Conspicuous by Their Absence

[Ivan]

This project actually pre dates the A6M2 that was just released. Now that I have what I consider to be a pretty good AIR file for the A6M2 Model 21, I believe it can be modified easily for the later plane.

The two aircraft are more similar than they are different. Here is what I believe to be the differences between them:

The A6M2 - 21 carries 60 rounds per each 20 mm Type 99-1 Cannon. Each round weighs 8.206 ounces.
The A6M3 - 22 carries 100 rounds per each 20 mm Type 99-2 Cannon. Each round weighs 8.912 ounces.

The A6M2 Engine is a Nakajima NK1C Sakae 12 with 950 HP at take-off
The A6M3 Engine is a Nakajima NK1F Sakae 21 with 1130 HP at take-off
Tne newe engine is a bit heavier, has a compression ratio of 7.2 instead of 6.7, has a higher critical altitude and revs a bit higher. The reduction gear and propeller diameter are slightly different.

Because of the engine, The fuselage fuel tank is reduced from 145 to 60 liters. To compensate, additional fuel tanks were installed outboard of the cannon.

The new empty weight is calculated by the following method:
Normal loaded weight is 2678 kg or 5904 pounds.
This is assumed to be with full internal fuel of 588 liters and full ammunition (Hopefully this is correct) with no external stores.
5904 pounds = loaded weight
- 932 pounds of fuel
- 213.5 pounds of ammunition
- 35 pounds of oil (Roughly 1/3 of the 52 liters carried)
---------
4723.5 pounds

This number hopefully isn't far off because it will be used for the flight model.

To be Continued....
- Ivan.

[Ivan]

After plugging in the variables described in the last post, the time came for tuning.
In theory, there should not be much tuning involved since the two aircraft are so similar.

The only real differences that should affect performance are the following:
1. Engine Power and Propeller Diameter and Pitch Range
2. Weight increase
3. Revised cowling

There were many surprising results from just changing a few parameters.
First of all, the Propeller Pitch Range meant that full rpm isn't developed on the ground. 25-45 degrees in A6M2. 29-49 degrees in A6M3.
The increase of about 100 HP at Sea Level and 2500 meters in critical altitude should increase the maximum speed seriously.
The increase in engine power at Sea Level is well over 10%, but resulted in only about 1% speed increase.
Drag coefficient was increased to compensate for this. I was surprised. The A6M3 looks more streamlined.
The Weight increase of slightly less than 300 pounds basic weight and probably around 550 pounds loaded weight make this beast feel a LOT less agile.
The aircraft also has two small fuel tanks outboard of the cannons which I compensated for by increasing the size of the wing tanks and moving them outboard by around 2 feet each. The seems to have reduced the roll rate noticeably. Surprisingly, the rather poor high speed roll rate did not seem to change.

The best climb rate is also much improved which surprised me: The A6M2-21 best climb rate was 3400 fpm at 180 mph. The A6M3-22 best climb rate was 3700 fpm at 185 mph.

Still more tweaking to do.
- Ivan.

[Ivan]

A while back, we were discussing Aircraft Animator and its capabilities.
Here is an example of something that wasn't easy, but I believe can be handled reasonably well within the limits of Aircraft Animator

http://www.youtube.com/watch?v=A0OSL...ture=endscreen

http://www.youtube.com/watch?v=Lfo_9k_28n8

Modified downloads of my Wildcats can be found here:

http://www.thefreeflightsite.com/Ivans.htm

Hubbabubba, you and I discussed this animation sequence a little when I first released the Wildcats a few years back. These videos came up when I was just poking around and my son started getting interested. Pity though, he had to go back and do some practice math work and miss a "Proper" education.

- Ivan.

[No Dice]

"Pity though, he had to go back and do some practice math work and miss a "Proper" education."

I really think that is a statement coming from a great father, mothers simply do not understand. LOL

That proper math education may lead to our next and even better aircraft designer for CFS1, watch
out dad he may be on your heals...at least we all hope so.

He has some big shoes to fill though.

Luv your work, waiting on your next release.

Dave

[Ivan]

I believe my son understands now that there is a lot of education that doesn't come from school.
He is studying Greece and Rome at schopl. Over the last week, I have read to him about the life and death of Socrates, a little overview of Plato and his Academy and last night I started with part of a description of Aristotle. Perhaps this isn't quite in line with everything in school, but we are not that far off either. I don't know how good my analysis was, but at least he learned a few new words. The book I am reading from is way past the high school level and he is only in 5th grade.

Michael's comment when I finished the reading about Socrates and did a little interpretation of his "execution" was that Socrates was an idiot.

Knowing how to do the math correctly is good, but understanding when and how to use it is even better. At least that is my opinion and I am sticking by it.

