elevator trim offsets, OBCO VS 3338 QUESTION and how to turn it off

[Ron Buchwald]

Hi Pete

Hope this finds you well, Now I have just finished up-dating to NEW release FSUIPC 3.999, wide sever 6.94, wide client 6.94 on all 5 of networked PCs. I have a question on what offset to use for ELEVATOR TRIM. Ok your docs say to use offset 3338 IF you want to disconnect them if auto pilot is running. YES or NO, via offset 310A, bit 0 or bit 5. YES or NO. now when I send to offset 3338, I get nothing, Well cause that is the post value after cal, I guess, SO, if I send to offset, 0BC0 the value, I do see the trim respond. So I am confused. The problem is " auto pilot is over-written by my sending the elev..trim value via oBCo" so I want to then turn that off, but I can not. I am unclear as how to use 310A and 3338 to do this. Funny, the throttles work ok when in auto pilot, but not the trim, I am using PM MCP.

[Pete Dowson]

I have a question on what offset to use for ELEVATOR TRIM. Ok your docs say to use offset 3338 IF you want to disconnect them if auto pilot is running. YES or NO, via offset 310A, bit 0 or bit 5. YES or NO.

It doesn't say that. I think you are misreading it. It says it is the axis value which is applied to the trim if allowed. It is not writeable, it is a read-out in case an autopilot program wants to disconnect the trim input and modify it to control pitch whilst still monitoring the axis input values in case it should disconnect. This is particularly useful when the trim is a motorised trim wheel also being moved accorfing to the actual applied trim (0BC0).

SO, if I send to offset, 0BC0 the value, I do see the trim respond. So I am confused. The problem is " auto pilot is over-written by my sending the elev..trim value via oBCo" so I want to then turn that off, but I can not.

The facilities to disconnect axis inputs works on axis inputs, not on offsets being written to. There are some exceptions though, that have arisen historically through assorted developments.

Why are you writing to an offset to control the trim? If you want to do that and have it treated like an axis you'd either need to send it as an FS axis control via offset 3110, or, perhaps easier, send it to the free axis offsets at 3BA8, which are now scalable to suit input types other than the PFC ones they were originally intended for. If you use the latter method you'd need to assign the resulting axis input in FSUIPC -- it'll be on one of Joysticks 16-18.

Regards

Pete