• Which the release of FS2020 we see an explosition of activity on the forun and of course we are very happy to see this. But having all questions about FS2020 in one forum becomes a bit messy. So therefore we would like to ask you all to use the following guidelines when posting your questions:

    • Tag FS2020 specific questions with the MSFS2020 tag.
    • Questions about making 3D assets can be posted in the 3D asset design forum. Either post them in the subforum of the modelling tool you use or in the general forum if they are general.
    • Questions about aircraft design can be posted in the Aircraft design forum
    • Questions about airport design can be posted in the FS2020 airport design forum. Once airport development tools have been updated for FS2020 you can post tool speciifc questions in the subforums of those tools as well of course.
    • Questions about terrain design can be posted in the FS2020 terrain design forum.
    • Questions about SimConnect can be posted in the SimConnect forum.

    Any other question that is not specific to an aspect of development or tool can be posted in the General chat forum.

    By following these guidelines we make sure that the forums remain easy to read for everybody and also that the right people can find your post to answer it.

How to balance an aircraft

Messages
1,681
Country
australia
I recently downloaded a freeware (Premier Aircraft Design) aircraft which will NOT fly correctly (don't know why they would release an aircraft which doesn't fly correctly).
Regardless of speed and power setting it flies in a very nose up attitude and when I created an AI version of it when it (AI version) approaches for landing it has a nose up attitude of what could be 45 degrees (yuck).
I found a similar aircraft which flies ok and tried to compare the differences looking at the CG values but they are the same.

What should I be looking at with the view to adjusting to make the aircraft fly correctly? In the aircraft.cfg?

Thanks
 

hairyspin

Resource contributor
Messages
3,253
Country
unitedkingdom
Where are the fuel positions relative to the CG? Are there Station loads in odd positions?
 
Messages
1,681
Country
australia
Thanks Tom

I have no idea what you mean - I have never changed anything apart from contact points (so that a floatplane will work in AI) and adding new liveries. just looked at the Microsoft aircraft.cfg document and see that station loads are in there but have no idea how they should be set up. In my 'rogue' aircraft they are 16 of them.
The document states that the first value is the weight and the second the offset relative to the datum reference point.
I compared these to the other aircraft which flies correctly and is similar (the good one an amphibian and the 'rogue' a floatplane both supposedly the same aircraft type DHC3 but one calls it a turbo Beaver and the other calls it a turbo Otter). I am trying to get the rogue aircraft set up to fly correctly (well it taxis, takes off, flies and lands but looks stupid especially landing) as an AI aircraft as there are no floatplane variants of the good one.

Firstly I noticed that the 'good' aircraft only has 6 station load points and the 'rogue' has 16.
Maybe I should firstly just replace the 16 with the 6? Can't hurt trying. Maybe like the 'scrape contact points', some aircraft have many more than others for realism?
ALTHOUGH the offset reference point relative to the datum reference point is ZERO for the aircraft which (seems to) fly level.


John
 
Last edited:
Messages
913
Country
indonesia
I ever heard from a friend that playing with AI, he told me that he don't like about landing not smooth for AI ( bump), and he solved the issue by adjusting the airspeed on aircraft.cfg. hope this make another clue for your problem. I never try this, but my friend does.
 
Messages
1,681
Country
australia
Thanks Kalang
It is possible for AI aircraft to land smoothly. I have two difference ones which land very nicely. Thanks for the suggestion though. Maybe my other two have the airspeed already set up nicely.
BUT in the one I am having problms with even flying it as a user aircraft you have to either constantly push the joystick forward a far bit or use heaps of trim to make it fly level regardless of throttle setting AND it approaches landing with a nose up attitude of what appears to be around 45 degrees whereas the other ones don't.
 
Messages
1,681
Country
australia
I tried copying all the weight and balance section from the amphibian version of the aircraft which flies ok and the AI version I created lands nicely to the floatplane and flew it as a user aircraft and while it started in a nose up attitude (I slewed into the air and went from there) when I reduced the engine power the nose came down.
Now that did not happen before I changed the weight and balance. It would remain in a nose up attitude even when the engine power was brought back to idle - the airspeed would reduce to almost the stall speed, the altitude would start to drop slowly but attitude remained in the nose up position.

