Flying Swallow
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  1. #1

    Flying Swallow

    These are my first tries through the Paint Hangar with this aeroplane.
    My son Michael says he likes the smaller pattern better.
    I am not quite satisfied with either one. I think the pattern should be somewhere in between.


    - Ivan.

  2. #2
    SOH Staff
    Join Date
    Jul 2005
    State of Confusion..... -8GMT
    i'm with you,
    trust your instincts.
    then, let us see the results.
    sometimes the magic works.
    sometimes it doesn't.

  3. #3
    Redding Army Airfield Allen's Avatar
    Join Date
    Dec 2007
    O85 Benton Field Airport
    The large print look too far apart. (Too much sliver)
    "Let Being Helpful Be More Important Than Being Right!" Some SOH Founder.

  4. #4
    The reality is that most of these aircraft came in plain natural metal finish from the factory and the "Camouflage" was applied in the field in whatever pattern seemed appropriate. There are zillions of variations. Some are mostly Olive / Dark Green. Some only have a couple Green splashes of paint. Not sure which one I like better yet.

    Other than muzzles for the wing guns, this model was finished back in 2005. The camouflage has been the hangup since then.

    This aeroplane project is getting attention because of a recent article I found in "Flight Journal" magazine while grocery shopping at Wegmans. There is a place called the "Fighter Factory" down in Virginia Beach that is trying to restore one. That alone would not have changed much....

    In the article was a description of the flight characteristics of the aeroplane which was something I had never seen before. The aircraft tested was a Ki-61-I "Koh" or Ki-61-1a in Western notation. (The Japanese used the suffixes "Koh", "Otsu", "Hei", "Tei" as we do A, B, C, D for minor modifications.) I also found in a forum discussion that my original name for my model was incorrect. Apparently a Ki-61-I-KAI c never really existed. KAI is short for "Kaizo" or "modified" and is the designation used when there is a major modification to the airframe: Thus N1K1-J Shiden and N1K2-J Shiden-KAI. So this version even with major airframe modifications was really designated Ki-61-Id.

    A flight report and some additional information meant that I had to rename the project and edit the SCASM code as well.... And since I was in the SCASM code, I figured I would add an interior Canopy Frame.... and since I wanted this aeroplane to fly as closely as possible to that described in the flight report, I got back into the Flight Model....

    I also found that the locations and volumes of the Fuel Tanks was not correct, so that resulted in yet more modifications. The DP file also needed updated for weights and for firepower. It should also get a change for the large quantities of armour that I found were installed in this bird.

    A month later, everything that I can think of is up to my current standards with the exception of the camouflage.... I'm working on that now, so we shall see where that will lead.

    There are many, many surprising things about this aircraft.

    - Ivan.

  5. #5
    Quote Originally Posted by Ivan View Post
    A month later, everything that I can think of is up to my current standards with the exception of the camouflage.... I'm working on that now, so we shall see where that will lead.

    There are many, many surprising things about this aircraft.
    Now almost 4 years later, this project is no longer up to current standards.
    Technology and standards advance rapidly during wartime.

    The 3D model is still pretty much up to current standards though the camouflage still has not been done.

    The AIR File is now leaves quite a lot of room for improvement and much of this is due to better information that I now have available.
    The additional information also makes some decisions necessary because of differences between reality and how things are implemented in a simulator.

    The original flight model (Version 0.57 from July 20, 2013) was built with the assumption that the engine parameters were fairly close to the Daimler Benz DB 601Aa which was the export version of the same engine used on the Me 109E but with some improvements in boost.
    This engine was license built by both Aichi and Kawasaki for their own aircraft.
    Kawasaki had made "improvements" in their design. Unfortunately, their engine (the Ha-40) was never reliable or durable.

    The Version 0.55 flight model had a maximum Manifold Pressure of 44.5 inches Hg (as from the Me 109E) but with 2500 RPM.
    The Version 0.57 flight model had a maximum Manifold Pressure of 45.9 inches Hg and a maximum of 2500 RPM.

    The actual performance is as follows:

    Take Off
    1160 HP @ 2500 RPM with 330 mm Boost --> 45.52 inches Hg

    Normal Maximum
    1100 HP @ 2400 RPM with 240 mm Boost --> 38.976 inches Hg at Sea Level
    1040 HP @ 2400 RPM with 240 mm Boost --> 38.976 inches Hg at 4200 Meters (13,780 feet) Altitude.

    The DB 601Aa export engine had a bit higher power at low level and allowed higher RPM for Take-Off but had a bit less supercharger and thus less performance at altitude.

    The problem here is that in CFS, War Emergency Power only affects Manifold Pressure. It does not change RPM limits, so should we allow 2500 RPM as maximum or 2400 RPM? Also, should we allow a maximum boost of 330 mm or 240 mm? There is no additional power adder required to run at the higher boost; It appears to be an engine durability limit.

