ERJ-145 sudden altitude jump

[airernie]

I flew from KMEM to KSDF today on VATSIM and during the flight I had two instances where the autopilot was active and I had several thousand feet jumps in altitude.

 

One was where i about 2000' below my target altitude of 28000' and climbing.  The aircraft suddenly jumped from appoximately 26000' to the target altitude.

 

On the second occasion I was at cruise altitude and the aircraft jumped from 28000' to 32500'.  Enough of a change that I got a call from ATC.

 

This isn't the first flight that this has happened on.

 

FSX and all related files are installed on a separate drive from my OS.  I'm running Win 7 Pro and UAC is off.

 

Any known casuses, fixes, etc?

[scoobflight]

what does 'jump' mean ... aircraft, in less than one second, was at a new altitude?  aircraft climbed normally to an uncommanded altitude?  other?

[airernie]

Thanks for responding.

 

Both jumps were fairly instantaeous.  The second jump was from a cruise altitude of 28000' to 32500' in a second or two.  Both went extreme nose up.  Nothing but sky in the windscreen.

 

I had to disengage the AP and reduce thrust to regain control and get the aircraft back to the captured altitude setting in the PFD.  Once there, I engaged the AP and it held fine the remainder of the trip at that altitude.

 

I'm going to do a bit more testing with the 'Use default autopilot for altitude hold' in the ERJ config dialog unchecked to see if that has any effect.

 

Ernie

[scoobflight]

this is a fault in the FS weather engine ... the atmospheric pressure changed and therefore your altitude.  there is no fault in the ERJ.

[airernie]

Thanks for the reply.  

 

A new experience since in the past I've only done GA and flown a lot closer to the ground.