As referenced earlier in this thread.. what you see in a model, and what's actually happening, are not aerodynamically related. The idea of course, is for the modeler to make it look as realistic as possible. If the modeler chose.. he could model a beach ball where yoke movement caused inflation/deflation...The problem with MSFS trim, is that it's not trim. It's more like a range adjustment for the upper and lower extremes of elevator deflection (effective, not seen).In the attached image, the trim range is represented by the light red area.-Figure 'A' shows the elevator and trim range at neutral. A properly animated elevator would show the expected deflections, and the model would respond accordingly.-Figure 'B' shows the neutral trim arrangent in full up elevator deflection.-Figure 'C' shows a trim range set to full down; with the elevator deflected full up (yoke all the way back).For explanatory purpose.. a model in flight trimmed per figure 'C' would require the yoke to be pulled all the way back, just to maintain level flight.The MSFS modeling does allow for trim-tab modeling. If you fly my Bonanza, you'll see that the trim-tab animation is counter to elevator animation, but there is no trim-caused elevator deflection. You could custom animate this effect visually, but since MSFS trim isn't really trim, it would be immensely complicated animation to have an accurate "show". You'd have to write a hidden XML gauge that kinda over-rides MSFS, and not only inter-relates trim/rudder animation, but constantly over-rides how the MSFS calculates effective elevator deflection..

For an aircraft to be trimmed lift must be equal to weight and pitching moment to zero. Zero stick force doesn't mean an aircraft is trimmed. Stick force would be zero if the stick is reased in a spin.There's a fallacy is in your statement:"Cl= TBL404 value, (elevator deflection value returns to zero when Yoke is released and trim is achieved or AP engaged).This is of course wrong because there must be a trimming lift from the elevator !"It isn't wrong. If the aircraft was trimmed with a given elevator_deflection then it's no longer trimmed if the yoke is released and the elevator_deflection changes. There's no "trimming lift " simply because the aircraft isn't trimmed.The lift and pitching moment equations together must be considered together, not separately. With no flaps or spoilers and assuming Cm_dT (thust) is zero for simplicity your equations are:Cl = Cl_alpha * alpha + Cl_de * elevator_deflectionCm = Cm0 + Cm_alpha * alpha + Cm_de * elevator_deflectionFor an aircraft to be trimmed:Cl - (Cl_alpha * alpha + Cl_de * elevator_deflection) = 0Cm0 - (Cm_alpha * alpha + Cm_de * elevator_deflection) = 0Both of these two equations have to be solved simultaneously to obtain unique values for alpha and elevator_defection for a given aircraft and Cl - any other values and the aircraft isn't trimmed. Remember that for a trimmed aircraft Cl = Weight / (0.5 *rho * Wing_Area * V^2) so is constant for a trimmed aircraft at a given weight and speed..There is an assumption that Cm_dt repesents the trim tab hinge moment.That may be the case in conventional aerodynamics, but it doesn't necesarily mean that is how Microsoft uses it. In conventional aerodynamics, Cm_de is the elevator hinge moment, not the pitching moment on the complete aircraft. The aircraft pitching moment arises from lift from the tailplane/elevator combination multiplied by its distance from the CG. Hinge moments effectively cancel each other.As others have pointed out, FS is a sub-$50 game that makes reasonable assumptions. It doesn't go into all the fine details of modelling the control system - stick/linkages/elevator/trim tabs. Also there are more ways of trimming an aircraft than by trim tabs.

