Trim issue with L39

[sjpateys]

I'm having roblems with the trim on the L39 and my experience seems to mirror that of others in that I set the trim and throttle for perfect level flight but 10 sec or so later the aircraft starts to wander (climbing/turning etc) no matter how I try the plane will not maintain level flight for more than 10 seconds or so. I have no trouble trimming my other modules. 

[razo+r]

When you say perfect level, do you also mean you perfectly maintain the speed at which you trimmed the aircraft? 

If yes, have you already tried removing all mods and running a repair? 

Have you also checked that the game/arcade flight mode is off? 

[sjpateys]

The aircraft stays level for about 10 seconds before it starts to climb. I then have to adjust throttle and trim again. I am using the simulation flight model

[razo+r]

Well, any change in speed also results in different forces, and that in turn will require you to constantly trim for the new speed. So unless you maintain perfectly the speed you trimmed for, you will always have to readjust the trim. That is how a non-FBW aircraft handles.

But if you still feel something is wrong, perhaps you should upload a short track.

[sjpateys]

I am fully aware of how aircraft handle. I'm not a newbie. I know some are harder to trim than others. You dont normally have to retrim every 10 seconds or so even in a non FBW aircraft generally. Personally I think that the trim switching is a little too coarse so I guess I will just have to live with it. The trim changes are only minor anyhow now I have have had more practice.  

[sjpateys]

I think you isunderstood my original post tbh, I wasn't expecting the trim to be maintained if I altered the power settings, I was talking about level flight at a aconstants speed. 

[razo+r]

You never replied with this information to my questions of your speeds so I assumed you were not flying at a constant speed. 

Would have been a great detail to know earlier... 

[sjpateys]

I have already answered your question. Yet again you have made assumptions. This is why I  gave up responding in the first place. 

[average_pilot]

On 3/24/2024 at 4:32 PM, sjpateys said:

I then have to adjust throttle and trim again.

Don't touch the trim, only the throttle. Every time you touch the trim you are telling the airplane to fly at a different airspeed and thus at a different power setting. You will never find the sweet spot on the throttle for (almost) hands free level flight if you are constantly re-trimming.

[virgo47]

L-39 module has a coarse trim, the action is quite fast, so even a short tick to the trim hat changes it often more than for the perfect position. In any case, without a track file, we can't say more.

[average_pilot]

How to fly straight and level using physics instead of piLoT sKilz. L-39C edition.

On the attached track you'll see (hopefully) that at some point it's just a question of reeeeally tiny throttle adjustments to float around the intended altitude.

L39SnL.trk

Edited May 21, 2024 by average_pilot

[NineLine]

Is there still an issue here? Looks like its resolved?

[virgo47]

1 hour ago, NineLine said:

Is there still an issue here? Looks like its resolved?

I'm not OP, but I fly Albatros quite often and I don't see it as a bug, it's a natural need of L-39 for regular trimming.

EDIT: Tested it now with the current patch, trimming seems OK.

Edited July 23, 2024 by virgo47