Cessna 210 "Centurion" family development topic

[TheEagle]

I have just started modelling the Cessna 210 "Centurion" family for FlightGear (first variant is the Cessna T210N, others will be modelled later). I thought (and was told by other users) that I should open a development thread for it, so here it is.

I am completely new to aircraft modelling, and I know it is recommended to improve other aircraft first, but as I already have some experience with models animations, 3D modelling and Nasal because of the LandingChallenge addon and some scenery contributions, and as I couldn't find a nice small GA aircraft that pleased me, I decided to directly start on a new one. The main thing I need help with is the FDM - I have it roughly where it needs to be, but if someone with much FDM knowledge could fine-tune it, I would be really thankful !

Where to get it

I have created a GitHub repo with some basic things in it, and I push my changes at least once a day.

What needs to be done

Almost everything, but I've made a selection ordered by what I need the most help with:

• Finding data for the other variants, because on Wikipedia I could only find data for the T210N
• FDM
• Nasal
• 3D modelling
• Animating things

I am planning to implement many details such at icing (and the increased drag it produces IRL), parts of the airplane being ripped of (or squashed, or bended) when crashing them onto the ground, etc. … But first thing is of course a good 3D outside model and cockpit.

[benih]

You also might consider adding a aircraft FGFS wiki entry like for the other planes.

[TheEagle]

You also might consider adding a aircraft FGFS wiki entry like for the other planes.

Oh yeah, thanks benih for reminding me !

[S&J]

I'm not seeing any code in github

[TheEagle]

Oh, you're right ! Sorry - I just pushed the code.

[S&J]

Your props in the wrong place, centre of the engine.

What prop have you picked ?

[TheEagle]

Your props in the wrong place, centre of the engine.

How do you mean ? Where else should the propeller be than in the center of the engine ?

[S&J]

Front of the plane I'd suggest

Ok I understand which prop you've gone for and performance specs

"D3A34C402/90DFA-10 constant-speed propeller[1], 7 ft 6 in (2.29 m) diameter"

Ok so in reality your prop is 80" diameter not 90"

Yes it may say it's 7'6".... But that the price we pay for taking info off wiki without questioning everything written.

Trust nothing, question and verify everything

[TheEagle]

Front of the plane I'd suggest

Well, that's where the engine is, right ? And the propeller is about at the same place as the engine, right ?

Ok so in reality your prop is 80" diameter not 90"

What makes you think that ? 2.29 meters are exactly 90.15748 inches according to Google.

[S&J]

By that logic the wheels on a car are in the same place as the engine.

As for the conversion from meters to inches, yes can't argue with it being correct..... But the numbers on your prop tell me it's an 80" diameter prop.

I'm sure other knowledgeable fdmer's will verify for me

[dany93]

I'm looking at this but it's very long, many attempts. For various results, not always good.
The engine and propeller files are not correct.
Please be patient.

Dany

[TheEagle]

Thank you very much Dany - don't stress yourself, I'm concentrating on the 3D modelling in the meantime !

[dany93]

Propositions for the engine and propeller files.

From the T210N POH:
- The engine is Turbocharged (boosted), direct-drive (gear ratio = 1), 310 HP at 36.5 inches Hg and 2700 RPM.
- The propeller is 80 inches diameter, constant speed 12.4 to 28.5 deg blade angle.


FlightGear JSBSim :
http://wiki.flightgear.org/JSBSim_Engines
http://wiki.flightgear.org/JSBSim_Thrusters

Engine

I'm not used to boosted engines. This one works well but I may have left mistakes.

Code: Select all

<?xml version="1.0" encoding="UTF-8"?>
<!--
  File:     Continental_TSIO-520-R.xml
  Author:   Aero-Matic v 0.83

  Inputs:
    name:           Continental_TSIO-520-R
    type:           piston
    power:          310 hp
-->

<piston_engine name="Continental_TSIO-520-R">
  <minmp unit="INHG">         10.0 </minmp>
  <maxmp unit="INHG">         36.5 </maxmp> <!-- 28.5 -->
  <displacement unit="IN3"> 520.00 </displacement>
  <maxhp>        310.00 </maxhp>
  <cycles>         4.0 </cycles>
  <idlerpm>      700.0 </idlerpm>
  <maxrpm>      2700.0 </maxrpm>
  <sparkfaildrop>  0.1 </sparkfaildrop>
  <volumetric-efficiency> 0.85 </volumetric-efficiency>
 
