A32NX - Trim Setings

Hello All,

I may have missed the discussion/update on this topic but can you actually set the trim in the A32NX like in the real plane based on weight etc.

Is it now modeled in the A32NX?

I have watched some tutorials and none seem to set like you can in A320 versions in XPlane/P3

Many thanks for your help.

JD

I guess it depends on what you’re trying to achieve by manually setting the trim. Technically yes, you can manually set the trim in the A32NX, but I can’t think of a reason why you would need to. Since as long as you set the weight, and center of gravity, it will auto-trim the aircraft accordingly.

Thank you.

Shouldn’t one be setting and crosschecking the CG pitch trim on the pitch trim wheel for takeoff?

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I always leave them at 0 neutral for takeoff.

That’s interesting. On the real one setting the correct stab trim is essential.
It varies between -2.5 and +2.5 units depending on CG.

Well, I made sure my CG is exactly in the middle everytime. Hahaha.

In that case 0 is correct of course.
Since you are doing pretty long flights you should be able to save fuel by flying with an aft CG :wink:

Yes, you can and must set the trim in the A320 on the ground for the takeoff as you would in any other aircraft. Based on your TOCG (Takeoff CG) value in the MCDU, you would look at that scale right next to the thrust levers and find what the corresponding trim setting would be. For example if your CG is around 30 you would have about 0.3 nose down trim.

You physically set that with the actual trim wheel which is the wheel right next to that with the white and black banding. Where do you see the set trim value? You can bring it up using the ECAM FCTL page or, as you are doing your after start flight control check, the FCTL page is automatically brought up and you will be able to set and see your value there.

You can also enter this value on the PERF page of the MCDU where it asks for “THS” which is AirbusSpeak for Trimmable Horizontal Stabilizer. It is a reference for the pilot only and the MCDU doesn’t actually use it.

There is a chart for this. as shown below. So, yes the A320 has “auto trim” but that has nothing to do with setting the takeoff trim which must be manually set.

Learn more here:

Thanks this is a good scale to have. I’ll keep this in mind on my next flight if I shift my CG.
I’m thinking of taking the median CG of 28 based on the halfway fuel mark.

So if I’m starting my flight with 100% fuel. Then I set my CG as such that I can have 28 CG at the 50% fuel mark. Then I refill the fuel back to 100% and see how the CG shifts. That way the CG shifts into the middle about halfway through the flight and continues on as the fuel decreases.

Having this scale would help with setting my takeoff trim accordingly.

So this is why economy class is positioned at the back…

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Again, if you can choose, you usually aim to have the CG as far aft as possible.

I tried this out, and it seems to be performing better.

So before I start the flight, I made sure to reset my payload, but with an empty fuel. Then I use the CG slider, to get as close to the aft limit as possible. About 39.98 CG. Then once I got that CG on an empty tank, I reset the fuel to whichever fuel I want which will bring the CG slightly forward. That way, I’m still on the most aft CG as possible, while preventing it to go over as the fuel decreases.

And before takeoff I set the stab trim according to the scale, and it does perform better. Thanks for the tips.

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Below is the CG envelop for the A320 you can use for your W/B calculations. The A320 does have a rather large CG envelope. In the PDF I shared, it shows the optimum t/o and landing CG for an A320 to be a FORWARD CG of 25. You can see this in the W/B Chart below.

Not to over complicate it but the document states, as is true in most aircraft, any CG inside the envelop is ok. If you look at the A320 trim wheel scale, notice the wide “green band” for trim values. Same concept here. Anything in the green is ok. The document however talks about OPTIMUM CG range.


To me this table looks more like 25% is the forward limit for better TO/Lnd performance, not the optimum.

Yes. For takeoff which is where this conversation started. For flight, there is a more beneficial “CG Range” vs position which PDF doc explains.

Is this A320 still valid for the A320neo? I find that most resources that says A320 tends to refer to the older A320-200 or the CEO model. From my limited understanding the neo performs differently than the older models, so most calculations that tends to be geared towards the A320-200 or the CEO is practically useless for the NEO.

That being said… which one should we be going for here? And is that 25% MAC is the CG for empty aircraft, yes? without passengers, baggage, and fuel?

I skimmed through the PDF I provided in about 5 minutes which will really explain what’s going on. In summary, there are performance differences but that will not generally impact the general loading. Whatever the differences, the guide explains for the single-aisle Airbus family aircraft, “the optimum ZFCG or TOCG is any CG inside the operational CG limits” which you can see in the chart provided.

In other words don’t sweat it if it’s in the limits. All this to circle back to the original posters question. Now you can see why trim is crucial and necessary to set before takeoff because of the flexibility in range of possible CGs.

@Neo4316 , I usually end up with TOCGs in the range of 25-30. You’ll end up with trim values less than +/- 1. You see 28 is around 0 on trim setting.

According to this slide. It seems to be saying that the most optimum CG for both fuel consumption, takeoff and landing performance seems to be the most aft CG:

So I guess I should be aiming for between 33.64 %MAC and 39.96 %MAC. As that would make it completely aft CG from take off, cruising, and landing which takes into account the CG shifts due to fuel consumption. While all within the CG range during all phases of the flight.

Which should make my take take-off THS and manual trim to be Nose down by between 1.4 to 2.5 respectively. (I’m not using the trim scale that you provided, because this scale seems different from the scale being shown in the A320neo cockpit trim wheel. Which I assumed is due to your scale is only applicable to A320-200 or CEO, while the one we have in the sim is already set for the A320neo.)

I’d recommend you spend 5 minutes to read the PDF I provided which should make all this clear.

Scale is different, but you can take your TOCG value, look at the scale next to the thrust levers like you said and read your corresponding THS value and set your trim to that value.