Flying Swallow

[Ivan]

Hello All,

I made another try with the camouflage pattern last night.
This time, I cheated a bit:
I could not find a suitable continuous pattern for both sides, so I just used the same pattern for both sides.

In doing so, I finally figured out what was causing the texture mismatch issues.
My process is to find a continuous nice looking camouflage pattern that is about 700 pixels wide, cut it into pieces and overlay masks and then rotate the new image to be used as a texture.

(Note that the aeroplane is 29.33 feet (8.940 meters) long at a mostly constant scale of 10.24 feet per 256 pixels which makes it 733.5 pixels in length. Note also that the Spinner does not share the same texture or scale as the rest so does not need to be included.)

With just a bunch of random looking splotches and no ability to see how things overlap and fit together until it gets to the simulator, it is basically a matter of working pretty much blind until the simulator starts.

The real mismatch problem turned out not to be a Typo. It could better be described as a "ClickO".
The division of the camouflage pattern worked fine.
The conversion to BMP format worked fine.
When I did the overlay of each mask, sometimes I would forget to accept the change before continuing the edit.

Since the next step was to do a 90 degree rotation, the overlayed mask was the only thing being rotated.
The camouflage pattern underneath did not rotate and as a result did not match anything else.
With random splotches, one pattern pretty much looks like the next, but with the cheat last night, the left and right side Fuselage camouflage had to look the same. It became obvious if it did not, so I eventually saw where I was messing up.

Another item worthy of note is that although I know that my texture mapping is around 1/2 pixel or 0.24 inch away from where it should be in places, it may not always make a difference that can be seen in the model.
It is not a matter of our eyes not being able to see the difference in such a small scale; it is more a matter of the model not being generated in a way that will show such small differences:

From what I remember of SCASM coding, each vertex of a textured polygon is mapped to a pixel on the texture. Thus if the texturing scale is quite large (Greater Distance per 256 pixel bitmap), the internal conversion from AF99 to SCASM may not do well if multiple vertices are closer together than the distance between pixels. That is one problem.
Consider what this means: If your specified shift does not move a vertex enough so that it maps to a different pixel, you get exactly the same SCASM code and model as before even though your very exact specification has changed.
The second issue is that SCASM actually works on a Metric scale internally.
I believe it is 1/512 Meter resolution for the typical scale we use for these models and those are the offsets that are used from the Center of Gravity of the model to determine the location of a vertex.
So, from Aircraft Factory 99. we get to design things on a 0.01 Foot (0.12 inch) grid that then gets fitted into a 0.0769 inch grid and sometimes things that should be evenly spaced by the numbers in AF99 don't end up so evenly spaced when converted.

Note that the Wing Fillets are textured in a single colour without any pattern at all.
Note also that the Supercharger Intake still needs to be textured.

- Ivan.

[aleatorylamp]

Hello Ivan,
It looks very realistic, and the spread is nicely uniform and balanced. The effort seems to have been quite worth while!

Your previous speckled pattern and also this one, are the two that in my opinion look the best on this plane.

I noticed on several original photographs that there seem to have been perhaps 4 or 5 different camo patterns, some of which look terribly botched, as if the crew had done a last-minute job themselves with spray cans just before covering the planes a bit with palm leaves!
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

I am fairly pleased with how the camouflage turned out.
I still have trouble with random patterns. It probably comes from my obsessive compulsive side which drives me to try to make things "exactly" as I think they should look. When there is no "exact" and no distinct "should look", I have difficulty because I can't really tell when I am done or where to improve things.

The Kawasaki Ki 61 was completed at the factory and painted with national insignia, IFF stripes, various stencils, and I believe they typically had a red star around the wing gun openings. That was it.
The appearance would be pretty much like the overall Gray / Natural Metal finish that I had when this painting exercise began.

Most Ki 61 would have been crudely painted in the field by whatever means the locals could come up with.
Sometimes the appearance was good. Sometimes it was a mess. Sometimes they masked around the factory paint. Sometimes they just painted around the factory paint in a very crude manner.
This crude painting method is probably why the canopy frames were never painted; it would take too much effort to mask around the canopy glass.
Some of the camouflage looked a lot like it was done with a broom or mop.

From what I have seen, the unit markings were generally VERY well painted as were additional decorations such as stripes and lightning bolts or kill markings and other personal emblems.

