Strange Behavior

[liketofly1 11]

Hi Captains,

 

Honestly, I don't really know where to start:

I was on a routine flight from VTBS Bangkok to LOWW Vienna, at cruise alt. Everything seemed nice and quiet - when all of a sudden I get a caution light and the airplane started a slight uncommanded climb. I was at FL320, disengaged the AP and arrested the climb and decended back to my FL320 however - (mind you I have no failures activated) as soon as I commanded ALT HOLD, on the MCP nothing happened - and from there on - ANY input to the MCP was disregarded by the Aircraft - yes, I could manually fly the plane and it responded to joystick imput as it should, however - neither HDG Sel - HDG Hold - FLCH - ALT Hold - nor VS/FPA just nothing I commanded via the MCP was followed by the Aircraft - although the correct modes where also reflected in the PFD's FMA. Neither AP nor A/T where responding although the lights - switches - and diales in the MCP reacted as required - just the plane did not follow anything except handflying......... and honestly I like handflying but not for a 9+ hour long haul....

 

All Instruments showed normal behavior and VAS was well within limits - so I'm at a real loss here  - had to land at VIBN Varanasi and restart the Simulator - after that - everything is working again.... really strange.

 

Any ideas what could have caused that very strange behavior? Any tip how to get the systems to respond again if this should happen again? No fun if one needs to re-start FS and do a fresh flightplanning from the alternate airport.......

 

Anyhow - if it happens again I will file a ticket with the support page......

 

Kind regards

[donkey20048 19]

With the unexpected climb do you have autostep climbs on? As this will change and climb the plane without your approval at certain points along flight plan

 

Could a corrupt or out of date panel state cause your other issues?

[downscc 1,327]

This might be (and I am just offering my best guess) related to the problem that SP1c will fix, to be sure where you using time acceleration such as x4 or x8?

 

The last time I had a hiccup, they've been far and few between, I left her in SPD LNAV VNAV PATH mode as shown on FMA then reset the course to the next fix. To do this, select the LSB next to next fix (LSB 1) and the fix will be copied to the scratchpad line. Then click the same LSB again and the EXEC button will light. Press the EXEC button and the course to next fix has been reset. Give it a try if this rarity happens to you again.

[liketofly1 11]

Hi everybody, 

 

thanks for your replays.....

 

With the unexpected climb do you have autostep climbs on? As this will change and climb the plane without your approval at certain points along flight plan

Could a corrupt or out of date panel state cause your other issues?

 

I'm pretty sure it has nothing to do with Autostepclimb as this function is deactivated - and with a slight climb I meant a 200 - 300 fpm climb, stepclimbs should be of a higher climb rate.

 

This might be (and I am just offering my best guess) related to the problem that SP1c will fix, to be sure where you using time acceleration such as x4 or x8?

 

The last time I had a hiccup, they've been far and few between, I left her in SPD LNAV VNAV PATH mode as shown on FMA then reset the course to the next fix. To do this, select the LSB next to next fix (LSB 1) and the fix will be copied to the scratchpad line. Then click the same LSB again and the EXEC button will light. Press the EXEC button and the course to next fix has been reset. Give it a try if this rarity happens to you again.

 

Unfortunately no, I was not using time acceleration as it was a VATSIM online flight (mind you, no controllers around, but anyway) - thanks for your suggestion with the FMC - that in fact is one thing I did not try to change the FMC waypoint.....will do so if it happens again - because as you said - I'm not really used to those hiccups as they are so rare....

 

kind regards

[scandinavian13 5,192]

Hardware trim axis?

[liketofly1 11]

Hardware trim axis?

 Hi Kyle,

 

What do you mean by hardware trim axis ? Handflying worked as it should, only the trim bug on the pfd - did not respond although the aircraft trimmed as it should - it just did not follow MCP inputs.... and I did not try to change anything via CDU of FMC......

 

I diverted safely to VIBN without problems.... exept I had to handfly the whole time until landing - after a restart of the computer - everything was fine again....

 

regards

Richard Oberwinkler

[scandinavian13 5,192]

 

 

What do you mean by hardware trim axis ?

 

I mean, literally, an axis on your hardware that is bound to the trim function.  This would be similar to a trim wheel, or something you physically move up and down (or along some scale - up/down, left/right, etc).  An example would be the knob/wheel on top of the throttle of the X-55 (here).

