How was the Japanese evaluation of the P-40?

[Shortround6]

"They give a 400 mph top speed to the P-39, while the P-40 only has 327. This is strange. Are those estimates?"


They may be from published reports or even advertising. The P-39 had been widely touted as a 400mph aircraft.

in fact even today it is one of the great myths as seen by the Wiki entry:

"The XP-39 made its maiden flight on 6 April 1938.[1] at Wright Field, Ohio, achieving 390 mph (630 km/h) at 20,000 ft (6,100 m), reaching this altitude in only five minutes.[15] However, the XP-39 was found to be short on performance at altitude. Flight testing had found its top speed at 20,000 feet to be lower than the 400 mph claimed in the original proposal."

First there is a typo, first flight was 6 April 1939.
2nd the idea that any aircraft does a maximum climb to 20,000ft and does a max speed run on it's first flight or even first day of flying is ludicrous to begin with.
3rd the first flight was only 20 minutes.
4th the XP-39 was transferred from Wright Field to Langley in June of 1939 (and arrangements made before that so something wasn't quite right).
5th the XP-39 had been plagued with over heating problems in ground running and taxi tests calling for numerous revisions to the oil and radiator ducts/inlets.
6th A vibration problem had been identified with the original drive shaft that a redesigned crankshaft Edit: change to drive shaft) with thicker walls was supposed to be part of the cure. This heaver drive shaft had NOT been fitted prior the the XP-39 going to Langley so the chances of the XP-39 being operated at anywhere full power before going to Langley are exceeding slim.
7th, if the XP-39 had come anywhere near the claimed figures in actual flight why did the Army and Bell make all the changes recommended by the Langley Wind tunnel people after they claimed the wind tunnel showed a max speed of 340mph?

Edit: for the P-40 327mph was the top speed of the XP-40 in one of it's radiator configurations. it went through several.

 

[Micdrow]

That's the book I have, too. I do wish it would be republished in English because it has some fantastic photos. I'd also prefer it to be in larger format and printed on better quality paper so the photos were clearer...but that's just me being greedy.

LOL I guess I am greedy as well because that would be on my requests if it was republished.

 

[Jenisch]

Thank for the informations.

Shortround6, do you have any information about a Ki-43 III version produced by Tachikawa achieving a top speed of 358mph? Because it's a information one can find on the internet, but I have the impression it could be suspicious data.

 

[Shortround6]

Shinpachi probably has better information and would be the final word on the matter. I do have print books (old ones) that give that speed for a late model Ki-43 but there may be some confusion. Some KI-43s got a late model Sakae engine (or army equivalent) with short exhaust stubs for ejector exhaust like late model Zeros. Some may also have gotten water injection.
Tachikawa may have fitted a couple of prototype planes with a model of the Kinsei engine (actually Army equivalent) similar to that used in the A6M8.
The 358mph speed seems quite plausible if that is the case but operational use may have been either near nil or nil.

 

[Shinpachi]

Thanks Shortround6 but this is just my guess.

(1) International mile = 1,609.344 meters
(2) International nautical mile = 1,852 meters

If the 358 mph is true,

(1) approx 576km/h
This might be possible speed.
(2) approx 663km/h
This is hard to believe.

Max speed of the Ki-43-III is said around 560km/h with the water injection

(1) 560km/h = approx 348 mph
(2) 560km/h = approx 302 mph

I don't believe the (2) approx 663km/h in any case.

 

[tomo pauk]

I believe that speed in (statute) miles per hour is always stated as 'mph'. Speed in nautical miles is in 'kt' or 'kts' - knots. Knots are in use today, unlike mph in international air traffic.

 

[Jenisch]

The top speeds we find in specifications of aircraft are always with military power, isn't?

 

[tomo pauk]

Nope. The term 'military power' is American, and they were sometimes expressing the speed with engine making WER, and sometimes max continuous/normal power.

 

[Jenisch]

In regard to the Japanese published speeds, the Japanese always used the continuous power, not? I think I have already heard something about this.

BTW: what is the problem with Japanese performance data? Here in the West people use so much Allied test data of the Japanese planes. But what about the testes conducted by the Japanese themselves?

 

[Shortround6]

Nope. The term 'military power' is American, and they were sometimes expressing the speed with engine making WER, and sometimes max continuous/normal power.

This one is a can of worms as different countries used different terms and some terms or conditions changed even in the same country over time.

I will probably screw this up but as examples some of the US radials used in the mid to late 30s ( and into the first year or two of the war (1939-40 on purchased aircraft) had a take-off rating and a max continuous/normal power rating and NO military power rating. At some point the engines were allowed (officially, what pilots were doing with them in combat could be different) to use the take-off conditions (RPM and/or boost level) for brief periods of time. this condition limits or ones very similar were called "military power" by the Americans. The early time limit on American engines was 5 minutes. As an example the P & W R-1830 engine used in many aircraft was allowed to use 2700rpm for take-off but was only allowed to use 2550rpm in the air in the early versions. At some point it depending on model it could use 2700rpm for 5 minutes as a military power rating at altitude.