    One other bit of information (and the reason why this thread is worthy of an update) was a pilot report that complained that the engine did not reach a full 2500 RPM until well after take-off and the aeroplane had reached 120 MPH airspeed.
    My Version 0.57 Flight Model was only able to reach 2500 RPM at 150 MPH to 160 MPH which meant that my propeller (stock P51D) was not a good fit. The general performance was otherwise pretty good, so it was left to the next update.

    A few weeks later (still in 2013) I tried to generate some new propeller tables for this aeroplane.
    The results were quite amusing: The aeroplane would accelerate quite well initially on the take-off run until it reached 45 MPH at which point it would stop accelerating. At that point, I stopped because I clearly had no idea what I was doing.

    A few weeks ago during Spring Break, my family traveled to do a couple more college visits.
    After dinner one evening, my son wanted to try something on the Internet and we had not brought any laptop computers along, so we both went down to the public computers at the hotel.
    While he was poking around, I decided to try to work on a function that would generate the kind of graph I would need for a Propeller Efficiency Table (Record 511).
    It turned out to be fairly easy, I just saved a few notes for later use.

    A few days ago, I finally finished working on a set of Propeller Tables (511 & 512) that allow the Ki 61-I to reach 2500 RPM just as the aeroplane reaches 120 MPH. The process was actually much more convoluted but those details deserve their own thread.
    Quite a bit more tuning needs to be done, but at least one significant fault has been corrected.

    - Ivan.
    Attached Thumbnails Attached Thumbnails Kawasaki_Ha-40.jpg   Ki61-Id.jpg  
    Last edited by Ivan; May 3rd, 2017 at 13:54. Reason: Add Some Decoration

  6. #6

    Short History

    Aichi and Kawasaki both license-built the Daimler Benz DB 601 engine.
    Kawasaki designed a heavyweight and a lightweight fighter, the Ki 60 and Ki 61, to use their engine.
    The heavyweight was intended to be the faster and more heavily armed aircraft but as the pair was developed, it was found that there was very little difference in performance between the two and that the lightweight was actually faster. The heavyweight Ki 60 was discontinued.
    The first flight of the Ki 61 was in December 1941 and a prototype actually tried to intercept the Doolittle Raid.
    The Ki 61 was not a particularly fast aeroplane especially at low altitude, so the raiders probably never knew anyone was following them.

    The design of the Ki 61, known as the Hien (Flying Swallow), was considerably different from other Japanese aircraft. It carried a significant amount of armour and was quite strongly built. Its faults were that the armament was fairly light for the time (1943) and that its engine was unreliable and lacked power. A relatively heavy airframe with very little engine power did not make for great performance.

    Germany supplied 400 20 mm MG 151/20 cannon to Japan via submarine and these were installed as wing armament on 200 Ki 61 fighters. This gave them a reasonable amount of hitting power but obviously was not a long-term solution.

    A significant redesign was made to the airframe of the Ki 61 to simplify the tail structure which also resulted in a fixed tail wheel replacing the earlier retractable version and stretched the nose section to make extra room for the ammunition boxes for a pair of 20 mm Ho-5 cannon.
    This was the kind of structural change typically noted by a Kaizo (KAI) designation change, but in this case, the eventual designation was just a change from c to d suffix (Ki 61-Id) which is the subject of this design.

    Flight performance data for the Ki 61-I series is available but most tests are of early versions. As noted earlier, engine reliability was very poor and the aircraft used for the test report I found most recently was only flown three times before it was grounded by engine failure. Late in the war when these flight evaluation were made, it probably didn't make sense to put much effort into testing an aeroplane that even at its best would only have matched technology in the ETO from about 1942.

    Maximum level speed ranged from 348 MPH to 368 MPH depending on the source but this was at a relatively low power setting of 240 mm boost and 2400 RPM.
    One has to wonder how things might have changed if the engine were more reliable and able to achieve designed power levels.

    - Ivan.

  7. #7
    Initial Testing gave the following numbers:

    2400 RPM at 39.0 inches Hg
    500..............996 HP.......307 MPH

    2500 RPM @ 45.5 inches Hg gives 1155 HP

    Horsepower is very low at 2400 RPM at 500 feet but maximum speed is only about 3 mph lower than I want.
    Horsepower is slightly low at 15,000 feet at which we want to reach 368 MPH.
    The power curve generally looks good but the power at high altitude is much lower than we want.
    This aircraft was the most successful interceptor of the B-29 Superfortress over the Japanese homeland.
    It had pretty good altitude performance with a service ceiling that some sources list at 38,000 feet.

    The problem is that the power at 45.5 inches (+330 mm) Hg is only slightly lower than we want so we don't want to raise it by much.

    The first attempt was to adjust the Engine Torque (Record 508) up a bit below its maximum RPM.

