P-47 Hot Rods in England

[Conslaw]

I was turning over my house recently looking for an old newsletter that I received from the P-47 Advocates group. It must have been about 10 years ago. The article I was looking for was about semi-sanctioned efforts in England to "soup up" or "hot rod" the P-47. These efforts would have either preceded or happened simultaneously with the development of the P-47M. If you have the article please cite from it liberally, as it is apparently out of print and off the web. If you have any other information on the topic, please post.

 

[Cave Tonitrum]

I have heard numerous accounts from people who claim to have knowledge about out of spec hot rodding in the field. (An "I know someone who's dad said 'X'" situation.) I've never read anything from someone with firsthand knowledge though. Given the performance limitations of the earlier P-47's (sans paddle blade) with respect to climb, one could see how there might be an interest in performance enhancing modifications. But out of spec alterations run the risk of affecting reliability which is one the the things pilots liked most about the P-47. That even if the going got tough, it would bring you home.

Late model "D's," after the switch to the new fuel and being cleared for 2,600hp, had a climb at sea level of over 3,200fpm and a top speed of 440mph. With it's great roll rate, dive and zoom climb capability, it wasn't such a bad mount.

 

[CORSNING]

I read an article (probably from a post on this sight) about a P-47D pilot that had a favorite A/C. He stated that it was capable of 470 mph (P-47M terratory). I am sorry I can't remember the thread or the pilots name.

Hey out there, you other guys are really good. I'm sure someone out there has the answere to that one.

Jeff

 

[pinsog]

I read an article (probably from a post on this sight) about a P-47D pilot that had a favorite A/C. He stated that it was capable of 470 mph (P-47M terratory). I am sorry I can't remember the thread or the pilots name.

Hey out there, you other guys are really good. I'm sure someone out there has the answere to that one.

Jeff

I'm pretty sure it was Robert Johnson that siad that. I believe he claimed to have the fastest prop plane in all of Europe didn't he?

 

[Conslaw]

Wwiiaircraftperformance.org has a number of pages concerning the adoption of 150 octane (1944-1) fuel. 150 Grade Fuel

In the 8th Air Force, a directive was issued in June 1944 allowing for the use of 1944.1 fuel in P-51B, P-38J and P-47D aircraft as long as those aircraft had some simple modifications to use the higher octane fuel. The first P-47s were limited to 52 inches of mercury manifold pressure. With water injection and 100/130 fuel, it was 65 inches. It seems that the fastest P-47s on 65" was in the 44x range. If they got another 15 MPH out of a change in manifold pressure to 75 inches, that would give them a top speed over 460. It's not outrageous to think that with diligent waxing and sealing of openings that 470 would have been possible on a B-engined Thunderbolt.

 

[FLYBOYJ]

I'd like to know more about these "semi-sanctioned" tweaks that were done on P-47s. For years I've heard stories about crew chiefs "souping up" their pilot's aircraft, keep in mind that as a maintainer then and now, there's a limited about of things you can do legally to an aircraft to enhance performance. I've heard of waxing and limited use of body filler, but both process are time consuming and if there's a big push to support an operation, I don't see any Tech Sgts wasting the time and energy, especially if they and their "troops" are assigned to 3 or 4 aircraft, which from what I understand was very common during the mid/ late 1944 period in the ETO.
Now, mentioned Robert Johnson, here's a quote from him concerning his crew chief Pappy Gould

"R.Johnson--Sure. My second Jug, a D-5 was the best P-47 that I 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."

Notice how the "tweaks" came at the direction of factory reps (and probably had a squadron maintenance officer's approval).
P-47 engine performance was discussed in this earlier thread;

http://www.ww2aircraft.net/forum/av...s-engines-need-some-clarifications-34328.html

 

[Mike Williams]

P-47 Hot Rods in England...

Fwiw:

P-47D Airplane Performance Tests at 70 In. Hg. Manifold Pressure, 17 June 1944
The results of these tests indicated a ten mile per hour increase in level speed flight to the critical altitude over and above operation at 65 In. Hg. manifold pressure with water injection. ... True air speed at 21,500 feet with 70 In. Hg. manifold pressure and water injection was 445 miles per hour.

