A32NX - Trim Setings

Yeah, I have spent over 30 minutes reading the PDF that you provided… but seeing as these are power point presentation slides, I’m missing a lot of context as I believe these are designed to be a supplemental content from an actual presentation where the presenter is actually the one delivering all the content and knowledge information.

I’m just saying that the trim scale you provided has a different scale than the one next to my thrust levers. So I just assumed that these two are taken from a different type of aircraft. So I’m just going to follow the one in my cockpit.

My question isn’t about how or which trim to set according to the TOCG value. That part is clear to me, what’s unclear is which TOCG should I set to have the optimum CG for my whole flight because I’m missing a lot of context from the power point slides in that PDF. But that’s okay, I think I figured it out now. Thanks.

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The further aft, the better, but you as the pilot have zero control over loading/CG IRL.

That said, if your A320 reverts to direct law a forward CG will make hand flying the A320 a lot easier!

True… I’m just talking about the context in the MSFS, seeing as we have an adjustable CG slider. But yes, I’m moving my CG to be as further aft as possible within the allowed range for the whole flight.

No worries and your right that scale doesn’t match. Basically look at slide 30. Anything inside limits is ok for A320. It’s a range, not a value.

Basically on trimming in general, we don’t worry about cruise CG as this would always be changing while flying due to fuel burn. You need to ensure that at takeoff you are within CG, and, that for landing, which considers fuel burn, you are within CG limits. During cruise it will shift and in the case of the A320, as long as it’s within the operational CG limits as shown on the WB chart, you are good to go.

Don’t forget that the passenger and baggage weights can be way off.

Keeping the CG in the middle is for sure a save solution.

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Very true.

Yeah, I’ve been taking this into account when I was trying out different CG, I move the Fuel slider from full, to 50% to empty and somewhere in between, and monitor how much the CG shifts during the entire flight. And judging form how it shifts, I managed to determine the best TOCG which takes into account making sure that when the CG shifts due to fuel burn, the CG is still within the operational limit.

Yeah, that could be the case, but it seems the one in the sim is pretty constant, as I always use the default payload which loads the exact same weight for passengers and baggage all the time. Which makes the CG very predictable.

Just for confirmation, I’m talking about RW ops. This luckily doesn’t happen in the sim.

Yep. The default sliders for payload in MSFS is not really ideal for this type of work but it works. I tend to enter in my own weights to better simulate pax and baggage loads.

@Neo4316 , @PZL104, I have one of the other Cenisoft Airbus W/B tools so I just bought the one for the NEO. Below is the envelope information. One thing I see is the trim scale again is off within the sim to the real aircraft so I’m thinking it may be wrong in the sim. I’m going to setup a flight using this tool to see if I can get good values for MSFS

The other challenge with the default “load manager” in MSFS is it has a simple two-zone setup for the NEO. Typically, you would see three W/B zones 0A, 0B, 0C, and/or, 0D. These each have their respective weight limits. it has nothing to do with seat layout, it’s just how the aircraft cabin is sub-divided. Having only two as in MSFS creates huge weight zones. Baggage compartments are also split with 4 available.

I think I’ve done this before but I think the NEO in MSFS is a 180 pax version. I consider a passenger as 200 lbs and 30 lbs of baggage per passenger for WB calculations. Given this, I took

180 pax x 200 pax = 36,000 lbs / 2 pax zones = 18,000 lbs business & economy class
180 bags x 30 lbs = 5400 all loaded in the rear baggage compartment in MSFS. This produces this setup:

To hopefully help out and not add more confusion:
The Fly-By-Wire A320neo is based on model A320-251N, which is the neo with CFM Leap1A-26 engines. It is specifically weight variant 055. The CG envelope/trim chart differs from that provided above for the A320-271N model. Within that weight variant, there are several different CG envelopes that customers can buy and use. For example, here is the basic CG envelope:

And here is an extended forward CG envelope:

Why the different envelopes, and what is the effect of using a different envelope?
Basically loading flexibility vs takeoff and landing performance. The more forward the CG limit, the higher the stall speeds, which leads to higher takeoff and landing speeds. Takeoff and landing performance must be based on the forward limit CG position, so the regulatory takeoff and landing performance is better for more aft forward limits. A more forward limit provides more loading flexibility, but penalizes takeoff and landing performance. The performance data are tied to the CG envelopes (when there are multiple envelopes available). Since the performance is based on the forward envelope, operating aft of the forward limit does not provide any increase in the regulatory performance although it will provide more of a safety margin.

The CG envelopes in MSFS contain limits that do not vary with weight as the real envelopes do. As a result, the MSFS forward and aft limits don’t correspond exactly to any real CG envelope. What is in there now (16% and 40% for the forward and aft limits is close to the extended forward CG envelope.

We are in the process of implementing a 4-hold/4-section 1-class cabin with 174 economy class seats. This has been in work for quite some time, so no idea when it will be finished. Loading will be accomplished via the EFB.

We are aware that the takeoff trim scale in the current flight deck is not correct for our airplane. We are waiting on access to the model to be able to fix it.