    That got the following numbers:
    2400 RPM at 39.0 inches Hg
    500.............1009 HP.......309 MPH
    15000.........1145 HP.......373 MPH

    Power at 2500 RPM was unchanged but since there was no test earlier using the Take-Off rating at critical altitude, I decided to test it here to confirm that it did not give a radical performance boost
    The actual manifold pressure increase was pretty minimal but the 2500 RPM made a slight difference:

    15000.........1171 HP.......376 MPH

    From doing a few experiments using part throttle, I believe that 1100 HP @ 2400 RPM should give 368 MPH or so and that can be achieved by reducing manifold pressure at 15,000 feet by around 0.5 inch or so.

    The next step would be to Raise the Sea Level power slightly by reducing the Friction Loss (Record 509) and also
    reducing the Supercharger Boost in Record 505.

    - Ivan.

  8. #8


    Hello All,

    What I noticed this morning was that the actual manifold pressure I had set in the AIR File as a maximum was 42.52 inches Hg.
    This is the actual correct conversion for 330 mm Hg. My posts here with 45.52 inches Hg are incorrect.

    The Japanese used a base number of 750 mm as their "Zero Boost" value.
    The typical Standard Pressure at Sea Level is 760 mm.

    The equivalent readings using various nations' standards are:
    +330 mm - Japanese
    1080 mm - Russian
    1.46 ATA - German
    42.519 inches Hg - American
    +6.18 pounds - British.

    As one can see, the Ha-40 engine used a rather low maximum throttle setting and this was considered Take=Off power.

    A slight reduction to the Friction Loss (Record 509) along with some changes to the Torque / Efficiency curve (Record 508) gives

    (All Tests at 500 Feet Altitude)
    1043 HP @ 2400 RPM with 39.0 inches Hg giving 310 MPH which is about where I wanted it.
    1053 HP @ 2500 RPM with 39.0 inches Hg
    1161 HP @ 2400 RPM with 42.5 inches Hg
    1174 HP @ 2500 RPM with 42.5 inches Hg

    Note that the numbers are about 50 HP low at the normal maximum (39.0 inches Hg) throttle setting and about right at the Take-Off setting. Although it is possible to tune the values higher at 2400 RPM, it is not a good idea to do this because then one can run into the odd situation where the engine generates more power at 2400 RPM than at 2500 RPM.

    Besides, the numbers SHOULD be a bit low at Sea Level because of the way CFS implements Superchargers.
    (Power at Medium altitudes will be too high.)

    Next comes the tuning of Engine Output at altitude.

    - Ivan.

  9. #9
    The sources that give the maximum speed of the Ki 61-Id as 368 MPH vary a bit as to the altitude.
    The range goes from 15,800 feet to 16,405 feet.

    I also found it to be rather annoying to have to back the throttle down from 100% to about 91% to get down to 39.0 inches Hg for the normal maximum power setting. (It really should be 38.9 inches as stated earlier, but I have never been able to get that precise with the throttle.) With that in mind, I finally decided to use 39.0 inches Hg as the maximum Manifold Pressure and allow 42.5 inches Hg only as an Emergency Setting. It is set as Water / Methanol injection which gives a fairly generous 10 minute limit.

    To get to a "Reasonable" performance range, Supercharger Boost Gain in Record 505 was reduced from 2.35 to 2.24.
    This brought the critical altitude down from about 14,500 feet to 13,600 feet. This Supercharger setting is very sensitive.
    Speed at 15,000 feet using 2400 RPM is now 369 MPH.
    Speed at 16,000 feet using 2400 RPM is 367 MPH which is a couple MPH below where I wanted it, but with 2500 RPM at either altitude, the engine puts out about 15 HP more.
    Of course in real life, engine service life would suffer but we have expert mechanics and manufacturing quality in our world is perfect if we declare it to be....

    The Engine is putting out about 60 HP more than I was aiming for, but performance is such a good match that I prefer not to keep messing with the settings.
    If it were absolutely necessary to bring the engine power lower, the critical altitude would go down a bit and it would be necessary to adjust airframe drag and propeller efficiency to keep the speed where it should be.

    The obvious question here is: Why not just increase propeller efficiency in the range matching the speed at 15,000 feet or 16,000 feet?
    The problem with that idea is that the Propeller Efficiency Table (Record 511) is just a heavily modified version of the stock P51D and its peak efficiency is already a bit over 90%.

    At this point, I am fairly satisfied with the maximum level speed at altitude.
    Next comes testing and tuning Service Ceiling.

    - Ivan.
    Attached Thumbnails Attached Thumbnails Ki61-15000.jpg   Ki61-16000.jpg  

  10. #10

    Climb Rate Test

    Before testing for Service Ceiling, one has to test for maximum Climb Rate at lower altitudes.
    This is necessary to get a value for the indicated air speed at which the maximum climb rate is achieved.