  <numboostspeeds>1</numboostspeeds>
  <boostoverride>0</boostoverride>
  <ratedboost1 unit="INHG">6.5</ratedboost1>
  <ratedaltitude1>12000</ratedaltitude1>
  <ratedpower1>310</ratedpower1>
  <ratedrpm1>2700</ratedrpm1>

 
  <man-press-lag> 0.1 </man-press-lag>
  <static-friction  unit="HP"> 1.55 </static-friction>
  <starter-torque> 248.00 </starter-torque>
  <starter-rpm> 1400 </starter-rpm>
 <!-- Defining <bsfc> over-rides the built-in horsepower calculations -->
 <!--<bsfc>           0.45 </bsfc>-->
  <stroke unit="IN">  4.0 </stroke>
  <bore unit="IN">    5.25 </bore>
  <cylinders>         6.0  </cylinders>
  <compression-ratio>  7.5 </compression-ratio>
</piston_engine>



Propeller

The NACA curves worked well for the Douglas DC3 of the (french) Patrouille de France. On 3 or 4 aircraft, I found that the NACA curves worked well, they even gave much better results than Aeromatic curves on 1 or 2 aircraft (from my memory).
<minpitch> 12.5 deg would not work for takeoff. But 15 deg works.

Cruise performance:
(POH) : 162 KTAS expected for 4000 lbs weight at 2000 ft, 2500 RPM, MP = 30 inhg, 80% BHP = 248 HP.

FG below, measured at weight = 2942 lbs, close to 2000 ft altitude.

NACA propeller version:
NACA Report 640 (5868-9, Clark Y section)
https://vdocument.in/reader/full/naca-r ... ac866c3623
https://vdocument.in/naca-report-640-56aac866c3623.html

Code: Select all

<?xml version="1.0"?>
<!-- Dany 12 sept 2021 (proposition for a start)
From Douglas DC3 Patrouille de France, NACA Report 640
-->

<propeller version="1.01" name="prop">
  <ixx>   4.38 </ixx>
  <diameter unit="IN">  80.0 </diameter>
  <numblades> 3 </numblades>
  <gearratio>  1 </gearratio>
  <cp_factor> 1.00 </cp_factor>
  <ct_factor> 1.00 </ct_factor>
  <minpitch> 15 </minpitch> <!-- shoud be 12.4 but does not work for takeoff (??); 15 OK -->
  <maxpitch> 30 </maxpitch>
  <minrpm>   2000 </minrpm>
  <maxrpm>   2800 </maxrpm>

<!-- Data from NACA Report 640 (5868-9, Clark Y section)
https://vdocument.in/reader/full/naca-report-640-56aac866c3623
https://vdocument.in/naca-report-640-56aac866c3623.html -->

 <!-- thrust coefficient as a function of advance ratio and blade angle -->
  <table name="C_THRUST" type="internal">
      <tableData>
                  0.0000    15.0000    25.0000    35.0000    45.0000    90.0000
       0          0.0000     0.1410     0.1600     0.1740     0.1800     0.0000
       0.2000    -0.1553     0.1160     0.1550     0.1700     0.1820     0.0000
       0.4000    -0.3608     0.0840     0.1520     0.1640     0.1860     0.0000
       0.6000    -0.5049     0.0450     0.1475     0.1600     0.1880     0.0000
       0.8000    -0.5049     0.0040     0.1000     0.1550     0.1780     0.0000
       1.0000    -0.5049    -0.0520     0.0600     0.1455     0.1675     0.0000
       1.2000    -0.5049    -0.1070     0.0175     0.1175     0.1600     0.0000
       1.4000    -0.5049    -0.1300    -0.0350     0.0810     0.1580     0.0000
       1.6000    -0.5049    -0.1300    -0.0889     0.0450     0.1525     0.0000
       1.8000    -0.5049    -0.1300    -0.1300     0.0050     0.1280     0.0000
       2.0000    -0.5049    -0.1300    -0.1300    -0.0400     0.1000     0.0000
       2.2000    -0.5049    -0.1300    -0.1300    -0.0900     0.0700     0.0000
       2.4000    -0.5049    -0.1300    -0.1300    -0.1300     0.0400     0.0000
       2.6000    -0.5049    -0.1300    -0.1300    -0.1300     0.0070     0.0000
       2.8000    -0.5049    -0.1300    -0.1300    -0.1300    -0.0360     0.0000
       3.0000    -0.5049    -0.1300    -0.1300    -0.1300    -0.0780     0.0000
       3.2000    -0.5049    -0.1300    -0.1300    -0.1300    -0.1199     0.0000
       3.4000    -0.5049    -0.1300    -0.1300    -0.1300    -0.1300     0.0000
       3.6000    -0.5049    -0.1300    -0.1300    -0.1300    -0.1300     0.0000
       3.8000    -0.5049    -0.1300    -0.1300    -0.1300    -0.1300     0.0000
       4.0000    -0.5049    -0.1300    -0.1300    -0.1300    -0.1300     0.0000
       6.0000    -0.5049    -0.1300    -0.1300    -0.1300    -0.1300     0.0000
      </tableData>
  </table>

