Autopilot banking oscillation

[Czar]

Hello. I've been enjoying your product as well as reading about the future work on the VNAV and related systems.

I've searched about this issue without getting any results. Sorry if it's a duplicated report.
I've been noticing an unusual oscillation on the banking when the auto pilot encounters a open turn on the flight path given the route characteristics.

The route flown is a SID from KLAS called BOACH SEVEN from runway 07L between BAKRR and MINEY. SID route: https://skyvector.com/files/tpp/1708/pdf/00662BOACH.PDF This behavior is also seen on different navigation paths that features such open turns.

A recording follows in this link:

I'd like to know if it's a normal behavior on the autopilot when encountering such turns transferring the blame onto the FMC plotting such turns incorrectly (I know it's unlikely, but I'm not a programmer) or is something like the AP is shifting between bank angles values to keep itself on the Nav Path.

Appreciated your product.

EDIT: Turbulence were absent.

Edited August 5, 2017 by Czar

[Litjan]

Hi,

this type of oscillation is normal for our product - it is a byproduct of the route being really just a sequence of points, not an actual curve. So the autopilot is really following a number of straight segments that make up the curve. The algorithm to make the plane follow a complex lateral part in various conditions (speed, wind, etc.) is fairly complex and always a trade-off between accuracy and smoothness.

Cheers, Jan