    To do this test and get consistent results, I use autopilot set for a particular climb rate and see what airspeed corresponds with a vertical speed setting. This test does not tend to be very consistent for several reasons:
    1. The Autopilot only has settings in 100 feet / minute increments.
    2. The Engine power and thus Climb Rate varies considerably with altitude.
    3. The climb rate is generally fast enough that the altitude and thus engine power change faster than the airspeed becomes stable.

    To do this, I bring the aeroplane to the airspeed at which I expect the best climb rate and set the autopilot's vertical speed to where I expect it to be. In this case, it was at 200 MPH True Air Speed and 2800 fpm.
    On the first try, I was pretty close.
    Starting the climb at 500 feet, airspeed became stable at around 203 MPH at 5,000 feet and increased to 210 MPH at 10,000 feet.
    Decreasing the vertical speed to 2700 fpm left the aeroplane with enough surplus power to constantly accelerate through the test.
    Increasing the vertical speed to 2900 fpm caused speed to decrease.
    I also found that there was enough surplus power by 10,000 feet that vertical speed could be increased to 2900 fpm while maintaining airspeed.

    After the first test, the numbers looked pretty good, but then I realised that I had started this test with full fuel and for comparison purposes, I like to run the tests with 50% fuel. Changing the fuel load increased climb rates to 2900 fpm at 5,000 feet and 3000 fpm at 11,500 feet. Airspeed increased by 3-4 MPH as well.

    Converting these numbers to Indicated Air Speed gave about 195 MPH IAS at 5,000 feet and 180 MPH IAS from 10,000 feet to 12,000 feet.

    Conclusion: Sustained Climb Rate at 2400 RPM with normal maximum power is around 2900 fpm and increases to 3000 fpm its maximum. Best climb speed is around 180 MPH IAS which will be used for the Service Ceiling Test.

    - Ivan.
    Attached Thumbnails Attached Thumbnails Ki61-ClimbTest.jpg  

  11. #11

    Side Effects

    All of this Engine Tuning has had some unintended side effects.
    One of the primary reasons for editing the AIR file was that the Engine did not reach its maximum of 2500 RPM until well after take-off.
    Replacement of the propeller tables (primarily Record 512) got the Engine to reach 2500 RPM at 119 MPH which was fairly close to the target of 120 MPH.
    Changing the maximum non-WEP manifold pressure to +240 mm had a couple side effects.
    It is no longer intuitive to run WEP for Take-Off.
    With the slight increase in power (about 12 HP) for +330 mm boost, 2500 RPM is now achieved at 114 MPH.
    With only +240 mm boost (normal maximum), 2500 RPM is now reached at 143 MPH....

    It isn't hard to reset the propeller tables, but I am not sure it is worthwhile to change or even which direction to adjust the numbers.
    Both directions are arguable, but with that being the case, perhaps it is a better idea not to change things at all.

    - Ivan.
    Attached Thumbnails Attached Thumbnails Ki61-NewPropeller2.jpg   Ki61-TakeOff-NormalMaxRPM.jpg   Ki61-TakeOff-WEP-MaxRPM.jpg  

  12. #12

    Service Ceiling

    The Service Ceiling is the maximum altitude at which an aircraft can maintain at least a 100 feet /minute (30 meters / minute) climb rate at the indicated airspeed at which it achieves its maximum climb rate.
    Sometimes 500 fpm is used as the standard but for our purposes, we will be using 100 fpm.

    The Absolute Ceiling is usually quite a bit higher and occurs when the indicated airspeed of the aircraft drops to its stall speed.

    The idea here is to adjust the Engine Power at high altitude to raise (or lower) the Service Ceiling but without affecting performance at the critical altitude or below.
    The technique is described in the Engine Performance Tuning Tutorial which can be found here:

    The basic idea is this:
    Engine Output is determined by the Engine Torque / Efficiency curve described in Record 508 balanced by the Friction Loss curve described in Record 509. If the Efficiency is higher but Friction is also higher, the net output of the Engine is unchanged..... At least at Sea Level. (Actually this is generally true up to the Engine's Critical Altitude.)
    Above the Engine's Critical Altitude, Torque falls off but Friction does not, so if there was less Torque and less Friction, the Engine Output falls off more slowly.

