Performance of Japanese aircraft inflated (or deflated)?

[Hardrada55]

When I was a kid, I remember seeing a book in which there was information about the maximum speeds of various Japanese military aircraft that was substantially different from the information available in generally available reference material of the time (late 1960s). If my memory serves me well, it was generally late war Japanese fighter and Japanese naval aircraft that seemed to have this discrepancy. It also seems that every one of these late war Japanese aircraft mentioned in this book had a top speed 20 to 40 mph faster than what was generally accepted. I think they had NIK2-J with a top speed of about 416mph. I remember this because at the time I related it to the top speed of the FW 190A-4 which with water injection (MW 50) was the same speed. Now, the only example of this inflation in performance I can find is the performance of the Japanese Nakajima Ki-84 in Rene Francillion's book "Japanese Aircraft of the Pacific War". Ki-84 is credited in the performance chart with a top speed of 392mph. But, on page 236 of the book it says in 1946 a Ki-84 reached 427mph. Does anyone else have any information about this discrepancy between actual late war Japanese aircraft performance and their reported performance? What significance, if any, would there be to this information? I realize fuel octane ratings may have played a part in this. Thanks

[DerAdlerIstGelandet]

I am not sure if this helps but I do know that captured late war Japanese aircraft were using US fuel with higher octane and that put out better performance than the Japanese were able to get out of them.

[Twitch]

Well I've been collecting books a LONG time and can tell you that every book I own from the 1950-1960s does not have exagerated performance figures. I'm certain that you did see some cheezy book long ago from that era that had inaccurate performance data. But the mainstream manuscripts written by the likes of Bill Gunston and William Green are realistic and agree to factory-observed data.

Glancing at both these men's books show 388 MPH @ 19,680 for the KI 84.

[Jabberwocky]

Originally Posted by DerAdlerIstGelandet

I am not sure if this helps but I do know that captured late war Japanese aircraft were using US fuel with higher octane and that put out better performance than the Japanese were able to get out of them.

Putting better fuel into a fighter will not necessarily make performance jump. The engine needs to have proper compression ratios in order to make use of the extra power. RAF/USAAF fighters needed quite a few engine modifications to run effectively on 150 octane. You couldn't just bung in new fuel and expect better performance.

However, the reverse is not true. Putting worse fuel into a fighter will, in all likelyhood, make it perform worse, because it can't produce as much power. So Japanese fighters may not of benefited from recieving 115/145 or 100/130 octane as they were tuned for maximum power on 87 octane fuels. However, during the war they were often running on sub-standard 79 octane fuel, so performance may of been lower than expected. For exampe, the Ki-100 which was built very late in the war, had a seperate tank with 93 octane for startup and climbing and then switched to the main tanks with a poorer fuel grade, which were used for flight.

US tests seem to have been with captured planes that have had a complete strip and repaint and had everything tuned as close to mechanical perfection as possible. So they were probably in BETTER condition than in their original tests.

The few original Japanese documents I have seen usually give fighter level speed at maximum power, but not at emergency power. Many of the official IJAAF documents give lower performance than their real world counterparts were capable of with proper fuel and maintenence. Given the small size, light weight and high horsepower of the late-war Japanese designs, 400 mph + speeds under ideal conditions aren't really anything to raise eyebrows.

[delcyros]

I do believe Lunatic once wrote something here regarding this Ki-84. He pointed out that beside of the high grade octane there were numerous changes in the engine with a lot US tooling involved. In the end they wanted to test its airframe, not the engine or the whole service plane, this lead to an overall increased performance. Tuning the bird, that´s it.

[loomaluftwaffe]

the Japanese Homare was unreliable and it says that u arent even sure if it will make enough power to intercept the B-29s

[DerAdlerIstGelandet]

Originally Posted by Jabberwocky

Putting better fuel into a fighter will not necessarily make performance jump.

Nope but it certainly helps.

[lesofprimus]

My Grandfather fought the Japanese and didnt really concern himself too much with the aircraft he was flying against... He was fully breifed on all the aircraft he was flying against, and knew how to effectivly fight against them...

The pilots were a different story... He flew and fought against the man with the stick in his hands, not the kite the pilot was sitting in...

As a side story, I remember him telling a story of a lone Japanase Ace who fought my Grandpa and 2 other Blacksheep for 20 minutes before they had to leave... He was so close to him, he could see kills painted on his fuselage.... Alot of em....

Never have been able to confirm who this was, much to his chagrin..

[loomaluftwaffe]

My Grandfather has seen a Zero shoot down a Mustang over his town, when they were being liberated. The pilot of the P-51 was lost

[FLYBOYJ]

I think many aviation authors make errors when gathering data on aircraft performance, I seen them mix up True Air Speed for Indicated Air Speed, and Knots for MPH. I think these days things are more accurate especially with Internet access to performance charts and original test data now posted on the Internet.

I believe the Zero was over-rated and the bravery of the Japanese pilot under-rated.

[DerAdlerIstGelandet]

Originally Posted by FLYBOYJ

I believe the Zero was over-rated and the bravery of the Japanese pilot under-rated.

I agree with you 100% on this. That does not mean the Japs were not able to make good aircraft and certainly does not mean the Zero was a bad aircraft. It was a great aircraft it was just overrated and the Pilots bravery was somethign that can rarely be equalled.

[Gnomey]

Originally Posted by DerAdlerIstGelandet

I agree with you 100% on this. That does not mean the Japs were not able to make good aircraft and certainly does not mean the Zero was a bad aircraft. It was a great aircraft it was just overrated and the Pilots bravery was somethign that can rarely be equalled.

Agreed, well said.

[lesofprimus]

I feel slightly different on the Zero.... SLIGHTLY.... At the beginning of hostilites in the Pacific, the Zero was unmatched in combat.... Then we learned how to NOT to fight against a skilled Jjapanese Ace and his little wooden unarmoured kite....

Just how many young American/Australian/English kids went down in flames whilst trying to out turn a Zero at 200mph????

Once the lesson was learned and that they didnt have self sealing fuel tanks, the mystique and the surpremecy of the Zero was over...

However, this still didnt stop Navy and Marine Corps pilots from losing their lives to a decent pilot in one...

[syscom3]

However, this still didnt stop Navy and Marine Corps pilots from losing their lives to a decent pilot in one...

I think more than one allied pilot was lost thinking that the Japanese fighter hes about to shoot down was piloted by an inexperienced rookie.

Imagine the surprise when the Japanese pilot turned out to be a veteran who knew what to do.

[lesofprimus]

Yea... My Grandfather did that, once, and got shot full of holes because of it... He never did make that mistake again...