So I'm wondering, when the engine runs at idle and the pilot sets a higher thrust level, what exactly happens, that the EEC/FADEC recognizes, that I want to accelerate? My professor said, it's anticipating the upcoming acceleration through:

  • $TRA > TRA_{threshold}$
  • $pt_3 < pt_{3_{min}}$ (cabin bleed)
  • $N2/\sqrt\theta < N2/\sqrt\theta_{idle}$ with $\theta = Tt2/T_{t ref}$

I get that the TRA (throttle lever angle) is higher than my previous one, hence I just raised it. But why exactly would pt_3 be lower than pt3_min, and why is $N2/\sqrt\theta$ smaller than idle? That would indicate that Tt2 has increased.

You probably need to go ask your professor for clarification. But let's look at it this way: what would it mean if $Pt3 > Pt3_{min}$ and $N2/\sqrt{\theta}>N2/\sqrt{\theta}_{idle}$. It means that the engine is probably NOT at idle. So in that situation, if you move the throttle, you probably do want to increase thrust, but not from idle. The EEC may have different control schedules for idle vs above idle operation.

Your Answer


By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.