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MSFS20 Can I correct the pitch attitude of MODEL?

B21-soaring

B21-soaring

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unitedkingdom
Hi the aircraft I'm working on has the model aligned to the GROUND, i.e. the Z-axis is parallel to the ground when the aircraft is parked (the modeller took the side-profile of the plane when parked to bootstrap the model)

The result is after much flight_model.cfg tuning I now have a plane perfectly calibrated to the desired flight model but the cruise attitude of the plane is too nose high, which I'd describe as flying as if the plane was still parked on the runway. I'm sure it was my rookie error that I didn't work out what was going on until after completing a huge amount of work on the flight model.

Is there an EASY way in the .cfg settings to tell MSFS I'd like the pitch relationship of the flight model and the 3D model to be adjusted, or would it be easier to go back to the modeller and just rotate the model (I can re-do the contact points but at least that doesn't mess with the flight model).

I've experimented with flight_model.cfg [AIRPLANE_GEOMETRY] wing_incidence and htail_incidence (I figured if I just add the same value to both the plane would fly at a new attitude but everything else would be the same, but my limited testing so far seems to disprove that. I've seen old posts where people suggest changing cruise_lift_scalar to alter the cruising nose position but that definitely alters the flight model which is not what I want.
 
If you want the fuselage to be horizontal at a particular speed, weight etc, then place the wing on the fuselage at an angle equal to the angle of attack it experiences at those conditions. That will lower the nose so when you fly level at those conditions the fuselage will be horizontal. As to the htail incidence make it zero.
Roy
 
Because of the way that wing lift coefficient is specified with respect to AOA, you will have to move the lift curve sideways in its table. For example if you have a symmetrical non-cambered airfoil it will have zero lift at zero AOA. If you use the table as it is you will fly level with the nose up by the amount of the AOA required to give enough lift for level flight. If you want the fuselage to be horizontal you should move the lift sideways so that the zero AOA has that amount of lift coefficient. This means that zero lift will occur at some negative value of AOA. The reason is that wing incidence in the aircraft config file has no effect. It is one of many entries that makes the file look complete but has no function. Same with htail incidence.
Roy
 
thanks Roy but FYI in MSFS both [AIRPLANE_GEOMETRY] wing_incidence and [AIRPLANE_GEOMETRY] htail_incidence have a huge impact on the flight model - that's changed since FSX. The htail change is like a trim adjustment on steroids, and the wing adjustment has the kind of impact you'd expect but there are second-order effects kick in which I suspect (but haven't done enough testing) are related to MSFS simulating the lift (maybe) & drag (definitely) of other aircraft parts.

I did suspect an 'aerodynamic' solution was going to be to re-do the wing lift/alpha curve, and that would then impact the rest of the flight model (because MSFS would simulate the plane in a different orientation, the drag of every surface would change). I don't want MSFS to do that, I just want the alignment of the 3D model versus the flight model adjusted in pitch.

In my case the flight model is as already close to what I want but I just misunderstood the orientation of the 3D model, so the visible pitch error in the 3D model (about 5 degrees) is the same at every phase of the flight. It turned out the modeller could rotate the model in about 10 seconds so we've done that.

Of course the orientation of the 3D model makes NO difference to the flight model at all*, and I could change the plane to a brick or fly the plane pointing upwards if I wanted, but I was hoping there was a parameter that could orient the flight model to the 3D model without having additional aerodynamic side effects -with the benefit of your experience it seems almost certain the answer to that is "no".

*I lied, there is a difference during the ground run while all the wheels are in contact with the ground.
 
I wish I could help you, but I see that we're struggling about the same points. It makes me feel better to see that I'm not alone... 😂
 
as always, get all your inputs correct first, then if you still have a problem (Mach lift is one of the 3 bugs in FSX/P3D aerodynamics) then and only then should you start coming up with tricks and band-aids. If the data is entered correctly and the model is referenced correctly, it will fly correctly. I don't know what bugs FS20 has yet, but I assume they are the same.

The easiest way to tell is do a test run at MACH 0.50 or less. If your pitch is off your airfile input is off.
 
Sorry I need to bump this, as my modelling partner has just re-done the Blender model as part of an update for the same freeware aircraft, and has once again set the pitch orientation of the MODEL (the BLENDER 3D MODEL) to be seriously out-of-alignment with what MSFS expects. If it makes the problem more obvious, imagine he has re-designed the model so that the nose is now pointing 45 degrees skyward IN BLENDER COORDINATES. I think I need to emphasise this is nothing to do with aerodynamics, as my plane would fly equally well with the model of a brick wrapped around it.

The question is can I ROTATE the alignment of the model with respect to the MSFS flight model (imagine I want the brick to fly vertically upright instead of horizontal). A solution that we know works is to go back into Blender and rotate the 3D model about the X axis and, lo, that is how it will look in MSFS but my partner says that will require every animation to be re-done in Blender. Please note the 3D model of the brick vertical or horizontal has no bearing on the lift or friction generated by the flight model, and there is no orientation of the brick which is 'correct' for a flying brick.

MSFS flight_model.cfg has parameters that can TRANSLATE the 3D model relative to the flight model in the X, Y, and Z directions by setting the 'reference datum point' appropriately, but I can't see any equally simple mechanism that would ROTATE the 3D model around the X axis (i.e. in pitch).

You'd think there must be a convention of what zero PITCH of the model in Blender relates to in FSX/MSFS, but I haven't seen any discussion of this. As far as I can tell you could reasonably model the plane as parked on the runway (i.e. nose-up for a tail dragger) or model the same plane as if it is in cruise. Say the model was 90 degrees out, I don't think it is possible to design a flight model that 'works' using the correct dimensions, i.e. the fuselage drag would be very high (i.e. I've tried setting the angle of attack of the main wing and elevator to adjust the pitch of the model in cruise but that is NOT the same as rotating the 3D model as a whole load of secondary aerodynamic effects kick in.

Apart from the impact on the flight model, you can 3D model the plane in any reasonable pitch orientation and the alignment on the ground will be sorted out by suitable choice of contact points and I wonder if some people model a plane tail down, and others with the fuselage horizontal and after they've tweaked the flight model it looks ok when it flies. But as far as I can tell with the same dimensions and coefficients (i.e. the 'correct values') there is no way those planes would fly at the same visible pitch unless some other adjustment was possible somewhere.

Apologies for sounding clueless but 3D modelling isn't my thing.
 
As far as I can tell, Asobo expects the 3D model to be positioned and oriented correctly in the flight attitude. They have not added a provision to correct this in the config.

It's not difficult to rotate the entire model and retain the animations in Blender. Just add a root empty object, parent everything with keep transform and the animations will become relative to that parent. This the same technique needed if you happen to need to change the scale of your entire model.
 
sal1800 said:
It's not difficult to rotate the entire model and retain the animations in Blender. Just add a root empty object, parent everything with keep transform and the animations will become relative to that parent. This the same technique needed if you happen to need to change the scale of your entire model.
Click to expand...
thanks for this - I'll pass it along to my buddy.
 
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