Not sure if I should also change the [fuel] section parameters, what do you think? They are
[fuel]
//Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
fuel_type =2
number_of_tank_selectors =1
Center1 =0, 0, -1.5, 85, 1
LeftMain =1.5, 0, -1.5, 85,1
RightMain =-1.5, 0, -1.5, 85, 1
electric_pump=1
 
Messages
913
Country
indonesia
yes, if you change it, it will change the CG and nose pitch. I do a lot try and error on this part ( include air file) for my MV-22B project. it will be a new standard your aircraft pitch. be aware that if you get right pitch at takeoff/landing, you must test it when cruising. both condition must met or you will meet with strange pitch at some condition (like cruise).

from my logic ( that my friend do) is if AI system try to reduce speed to get landing speed, but is same time aircraft must at right landing path. when low speed, aircraft will faster descent to keep aircraft at right path AI system auto will gain pitch to correct landing path. you can try to other condition like fly with autopilot when climbing, autopilot control vertical speed (and heading/course if necessary), you have the throttle. try to reduce speed as low as possible ( don't get stall). so what happen with your nose pitch. it will gaining pitch to catch up how much your vertical speed set.
 
Messages
1,681
Country
australia
Well using the [weight and balance] section to contain the same as the other aircraft (the amphibian) not only made the user aircraft more manageable and realistic it also made my AI version pitch more realistically during landing HOWEVER landing speed seemed to be too slow.
I looked at the [reference speeds] section in aircraft.cfg (the only place I could find anything to do with speed) and compared to other similar aircraft and the figures are very similar. I am wondering if there are other settings which affect the airspeed when landing of an AI aircraft.
 
Last edited:

Roy Holmes

Resource contributor
Messages
1,803
Country
us-virginia
John,
Have a look at http://www.fsdeveloper.com/forum/threads/fsxa-ai-flare.49157/#post-189541 especially my post#9.
AI planes adopt a 2° nose-up attitude on the 3° approach, so they fly at whatever speed gives them 5° angle of attack, in the landing configuration.
To get them to fly faster you will need to decrease their lift in this configuration. To do this simply, reduce lift_scalar = 1.0 in the [flaps.0] section of the aircraft.cfg. That will force the plane to go faster to compensate for the reduction in lift coefficient.
Roy
 
Messages
1,681
Country
australia
Thanks Roy

I will also adjust the lift_scaler in the other direction for my AI DHC2 Beaver as it seems to approach for landing much too fast and then touches down so far down the (water) runway that it aborts the landing. Makes a lot of sense.

I am learning that its not as easy as just adding wheel contact points for floatplanes to work as AI aircraft.:rolleyes:

I thought that if the user aircraft flew ok then the AI version (using the same aircraft.cfg apart from contact points with floatplanes) also would, how wrong it seems I was.

Added later.

Success thanks to you Roy.
Not only did reducing the lift_scalar in my AI Otter result is a faster landing speed increasing it in my AI Beaver eventually reduced the landing speed. At first it was still too fast and the AI Beaver would NOT touch down as (I suspected) it would have run out of 'runway' so I thought that I would try increasing the drag_scalar value and that worked. It is still a little fast but now it will land and stay down. What then would adjusting the pitch_scalar do? I noticed in the Beaver it is 1.0 but in the Otter it is 0.01 - very diffeernt figures.
Please note the Beaver is piston engined and the Otter turbo prop.


Thanks again
John
 
Last edited:
Messages
1,681
Country
australia
Is there something else which I can change to slow down the (DHC2 Beaver) AI floatplane when landing as it still approaches very fast and does not touch down until at least half way along the "runway" as the rate of descent seems slow.
 

Roy Holmes

Resource contributor
Messages
1,803
Country
us-virginia
John,
There are lots of ways to do almost anything to the flight characteristics in the sim, many of them are complex.
The easiest ways involve the aircraft.cfg scalars, but they can only adjust what is in the sir file.
I'm surprised that the Beaver is flying fast because it (stock FSXA model) has a lot of lift and should approach at about 50 kts.
If you get desperate, PM me the air file.
Roy
 
Messages
1,681
Country
australia
Thanks Roy,

I agree with the low airspeed of the Beaver during landing the user aircraft. It just doesn't make sense although I did read somewhere that not all user aircraft either fly well as an AI aircraft or in fact CAN fly as an AI aircraft and I suggest that is with the standard aircraft.cdf file.

