Mitsubishi Ki-21 Sally top speed

Discussion in 'Aviation' started by Johnny .45, Jan 25, 2014.

  1. Johnny .45

    Johnny .45 Member

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    I just looked up the Wikipedia article on the Ki-21 Sally; it's been a while since the last time I read it so I can't recall what it said before, but I was surprised to note that its top speed it listed as "305mph". This sounds excessive for a plane that was introduced in 1936. Admittedly the Ki-21-II was given much more powerful engines than the original, but a top speed like that would make it a very quick medium bomber indeed. Does anyone have any book confirming or contradicting that number? It sounds too high. The G3M is only a year older, designed by the same company, and it can't better 233mph. The G4M is even newer, and doesn't have any more armor or bombload or range than the Ki-21, and it's only 265mph. The Ki-49 which replaced the Ki-21 was supposedly "not that much faster" than the Ki-21, and it only lists 306mph, which might as well be the same speed.
    B-25:272mph
    Wellington: 235mph
    Do 17: 217mph
    He 111: 193mph
    BR.20: 270mph
    G3M: 233mph
    G4M: 265mph
    Ki-49: 306mph
    Ki-21: 305mph
    See what I mean? It seems a little out of place among all those other numbers, even considering the lack of armor and self-sealing tanks (the G3M and G4M didn't have those either). The only other plane that breaks into the 300's is the Ki-49, which is a next generation bomber.
    If that number is correct, then I'd say it suggests that they did a very good job on the aerodynamics of the Ki-21, and one has to wonder why the Navy stuck with a slowpoke like the G4M when the Ki-21 was so much faster and carried just as big a bombload.
     
  2. GregP

    GregP Well-Known Member

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    I have its top speed listed as 268 mph. Actually listed as 432 kph.

    That comes from a 1946 boook published in Japan entitled "General View of Japanese Military Aircraft in the Pacific War," Kantosha, Tokyo, Japan.

    That agrees exactly with several other references within 1 mph.
     
  3. tyrodtom

    tyrodtom Well-Known Member

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    #3 tyrodtom, Jan 25, 2014
    Last edited: Jan 25, 2014
    Some of the top speeds you've listed for the aircraft you're comparing the Sally to are way off.

    The DO17 top speed you list as 217 is it's top speed at sea level, it top speed at altitude is 255.
    You list the top speed of the He111 as 193mph. That's the first models of the He111, with two 660 hp engines.
    When it had the engines it had early WW2, 1300 hp, it's top speed is 273 mph. 80 mph higher.

    If the He111 can get a boost in top speed of 80 mph from 1300 additional hp, why can't the Sally get a 40 mph increase from a 1100 hp increase?

    And why did the IJN stick with the Betty ? Check out the Betty's range, and compare it with any other aircraft in the world in that time period..
     
  4. nuuumannn

    nuuumannn Well-Known Member

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    #4 nuuumannn, Jan 26, 2014
    Last edited: Jan 26, 2014
    Yep, Tom's right, Johnny, your figures don't match.

    To begin with, the Ki-21 and the G4M were designed for different services, one was for the army and one was for the navy - two very different organisations with different requirements. The G4M was bigger and heavier than the Ki-21 and had a larger crew to operate its more satisfactory defensive armament, which was one criticism of the Ki-21. Although the latter had the same/similar war load in terms of weight, its bomb bay was smaller. The G4M had a bigger bomb bay because it was also capable of carrying a torpedo, which the Ki-21 could not do, not having a requirement to do so. Also, although the two aircraft had the same maximum load, the Ki-21 had a smaller standard load with a useful range, whereas the G4M could fly a longer mission with a bigger useful load.

    Lastly, the G4M's range - like Tom intimated, was very impressive; no other twin engined bomber of its size had the same combat radius, although as we know that came at a price and when the G4M-3 entered service, with more powerful engines, self sealing tanks and armour plating, it was too late to make a difference, although it was the fastest of the G4M variants with a maximum speed of 292 mph at 16, 895 ft.

    Johnny, I think you might be impressed by the wrong aircraft; you should be admiring the G4M for its abilities, rather than the Ki-21. What the Japanese achieved with the G4M in terms of performance is more impressive; despite being bigger and heavier, the G4M managed to carry a greater useable load than the Ki-21 across a far greater distance - more than twice that of the Ki-21 - at a slightly lower cruising speed, of course, but still creditable compared to its foreign contemporaries, all the more so considering what it could do.
     
  5. Johnny .45

    Johnny .45 Member

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    I just grabbed all those numbers straight from the info boxes on Wikipedia at the last moment. Any inaccuracy can be blamed there. As for the rest, I don't think I'm "impressed with the wrong aircraft" (I like all Japanese aircraft), I was just surprised at the top speed being listed so much higher than the G4M's. Maybe none of the numbers I saw are any more accurate than the top speeds I listed, but according to them the two aircraft had roughly equal range and the Ki-21 had a slightly larger bombload (although I don't know about carrying a torpedo...the G4M was semi-external as it is though). But who knows accurate those numbers are; they don't specify whether it is with or without a bombload. I suspect that is the key, but the Ki-21 was considered long-legged too. Maybe is wasn't as much as the G4M, but that wouldn't be surprising. What would is a true 305mph bomber of that size. It wasn't a small plane, even if it weighed less than a G4M (which was big enough to be a 4-engine plane itself).
     
  6. tyrodtom

    tyrodtom Well-Known Member

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    I got those figures from the same WIKI article you did.

    The DO 17 top speed of 217MPH was listed as at sea level, the higher top speed at altitude of 255 was right beside it.
    The top speed of He111 of 193 planely stated it was for the 660 hp very early model He111, the specs for the WW2 1300 hp He111 was actually before the early model, in the same WIKI article
    .
    You just didn't see them. That's not WIKI's fault.

    Weights , wingspans, ranges are in the WIKI article also.
     
  7. RCAFson

    RCAFson Well-Known Member

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    Apparently there are 2 versions of the Ki-21, the Ki-21-I with 2 x 850hp engines = 268mph @ 13000ft and the Ki-21-II with 2 x 1450hp engines = 302mph @ 15500ft. Max weight was only about 23000lb, for the II and 17000lb for the I so these numbers seem reasonable.
     
  8. tyrodtom

    tyrodtom Well-Known Member

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    I think most of us know Wiki isn't the definitive source of information on aircraft performance.
    But it does usually give some of the speeds, and the altitude at which they were achieved , but they will hardly ever give the weights at which some of those performances were at.

    It's just a easy place to get quick, general information.

    I've got a couple hundred books myself , thousands if you count old magazines, on aircraft, and other military , or technical subjects. But I usually go to the internet if I want some general information quick.
     
  9. Johnny .45

    Johnny .45 Member

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    I can't afford books, so I come here to ask people who can.
     
  10. Shinpachi

    Shinpachi Well-Known Member

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    Maximum speed of the Ki-21 model 2, the most produced model, is 297mph(478kmh) with the engine Ha-101 for 1,500hp.

    Wiki japan
     
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