[Solved] N1 thrust falling back on takeoff

[flyingfudge]

I'm having a problem on every take off. The ATS increases to full thrust on the take off roll but on take off ( appx 500ft ) the thrust suddenly starts rolling back and the aircraft approaches the stall.

I've tried different airframes etc. with the same result. I've attached my log ( please advise if there's a more informative file I should upload ) and a pic of the situation.

Thanks ....

Log.txt

Edited January 12, 2022 by Graeme_77

[Graeme_77]

The issue here is the ATS system is in speed mode, and the target speed is 127 kts, so it has made a power reduction.

Being aware of the flight mode annunciators or “FMAs” is key to flying a complex aircraft. It doesn’t matter what buttons are pressed on the panel, only the modes showing in the FMA strip and ATS panel. In this case you can see LNV1 and PITCH, with ALTS armed and ATS SPEED.

The reason this particular issue has occurred is with LNV1 armed before takeoff, at 400ft the aircraft swaps from TO/TO to LNV1 and PTCH, but the vertical change from TO to PTCH results in a more subtle change on the ATS panel from “N1 TO” to “SPEED”, when the adjusts the thrust to follow the speed target. It’s more obvious in a real jet where the thrust levers move, but Airbus pilots with detent levers are conditioned to be aware of that thrust mode annunciator at all times, it’s the only proper way to tell what the automation is trying to do, so very similar to sim hardware in that regard.

For takeoff we recommend speed be selected to 200 kts, or the departure speed limit if more limiting. Keep an eye on the ATS panel and you’ll see it swap to N1 mode when using TO or FLC, and SPEED mode when using VS, PTCH or ALT.  

Edited January 12, 2022 by Graeme_77

[Andydigital]

You are in SPEED mode which is indicated by the blue marker on the speed tape and SPEED in the ATS display, it’s also only set to 127knots. The ATS display should show N1-TO if you were in the correct mode. 
 

edit I’m too slow too lol

Edited January 12, 2022 by Andydigital