FSX/ESP Airfile Table 1101

[mgh 89]

Does anyone know if Table 1101 is still needed for FSX/ESP aircraft add-ons?I ask because, it isn't used in any of the sample ASM files given in the ESP SDK, although it still appears in the list of tokens in the file airfiletokens.h. (This file lists the descriptive names (tokens) for the tables together with their numbers.) The names of many other tables in that file are prefixed by either UNUSED_ or OBSOLETE_. but not Table 1101 which is named AIR_VARIABLES. Also sample airfiles have the comment ;**** END OF REQUIRED AERODYNAMICS ***** so it seems Table 1101 may not be requiredAirEd and AircraftAirfileManager show CD₀ together with the other basic drag coefficients appearing in Table 1101 as int16 (short). But in the sample files they appear in Table 1540 as AIR-80_DRAG_PARAMS as REAL8 (double). This is also the case for the basic lift and pitch parameters. However, to confuse the issue these "new" tables don't seem to be used in the FSX default aircraft I've looked at which contain Table 1101, although they are in the sample files!

[dmaher 0]

I’m not sure I completely understand, but I’ll go ahead and post some of my conclusions.Yes..Table 1101 is still req'd for FSX/ESPI compared PistonSample.asm with FSX Mooney_Bravo.airThe data corresponds 100% except for table 1101. (and possibly table 1199 – AI control)Table ‘1101-Primary Aerodynamics’ corresponds to ESP’s ‘REQUIRED AERODYNAMICS’...they are the same thing.ESP's ‘REQUIRED AERODYNAMICS’ section is very concise and lists only conventional Jan Roskam coefficients.Table 1101 as we know it contains many unused and obsolete parameters…that likely should be avoided.For my own benefit I edited ‘AircraftAirfileManager.ini’ to reflect only ESP coefficients listed in PistonSample.asm.This is very risky because there are likely important and valid ESP coefficients that weren’t used in PistonSample.asmBut for a GA piston single it's a reasonable choice.In PistonSample.asm, CD0 is in ‘AIR_80_DRAG_PARAMS’ - subsection of ‘REQUIRED AERODYNAMICS’So I’d expect to find in table 1101 using AAM...which it is.As far as I can see...Mooney_Bravo.air doesn’t have a table 1540.PistonSample.asm doesn’t have a table 1540...either.So table 1540 is dead to me :)However, I’ve never looked at airfiletokens.h.So you have some extra information...that could shed better light.

[mgh 89]

I agee it's confusimg. The default FSX aircraft seem (I haven't obviously checked all of theml) to use Table 1101, even though the ASM samples don't. The samples include

TOKEN_BEGIN     AIR_80_LIFT_PARAMS                REAL8   0.000000        ; CL spoiler                REAL8   1.2             ; CL flaps                REAL8   0.000000        ; UNUSED                REAL8   0.715988        ; CLih                REAL8   -0.273018       ; CLde                REAL8   0.000000        ; UNUSED        TOKEN_END        TOKEN_BEGIN     AIR_80_DRAG_PARAMS                REAL8   0.065           ; CDo                REAL8   0.07            ; CD flaps                REAL8   0.007000        ; CD gear                REAL8   0.000000        ; CD spoiler        TOKEN_END        TOKEN_BEGIN     AIR_80_PITCH_PARAMS                REAL8   2.133893        ; CMih                REAL8   -1.6            ; CMde                REAL8   -0.051200       ; CMde due to propwash                REAL8   -2.601277       ; CLq                REAL8   0.988016        ; CL adot                REAL8   2.0             ; CM adot                REAL8   -28.770823      ; CMq                REAL8   -10.000000      ; CMq due to propwash                REAL8   0.0             ; CMo                REAL8   -0.07           ; CM flap                REAL8   -1.066947       ; CM delta trim                REAL8   0.020000        ; CM gear                REAL8   0.000000        ; CM spoiler        TOKEN_END        TOKEN_BEGIN     AIR_80_SIDE_FORCE_PARAMS                REAL8   -0.569647       ; CyB                REAL8   0.038363        ; CyP                REAL8   0.018805        ; CyR                REAL8   -0.153025       ; Cy Delta Rudder        TOKEN_END        TOKEN_BEGIN     AIR_80_ROLL_PARAMS                REAL8   0.045           ; ClB                REAL8   -0.9            ; ClP                REAL8   -0.061076       ; ClR                REAL8   0.000000        ; Cl Delta Spoiler                REAL8   -0.269225       ; Cl Delta Aileron                REAL8   0.010           ; Cl Delta Rudder        TOKEN_END        TOKEN_BEGIN     AIR_80_YAW_PARAMS                REAL8   0.099757        ; CnB                REAL8   0.034553        ; CnP                REAL8   -0.524805       ; CnR                REAL8   -3.000000       ; CnR due to propwash                REAL8   0.000000        ; UNUSED                REAL8   0.000000        ; UNUSED                REAL8   -0.002345       ; Cn Delta Aileron                REAL8   0.063277        ; Cn Delta Rudder                REAL8   0.002048        ; Cn Delta Rudder due to propwash        TOKEN_END 