Several other engines around the world (certain DB 601s and Russian M-105 engines) were also allowed to use either higher rpm or boost for take-off for 1-2 minutes than they were allowed to use in flight.

Please note that WER pretty much only works at altitude below the max full throttle height of the engine and that for a number of planes the maximum speed changed only a little. the altitude at which it reach maximum speed changed a lot. For instance a P-40N-1 (important as that was the stripper version) was supposed to hit 371mph at 17300ft using 3000rpm and 44.5in Manifold pressure and making 1125hp. It was supposed to hit 378mph at 10550 ft using 3000rpm and 57in manifold pressure and making 1480hp. The supercharger was simply incapable of maintaining the 57in of manifold pressure above 10550ft and the manifold pressure and power would continually fall and get closer to the 44.5in pressure the higher the plane climbed (and it could not hold the pressure quite as high in a climb as it could in level flight) At 10550ft and below the plane was much faster using "WER" and as the plane gained altitude the speed difference got much closer until at 17,300 ft it didn't matter what the pilot did with the throttle/boost control. 44.5 in was it.

British had a different problem with early Merlin IIIs. They used such a high altitude supercharger on the Merlin that they had to limit take-off power to 880hp using the throttle and could progressively open the throttle as they climbed. This was due to the 87 octane gas and was to prevent detonation. But again the use of combat boost changes the altitude at which top speed is reached much more than it changes the actual top speed. see;
http://www.spitfireperformance.com/spitfire-I-rae-12lbs.jpg

Absolute top speed changes by about 5mph using 12lb boost instead of 6 1/4 but the altitude decreases by around 5500ft. Granted at 12500ft the speed changes by over 30mph.

 

[Shortround6]

In regard to the Japanese published speeds, the Japanese always used the continuous power, not? I think I have already heard something about this.

BTW: what is the problem with Japanese performance data? Here in the West people use so much Allied test data of the Japanese planes. But what about the testes conducted by the Japanese themselves?

The first maybe true but it may depend on the type of engine. Some of the radials might be operating at closer to "maximum" power than at the continuous rating than some V-12s. For instance using American engines the Allison was rated at 1000hp continuous and 1150hp military for a 15% gain. The R-1830s in a B-24 were rated at 1100hp continuous vs 1200hp military for a 9% increase in power. Please note that both continuous ratings required full rich mixture and sucked fuel at a very high rate. For the R-2600 used in the Avenger difference was 1700hp vs 1500hp in low blower below 3000ft and around 1450hp at 12,000ft military vs 1350hp max continuous.
Yes there will be an increase in performance, just don't expect a big one.
The cube law says a plane that needs 1000hp to go 330mph will need 1190hp to go 350mph (if I have done the math right).

Two possible problems with getting Japanese test results.
1. The Americans may have been less interested in collecting data. The war was over, in May/June/July of 1945 the end of the war against Japan was much less clear and perhaps captured German data could help in the war against Japan.
The Americans may not have perceived Japanese data to be very valuable.
2. There may not have been as much data to collect. The Japanese having been subject to bombing on a scale at least as heavy as Germany in many cities or factory areas and Japanese construction tended to burn better.

 

[XBe02Drvr]

Anything that's built by Metric specifications is foreign!!

Never mind metric, British Standard is TRULY foreign! As late as the mid 80s we were working on RR Dart engines that still had BS hardware on them. Can't buy those tools this side of the pond. A local Brit custom car builder used to smuggle them in for us on his annual visit to the Mum in Yorkshire.
Cheers
Wes

 

[fubar57]

LOL I guess I am greedy as well because that would be on my requests if it was republished.

If you have loooooooooooooooooots of free time, use Google translate. Instead of using the type writer, you draw the Japanese characters. As you draw it also gives you hints as to what the character might be, much like auto-correct in text messaging. I've done it a few times and it takes quite a while

 

[GrauGeist]

Never mind metric, British Standard is TRULY foreign! As late as the mid 80s we were working on RR Dart engines that still had BS hardware on them. Can't buy those tools this side of the pond. A local Brit custom car builder used to smuggle them in for us on his annual visit to the Mum in Yorkshire.
Cheers
Wes

Oh I know!
I had a friend who collected Morris Minors and I used to help him work on them.
The hardware was threaded metric, but the bolt heads were BSW - what a complete pain in the azz...

