Aircraft Trim

Hey. So during my flights - my biggest struggle always seems to be that I can’t get the trim just right most of the time. It’s usually too high, but doesn’t fix itself when I try and correct it. Any suggestions on appropriate trim levels for climbing, cruising and approach stages? Thanks in advance.

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Just trim the aircraft until the pink/magenta line disappears. The trim value will change with the weight of the aircraft. 🙂

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I’ve tried that, but it doesn’t like to stay.

What do you mean it doesn’t stay? Works just fine for me on everything from the TBM to the 787

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I think if it cannot stay well trimmed (the magenta mark comes back whatever correction one adds), it means the aircraft somehow struggles (too heavy/high/fast/slow) to fly.

Well sometimes I have to use full fuel (for example - I’m currently doing a 20HR flight from Singaopre to Cancun, Mexico.

I guess I need to use less fuel sometimes - but on certain occasions, I have no other option.

Well then, fly lower to start with (FL280) and see if you manage to trim the thing, say at 0.79.

Good strategy. Thank you mate.

Hi DeerCrusher, thanks for your tips! Unfortunately the same problem also relates with me, it doesn’t stay. Does setting that trim require very small increments/decrements and waiting for it to take effect? i.e. once we set it, the magenta line will sometimes come up again but if we just don’t panic and leave it be it’ll stabilise again? Or should we gradually adjust them as fuel consumption goes over time? Up to now I still don’t know how to get that “sweet spot”, its just so hard to do. Am I missing something else? Like a “trim checklist procedure” kind of thing? (Just like principles in setting which flaps at such and such speed?).

Trimming will have to take small adjustments initially but once you find the right setting it should hold for awhile. As you burn fuel, the aircraft load become lighter and therefore you’ll need less trim. So yes, you’ve got the right idea. Again it takes a few moments to get the aircraft trimmed out. Its not as simple as setting the trim to a specific number unless you know for certainty the trim setting for the speed, weight and altitude you’ll be cruising at.

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It would be nice with autotrim

Indeed! Yet I fear we would probably gain a bit less knowledge about how to fly an aircraft.

I also noticed that airliners need more positive trim at FL370 or more than they do at about FL280. Probably yo compensate the relatively thinner air.

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