Airbus A320 [Family]

[ja sam niko]

The results are hilarious ....The take off speed was about 450 kts but after that,it was something I was waiting for a looong time... The aircraft was flying and climbing like it should .. Beautiful. Level,without any wild reactions....like a dream.









So ,man i owe you. A LOT. Not just a favor but a drink. :p

I will tweak that a bit more to make nose lighter and TO speed more normal...but this is a huge,huge ,huge step forward.


Good job man....good job.



Cheers

[Bjoern]

It's okay...I just hope that I gave you momentum enough so that you can tinker with the FD even more.

Here's relevant bits from a FD configuration file for an A321-211 for MSFS:

Code: Select all

[weight_and_balance]
//A321-211/231 config
     
//Pax Zonings
//weight, longitudinal(fore-aft),lateral,vertical position
station_load.0= "9395.2,  29.24, 0.000, 0.000,  CAB OA (74)" //Forward Section
station_load.1= "9116.6,  -3.33, 0.000, 0.000,  CAB OB (74)" //Middle Section
station_load.2= "8985.1, -31.34, 0.000, 0.000,  CAB OC (72)" //Rear Section 

//Cargo & Baggage
station_load.3= "3880.1,  28.11, 0.000, 0.000,  CPT FOR"     //Forward Compartment (12500lbs)
station_load.4= "3986.9, -18.46, 0.000, 0.000,  CPT AFT"     //Aft Compartment     (12500lbs)
station_load.5= "952.5,  -39.22, 0.000, 0.000,  CPT BLK"     //Bulk Compartment    (03300lbs)

//Basic Weight

empty_weight=120847.4
empty_weight_roll_MOI=959904.000000
empty_weight_pitch_MOI=1710000.000000
empty_weight_yaw_MOI=1230000.000000
empty_weight_coupled_MOI=0.000000
max_gross_weight=196210
reference_datum_position=0.0000,0.000000,0.000000
empty_weight_CG_position=0.63,0.000000,0.000000
CG_forward_limit=0.18
CG_aft_limit=0.40


[airplane_geometry]
wing_area=1317.503
wing_span=111.833333
wing_root_chord=13.76
wing_dihedral=3.298901
wing_incidence=-3.5
wing_twist=-1.600000
oswald_efficiency_factor=0.745 
wing_winglets_flag=1
wing_sweep=25.0000
wing_pos_apex_lon=16.813
wing_pos_apex_vert=0.70000
htail_area=333.681
htail_span=41.666667
htail_pos_lon=-57.33688
htail_pos_vert=6.500000
htail_incidence=1.500000
htail_sweep=0.000000
vtail_area=231.424
vtail_span=17.991665
vtail_sweep=0.000000
vtail_pos_lon=-54.51698
vtail_pos_vert=19.915
elevator_area=76.500000
aileron_area=57.0
rudder_area=56.200000
elevator_up_limit=25.0
elevator_down_limit=15.0
aileron_up_limit=25.0
aileron_down_limit=15.0
rudder_limit=25.0
elevator_trim_limit=13.5
spoiler_limit=50.0 //35.0
spoilerons_available=1         
aileron_to_spoileron_gain=1.5       
min_ailerons_for_spoilerons=12             
min_flaps_for_spoilerons=0                   


[generalenginedata]
engine_type=1
fuel_flow_scalar=1.09 
Engine.0=6.500000,-18.95,-5.125
Engine.1=6.500000,18.95,-5.125
min_throttle_limit=-0.43
max_contrail_temperature = -30

[contact_points]
   //0  Class   (1= landing gear/2= scrape point/3= skid point /4= float/5= water rudder)
   //1  Longitudinal Position   (feet from reference datum)
   //2  Lateral Position   (feet from reference datum, minus=Left, plus=Right )
   //3  Vertical Position   (feet from reference datum)
   //4  Impact Damage Threshold   (Feet Per Minute)
   //5  Brake Map   (0=None, 1=Left, 2=Right)
   //6  Wheel Radius   (feet)
   //7  Steer Angle   (degrees)
   //8  Static Compression   (feet)  (0 if rigid)
   //9  Max/Static Compression Ratio   (max compression/static compression)
   //10 Damping Ratio   (0=Undamped, 1=Critically Damped)
   //11 Extension Time   (seconds)
   //12 Retraction Time   (seconds)
   //13 Sound Type   (0=Center gear/1=Auxiliary gear/2=Left gear/3=Right gear/4=Fuselage scrape/5=Left wing scrape/6=Right wing scrape/7=Aux. scrape 1/8=Aux. Scrape 2/9= Tail scrape)
   //14 IAS limit gear retraction   (KIAS)
   //15 IAS gear damage at   (KIAS)
   //Nosewheel travel, this model:
   //Main gear travel, this model:

