Ki-61 Relativity

Discussion in 'Engineering Retrospective' started by squirl, Sep 25, 2005.

  1. squirl

    squirl Well-Known Member

    Joined:
    Jul 21, 2003
    Messages:
    853
    I have recently been pursuing conclusions which can be made from the tests which were conducted during the Ki-61's development.

    -both of these quotes came from an encyclopedia volume in a local library

    Many websites include the same passage:

    Here:

    and here:

    ...both can be found after only minutes of searching.

    The interesting concept here is that we have a "link" between a Japanese fighter and several Western fighters. By using logical relativity (if A is greater than B, and B is greater than C, then A is greater than C), we can determine how a Ki-61-I would have performed against fighters which it may never have faced, all through the use of "mediums:" the P-40E and Me-109 E-3.

    Relativity #1: the Ki-61-I has a better turning circle than the Me-109 E-3

    Reason: above data

    Relativity #2: the Ki-61-I has a better turning circle than the P-40E

    Reason: above data

    Relativity #3: the Ki-61-I has a better turning circle than the P-38

    Reason: Eric Bergerud's Fire in the Sky: The Air War in the South Pacific has a quote from Robert DeHaven, a P-40 pilot who later flew the P-38.

    Dehaven:

    If the Ki-61 was more maneuverable than the P-40, and the P-40 was more maneuverable than the P-38, then the Ki-61 was more maneuverable than the P-38.

    Relativity #4: the Ki-61-I has a better turning circle than the P-39

    Reason: this source

    The P-39N and the P-40N are almost identical to their earlier counterparts, in terms of weight and power. Additionally, the source states that both the P-39 and the P-40 had a similar advantage over the P-51B in a turning circle. This leads one to believe that the two planes had roughly the same turning ability. Therefore, if the Ki-61-I could easily out turn the P-40, and the P-40 had roughly the same maneuverability of the P-39, the Ki-61-I could out turn the P-39. I admit that this is a long stretch as far as relativity is concerned, but even if the P-39 were slightly better than the P-40 in a turning circle, the fact that the Ki-61-I could easily out turn the P-40 and that the P-39 could only slightly out turn the P-40 would imply that the Ki-61-I would still be able to out turn the P-39.

    Relativity #5: the Ki-61-I has a better turning circle than the P-51

    Reason: this source

    This relativity is based upon the previous example. If the Ki-61-I could out turn the P-40, and the P-40 could out turn the P-51, then the Ki-61-I could out turn the P-51. The Ki-61-I would most likely out turn the P-51D as well, because the P-51D was heavier than the P-51B with the same size wing.

    Relativity #6: the Ki-61-I has a better turning circle than the Me-109 G

    Reason: this site

    Though this article does not name any version of the Me-109 in particular, the History Channel show, which covered this very dogfight, stated that the 109 in question was a 109 G and that the nose gun was a 30mm, not a 20mm. I find it interesting how the quoted article appears to be taken from a personal account of Bud Anderson, but it differs from an actual television interview of the same person recalling the same event. In any case, the P-51B was shown to be capable of out turning the Me-109 G. If the Ki-61-I could out turn the P-51B, and the P-51B could out turn the Me-109 G, then the Ki-61-I could out turn the Me-109 G. Though this connection may seem loose, bear in mind that the Ki-61-I could also out turn the Me-109 E-3 which was, by far, lighter and more maneuverable than the Me-109 G series. Still further, there was this post comparing the turning circles of the P-51B to the Me-109 G:

    Relativity #7: the Ki-61-I has a better turning circle than the Hawker Tempest

    Reason: this post

    The Mustang which is mentioned in the quotation is a P-51B. If the Ki-61-I could out turn the P-51B, and the P-51B could out turn the Tempest, then the Ki-61-I could out turn the Tempest.

    Relativity #8: the Ki-61-I has a better turning circle than the Hawker Typhoon

    Reason: this post

    This is another somewhat vague description of turn comparison. I can still make a judgement based upon the fact that the Tempest is out turned by the P-51B, which is out turned by the P-40, which is out turned by the Ki-61-I. This means that the gap between the Tempest and the Ki-61-I is large enough to suggest that the Typhoon would also be out turned by the Ki-61-I, even if it were slightly better than the Tempest.

