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pitching up (Read 998 times)
19th Oct, 2009 at 10:40am

ukmil   Offline
Spline Extruder
I Love FFDS!

Posts: 125
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ok, need some help here, trying to get my latest aircraft to fly, and it goes ok, on ground, and in the air until it climb above 250 knts. it then starts a nose up climb, up until 450 knts, where it needs 4.5 degrees of trim to get it level again.

how can i combat this?
 

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Reply #1 - 20th Oct, 2009 at 5:32am

Au-MaV   Offline
Inspecteur des Polygonnes
Whatcha lookin at
Adelaide South Australia

Gender: male
Posts: 1956
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Hi
Play with the 1101 pitch setting  Cmo pitch movement Coeff at AOA this sets the trim setting at cruse.
Also check the wing_incidence in the aircraft.cfg if this is at 0 then play with the above,if it has a setting try zeroing it out
Finally check that the engine location up/down is 0,if it has a neg or pos number throttle will effect pitch (this is in relation to the reference_datum_position)
The above is quick and dirty tweaking stuff  Wink 
Wozza
 
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Reply #2 - 29th Oct, 2009 at 10:16am

sergio   Offline
Point Pusher
I love YaBB 1G - SP1!

Posts: 9
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4,5 of trim is not that much. Considering the great flight speed difference it seems to me almost correct.
Nevertheless, if Cm0 is allreday set correctly, there is still the pitiching moment due to speed to consider. I don't know at wich altitude the flight test was done but if one stay low, 450 KIAS equals to Mach 0.6 till almost 0.7. At 10.000 ft you have already Mach 0.9. Therefore I would give a look to table 433 (Increase of Cm0 due to mach number). And perhaps to table 422 too (Cm ih due to mach).

Ciao, Sergio
 
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