static_pitch=-0.319722
static_cg_height=11.60811023622

point.0 = 1,  50.80,   0.0,  -11.96,  800, 0.0, 1.533, 68.0, 1.00, 1.44, 0.68, 13.2, 12.9, 0.0, 252.0, 282.0
point.1 = 1,  -4.20, -12.45, -12.27, 1200, 1.0, 1.680,  0.0, 0.72, 1.54, 0.81, 14.0, 13.7, 2.0, 252.0, 282.0
point.2 = 1,  -4.20,  12.45, -12.27, 1200, 2.0, 1.680,  0.0, 0.72, 1.54, 0.80, 14.2, 13.3, 2.0, 252.0, 282.0
point.3 = 2, -13.75, -54.58,  -0.50, 750,  0.0, 0.000,  0.0, 0.0,  0.00, 0.00,  0.0,  0.0, 5.0,   0.0,   0.0
point.4 = 2, -13.75,  54.58,  -0.50, 750,  0.0, 0.000,  0.0, 0.0,  0.00, 0.00,  0.0,  0.0, 6.0,   0.0,   0.0
point.5 = 2, -65.25,   0.00,   0.05, 750,  0.0, 0.000,  0.0, 0.0,  0.00, 0.00,  0.0,  0.0, 9.0,   0.0,   0.0
point.6 = 2,  66.16,   0.00,  -3.16, 750,  0.0, 0.000,  0.0, 0.0,  0.00, 0.00,  0.0,  0.0, 4.0,   0.0,   0.0
gear_system_type=0


[fuel]
Center1=   4.15,   0.0, -4.00, 2166.0, 6.1
Center2=   4.15,   0.0, -4.00,  790.0, 4.5   //ACT 1
Center3=   4.15,   0.0, -4.00,  790.0, 4.5   //ACT 2

LeftMain=  0.10, -19.6,  1.40, 1815.0, 6.0   //3.45
RightMain= 0.10,  19.6,  1.40, 1815.0, 6.0   //3.45

LeftAux=  -7.00, -36.4,  2.20,  232.0, 0.0
RightAux= -7.00,  36.4,  2.20,  232.0, 0.0

fuel_type=2.0
number_of_tank_selectors=1
electric_pump=0

[flaps.0]
span-outboard=0.500000
extending-time=21.000000
system_type=1
type=1
flaps-position.0=0.000000,0.000000
flaps-position.1=0.0
flaps-position.2=10.0
flaps-position.3=14.0
flaps-position.4=21.0
flaps-position.5=25.0
lift_scalar=0.0
drag_scalar=0.0

[flaps.1]     
type=2                                    // slats
span-outboard=0.95                                  // 0.0 .. 1.0
extending-time=21                                  // seconds
flaps-position.0=0   
flaps-position.1=18,
flaps-position.2=18,
flaps-position.3=22,
flaps-position.4=22, 
flaps-position.5=27,                                   
blowout-speed=260                               // KIAS
lift_scalar=0.10
drag_scalar=0.43
pitch_scalar=0.3
system_type=1

[flaps.2] //ailerons
type=2
span-outboard=0.85
extending-time=13.000
system_type=1
damaging-speed=233.000
blowout-speed=250.000
flaps-position.0=0.000,
flaps-position.1=0.000,
flaps-position.2=5.000,
flaps-position.3=5.000,
flaps-position.4=5.000,
flaps-position.5=5.000,
lift_scalar=0.25
drag_scalar=0.20

[flaps.3]  //actual flaps
type=1
span-outboard=0.85
extending-time=21.000
system_type=1
damaging-speed=233.000
blowout-speed=250.000
flaps-position.0=0.000,
flaps-position.1=0.000, 
flaps-position.2=10.000,
flaps-position.3=14.000,
flaps-position.4=21.000,
flaps-position.5=25.000, 
lift_scalar=1.50  //0.66
drag_scalar=0.48


[jet_engine]
thrust_scalar=1.0


[turbineenginedata]
fuel_flow_gain=0.00247
inlet_area=29.3000
rated_N2_rpm=14950.000000
static_thrust=25233.000000  //CFM56-5B3 corrected value. Actual T/O 32000 MCP 29090.
afterburner_available=0
reverser_available=1
bypass_ratio=4.50

[flight_tuning]
elevator_effectiveness=1.0
pitch_stability=1.2
roll_stability=1.0
yaw_stability=1.0
aileron_trim_effectiveness=0.9
rudder_trim_effectiveness=1.1
cruise_lift_scalar     = 1.35
parasite_drag_scalar=1.0
induced_drag_scalar=1.0               


You could try to "borrow" some values from it for the corresponding sections of the FG A321 and see if matters improve.
Note that all values are in ft or lbs and might need to be converted.

[ja sam niko]

You really did.

Right now,I have made changes to the CG ,in the .xml files of A320 -200 and I'm more then happy with the results.

Take off speed is OK,climb out good and the nose on level flight is not way up .