    Relativity #9: the Ki-61-I has a better turning circle than the FW-190

    Reason: this post

    This was the result of a turn comparison between the Tempest and FW-190. Even if this FW-190 has a turning circle which is identical to the Tempest's, it is still inferior to the P-51B, which is inferior to the P-40, which is inferior to the Ki-61-I. The only problem here is that the version of the FW-190 is not given (though I am led to believe it is a FW-190 A-3), but there are so many relativity gaps between the FW-190 and the Ki-61-I that I am confident that the sum of these gaps gives the Ki-61-I a great turning advantage over all 190's.
     
  2. squirl

    squirl Well-Known Member

    Joined:
    Jul 21, 2003
    Messages:
    853
    I have been unable to find a solid way to link the Spitfire series, US Navy fighters and most Russian fighters to the turning performance of the Ki-61-I. With some help, however, I may be able to draw a conclusion about the Spitfires' turning performance relative to the Ki-61-I.

    First, we can look at this source.

    This webpage provides the turn radii of the Me-109 E-3 and Spitfire Mk.I at 12,000 feet, with the indicated airspeed of the turn.

    [​IMG]

    There is also this source.

    No airspeed is given, however.

    I think it is very possible that we can use this information to determine how the Ki-61-I would match up with the Spitfire V and Spitfire IX. After all, the Spitfires V and IX had almost the same wing as the Spitfire I (aside from cannon bulges and barrels). This is why I think we can derive the turn radii of the Spitfire V and IX at 12,000 feet.

    Of course, before we could do anything, we would need to decide which of the two sources is more accurate, because the numbers differ greatly. One says the 109 E-3 had a turn radius of 885 feet at 12,000 feet. The other says the 109 E-3 had a turn radius of 754 feet at almost 20,000 feet - a tighter turn in a much thinner atmosphere! Many say the British test (the 885 feet radius test) was inaccurate because the British tested a damaged 109 E-3. Others claim the German numbers are inflated propaganda estimates. In any case, we would need to sort this out before an evaluation could be made.

    Still, it is very convenient that the Spitfire I was tested against the exact model of 109 that the Ki-61-I was tested against. If we get conclusive numbers, this convenience may permit a comparison between the Ki-61-I and the Spitfire V and IX.
     
  3. PressLuftHammer

    PressLuftHammer FH Beta Tester

    Joined:
    Mar 5, 2003
    Messages:
    13,933
    Location:
    Ekaterinburg (Russia)
    Spit I, V and IX have equal wings.
    But different Take-off weight.
    Spit I have weighth about 2600 kg,Spit V weight about 2800 kg Spit IX weight about 3300 kg.
    Hence Spit V and Spit IX have biggest turn radius.
    But Spit V and Spit IX have powerfull engines.
    Hence Spit V and Spit IX have highest speed in turn.

    For comparsion Load wing
    Spit I 121 kg /M^2
    Spit V 125 kg /M^2
    Spit IX 147 kg/M^2
    Ki-61b 158 kg/M^2
    Yak-9 167kg/M^2
    Bf.109F-2 172kg/M^2
    Yak-3 179kg/M^2
    Bf.109G-2 185kg/M^2
    Fw.190A-4 216kg/m^2
     
    Last edited: Sep 26, 2005
  4. HoHun

    HoHun FH Beta Tester

    Joined:
    Sep 22, 2001
    Messages:
    2,643
    Hi Presslufthammer,

    >Spit I have weighth about 2600 kg,Spit V weight about 2800 kg Spit IX weight about 3300 kg.

    These weights seem to be a bit on the low side for all three Spitfire models.

    >Ki-61b 158 kg/M^2

    It seems you're using a higher weight for the Ki-61 than I do?

    The Ki-61 apparently had an F2R wing section like the Me 109, so its Clmax was a bit higher than the Spitfire's.

    In my opinion, the Ki-61 should outturn the Spitfire IXc below 6 km. With the earlier Spitfires, it depends on engine power with the Spitfires probably superior, but the Ki-61 should have the smaller turning radius in any case.

