Jack vs. Tojo - Which was better? Why?

[michael rauls]

The super high performance quoted for late war US planes like P-47N and P-51H are using 80-90" of boost! I am not sure if 80-90" boost would be used by the fighter planes flying 850 mile over water from Iwo Jima to Japan. Using safer (rated) levels of boost the performance is still great, but is then almost the same as J2M using their own high boost over their own land.

FLIGHT TESTS OF THE P-47N AIRPLANE AAF NO. 44-88406
Speed at Military Power (53inch boost)
423mph at 38,000ft.
372mph at 15,000 ft.

P-47N sustained rate of climb is only around 1560-1740ft/min below 25,000ft at Military Power!

Yes but the Thunderbolt can still pull the better numbers out of a hat when/ if it really needs them using the higher boost for a short period I would think.
Also an advantage the p47 has over most other planes including the Jack is it's superior high altitude performance which if utilized properly would translate into either they come up to where the p47 has the much superior performance or they stay in a position where the Thunderbolt has the altitude/ energy advantage on them.
Kind of a loose/ loose for the Jm2. Not saying it's a hands down, walk away one sided contest but that would seem to give the p47 a distinct hard to counter edge over the Jack( and most planes) that doesn't show up in raw performance stats.

 

[taly01]

and if the choice is between over boosting your engine and getting the other guy before he gets you, versus babying your engine and becoming a guest of the Emperor (or worse)

The (or worse) could be ditching part way back to Iwo Jima and hoping you get found before sharks get to you!

P-47 Thunderbolt's best escape tactic is basically a power dive...... interestingly Akamatsu who is probably the most successful Raiden pilot also usually used an escape dive after a firing pass.

Also one translation of the Japanese name Raiden is Thunderbolt!

 

[XBe02Drvr]

The (or worse) could be ditching part way back to Iwo Jima and hoping you get found before sharks get to you!

Most fighter pilots would accept that risk in preference to being shot down over the target area. I know I would. There's a reason for the slogan, "faith in God and Pratt and Whitney".
Cheers,
Wes

 

[Shortround6]

US had some subs and a number of PBYs assigned to pilot recovery. Certainly not a guarantee of safety but offered a chance.

 

[michael rauls]

I wish I could be more specific but here goes, I read an article on the internet( so take with salt grain, maybe 2) a while back that they did a test in a p47 in early 44 to see how long the engine could be run at verry high boost( wish I could remember the exact numbers but just remember it was far in excess of normal), basically after an hour of this is was still running and undamaged much to everyones suprise.
I guess that Pratt and Whitney was one tough motor.

 

[BiffF15]

The (or worse) could be ditching part way back to Iwo Jima and hoping you get found before sharks get to you!

It's the enemy you know (the guy in the other plane who is winning) versus the enemy you don't know (engine longevity after pushing it). The former is a guaranteed to put you into a bad place while the latter is not.

Wes is correct .

Cheers,
Biff

 

[Greg Boeser]

James Muri reported running his R-2800-5s at 70" and 2650 rpm for over a half hour to clear the Kido Butai after attacking the Akagi at Midway. And these were the early A- series engines.

 

[alejandro_]

T.A.I.C. Tojo 2 report 155A dated March 1945. Revised from the December 1944
report.
( T.A.I.C. Jack 11 report 105A dated December 1944 )

Thanks for that information Corsning. Do you have data for the Tojo 1 as well?

 

[taly01]

I'm not saying the Raiden will outperform the P-47N even if its only at 52", but data sheet racing isn't combat proof, and its interesting that the USAAF P-47N tests on www.wwiiaircraftperformance.org are only at a WEP of 53", and they added this.........

FLIGHT TESTS OF THE P-47N AIRPLANE
AAF NO. 44-88406 ............
...........At high power settings considerable maintenance was involved because of oil leaks, cracked vacuum pump housings, exhaust collector rings burning out and oil leaks. At war emergency power these malfunctions become excessive and operation was restricted at this power. In military power climbs high oil and cylinder head temperature above 30,000 ft. were experienced and made it necessary to reduce power after ten minutes of operation to cool the engine.

There is a already a thread about it on here Overboosting the P-47's engines: need some clarifications

 

[CORSNING]

72"Hg was war emergency for these aircraft engines. 54.3"Hg was military.

 

[CORSNING]

Thanks for that information Corsning. Do you have data for the Tojo 1 as well?

Sorry Sir, I do not have a TAIC report on the Ki-44-I.
Your thank you is appreciated. You are quite welcome sir.

 

[Zipper730]

J2M3 m21 vs. P-47N.
The following quote is from page 53 of Erik Pilawskii's 'Fighter Aircraft
Performance of WW2'.
" The J2M3 was remarkable for its tremendous flying horsepower, possessing
what was likely the most formidable power loading of any aircraft in the Pacific
war. Meanwhile, the P-47N model was a longer ranged development of the
P-47D, complete with larger wings and increased tankage. Against the 'Jack',
the Thunderbolt would have to rely on its modest speed advantage*, being
inferior to the J2M in every other performance characteristic. With equal pilots
at the controls this would not have been enough, and it is hard to see past a
victory for the J2M3 under normal circumstances."

The normal power loading for the Model 21 was about 3.65 lb./hp. which was
very good compared to the '47N's 5.64 lb./hp.

P-47N (J2M3 with 92 octane and smooth running engine.)
432 (402) mph/6,000 m.
444 (397) mph/7,000 m.
456 (388) mph/8,000 m.
463 (377) mph/9,000 m.
467 (363) mph/10,000 m.

