Angle of attack during straight-and-level flight

I downloaded a Cessna 206 Stationair for FS9. I ported it over to FS8, (which I still use), and converted both to turboprop by substituting the Caravan .air file. All four aircraft fly differently. In each case, I get varying results as to the angle of attack during straight-and-level flight. Some fly slightly nose-down, some slightly nose-up.

I've tried adjusting this by changing the angle of incidence of the wing, and the tailplane, in both the .cfg file and .air file. None of this has had any effect.

Is there a way to adjust the angle of attack during straight-and-level flight?

Elmer J. Fudd

You don't adjust the incidence of the wing. You adjust the horiz stab incidence. The way to do this is to put the ac in Auto Pilot with Alt and Hdg Hold. Then you pause sim, go to aircraft cfg's Airplane Geometry section and make change to Horiz Stab Incidence. I start with '0.123'. Save cfg. Go back to sim, do select aircraft before you un-pause. After it loads, in panel view of course, push 'P' and give it 20 sec's to adjust to level flight. CK pitch trim. If it's '-1.00' then you go back to ac cfg, and change it to '-0.123' (minus). Repeat. Etc. When pitch trim is '0.00' then you got it. BUT as fuel is burned off the pitch trim will change a little. No biggee. It's 99% so be happy with that.

Chuck B

Napamule

I did try that. I started with the Horizontal Stabilizer (that's what I meant when I wrote "tailplane".) It didn't seem to have any effect. Note that I'm trying to adjust the angle of attack, not the pitch trim. One of the planes (the one I most want to use) flies nose high, as if there were something heavy on the tail.

I'm going to try again, maybe with a different computer. With the one I was using, sometimes changes I make mid-flight don't seem to take.

Elmer J. Fudd

I did try that. I started with the Horizontal Stabilizer (that's what I meant when I wrote "tailplane".) It didn't seem to have any effect. Note that I'm trying to adjust the angle of attack, not the pitch trim. One of the planes (the one I most want to use) flies nose high, as if there were something heavy on the tail.

 

I'm going to try again, maybe with a different computer. With the one I was using, sometimes changes I make mid-flight don't seem to take.

 

Elmer J. Fudd

I think you can also adjust the cruise_lift_scalar = 1.00 .

Not a perfect fix as it can change rate of climb etc. But thats what i do because I dont get the other stuff.

Adjusting the htail_incidence in this aircraft did not work. I had used the Caravan .air file, because I could not get the engine to run when I used the original .air file, despite adjusting every engine related parameter I could find, in both the .cfg and .air files.

I ultimately scrapped the idea of using the Caravan .air file, and reverted back to the original .air file. I just kept copying more engine related parameters from the Caravan .air file, including the "unknown" ones. I finally got the engine to run, and the plane flies normally now.

There is still a bit of difference in the angle of the dangle between FS8 and FS9, but aircraft sometimes fly differently in these two sims, even if they are identical aircraft. There are some other differences as well, particularly with residual thrust at idle, (more in the FS8, even with the piston C206, which is inexplicable).

At least now, there is no difference between the two aircraft WITHIN each of the sims, and I'm happy now. At least the tail no longer looks from the spot plane view as if it's dragging its tail through a bog, and I see better in VC view.

Thanks, for the help, guys.

Elmer J. Fudd

Not having FS8, but the real way is to adjust the Cl vs AOA curve in the air file around the AoA of zero degrees. One should be able to calculate the value of AOA in cruise at sea level from the standard aero formula W= Lift= aircraft weight= rho/2 . (v x v) . Cl . Wing area. So rearrange the formula for Cl.

Then look up the Cl vs AoA graph & then read the AoA at that value of Cl. After that move the value of Cl up or down changing the straight line slope....remember you are using angle in radians, value 'x' ; for Cl value 'y' in the graph. This also works for Cm vs AOA as an alternative to changing table 1101 Cmo Pitch moment Coeff at AOA (trim os) = 0

Sounds worse than it reads!

Keith

Keith,

I appreciate the treatise, but most of what you've written is above my pay grade. I'm a pilot, not an engineer. I use AirEd to modify .air files, and it has its limitations. A lot of parameters are just marked "unknown".

At any rate, by reverting back to the original .air file, I've got it working properly.

Regards,

Elmer J. Fudd

Keith,

 

I appreciate the treatise, but most of what you've written is above my pay grade. I'm a pilot, not an engineer. I use AirEd to modify .air files, and it has its limitations. A lot of parameters are just marked "unknown".

 

At any rate,by reverting back to the original .air file, I've got it working properly.

 

Regards,

 

Elmer J. Fudd

Many a time I've found my "improvements" were actually a step or sometimes leap backwards! When in doubt I always first try "by reverting back to the original .air file, I've got it working properly."

Well Done!!

Michael

Keith,

 

I appreciate the treatise, but most of what you've written is above my pay grade. I'm a pilot, not an engineer. I use AirEd to modify .air files, and it has its limitations. A lot of parameters are just marked "unknown".

 

At any rate, by reverting back to the original .air file, I've got it working properly.

 

Regards,

 

Elmer J. Fudd

Elmer, yes a lot of the time reverting can be a marvellous cure, one has to do only 1 thing at a time, which can be very tedious, otherwise something else changes one did not consider. But surely a pilot must have some knowledge of aerodynamics? Anyway glad you got sorted.

Just got me wondering - as I was brought up by my father who owned & maintained his aircraft back in the late '40's through the 50's & into the 60's, flying was in my blood, I then became a design draughtsman & for a short time had a pilots licence - got married & bought a house - that put paid to flying.....so am I a designer or a pilot - or a bit of both? Master of none!

Keith

In each case, I get varying results as to the angle of attack during straight-and-level flight.

Just a technical note -- you're talking about pitch attitude, not angle of attack. Angle of attack is the angle between the chord of the wing and the relative air flow, and it varies as speed changes, among many other factors.

Quite so, Larry. I stand (sit?) corrected. That's what I meant, but the right words didn't come to mind. I should know better than to rely on my memory, but sometimes, I forget.

Regards,

Elmer J. Fudd