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I cannot get Autothrust to work. I got rid of the FAIL message on the ATS window, but I cannot activate ATS whatsoever.

I push it on Ground or in Flight with VNAV enabled, but whatever I try, Autothrust will not come on, ATS pushbutton is not lit.

Can anybody explain to me, what the condotions exactly have to be to get ATS working?

I am sure I forget something to activate, but I don't know what it is.

Help is much appreciated!


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  • Pils pinned this topic

Same problem here, in flight FAIL message, I pull the CB (G7) in and out and push ATS again and FAIL message is back. 

But at_disc in the bindings brings ATS back to life.



Edited by J@nek
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I followed the checklist and came to the After Start Checklist point ATS….N1 TO. 

I don’t have it as you see in the image. 

on the top right the checklist says 1 Action. Can I do something there to make the F/O does the correct switch. 
obviously something is missing here. 


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The tooltip asks you to make sure the ATS display shows something. First step would be to look at the ATS display ;)

Just this once, I'll try not to be too unhelpful: the ATS display is to the left of the autopilot controls and left of the captain's master caution/warning indicator, above the primary flight display.

Edited by Rodeo
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You’re asking for takeoff power, cowl anti ice, while running the packs on the engines. IIRC this is not allowed. The procedures show takeoff and landing with the APU running and supplying the packs. There are options for cowl, or 10th stage, but not both.

Also TOGA will not rearm ATS when the flight directors are displayed. You need to remove the flight directors, then press TOGA. This is a real quirk of the Challenger.


Edited by Graeme_77
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5 hours ago, Stevens said:

Thanks Rodeo, but I in fact know where the ATS window is. 

Maybe you or hopefully the developers could explain the system behavior in the following video. 
I cannot believe this is normal…

This is indeed normal. The reason is quite simple: the ATS needs an N1 limit target to operate. Otherwise, it would have no idea what the maximum allowable thrust is. This value is supplied by the FMC. The FMC uses performance tables made by the aircraft manufacturer to determine what the takeoff thrust limit is supposed to be and if I show what the table looks like, you'll immediately see the source of the problem:


Your SAT is +35 C. At that temperature, the FMC has no data to compute a takeoff N1 target, so the target blanks and the ATS goes to FAIL (and cannot be re-engaged). Take the cowl A/I off, FMC goes back to the normal takeoff tables and voila, ATS is back in business.

Edited by skiselkov
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