    Regards,

    Henning (HoHun)
     
  5. PressLuftHammer

    PressLuftHammer FH Beta Tester

    Joined:
    Mar 5, 2003
    Messages:
    13,933
    Location:
    Ekaterinburg (Russia)
    Spit I 6000lb 2728kg (U right) 121 kg/M^2
    Spit V 6695lb 3023 kg (U right) 135kg/M^2
    Spit IX LF (Merlin 66) 3292kg Take-off weight at test NII VVS
    For this plan have data test time turn 17,5 sec radius 235m at alt=1000m

    American test data 6892lb 3122kg


    I'm calculate Cl for turn manuever for spit IX and 109G-2 from test data NII VVS
    alt=1000m
    Spit IX LF weigth 3292kg time 17,5 sec radius 235m result need Clman=1,18
    Bf.109G-2 weigth 3023kg time 20 sec radius 290m result need Clman=1,23

    U can see its small different.


    for compare radius need load wing and Cl manuever
    For Spit IX LF 147kg and Cl=1,18
    Ki-61b 158kg and Cl=1,23 (for R2 109G-2)

    Calculate efficient= (Load wing)*(1/Cl)
    Spit IX e=147*(1/1,18)=124,6
    Ki-61b e=158*(1/1,23)=128,5

    IMHO radius turn mb equal,
    but engine Spit IX powerfull (1580HP vs 1100HP)-> time turn Spit IX is less vs Ki-61b

    Radius turn Spit I and Spit V less Ki-61b
     
  6. HoHun

    HoHun FH Beta Tester

    Joined:
    Sep 22, 2001
    Messages:
    2,643
    Hi Hammer,

    >Spit IX LF (Merlin 66) 3292kg Take-off weight at test NII VVS

    I see. I used 7480 lbs = 3392 kg from another source, but if your weight is from a real aircraft it's good, too.

    >American test data 6892lb 3122kg

    Hm, that's TAIC data, which is a bit suspect. For example, they note "location of oxygen cylinders is unknown", which suggests that they didn't really have a Ki-61 to check.

    I'm using 6504 lbs = 2950 kg, which of course yields a higher turn rate.

    >Spit IX LF weigth 3292kg time 17,5 sec radius 235m result need Clman=1,18

    That's pretty close to NACA data which gives the Spitfire a Clmax of 1,22.

    >Bf.109G-2 weigth 3023kg time 20 sec radius 290m result need Clman=1,23

    Hm, that indicates a sub-standard aircraft. The Clmax was actually 1,49 for the Bf 109.

    >U can see its small different.

    Your calculations are correct, I'd arrive at the same conclusions from the same input data :) So it's rather a question of researching reliable input data!

    Regards,

    Henning (HoHun)
     
  7. RolandGarros

    RolandGarros Well-Known Member

    Joined:
    Mar 21, 2003
    Messages:
    2,867
    The comparison is not as simple as y'all make it out to be.
    You can generalize & estimate, but the actual flight qualities of an aircraft are not what you'll decipher. Best would be to actually test the aircraft against each other, next best maybe to use a physical simulator (like X-plane).
     
  8. squirl

    squirl Well-Known Member

    Joined:
    Jul 21, 2003
    Messages:
    853
    Loaded weight for Spitfire IX (Merlin 61):

    [​IMG]

    -from this site

    Load 1 is the Spitfire IX fitted with 4x7mm and 2x20mm; load 2 is with 8x7mm.
     
  9. squirl

    squirl Well-Known Member

    Joined:
    Jul 21, 2003
    Messages:
    853
    As far as the Spitfire LF IX is concerned, we must remember that it had clipped wingtips. This reduced the aspect ratio from 5.61 to 4.48 and the wing area from 242 ft^2 (22.48 m^2) to 231 ft^2 (21.46 m^2). It is described on this site, with my numbers coming from the Spitfire LF.Mk VC, which has the same wing as the Spitfire LF IX.