For an aircraft to be trimmed lift must be equal to weight and pitching moment to zero. Zero stick force doesn't mean an aircraft is trimmed. Stick force would be zero if the stick is reased in a spin.There's a fallacy is in your statement:"Cl= TBL404 value, (elevator deflection value returns to zero when Yoke is released and trim is achieved or AP engaged).This is of course wrong because there must be a trimming lift from the elevator !"It isn't wrong. If the aircraft was trimmed with a given elevator_deflection then it's no longer trimmed if the yoke is released and the elevator_deflection changes. There's no "trimming lift " simply because the aircraft isn't trimmed.The lift and pitching moment equations together must be considered together, not separately. With no flaps or spoilers and assuming Cm_dT (thust) is zero for simplicity your equations are:Cl = Cl_alpha * alpha + Cl_de * elevator_deflectionCm = Cm0 + Cm_alpha * alpha + Cm_de * elevator_deflectionFor an aircraft to be trimmed:Cl - (Cl_alpha * alpha + Cl_de * elevator_deflection) = 0Cm0 - (Cm_alpha * alpha + Cm_de * elevator_deflection) = 0Both of these two equations have to be solved simultaneously to obtain unique values for alpha and elevator_defection for a given aircraft and Cl - any other values and the aircraft isn't trimmed. Remember that for a trimmed aircraft Cl = Weight / (0.5 *rho * Wing_Area * V^2) so is constant for a trimmed aircraft at a given weight and speed..There is an assumption that Cm_dt repesents the trim tab hinge moment.That may be the case in conventional aerodynamics, but it doesn't necesarily mean that is how Microsoft uses it. In conventional aerodynamics, Cm_de is the elevator hinge moment, not the pitching moment on the complete aircraft. The aircraft pitching moment arises from lift from the tailplane/elevator combination multiplied by its distance from the CG. Hinge moments effectively cancel each other.As others have pointed out, FS is a sub-$50 game that makes reasonable assumptions. It doesn't go into all the fine details of modelling the control system - stick/linkages/elevator/trim tabs. Also there are more ways of trimming an aircraft than by trim tabs.

As referenced earlier in this thread.. what you see in a model, and what's actually happening, are not aerodynamically related. The idea of course, is for the modeler to make it look as realistic as possible. If the modeler chose.. he could model a beach ball where yoke movement caused inflation/deflation...The problem with MSFS trim, is that it's not trim. It's more like a range adjustment for the upper and lower extremes of elevator deflection (effective, not seen).In the attached image, the trim range is represented by the light red area.-Figure 'A' shows the elevator and trim range at neutral. A properly animated elevator would show the expected deflections, and the model would respond accordingly.-Figure 'B' shows the neutral trim arrangent in full up elevator deflection.-Figure 'C' shows a trim range set to full down; with the elevator deflected full up (yoke all the way back).For explanatory purpose.. a model in flight trimmed per figure 'C' would require the yoke to be pulled all the way back, just to maintain level flight.The MSFS modeling does allow for trim-tab modeling. If you fly my Bonanza, you'll see that the trim-tab animation is counter to elevator animation, but there is no trim-caused elevator deflection. You could custom animate this effect visually, but since MSFS trim isn't really trim, it would be immensely complicated animation to have an accurate "show". You'd have to write a hidden XML gauge that kinda over-rides MSFS, and not only inter-relates trim/rudder animation, but constantly over-rides how the MSFS calculates effective elevator deflection..

The picture shows how trim tab works. Notice that trim tab and elevator move in opposite direction.During flight, the aerodynamic forces tend to maintain the elevator in the air stream and therefore there must be a sufficient force exerted either by the pilot's wrist or by the trim tab to counter these forces (hinge moment) and assure a given deflection of elevator( when this effort is supplied by trim tab, the pilot can fly hands off).

The picture shows how trim tab works. Notice that trim tab and elevator move in opposite direction.During flight, the aerodynamic forces tend to maintain the elevator in the air stream and therefore there must be a sufficient force exerted either by the pilot's wrist or by the trim tab to counter these forces (hinge moment) and assure a given deflection of elevator( when this effort is supplied by trim tab, the pilot can fly hands off).

The pics are of course, exaggerated for the purpose of showing what's going on. For instance, in my (real life) RV6A airplane, I can look back & see the leading edge of the elevator counter balance ........up about 3/8" (at the most)in flight with normal loadings. If it was any more than that, I'd be shimming the horizontal stab to eliminate some drag. MSFS just isn't animating that 3/8", while correctly showing the tab moving opposite of the elevator.L.Adamson

The picture shows how trim tab works. Notice that trim tab and elevator move in opposite direction.During flight, the aerodynamic forces tend to maintain the elevator in the air stream and therefore there must be a sufficient force exerted either by the pilot's wrist or by the trim tab to counter these forces (hinge moment) and assure a given deflection of elevator( when this effort is supplied by trim tab, the pilot can fly hands off).