I am sure some of the personnel in the field masked and painted carefully around the insignia and the home defence aircraft such as from 244 Sentai tended to be painted very precisely.

I don't think my camouflage pattern is all that realistic looking but the look I was trying to get was that of the aircraft that were painted with lots of overlapping green stripes with a spray gun. There were some gray patches left over but they tend to be much smaller than what I have here. (No, I did not contradict myself. I don't think it is particularly realistic but I still like the appearance.)

My current task is to go back and edit the flight model to improve the handling characteristics.
By reputation this aircraft and its descendants were some of the nicest handling of the Japanese fighters and right now, this bird does NOT handle all that well.

An accelerated stall is absolutely vicious and a snap roll happens often without even trying. Low speed control is quite poor, and controls in general is not very precise.
This part of adjusting flight models is actually quite fun because it isn't just a matter of flying on autopilot and recording numbers.
As I mentioned in the past, my test is to see if I can fly Figure Eights through the base of the Eiffel Tower very easily. With my P-40s and FW 190A, this is very easy. With the Hien, it isn't easy at all but it should be.

The negative curves in the Power Coefficient Table should also be adjusted a bit in my opinion. You probably don't know this, but the ones in your Two-Pitch propeller probably make more sense than what I currently have in this AIR file.

- Ivan.

[aleatorylamp]

Hello Ivan,
OK, so that clarifies why there so many different colour-scheme qualities on these planes. The impression I was was getting was not totally off then!

I like your first speckled colour scheme best, but it would also be the most difficult pattern to match at the joints between two surfaces, and the second one seems to work better there. The second one also looks clean and business-like!

Interesting, the handling qualities you report for this aircraft. That would certainly be certainly one of its attractive qualities, apart from the superb looking lines. I hope you get the behaviour where you want it!

Cheers,
Aleatorylamp

[Ivan]

Hello All,

It has been a while because I had to do a LOT of reading to figure out what the standard markings for a Japanese Army Fighter should be.
There are apparently a LOT of rules and almost as many exceptions to those rules.

As noted earlier, the Camouflage pattern is much neater than it would normally be in the field which is where most of the aircraft were painted.
This COULD HAVE been done by some obsessive mechanics who spent way too much time masking off the factory markings before painting.

This particular aeroplane has had the national insignia on its Fuselage applied slightly larger and lower than was typical. The specification for this model was for the insignia to be 600 mm in diameter with a 75 mm white border if there was any border painted on at all.
On a light coloured aircraft, there would usually have been no border at all but the appearance is suggested by the masking before painting.

The standard factory overall finish was clear lacquer on upper surfaces and bare metal on the lower surfaces.
Some photographs appear to have the aircraft in overall light gray but I don't know if this was an effect of weathering on the lacquer or actual gray paint.

Most Ki 61 carried a white stripe on the Fuselage just ahead of the tail surfaces. This was the typical marking for a fighter aircraft, but some aircraft did not have the "combat stripe" at all or on occasion had it in other colours.
A multi coloured strip typically indicated other service roles such as test / experimental / training but there are also fighters carrying multi coloured stripes.

A wide white stripe would be painted ahead of the national insignia, if it were the Squadron Leader's aircraft.
Aircraft were generally shared between pilots but some were assigned to a particular pilot and would carry personal markings or emblems.

The Sentai emblem was typically painted on the Fin and Rudder and each Sentai (made up of 3 squadrons or Chutai) would typically have its own symbol though each Chutai within the unit would have the symbol in a different colour.

The biggest problem I ran into here was that although 10.24 feet / 256 Pixels is a very fine scale for Combat Flight Simulator, it does not allow very fine detail to be painted.
My original idea was to include a typical Japanese Chrysanthemum but when reduced down to the 30-35 Pixels available on the Fin, it more like a gray blur. A Plum Blossom (Ume) crest (Mon) was also considered and I am still working on that idea.
My children told me that the first versions looked more like a reel of movie film!

The emblems for the 19th Sentai and 68th Sentai were fairly simple so I just used those symbols for now.
The 244th Sentai markings with Red or Blue Tails are the typical markings seen on artwork depicting the Ki 61 so I am reluctant to go down the path of least originality.

