Thrust limit goes blank during cruise

[Bjerko]

Hello.

Came over an odd problem during cruise which I have never had on any of my numerous previous flights.

As I was crusing along at FL380, I suddenly noticed (after cruising for an hour) that ATS was flashing "FAIL", I cleared the message and tried to re-engage the ATS without any luck. Going to the FMS, I noticed that all the thrust limits was gone for no apparent reason. With blank I mean that TO, CLB and CRZ had no numbers in them, no text or numbers, just blank. However MCT had a number in it, but selecting it just resulted in it being automatically deselected.

Once I started my decend, reaching about FL350 all my thrust limits restored and I could resume the usage of ATS.

So I am a bit confused of what went wrong for this flight, any ideas?

[L1ntzi]

It has probably been too cold for the engines and ATS hasn't been able to keep up with the requested power. If temperatures are below ISA -10°C at high altitudes that can happen. I experienced this also today around FL380 with ISA -16°C. Descended to FL360 and it was then fine.