In about a half hour or so, Anna Honey will be on a plane to Japan on yet another trip. I get to be the single parent again..... Not much fun, too much work.

- Ivan.

[No Dice]

Ivan, I know you don't drink....But if you buy the beer , I am more than willing to continue your childrens education on what you can and can not do
while mom is away. These things are important and can be applied to your first year in college even....beer pong, poker, toga parties...you know..the
important stuff. LOL

Good Luck Mr Mom......Call me if you should require my services.

Dave

[Ivan]

Thanks for the offer.

BTW, you are also showing your age: Majority of college students these days are underage for drinking. It changed when I was in college. There are also lots of other little events conspiring to make my single parenthood a bit more challenging.

Tomorrow evening, I need to figure out how to be in two places at once.

- Ivan.

[Ivan]

I really would like to get to grips with the Air File side of things as my frustration came to a head when I was developing my Vickers Vernon. Turning the beast was a nightmare and something I'm not proud of, it would sideslip at a rate that could result in a crash at a lower altitude. Even on autopilot it would start to stick its nose high into the air to try to get round.

Hello Womble55,

There is a good little discussion going in the Flight Dynamics area about information for building a flight model:
http://www.sim-outhouse.com/sohforum...-create-an-FDE

I tried out your Vickers Vernon. It feels like a huge and underpowered bomber which is what it looks like. What exactly do you want to change? The most obvious change I would make is to adjust the trim a touch nose up so that it doesn't keep trying to plant itself into the ground or ocean. I also believe your landing gear contact points are a bit off. Are you working off a pilot report of some kind that says it should behave a certain way?

Thanks.
- Ivan.

[womble55]

Hi Ivan,
As you noticed with the Vernon, it is a slow, lumbering beast and has amazed me how the full sized aircraft ever got off the ground. But get off the ground it did and with such reliability it was, and its close relations, used for a considerable time.

My beef is with the serious sideslip and lack of effective rudder, I dont want to be able to roll the blighter but a smooth bank and turn would be great. I dont want the instant response either, it has to be a bitch to fly with complete concentration required. Its not a Tigermoth, so it needs a degree of lethargy in its controls.

I haven't delved into the quirks of Air files and it is something I should investigate, but projects call.....

[Ivan]

I poked around on the Vernon yesterday. I noticed that you used a FS98 AIR file.
I don't know if you want to redo the AIR file, but if you do, I would suggest starting with a P-51D stock file.
There isn't a lot of flexibility with the FS98 AIR files.

- Ivan.

[womble55]

I had to chuckle when you mentioned using a P51D Air file as a starting point, stall turns, zoom climbs, fast roll rate, a very nimble bird. I didn't realise that there was so much difference between a FS98 and a CFS1 Air file. When I build a new aircraft I use an Air file of a similar aircraft already in my collection, I think I will have to be more selective in my donor aircraft in future. In fact I shall have to go through them all to find the best donors in each class and tag these as the only ones to use.

[Ivan]

Hello Womble55,

Way way back when I started building CFS aeroplanes, I figured that just about anything that ended up with the correct straight line performance and general handling was good enough.
I did want to have a supercharger available on my planes so that the critical altitude was higher than sea level, but tried to retain some of the easier FS98 records.
The end result wasn't pretty. I actually had one Hellcat AIR file that would slow down, wobble a bit and then flip and explode in an uncontrollable manner regardless of how gentle the touch down was.

After that, I looked at the various stock AIR files and decided to start with the stock P-51D.
I seem to remember that some of the other stock AIR files are missing some records that are in the P-51D.
I believe everything I have ever released is based on the P-51D, even the Fokker E.III Eindecker.
I have a Heinkel 177 and a B-25 in the works and even those are based on a stock P-51D.

A couple weeks back, I started making notes on necessary changes to the P-51D AIR file regardless of subject.
Although that AIR file is as complete as I have seen, it has a lot of garbage data with lots of unrealistic values.
I had already gotten pretty far with my flight model for the A6M2 when I found that there were a few stock values that I had forgotten to change and when changed, forced a re-test of everything I had already done.

Someone had it in their mind that the P-51D was to be the ultimate hot rod in the game and tweaked it accordingly.
As an example, the wing efficiency in record 1204 is in the low 5000s for most of the other stock aircraft but is in the 4000s for the P-51D. This means that the P-51D will bleed off less speed from induced drag such as in pulling a hard turn or in a low speed climb.

- Ivan.

[womble55]

Just to see what the difference was, I changed the air file on my Wellesley for a stock P51D one. Even though it is a tad too sensitive in all axis, the speeds are all wrong and the acceleration and deceleration are wrong....it flies much better. I will alter the weights, wing area, engine horse power and see what results. A thousand thanks for this tip and for all the others you present.

[Ivan]

Hello Womble55,

You're quite welcome! Glad you found the discussion useful.

