discussion of these aircraft. Your single figure quotes are not.

Regards,

Henning (HoHun)

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: bozon on November 28, 2003, 02:43:48 AM

very interesting thread.

thank you widewing.

Bozon

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: HoHun on November 28, 2003, 02:45:37 AM

Hi Widewing,

>Someone's full of baloney, and I doubt that it was the USAAF's Experimental Engineering Division.

Try to concentrate on the question:

>>Where's your evidence for a 460+ mph top speed standard P-47D?

The laws of physics are pretty consistent, and the P-47D tested for the F4U-4 comparison is never going to get anywhere 475 mph for certain.

Either you prove the data for the tested P-47D is in error, or you prove my calculations are in error. Both could easily be possible, but I'm not going to believe it without positive proof.

And if you look at the P-47M and P-47N issue, you'll see that I've done nothing but asking questions. I've not made a single statement regarding their performance.

I'm mildy surprised that this was enough to make you lose your composition and resort to ad hominem statements. I'm not going to comment on your emotions - but please, keep them for yourself.

Regards,

Henning (HoHun)

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: moot on November 28, 2003, 08:10:20 AM

Polished, P47s may or may not have been, but Henning certainly is.

Title: Re: Re: Re: Re: Re: Re: Re: Re: Re: Bob Johnson's observation of Luftwaffe fighters
Post by: Widewing on November 28, 2003, 08:57:20 AM

Quote

Originally posted by HoHun
Hi Widewing,

>Please, stop being obtuse.....

Please stop being impolite. If you mistake thoroughness for obtuseness, that's your fault only. You were posting speed figures with no altitude given - quite obviously, that's useless for a detailed discussion.


I'm not being impolite whatsoever; but don't stand in the road because it's right around the bend.


This is your claim:

>>Then, how do you account for the P-47M-1-RE and P-47N-1-RE recording CORRECTED speeds of 475 and 467 mph respectively on 2,800 hp?

I'm quite ready to give you the benefit of doubt, but if you go and use capital letters, then I assume you have something to back up your claim.

First of all, it's not "my claim", these are established facts.


>If you need actual data, see Dean's "America's Hundred thousand", pages 282 and 283.

Do you mean this is your source? If it is, does it contain speed and power curves like the F4U-4 comparison?

That would be a useful basis for a thorough discussion of these aircraft. Your single figure quotes are not.


What did you think I meant? Yes, Dean provides speed, power and climb curves for many versions of the P-47D, as well as the P-47M and N. The F4U-4 is included. Dean's work is thorough (over 600 pages) and well respected. Invest in a copy.

My regards,

Widewing

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Widewing on November 28, 2003, 09:36:53 AM

Quote

Originally posted by HoHun
Hi Widewing,

>Someone's full of baloney, and I doubt that it was the USAAF's Experimental Engineering Division.

Try to concentrate on the question:

>>Where's your evidence for a 460+ mph top speed standard P-47D?

The laws of physics are pretty consistent, and the P-47D tested for the F4U-4 comparison is never going to get anywhere 475 mph for certain.

Either you prove the data for the tested P-47D is in error, or you prove my calculations are in error. Both could easily be possible, but I'm not going to believe it without positive proof.

And if you look at the P-47M and P-47N issue, you'll see that I've done nothing but asking questions. I've not made a single statement regarding their performance.

I'm mildy surprised that this was enough to make you lose your composition and resort to ad hominem statements. I'm not going to comment on your emotions - but please, keep them for yourself.

Regards,

Henning (HoHun)

Where did I state that a "standard" P-47D was a 460 mph fighter? Answer: Nowhere.

I reported what Johnson said, and what Pappy Gould said with regards to Pratt & Whitney tech reps, who showed Gould how to modify the standard wastegates to provide for higher boost pressure. In my interview (which I assume you didn't bother to read), Johnson stated the following:

---------------------------------------------------------------------------------
CCJ: I remember reading where you thought that your P-47 was the fastest fighter in the ETO.

RSJ: I still believe that it was.

CCJ: Really?

RSJ: Sure. My second Jug, a D-5 was the best P-47 that ever flew, and I flew them all, including the P-47M which the 56th got near the end of the war.

