I was wondering does a compressor variable geometry and a inlet variable stator vane share any similarities or does these terms have same meanings?

I did some digging and all I could find is that CVG is most applicable to turbochargers like the ones you'd find on cars.

However, the term 'CVG scheduling and control' was mentioned as part of a FADEC control output in my gas turbine engine module.

It states that "the FADEC stores a schedule of CVG position versus corrected N2 so as to achieve optimum compressor efficiency. CVG position feedback fed from the CVG actuator on the engine is compared with the CVG demand to achieve a closed loop control. Thus, the inlet guide vanes and the first 5 stages of the CVG are controlled"

This statement rises another question because I do understand that a inlet variable stator vane can aid to change the angle of the incoming air which is passing through the engine and therefore it can manipulate the pressure which is at the inlet and this VSV are controlled by actuators (purposely to minimise compressor stalling effect).

Now how does the CVG fit into this context, is it a system that is solely utilized by the FADEC in order optimise the AOA of the IVGVs? And if so, why is that if the total engine pressure exceeds its limit(which I know that in such condition the EGT has increased), the CVG would be turned off to compensate for air control. Shouldn't the Fuel control unit decrease the flow of fuel into the burners?

I know these is quite a mouthful but if any one can answer or at least shine some light I'd appreciate it.

  • 1
    $\begingroup$ Welcome to Aviation Stack Exchange. Please limit your question to a single question, without any "in addition..." secondary questions. Also, please specify which engine your question refers to; the mechanism you're referring to isn't universal. $\endgroup$
    – Ralph J
    Commented Jun 21, 2023 at 12:17
  • $\begingroup$ I haven't made an attempt as yet to find which engine has this mechanism but it was during our gas turbine engine module(aircraft engine) especially when we were digging into FADEC I came across this term 'CVG'. This question came out from EASA examation and I wanted to know if anyone would know the difference with the variable stator vanes and the CVG and how CVG and the total engine pressure operates.The question stated that if the engine pressure ratio exceeds its limit value what would happend? And the correct answer was that the CVG system would close inorder to compensate for airflow $\endgroup$
    – Ludwig T
    Commented Jun 21, 2023 at 12:28
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    $\begingroup$ Do you have any reason to think compressor variable geometry is not the generic wording encompassing all features used to adjust the compressor geometry and remain at the engine design point: VIGV, VSV, VBV? See this thesis, e.g page 24. $\endgroup$
    – mins
    Commented Jun 23, 2023 at 10:30
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    $\begingroup$ Ralph, I can't thank you enough for the information. Upon reading it and reflecting on this diagram I have with me(how the FADEC receives inputs and then sends one of its output to the CVG in order to compute the optimal performance of an aircraft) I am convinced this CVG is a system that FADEC uses to manipulate the VIGVs. Thank you much $\endgroup$
    – Ludwig T
    Commented Jun 23, 2023 at 18:23


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