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Old 4th Jan 2013, 18:36
  #32 (permalink)  
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Join Date: Jun 2009
Location: florida
Age: 81
Posts: 1,611
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Salute!

Thank you Doze and Nuts to add the technical and aero stuff.

Our small jet used "stby gains" when we lost the air data. The stby gain for total pressure was basically sea level 14.7 psi, dynamic pressure was about 300 knots gear up and maybe 160 or 180 knots with gear down. The ratio was what HAL used to determine control surface deflection and rate. So like the 'bus, we had a "heavy stick" unless going the speed of stink.

Remember that the FBW control input never commands absolute surface movement rate nor position unless in the 'bus "direct" mode. We didn't have that option. So the biggie is the gains determine the rate of movement of the control surfaces. Body rates are blended with existing gee until reaching the commanded gee. This prevents a "rough" ride and helps to prevent overshooting your desired AoA/attitude. Once getting to your desired pitch attitude, relaxing the stick allows the system to maintain the gee ( one gee corrected for pitch attitude in the 'bus, and trimmed gee in our little jet).

Still seems like many here do not fully understand the control law implementation, and the plethora of reversion modes in the 'bus is still confusing to this old fart.
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