    I prefer to work in True Airspeed to avoid confusion, so if the best climb rate is achieved at 180 MPH Indicated Airspeed, the aircraft needs to stay above the following airspeeds at each altitude:
    33,000 feet -- 312 MPH
    34,000 feet -- 317 MPH
    35,000 feet -- 323 MPH
    36,000 feet -- 330 MPH
    37,000 feet -- 336 MPH
    38,000 feet -- 343 MPH

    Engine Power (Current)
    2500 RPM (+240 mm)
    1053 HP @ 500 feet
    1121 HP @ 15,000 feet

    2400 RPM (+240 mm)
    1043 HP @ 500 feet
    1113 HP @ 15,000 feet
    1069 HP @ 16,000 feet

    The relevant values before tuning for Service Ceiling were:
    Record 508 - Engine Torque / Efficiency
    2200 RPM -- 0.62
    1500 RPM -- 0.59

    Record 509 - Per Cylinder Friction Loss
    3000 RPM -- 58


  13. #13

    Service Ceiling (continued)

    .......After a bunch of cycles adjusting and re-re-testing, etc.
    The adjusted Service Ceiling appears to be around 34,500 feet
    and Absolute Ceiling is around 38,200 feet.

    (See Attached Screenshots)

    Service Ceiling tests tend to be very sensitive to slight weight changes and tend to have a bit of scatter even if all conditions are the same.

    Engine Power (Updated)
    2500 RPM (+240 mm)
    1055 HP @ 500 feet-------------(+2)
    1122 HP @ 15,000 feet---------(+1)

    2400 RPM (+240 mm)
    1046 HP @ 500 feet------------(+3)
    1114 HP @ 15,000 feet--------(+1)
    1074 HP @ 16,000 feet--------(+5)

    The relevant values AFTER tuning for Service Ceiling were:
    Record 508 - Engine Torque / Efficiency
    2200 RPM -- 0.57
    1500 RPM -- 0.53

    Record 509 - Per Cylinder Friction Loss
    3000 RPM -- 28

    The Supercharger Boost also required a slight adjustment from 2.24 to 2.25.
    With these minimally changed engine power readings, I would not expect any significant change in performance but power and speed will be tested again at the full range of altitudes as was done in initial testing.

    - Ivan.
    Attached Thumbnails Attached Thumbnails Ki61-ServiceCeiling.jpg   Ki61-ServiceCeiling2.jpg   Ki61-AbsoluteCeiling.jpg  

  14. #14
    While the changes in Engine Power were very minor, it was still worthwhile to retest level speeds under various engine settings.

    At 500 Feet Altitude:
    39.0 inches Hg -- 1046 HP @ 2400 RPM -- 311 MPH

    (1 MPH faster for an additional 3 HP over the last test)

    At 15,000 Feet Altitude:
    37.1 inches Hg -- 1114 HP @ 2400 RPM -- 370 MPH

    (1 MPH faster for 1 HP extra)

    At 16,000 Feet Altitude:
    35.6 inches Hg --1074 HP @ 2400 RPM -- 369 MPH

    (2 MPH faster for 5 HP extra)

    The Climb Rate tests were not redone because a couple HP really is not noticeable when climb rate are only recorded within about 50 feet / minute.

    There was one rather strange situation which is easily explainable in the simulation world but has no equivalent in the physical world.

    At 500 Feet Altitude:
    39.0 inches Hg -- 1055 HP @ 2500 RPM -- 309 MPH with a 100 RPM increase and 9 HP more, the aeroplane goes 2 MPH SLOWER!!!
    Normally, the Engine Power curves are such that there is a greater increase in power with a 100 RPM increase.
    The DECREASE in RPM actually INCREASES the Advance Ratio (J).
    At 2500 RPM, J = 1.0 at 180 MPH.
    At 2400 RPM, J = 1.0 at 173 MPH.
    so for the same linear speed, the Advance Ratio is higher if RPM is lower.

    The effect of this is that for the 2400 RPM speed run, the Propeller Pitch is 35 degrees but at 2500 RPM, the Propeller Pitch drops to 34 degrees, so the Constant Speed mechanism is working as it should.
    The problem occurs because of Interpolation.
    In real life, there are an infinite number of curves between a pitch of 30 degrees and 35 degrees. On computers there is nothing between those two curves and all intermediate values are interpolated.
    (See attached Screenshot)

    All of the Propeller Efficiency (Record 511) Graphs will have this problem; It is only a matter of degree depending on where this happens in the graph. I was hoping to give this kind of explanation in a new propeller thread but it needs to be here as well for the discussion to make sense.
    Note that this is the first Propeller manufactured by Ivan's Propeller Workshop.

    - Ivan.
    Attached Thumbnails Attached Thumbnails Interpolation.jpg  

  15. #15

    Conflicting Data

    The sources that I have used for performance data agree in general but not so well in specifics.
    Sometimes it is a matter of different versions of the aircraft that were tested or the assumed condition of the aircraft.
    Sometimes the difference is not explainable.

    One of aircraft tested was the famous Cape Gloucester Ki 61-Ia (s/n 263).
    The aircraft was captured in UNSERVICEABLE condition and measured for dimensions, and "restored" to flying condition.
    It was tested for general straight line performance which is documented in the attached TAIC report and also in comparative trials against US Navy types. In general it fared poorly though it was a very early (about March 1943 production) aircraft and probably had the typical problems of any new aircraft type.