Also included is a screenshot of my Macchi C.202 Folgore that was released a couple years back. My preference is for markings with the style typical of the particular air force but not representing any actual historical aircraft or unit. I do not believe the Squadriglia emblem on the Folgore was ever carried by an actual fighter.

- Ivan.

[Ivan]

I decided to give a try at the path of least originality just to see how difficult it was.
(It turned out to be pretty simple.)

As usual, the most difficult part was in drawing the 244 Sentai emblem.
There appear to be two little yellow patterns on top of the white flash.
The lower pattern is obviously a yellow 5 point star, but I can't really tell what the upper pattern is supposed to be.
What is drawn here is just a "best guess" at what I believe I am seeing.I

Attached are screenshots of the Red and Blue Tail versions.
I simply do not like the "White Bandage" stripes under the national insignia that were typically worn by Home Defence aeroplanes, so I did not put those on any of these paint jobs.
Note that there were also aircraft with just the 244 Sentai emblem over camouflage and others with the emblem over gray or NMF.

I also made a lot of tries with the Chrysanthemum because it was a part of the insignia used by many different units.
I was actually correct in my initial statement that I simply could not do it in 30-35 Pixels, so I tried for 40 pixels by first creating the image double sized and then using GIMP to scale the image down.

As can be seen from Kiku 1, the result was not so good.
The blurry center is something I didn't like but could deal with if I had to.
The big problem was that the edges were somewhat inconsistent and looked pretty bad when pasted over whatever was underneath.
It looked like it might have been done by a painter who was intoxicated. (....And No, I don't drink. ;-)
Often, working in a larger size and then reducing the image softens and blends the separations and does a pretty fair job of anti-aliasing but in this case, it did not turn out well at all.

After a few more tries, I decided to try drawing the symbol as a 39 x 39 Pixel image using MS Paint.
The result still has problems but looks good enough to use.
Note that the petals at 45 degrees are slightly too long but if I moved them by one pixel, they would be slightly too short....
The image is shown here as Kiku 2.

During the experiments with getting a proper Chrysanthemum, I also took a look back at what I had done with a Cherry Blossom on my Ohka 11 piloted bomb. It was a small image but looked pretty good.
As I poked around a bit, I found that the Cherry Blossom was actually used as the insignia for 45 Sentai (Bomber Regiment) which flew the Ki 48 twin engine bomber.

The Japanese Army actually used quite a few very attractive Sentai insignia, but very often these insignia are associated with Sentai in other than Fighter roles.

- Ivan.

[Ivan]

Attached are a couple screenshots of a Chrysanthemum emblem on the Ki 61.
I still can't decide what the marking behind the Chrysanthemum should be.
Perhaps a single ribbon or banner? Perhaps a Lightning Bolt?
I really should save off a few of these texture sets in case I might want to include them in the release.

Yesterday, I started the Ki 61 for better handling and maneuverability.
The idea is to improve the controllability without changing the measureable straight line performance in any way.

About a week ago, I confirmed that the zero fuel weight in the AIR file was correct.
Fuel quantity and arrangement was also checked but I am pretty sure the numbers I have are off by around 15 Gallons or so.
I don't happen to know if the Ki 61 was like many other Japanese fighters and used continuous Methanol anti detonant when running past cruise power. If so then the AIR file weight will change a bit but will be made up by the weight of Methanol.

I also checked the DP file ammunition weights which were correct.
Moments of Inertia were also within reasonable range of calculated values.

Unfortunately the firing rates of the guns was not correct.

The Ki 61-I Tei (d) had an extended nose section to allow the mounting of a pair of Ho-5 20 mm cannon in the cowl.
The free firing rate of these guns was 850 Rounds Per Minute.
By my understanding, a synchronized cowl gun would typically lose 15-20% of its rate of fire, so the Ho-5's firing rate was reduced to between 700 and 725 Rounds Per Minute.

The wing guns were a pair of Ho-103 12.7 mm guns firing explosive shells. They retain their normal 900 RPM free firing rate.

The first actual AIR file adjustment was to the Control Response records (341, 342, 343).
The result was amazing. Lining up for the base of the Eiffel became fairly easy as did quick aborts when things did not quite line up.
It was quite possible to fly Figure 8s through the base though I did not actually try.
The directional stability was still a bit too high and ruined a few passes.

