Trim issue revisited

[bobsk8]

In the last few days, I began flying the 172 and Cherokee after a few months of flying 737's. I noticed on the 172, that I had real issues properly setting the trim. I checked most everything, googled the topic, looked at the forums, and a couple of suggestions I read multiple times, about making sure I had run the A2A update. I had run this update, some months ago, and just ran it again a couple of weeks ago, but the problem persisted. I reported my symptoms of needing a great deal of down trim on takeoff, or the 172 would climb at over a 1500 fpm or more, If I had trim set at the takeoff mark on the trim indicator. I found a setting of about negative 35 on the trim produced a Vy speed of around 80 knots. Others posted that they were not seeing this on their 172''s. Nick on the forum suggested that I run the update again "if I had recently reinstalled the 172, but first to delete the client .wyc that is located in the Prepar3D v3 /A2A/Cessna 172/ Update_p3d folder. I did as he suggested, and again ran the A2A update, and this time it took a much longer time to complete.

After running the update, the first thing that I noticed is that the update had replaced the aircraft.cfg file for the A2A so I lost some entries I had for repaints, and I also lost a modification that I had made for the Camera0 file for Ezdok and the inspection views to both work. I had a backup of the entire aircraft.cfg on a backup drive, but I didn't want to replace the after update brand new cfg with and older version, because I suspected that changes were made of the data in the cfg file that were done by the update and I wanted to keep those. So I just copied an pasted the few repaint entries from my cfg backup to the new one, and I did the same thing with the camera file. Anyway, now I was convinced that running the update before had not worked, because these changes were not made the prior time I ran the update. Then it suddenly dawned on me, that I had in fact reinstalled the C 172, when I went from P3D version 2.5 to version 3, which required an uninstall of version 2,5, and then having to reinstall all my add ons including my 172 and Cherokee. When uninstalling P3D, some add on files are left, and apparently the updater saw this client.wyc file indicating that the update had already been run with my previous version of P3D, so it just skipped it. When I deleted that file client.wyc, now it saw the original install non-updated file of the C 172, and knew it had not been updated, and so it ran the update properly.

Now I flew the 172 after the update, and the trim behavior was totally different, and much more like the real aircraft. I could set the trim prior to take off pretty close to the takeoff mark on the trim indicator, and the climb rate was much more normal. This lack of the update was what had caused all my problems. The point I want to make with all of this is, that there are quite a few people that have P3D, and if they had older versions of P3D like V1 or V2, and update to the next version, they need to reinstall the A2A aircraft, and if they do that they need to make sure the update runs properly after they reinstall it. Deleting this client.wyc will insure that this happens.

One more thing I discovered in this, is the behavior of the trim wheel, whether you are using the joystick assignments in P3D ( FSX is probably the same), or FSUIPC. If you notice the trim wheel moving very slowly with a steady speed, that is not right. It is too slow to properly set the trim in my opinion. This usually happens if you use FSUIPC to program your buttons on your joystick. The other behavior of the trim wheel is to start out very slowly for about 1-2 seconds and then speed up. I call this the non-linear behavior of the trim, which is not realistic either. I have never flown an aircraft where the trim effect when moving the trim wheel is non-linear. The fix for this , which is beyond simple, is to use the built in A2A Input-Configurator which is found in the Windows/All programs /A2A Simulations /Accu-sim C 172 Trainer ( or whatever ever aircraft you are adjusting). Stat the configurator in admin mode and open the configurator and you will see a number of selections for setting controller buttons. Click on the yoke trim up and yoke trim down, and press the joystick buttons that you want to assign to your elevator trim. After you do this, make sure if you have FSUIPC controlling the trim aircraft specific, to turn that off. Now the trim wheel is different in two ways, first the movement is much faster as soon as you press the trim up or down on your joystick, and secondly the non-linear behavior is no more. The speed of the trim wheel is fast and it is steady You want a small trim adjustment, just tap the trim button you have assigned. If you want a larger adjustment just hold it down a bit. With the linear behavior, it is much easier to control the trim adjustment and quickly you will learn how long to press the button to get the trim you want. It is far better using the A2A method, than either FSUIPC or the Flight sim behaviors. By the way, I also opened the same Input configurator for the Cherokee and set that too.

Hope that helps.

[Great Ozzie]

Nick on the forum suggested that...