    The loaded weights of the Spitfire IX and LF IX need to be found. Everywhere I look, the loaded weights of the Spitfire F IX, Spitfire LF IX and Spitfire HF IX are all the same:

    This site:

    Mk. IX (Merlin 61 or 63)
    7300 pounds, loaded

    Mk. IX (Merlin 66)
    7300 pounds, loaded

    Mk. IX (Merlin 70)
    7300 pounds, loaded

    And Spitfire F.IX, Spitfire LF.IX and Spitfire HF.IX:

    Spitfire F IX: 7,106 pounds, loaded
    Spitfire LF IX: 7,106 pounds, loaded
    Spitfire HF IX: 7,106 pounds, loaded

    If we assume that all marks of the Spitfire IX weighed the same, then we can go with our more accurate 7,445-pound loaded weight. I am comfortable with this weight because all pieces of equipment and their weights are included in the total. So if all marks of the Spitfire IX weighed the same, and the Spitfire F IX weighed 7,445 pounds, loaded, then the Spitfire LF IX probably weighed 7,445 pounds, loaded.

    Spitfire LF IX loaded weight: 7,445 pounds (3,377 kg)
    Spitfire LF IX wing area: 231 ft^2 (21.46 m^2)
    Wing loading: 32.2 lbs/ft^2 (157.4 kg/m^2)

    The Ki-61-Ib's loaded weight seems to be an item of confusion as well.

    Rene J. Francillon quotes the loaded weight of the Ki-61-Ib as 6504 pounds (2,950 kg).

    The US report concerning the Ki-61 states that the loaded weight is 6,982 pounds (3,167 kg). There are some problems with this information, however. The empty weight is 138 pounds (62.6 kg) higher in the US report. The maximum loaded weight is also different: 7,682 pounds (3,484 kg) in the US report and 7,165 pounds (3,250 kg) according to Francillon. I am inclined to believe the Francillon numbers because Francillon's Ki-61-Ib statistics are drawn directly from Japanese reports. Francillon's weights are therefore the weights of the Ki-61 exactly as it was flown by the Japanese. The American report may have numbers from a damaged airplane or it may also use a different, "American definition" of loaded weight.

    Ki-61-Ib loaded weight: 6,504 pounds (2,950 kg)
    Ki-61-Ib wing area: 215.3 ft^2 (20 m^2)
    Wing loading: 30.2 lbs/ft^2 (148 kg/m^2)
     
  10. PressLuftHammer

    PressLuftHammer FH Beta Tester

    Joined:
    Mar 5, 2003
    Messages:
    13,933
    Location:
    Ekaterinburg (Russia)
    See attach image pls



    One moment, Cl manuever not equal Clmax, Cl manuever ~0,8..0,85Clmax
    from my airdinamic book.
    1,18/0,85 =1,388
    1,23/0,85=1,445

    But its Clmax for plan at maximum power engine and speed in turn its not equal Clmax profile wing.
    Cl max of airplan can different at speed and power.

    P.S.
    If recalculate turn radius for Bf.109F-2 with Cl manuever 1,23
    radius 267m (FH 1.61 248m)
    Bf.109F-4 274m (FH 1.61 263m)
    Bf.109G-2 radius 290m (real data NIIVVS) (FH 1.61 269m)
    Spit LF IX real data NII VVS 235m (FH 224m) (But 18,5 sec vs 17,5 sec test data NII VVS)


    May the Force be with you !!! :)
     

    Attached Files:

    Last edited: Sep 27, 2005
  11. HoHun

    HoHun FH Beta Tester

    Joined:
    Sep 22, 2001
    Messages:
    2,643
    Hi Hammer,

    >See attach image pls

    That's the TAIC data which I have, too. It's not reliable :-(

    It appears to be compiled from the investigation of wrecks, not from a real aircraft. (They would have known where the oxygen vessels are mounted :)

    >One moment, Cl manuever not equal Clmax, Cl manuever ~0,8..0,85Clmax
    from my airdinamic book.

    Ah, I misunderstood the meaning of "Clman" :)

    NACA calls this "Clmax", too, though there ould be less confusion if they used "Clman".

    For the Spitfire, Clman = 1.21, so the Russian test with 1.18 is quite accurate.

    For the Bf 109, Clman = 1.49, and the Russian test doesn't appear accurate.