Two crashes showed where there were still problems.
One issue was the loss of Elevator control at moderate to high speeds which meant that I could not pull out of a low altitude loop.
The second issue was shown when the aeroplane snap rolled as a result of an accelerated stall.

Tonight was spent making a few tools so I can compare some graphs in the AIR file.
There is still more tuning to be done.

- Ivan.

[aleatorylamp]

Hello Ivan,
Your artwork is certainly looking very good. The markings are very attractive too, and will allow for more than one upload, I´m sure!

I´m glad you are progressing with the .air file, and that the model´s behaviour is fitting your expectations more closely.

Interesting, that you mention Control response Records 341, 342 and 343. I have always wondered about them, but have never more than glanced at these graphs, without daring to play around with them, as my knowledge on detailed aircraft behaviour has never been more than a general impression.

Your comments seem to indicate they could be useful to regulate manoueverability in extreme conditions, which sounds exciting! Perhaps I´ll experiment with them a bit to see how they work. I´ve just put it on my To-Do List!

Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

I am still not anywhere near done with adjusting the handling.
I had actually gone a lot further than I just described, but there is at least one factor that I have not yet pinned down that seems to limiting the amount of control force that can be applied. I have a pretty good suspicion but am not sure how I should handle it to be consistent though.

By reducing the Directional Stability and reducing (!) the Rudder control, it is now much less difficult to hold the aeroplane straight on the runway even though I have done nothing to affect Engine Torque or P-Factor.

As an analogy, consider how difficult a time a swordsman would have with a blade that has been tied in a knot with the tip pointing in an odd direction. The weapon is certainly dangerous but not intuitive to use. I am doing the equivalent of trying to re-equip with a straight bladed sword of the same length. They may be the same weight and have the same reach, but one is intuitive to use and one is not.

The really surprising thing about this tuning is that I have done absolutely NOTHING that should affect the stall characteristics of the aeroplane. It still has a very sudden and vicious stall, but it is so much easier to hold it on the edge of a stall that it is not so bothersome any more. (I know the sudden wing drop and loss of control has not gone away because of the low altitude snap roll and crash when playing around the Eiffel Tower.)

There is still a lot more to fix before I can consider this project to be complete.

- Ivan.

[Ivan]

Hello All,

I believe I am finally done with tuning the handling of the Ki 61-I.... At least for the first pass.
I had a pretty good idea of what I was trying to accomplish but am still a bit surprised at how well things turned out.
I will be leaving both versions of the AIR file in the release in case anyone is interested in doing a comparison.

The basic handling modifications should have absolutely no effect on the measurable performance that was documented earlier and yet the net effect is much more effective fighter that can be flown to its limits.

In checking out the rest of the AIR file, I found that the CL Graph had a slightly lower maximum Coefficient of Lift than I would have expected and made some adjustments.
These adjustments unfortunately DO change some performance numbers.
The slightly higher CL value should slightly lower the Stall Speed to about 90-95 MPH clean.
Climb Rate should also increase slightly but not to a measurable degree by the method I am using.
The adjustment to the CL Graph in theory should affect but not significantly change the Stall Characteristics.
A Stall still often leads to a Spin but it is now much easier to stay just at the edge of the stall before loss of control.

As mentioned earlier, flying through the base of the Eiffel Tower is now very easy.
Very low level flying is also very easy now. The only problem is that with CFS, there is not enough ground detail to judge altitude very precisely.

The next step in development is to program a few gauges for testing and at least one for the actual panel.

- Ivan.

[aleatorylamp]

Hello Ivan,
That´s good news, and nice screenshots too!
Cheers,
Aleatorylamp

[Ivan]

Some of the testing gets a little hard on equipment.
Fortunately, new Propellers and Engines are not that hard to get in the virtual world.
Testing Wheel Brakes and Scrape Points tends to get lots of Prop Strikes as does the very low level flying.

I have never quite figured out how to get the Scrape Points set in such a way that they line up with the 3D Model and still make the aeroplane sit properly.

A bit more testing and edits for handling were also done and the audio Stall Warning was enabled.
Now it is much more obvious when a low altitude stall causes a crash though to be useful, the stall warning should happen BEFORE the actual departure.

- Ivan.

[Ivan]

Hello All,

The last couple evenings have been spent working on a Manifold Pressure Gauge for the Ki 61.

