Unable to override Commanded N1 on a Jet engine

[MSFS 2024] Bug Reports Aircraft
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1

Version: 1.6.30

Frequency: Consistently

Severity: Blocker
**
Context:** flight

Bug description:

I am unable to override TURB ENG COMMANDED N1 at all, neither TURB ENG THROTTLE COMMANDED N1, the documentation indicate these variables are writable, but I cannot achieve it at all:

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image1093×110 12.2 KB

This is quite crucial, since to write custom FADEC Computers, we receive the data of the target N1%..

Either the documentation is wrong, or the variables are not posible to be overriden, something here is missing..

I can override Corrected N1, but this will not drive N2% leading to having to feed N2% too, but that data is not available on any POHs IRL, it is always N1% only.

**Repro steps:
**
This code on a jet engine will fail to override the vars as per documentaiton:

		<UseTemplate Name="ASOBO_GT_Update">
			<FREQUENCY>120</FREQUENCY>
			<UPDATE_CODE>
					90 (&gt;TURB ENG COMMANDED N1:1, Percent)
					90 (&gt;TURB ENG COMMANDED N1:2, Percent)
			</UPDATE_CODE>
		</UseTemplate>

Best,
Raul

1 Like
2

Hello Raul,

Yes, you are correct: despite both SimVars you mentioned (TURB_ENG_COMMANDED_N1 and TURB_ENG_THROTTLE_COMMANDED_N1) being documented as writable in the SDK, writing to either of them currently has no effect. Our investigation confirmed that the simulation code ignores externally written values and overwrites them every timestep.

To preserve the existing behavior and maintain backward compatibility, while allowing the TURB_ENG_COMMANDED_N1 SimVar to be used as an input, a new SimVar named TURB_ENG_COMMANDED_N1_OVERRIDE_ACTIVE has been added. It dynamically enables external control of commanded Ne for the indexed turbine engine as follows:

  • When true, the value written to TURB_ENG_COMMANDED_N1 is used as commanded Ne (effectively as uncorrected commanded N1), bypassing the internal commanded Ne calculation.
    TURB_ENG_THROTTLE_COMMANDED_N1 is also updated with the same value.
  • When false, which is the default, commanded Ne continues to be calculated internally by the turbine engine code, so the existing behavior remains unchanged.

Please note that writing to TURB_ENG_THROTTLE_COMMANDED_N1 will continue to have no effect, and this SimVar will therefore be marked as non-writable in the SDK starting with SU6.

All of these changes will be introduced with SU6, starting with SU6 Beta 1.8.9.0.

I hope this will allow third-party developers to implement custom FADEC or other external engine-control logic.

Please let us know if you have any questions.

Best regards,
Andrey / Asobo

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Turbine heli clutch