Flight Dinamics request

[rafaelledezma]

Hello friends, I am trying to understand a little the parameters that are inside the .air file, the truth has helped me a lot to create much more real dynamics to different models for the fs that were originally wrong but, I cannot understand what the parameters are that affect the attitude of cruise flights (straight and level) it happens that in the case of an airplane flying in cruise with a positive angle of inclination which is wrong, the plane should be straight with respect to the horizon or perhaps in negative angle and I don't know what value this parameter affects, can someone help me?

 

[Roy Holmes]

The attitude a plane adopts when in cruise depends on a lot of factors but the main one is the type of airfoil shape. The angle a wing makes to the incoming airflow is called angle of attack (AOA). The airfoil shape determines the AOA where lift is zero. In the sim AOA is measured relative to the airplane's fore and aft axis.
If the airfoil is symmetrical as in fast jets, then the AOA is effectively zero for zero lift. Depending on weight, airspeed and the lift coefficient of the airfoil, level flight will always be with the nose pitched above the incoming airflow.
If the airfoil is not symmetrical as on most airplanes other than fast jets, the nose can be at a positive angle or negative angle depending on the airfoil shape.
So the answer to your question is it depends on the chosen airfoil. The AOA to lift coefficient characteristics are given by record 404 in the air file.
Roy

 

[rafaelledezma]

The attitude a plane adopts when in cruise depends on a lot of factors but the main one is the type of airfoil shape. The angle a wing makes to the incoming airflow is called angle of attack (AOA). The airfoil shape determines the AOA where lift is zero. In the sim AOA is measured relative to the airplane's fore and aft axis. If the airfoil is symmetrical as in fast jets, then the AOA is effectively zero for zero lift. Depending on weight, airspeed and the lift coefficient of the airfoil, level flight will always be with the nose pitched above the incoming airflow. If the airfoil is not symmetrical as on most airplanes other than fast jets, the nose can be at a positive angle or negative angle depending on the airfoil shape. So the answer to your question is it depends on the chosen airfoil. The AOA to lift coefficient characteristics are given by record 404 in the air file. Roy

The attitude a plane adopts when in cruise depends on a lot of factors but the main one is the type of airfoil shape. The angle a wing makes to the incoming airflow is called angle of attack (AOA). The airfoil shape determines the AOA where lift is zero. In the sim AOA is measured relative to the airplane's fore and aft axis. If the airfoil is symmetrical as in fast jets, then the AOA is effectively zero for zero lift. Depending on weight, airspeed and the lift coefficient of the airfoil, level flight will always be with the nose pitched above the incoming airflow. If the airfoil is not symmetrical as on most airplanes other than fast jets, the nose can be at a positive angle or negative angle depending on the airfoil shape. So the answer to your question is it depends on the chosen airfoil. The AOA to lift coefficient characteristics are given by record 404 in the air file. Roy

POST CORRECTED!
Hello Roy, thanks for answering, I am going to dedicate myself to studying the value 404. The truth is that the models are very good and deserve the time to adjust the values. The drawing shows the difference in flight attitude using different .air files even when they have the same aerodynamic values (1101) and the same efficiency and propeller coefficient values (511 512). The plane has a different flight attitude. say, it is evident that there is another value that affects the flight attitude in cruise.

In the case of the CARENADO CT206H I have put the real values of the plane into the .cfg file and have adjusted the values in the .ar file so that the plane flies as the manufacturer suggests in the POH, your answer speaks the truth and it is for that reason that I write my friend I am very grateful for your answer.

There are other values for example, the coefficient and efficiency of the propeller 511 and 512 where I do not understand its complexity, I suspect that there is the secret to be able to gain speed without sacrificing drag or power that is consistent with the sound of the engine and the RPM. I do not know if the greater argo speed is gained along the arc. Do you know anything about it?



NOTE: I made the drawing of the arch trying to interpret or understand what I can on the internet. Do you know anything about that? THANKS ROY !!

 

[bstolle]

Hi,
I just compared the cfg file with the original one and I noticed a few things which are different from the original cfg file. This cfg file has been modified already.
It would be interesting to see the rest of the cfg file and what else has been changed.
The engine location has been moved back by almost 9ft ? and the thrustline entry has been added.
The cylinder displacement is six times higher than in the original cfg ?
The 511 table is for another aircraft, a C421.