I am using the stock FSX DHC2 Beaver aircraft and so if you have FSX installed you could check your copy of the air file if not then I will send one BUT -

I experimented using the AI DHC2 Beaver which comes with the VICTORIA scenery package and found that it too approached very fast and would not touch down (I assume because the approach was so fast it ran out of 'runway'). I checked the scalar values in the [flaps.0] section and they were 0.0 so I changed them to (lift)1.2, (drag) 1.5, and pitch 1.00 and retested and it then approached AND landed at a very reasonable speed.
I am now comparing all the values (other than things like forcefeedback etc etc which don't seem to have any affect on the flying as AI) and see what the differences are.
Not sure if I can compare the .air files unless I find a 'disassembler' but maybe just 'tweaking' my aircraft.cfg file will be sufficient.
The Beaver aircraft in the Victoria package appears to be maybe an FS9 aircraft (not as detailed as the stock FSX one) and I am wondering if changing my AI aircraft.cfg (modified stock FSX) will work.

I guess I could try copying the aircraft.cfg but that would be 'stealing' as the aircraft.cfg has the following -

// by Ronald Zambrano, radzamb@hotmail.com
//
// air file with kind permission by Tom Miller
//
// !!!Copyright remains with the original authors!!!

I have found MANY FS2004/FS9 AI floatplanes available for download but NO (so far) FSX AI floatplanes to download. I wonder why.
 
Last edited:
Messages
1,681
Country
australia
Hi again Roy,

I have adjusted the scalar settings in the [flaps.0] section but still would like the AI aircraft to approach and land slower as well as loose altitude faster if possible.
I tried adjusting the scalar settings in the [flight.tuning]section but ended up making the situation worse.

I sent the air file via PM and hope that you received it.

I am considering purchasing AirWrench but wonder if I will understand what to adjust. I am a complete novice with aircraft settings. Maybe there is documentation somewhere to explain how everything works and comes together or is it something you just have to pick up and understand yourself.

It is strange that the FS9 AI DHC2 Beaver which comes with the Victoria scenery package flies really nicely especially during landing so does my AI version of the DHC3 turbo otter.
I have compared the scalar values in the aircraft.cfg for both of them with my AI version of the tock FSX DHC2 and they are either the same or very similar.
 

Roy Holmes

Resource contributor
Messages
1,803
Country
us-virginia
John,
The air file is the same as the one I had. I had a reply in draft for you yesterday, but bungled something and it disappeared!.
AirWrench is great for building a new set of FDE, but it essentially fits you up with an airfile depending on what type of airplane you are creating. You also can not just change one thing, it saves a new file as it thinks fit. There is a companion program called AirWiz, which I use all the time because you can edit one thing at a time and see the effect without having to create anything permanent. However it is probably more than you want to chew at right now.
There is an excellent document called Flight Dynamics in MSFS by Yves Guillaume, which is the Bible on performance as far as I'm concerned, but it is a study rather than a read

Anyhow I think the problems lie in the air file, it has enormous values for lift coefficients and generally flies at low AOA due to the airfoil camber. I could fix it all and will try to fit it in but I'm sort of up to my neck with four different fighter FDE projects at the moment.
Although I did a lot of AI checking some years back and have data on 46 airplanes in the landing phase, I did not have any floatplanes or even a Beaver with wheels. The Goose was very stable and made excellent wheel landings, for example.

Roy
 
Messages
1,681
Country
australia
Thanks Roy,

Maybe I will consider getting AirWiz but will certainly look for the Flight Dynamics doc.

I have done some research and have read that AI aircraft often do not fly like the user version and that AI flights fly with empty fuel tanks which would affect flying characteristics with no weight. I am interested in the DHC2 Beaver floatplane (and the DHC3 Otter floatplane) as they are the common aircraft in British Columbia (where my water airport is) and my favorite livery is the special Kenmore Air with Rocky and Bullwinkle on the engine cowling and tailplane.

Screenshot.jpg

I have changed the scalar values in the [flaps.0] section with some success in slowing the approach speed down and now it will at least approach slow enough to land before running out of runway - strangely the glideslope doesn't appear to be as high as that used by my DHC3 which lands not far past the threshold. I guess that is possibly 'tied' to the fast approach speed. I have read about glideslopes elsewhere (maybe a thread from yourself if I remember correctly) but didn't understand most of the abbreviations (understood what AOA meant and that was all).
Maybe I should try increasing the scalar values more but wonder is there a 'limit' to how high you should go with those values without mucking up something else. Maybe its trial and error.

Once again thanks.

John
 
Top