These are Tables 1539 (Lift)), 1540 (drag), 1541 (pitch), 1542 (side force), 1553 (roll), 1544 (yaw). They seem to duplicate (to a different precision) the corresponding entries in Table 1101. I suspect that, if present, the values in later tables wil over-ride those in Table 1101 in FSX.I haven't cross- checked other remaining entries in Table 1101 against the samples to see if they are duplicated - I suppose that's the next task :( At first sight there may be differences between the contents of Table 1101 as reported by AirEd and Aircraft AirFile Manager and the later tables so this need to be checked too!

[dmaher 0]

That’s very interesting.Do you have a copy of Asm2Air.exe? (part of ESP)It would be valuable to see the airfile generated by 'PistonSample.asm'I’m curious how you determined this…AIR_80_LIFT_PARAMS --> 1539AIR_80_DRAG_PARAMS --> 1540AIR_80_PITCH_PARAMS --> 1541AIR_80_SIDE_FORCE_PARAMS --> 1542AIR_80_ROLL_PARAMS --> 1553AIR_80_YAW_PARAMS - -> 1544I made some big assumptions, without the benefit of an actual ESP airfile - so, I’m not certain.But I came to a different conclusion.Looking at an FSX airfile (should be similar to ESP) it appears these sections are all contained in 1101.And the tables you’ve listed above are missing…and assumed obsolete.Have I missed something?I suspect either approach works for now...but I'd like to use the newer ESP convention.

[beatle 0]

Some of the values that used to be only stored in the .AIR file were superceded by values in the aircraft.cfg/sim.cfg file - not sure if that's the case with the specific section you asked about, but its possible those values come from the .CFG file.Tim

[WarpD 824]

The numeric values that identify a record/data type in an .air file is defined in the airfiletokens.h file that comes with ESP.It's my understanding that the specific AIR_80_xxx record types being discussed will override respective values contained in the 1101 AIR_VARIABLES record. However, there's a great deal of data contained in the 1101 record that isn't covered anywhere else in the .air file.

[mgh 89]

Do you have a copy of Asm2Air.exe? (part of ESP)I’m curious how you determined this…

I don't have AsmToAir.exe but do have a copy of airfiletokens.h. The relevant extract are:

AIR_VARIABLES    EQU 000001101hAIR_80_LIFT_PARAMS  EQU 000001539hAIR_80_DRAG_PARAMS  EQU 000001540hAIR_80_PITCH_PARAMS  EQU 000001541hAIR_80_SIDE_FORCE_PARAMS EQU 000001542hAIR_80_ROLL_PARAMS  EQU 000001543hAIR_80_YAW_PARAMS  EQU 000001544hAIR_80_CL_ALPHA_TABLE  EQU 000001545hAIR_80_CM_ALPHA_TABLE  EQU 000001546h  

I wrote a simple application to read an airfile and display the table numbers, token names, and table lengths .I too would prefer to use the latest tables. I'll investigate and attempt to find what variables are in Table 1101 that aren't covered by other tables.