P-47D Airplane Tests at 70 In. Hg. Manifold Pressure, 24 June 1944
The P-47D airplane has been released for 70 In. Hg. MAP using 100/150 fuel with water injection (No. 13 water jet).

Teletype Message July 9, 1944: Fuel 100/150
P-47s operating in the UK at the following power settings: 62" Hg without water and 67" HG with water.

Grade 150 Aviation Fuel, 11 July, 1944
War Emergency Manifold Pressures established by the 8th Air Force:
P-47 without water Old W.E.R. - 52"; New W.E.R. - 62"
P-47 with water: Old W.E.R. - 57"; New W.E.R. - 67"

FLIGHT TESTS ON THE REPUBLIC P-47D AIRPLANE, AAF NO. 42-26167 USING 44-1 FUEL, 15 July 1944

VII Conclusions

A. The R-2800-63 can be operated at 65.0" Hg., 2700 RPM, in level flight and climb without water injection when using 44-1 fuel. It can be operated at 70.0" Hg., 2700 RPM with water injection with 44-1 fuel. Climbs at high power must be limited because of high cylinder head temperatures and carburetor air temperatures. Short climbs can be made without difficulty.

B. A gain of 19 MPH can be realized by using 65.0" Hg., 2700 RPM over 56" Hg., 2700 RPM. 8 MPH can be gained at 65.0" Hg. by using water injection. With water injection at 70.0" Hg., 2700 RPM, 7 MPH can be gained over 65.0" Hg., 2700, water injection.

C. In climb operation a gain of 510 ft/min. by using 65.0" Hg., 2700 RPM over 56.0" Hg., 2700 RPM can be realized. 410 ft/min can be gained at 65.0" Hg., 2700 RPM using wate injection. No 70.0" Hg. climbs were made.

 

[Conslaw]

Flyboy - This is the type of information that I remember from the P-47 journal. They talked about the factory reps assisting them with higher boost and other mods.

 

[varsity07840]

I was a flight engineer on a CH-47C Chinook helicopter in Viet Nam. We flew with lower powered T55-L7C engines rather than the troublesome L11s originally fitted. Normal output was supposed to be around 95% of book rating. If you had a friend who was an engine specialist, he'd tweek them up to around 105%. We always left it to the engine guys to play with them. It made a difference in the hot climate and at higher altitudes.

Duane

 

[Mike Williams]

A good case can be made that by 1944 P-47's were already hot ships "as is" with official improvements modifications, without having to resort to unauthorized "souping up" or "hot rodding". During the first half of 1944 a standard P-47D operating at 56" Hg. manifold pressure with water injection was certainly a strong performer relative to the enemy aircraft it faced in the ETO - see: Results of Flight Tests of P-47D-10 using water injection and 56" Hg. MAP (2300 HP)

Service trials in early 1944 planned increasing WER from 56" to 64" (Water Injection on P-47D Airplanes, 3 February 1944). War Emergency Power Kits enabling 2600 Hp. were en route to the UK by February 1944 (War Emergency Power Kits for P-47's, 5 February 1944).

That said, was operating 60" Hg. manifold pressure such as noted in the following report "approved" by the 8th AF at that time or made possible by a local field mod?
Encounter Report of Capt. James R. Carter, 56th FG, 30 January 1944: "I gave full power using water injection and drew 60 inches from 20,000 down to 4,000, finally catching up to the last FW 190."

I'm not sure if this instance of using 65" Hg. manifold pressure was a result of the new WER power kits or some unauthorized modifications made at the local level: Combat Report of 1st Lt. Harry C. Roff, 78th FG, 10 February 1944: "They started a spiraling climb and, even with my ship drawing 65 inches, I could not close to less than 400 yards."

By Spring 1944 "Equipment has been perfected by which a War Emergency Rating of 2535 HP at 2700 RPM at 64" Hg. manifold pressure may be realized from the R-2800 engines now used in production P-47 airplanes." (Improved High Power Equipment for P-47 Aircraft. 17 May 1944).