 <!-- power coefficient as a function of advance ratio and blade angle -->
  <table name="C_POWER" type="internal">
     <tableData>
                  0.0000    15.0000    25.0000    35.0000    45.0000    90.0000
       0          0.0445     0.0600     0.1490     0.2630     0.3900     2.2123
       0.2000     0.0712     0.0575     0.1380     0.2510     0.3900     2.2123
       0.4000     0.1554     0.0500     0.1270     0.2380     0.3900     2.2123
       0.6000     0.2354     0.0340     0.1180     0.2225     0.3820     2.2123
       0.8000     0.3153     0.0040     0.1000     0.2100     0.3650     2.2123
       1.0000     0.3918    -0.0170     0.0700     0.1990     0.3470     2.2123
       1.2000     0.3132    -0.0670     0.0260     0.1750     0.3325     2.2123
       1.4000     0.5411    -0.1170    -0.0229     0.1350     0.3260     2.2123
       1.6000     0.6184    -0.1670    -0.0686     0.0850     0.3180     2.2123
       1.8000     0.6930    -0.2170    -0.1146     0.0250     0.2810     2.2123
       2.0000     0.7676    -0.2700    -0.1599    -0.0343     0.2400     2.2123
       2.2000     0.8449    -0.3100    -0.2059    -0.1029     0.1920     2.2123
       2.4000     0.9196    -0.3500    -0.2519    -0.1716     0.1380     2.2123
       2.6000     0.9942    -0.4000    -0.2971    -0.2175     0.0550     2.2123
       2.8000     1.0715    -0.4500    -0.3431    -0.2608    -0.0226     2.2123
       3.0000     1.1461    -0.5000    -0.3891    -0.3088    -0.1029     2.2123
       3.2000     1.2207    -0.5500    -0.4344    -0.3548    -0.1832     2.2123
       3.4000     1.2980    -0.5696    -0.4804    -0.4001    -0.2628     2.2123
       3.6000     1.3727    -0.5696    -0.5264    -0.4461    -0.3431     2.2123
       3.8000     1.4473    -0.5696    -0.5696    -0.4920    -0.4234     2.2123
       4.0000     1.5246    -0.5696    -0.5696    -0.5696    -0.5030     2.2123
       6.0000     2.2123    -0.5696    -0.5696    -0.5696    -0.5696     2.2123
     </tableData>
  </table>


<!-- thrust effects of helical tip Mach -->
<table name="CT_MACH" type="internal">
  <tableData>
    0.85   1.0
    1.05   0.8
  </tableData>
</table>

<!-- power-required effects of helical tip Mach -->
<table name="CP_MACH" type="internal">
  <tableData>
    0.85   1.0
    1.05   1.8
    2.00   1.4
  </tableData>
</table>

</propeller>


At 30 inhg, 2500 RPM, 230 HP, blade 23 deg, : 146 KTAS.
But, close to 80% max power (cf. POH) = 248 HP it gives:
248 HP, 2500 RPM, 32 inhg, blade 24 deg : 151 KTAS (still a bit low).
The disagreement may be due to improper propeller curves (other blade section? efficiency?) or to aircraft drag at cruise velocity.

AEROMATIC propeller version:

Code: Select all

<?xml version="1.0"?>
<!-- Generated by Aero-Matic v 1.1
From Aeromatic version, Dany 12 sept 2021 (proposition for a start)

     Inputs:
                horsepower: 310
                     pitch: variable
            max engine rpm: 2700
        prop diameter (ft): 6.6666666666667

     Outputs:
              max prop rpm: 2814.45
                gear ratio:    0.96
                       Cp0: 0.052752
                       Ct0: 0.122913
       static thrust (lbs): 1270.37
-->