Getting a clean image was not easy, but I believe I have sufficient information to program such a gauge now.
This gauge apparently was manufactured with many slight variations in the markings though the general appearance and colours were very similar. The Positive boost side was Red and the Negative side was either Black or Dark Gray.
The same instrument was used on many different aircraft of the Japanese Army but as usual, if the Army used it, the Navy did not.
This gauge was used on the:
Army Type 1 Fighter - Ki 43 Hayabusa (Oscar)
Army Type 2 Fighter - Ki 44 Shoki (Tojo)
Army Type 3 Fighter - Ki 61-I Hien (Tony)
Ki 45 Toryu Twin Engine Fighter (Nick)
Ki 46 Recon Aircraft (Dinah)
Ki 48 Twin Engine Bomber (Lily)
and probably others that I don't know about yet.
I came across images of these aircraft while searching for a clear image of the MP Gauge for the Ki 61.

Attached is an image of the instrument from the instrument panel of a Ki 46.

So far, I have finished the images for the Gauge Face and the Needle but have not yet done any programming.

- Ivan.

[Ivan]

The standard factory overall finish was clear lacquer on upper surfaces and bare metal on the lower surfaces.
Some photographs appear to have the aircraft in overall light gray but I don't know if this was an effect of weathering on the lacquer or actual gray paint.

Sometimes even information from books is not terribly reliable.
The source of information for the standard factory finish being clear lacquer was from the same book that seemed to give good information about the standard markings.
This information is disputed by a discussion at the J-Aircraft site which seems to make a lot more sense.
I will paraphrase some of it here and hopefully the previous sentence can be considered sufficient credit.
Some of the following is also my own interpretation, so any misinterpretation is mine.

Pre-war research in Japan came to the conclusion that ANY coating on a Natural Metal Finish would be better than none because the reflectivity of bare metal could be seen from great distances.
The problem with clear lacquer applied to aircraft exposed to the sun is that they would turn yellow in a very short time.
This by itself is not necessarily bad but does not seem to be what happened to aircraft in the field.
Sometimes aircraft were painted aluminum, sometimes they were painted gray. Basically any paint was better than none at least on the top surfaces. High reflectivity on the underside did not seem to matter as much.

So for now (Not that it matters much for CFS Textures), I will assume that the factory finish was an overall light gray.

- Ivan.

[Ivan]

A little while ago, I did some more checking of my numbers and found that I had made a slight error in calculations.
My original listing for ammunition load for the 20 mm cannon mounted on the cowl was 150 rounds per gun.
The correct ammunition load is actually 120 rounds per gun which I corrected in the DP file but I did not update the weight specification in the AIR file.
To maintain the correct loaded weights, 31 pounds needs to be added to the Zero Fuel Weight in the AIR file.
In addition, I decided that it probably makes sense to include the Aft Fuselage Fuel Tank since it is one of the distinguishing features of the Ki 61-Id.
The extra 95 Liter (25 Gallon) Fuel Tank would add another 150 pounds to the Take-Off weight.

With an extra 181 pounds more weight, performance is expected to drop slightly, so it is time for another round of tests.

- Ivan.

[aleatorylamp]

Hello Ivan,
I was a bit curious about possible effects, if any, of the 150 lb aft fuel tank.
Maybe it is a silly question, and would perhaps depend on whether this tank was intended to be used first or last - i.e. as reserve.

Would the added weight behind the CoG have to be compensated with an offset parameter, or is a slight tail-heaviness desirable until the fuel there is consumed? Of course if this were negligible, it could of course go ignored.

Cheers,
Aleatorylamp

[smilo]

granted, it's 03:15 and i'm in a bit of a fog.
but, if the original ammo count was 150 rounds per gun
and the corrected load is actually 120 rounds per gun,
wouldn't you need to subtract instead of add 31 pounds
to correct the loaded weights,
or am i missing something here?

okay, i'm going back to bed

[aleatorylamp]

Hello Smilo, hello Ivan,
If I understand the weight from the bullet count correctly,
the 31 lb from the rounds reduction deducted from the DP
file would have to be compensated in the total weight count,
so they would be added to the dry weight in the the .air file.

I don´t know if the Dp file gun position is also the position
of the ammo weight, and whether it affects the CoG. If it does,
depending on the gun positions (nose or wing - or both, as the
screenshot seems to show), this would be another factor that
could alter the CoG, as well as the 150 lb aft tank.

