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MSFS [SOLVED] Can I correct the pitch attitude of MODEL?

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145
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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.
 

Roy Holmes

Resource contributor
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1,717
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us-virginia
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
 

Roy Holmes

Resource contributor
Messages
1,717
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us-virginia
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
 
Messages
145
Country
unitedkingdom
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.
 
Messages
13
Country
france
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... 😂
 

jx_

Messages
555
Country
unitedstates
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.
 
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