Should probably promote Nick to admin.

Well if not... maybe a consideration for Warrant Officer - even if the USAF refuses to bring back the rank.

[bobsk8]

Nick on the forum suggested that...

Should probably promote Nick to admin.

Well if not... maybe a consideration for Warrant Officer - even if the USAF refuses to bring back the rank.

I totally agree!!

[Nick - A2A]

Hey Bob,

Couldn't agree more with you on the constant speed trim option offered by the input configurator. I always found that "trim acceleration" behaviour in FSX annoying and, as you say, totally unlike the trim response in a real aircraft (though I haven't flown one!) I found I'd regularly overshoot the desired trim setting back when this was the only option for me in FSX. The "linear" trim response as you term it is much more sensible. Incidentally, I stumbled across some figures for the trim rate of the manual electric trim (MET) system in a real Cessna (a 182S) when reading the accident report I linked in this post. Unsurprisingly, the guys at A2A have done a great job of matching the trim rates described in the report; just a second or two of difference if I recall correctly. (It would still be nice if they could implement the various MET annunciators I mentioned in that post though... )

There's actually another bonus to using the input configurator for pitch trim too. The pitch trim assignment via the default FSX options seem to be a function of frame rate, so the trim rate will actually differ depending on your FPS. However, the input configurator doesn't suffer the same issue as discussed here.

FSUIPC actually has some ways in which we can assign trim inputs to buttons without the "non-linear" response, and with the trim rate being totally customizable. However, it involves using offsets and is certainly a lot fiddlier than the input configurator. For advanced FSUIPC assignment to modify the trim rate, this topic may be helpful, though I think the parameter values of 256 suggested are a bit extreme and will lead to rather a fast trim rate. However, by using this 'offset' method you can set the trim rate exactly as desired. See page 31 of the FSUIPC4 User Guide for more info on this technique.

As regards the client.wyc file, yeah that seems to cause issues from time-to-time, typically when people reinstall as part of trying to troubleshoot an issue. Not sure if there's any way the Accu-Sim updater could be improved to make this less of an issue, but probably one of those things that's easier said than done.

Cheers,
Nick

P.S. Thanks guys.

[bobsk8]

Hey Bob,

Couldn't agree more with you on the constant speed trim option offered by the input configurator. I always found that "trim acceleration" behaviour in FSX annoying and, as you say, totally unlike the trim response in a real aircraft (though I haven't flown one!) I found I'd regularly overshoot the desired trim setting back when this was the only option for me in FSX. The "linear" trim response as you term it is much more sensible. Incidentally, I stumbled across some figures for the trim rate of the manual electric trim (MET) system in a real Cessna (a 182S) when reading the accident report I linked in this post. Unsurprisingly, the guys at A2A have done a great job of matching the trim rates described in the report; just a second or two of difference if I recall correctly. (It would still be nice if they could implement the various MET annunciators I mentioned in that post though... )

There's actually another bonus to using the input configurator for pitch trim too. The pitch trim assignment via the default FSX options seem to be a function of frame rate, so the trim rate will actually differ depending on your FPS. However, the input configurator doesn't suffer the same issue as discussed here.

FSUIPC actually has some ways in which we can assign trim inputs to buttons without the "non-linear" response, and with the trim rate being totally customizable. However, it involves using offsets and is certainly a lot fiddlier than the input configurator. For advanced FSUIPC assignment to modify the trim rate, this topic may be helpful, though I think the parameter values of 256 suggested are a bit extreme and will lead to rather a fast trim rate. However, by using this 'offset' method you can set the trim rate exactly as desired. See page 31 of the FSUIPC4 User Guide for more info on this technique.

As regards the client.wyc file, yeah that seems to cause issues from time-to-time, typically when people reinstall as part of trying to troubleshoot an issue. Not sure if there's any way the Accu-Sim updater could be improved to make this less of an issue, but probably one of those things that's easier said than done.

Cheers,
Nick

P.S. Thanks guys.

The issue with P3D users, is that when you install a new version, which happens about once a year, you have to uninstall the previous version. So possibly a read me note on the update about this reinstalling issue, and possibly having to delete the update folder or that file it contains, would solve the problems that P3D users might run into when updating their P3D version. My quess is that there are more than a few P3D simmers out there flying the C 172 and Cherokee, that have not been updated.