There actually are a zillion more things to alter than what you mentioned.
If the aircraft is too sensitive, you can either change:
Control Factor
1101:112 for Ailerons
1101:142 for Elevators
1101:208 for Rudder
Damping
(also 1101 about two entries below the control factor)
Moments of Inertial
Record 1001

There are also a couple speed / control effectiveness graphs to mess with, but hopefully just messing with the above values will fix things enough. Besides, it isn't often that you can actually get data as to how the controls behave with increasing airspeed.

Another goofy thing is that what is labeled Indicated Air Speed (IAS) for a couple of the graphs isn't really IAS. It is really 1/2 Rho * V^2. See the discussiont at this link:

http://forum.lwdesigns.com.au/1-2-rh...eed-t1285.html

I attached an older copy of the FDE control file that shows how the variables are used by the "Flight Dynamics Editor" which is free from Abacus. I have more current copies, but everyone is in bed now and I don't want to go stomping around and wake up anyone.

Besides tuning Horsepower of your engine, you also want to change your Record 512 (Propeller Power Coefficient) to match your new engine / drivetrain. This basically matches the engine's torque after reduction gearing with how hard a propeller is to spin. If you get it wrong, the propeller pitch settings will be a bit off.
You can tell when this happens by finding that you can go a bit faster (better propeller efficiency) by adjusting propeller pitch angle / RPM.

I have a Engine Tuning tutorial in mind with examples, but you can get most of the discussion by looking at the FSX thread I listed earlier:

http://www.sim-outhouse.com/sohforum...-create-an-FDE

- Ivan.

[Ivan]

Hello Womble55,

A couple other things I forgot to mention:
A lot of things get simpler when you are working with something like the Vickers Vernon:
First of all you don't have a supercharger, so whatever method you use to determine engine power isn't nearly as important.
Next, you are using a fixed pitch propeller, so the Propeller Power Coefficient (Record 512) isn't as important because the simulator won't be trying to match propeller pitch with engine load.

With the Fokker Eindecker, I cheated like mad (because I really didn't know any better):
First, do the rest of your speed and power tuning with a constant speed propeller.
Next, take a propeller pitch angle reading under cruise / max speed conditions using Jerry Beckwith's very excellent test panel.
Once you have that pitch angle, set your propeller to fixed pitch with that value.
Do Test afterwards to make sure the lugging propeller and cruise or maximum speeds haven't changed.

I don't think this method would work with the Wellesley variable pitch propeller though.

(That beast seems awfully underpowered.)
Good Night.
- Ivan.

[smilo]

this is an interesting subject
that deserves it's own thread.
at least, then, it would be easier to find
for future reference.

it's something, i believe,
we would like to learn more about.
although, i have to admit, like OleBoy,
in the FX discussion;
"...areas pertaining to flight dynamics.
Generally, I just moved on.
I was over whelmed with it."

maybe, if it started with making basic changes
to a stock p-51d.air file for a very simple aircraft,
the process might be easier to understand
and, over all, not be quite so overwhelming.

i'd also be curious to know how hubba
modifies for his ships and the jeep.

just a thought....or two.

[Ivan]

Hello Guys,

I actually worked up a "Drive Model" for Hubbabubba's Jeep also.
It took a bit of effort, but did pretty much what I wanted it to do.
Each time I play with another project, I learn something new and that "Drive Model", which I believe Hubbabubba didn't use, taught me a bit about the lack of stability of a tail dragger landing gear.

One would think that a tricycle with the single wheel in front would have a greater tendency to tip when cornering, but

I believe I can pull off a pretty fair "Engine Tuning" tutorial for CFS, but don't know if I really know enough for a good Flight Model tutorial. I can pretty much accomplish what I set out to do in terms of performance and handling, but the methods are not necessarily technically the "Correct" way to do things.

- Ivan.

[smilo]

i. for one, would like to see
that " "Engine Tuning" tutorial for CFS"

of course, you have to know from the start
that there won't be a lot of comments,
but, i'm sure folks will read it.
that's just the way it is around here.

so, please, give it a go.

[hubbabubba]

Hello Guys,

I actually worked up a "Drive Model" for Hubbabubba's Jeep also.
It took a bit of effort, but did pretty much what I wanted it to do.
Each time I play with another project, I learn something new and that "Drive Model", which I believe Hubbabubba didn't use, taught me a bit about the lack of stability of a tail dragger landing gear.

(...)

- Ivan.

Any aircraft should use a CFS1-like AIR file, but land/sea vehicles...?

Last time I tried one of your AIR files for the jeep, Ivan, it was flying for miles once driven over a cliff.

Land vehicles and ships do pretty well on a FS98-like AIR file, as long as you do look for "driveability" (or "steerability") rather than specs.

BTW, smilo is right; this thread is turning into a "smörgåsbord".