 

[XBe02Drvr]

Somebody should have shot Sir Joseph Whitworth before he could spawn all his whacko ideas, like British Standard, and like the 1 turn in 20" HEXAGONAL BORE rifle barrel that defeated the American rifle teams at the Wimbledon and Creedmore matches, and killed many a Union general and artilleryman in the civil war! And he's the guy who visited Robbins & Lawrence in Windsor VT and took their precision machine tool and mass production ideas home to Britain and cranked out enough Enfield Rifle Muskets fast enough to stop the Russians in Crimea. (Funny how history repeats itself! Wish we could do that now.)

 

[vikingBerserker]

That's the book I have, too. I do wish it would be republished in English because it has some fantastic photos. I'd also prefer it to be in larger format and printed on better quality paper so the photos were clearer...but that's just me being greedy.

I so agree! I burned out Google Translate App taking pics of the pages and having it translate them.

 

[yulzari]

Somebody should have shot Sir Joseph Whitworth before he could spawn all his whacko ideas, like British Standard, and like the 1 turn in 20" HEXAGONAL BORE rifle barrel that defeated the American rifle teams at the Wimbledon and Creedmore matches, and killed many a Union general and artilleryman in the civil war! And he's the guy who visited Robbins & Lawrence in Windsor VT and took their precision machine tool and mass production ideas home to Britain and cranked out enough Enfield Rifle Muskets fast enough to stop the Russians in Crimea. (Funny how history repeats itself! Wish we could do that now.)

Actually the Whitworth polygonal bore was another one of Brunel's ideas built for him by Westley Richards. Brunel deliberately chose not to patent it so that Britain's gun makers could use it for future army rifles but Whitworth stuck in the patent after Brunel let Westley Richards demonstrate it to Whitworth. It turned out that Whitworths' hexagonal bore fouled too easily for a standard service rifle (and was overpriced). Whitworth always threatened to sue anyone who tried to use polygonal rifles but when Westley Richards used Brunel's octagonal bore in their Monkey Tail (I have one of the carbines) breechloader he realised that Westley Richards had the evidence to defeat any legal action so the barrels carried 'Whitworth Patent' on the barrel but Westley Richards never paid any royalty.

Also it was a purchasing commission that went to the USA to investigate machinery for making interchangeable parts for the Pattern 1853 rifle musket although Whitworth had visited assorted American machine makers in the past. The Crimea weapon was the Pattern 1851 rifle musket colloquially called the Minie Rifle. That was not made of interchangeable parts nor were the non Enfield government factory weapons sold to both sides in the American difference of opinion by the British and Belgian trade. Only the London Armoury Company weapons were interchangeable and sold to that market and they too had invested in American machinery. I can attest to the problems of period non interchangeable Pattern 1853 rifle musket based Snider as I have one I made up from 4 different ones and b*gger all fits together without hand fitting. After the unpleasantness the USA chose to standardise on the indigenous Springfield rifle musket as it was interchangeable and the hundreds of thousands of surplus and captured Enfields were sold off supplying the Belgian trade with the source material for Snider breechloader conversions amongst others.

Whitworth's foray into small arms was deeply resented by the trade as he was paid a huge sum to do research and came up with a rich man's toy which was even superceded in competitions by more conventional rifling in the same bore.

As an engineer generally he was worthy of his fame and his championing of accurate measurement and standard threaded fasteners was a huge step forwards but his contribution to small arms was feeble at best for all it's hype.

 

[XBe02Drvr]

The story behind the story. Thanks, yulzari!
Cheers,
Wes

 

[yulzari]

The story behind the story. Thanks, yulzari!
Cheers,
Wes

As a piece of OT follow up trivia. After the 1870 war the Germans sold 100,000 ex USA Civil War captured Springfield rifle muskets to the Turks at 1$ each for which the French had recently paid 12.50$ each. The Turks then converted them to breech loaders on the Polivache system in their factory in Turkey for their shortened version of the Enfield Snider cartridge. Some were still being used in places like the Yemen by the Turkish army in WW1. The Turks bought even more ex USA Civil War Enfield Pattern 1853s direct from the USA and some were converted as Snider breechloaders by the Belgians and shipped on to Turkey and others went direct to Turkey for Polivache conversion. All of these saw service in the time of the Russo-Turkish war and the Balkan Wars as second line weapons. So Dear US Readers, your Civil War weapons were still being used up to and including WW1.

 

[vikingBerserker]

If you have loooooooooooooooooots of free time, use Google translate. Instead of using the type writer, you draw the Japanese characters. As you draw it also gives you hints as to what the character might be, much like auto-correct in text messaging. I've done it a few times and it takes quite a while

If you have a smart device use the Google Translate App, you take a picture of the text and it will translate it for you and I know it works on this book as that's the reason why I got the Appp