CCJ: What made this one Thunderbolt so fast?

RSJ: Several things. My crew sanded every joint smooth, and waxed it to a high gloss. Factory technical reps showed my crew chief, Pappy Gould, how to adjust the wastegates to keep the boost pressure higher than normal. My D-5, which I named Lucky, had water injection. I never used the water injection in combat. I didn't need it. From time to time I'd switch it on, push the throttle up to 72" of manifold pressure and the head rest would smack me from behind. I would let her run for a few minutes just for the fun of it.

CCJ: 72 inches!? Did you ever take note of your airspeed during one of those runs?

RSJ: Of course.

CCJ: And....... how fast did it go?

RSJ: I've seen just over 300 at altitude.

CCJ: 300 indicated?

RSJ: Yes.

CCJ: What was your altitude?

RSJ: I guess it was right around 32,000 feet.

CCJ: Geez, that’s well over 450 mph!

RSJ: Oh, I figure closer to 470.
----------------------------------------------------------------------------------

Now, if Gould and the P&W rep's handiwork produced the expected 2,700 hp, and based upon the P-47D-5-RE having less drag and weight than the P-47M-1-RE, why should it surprise anyone that its performance should generally mimic that shown on the P-47M speed and climb charts?

Note that Johnson used water injection for the 72 in/Hg power setting.

Finally; we read the comments you post, and reflect upon your posts in the Bf 109 thread and realize that you have a personal agenda. Yet, you tell us you only want to be "thorough". Clearly, you are the one suffering from the permanent "wedgie".

So far I have watched you quote out of context and twist facts, either because you failed to fully read posts, or because you wish to obfuscate the discussion. If you wish to be "thorough", you can begin by actually reading the posts and addressing the points therein, rather than create new ones out of thin air.

By the way, you didn't answer my only question... An easy one too.

Do you fly Aces High?

I'm fairly certain that your answer would be no. That's too bad, because an expert of your caliber could certainly point out any errors in the flight model physics of the P-47 or Bf 109. No doubt, Hitech Creations would hang on your every word. ;)

My regards,

Widewing

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: leitwolf on November 28, 2003, 11:33:48 AM

Were modifications to engine and plane limited to the ETO or is reasonable to believe the Navy also had souped up F4Us and F6Fs ?
How'd they perform?

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Widewing on November 28, 2003, 12:30:40 PM

Quote

Originally posted by leitwolf
Were modifications to engine and plane limited to the ETO or is reasonable to believe the Navy also had souped up F4Us and F6Fs ?
How'd they perform?

It is entirely possible that some mechanics did. However, the opportunity and means was extremely limited. Why? Because modifications on the P-47 were not to the engine itself, but to a system. Unlike mechanically supercharged engines like those on the F6F and F4U, the P-47 employed a turbo-supercharger powered by exhaust gas. There were two parts of this system that could be easily modified to alter performance. These were the wastegates and the turbo regulator. Wastegates were generally modified by shimming or stretching the spring (stretching required a heating stress relieving process or the spring will simply collapse back to its original free length, but actually provide less force at working height). New springs could be easily fabricated using a simple screw lathe and mandrel (if one has the required spring wire on hand). Turbo regulators could rigged to allow for greater turbo RPM, or could be internally modified by changes to the spring, poppet or even orifice diameter (not just at the valve seat). At speeds above 18,250 RPM, a warning light would illuminate in the cockpit. This could be overridden by the machanic, or the switch could be adjusted for a higher velocity (not easy to do). The G.E. C-21 turbo could withstand rotational speeds about 50% higher than normal operation, but bearing wear was greatly magnified if higher speeds were sustained. Major turbo failures could severely damage the aircraft, and posed a significant fire risk (leaking oil on a hot manifold or hot exhaust gas leaks). So, I'm sure pilots were cautioned about the potential and inevitable engine and turbo damage resulting from maintaining high boost pressures for extended periods. These modifcations were done to provide the pilots with the absolute maximum power for emergency situations, not for general use, and that is an important point that needs to be emphasized.

