Flying Swallow

[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]

More Flight Model Updates

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]

Modifications for Service Use

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]

Climb Rate Test Yet Again

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.

 

[Ivan]

Nervous Shake Test

Last night, I checked to see how much the trim for straight and level flight changed as a result of the weight increase.
It turns out there were a few surprising differences.

I set up a rather unusual test:
Very often on a CFS aircraft, if the balance on the landing gear, contact points, or spring rates are not in harmony, the aeroplane will vibrate or wiggle a little even when nothing is happening.
To test this, I leave the aeroplane loaded but inactive for a few hours and see if it has moved noticeably from where it started.
This aeroplane was left overnight and does not appear to have moved.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
Sit, Fido!! Good Dog... and all night!

Anyway, your thorough testing and fine-adjustments,
together with the intricate textures and excellent lines
this model shows, will surely make it a very successful
model in the warbirds library - not to mention the
performance!

Nice work!
Cheers,
Aleatorylamp

 

[Ivan]

Edits and Tests

I tried to do just one more edit in AF99 and got the result shown in the screenshots.
I do not believe it is the result of a broken Development Machine, but I also know that MdlDisAs did not work either and THAT is most certainly a misbehaving Development Computer.
I will try the SCASM (MdlDisAs) edit on another computer this evening and see if it works there.

On another somewhat related note, I also found that the Roll Rate was not quite what I expected it to be and Trim appears to be not quite stable.
I suppose it will be yet more editing on the AIR file.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
What ate up the camo?
Cheers,
Aleatorylamp

 

[Ivan]

A Retry....

Hello Aleatorylamp,

This morning I went back to do another build with AF99 so that I could see what the code changes were for the Alpha Transparency in the Canopy and be able to put them in manually via SCASM.
It turns out the build from AF99 worked today.
I have a minor suspicion there was an interaction between programs that might have been causing problems.
I have to help my Son with some of his school work tonight, so I probably will not get anything more done for a couple days.
Tomorrow looks to be pretty busy.

Regarding Camouflage:
You know it was all done in Water Colours, so it went away with the first rain or snow storm.
Actually, it was field applied camouflage and the new version is straight from the Aircraft Factory again.

Attached is a Screenshot to show what I was testing for earlier.
Note that for this Messerschmitt Bf 109E, it only took about 3 minutes for the aeroplane to fidget enough to get to this angle from the time it loaded into the simulator.

Can we all say "Fidget Spinner"?

- Ivan.