<propeller version="1.01" name="prop">
  <ixx>   4.38 </ixx>
  <diameter unit="IN">  80.0 </diameter>
  <numblades> 3 </numblades>
  <gearratio>  1 </gearratio>
  <cp_factor> 1.00 </cp_factor>
  <ct_factor> 1.00 </ct_factor>
  <minpitch> 12 </minpitch>
  <maxpitch> 45 </maxpitch>
  <minrpm>   2392 </minrpm>
  <maxrpm>   2814 </maxrpm>

 <!-- thrust coefficient as a function of advance ratio and blade angle -->
  <table name="C_THRUST" type="internal">
      <tableData>
                -10        0         15        25        35        45        55        65       90
      -0.2      -0.0600    0.0338    0.1229    0.1506    0.1659    0.1752    0.1614    0.1383   0.0000
       0.0      -0.0891    0.0000    0.1229    0.1506    0.1659    0.1767    0.1652    0.1383   0.0000
       0.2      -0.0999   -0.0307    0.1061    0.1475    0.1636    0.1767    0.1652    0.1383   0.0000
       0.4      -0.0999   -0.0714    0.0799    0.1460    0.1605    0.1752    0.1652    0.1383   0.0000
       0.6      -0.0999   -0.0999    0.0423    0.1314    0.1536    0.1706    0.1629    0.1383   0.0000
       0.8      -0.0999   -0.0999    0.0023    0.0983    0.1491    0.1645    0.1629    0.1383   0.0000
       1.0      -0.0999   -0.0999   -0.0399    0.0600    0.1429    0.1560    0.1614    0.1383   0.0000
       1.2      -0.0999   -0.0999   -0.0822    0.0184    0.1175    0.1506    0.1614    0.1383   0.0000
       1.4      -0.0999   -0.0999   -0.0999   -0.0269    0.0846    0.1482    0.1583    0.1383   0.0000
       1.6      -0.0999   -0.0999   -0.0999   -0.0683    0.0461    0.1429    0.1552    0.1383   0.0000
       1.8      -0.0999   -0.0999   -0.0999   -0.0999    0.0077    0.1229    0.1506    0.1383   0.0000
       2.0      -0.0999   -0.0999   -0.0999   -0.0999   -0.0307    0.0960    0.1500    0.1383   0.0000
       2.2      -0.0999   -0.0999   -0.0999   -0.0999   -0.0692    0.0692    0.1475    0.1383   0.0000
       2.4      -0.0999   -0.0999   -0.0999   -0.0999   -0.0999    0.0369    0.1205    0.1383   0.0000
       2.6      -0.0999   -0.0999   -0.0999   -0.0999   -0.0999    0.0047    0.0762    0.1229   0.0000
       2.8      -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   -0.0277    0.0499    0.0999   0.0000
       3.0      -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   -0.0600    0.0262    0.0768   0.0000
       3.2      -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   -0.0922    0.0023    0.0538   0.0000
       3.4      -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   -0.0215    0.0307   0.0000
       3.6      -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   -0.0454    0.0077   0.0000
       3.8      -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   -0.0692   -0.0154   0.0000
       4.0      -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   -0.0929   -0.0385   0.0000
       6.0      -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   -0.0999   0.0000
      </tableData>
  </table>