I will make more test flights to test everything.

Like I said,I'm more then happy with the results.

If I manage to solve this completely,I will switch my focus to the rudder. The "hard over" problem on start up is still there.

Thanks everyone.

Cheers

[ja sam niko]

The final verdict about the A320 Family is that I give up of this!


There's nothing I can do.

[Bjoern]

Oh FFS!

What was your goal?
What did you do to get there?
What was the actual result?

[ja sam niko]

The goal was to eliminate all the problems with the FDM ,of the A320 Family. To make those aircrafts flyable.

Lot and lots of tinkering around FDM. I was quite close to solve it,with some changes regarding Lift and flaps...

Thanks to your hints regarding the CG,I was able to lower the nose in the flight and to lower it well. The down side was that the take off speed for the A321 was 450 kts...so ....forget it.

I will focus on my airline cause that's something much more important to me. Obviously ,just about everyone here knows lot more than me about FDMs so ,that's it from me.

Cheers

[Bjoern]

Thanks to your hints regarding the CG,I was able to lower the nose in the flight and to lower it well. The down side was that the take off speed for the A321 was 450 kts...so ....forget it.

Hm, "unstick" speed too high, nose too high...

Sounds like the horizontal tailplane/elevator values need work. Maybe in the "lift coefficient" (or so) and in the "position" department.
Obviously, they do not generate enoughm lift to keep the plane nose-down or enough momentum to turn the plane yround the y-axis.

[ja sam niko]

I was tinkering around elevators,lift and flaps ,but without touching the CG...the results were not good also. It was good to eliminate the annoying pitch-dive behavior ...nothing else. The take off speed was normal,around 150 ,but the nose way up,nearly 10 deg. which made flying and even more -landing ,close to impossible.

I 'm aware that CG and lift numbers are badly wrong here...but without Omega's FBW ,this plane will not fly normally. The FDM of the Neo, is 99% the same as on this one,but with FBW... Wihout it,even the Neo will have the same problems.

Interestingly, the A320-200 reacted well on the changes in the CG,without touching anything else. But others didn't. A321 needs 450+ kts to take off,A319 can't take off at all and it sits on it's nose gear..... 318..didn't want to try.

The old Omega's A330 ,which is somewhere below,has almost the same FDM ,like this A320F but million times better,same cockpit,AP....so there must be a way to use that FDM here,with some corrections of course.


Also ,there is something else. In JSB ,there are three main unit positions ,X , Y , Z,right?

On the A340-600 for example is like this:
Z AXIS (Positive upwards, Negative downwards)
X AXIS (Positive in direction from Cockpit to Tail, Negative from Tail to Cockpit)
Y AXIS (Positive from Port to Starboard, Negative from Starboard to Port)

So I tried one more thing. I have reverted the CG data on the 321as it is by default ,and tried to add some weight to the tail area, to try to find a balance between nose and tail. The result was that the aircraft lost it's side to side stability.....so,Will someone here tell me,which of these three axis does what in the A320's FDM ,cause obviously it's not the same as for the A340?


Cheers

[daveculp]

Maybe this should be a new topic. I don't want to go through 55 pages of posts to find which particular FDM configuration file we are talking about.

[ja sam niko]

Maybe this should be a new topic. I don't want to go through 55 pages of posts to find which particular FDM configuration file we are talking about.

I don't fully understand what you are trying to say.... but I would really like to know.


Cheers

[daveculp]

If you want help with a particular file, then you should post the file itself, or at least a link to it somewhere. I've seen discussions in this forum get confusing because people end up talking about different files, or different versions of a file. If you are referencing a file that appears on one of the preceding 54 pages of this thread, please don't. I'd like to help you (in fact I've tried already, twice), but you're not helping people help you. I recommend you start a new thread which includes the file you are asking about.

[ja sam niko]

Thanks Dave but it's not one single file that I'm talking about,it's the FDM used in 4 aircrafts,in the whole A320 Family..


It will start a new topic and put the link here. There ,I will explain the current state of the aircraft and what I tried to do so far...

I hope this aircraft will finally be ok,and I'm sorry for creating confusion and all other problems.

Thanks everyone so far.

Cheers

OK people,from now on,the A320 Family FDM Changes and Improvements will be discussed here:

http://forum.flightgear.org/viewtopic.php?f=4&t=22533

[Baron210]

I was reading a little on this forum, and I noticed the post above discussing the topic of having to learn programming and such, and nobody is bothered about the A320. Well I thought I'd just add that I have been "Simming" and real life building back end full motion flight simulation PC and rack equipment for a Gatwick based flight training company, and most of what I have learned has been through keeping an open and self motivated mind. You do not have to be a "Rocket Scientist", just have the motivational spirit to learn, and believe me, when you solve a problem yourself, you get one hell of a buzz too!

Thanks for the explanation about the A380 autopilot too, been trying to solve a little problem with this, now I know!