[dmaher 0]

Ok, thanks, I understand now :)My theory that AIR_80_XXX coefficients in PistonSample.asm referred to table 1101 was wrong.They clearly have their own tables 1539-1546(although the records all exist in 1101 too)Looking at FSX Mooney_Bravo.air I had found three records in 1101 that contained data and didn’t have an equivalent in the AIR_80_XXX tables.They were…

[1101]00, int16, Airframe Type --> set to: 649750, ang16, Fuselage AoA at Min Induced Drag --> set to: -1.74725EA, int32_2, Cn_? Yaw Moment - ?? ---> set to: 6.34765

Of course, there are many other records, but they were empty in FSX Mooney.That doesn’t really confirm the empty records are obsolete…but it’s a good indication.As for the three records above, there’s a case to be made that they are legacy and not req’d.00, Airframe Type --> No one knows what this does, or how to set it :) (?)50, Fuselage AoA at Min Induced Drag --> is available in table 404, corresponds to zero lift (No?)EA, Cn_? Yaw Moment - ?? --> don’t know, but use AIR_80_YAW_PARAMS, CnB instead (?)I haven’t looked at all default FSX aircraft, so there may be other 1101 records used elsewhere.My hunch is 1101 isn't required.

[mgh 89]

As you say, all the other remaining entries in Table 1101 are covered by the new tables in the ESP SDK except for two:Offset 80 - *Fuselage AoA at Min Induced Drag. This has a value of -0.401099 for the FSX default 747. I suppose it could be used to take account of wing that is "twisted" along its span. Simple wing theory states that the induced drag is proportional to the lift coeffiicient squared so induced drag is minimised when CL is zero - ie no net lift. However, if the wing is twisted or has changing sections along is span then at zero lift some parts will have net upward lift forces and other parts will have equal and opposite net downwards lift forces . This should result in induced drag even when there is no net lift. It seems that this parameter is intended to allow for this.Offset 234 - *!Cn_? Yaw Moment - ?? This has a value of zero and, from its descrption, it would seem there's uncertainty about what it represents.It seems that Table1101 is now pretty well redunant.

[WarpD 824]

Since all the FSX aircraft have table 1101... I don't believe your conclusions are accurate regarding it's necessity/redundancy.In fact, I don't remember seeing the new records in any of the FSX aircraft at all. This tells me that they're 'latecomers' that never got fully implemented. This results in a concern that relying on them solely could result in an FDE that is at the least unpredictable and most likely unstable.

[dmaher 0]

It is strange because PistonSample.asm doesn’t appear to have table 1101.It would be very interesting to look at PistonSample.air to confirm that.That’s the quickest way to get an answer...I guessIf FSX and ESP are functional the same (Ui and such notwithstanding) you’d assume FSX doesn’t need 1101 either - if in fact ESP doesn’t.It’s unlikely ACES would have revisited FSX airfiles if the change happened late in the schedule.The other test would be to take a working and familiar airfile and move everything to AIR_80_XXX - delete 1101.Use AFSD and some flight tests to see.It would take a bit of faith to be convinced :)BTW..about - Fuselage AoA at Min Induced DragAll the AIR_80_XXX coefficients are conventional terms.But this one is not :)It seems to muddle up wing incident and aoa...and should be read from table 404CLvsAlpha IMO.Mind you it does have an effect.

[WarpD 824]

I don't believe you're correct regarding minimum drag being at the same angle of attack as minimum lift.

[dmaher 0]

As I see it....The tag is talking about ‘Induced Drag’ - not just ‘Drag’...if it’s to be trusted :)So induced drag is the component of drag from generating lift...it’s lowest value is at zero lift.The angle of attack that corresponds depends on the airfoil design.

[mgh 89]

It is strange because PistonSample.asm doesn’t appear to have table 1101.

None of the sampe aircraft files has Table 1101.I'm still thinking about the implications of Offset 80 - *Fuselage AoA at Min Induced Drag

[WarpD 824]

As I see it....The tag is talking about ‘Induced Drag’ - not just ‘Drag’...if it’s to be trusted :)So induced drag is the component of drag from generating lift...it’s lowest value is at zero lift.The angle of attack that corresponds depends on the airfoil design.

No, the tag is setting the fuselage angle of attack with relation to minimum induced drag. It's effectively setting the angle of the wing with reference to the fuselage. This value is not represented in the Cl vs AoA table at all.