Hi guys, I had a weird problem last night I haven't experienced before. Was cruising on autopilot but the plane just kept rocking up and down. There was a tail wind but no turbulence. I panned to an outside view and it looked like my elevators were trying to push the plane down while the autopilot was trying to keep the plane up ( or vice versa
), and I kept getting an "altitude warning".  Later on I noticed that the trim tab to the left of the speed brake lever was set at zero. I then adjusted it to around 2.5 (as it was at take-off) and it seemed to stabilise things. No idea how it got to zero. I must have accidently moved it somehow without realising? And if I did adjust it accidently should it not have adjusted itself to stabilise the plane automatically? Excuse any ignorance here, just trying to figure out what happened.

 

I have 5 minutes of it on twitch where you see the rocking and outside view of the elevators. You can see it here http://www.twitch.tv/troykr/b/524465683

Hi, Troy,

 

I don't think you are having a trim problem -- looks like elevators are just trying to compensate for pitch changes caused by something else.

 

I notice you are at 40,000 ft.  What is the FMC displaying for optimal and max altitudes?  Also, I can't quite make out the TAT on the EICAS.  What is it?

 

Mike

Hi Mike thanks for your help. Ummm I had selected short range fuel option and set my altitude to 38,000ft but it auto step climbed on its own to 40,000 shortly after reaching cruise. Can't exactly remember Max/Optimal, but it was about 39,000 and I did lower to that flight level but the rocking continued. TAT, umm I wasn't paying attention to it last night but I make it out at -24c. Does that sound right?

 

p.s. I am flying again tonight and the problem has not repeated. Last night was NZDN (Dunedin) to NZAA (Auckland). Tonight NZAA (Auckland) to NTAA (Tahiti).

Right now I'm at 38,000 with TAT -22c and about to step climb to 40,000. Flying nice and smooth tonight so far.

Hi, Troy,

 

TAT looks OK -- sometimes weather engines inject temps like +35C at high altitude, which causes performance problems (though not exactly like yours). 

 

I'm puzzled by this -- don't recall seeing it before described on this forum and haven't experienced it.

 

Only other things I can think of, if it should happen again:

1) Are you using the PMDG loader to load fuel and payload?  If not, possibly the weight distribution is off.

 

2) Is the aircraft very lightly loaded?  Maybe there is some bug that shows up at high altitudes and very low gross weights.

 

3) It doesn't look like you have any failures -- if you have failures set try turning them off. 

 

4) Maybe it is an issue with auto step-climb or auto acceleration, although, again, you don't appear to have an increased sim rate.

 

Hope this is of some help!

 

Mike

Hi, Troy,

 

TAT looks OK -- sometimes weather engines inject temps like +35C at high altitude, which causes performance problems (though not exactly like yours). 

 

I'm puzzled by this -- don't recall seeing it before described on this forum and haven't experienced it.

 

Only other things I can think of, if it should happen again:

1) Are you using the PMDG loader to load fuel and payload?  If not, possibly the weight distribution is off.

 

2) Is the aircraft very lightly loaded?  Maybe there is some bug that shows up at high altitudes and very low gross weights.

 

3) It doesn't look like you have any failures -- if you have failures set try turning them off. 

 

4) Maybe it is an issue with auto step-climb or auto acceleration, although, again, you don't appear to have an increased sim rate.

 

Hope this is of some help!

 

Mike

 

1) yes

2) default payload

3) service based failures on

4) i have auto step-climb on.

 

Re wx engine I use ASN with all hot fixes.

 

Yea it's an odd one. No such problem last night though. I'll report back here if it happens again.

Aware you using any hardware trim? Saitek trim wheel or something of the sorts? I had a friend have this happen to him because of the hardware trim wheel.

Hi David,

 

I'm using the FLY 5 Joystick http://www.cyborggaming.com/prod/v5stick.htm

and I have it configured through FSUPIC.

Thrusters, ailerons, rudder, elevators. No hardware trim in use or mapped to the joystrick to my knowledge.

 

Keen on getting a Saitek yoke soon though.

Oh, yeah I believe that pmdg products should not be used with fsuipc.

 

Here's page 27 of the introduction document on the T7

 

The PMDG 777-200LR/F is fully compatible with FSUIPC except that we recommend that you do not calibrate your flight controllers through FSUIPC. We recommend that you use the driver/software that comes with your hardware. (Calibrating through FSUIPC may not cause any problems, but in certain circumstances with certain hardware we found that problems existed that could only be resolved by having the user conduct the calibration via the driver/software.)

Hey David well spotted, I missed that. It doesn't elaborate on what sort of problems might occur, but maybe it had something to do with it.

Something to do with the .ini file, but I would test it by erasing all fsuipc profiles for the T7, and see if that happens again.

Will do, cheers.