    Note that the Fw 190A-5 has the same circle time as the Bf 109G-2 in the Russian test, but as every Luftwaffe pilot will tell you, the Bf 109 had superior turning abilities by far.

    Which weight did you use for the Bf 109G-2?

    Regards,

    Henning (HoHun)
     
  12. PressLuftHammer

    PressLuftHammer FH Beta Tester

    Joined:
    Mar 5, 2003
    Messages:
    13,933
    Location:
    Ekaterinburg (Russia)
    I compare with test data for La7 left and right utrn get me different Cl man 1,18 and 1,21.


    Can see source for Cl man =1.49 pls for 109?
    its US, UK or Germany test data?


    I have data for Fw.190A-4 left turn time 22 sec and radius 340m at alt=1000m
    Take-off weigth 3988 kg wing area 18,3m^2
    Cl man = 1,22 Cl max=1,44

    3023kg
     
    Last edited: Sep 27, 2005
  13. HoHun

    HoHun FH Beta Tester

    Joined:
    Sep 22, 2001
    Messages:
    2,643
    Hi Hammer,

    >Can see source for Cl man =1.49 pls for 109?
    >its US, UK or Germany test data?

    UK test. Me 109E, 5600 lbs:

    http://hometown.aol.de/HoHunKhan/spit109turn18.gif

    >I have data for Fw.190A-4 left turn time 22 sec and radius 340m at alt=1000m
    >Take-off weigth 3988 kg wing area 18,3m^2
    >Cl man = 1,22 Cl max=1,44

    Good data :) I only mentioned the Fw 190 because relativity suggests that the Bf 109 turns quicker than the Fw 190.

    >3023kg

    Hm. Do you have all figures in writing? I only have the diagrams, and they suggest a higher weight (calculating from indexed data, maybe bogus).

    Regards,

    Henning (HoHun)
     
  14. strafe

    strafe Guest

    Hello guys, nice work!
    I have some In Action, Walk Around series from Squadron, Osprey publications and some papers like "Calculated and measured turning performance of navy F2A auircraft" in pdf format. If I can help you anyway pls let me know. These books has a lot of info, but I don't know if they are so accurate to this issue.
     
  15. HoHun

    HoHun FH Beta Tester

    Joined:
    Sep 22, 2001
    Messages:
    2,643
    Hi Strafe,

    >I have some In Action, Walk Around series from Squadron, Osprey publications and some papers like "Calculated and measured turning performance of navy F2A auircraft" in pdf format.

    Thanks for the offer! :)

    At the moment, what would help us most would be data on the normal take-off weight of the Ki-61, the more detailed the better (individual components' weight, exact aircraft version etc.). Optimum would of course be something based directly on Japanese documents :)

    (The weight difference between TAIC and Francillon is so large that this is a priority item.)

    Any information on stalling speeds would be interesting, too, especially if the configuration is mentioned (power/no power, flaps/no flaps). If the Clmax is given directly, or some information on turning radii, that would be even more helpful.

    The F2A paper is quite interesting. I have a copy on my disk, but if you have the original NACA report number, that would be great for reference. My copy has been re-named, so I can't point people to the NACA server if they want to have a look for their own.

    (I found the methods of the F2A paper too difficult to apply to our planes of interest due to the sketchy nature of the data we usually have, but I believe Hammer's method and mine own are decent approximations, especially as they both yield comparable results :)

    Regards,

    Henning (HoHun)
     
  16. PressLuftHammer

    PressLuftHammer FH Beta Tester

    Joined:
    Mar 5, 2003
    Messages:
    13,933
    Location:
    Ekaterinburg (Russia)
    [​IMG]
    We can see 1,49 it is Cl max for Bf.109E-3 at over G 3.0g
    and Cl max =1,45 for Spit I at over G 3.0g
    But me calculate Cl manuever= ~0.8..0.85*Clmax


    Its data from book "Aircraft constuction in USSR" but now i not this book
    (try ask badger mb he have this book in jpg format)
    But have other data NII VVS for captured Bf.109G-2
    Flying weigth 2935,4kg !!!
    http://www.bf109.ru/me109w.htm
     
  17. HoHun

    HoHun FH Beta Tester

    Joined:
    Sep 22, 2001
    Messages:
    2,643
    Hi Hammer,

    >But me calculate Cl manuever= ~0.8..0.85*Clmax

    Ah, this is a misunderstanding.

