NZWW

Uncommanded nose dive with AP engaged

Recommended Posts

In the last few days I've been experiencing sudden and rapid uncommanded nose dive in excess of 5000 FPM with either VNAV or APP engaged. Happened twice during descend, final approach and once in climb (three separate flights, PC rebooted in between). AP follows FD bars (!) during this dive (so rather it is "commanded nose dive"). Following AP disconnect and subsequent engagement, aircraft follows normal vertical path. I have service-based failures engaged, but they show no active failures. I'm very experienced user of PMDG B737NGX, so I doubt this is caused by mismanagement on my behalf.

 

Has anyone experienced something of this nature too?

 

 

Thanks

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

I suspect it's failing yoke sending input signals, as CWS mode persists on FMA throughout. I increased null zones for elevator through FSUIPC, going to check in the coming days.

Share this post


Link to post
Share on other sites

Just completed two separate flights without issues. No other indication in the forums over the last 30 days.

 

Video of it happening maybe? A weird axis issue with FSUIPC?

 

Full names please in the PMDG forums. 

Share this post


Link to post
Share on other sites

I experience something similar when I was too high on approach and the autopilot was trying to acquire the glideslope from above.  I disconnected the autopilot and went around, but probably had a few pax with whiplash.

 

Only happened to me on final, not really at any other stage of flight, except when I was being tossed around by the weather.

Share this post


Link to post
Share on other sites

Any of you have ASUS motherboards?

 

Indeed.  However, I figured mine was a result of bad piloting/atc (ending up above the G/S), NOT a design flaw.  That is the ONLY time I've experienced it, and it performed as expected, as the NGX has at all other stages of light, I don't have any complaints.

Share this post


Link to post
Share on other sites

ASUS motherboards seems to have had issues with CMOS batteries and BIOS versions for a while now. Usually replacing the CMOS battery fixes the issue. Occasionally, a BIOS flash is required.

 

Basically, if the voltage gets weird, the HPET can get off, and when you're trying to time very precise events off of a clock, that clock needs to be precise itself. If the clock gets weird, well...you've seen the result.

Share this post


Link to post
Share on other sites

Having tweaked FSUIPC (increased elevator null zone and ticked "control spike elimination") and completed 3 flights, it indeed seems to be yoke issue. Another reason always to be on guard and take over.

 

Not an ASUS motherboard, btw.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now