 

For what it's worth, the sim tries to assign functions to random buttons/switches when it sees hardware, so even if you didn't set a trim axis, you might want to check your assignments in the FSX menu to ensure it didn't randomly assign one to a slider or knob on your hardware (the CH Yoke has a black wheel where the yoke connects to the base that the sim will automatically set as a trim wheel).

 

Regardless, if you do not zero out any hardware trim before trying to put the AP on, it might connect, but it might randomly kick off because the hardware will override the in-sim trim value, which will tick the AP off.

 

 

 

Handflying worked as it should, only the trim bug on the pfd - did not respond although the aircraft trimmed as it should - it just did not follow MCP inputs.... and I did not try to change anything via CDU of FMC......

 

Not sure what you're getting at, here.

 

The trim bug should only be displayed when not using the autopilot - AND - it is not commanded by the MCP at all.  The speed in the MCP window does not drive the commanded trim reference speed at all.  This is the whole reason the TRIM REF BUG is even an option in the PMDG SETUP menus.

[Mike Ionas 5]

Hi Captains,

 

Honestly, I don't really know where to start:

I was on a routine flight from VTBS Bangkok to LOWW Vienna, at cruise alt. Everything seemed nice and quiet - when all of a sudden I get a caution light and the airplane started a slight uncommanded climb. I was at FL320, disengaged the AP and arrested the climb and decended back to my FL320 however - (mind you I have no failures activated) as soon as I commanded ALT HOLD, on the MCP nothing happened - and from there on - ANY input to the MCP was disregarded by the Aircraft - yes, I could manually fly the plane and it responded to joystick imput as it should, however - neither HDG Sel - HDG Hold - FLCH - ALT Hold - nor VS/FPA just nothing I commanded via the MCP was followed by the Aircraft - although the correct modes where also reflected in the PFD's FMA. Neither AP nor A/T where responding although the lights - switches - and diales in the MCP reacted as required - just the plane did not follow anything except handflying......... and honestly I like handflying but not for a 9+ hour long haul....

 

All Instruments showed normal behavior and VAS was well within limits - so I'm at a real loss here  - had to land at VIBN Varanasi and restart the Simulator - after that - everything is working again.... really strange.

 

Any ideas what could have caused that very strange behavior? Any tip how to get the systems to respond again if this should happen again? No fun if one needs to re-start FS and do a fresh flightplanning from the alternate airport.......

 

Anyhow - if it happens again I will file a ticket with the support page......

 

Kind regards

I faced exactly the same problem today for the second time in the last couple of weeks. Although the A/P is on and all modes are announciated correctly on the FMA it does not control the aircraft. No other modes are working as well, but all instruments appear to be fine and I can hand fly the aircraft without any issues. It is as if the A/P does not have any control over the aircraft.. Only strange behavior was that the A/P disconnect horn does not sound when the I disconnect the A/P (via the A/P discon button) but the warning does appear normally on the master warn button. I will file a ticket as this is the second time this is happening..

[liketofly1 11]

I faced exactly the same problem today for the second time in the last couple of weeks. Although the A/P is on and all modes are announciated correctly on the FMA it does not control the aircraft. No other modes are working as well, but all instruments appear to be fine and I can hand fly the aircraft without any issues. It is as if the A/P does not have any control over the aircraft.. Only strange behavior was that the A/P disconnect horn does not sound when the I disconnect the A/P (via the A/P discon button) but the warning does appear normally on the master warn button. I will file a ticket as this is the second time this is happening..

 

Hi Mike,

 

Hasn't happened to me anymore since that time - however, if it happend again I'll also file a ticket - I'd need to collect some info though since  I didn't collect enough info on the failure (log files etc. to substantiate the problem) at that time....

 

regards

[Mike Ionas 5]

Hi Richard,

 

In my case it was the second time after 25-30 flights without issues, therefore I raised a ticket just in case PMDG can pinpoint the cause and since I had all the info fresh..

 

Regards,

[liketofly1 11]

Super if you took a system screenie...... 

 

If they can pinpoint it - or already have some reports in this regard and are working on a solution for 1c - and get back to you, please be so kind and post it here, so anyone with this problem stays informed....

 

kind regards