Spitfire vs different models of zeros

Discussion in 'Flight Test Data' started by Micdrow, Aug 13, 2007.

  1. Micdrow

    Micdrow “Archive”
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    Spitfire comparisons vs different models of zero's

    Enjoy
     

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  2. Wildcat

    Wildcat Well-Known Member

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    Excellent!! Still scouring the Australian archieve eh! I loved the comment from the Beaufighter report "Watch out s/e fighter boys or you will be out of a job" :lol:
     
  3. Micdrow

    Micdrow “Archive”
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    Yeah there is lots of info there, just takes alot of time finding stuff of interest. Its surprising though what you can find if you take the time.
     
  4. Wildcat

    Wildcat Well-Known Member

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    Tell me about it! I've spent many hours going through various squadron ORB's. fascinating stuff.
    Many thanks for your efforts mate, I for one appreciate it!
     
  5. Micdrow

    Micdrow “Archive”
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    Your welcome Wildcat. I wonder if we make a squadron ORB thread in the Main technical message area on the info there if people would be interested?
     
  6. Maharg

    Maharg Member

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    I totally agree with you Wildcat.

    MD you have gone above and beyond for this forum. Thank you very much. :)

    All the best.
    Graham. :thumbup:
     
  7. Micdrow

    Micdrow “Archive”
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    Thanks again guys and your welcome, to be honest I never in my wildest dreams thought that this would go so far or this big.

    Thanks again!!!!
     
  8. slaterat

    slaterat Member

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    Thats a great find thanx.

    Slaterat
     
  9. Ivan1GFP

    Ivan1GFP Member

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    Hello All,
    That Spitfire Vc versus A6M3-32 comparison makes interesting reading. (I presume these were the models being compared.)

    One interesting thing I found was the quoted maximum speed of Hap:
    335 mph @ 16,000 feet with engine at 2600 rpm and 40" boost (about +250 mm) seems to be way too low of a throttle setting. 2700 rpm is the military power setting and 2750 rpm at 41.7" boost (+300 mm) is WEP setting.

    This is a minor change in topic, but recently I have been watching You-Tube videos. Some appear to be historic Japanese and some are of a A6M5 (61-120) that is still flying today. I watched a Ki-43-I Oscar do a full 360 degree roll in about 1.5 seconds. The modern A6M5 did a full 360 degree roll in 3.1 seconds and did not appear to be really rolling as fast as he could. I have seen the tables in NACA Report 868 which suggest that at least the Zero should roll a whole lot slower. Capt. Eric Brown suggests that the Zero did not have a high roll rate. The A6M5 pilot (Steve Hinton?) claimed that the Zero had a very good roll rate. With the Huge ailerons, I would guess that the A6M5 pilot was right.

    How does one resolve all these conflicting reports?

    - Ivan.
     
  10. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Keep in mind as well the flying Zeros you see today don't have original engines as far as I know.
     
  11. Ivan1GFP

    Ivan1GFP Member

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    This particular A6M5 Zero is the only one still flying with the original Sakae 21 engine (1695 CID). The others are all flying with some variant of the P&W R-1830. I don't see how a slight engine change would affect the roll rate that much.

    - Ivan.
     
  12. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    I would investigate the difference in torque between the 2 engines with their respective propeller installations. I know Steve Hinton and run into him several times a year, the next time I see him I'll ask him about his comments.
     
  13. Ivan1GFP

    Ivan1GFP Member

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    Please ask him what he thinks the maximum roll rate is on the A6M5 he flies, and "Does he know that he is contradicting NACA Report 868?"

    ;)
    - Ivan.
     
  14. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Will do Ivan - I may out his way at the beginning of December, anytime I'm at Chino I always try to get by the museum. If I don't see him then, It might not be till the spring or early summer.
     
  15. Matt308

    Matt308 Glock Perfection
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    It could also be self imposed restrictions on aerobatics to minimize airframe stress.
     