Cheers,
Aleatorylamp

[Ivan]

Hello Gentlemen,

Aleatorylamp is correct in his explanation of the DP file subtraction to be compensated for in the AIR File.
The problem here is that I already made the change to the DP file a long time ago and did not reflect the change in the AIR file because I did not make a corresponding change in my spreadsheet to calculate weight and everything still looked right.

Regarding the Aft Fuel Tank:
My original intent was to not put in the Fuel Tank at all because I was not sure about the volume and also because I do not have a proper fuel selector to let me access 4 tanks.
A few months ago, I found that my original estimate of the volume was actually correct and that the Aft Fuel Tank was connected to the Center Wing Tank and thus needed no extra selector.
In reality the actual selector is a bit more complicated but I have no ability to program mouse functions and thus can't build a correct fuel selector.

The "New" Fuel Tank is really just 95 liters greater capacity in the Center Wing Tank, so there is very little change in gravity.
This will also require some change to the Check List.

Regarding Fuel Tank locations and Center of Lift, I have an idea in mind about how things really work, but have not figured out a proper way to test my theory yet.

When I made these changes, I did a few quick flights and was surprised by how slow the Roll Rate was.
I will have get a stopwatch and go back to correct this.

- Ivan.

[Ivan]

Recently I found that the Zero Boost value for Japanese Engines was actually 760 mm Hg instead of the 750 mm Hg that I had been using. The discrepancy isn't much but I thought it was necessary to edit the AIR file to reflect the changes.

The effect is essentially increasing the Manifold Pressure limits by 10 mm (0.39 inch) Hg and then adjusting other factors to compensate so that aircraft performance is unchanged.

The first test was to observe the differences resulting in a simple increase in MP with no other changes.
At the 500 foot test altitude, the difference was not much: +10 HP.
Next came the obvious adjustments to Friction and then Torque.
I decided that the following test altitudes would be useful for comparison of performance changes:

Initial Test Settings were
38.97 inches Hg - 2400 RPM
500 feet........1046 HP............This is the baseline tuning Target
12500 feet....1153 HP.............This is slightly under the Engine Critical Altitude
15000 feet....1114 HP.............This is Aircraft Critical Altitude
25000 feet.....757 HP..............This number is just an intermediate point to confirm shape of the power curve
30000 feet.....611 HP..............This value is near but still under the Service Ceiling

The three numbers that are the most important are:
500 feet ----- This is where we determine Sea Level Speed.
15000 feet -- This is where we expect to achieve Maximum Level Speed.
30000 feet ---This determines Service Ceiling.

Once we have those three numbers matching the original values, the performance should also be pretty similar and not require any modification of other sections of the AIR file.

The first edit of just the Friction graph brought the power output for 500 feet and 12500 feet very near the target values, but as noted in the Engine Tuning Tutorial, the altitude performance fell off sharply.

Next was an adjustment to Engine Torque which brought the power down very significantly and needed to be compensated for by adjusting Friction downward by quite a bit.
The power output (1102 HP) at 15000 feet was still a bit lower than it should be although other numbers were very close.

A slight adjustment of the Supercharger Boost Gain from 2.25 to 2.27 gave a result that I believe was a better match

Final Test Settings were
39.37 inches Hg - 2400 RPM
500 feet........1048 HP............ + 2 HP is negligible for performance.
12500 feet....1154 HP............ + 1 HP
15000 feet....1115 HP............ + 1 HP
25000 feet.....761 HP............ + 4 HP
30000 feet.....616 HP............ + 5 HP

- Ivan.

[Ivan]

In doing my basic research for the Ki 61-Id, I had not looked much at what was done with prior versions of this aircraft in service use. I was more interested in the aircraft models as they came from the factory.
The Ki 61-Id was lengthened to provide space in the fuselage to mount a pair of 20 mm Ho-5 cannon.
It also carried substantially more armour than prior versions and came with an Aft Fuselage Fuel Tank as standard.

The Ki 61-I in all versions was somewhat under powered. With prior versions, often a fair amount of the armour was removed in service use to lighten the aircraft for better performance especially at altitude.
Some units also chose to remove the Aft Fuel Tank because its use moved the aircraft Center of Gravity too far aft and was believed to be the cause of many accidents.
This was my original reasoning (and the fact that there was no proper fuel selector) for leaving out the Aft Fuel Tank. The capacity of this tank in Ki 61-Id was only 95 Liters but was 200 Liters in earlier versions that were equipped with the Aft Fuel Tank.