Happy Easter guys!:naturesm:

[smilo]

...
BTW, smilo is right; this thread is turning into a "smörgåsbord".
Happy Easter guys!:naturesm:

that it is, but in it's defense,
subjects that are "conspicuous in their absence"
are brought up and, generally, if there is interest
in pursuing said subject, a new thread is started.

or, am i totally off base?

...and a Happy Easter to you all, too

spring is in the air, maties.
it's been sunny and in the 60s.
a veritable heat wave for these parts.
green things are popping out
and there's even a bit of color.

[hubbabubba]

(...)
green things are popping out
and there's even a bit of color.

What? Green is not a color? :greenbo::greenbo::greenbo:

[Ivan]

Any aircraft should use a CFS1-like AIR file, but land/sea vehicles...?

Last time I tried one of your AIR files for the jeep, Ivan, it was flying for miles once driven over a cliff.
Happy Easter guys!:naturesm:

Hello Hubbabubba,

My recollection was that my "drive model" didn't have any lift at all though the controls did allow it to be steered and pitched up and down if driven off a cliff. It never could reverse, so was somehat limited. I believe I sent you the final version, but perhaps I did not.

I prefered my "drive model" to yours but will admit that it was because it was doing what *I* thought it should do.
In other words, I believe mine was better more because it was mine than because of any real demonstrated superiority to your "drive model".

Happy Easter Everyone.
- Ivan.

P.S. I was stuck on a iPad for a while this afternoon while my son was playing on this computer. Re reading the first few pages of this thread was quite entertaining. Many things have changed, but many more have remained the same. It certainly is wildly off the original topic, but a pretty good general discussion in any case. Glad to have had you all here.

[smilo]

What? Green is not a color? :greenbo::greenbo::greenbo:

green, shmeen...
you know what i mean.

i did forget to mention
that the frogs are awake
and crock all night long.

and the __ __ __are moving, too

[hubbabubba]

Hello smilo

I do remember your veranda pictures; moss was growing on everything. No wonder that you would consider green sort of "blah". BTW- forest green is my favorite color. When I have a screen saver picture of a green pasture or forest (it changes every 24 hours at midnight), it makes my day.

Hello Ivan

I had comparative test drive and "my" FS98 AIR file was marginally better in speed control, acceleration, steering... but yours was getting closer after each new version. I'm not prejudiced towards CFS1 AIR files. I do remember that I did ask you to give it a try. I simply think that, having less entries, they're easier to adapt to land/sea vehicles... for now.

Hello Womble55

Ivan is probably the best "go to guy" when it comes to AIR files. Personally, I do mine more by "feelings" than specs but, when in a snag, I do turn to Ivan - but I do not always follow his advices as you can see above...

[Ivan]

Ivan is probably the best "go to guy" when it comes to AIR files....

Hello Hubbabubba,
That means quite a lot coming from you.

Hello Ivan

I had comparative test drive and "my" FS98 AIR file was marginally better in speed control, acceleration, steering... but yours was getting closer after each new version. I'm not prejudiced towards CFS1 AIR files. I do remember that I did ask you to give it a try. I simply think that, having less entries, they're easier to adapt to land/sea vehicles... for now

As I stated earlier, it all comes down to how each of us thinks a Jeep / Car should behave. We obviously don't agree here.
The areas you mentioned are exactly where I believe my "drive model" was better:

The speed control issue was one I tested quite a lot. When driving, one should be able to hold exactly 27 mph or whatever and not stray more than one or two mph and be able to do it easily. Mine did that in my testing.

The Jeep wasn't a speed demon and was about a 1800-2000 pound vehicle (loaded) with only 60 hp or so.
Acceleration would have been quite poor. The rest of the details are from memory, so beware:
Gearing was also quite non-optimal, so 0-60 times in the 12-15 second range seem about right from an intuitive sense. Top end was only about 80 mph or so IIRC and I figure a beast like this would take around 25-30 seconds to get there. Also because of the gearing, 0-10 mph acceleration should be quite good.
The resulting AIR file pretty much did what I wanted in that respect. I tested it quite a few times with a stop watch.

I also believe steering was better because you could hold a minimum radius turn only to about 20 mph and it steered quite precisely. Also, at higher speeds, there was no difficulty in being able to drive along a road and stay in your own lane which I tested using the edge of a runway and the CFS scenery "Train Tracks". Again, it did pretty much what I wanted.

There was a bit of torque effect on acceleration (CFS AIR File residue) which simulated the planting of one of the rear wheels on a high power rear-drive launch or torque steer from a front-drive high power launch. The Jeep's suspension was quite crude. The front of the jeep would dive as you might expect with braking as well.

Then again, I personally have never driven a wartime Willy's Jeep, so a lot is speculation from experience with other vehicles.
- Ivan.