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#2721 MP properties engines/engine[*]/n{1,2} not overrideable

2020.3
New
nobody
None
Low
2022-04-13
2022-03-29
No

There is no way to reconnect engines/engine[*]/n{1,2} to FDM properties other than fdm/jsbsim/propulsion/engine[*]/n{1,2}, this probably also affects YASim.

Firstly, these properties are MP-enabled. Secondly, they, at least for JSBSim FGTurbine, have no physical meaning because they are the referred speed N_r = N * sqrt(T_0 / T), T_0 = 288 K that stays constant with flight regimes (which is not the case for the mechanical RPM N., and if you use those properties for animations or sounds they will be off at high altitudes or speeds, so you have to transmit the mechanical RPM and also thrust norm for the thrust noise, which would be other properties. Thus these properties are just being transmitted in vain in most cases. If they could be reconnected, they could have been used for the mechanical RPM and thrust.

Discussion

  • Anonymous

    Anonymous - 2022-03-29

    Related discussion in JSBSim repo, which concluded that the problem is FG-side: https://github.com/JSBSim-Team/jsbsim/discussions/210

     

  • Anonymous

    Anonymous - 2022-03-29
    • summary: engines/engine[*]/n{1,2} not overrideable --> MP properties engines/engine[*]/n{1,2} not overrideable
     

  • Anonymous

    Anonymous - 2022-03-29
    • Description has changed:

    Diff:

    --- old
+++ new
@@ -1,3 +1,3 @@
 There is no way to reconnect `engines/engine[*]/n{1,2}` to FDM properties other than `fdm/jsbsim/propulsion/engine[*]/n{1,2}`, this probably also affects YASim.

-Firstly, these properties are MP-enabled. Secondly, they, at least for JSBSim FGTurbine, have no physical meaning because they are the referred speed `N_r = N \sqrt{\frac{T_0}{T}}, T_0 = 288 K` that stays constant with flight regimes (which is not the case for the mechanical RPM `N`., and if you use those properties for animations or sounds they will be off at high altitudes or speeds, so you have to transmit the mechanical RPM and also thrust norm for the thrust noise. Thus those properties are just being transmitted in vain in most cases.
+Firstly, these properties are MP-enabled. Secondly, they, at least for JSBSim FGTurbine, have no physical meaning because they are the referred speed `N_r = N * sqrt(T_0 / T), T_0 = 288 K` that stays constant with flight regimes (which is not the case for the mechanical RPM `N`., and if you use those properties for animations or sounds they will be off at high altitudes or speeds, so you have to transmit the mechanical RPM and also thrust norm for the thrust noise. Thus those properties are just being transmitted in vain in most cases.
     

  • Anonymous

    Anonymous - 2022-03-29
    • Description has changed:

    Diff:

    --- old
+++ new
@@ -1,3 +1,3 @@
 There is no way to reconnect `engines/engine[*]/n{1,2}` to FDM properties other than `fdm/jsbsim/propulsion/engine[*]/n{1,2}`, this probably also affects YASim.

-Firstly, these properties are MP-enabled. Secondly, they, at least for JSBSim FGTurbine, have no physical meaning because they are the referred speed `N_r = N * sqrt(T_0 / T), T_0 = 288 K` that stays constant with flight regimes (which is not the case for the mechanical RPM `N`., and if you use those properties for animations or sounds they will be off at high altitudes or speeds, so you have to transmit the mechanical RPM and also thrust norm for the thrust noise. Thus those properties are just being transmitted in vain in most cases.
+Firstly, these properties are MP-enabled. Secondly, they, at least for JSBSim FGTurbine, have no physical meaning because they are the referred speed `N_r = N * sqrt(T_0 / T), T_0 = 288 K` that stays constant with flight regimes (which is not the case for the mechanical RPM `N`., and if you use those properties for animations or sounds they will be off at high altitudes or speeds, so you have to transmit the mechanical RPM and also thrust norm for the thrust noise. Thus those properties are just being transmitted in vain in most cases. If they could be reconnected, they could have been used for those.
     

  • Anonymous

    Anonymous - 2022-03-29
    • Description has changed:

    Diff:

    --- old
+++ new
@@ -1,3 +1,3 @@
 There is no way to reconnect `engines/engine[*]/n{1,2}` to FDM properties other than `fdm/jsbsim/propulsion/engine[*]/n{1,2}`, this probably also affects YASim.

-Firstly, these properties are MP-enabled. Secondly, they, at least for JSBSim FGTurbine, have no physical meaning because they are the referred speed `N_r = N * sqrt(T_0 / T), T_0 = 288 K` that stays constant with flight regimes (which is not the case for the mechanical RPM `N`., and if you use those properties for animations or sounds they will be off at high altitudes or speeds, so you have to transmit the mechanical RPM and also thrust norm for the thrust noise. Thus those properties are just being transmitted in vain in most cases. If they could be reconnected, they could have been used for those.
+Firstly, these properties are MP-enabled. Secondly, they, at least for JSBSim FGTurbine, have no physical meaning because they are the referred speed `N_r = N * sqrt(T_0 / T), T_0 = 288 K` that stays constant with flight regimes (which is not the case for the mechanical RPM `N`., and if you use those properties for animations or sounds they will be off at high altitudes or speeds, so you have to transmit the mechanical RPM and also thrust norm for the thrust noise. Thus those properties are just being transmitted in vain in most cases. If they could be reconnected, they could have been used for the mechanical RPM and thrust.
     

  • Anonymous

    Anonymous - 2022-03-29
    • Description has changed:

    Diff:

    --- old
+++ new
@@ -1,3 +1,3 @@
 There is no way to reconnect `engines/engine[*]/n{1,2}` to FDM properties other than `fdm/jsbsim/propulsion/engine[*]/n{1,2}`, this probably also affects YASim.

-Firstly, these properties are MP-enabled. Secondly, they, at least for JSBSim FGTurbine, have no physical meaning because they are the referred speed `N_r = N * sqrt(T_0 / T), T_0 = 288 K` that stays constant with flight regimes (which is not the case for the mechanical RPM `N`., and if you use those properties for animations or sounds they will be off at high altitudes or speeds, so you have to transmit the mechanical RPM and also thrust norm for the thrust noise. Thus those properties are just being transmitted in vain in most cases. If they could be reconnected, they could have been used for the mechanical RPM and thrust.
+Firstly, these properties are MP-enabled. Secondly, they, at least for JSBSim FGTurbine, have no physical meaning because they are the referred speed `N_r = N * sqrt(T_0 / T), T_0 = 288 K` that stays constant with flight regimes (which is not the case for the mechanical RPM `N`., and if you use those properties for animations or sounds they will be off at high altitudes or speeds, so you have to transmit the mechanical RPM and also thrust norm for the thrust noise, which would be other properties. Thus these properties are just being transmitted in vain in most cases. If they could be reconnected, they could have been used for the mechanical RPM and thrust.
     

  • James Turner

    James Turner - 2022-04-13

    I'd maybe raise this on the mailing list about best way to decouple these without breaking anything? I had something similar for autobrakes years ago, had ot basically add an intermeidate property.

    Code should be in FDMshell.cxx so doesn't need an internal JSBSim change I hope.

     

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