Altitude hold in cruise fluctuating

AlexEtz

Dear JF team,

I spotted a strange bug when I decided to fly a LRC cruise at Mach 0.6 FL280, the aircraft is unable to maintain altitude with HOLD mode, it is fluctuating since I am stable at FL280, meaning more than 1 hour. Here a video to illustrate;

https://youtu.be/9XEn5F3Of0w

In the video you can also see me trying to compensate the fluctuation with my joystick and even the trim, with no success.

Cheers,

Alex

AlexEtz

edit: if I deactivate the pitch switch blue button, stabilize and trim manually, reactivate the pitch control, it seems to retrieve a stable flight for a few minutes then it start to fluctuate again.

Kenzo

Are you on the newest version? I’ve had this problem with a prior version, I think 1.2.

Mark

We are aware of the tendency of the aircraft to porpoise at low weights when the 'GPS Navigation' option is not selected on the EFB and it is something we are looking into.

Unfortunately, it's a tricky issue to fix as we are currently supporting two different navigation systems (traditional navigation, and GPS navigation with the Working Title GNS530) that both have two independent autopilot systems that work in completely different ways and are fighting against each other for control of the aircraft, so we have had to set up the F28 to work the best it can with both options. We explain this in more detail in a previous forum post if you'd like to read more into this: https://community.justflight.com/post/26060

Improvements are ongoing with this though, and just in the last few days our flight model developer has been working on some improvements to the flight model that should reduce this tendency. We'll be sure to release an update to the F28 as soon as we have this one improved, as it's a bugbear I would personally love to see improved too.

Mark - Just Flight

AlexEtz

Okay, interesting! Thanks for the info Mark!

AlexEtz

Hey @Mark , I didn't had this issue since a long time... maybe last MSFS updates fix it. I will report it back if I see any fluctuations again.

Smarticus

Just to add, unfortunately the Xbox version is suffering from this constant pitch up and down also.
Any altitude you put in once it reaches that, the pitch up and down starts, just like in the OP video posted in Feb, the only solution I have found is to click the GPS option and it stabilises immediately. Is there any further news on an update?

thanks

Mark

We have a large "Version 2" update to the F28 Professional currently in development and there will be some autopilot improvements included with that update.

Full details on the F28 Professional Version 2 update can be found here.

Mark - Just Flight

AlexEtz

Hey, thanks to the team and you Mark for listening to the feedbacks. Can't wait for this nice update and fly with a FMC! Good luck with the rest of the work