Trim issues, AP disconnect

[Enrit]

Recently I have had some problems with the 737. The autopilot disconnects every few minutes during the climb and cruise. There was no obvious reason for this; it did not seem to be linked to sudden changes of wind.

I also notice that the trim during flight is very far forward, right on the front edge of the green zone, although I set it as per the FMC setting (3.4 on the last 2 flights, for a GTOW of 47.5 tonnes. When the AP disconnects, the plane wants always to climb, as if its tail heavy.

I am using an Saitek X52 pro stick/throttle, and wondered if there was some problem with it, so I dis-assigned the 2 trim buttons on the stick (also the a/p disconnect button on the stick) and reassigned nose down/up trim and a/p disconnect to the keyboard, but the problem is still there.

Any help greatly appreciated - I love this plane!

[Morten]

AP disconnect might be your hardware spiking or you accidentally bumping into your controls.  You will enter CWS mode. Try increasing the null-zone.

issue #2 is probably a result of issue #1

M

[Enrit]

Many thanks, will give it a go.

[Litjan]

Also noticed that there can be situations where the plane runs out of trimrange when CG is fairly aft and speed is very high. We have to investigate if this is normal or something we need to fix.

The trim set for takeoff (green range) has nothing to do with the trim during cruise, so that is not a lead, though.

Thanks, Jan

 

[Enrit]

OK, as suggested I extended the x & Y null zones from 4 to 7 %. Problem solved - no AP disconnects.  

This time, though, the autothrottle kept disengaging! about every 3 - 4 minutes.

I've been using the IXEG 737 since April, and its only in the last few weeks these problems have occurred. So I will try a reinstall, and see if that works.

Thanks for your help.

Neil