As far as setting the takeoff trim, the airplane will be able to safely take off with the trim anywhere in the green range, but you should be setting it according to the takeoff CG position. Using the “incorrect” trim scale in the current flight deck is okay.

For cruise, an aft cg should generally result in less drag and lower fuel burn. The MSFS flight model does not correctly account for aerodynamic center vs CG for swept wing airplanes at this time, but for differences in CG position, the effects should generally be representative.

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@Neo4316 Then you’re doing it wrong. And your advice to the OP about auto trim doing it for you is wrong, too, at least for the start of the flight, as you, the PIC, must manually set the trim manually. You may not have to touch it again until after you turn the AP off before landing, depending on when you do that (for example, if you use the autoland capability of the aircraft, setting it before TO will literally be the only time you have to touch it. OTOH, if you like to hand-fly the last 10,000’, you may be touching it a lot.

It all depends on circumstances.

EDIT: Now I see that you are manually manipulating the CG to the point that 0 is correct. That’s one way to go, I expect, but it’s not at all realistic. The highly variable weight of your cabin will make such a thing impossible. From one extreme, a post Covid cabin with only a small handful of passengers, if any (I heard tales of flights leaving the gate with only company employees on board), to the other, which would be say a Christmas rush, where every seat is not just filled, but overbooked (not that those overbookings have anything to do with CG), and everybody is wearing and carrying heavy winter gear with them in their baggage. There’s no way to force both of those scenarios into a 0 trim setting, no matter how hard you as a RL Captain, might try.

EDIT 2: I see others have already told you much (if not all) of what I just did.

My CG tends to be around 30 (I think it’s because of how the sim auto distributes the weight I get from Simbrief), but that corresponds to more like +0.9ish on the trim. I wonder if the table you shared does not match what the A32NX actually does, like some kind of bug or error.

BTW, if this has already been discussed (I’m responding as I read through rather than reading the whole thread first), I’m not going to bother editing my post as I did above. I’ll just chalk it up to “I should have read the whole thread first”. Which is possible with a 30-something post thread, but I’m not even going to try if I’m late to the party and it’s already at 700 posts or so.

@Fmgc320 0 weight pilot and co-pilot? Are you assuming that you’ll have ghosts flying the b1rd?

No ghosts. The crew is already included in the DOW (+catering etc.)
Crew is (obviously IRL) not part of the payload.

@PZL104 Dry operating weight?

Yes, sorry.

Yeah, I learned a lot more now. Before reading this topic, I always aim for my TOCG to always be 28, right in the middle between the two CG limits. Because I thought that being the absolute balance is the way to have a stable attitude. But the more I learn the more I need to shift my CG out.

I guess it’s true that it’s not realistic, but I guess for me the benefit of this sim is that I can get it to the way I want it to. I have a little bit of OCD, so I always need to have everything to be symmetrical, perfect, balanced whenever I can even if it’s a little bit unrealistic. And the sim lets me to do it, so that’s why I do it.

Then I learned that the CG shifts as the fuel burn, again, I adjust my CG to have the most centered and balanced throughout the whole flight instead of just the takeoff. But I don’t know if manual trimming is mandatory, because I’ve been keeping my take off trim to be at 0 ever since, and for some reason, my plane doesn’t crash on take off. So I always thought that it’s okay. If it is unrealistic, then perhaps the FBW team needs to be notified so that they can apply the correct attitude behaviour for an incorrect take off trim.

But as I learned more in this topic, the more I understand about the importance of an AFT CG. So now, I’m putting the CG as far back to the aft as possible, also taking into account the CG shifts due to the fuel burn, making sure that once all the fuel is depleted, my CG doesn’t go out of the limit, while still being as far back to the aft as possible.

While it may not be realistic, because the sim lets me to shift the CG around, means that I will be setting them to the CG that I want, and my payload is always the same for all my 800 flights anyway. And I’m not looking for variable passengers/cargo.

We are all different of course, but having variable passengers and cargo and fuel load, and having to need to do different calculations for every single flight that I want to do isn’t really my idea of fun. I don’t want an arcade feel flight simulator of course, I want a detailed and realistic sim. But I don’t want it to be too realistic that it takes the fun away for me. So I like to be somewhere in the middle. Balanced. A lot of detail, but take away the variability to keep it constant.

Now after learning everything I need to know, I’m just going to do it properly this time.

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The most important part is you’ve learned something new and applying it to how YOU want to simulate flight in MSFS.

It’s also a valid point you bring up where with that knowledge, you now would appreciate more “realism” dialed into MSFS/A32NX in that aspect, even if you choose not to leverage it. It reminds me of the deep functional capabilities of another platform’s A320. While I can get super immersed in simulating a line pilot with complex loading scenarios, I may not do it every time. But knowing I can is the point. And that would only matter if you knew the “why” and “How” about how it’s supposed to function in the first place.

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The video is private… Can you at least change it to unlisted, if you don’t want it to get picked up by the search engine?