    Other sources of data were the "Famous Airplanes of the World" series, Maru Mechanic, the TED report comparing the Ki 61-I against USN fighters, various other books and discussions from the J-aircraft site and probably another dozen sources that I can't remember.

    Obvious differences between the TAIC report and the design subject are the following:
    The tested aircraft was a Ki 61-Ia and the design subject is a Ki 61-Id.
    The engine was the same in theory but the airframe was quite different as noted earlier.
    Armour Plate is noted only on the Radiator for the TAIC aircraft which does not agree with other sources especially those for the d model.
    The Nose was lengthened for Ho-5 20 mm cannon instead of Ho-103 12.7 mm cannon.
    The Tail construction was different as noted earlier. The construction was simplified and the retractable tail wheel was replaced.
    This -Koh (a) model had an aft Fuselage Fuel Tank that is not included in the subject -Tei (d) model.
    I do not know if all of the d models did not have a aft Fuselage Tank, but the drawing from Maru Mechanic clearly shows no fuel tank in that position. That would make a pretty significant difference in loaded weight.

    Note that the test aircraft was not serviceable when captured and was certainly not factory fresh. There were obviously no ready spare parts to bring the aircraft back to flying condition. Therefore the performance was probably not quite what the design was capable of achieving.
    Were the TAIC people willing to push an unfamiliar aircraft with an unknown service history to its limits knowing that it was sidelined for mechanical problems?
    Note also that the service ceiling numbers in the document are pretty close to my own flight model (which is not necessarily good).
    Note that the engine power is more in line with what my flight model is getting rather than the numbers I quoted from FAOTW.

    One other thing to consider is that Japanese aircraft performance numbers were typically not accurately stated.
    Often an early test speed was used even if the aircraft had been substantially improved, thus 361 MPH or 368 MPH was probably a MINIMUM expectation.
    The US practice for testing maximum speed was to use Emergency Power while the Japanese quoted speeds for Military Power.
    That might be a plausible explanation for why an aircraft in poor condition could still achieve very near the quoted maximum speeds for the type.

    ....So.... The question is where to go next. I believe the straight line performance numbers for this flight model are "reasonable" and probably a bit on the optimistic side for an aircraft in service conditions but of course we have superb mechanics working for us!
    When the TAIC report is taken into account, even the engine output is reasonably close and so far, none of the performance numbers are so far off as to be out of character for a well constructed and well maintained aircraft.

    Until I find better data, I will now focus on the general maneuverability and handling, additional cockpit gauges, and a paint scheme of some sort which is what started this thread years ago....

    - Ivan.
    Attached Thumbnails Attached Thumbnails TAIC 154A-1 Tony 1.jpg   TAIC 154A-2 Tony 1.jpg   TAIC 154A-3 Tony 1.jpg   TAIC 154A-4 Tony 1.jpg  

  16. #16
    Hello Ivan,
    I have been following your posts with great interest, and Iīm glad you are making progress on your Ki-61 - especially as you say it has the first CV propeller that your workshop has produced!
    Despite conflicting information, which is mostly inevitable and which I always find when preparing my models, it seems that with your reasoning to interpret the data, you are achieving a very good flight model.
    "Why make it simple if you can also make it complicated?"

  17. #17
    Hello Aleatorylamp,

    I am glad you are enjoying the thread. I figure there are probably about a half dozen people actually following it.

    Yes, this was the first propeller from Ivan's Prop Shop.
    There are lots of issues which I am finding which I have only hinted at here.
    You can see the Record 511 Efficiency Graph I am using.
    Compare it to the Stock P51D Graph and you will see a lot of the things I mentioned in your FW 200 Thread.
    You can also see an illustration of the "Interpolation Problem" which I described many times.
    It gets pretty bad at 32.5 degrees and at 37.5 degrees.

    I don't want to correct the situation at 32 degrees because it will raise the Sea Level speed and possibly push the best climb speed even higher than it is now. The Best Climb Speed at 180 MPH IAS is already higher than I would have liked; Ideally I would have wanted it down around 150 MPH or possibly 160 MPH and perhaps then the Service Ceiling would have been higher.

    Correction to History Comments:
    800 MG 151/20 cannon were delivered by the Germans. They were installed in 388 aircraft (obviously with a few spares).