Looking at these figures, it seems as if the top speed was based around the 72" overboost?

 

[PAT303]

First ever post, I remember reading somewhere that if high boost and water injection is used the engines require a strip down?.

 

[Shortround6]

First ever post, I remember reading somewhere that if high boost and water injection is used the engines require a strip down?.

that may have varied (considerably?) with time. By 1946/47 water injection was being used routinely for take-off on transport aircraft. 2400hp/ 2800rpm/56.0in(+13lbs) on the Commercial C series engines.
In 1943 the engines may certainly have required much often spark plug changes and oil inspections than engines not using water injection and high boost. Actual strip downs/overhauls might have been deemed necessary depending on the hours already on the engine and any metal particles found in the oil?

 

[taly01]

The power vs height graph is great and it shows what they were mentioning in the other thread that 72"+ boost cannot be made > 20,000ft as the turbo/supercharger cannot generate that pressure at thin air altitudes.

I remember reading somewhere that if high boost and water injection is used the engines require a strip down?.

On the P-40 at least to get WEP you had to push the throttle through a wired stop gate, and when you got back the mechanics would curse you behind your back for making them do an engine pull down! I guess the P-47N had some similar system so mechanics would know you went to War Emergency Power.

 

[Shortround6]

I don't believe that EVERY use of WEP required an "engine pull down". It might depend on what is meant by an "engine pull down".

To get a WEP rating an American engine (other countries had different requirements) had to accumulate 7 1/2 hours running time on a test engine at that power rating without breaking anything (or only a few minor problems/accelerated wear). This could be done in 5 minute intervals with cooling off periods in between or all at once or some combination.

It was up to the squadron engineering officer most of the time to both monitor the engines and implement suggested maintenance procedures.
Some types of engines required more frequent spark plug changes (perhaps as often as 20 hours) if WEP settings were used. No mechanic is going to thank the pilot for for making him/them change 18-48 plugs (48 plugs on a P-38) but that is not quite an "engine pull down".
Again, this could change with local conditions. If you were in some god forsaken airfield with poor supplies they may have already been reusing plugs (pulling them, cleaning and replacing) and the engineering officer may have decided that every use of WEP required pulling the plugs until they got new ones?

Depending on when water injection was used it might have contaminated the oil (or they were afraid it would) which might require draining what oil was left and replacing it. If water was used on take-off for a multi hour flight the water/alcohol would have evaporated out of the oil by the time the plane landed.
Oil samples might be pulled for examination/analysis for metal particles (sign of bearing failure.)

If an engine was supposed to be good for 240 hours (number out of hat) before overhaul then every 5 minute use of WEP might shorten that time by one or more hours, depends on the engine in question and the experience of the engineering officers in that theater and the recommendations from the manufacturer.

What procedures were on an Allison in the fall of 1942 and what the procedures were on an R-2800 in the spring of 1945 might be very different.

I will note that Allison, P & W and RR Merlins all gained in overhaul life during the war while operating at increased powers. A discreet curtain will be drawn over the Wright R-3350 however

 

[Capt. Vick]

Jack...based on looks alone

 

[Ivan1GFP]

J2M3 m21 vs. P-47N.
The following quote is from page 53 of Erik Pilawskii's 'Fighter Aircraft
Performance of WW2'.
" The J2M3 was remarkable for its tremendous flying horsepower, possessing
what was likely the most formidable power loading of any aircraft in the Pacific
war. Meanwhile, the P-47N model was a longer ranged development of the
P-47D, complete with larger wings and increased tankage. Against the 'Jack',
the Thunderbolt would have to rely on its modest speed advantage*, being
inferior to the J2M in every other performance characteristic. With equal pilots
at the controls this would not have been enough, and it is hard to see past a
victory for the J2M3 under normal circumstances."

The normal power loading for the Model 21 was about 3.65 lb./hp. which was
very good compared to the '47N's 5.64 lb./hp.

P-47N (J2M3 with 92 octane and smooth running engine.)
432 (402) mph/6,000 m.
444 (397) mph/7,000 m.
456 (388) mph/8,000 m.
463 (377) mph/9,000 m.
467 (363) mph/10,000 m.

*Modest speed advantage?

Hello Corsning et al.
Part of the problem with this comparison of maximum level speeds is that it leaves out the detail about how long it takes for each aircraft to get up to speed.

The P-47M with the same engine as the N model was used in small quantities in Europe.
One of them, "Wonderful Winnie" was used by its pilot to race against unsuspecting Mustangs for money and won those races. The accounts of those races were that on the start of the race, the Mustangs would build up a pretty good lead because of the rather slow acceleration of the P-47M.
Eventually the Thunderbolt would overtake the Mustangs, but it took a while to even catch them.

Consider that the P-47N is heavier than the P-47M and also a couple MPH slower.
The speed advantage is also mostly at very high altitude where the J2M probably would not be.
The J2M as mentioned has a particularly high power to weight ratio and probably a very good acceleration as a result and that may lessen the apparent speed difference.

- Ivan.

 

[Shortround6]

Since the Jack was newer by several years (at least in combat form) and used an engine that was about 20% more powerful the Mitsubishi company would have had to really screw up not to build a better combat plane.
However if you are trying to decide which was the better plane in late 1942, all of 1943 and most of 1944 then the Tojo wins

 

[XBe02Drvr]

However if you are trying to decide which was the better plane in late 1942, all of 1943 and most of 1944 then the Tojo wins

You can't win the fight if you don't make it to the ring by show time!