Conspicuous by Their Absence

Hello Womble55,

Actually what I showed for the fowler flaps isn't quite as easy as you describe.
The flap segment WILL rotate 45 degrees (or 90) unless you choose to hide some of the movement.
The underside of the airfoil in those drawings was level which meant that the angle of the deployed flap must be -45 degrees.
If the underside (or rather the retracted flap) was angled other than level, the deployed version would end up at another angle.
The distance was set by eyeball but is far enough away so that the angle subtended a segment as long as the projected flap chord. Perhaps 22 degrees would be a better value to use?

As for just feeding in values and getting a resulting AIR file, AirWrench can do that for you, but I would much rather learn enough about the AIR file to figure out how to do things myself. If speed at altitude is all you are looking for, I can tell you how to do that. It isn't hard. I was debating on doing a couple short tutorials.

- Ivan.
 
I would like to be able, without going through the entire list of an Air File to get my beast sitting at the right height above the tarmac, to sit at the right angle, to lift off at the right angle (not as though its on a lift), to turn correctly, to respond to the input of the controls correctly ( without going into a high speed stall or sideslipping as soon as you look at it) and all of the other deviations of trim associated with flap and undercarriage acutation. To be able to increase or decrease the effect the elevators, ailerons or rudder have with ease.

Its a long winded process at the moment and beyond the majority of people unless they stick the Abacus booklet to their knee and go through each point on the Air File.

I did an experiment with speed many years ago by building a sparrow missile and endowing it with a very high thrust. A bitch to control but it could shoot down bombers at altitude in a most effective way not usually seen in the avalable files to CFS users.

Im not a speed jockey, the successful finding of a pile of gravel in the road on a sharp bend in a typical english country lane while riding my motorcycle at 45mph and subsequent deposit of said motorcycle and myself into a ditch put paid to that desire. Besides, the buses I drive will only reach 45mph if dropped from a Hercules at 20,000ft which suits me fine.

I know there are people out there who can twiddle an Air File to within a gnats personal bit with ease. My enjoyment is making the bodywork, doing the panelbeating, solving a simple problem like why does a panel disappear and reappear. A particular favourite is getting all of the struts on a biplane to display in order with the engines and both wings. This is further compounded with wingtip floats but dividing the various part/components into zones helps immensly.

When I get the display right I will then go through other projects with the same problem and hopefully rectify them.
 
Hello Womble55,

I am still thinking that if AIR files really bother you that much, you should just buy AirWrench from Jerry Beckwith.
These days, tweaking AIR files is a fair amount of the fun. It does get frustrating at times, but if your standards are not very high, a fair one should only take a couple hours of editing and testing. That amount of time will put you ahead of perhaps 95% of the developers out there.

Getting the handling just right took me a dozen hours spread over 2 weeks for the A6M2 project, but I was in no hurry.

I figure I can do a maximum speed test accurate to within 2 mph and 100 feet altitude in about 15 minutes, so it really isn't that hard to do. Climb tests take a while as do Service and Absolute Ceiling tests.

I do almost all of the performance tests via autopilot so perhaps I am cheating.

I don't believe the Abacus information for editing AIR files is all that accurate any more. It has not been updated in a bunch of years. The really hard part about AIR files is doing the basic research. Even if you use a tool to build the AIR file, you will still need to do research. Sometimes this can get stupid as well. I spent a fair amount of time chasing down the fuel tank volumes for the A6M2. It mattered to me whether it was 190 or 195 liters in each wing tank.

BTW, Aircraft Animator can sometimes be used to create very interesting sequences. Check out my F4F Wildcats and their landing gear retraction animation. I believe that it worked out fairly well.

- 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.

I have downloaded AirWrench but its on my wife's netbook and I need to transfer it to my working PC before I can delve into this side of things. I hadn't heard of AirWrench until you mentioned it, many thanks as I would have continued in the dark as it were.

I have a few projects that could benefit from the application of this program, you never know, I might be able to get my Pogo or Treibflugel to take off and land properly.
 
AIR Files

Hello Womble55,

I can't really claim to be any kind of expert with AIR files, but pretty much accomplish what I set out to do with them.
I always start off with the stock P-51D AIR file or something I have already derived from that. The P-51D flight performance is pretty unrealistic and it has a bunch of messed up parameters, but other than behaving like a mod, it sorta kinda flies.

As for AIR Wrench, I have not used it yet. I would rather understand what I am doing instead of just plugging in numbers.
The manual for AIR Wrench is a very interesting read. It answers a lot of very basic questions as to what various records mean. I also often use the stock AIR files as references.

I don't think CFS can handle such things as your Pogo or Triebflugel any more than it can handle spacecraft or cars or ships even though we do use it for that.

If you have a regular aeroplane that needs an AIR file edited for it, email it to me and I will see what I can do. I will also provide a little explanation of what I changed and why. I have a lot of notes, most of which are just hand written in a steno notebook, so a general description isn't easy but for specific problems, it is useful. For a specific case, check out my thread on the A6M2. I was trying to create a shake in the aircraft at a specific airspeed and was able to tune using information from the notes.

- Ivan.
 
A6M3 Model 22

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.
 
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.
 
Aircraft Animator again

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=A0OSLUaqIzg&NR=1&feature=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.
 
"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
 
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.
 
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
 
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.
 
womble55 said:
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.
Click to expand...

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/sohforums/showthread.php?76569-What-Key-info-is-need-to-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.
 
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.....
 
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.
 
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.
 
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.
 
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.
 
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-rho-v-2-versus-indicated-air-speed-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/sohforums/showthread.php?76569-What-Key-info-is-need-to-create-an-FDE

- Ivan.
 
Cheating in Development

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.
 
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