There were some things an F6F or F4U mechanic could tweek to add a bit more power. Things like prop indexing and magneto timing changes were feasible. However, these changes could have serious negative effects, especially retarding the ignition too far. Also, unlike the USAAF, the Navy did not blend its fuel at airfields. It was supplied already blended by the manufacturer. Once onboard tankers, and even once aboard and in the carrier's fuel bunkers, there was little anyone could do with the fuel beyond running basic quality and contamination testing. Any local fuel depot within the 8th AF could custom blend fuels to achieve higher anti-knock properties. This is evidenced by Doolittle's order specifying custom blends for the P-38s. He ordered the fuel service depot supplying Kingscliffe to increase the minimum octane rating to 110, and even specified the additives (Doolittle was part of the team at Shell that developed 100 octane aviation fuel in the 1930s). I actually have a copy of that order.

The best way for mechanics to improve the performance of the F6F and F4U was simply maintaining the highest possible state of engine tune, waxing the aircraft and sanding/filling joints in the skin. Removable panels must fit as precisely as possible. For example, badly fitting wing fillets on the P-38 could cause a loss of speed as much as 12 mph and generate vortices that would buffet the elevator (ref. Bodie). So fit and finish were important to obtaining the maximum possible speed.

My regards,

Widewing

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: HoHun on November 28, 2003, 01:30:50 PM

Hi Widewing,

>Where did I state that a "standard" P-47D was a 460 mph fighter? Answer: Nowhere.

As I pointed out above, to get a standard P-47D up to 470 mph by a power increase from 2600 HP to 2900 HP, you need to start with a standard P-47D that makes 460 mph at optimum altitude.

Here is the data:

Critical altitude at 64" Hg: 27700 ft.
Critical altitude 72" Hg: 26500 ft.
Power at 26500 ft, 64" Hg: 2600 HP
Power at 26500 ft, 72" Hg: 2900 HP
Speed of a standard P-47D @ 2600 HP @ 26500 ft: 438 mph
Speed of a standard P-47D @ 2600 HP @ 27700 ft: 441 mph

Here's the result of my calculation:

Speed of a standard P-47D @ 2600 HP @ 26500 ft: 454 mph

If you don't like the result, you either have an issue with the data of the F4U-4 comparison report, or you have an issue with my math. You shouldn't have an issue with my personality, though, as it has no impact on the results at all :-)

I assume you can verify the data. If you need more details on the reference P-47 (or the full report), just drop me a line and I'll help.

If you can't do the math yourself, there are a lot of people on this forum who could help you. Just ask a friendly question on the board, and you can let the community check my simple calculation.

For example, you could ask Badboy, who's a real expert - hey, you could even ask Hitech himself. If you're on friendly terms with Francis Dean, send him the data and ask for his estimate - I'm confident he would come up with a result very similar to my own.

Just to make sure you don't misunderstand the implications a second time: If there was no standard P-47D doing 460 mph, there was no way that going from 2600 HP to 2900 HP would produce a 470 mph P-47D.

I hope you recognize now that my question regarding the 460 mph standard P-47D was well in context.

If you don't have data on such a P-47D, any data would help our analysis, for example by illustrating the possible variations between different Jugs.

I appreciate that you think me worthy of being flamed, but I'm a bit disappointed that you do so before we've really dug into the data ;-)

>By the way, you didn't answer my only question... An easy one too.

I purposefully left it unanswered because I fail to see what me flying Aces High or not has to do with the top speed of the P-47.

However, I never made it a secret that I don't fly Aces High. I'm tempted to say "yet", though, as I follow its development with great interest and consider it the most promising online fight simulator currently available to the public.

>That's too bad, because an expert of your caliber could certainly point out any errors in the flight model physics of the P-47 or Bf 109. No doubt, Hitech Creations would hang on your every word. ;)

In the discussions on this forum, Hitech has occasionally commented on my posts. If you'd care to look up these comments, you'd find that Hitech has usually given me very thoughtful answers that prove that he really knows his stuff.

I don't think Hitech have written such nice answers if he'd have thought me to be a lunatic Luftwaffe fanatic :-)

Regards,

Henning (HoHun)

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Widewing on November 28, 2003, 04:54:05 PM

Quote

Originally posted by HoHun
Hi Widewing,

>Where did I state that a "standard" P-47D was a 460 mph fighter? Answer: Nowhere.