 <!-- power coefficient as a function of advance ratio and blade angle -->
  <table name="C_POWER" type="internal">
     <tableData>
               -10        0        15        25        35        45        55        65       90
      -0.2      0.0088   0.0176    0.0616    0.1398    0.2411    0.3429    0.3956    0.4378   0.4378
       0.0      0.0352   0.0088    0.0528    0.1303    0.2305    0.3429    0.3972    0.4378   0.4378
       0.2      0.0501   0.0141    0.0510    0.1213    0.2205    0.3429    0.3972    0.4378   0.4378
       0.4      0.0675   0.0308    0.0439    0.1118    0.2094    0.3429    0.3972    0.4378   0.4378
       0.6      0.0828   0.0466    0.0290    0.1039    0.1962    0.3360    0.3956    0.4378   0.4378
       0.8      0.0976   0.0624    0.0088    0.0881    0.1846    0.3207    0.3956    0.4378   0.4378
       1.0      0.1124   0.0775    0.0088    0.0617    0.1741    0.3044    0.3941    0.4378   0.4378
       1.2      0.1277   0.0620   -0.0290    0.0237    0.1540    0.2917    0.3914    0.4378   0.4378
       1.4      0.1424   0.1071   -0.0438   -0.0176    0.1187    0.2875    0.3867    0.4378   0.4378
       1.6      0.1572   0.1224   -0.0512   -0.0528    0.0749    0.2796    0.3782    0.4220   0.4378
       1.8      0.1725   0.1372   -0.0528   -0.0881    0.0220    0.2479    0.3666    0.4131   0.4378
       2.0      0.1873   0.1519   -0.0675   -0.1229   -0.0264    0.2110    0.3492    0.4046   0.4378
       2.2      0.2020   0.1672   -0.0828   -0.1583   -0.0791    0.1714    0.3387    0.3867   0.4378
       2.4      0.2173   0.1820   -0.0976   -0.1936   -0.1319    0.1224    0.3286    0.3782   0.4378
       2.6      0.2321   0.1968   -0.1124   -0.2284   -0.1672    0.0512    0.3207    0.3650   0.4378
       2.8      0.2469   0.2121   -0.1277   -0.2638   -0.2005   -0.0174    0.3139    0.3603   0.4378
       3.0      0.2622   0.2268   -0.1424   -0.2991   -0.2374   -0.0791    0.3033    0.3603   0.4378
       3.2      0.2769   0.2416   -0.1572   -0.3339   -0.2727   -0.1408    0.2838    0.3519   0.4378
       3.4      0.2917   0.2569   -0.1725   -0.3693   -0.3075   -0.2020    0.2200    0.3429   0.4378
       3.6      0.3070   0.2717   -0.1873   -0.4046   -0.3429   -0.2638    0.1546    0.3339   0.4378
       3.8      0.3218   0.2864   -0.2020   -0.4378   -0.3782   -0.3255    0.0860    0.3234   0.4378
       4.0      0.3366   0.3017   -0.2173   -0.4378   -0.4378   -0.3867    0.0174    0.2991   0.4378
       6.0      0.4378   0.4378   -0.4378   -0.4378   -0.4378   -0.4378   -0.4378   -0.2638   0.4378
     </tableData>
  </table>

<!-- thrust effects of helical tip Mach -->
<table name="CT_MACH" type="internal">
  <tableData>
    0.85   1.0
    1.05   0.8
  </tableData>
</table>

<!-- power-required effects of helical tip Mach -->
<table name="CP_MACH" type="internal">
  <tableData>
    0.85   1.0
    1.05   1.8
    2.00   1.4
  </tableData>
</table>

</propeller>


At 30 inhg, 2500 RPM, 231 HP, blade 24 deg, : 153 KTAS.
But, close to 80% max power (cf. POH) = 248 HP it gives:
248 HP, 2500 RPM, 32 inhg, blade 26 deg : 161 KTAS.
Here, at least at 248 HP the Aeromatic curves seem give cruise velocities closer to the POH specifs than the NACA ones.

Both seem to have a decent rate of climb (1000 - 1500 ft/mn @ 2942 lbs and 110 KTAS).

Do not take this as a reference, but I hope that these files will at least give you a start to understand and improve.

Important: do not tweak the CT, CP tables only by feeling. You would likely end up at irrealistic curves, e.g. with greater than 100% efficiency. Prior to doing this, you must understand the propeller calculations. A calculation tool as LibreOffice calc or Excel spreadsheet is almost indispensable.

In your PM, you ask:

"Would you be willing to do the FDM at least roughly ?"

Doing a correct FDM is a very long work, at least a few weeks, more probably months.
You already have a basic one which flies.
For a basic one, I will not do better, I'd start from scratch by using Aeromatic.
For you to learn, I'd recommend the same way (maybe the one you used): doing a basic FDM from Aeromatic and trying to understand and improve it.
For the coefficients, Megginson's table is a good reference.
Taking a FDM already done from another aircraft is doable if you have only small changes to do. Otherwise, you risk to have a too much sophisticated, complicated one, difficult for you to understand. And, maybe, not well fitted for your aircraft.

Dany
________________________________________________________________________________________

[TheEagle]

Thank you Dany !

I found the reason for the low cruise speed : you have to
1. retract the gear ad
2. set the <ct_factor> to 3 to match the number of blades (got hi from the 208B)
I think your prop file is much better than the aeromatic one !

But can you explain to me what the vertical numbers of the CP and CT tables mean (I mean the first column). And for the CP table I also would ike to know what the first row is referencing - thrust ? torqu ?

[S&J]

Dany is the prop you've modelled the McCauley Constant Speed Propeller D3A34C402/90DFA-10 ?

If so it's a 400 series.... Which is "The C400 series - three-bladed constant speed non-feathering propellers"