    Clmax is a function of speed and thrust:

    Clmax = f (v, thrust)

    Clman is one specific Clmax value:

    Clman = Clmax (1 G stall speed, 0% thrust)

    The rule of thumb is:

    Clmax (1 G stall speed, 0% thrust) = ~ 0.85 * Clmax (1 G stall speed, 100% thrust)

    But:

    Clmax (1 G stall speed, 0% thrust) = ~ Clmax (3 G stall speed, 100% thrust)

    The reason: The effect of propeller backwash decreases with increasing speed.

    Clmax (v1, 100% thrust) > Clmax (v2, 100% thrust) for v1 < v2

    >]http://www.bf109.ru/me109w.htm

    Thanks, I'll try otto translation ;-)

    Regards,

    Henning (HoHun)
     
  18. HoHun

    HoHun FH Beta Tester

    Joined:
    Sep 22, 2001
    Messages:
    2,643
    Hi Hammer,

    > Its data from book "Aircraft constuction in USSR" but now i not this book
    >(try ask badger mb he have this book in jpg format)

    The reason I was asking:

    Turn time Bf 109G-2 according to Pic. 26: ca. 23 s

    (G/S)/Vmax according to Pic. 26: 0.39 (kg/m^2)/km/h

    That means G = 0.39 (kg/m^2)/km/h * Vmax * S

    Vmax = 525 km/h (Pic. 27), S = 16.16 m^2

    G = 0.39 * 525 * 16.16 kg = 3309 kg.

    From http://www.bf109.ru/me109w.htm

    "Причем в полную нагрузку включена лишь одна пушка, стреляющая через редуктор, так как самолет, подвергавшийся взвешиванию был в варианте без двух крыльевых пушек."

    Otto translation says ~ "The weight is for a single-cannon aircraft."

    My suspicion: Ca. 23 s for 360° is for the heavy Bf 109G-2/R6.

    That makes sense with regard to relativity to Fw 190A-5 data:

    G = 0.43 * 510 * 18.3 kg = 4013 kg.

    So the method works.

    What Clmax do you get for the Bf 109G-2 using 3309 kg?

    Regards,

    Henning (HoHun)
     
  19. PressLuftHammer

    PressLuftHammer FH Beta Tester

    Joined:
    Mar 5, 2003
    Messages:
    13,933
    Location:
    Ekaterinburg (Russia)
    Aircraft have only one cannon, its test weigth of variant aircraft without under wings cannon
    (not Bf.109G-2/R6 )

    Its right for sustained turn at alt=1000m.


    That makes sense with regard to relativity to Fw 190A-5 data:

    G = 0.43 * 510 * 18.3 kg = 4013 kg.


    R=290m
    t=20 sec

    Calculate speed
    v=R*2*Pi/t=91,11m/s
    a=V^2/R=28,62m/s^2=2,918 g
    full over G=(a^2+1)^0.5=3,084 g

    calculate Cl man
    wing squer S=16,1m^2
    air for alt 1000m q=1,1116
    weigth variant 1 m=3023kg
    variant 2 m=2935,4kg
    variant 3 m=3309 kg

    Cl man =(2*m*g* overG) /(q*S*V^2)
    variant 1 Cl man=1,23 Clmax=1,447
    variant 2 Cl man=1,196 Clmax=1,407
    variant 3 Cl man=1,348 Clmax=1,586

    IMHO variant 3 not real for radius 290m and time 20 sec
     
  20. PressLuftHammer

    PressLuftHammer FH Beta Tester

    Joined:
    Mar 5, 2003
    Messages:
    13,933
    Location:
    Ekaterinburg (Russia)
    U right, but turn speed for Bf.109G-2 highest Bf.109E-3
    imho 109G-2 320kmph vs 250 kmph for 109E-3.
    Hence Cl max for 109G-2 < Cl max 109E-3 too for Spit IX and Spit I