    It is interesting to compare the performance of fighters using the DB 601A / DB 601Aa series of engines.
    The standard engine on the Messerschmitt 109E was the DB 601A.
    The critical altitude of the DB 601A was 4500 Meters.
    The Germans did not export the DB 601A. For Export aircraft / engines, they used the DB 601Aa engine.
    The critical altitude of the DB 601Aa was 3700 Meters.
    The DB 601Aa engines were "license-built" by Alfa Romeo of Italy, Aichi and Kawasaki of Japan.
    The Italians pretty much stuck with the original German design with very minor improvements.
    The Italian engines were apparently pretty comparable with the German originals but with a reputation for a bit better durability.
    The Japanese (Kawasaki) used the basic DB 601Aa design but made some "improvements" for their Ha-40.
    The maximum boost was increased very slightly but the critical altitude was increased to 4200 Meters which is almost as good as the original non-Export DB 601A.
    The engine was also lightened over the original.
    The reliability and durability however were much worse than the original design.
    The aircraft that was the test subject for the pilot report I found apparently was grounded after its third test flight because pieces of the engine's main bearings were found in the oil.

    Some German Messerschmitt 109E's were also equipped with the DB 601Aa instead of the DB 601A and thus make a good comparison the Macchi C.202 and Ki 61-I.

    Some numbers:
    Messerschmitt 109E------ 354 MPH ---- 34,000 Feet Service Ceiling
    Macchi C.202 --------------375 MPH ---- 37,000 Feet Service Ceiling
    Kawasaki Ki 61-I --------- 368 MPH ---- 38,000 Feet Service Ceiling

    On a different note, The Paint situation is coming along fairly well at least for what I have done thus far. The Wings and Stabilisers were easy because they do not need to be matched to anything. The Fuselage extends across about 5 or 6 different texture files so matching the patterns will not be fun.

    Incidentally, the scales I am using are:
    Fuselage --- 10.24 Feet over 256 Pixels
    Wings ------ 18.20 Feet over 256 Pixels
    Stabiliser -- 12.80 Feet over 256 Pixels
    Fin --------- 10.24 Feet over 256 Pixels

    The Wing Fillet is an odd size but will be worked at whatever scale necessary to blend patterns.
    It is amusing that from the Virtual Cockpit view, the Fuselage cannot be seen, so it look from there that nothing more needs to be done.

    - Ivan.
    Attached Thumbnails Attached Thumbnails Ki61-WingsPainted.jpg   Ki61-VCockpit.jpg  

  18. #18
    Hello Ivan,
    Meticulous work on the wing and tail textures - looking fantastic!
    "Why make it simple if you can also make it complicated?"

  19. #19
    Join Date
    Sep 2011
    St Simons Island GA
    Thanks for posting the results of your efforts. One of Japan's prettiest WWII fighters. Following with interest!

  20. #20
    Thanks Guys,

    I had actually hoped to do the full series of fighters from the Ki 61-I to Ki 61-II-KAI to the bubbletop Ki 61-II and finally the Ki 100 in both the -Ko and -Otsu versions. So far, I have not gotten past Part 1 of the series yet.

    I had originally not wanted to build the Ki 61 because it really is at best only an adequate fighter for its time, but it really was a beautiful aeroplane and I had never seen a really good CFS version out there. My combat flight testing of this aeroplane was against my own Spitfire Mk.IX with a stock flight model and I figure it has about a zero percent chance of winning such a fight. The stock Griffon-powered Spitfire Mk.IX has about double the engine power in an aircraft that is pretty near the same size and weight. (Yes, I did say "Stock Griffon-Powered".)

    From a tactical standpoint, I figure the Ki 61-I was equivalent to the pre-production Me 109F or about even with a Macchi C.202 which meant that by 1944 when the Ki 61-Id was introduced, it was outclassed. That is why I was hoping to get to its successor that never arrived, the Ki 61-II-KAI which was pretty much equivalent to Me 109G series.

    From a flight model standpoint, the issues to work with are these:
    Propeller Pitch Range is 27 - 47 degrees.
    The engine reaches full 2500 RPM at around 120 MPH.
    That means that it comes off its low pitch stop at around 120 MPH.
    At the moment, it is hitting best climb at around 180 MPH with around 30 degrees Propeller Pitch.
    The problem is that with the way CFS Propeller graphs are arranged, the 5 degree intervals (actual graphed angles) are the peaks and the areas between (2.5 degree intervals) are the valleys and it would take a lot of messing around to bring the airspeed for best climb down to 150-160 MPH where I think it should be.
    This kind of thing will be discussed further if I ever post a "Propeller" thread.

    The painting is coming along rather badly. I found that I had lost some detail with the method I am using and need to do a few things over again.

    Ivan's Paint Shop is not very qualified which is why so many project end up getting trapped there.

    - Ivan.
    Attached Thumbnails Attached Thumbnails Ki61-1d-WireFrame.jpg  

  21. #21
    Hello Ivan,

    From your comment on the Fw200 Condor thread, whose content has recently largely also been propellers, Iīm glad that you have managed to get a reasonably good working propeller for your Ki-61.

    Although the Ki-61 is on a different power level compared to the "Stock Griffon-Powered" Spitfire - i.e. the greatly souped-up Merlin (stock plane performances cheating again, are they?)..., at least this so-to-speak "bench test" proved that the propeller behaved very bravely, and seems to have achieved quite a congratulatable result - at least for now!