Yes.. I know how trim works.. My post and image explained how MSFS trim works.

There is a further misconception. The purpose of a trim tab an a real aircraft is to reduce the elevator hinge moment to zero in order the reduce the stick force to zero while having a minimal other effects. The purpose of trim in Flight Simulator is different. Many, if not most, users have a self-centering stick. With such a stick in FS the only way to zero the force is to centralise the stick and thus centralise the elevator. The purpose of trim in FS is therefore, in effect, to provide the same aerodynamic effect as elevator deflection. If +5^o of elevator is needed to trim the aircraft (ie forces and moments in balance) then the trim has to provide the effect of +5⁰ elevator when the stick and elevator are centralised awith zero stick force.

There is a further misconception. The purpose of a trim tab an a real aircraft is to reduce the elevator hinge moment to zero in order the reduce the stick force to zero while having a minimal other effects. The purpose of trim in Flight Simulator is different. Many, if not most, users have a self-centering stick. With such a stick in FS the only way to zero the force is to centralise the stick and thus centralise the elevator. The purpose of trim in FS is therefore, in effect, to provide the same aerodynamic effect as elevator deflection. If +5^o of elevator is needed to trim the aircraft (ie forces and moments in balance) then the trim has to provide the effect of +5⁰ elevator when the stick and elevator are centralised awith zero stick force.

Exactly.. (per my image).. MSFS trim moves the effective elevator range up or down (even to the point where full deflection is needed for neutral effect (figure C)) .. so that a hands-off situation, is actually some degree of deflection.It works well enough (to me).. so long as you don't push the limits. For example.. In a real airplane, if the last pilot left the trim all the way down, you'd still have full use of the elevator. In MSFS however, there would be no up- deflection available. The full motion of your yoke would have been set so that it would be from neutral-elevator, to a ridiculuous amount of down-elevator (even though the visual model shows normal up/down deflection). You could go rolling down the runway, with the yoke on your chest, and not be able to rotate.

There is a further misconception. The purpose of a trim tab an a real aircraft is to reduce the elevator hinge moment to zero in order the reduce the stick force to zero while having a minimal other effects. The purpose of trim in Flight Simulator is different. Many, if not most, users have a self-centering stick. With such a stick in FS the only way to zero the force is to centralise the stick and thus centralise the elevator. The purpose of trim in FS is therefore, in effect, to provide the same aerodynamic effect as elevator deflection. If +5^o of elevator is needed to trim the aircraft (ie forces and moments in balance) then the trim has to provide the effect of +5⁰ elevator when the stick and elevator are centralised awith zero stick force.

Perfectly right mgh ! But what bothers me exactly is that the trim process (Cm_dt*tab deflection) in MSFS supplies the pitching moment like the elevator deflection does (Cm_de*elevator deflection) but not the elevator lift component (Cl_de*elevator deflection) which is completely ignored.In other words, once the trim process enters in action to replace the elevator effect, the pitching moment component (Cm_dt*trim tab deflection) is there, but there is no more the lift component that makes this moment possible(moment=lift *arm) like in the case of elevator deflected.I think that Microsoft could add a Cl_dt coefficient to the trim tab so that at trim condition, both the lift and moment components are there to provide the same effect as elevator deflection.It appears that FSFORCE (www.fs-force.com) has some kind of solution to this issue. Have a look at the picture below.