As previously noted, during the second half of 1944 the 8th AF was using 150 grade fuel enabling 67" - 70" Hg. manifold pressure.

By 1945 there was this "hot rod" on operations:

There may well have been some tweaking by ground crews to get the most of their pilot's aircraft, but the P-47's as supplied and officially modified were more than capable of dealing with the enemy; just read the Encounter Reports.

 

[FLYBOYJ]

My point folks, if you're a maintainer and you're doing something to gain extra performance outside the normal maintenance manuals, unless sanctioned by an engineering officer or factory rep (probably with an engineering officer's concurrence) you're setting yourself up for a heap of trouble, be it during WW2 or today.
I think the only reason why Pappy Gunn got away with doing some of his mods was because he convinced NA field reps that his mods were sound and he had the blessing of a Major General (George Kenny)

 

[fastmongrel]

With all due respect to Johnson (27 kills in 89 combats deserves respect) how did he know his plane could do 470mph. I doubt a combat plane had a carefully calibrated speedo/pitot tube/altimeter and no one was going to bother setting up a measured mile. It was obviously a hot bird but without proper testing all that can be said is it was faster than a standard bird. If his instruments are only say about 2% out that means it could be doing 460 or 480.

 

[Milosh]

Was Gunn involved in any other airplane modifications other than the hmgs in the nose of the A-20s and B-25s and helping the factory install the 75mm in the nose of the B-25?

 

[FLYBOYJ]

AFAIK those were the only mods he did.

 

[GregP]

One of the guys I used to work with at Motorola was in Pappy Gunn's crew. His name was Paul Cherry. He worked on another project, but we used to occasioanlly eat lunch with him and ask about the war.

He said the first 75 mm cannon they installed in the field had no recoil absorption and it egg-shaped some of the rivet holes in the wings after less than 20 shots. They scrapped the plane since the wings would flop around due to the elongated rivet holes! So ... they began installing recoil absorption mechanisms. As I recall, he said their first "homemade" recoil mechanism cannibalized the shock absorbers from 2 Jeeps! Soon after, they began receiving factory planes with the 75 mm cannons and factory recoil absorbers, and didn't have to continue trying to make them in the field. However, theirs worked quite well.

 

[tyrodtom]

The French 75mm cannon that the US adopted had a well developed air over hydraulic recoil buffer well before WW1, it was so effective it was a French state secret for years prior to WW1. It was why the gun could be fired so fast, it didn't have to be re-aimed between shots.
That recoil system may not have soaked up all the recoil up to aircraft structural requirements. I can't imagine anyone trying to solid mount a 75mm, because even a 20mm needs some compliance.
After all, you don't even solid mount a 75mm in a tank, what would ever make anyone think you could do it in a aircraft.

 

[GregP]

Hey, these guys wsere mostly farmers and shade tree mechanics when they were kids and went to war. They did a "field modification" to see if it would work ... they never contemplated production. The second one HAD the recoil absorption and most of the rest were from North American Aviation and were well tested before being deployed.

 

[tyrodtom]

From the pictures I've seen they didn't solid mount the cannon, the recoil mechanism is a part of the barrel, it can't be separated from it.
But the whole gun , gun carriage, trail, wheels and all is around 3500-3600 lbs., barrel with recoil mechanism is a fraction of that. WAG, 1/2 -1/3 of the total weight.
Without all the weight of the whole system, you'd probably have left over recoil energy.

 

[GregP]

I wasn't there and don't know for sure, but Paul Cherry said the first one didn't have a recoil mechanism and they had to scrap the "war weary" B-25 they used as a Guinea Pig.

Might be a "war story" or might be true, I couldn't say, but old Paul wasn't much given to telling lies in regular life or even to rambling long conversations. He mostly kept to himself and did electronic work. Might be as you say, or they might have used a different make 75, I don't know and won't speculate. In any case, the vast majority of the 75 mm cannon-armed B-25's came from North American and DID have recoil absorption.

 

[tyrodtom]

I grew up around WW2 veterans, my Dad, uncles, teachers, my friends fathers.
Even when I was a kid I realized I was listening to impressions, not 100% fact.