Bernt

 

[rafaelledezma]

Hi,
I just compared the cfg file with the original one and I noticed a few things which are different from the original cfg file. This cfg file has been modified already.
It would be interesting to see the rest of the cfg file and what else has been changed.
The engine location has been moved back by almost 9ft ? and the thrustline entry has been added.
The cylinder displacement is six times higher than in the original cfg ?
The 511 table is for another aircraft, a C421.

Bernt

Virtually no paid or free aircraft have references and real values, in the case of the Cessna C421 Golden Eagle it uses a 375 HP turbocharged Continental GTSIO-520-N engine with 7.5: 1 compression radius.

Logically, if we adjust the engine reference numbers to the real manufacturer value, the airplane will have wrong and unreal behavior and that's when we have to adjust the values inside the .air file for the airplane to fly correctly.

I have invested a lot of time modifying all these aircraft following the engine manufacturers' references and adjusting them to the POH of each aircraft model and I have managed to have excellent results but there are values that I have not discovered and achieve more real changes in the case of the attitude of Flight of the Cessna C421 Golden Eagle from ALABEO too.

I have also adjusted the weight and balance of each airplane by locating each value in its position in the model (passengers, engines, fuel tank, wheels, visual reference point of contact, lights etc) and that also influences the behavior of the airplane considerably. and flight attitude.

All of my paint work and flight dynamics modifications are freely available on my YVRepainter Shop Facebook page. I am available to order for requests or suggestions whenever Brent has time. The Cessna C421 Golden Eagle is one of my favorites and it flies very well. I RECOMMEND IT!

 

[bstolle]

I hope that you are not using the real numbers for e.g. the passengers and fuel tank locations since this will make the C421 react in a non-realistic way.
Concerning the cylinder displacement...520 means that your engine has six times the displacement of the real engine!
Another item is your test at non-ISA conditions. FSX/P3D are not very accurate at calculating ISA deviations. Chances are that the performance at ISA conditions will be incorrect.

 

[Ellover Dee]

To the original post:

What you are concerned with is "angle of incidence". This is the angle at which the main wing is mounted on the fuselage.

Flight Simulator does not know or care what the specific type of airfoil is in terms of its name or design, such as a NACA 5-digit, or whatever. The only thing it wants to see is the curve created by that airfoil as determined in a wind tunnel, or these days, in a a computer program which replicates a wind tunnel. That curve is remarkably similar for almost all airfoils commonly used in subsonic aircraft, with a spread of about 17 degrees from zero lift to maximum lift.

Past versions of Flight Simulator used an entry for angle of incidence in the aircraft.cfg file, which is still there, but does nothing in FSX/P3D. So we need to shift the lift curve in 404 to account for the angle of incidence. Move it right, the plane will fly more nose-down, and to the left, more nose-up.

To address the issue of using the actual locations of weight and fuel; it is not entirely impossible to use the exact locations and achieve an excellent flight model but it takes a great deal of work to manipulate all the factors involved and usually is not worth the trouble.

AirWrench will "repair" weight/balance by just locating everything at the specified center of gravity but is not at all realistic.

There are a lot of things that are commonly believed to be impossible with FSX/P3D flight dynamics but a better word might be "impractical".

 

[Ellover Dee]

"It is evident that there is another value that affects the flight attitude in cruise."

Yes, you are right. I missed this comment; that value is, as I indicated in an earlier post, angle of incidence.

Thrust from 511/512 have no effect on cruise attitude. Also, a photo-realistic replication of an efficiency curve is not exactly what FS is looking for. Values on the X/Y axes tend to be exaggerated visually so an effective and realistic curve will appear somewhat differently in FS than in a real-world test report. Examine some of the stock aircraft; they are a good starting point but a great deal of cleanup is needed.

As you pointed out, there are few airplanes, either freeware or payware, that use actual values. This is not because actual values don't work, it's simply because flight modeling is a tricky business.

 

[rafaelledezma]

Indeed, in table 404, along with other values, the attitude of cruising is changed, since I was able to adjust many of the planes that erroneously fly, in one of the images that I put here I show the C404 Titan adjusted to the values in the POH table. and there is an error, I made the plane fly in KIAS speed by KTAS, now the adjustment is published to the actual table. I dedicated myself to adjusting the models because they are very good in aesthetics but unreal in dynamics.

 

[bstolle]

I made the plane fly in KIAS speed by KTAS, now the adjustment is published to the actual table.

