If my memory doesn't fail me, the FS family of sims simulates the trim by moving the CG of the aircraft which is a little weird if I remember correctly my classes in physics of long ago.

FS20 using 1000 application points to apply positive and negative lift all over the wings and tail should allow a more orthodox simulation. I took a quick refresher course  here https://www.grc.nasa.gov/www/k-12/VirtualAero/BottleRocket/airplane/trim.html but I would appreciate if real life pilots and FDE developers would comment this point to enlighten us all ?

 

Trim in FSX/P3D is simply really bad. It's even worse for aircraft with non-adjustable horizontal stabilizers. Inertia is another big problem and since Asobo already mentioned in episode 3 that this item has been improved, I have no doubt that we will finally see correct trim behavior for trimmable elevators/stabilizers 🙂  

Edited November 25, 20196 yr by FDEdev

To do it properly, MFS should depart from the present model, which actually looks more like the airliner stabilator approach when it comes to the elevator trim, and model at least as many different forms of trim as there are:

- ground adjustable trim tabs on some of the control surfaces ( ailerons, rudders, elevators );

- cockpit adjustable trim tabs ( for either of the above, sometimes some are adjustable by the pilot from the cockpit while others are ground adjustable );

- stabilators - like in most airliners and many modern "plastic" gliders where the whole horizontal stabilizer changes incidence;

- force trims like still used on some older models ( many gliders I've flown ) where a spring is directly attachged to the stick and compensates for the forces;

There aren't yet rotary wings - those will require yet different approaches...

Just out of curiosity: In War Thunder they restrict the use of trim controls depending on if the real aircraft did have them installed and controallable from the cockpit, but they have a rather interesting method to set the ground adjustable ones for default flight conditions by taking an aircraft to a "test flight", but still only allowing for those control surfaces that had trim tabs for the real thing to be adjustable an then their default settings saved.

Yet, applying trim immediately results in the corresponding control surface to move, even if there is still not enough airflow.

In IL-2 the ground adjustable settings are definded by default in the various game modules.

In DCS World some ww2 aircraft modules allow for what corresponds to ground adjustable trim tabs.

On both IL-2 Great Battles and DCS the control surfaces only move when there is enough airflow affecting their trim tabs.

In X-Plane 11 Austin did also change the way control surfaces react to trim. Previously they acted pretty much like in War Thunder, while now they also rely on the "airflow" to do the job...

Edited November 25, 20196 yr by jcomm

Just for clarification, a stabilator or all-flying-tail is a horizontal stabilizer which has the full range of motion like an elevator. Hence the word mix stabilizer and elevator, like on the DR400.

Most airliners (and e.g. the Piper Cub) have a moveable/adjustable stabilizer with a very limited movement range which is only used for trimming.

The L-1011 had a very special horizontal tail design where the stabilizer did move together with the elevator when moving the yoke, a combination which provided very good pitch control. 

 

Edited November 25, 20196 yr by FDEdev

Another interesting control system is in the DC9/MD8x family (and as I read, also DC8 and Convair 880), where IIRC the elevators are not powered, but basically free floating. They are operated through the means of trailing edge trim tabs, cable actuated. In other words, the elevator position is controlled by the pilot not directly, but as if they were continually trimmed to the desired position.

With regard to MFS, more than trimming per se (which shouldn't be hard to implement correctly), I wonder how it will deal with flight control sensitivities. Will the max control excursion decrease with increasing dynamic pressure? Or will it use some other method (increasing non-linearity etc.) to account for airspeed-related control loading? And how will max control excursion change with changing trim position? All PC flight controls are very different from non-fly-by-wire flight controls, so there are multiple ways to model them...

 

Aside from the simulation aspects of trim, I'd like to see some sort of user interface to substitute for the lack of force feedback. For example, if you hold the yoke/stick for the desired attitude, then start adjusting trim, an on-screen gauge could appear to represent the force you need to apply, and as you trim out the required force you can let the control return back towards the neutral position. When you stop trimming then after a few seconds the visual gauge disappears. That would be a lot nicer than trimming blind as we do today.

30 minutes ago, fs4fun said:

Aside from the simulation aspects of trim, I'd like to see some sort of user interface to substitute for the lack of force feedback. For example, if you hold the yoke/stick for the desired attitude, then start adjusting trim, an on-screen gauge could appear to represent the force you need to apply, and as you trim out the required force you can let the control return back towards the neutral position. When you stop trimming then after a few seconds the visual gauge disappears. That would be a lot nicer than trimming blind as we do today.

That's a good idea 👍

2 hours ago, fs4fun said:

Aside from the simulation aspects of trim, I'd like to see some sort of user interface to substitute for the lack of force feedback. For example, if you hold the yoke/stick for the desired attitude, then start adjusting trim, an on-screen gauge could appear to represent the force you need to apply, and as you trim out the required force you can let the control return back towards the neutral position.

Don't understand that one. That's what I'm doing with my non-force feedback joystick and without any gauge. If I have to apply constant forward/aft stick pressure, I start trimmung and I'm reducing stick pressure until it reaches the neutral/center position.

19 minutes ago, FDEdev said:

Don't understand that one. That's what I'm doing with my non-force feedback joystick and without any gauge. If I have to apply constant forward/aft stick pressure, I start trimmung and I'm reducing stick pressure until it reaches the neutral/center position.

I've never found that worked particularly well. I try my best but absent feedback it's just guesswork and trying to use visual cues but yes eventually the trimming gets done. It is a long-standing complaint that it's easier to trim a real airplane than it is to trim in the sim.

Strange. Never had this problem. Trimming happens basically automatically for me, IRL and in the sim. Guess that this depends a lot on the quality of the joystick/yoke being used.

Trimming is automatic for me too, but at release of the joystick, most the times I see a tiny over- or undershoot and a small second trimming is necessary. So having a gauge which would simulate the force is an interesting idea, worth trying.

It's indeed an interesting idea/feature, especially for beginners...if you can disable it!

The alternative would be a feedback trimwheel but I don’t hold my breath waiting for one.

 

7 hours ago, fs4fun said:

I'd like to see some sort of user interface to substitute for the lack of force feedback. For example, if you hold the yoke/stick for the desired attitude, then start adjusting trim, an on-screen gauge could appear to represent the force you need to apply, and as you trim out the required force you can let the control return back towards the neutral position.

I have to say I'm with @FDEdev here... I'm not really sure what such a gauge would add beyond the visual and physical cues that are already there.

I mean, you can already feel the force required to hold the stick out of centre... because you're already holding the stick out of centre. If you can't feel the difference between the stick being centred or not, or see the nose attitude move up or down, then I'm not really sure a gauge is going to make a lot of difference.

Hold the attitude, trim, and gradually release the pressure on the stick so that the attitude doesn't change when you are trimming. Obviously if you just let go and start trimming and hoping for the best (I'm not saying this is what you are doing, but it's what I see a lot of simmers doing) then you won't feel anything, and if you hold the stick in a constant position whilst you trim that isn't going to work either; the actions have to be coordinated. Just focus on holding the attitude steady...

There's a simple solution! A new Microsoft FFB joystick. All we need is Asobo to hit up the hardware department at MS.