- Ivan.

[aleatorylamp]

Hello Ivan,
Interesting adjustments and corrections.
It´s good when the numbers get closer to what reliable specs say, and with the +10 Hp improvement at S.L., it also improves at the ceiling.

Unless my maths is bad, a 95 litre tank (150 lb) only made approximately 20 minutes´ difference,
so the increased performance without it (and of course with reduced armour plating) must have been welcome.

It appears that one of these, armed with the 20 or 30 mm cannon, was the only Japanese machine that could down a B-29.

A very interesting plane!
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

If I had done nothing but to adjust the Manifold Pressure limits, the result would have been a 10 HP increase at Sea Level and probably a bit less at altitude. My goal was to match the previous power outputs as close as possible so the end result is only a 2 HP increase at Sea Level (really 500 feet).
The important thing was to have as close to the same power at around 15000 feet as possible so that the maximum speed would remain the same. Depending on the source, the altitude for maximum speed varies from about 13,800 feet to 16,400 feet.

The Ki 61-Id was the only version able to mount the domestic Ho-5 20 mm cannon in the fuselage and that is why I picked it to build. A few (under 400) Ki 61-Ic were armed with German MG 151/20 cannons in their wings but once that supply of imported guns was used up, there were no more coming.

From what I have been reading recently, it appears that many of the bomber interceptors were quite heavily modified to be able to effectively intercept the B-29 and some had their armament removed for ramming attacks. There is apparently quite a lot more to learn about this project that is "almost done".

- Ivan.

[aleatorylamp]

Hello Ivan,
As always, there is much more information than what one gets to see when one first
starts looking!

How sinister - ramming attacks! Not exactly Kamikaze, but being rammed is the most
gruelling way of getting eliminated, I think.

Desperate moves towards the end of the war, I suppose.
I hate how you get rammed in CFS1 Quick Combat!

The Germans also tried it as a last resort, to stop the B17´s, but only had limited
success, and at a very high cost, so they soon gave up. All the fighters involved and
most of the pilots, despite bailing out, were lost, and one or two of the rammed bombers
even managed to limp home.

Anyway, Ki61-Id looks and sounds like a great model notwhithstanding!
Cheers,
Aleatorylamp

[Ivan]

After updates to the AIR file, a new test of Climb Rates seemed appropriate.
The test is conducted with 50% internal fuel and full ammunition.
The total useable fuel quantity (from gauges) is 155 Gallons, so performance tests will be attempted with as close to 77.5 Gallons of fuel as possible.

For this test, I attempted to start at as low altitude as possible (about 200 feet) and take a measurement as 1500 feet altitude was reached. Note that with a climb rate of around 3000 feet per minute, taking a measurement at exactly 1500 feet is rather difficult.

Climb Rates at "1500 feet":
TAS..............Climb Rate
152 MPH.......2600 feet/minute
163 MPH.......2700 feet/minute
172 MPH.......2850 feet/minute (Above 2800 but slightly below 2900)
182 MPH.......2800 feet/minute

Note that the only significant change from earlier tests was the increase in aircraft weight but earlier tests showed a much higher airspeed for best climb. There seems to be a slight drop in climb rate above 180 MPH but it increases again by 200 MPH. This appears to be an effect of the Propeller Tables yet again.

202 MPH......2800 feet/minute

Best climb appears to be at 165-170 MPH IAS as compared to 195 MPH IAS from earlier tests.
For the Service Ceiling test I used 165 MPH IAS.

The Service Ceiling test appeared to be very repeatable but also depended quite a bit on the Fuel Load.
As noted earlier, the tests were intended to be conducted with 50% fuel (77.5 Gallons).

The first test was started a bit low and ended at 36,600 feet with 72 Gallons of fuel.
I believed that this test should be repeated with a bit more fuel, so....

36.300 feet -- 460 HP -- 78.7 Gallons -- 302 MPH TAS which is 165 MPH IAS
36,100 feet -- 463 HP -- 78.9 Gallons -- 303 MPH TAS

These results seem fairly close, so 36,100 feet will be recorded as the Service Ceiling.

- Ivan.