I don't understand this sentence. Are you saying that the original C404 has IAS and TAS mixed up? (Unfortunately the screenshot is too small to be able to read anything.

 

[rafaelledezma]

I don't understand this sentence. Are you saying that the original C404 has IAS and TAS mixed up? (Unfortunately the screenshot is too small to be able to read anything.

When I made the modification I had an error in the interpretation of the POH table, I confused KIAS and KTAS, I modified the plane so that it crossed KTAS in KIAS

 

[bstolle]

That makes sense since this aircraft looks a lot like the Alabeo C404. With the original FDE the cruise performance matches the POH values within 2% in your 10000ft example.

 

[rafaelledezma]

That makes sense since this aircraft looks a lot like the Alabeo C404. With the original FDE the cruise performance matches the POH values within 2% in your 10000ft example.

In my case it was nothing real so I modified it, totally unreal

 

[bstolle]

How many hours do you have on the real C404?

 

[rafaelledezma]

How many hours do you have on the real C404?

I am not a real pilot I only fit the model to the POH which is real data

 

[bstolle]

Sorry to say, but since you even misread the POH tables and mixed up IAS and TAS when you 'corrected' the 404, I doubt that you can get any closer than the 2% deviation.
In most parts of the cruise envelope the difference is even lower.

 

[rafaelledezma]

Sorry to say, but since you even misread the POH tables and mixed up IAS and TAS when you 'corrected' the 404, I doubt that you can get any closer than the 2% deviation.
In most parts of the cruise envelope the difference is even lower.

I think we are both misinterpreting everything, I said that I had a POH reading error in the first modification in the KIAS and KTAS and I recognize it, that's why I modified it a second time adjusting the plane as close to the POH, there is no plane that flies real in the simulator because all the planes fly at 60 knots and that is unreal, in the case of CARENADO and ALABEO the C404 had many errors with regard to fuel in crocero, position of the center of gravity and distribution of the weight of cargo and passengers, Propeller size error among many other things and they are what I have modified, even though I am not a real pilot, the plane flies unreal compared to the manufacturer's POH, what I am looking for is for the plane to fly the closest thing to the data of the POH that's why I do the comparison in the image and nothing else, I repeat again, I had a bad reading in the first modification regarding KIAS vs KTAS and it was already adjusted, The moderator is originally unreal regarding POH

 

[bstolle]

What do you mean with: all the planes fly at 60 knots and that is unreal ? As I've mentioned in this thread before, simply using real world numbers doesn't create a realistic flight model.
If you are e.g. using the 'real' distribution of passenger and baggage weight you are decreasing the realism. And again, you also misunderstood the cylinder displacement in the cfg file.
I'm not aware that Alabeo 404 doesn't perform according to the POH. Do you have an example?

 

[rafaelledezma]

What do you mean with: all the planes fly at 60 knots and that is unreal ? As I've mentioned in this thread before, simply using real world numbers doesn't create a realistic flight model.
If you are e.g. using the 'real' distribution of passenger and baggage weight you are decreasing the realism. And again, you also misunderstood the cylinder displacement in the cfg file.
I'm not aware that Alabeo 404 doesn't perform according to the POH. Do you have an example?

What I mean is that almost all the planes in the sim including the C404 at 60 knots still fly and that is unreal, that the entire group of cargo and passengers is in front of the wing rope in the model is totally unreal no matter if the passenger number are real or not, this causes the plane to adopt an unreal flight attitude and almost all models for the simulator including the C404 have that error, I just put each data in its place within the model and nothing else that It's what I do. In the case of the C404, the plane comes with Continental GTSIO-520-M engines with 520 cubic inches of cylinder deflashing, that's not what I say, that's what the manufacturer says and I adjusted that value within the C404 .cfg file that It was also unreal just to almost all the remaining data, my configuration is not close to 2% as you say but it is closer than the original configuration of the C404 model. this is the last time used to answer you because I repeat, we are both misinterpreting everything, I the POH and you my comments

 

[bstolle]

I agree. This doesn't make much sense. When you e.g. alter the prop diameter you have to change the prop curves in the air file as well, otherwise the prop efficiency is wrong.
I don't know what a 'wing rope' is. CG has an negligible effect on pitch attitude at cruise. At low weight the stall speed of the C404 is 60kias, so I don't see this problem either.
The 520 cubic inches is the total for all 6 cylinders, not 1. etc. etc. etc.