[SOLVED] 777 trim broken

[jwocky]

Vincent ... you realized, that the line you quoted out of context was while it was still in context, referred to planes in FG? Not in RL? And yes, obviously many FG pilots fly around in FG without using manual trim. Again ... in FG! And thus, my question aimed at what we could/should do in FG.

[KL-666]

Hello Jwocky,

No, i did not realize you were talking about fg. Sorry about my misunderstanding.

What should be done in fg? Simulate rl i guess. In my previous post i quoted what i have sent pm to Hyde about auto trim and manual trim. Something along that line should be done.

In order of importance, there should be:
1) manual trim. Always!
2) autopilot working the trim (not elevator)
3) auto trim, following pilot's inputs on the yoke (in this case autopilot may work the elevators too, because auto trim will get the stabilizer trimmed anyway)

Btw, I saw Hyde here, so i assume posting about 777 here is enough, and i do not need to pm on that other forum?

Kind regards, Vincent

[Octal450]

@Hyde
First off, welcome to the FreeFlight Forum.

Perhaps the use of more nasal timers, for the amount of time the yoke is push or pulled?

Regards,

[Octal450]

2) autopilot working the trim (not elevator)
Btw, I saw Hyde here, so i assume posting about 777 here is enough, and i do not need to pm on that other forum?

This is wrong. The autopilot uses the elevator, then uses the trim to maintain the pitch it has achieved. I am going to attempt to make this in the MD-11.

Hyde just posted about it here, I also left a note on the FG forum earlier today.

Regards,

[KL-666]

That is exactly stated in point 3). All i said in point 2) was, that without auto trim, the autopilot should work the trim, because it is more realistic to have the plane in trim.

Kind regards, Vincent

[Octal450]

@KL-666 It shuld use both. The elevator moves quicker, and has a more immediate effect, then the AP should trim the plane, to keep it in trim.

[Hyde]

I've just pushed the change.
Please try and let me know the results.

Hyde

[KL-666]

Hello Hyde,

Thanks for having the manual trim back. But the auto trim is too much interfering with manual flight. I see auto trim immediately racing after yoke inputs. Maybe 3-5 seconds delay is too short. Try 10 seconds for the start of following, and maybe 20 seconds delay after manual input.

Auto trim is a complex beast. If implemented simple, it causes all sorts of undesired behaviour. Let me give a complex example: Make a turn with good roll angle. Then you have to pull a bit to stay level. Then auto trim kicks in relieving the yoke. But at rolling out of the turn you have an unnatural high up-trim. I am pretty sure Boeing has solved this issue by having the auto trim intelligent enough that it knows there is a turn, so it should not trim.

Kind regards, Vincent

[Hyde]

I've changed the parameter difference autopilot and manual control.
Please check again.
thanks,

[KL-666]

Hello Hyde,

The auto trim is a lot calmer now, and the plane flies a lot better manually.

There are a few cases where auto trim is off in the 777:

1) on the ground
2) in flare
3) in the rotate pull

For all three i would suggest to turn off auto trim below 50 ft agl. This is specifically for flare, but it catches the other instances too.

4) The Boeing logic for auto trim in a turn is complex and unknown. Therefore i suggest to turn auto trim off in a turn too.

This can be achieved by turning off auto trim at a bank of say more than 5 degrees.

Kind regards, Vincent