  16. HoHun

    HoHun Active Member

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    Hi Ivan,

    >One interesting thing I found was the quoted maximum speed of Hap:
    335 mph @ 16,000 feet with engine at 2600 rpm and 40" boost (about +250 mm) seems to be way too low of a throttle setting. 2700 rpm is the military power setting and 2750 rpm at 41.7" boost (+300 mm) is WEP setting.

    Good catch! Here is a translation of an original document listing engine data, translated by our forum member Shinpachi:

    http://www.ww2aircraft.net/forum/engines/japanese-piston-engines-8450.html#post381951

    >I have seen the tables in NACA Report 868 which suggest that at least the Zero should roll a whole lot slower.

    I believe the graph in question is annoted "Force limits unknown" or something like that, so it might not be comparable to the other graphs in the diagram.

    I'd expect the A6M to have a great roll rate at low speeds - the historical reports all seem to hint at a low roll rate at high speeds only.

    Regards,

    Henning (HoHun)
     
  17. kool kitty89

    kool kitty89 Well-Known Member

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    Here's the chart:

    [​IMG]
     
  18. bruno_

    bruno_ Member

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    Maybe most of the people know very well this subject but for the few still not yet inside it, it could be worth nothing that when looking to roll rates figures and graphs, one should take into account they refer to the "steady state roll rate", that is the amount of degree per second the aircraft rolls once the transient phase is over. In most combat situations, however, is the inital (transient) phase to be important, since during these few seconds it is vital to quickly change the direction of the "lift" vector in order to gain angular separation between you and the enemy. And typically once you have got, let us say 90* or some more roll, you've got your result. Then it's no more a matter of roll but, it's a problem of turn rate.
    Steady state roll rates, by way of example, aren't affected by the moment of inertia of wings etc, whereas the transient rolling performace heavily depends on it.
    As to the Zero rolling performance, I've read that this kite suffered more than other aircrafts for the aeroelesticity of its wing structures. In poor words, the deformation of wing/aileron profiles, under the the rolling command, partly compensated the intended ailerons deflection thus reducing the net effect. In limit conditions, such compensation is total. Almost all aircrafts suffer from these problems but the Zero more than the average. On the other side Zero was delightfully light. Thus a good transient roll performance could be compatible with a poor steady state one.
     
  19. Ivan1GFP

    Ivan1GFP Member

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    Hi HoHun,

    I am following that thread with the notes by shinpachi as well. Really good information! I believe I also have a question in that area for the Compression Ratio of the Sakae 21.

    The point I was trying to make was that if the speed of the A6M3-32 was 335 mph without even using full throttle, I would imagine that it would be significantly faster at the full throttle setting, yet most sources quote a figure around 335 mph for this plane.

    The aero-elasticity aspect is noted in the book "Eagles of Mitsubishi". I am referring to timing a 360 degree roll by a A6M5 (61-120) that was shown in a You-Tube video. My stopwatch says 3.10 seconds or so which works out to around 120 degrees per second and I believe the pilot wasn't even trying hard because there was noticeable deceleration to come back to level flight.
    To me, that is pretty fast for a WW2 fighter. The video of the Ki-43-I was even more spectacular at about 1.5 seconds.

    As you pointed out, neither roll was "steady state", so the steady state roll rate should be even higher.

    - Ivan.
     
  20. Ivan1GFP

    Ivan1GFP Member

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    This may be a silly question, but what are the the standards for atmospheric pressure for the various manifold pressure ratings?

    With US, Absolute pressure in inches of Mercury are used, so there is no required "reference" pressure.

    With the Germans, a multiple of standard atmospheric pressure is used such as 1.42 ata, but how many inches of Mercury is 1.00 ata???

    With the Japanese, Millimeters of Mercury above atmospheric pressure are used. I believe their standard reference is 760 mm of Mercury from some of the numbers that were converted to Inches of Mercury.

    With the British, Pounds of pressure above one atmosphere are used. I would hope that the standard 1 atmosphere would around 14.7 pounds, but what is the precise number?

    Thanks for any information.
    - Ivan.
     
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