    "Why make it simple if you can also make it complicated?"

  22. #22
    Hello All,

    One of the most serious weaknesses I have had in putting together a CFS aircraft project is in texturing the model.
    The panel lines do not present any problems because they are generally pretty well defined.
    One has to choose which ones to represent and which to leave out, but after a while it gets to be fairly easy though tedious.

    The painting of convincing camouflage patterns has always been difficult for me. I suppose it has something to do with my refusal to accept anything that is not well defined even if it is SUPPOSED to be random.
    Another issue has been the matching of camouflage patterns over multiple pieces of the aeroplane as would usually happen on the Fuselage.
    Visually apparent differences in different areas of the aeroplane such as between the Wings and Fuselage also tend to bother me which is why all that appears on the model thus far for camouflage is Tail and Wings.

    To make the matching easier, I thought I would try to calculate the offsets to lay out a continuous pattern over multiple pieces.
    I believe the concept is sound and would make it easy to transfer a Profile Painting onto a suitable model.

    Attached is a screenshot from my first attempt which obviously failed in multiple aspects.
    In this case even the scale appears to be miscalculated.

    Time to go back and see where the process went wrong.

    - Ivan.
    Attached Thumbnails Attached Thumbnails AutomaticTextureLayout.jpg  

  23. #23
    Hello All,

    In checking through the process for generating textures, I actually didn't find anything wrong so the best guess is that I must have copied some numbers incorrectly. This is one of the reasons I want a more automated process: To take the greatest single source of errors (me) out of the loop whenever possible.

    Here is another attempt at automating the texture generation and it seems to have worked pretty well.
    The Port side is also shown with the numbers not reversed so that it is easier to see that they are in pretty good alignment and continuous.

    One of the things I found out when I starting looking at automatically generating texture files was that I had made a few mistakes when I was mapping textures to the model. Each Texture File is 256 x 256 pixels. The scale being used on this model is 10.24 feet over 256 Pixels which works out to 0.04 Feet per Pixel, so each Pixel covers an area of 0.48 x 0.48 inch. In places I could not tell visually but could tell once I had done the calculations that I was off by 0.02 feet (1/2 Pixel) which means that there is occasionally about a 1/4 inch misalignment between adjacent textures.
    Hopefully I will remember to correct this when any other updates are made to the model.

    Time to go back and see if I can get the camouflage texture looking the way I wanted.

    - Ivan.
    Attached Thumbnails Attached Thumbnails AutomaticTextureLayout2.jpg   AutomaticTextureLayout3.jpg  

  24. #24
    Hello Ivan,
    For someone so un-artistic as myself, textures are the worst part of modelling, and within textures, itīs camo patterns, and within those, the speckled ones, that include styles with intricate brocade or splinter patterns. They are also the most striking, though, and the model looks fantastic with them!

    You seem to have found a way to get the sizes to coincide on all surfaces, which I was never able to do very well. Then, hand-matching the edges on different sections on the same surface is tedious but possible, but when one surface is up/down and the other left/right, matching the pattern gets nightmarish.

    I found some photos of the Swallow where the seemingly hand-sprayed speckles were applied on the completed plane because the speckles, for example at the wing-root, flowed from the fuselage onto the wings, but other photos showed a distinct un-sprayed gap there, and in some cases the speckles on the wing were cut at the wing root, meaning either that the wing came from another plane, or that the speckles were applied before assembly. Plastic model kits also reflect both these things.

    So, if life gets too difficult matching different surfaces, there is a good, real way around, because speckles didnīt always flow over! But you must have noticed this already, so thereīs nothing new here...
    Good luck anyway.
    "Why make it simple if you can also make it complicated?"

  25. #25

    Another Paint Scheme

    Last Night I decided to try out a different approach to a camouflage scheme.
    The textures here are actually a heavily modified scan of a "Composition Notebook" back cover.
    The pattern seems to be quite appropriate though it gets to be a little sloppy around the Nose section.

    Unfortunately it breaks up the really pretty lines of the aeroplane though I suppose that is the point of camouflage.

    The Wing Roots can be used to merge the Fuselage and Wing patterns though in real life, the exhaust stains from the engine would have turned the Fillet area gray or black and hidden any camouflage pattern underneath, so whether or not the patterns match across the major assemblies would not matter much.

    As before, I am fairly satisfied with the Wings and Stabiliser but not so much with the Fuselage.
    Note that camouflage was never applied to the Canopy Frame.

    Time to figure out how to highlight the Katakana character on the Fuselage and design or pick some unit insignia....

    - Ivan.
    Attached Thumbnails Attached Thumbnails Ki61_Pattern2_1.jpg   Ki61_Pattern2_2.jpg   Ki61_Pattern2_3.jpg   Ki61_Pattern2_4.jpg  

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