Nose down attitude at cruise

[camg]

I've been using Tom's flyable version of the DHC8-100. At cruise, the attitude indicator shows about a 2.5 degree nose down attitude. In other A/C I've been able to adjust the wing_incidence (ie: angle of incidence) in the .cfg file to get the plane to fly nose level, or even a half-to-one degree nose up as one would expect.

The spot plane view from the side also confirms the plane is cruising nose down.

Any ideas on what to adjust to correct this?

Cam

[Tom Goodrick]

Pardon me if I sound bitter about this but I am. You were kidding yourself if you thought changing the wing incidence angle changed the pitch angle in cruise. Microsoft proclaimed proudly that they removed that parameter from FS2004. It was effective before that and we all used it to do just that - get a level attitude in cruise. But they set the wing incidence internally at 1.5 degrees (I know of very few aircraft with such an angle in real life) so that changing that value has no effect. The only way to accomplish this in FS2004 is to shift the center portion of the CL vs AoA table (#404) to the left a few degrees to lower the nose or to the right to raise it. You have to go into the .air file and change the position (angle of attack) of typically 15 of the points in the table from left of zero to stall. This is a lot of fun (the angles are in radians) because it is a "trial and error" process. Sounds like I may have over done the correction I put in. They usually fly too nose high.

This does change slightly with loading - full versus empty cabin. Fuel may also have a slight effect depending on tank location.

There is also an incidence angle for the horizontal stabilizer that does work and has consioderable effect on the trim. Is it possible you changed that on other airplanes and saw a change in the trim angle at cruise? It is best to keep the two problems separate - stabilizer trim relates to control and CL vs AoA relates to longitudinal stability (along with table 573).

There was a big stink about this along with the change in calculation of center of gravity when FS 2004 first came out. We made noise on all the forums. It was a management decision supposedly to make the body angle of attack the only calculation needed. They thought this would simplify the software. Of course we know that the only angles of attack that matter are of the wing and of the horizontal stabilizer. The idea that they could not afford to treat the wing incidence as a variable between aircraft is patently absurd - one classic case of a dumb management decision. Microsoft is becoming known for that.

By the way, there is no variable given by the simulator in flight for wing angle of attack. In making my AoA gauge, I had to calculate it from pitch angle and airspeed components. In that calculation I use the 1.5 degree incidence that Microsoft assumes.

[camg]

You're right, Tom. When I was adjusting the angle of incidence I was in FS2002. As I mentioned in another thread, I fly as much in FS02 as I do in FS04--there are features and A/C I like in both editions.

My apologies for getting the capabilities for each mixed up at times; I know this is supposed to be the FS 2004 forum after all!

I shifted the middle data points in Table 404 to the right 0.035 radians (two degrees of incidence) and now it's flying the way I want. (Actually the fuselage is flying about 0.5 degrees nose up and the attitude indicator is about 0.5 degress nose low, but I'm satisfied.

Thanks for the advice!

[Tom Goodrick]

When you move an aircraft from FS2002 to FS2004, or vica versa, you will see there is a significant shift in the CG position unless you do make certain changes in the aircraft.cfg file. Also, the landing gear may act differently. either use my CG gauge on a panel to see the exact CG location or look at the diagram. A normal CG in FS2002 will be at or forward of the nose in FS2004. The solutions to this are:
1) change the folloeing line in the [airplane_geometry] section:

wing_pos_apex_lon=2.08

from 0 to a small positive distance in feet (about 25% of the mean chord).
2) change the empty CG position very slightly (about + or -0.5 feet)

empty_weight_CG_position = 0.5, 0, 0

Landing gear adjustment is a guess of position and spring constant.

All the aircraft on my web site are set up for FS2004.

When FS2004 came out, I hesitated about getting it because I thought my system would not handle it well. I liked FS2002. But with additional RAM, my system handles FS2004 well enough so I can enjoy the additional scenery detail> switched entirely over to FS2004 and converted all my aircraft as I worked out the conversion process. I am not sure if FS2002 has the same dynamic stability parameters. I began working in that area after switching to FS2004 and trying to spin the J-3 Cub.

[zfly2sky - bgan072]

I realize that this is an old thread but thought I'd throw my 1/2 cents worth in, so I hear by the
"grape vine" or should I say the "forum vine" that you can adjust the cruise level of the aircraft
by accessing the aircraft.cfg and look for the [flight tuning] section, (it is usually beneath the
";Moments of Inertia" and the "max_number_of_stations") and the first one under [flight tuning]
is the "cruise_lift_scalar". It is usually "1.0" but if you change it to .05 or 1.5, up or down can be
achieved. It doesn't take very much at all. I got so many "stuck up" aircraft with their noses in
the air that it just gets intimidating. lol