As I pointed out above, to get a standard P-47D up to 470 mph by a power increase from 2600 HP to 2900 HP, you need to start with a standard P-47D that makes 460 mph at optimum altitude.

Here is the data:

Critical altitude at 64" Hg: 27700 ft.
Critical altitude 72" Hg: 26500 ft.
Power at 26500 ft, 64" Hg: 2600 HP
Power at 26500 ft, 72" Hg: 2900 HP
Speed of a standard P-47D @ 2600 HP @ 26500 ft: 438 mph
Speed of a standard P-47D @ 2600 HP @ 27700 ft: 441 mph

Here's the result of my calculation:

Speed of a standard P-47D @ 2600 HP @ 26500 ft: 454 mph


Let's stick to Johnson's Jug.

P-47D-5-RE, R-2800-21

Power at 25,000 ft, 52" Hg: 2,000 hp
Power at 27,000 ft, 64" Hg: 2,300 hp

Those are the baseline numbers for Johnson's Thunderbolt as delivered per P&W data sheet for the -21 engine (ref. Bodie collection).

Gould was told by P&W that 72" Hg would generate 2,700 hp.

Baseline speed for the P-47D-5-RE was 433 mph @ 27,000 ft. on 2,300 hp.

Base your calculations on these numbers.

Either way, the fact that the P-47M attained 475 mph on 2,800 hp at 32,600 ft is a major stumbling block opposing your assertion that a P-47D-5-RE would require 2,900 to reach 470 mph when it has less drag and weighs 800 lbs less.

In the meantime, why don't you download the software, it's free. Then set up an account, the first two weeks are also free. This way, if we become annoyed with each other, there's some minimal recourse for revenge! LOLOLOLOL

No, that wouldn't be fair, I've been doing this a while. But, I would be willing to show you the "ropes" so to speak, to help shorten the learning curve (which is remarkably steep).

My regards,

Widewing

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: HoHun on November 28, 2003, 06:28:16 PM

Hi Widewing,

>P-47D-5-RE, R-2800-21

>Power at 25,000 ft, 52" Hg: 2,000 hp
>Power at 27,000 ft, 64" Hg: 2,300 hp

>Gould was told by P&W that 72" Hg would generate 2,700 hp.

>Baseline speed for the P-47D-5-RE was 433 mph @ 27,000 ft. on 2,300 hp.

OK, one additional assumption is that critical altitude for 74" Hg drops by 1200 ft compared to 64" Hg just as suggested by the F4U-4 comparison documents.

In this case, the calculated speed at 25800 ft/2700 HP would be 450 mph.

This is based on a 5 mph drop in speed at 2300 HP that I calculated for the increased density at the lower altitude.

If the drop is only 3 mph as indicated by the F4U-4 comparison, the final speed at 2700 HP would be 454 mph.

Despite its lower 64" Hg top speed, "Bodie's" P-47D is more efficient aerodynamically as it has 300  HP less available and yet reaches a top speed that's only slightly lower though it has a lower critical altitude, too. If you virtually put the "F4U report" engine into the "Bodie" P-47D airframe, you arrive at a calculated 462 mph airspeed at 2900 HP/26000 ft, which is a considerable improvement over both individual reports. If we suppose both are accurate, that might actually be realistic!

>Either way, the fact that the P-47M attained 475 mph on 2,800 hp at 32,600 ft is a major stumbling block opposing your assertion that a P-47D-5-RE would require 2,900 to reach 470 mph when it has less drag and weighs 800 lbs less.

In fact, it would be a quite interesting comparison and a good "sanity check" - if I had any data for a P-47M and N.

>But, I would be willing to show you the "ropes" so to speak, to help shorten the learning curve (which is remarkably steep).

Now that's a nice offer :-) I'm patiently waiting for Aces High 2 in the hope that the learning curve will get even steeper ;-)

Regards,

Henning (HoHun)

Title: Bob Johnson's observation of Luftwaffe fighters
Post by: Nilsen on November 29, 2003, 04:04:14 PM

Great post widewing, thx :)