Perfectly right mgh ! But what bothers me exactly is that the trim process (Cm_dt*tab deflection) in MSFS supplies the pitching moment like the elevator deflection does (Cm_de*elevator deflection) but not the elevator lift component (Cl_de*elevator deflection) which is completely ignored.In other words, once the trim process enters in action to replace the elevator effect, the pitching moment component (Cm_dt*trim tab deflection) is there, but there is no more the lift component that makes this moment possible(moment=lift *arm) like in the case of elevator deflected.I think that Microsoft could add a Cl_dt coefficient to the trim tab so that at trim condition, both the lift and moment components are there to provide the same effect as elevator deflection.It appears that FSFORCE (www.fs-force.com) has some kind of solution to this issue. Have a look at the picture below.

I'll assume that MSFS is more like a radio controlled airplane, in which trim effects the aileron & elevator servos instead of tabs. Like MSFS, the sticks are always centered by the springs. All I care about is the end result. I do get the "feel" for the need of trim...........due to what I see on the screen..........up to a point. A severely out of trim airplane just won't be replicated well on a desktop sim. As to the pic, I'd say the graphics in it, are overly exaggerated too. If an aircraft needs that much trim for level flight, then it's got other problems.L.Adamson

Personally - having waded through everybody's technical version of how trim tabs works (thank God no-one got into how an MD-80's (six tabs) tail feathers are controlled) - I'm now all for that 12 x 2 bit of aluminium and a hammer......Happy New Year!!! :(

I'll assume that MSFS is more like a radio controlled airplane, in which trim effects the aileron & elevator servos instead of tabs. Like MSFS, the sticks are always centered by the springs. All I care about is the end result. I do get the "feel" for the need of trim...........due to what I see on the screen..........up to a point. A severely out of trim airplane just won't be replicated well on a desktop sim. As to the pic, I'd say the graphics in it, are overly exaggerated too. If an aircraft needs that much trim for level flight, then it's got other problems.L.Adamson

But, do you think that it is safe to continue flying aircrafts(even as desktop sim) that do not trim as in real world?

As long as you stay within a normal, operating envelope (and the model has accurate flight dynamics), MSFS trim functions pretty well.As a sim pilot, like a real pilot; part of your checklist is to make sure the trim is set near neutral (or inside of a visual takeoff range).As you roll down the runway and rotate, and then pitch for a target climb-speed; you can then "trim" to maintain that airspeed without exerting any elevator force on the yoke(stick).. Then when leveling out, you can pitch for a cruise airspeed, and again "trim" to maintain that airspeed without any elevator input... and again for a descent, trim for a "hands off" airspeed... It works very well.But, because of what MSFS is really doing, any trim setting outside of neutral, has actually taken away available elevator on one extreme, and added extra, available elevator to the other extreme... ala, shifting the range.As in my takeoff example.. excess down trim can actually keep you from rotating.. and a certain amount of down trim can actually keep you from initiating a stall.. because the amount of up-elevator deflection available is not enough to reach a stall airspeed.Is simming with that type of trim safe ? dunno.. that's subjective..

It appears that FSFORCE (www.fs-force.com) has some kind of solution to this issue. Have a look at the picture below.

That is accomplished via intercepting and recalculating the FS variables in real time, but also requires a force-feedback joystick or yoke.The same visual effect can be accomplished in the model itself using custom variables driving control nodes. That won't of course affect the flight model itself.

That is accomplished via intercepting and recalculating the FS variables in real time, but also requires a force-feedback joystick or yoke.The same visual effect can be accomplished in the model itself using custom variables driving control nodes. That won't of course affect the flight model itself.

Yeah…I don’t call this a bug at all.The default elevator animation tag doesn’t mix in the trim value…so, as Fr.Bill says, a custom tag is req’d.Likely - all animations should use custom tags B) There are several empennage configurations so the script needs to be designed to suit.I use airspeed and trim plus joystick Y axis to determine the elevator deflection. The effect is subtle…but it’s more accurate.Joysticks being what they are, don’t show the aerodynamic position of the elevator (...a joystick's neutral position is fixed).I think it’s helpful to think of joystick deflection as ‘control pressure’ rather than a cntrl surface position.A neutral joystick is 'zero control pressure' not zero elevator deflection.IMO - consider this before removing your joystick’s null-zone :( :( :(