[Solved] ATC turned off while climbing

[leha74ru]

apparently slowly gaining altitude, TAT -55. decreased, but I have no idea how to revive the ATS

Edited January 18, 2022 by leha74ru

[Rastuasi]

Might change your title  

To answer your question, I come across this regularly. What I do is the following:

1. Switch off FLC mode to VS and lower it initially down to 500 ft/min.
2. Reset the ATS using the disconnect commands.
3. Watch the IAS indicator, once it gets closer to the actual set speed, you should be able to turn on ATS again.

What I find to be the issue is when the N1 cannot be matched for the same speed. I end up in a super high AOA and the speed slowing down as it tries to keep the VNAV.  It is similar to previous posts by Graeme where he states "lower the nose, get the speed up and then re-engage". Do note, on some climbs, I cannot go back into FLC mode at all, it immediately has problems. So I just monitor the N1 and if ATS is holding the 250/M.72 IAS at a lower than N1 max (purple value) then I add a few hundred FPM to the climb. Eventually she levels off and all is golden and I can go back fully into ATS. Only once at 40k, did I have to actually lower the overall speed from M.80 to M.78 due to the same issue.