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Guest richjb

V1 Cuts, Aircraft Controlablity & Aircraft.cfg

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Hello,Thanks again to everyone involved with bring Tinmouse back. Since receiving the package, I've been putting Tinmouse II through it's paces so to speak. As such, I was practicing a few V1 cuts (engine failures after V1 with a continued takeoff). I noticed right away there were several controlablity issues, especially related to whether the Yaw Damper was on or off. With Y/D on, the ability to maintain directional control was nearly impossible after lift-off. With the Y/D off, directional control was possible, but it was extreamely over sensitive with respect to rudder. BTW, I use the PFC jet yoke and the FlightLink professional rudders for my flight control system.While researching this problem, I noticed several items in the AIRCRAFT.CFG file that were either missing or incorrect. One items that was incorrect was the rudder limit:rudder_limit = 40.000While I could not find a conclusive limit from my available sources, looking at other B737 AIRCRAFT.CFG files, the rudder limit should be more on the order of 25.00.For comparison, here's the original [airplane_geometry] section:[airplane_geometry]wing_area = 980.000wing_span = 93.000wing_root_chord = 10.54wing_dihedral = 0.000wing_incidence = 1wing_twist = 0oswald_efficiency_factor = 0.77wing_winglets_flag = 0wing_sweep = 0wing_pos_apex_lon = 4.6376wing_pos_apex_vert = 0htail_area = 312.00htail_span = 30.000htail_pos_lon = -40.0htail_pos_vert = 7.112htail_incidence = 1.50htail_sweep = 35.000vtail_area = 224.000vtail_span = 22.5vtail_sweep = 0.000vtail_pos_lon = -37vtail_pos_vert = 9.25elevator_area = 70.46aileron_area = 13.4rudder_area = 56.2elevator_up_limit = 22.00elevator_down_limit = 18.00aileron_up_limit = 30.000aileron_down_limit = 20.000rudder_limit = 40.000elevator_trim_limit = 17.000spoiler_limit = 60.000aileron_to_spoileron_gain = 3.00min_ailerons_for_spoilerons = 12.50min_flaps_for_spoilerons = 0.0000spoilerons_available = 1Here are changes to this section based on data from Boeing's B737 training books which I have or from Chris Brady's B737 site:[airplane_geometry]wing_area =980wing_span =93.000wing_root_chord =15.5 wing_dihedral =6.0wing_incidence =1wing_twist =-0.5oswald_efficiency_factor =0.77wing_winglets_flag =0wing_sweep =25wing_pos_apex_lon =4.6376wing_pos_apex_vert =0htail_area =338.16htail_span =41.67htail_pos_lon =-40.0htail_pos_vert =7.112htail_incidence =0htail_sweep =30.00vtail_area =224.000vtail_span =20.177vtail_sweep =35.00vtail_pos_lon =-37vtail_pos_vert =9.25elevator_area =70.503 613 229aileron_area =26.9rudder_area =56.1876elevator_up_limit =22.00elevator_down_limit =18.00aileron_up_limit =20.000aileron_down_limit =20.000rudder_limit =25.00elevator_trim_limit =20.000spoiler_limit =60.000aileron_to_spoileron_gain =3.00min_ailerons_for_spoilerons =12.50min_flaps_for_spoilerons =0.0000spoilerons_available =1The FAA Type Certificate Data Sheet does not have flight control angles for the B737. I looked at two other "well-known" B737 packages and the default B737-400 AIRCRAFT.CFG for the rudder_limit used. All of these packages used a rudder_limit value of 25.00 as did the original Timmouse AIRCRAFT.CFG file . I have additional B737 training information on the way, so I hope to confirm that value when these arrive.While these change improved directional control after the V1 cut, the stablity of the flight model was still lacking. The original Charles Fox FDE was more accurate with respect to the yaw axis when rudder was added and suddenly released. The current model swings rapidly when rudder held agains the asymetric engine thrust is suddenly. While there is a pronounced nose swing, my experience in jets says the swing in the current model is excessive. Further, I've notice that virutally no rudder is needed with T/O thrust and the airspeed around 200 kts. while this may be true in level, un acclerated flight at 200 kts (N1 = 60%), it most certainly will not be true with T/O thrust.I have also noticed that when sufficient rudder is used to center the ball (zero yaw), a very strong roll tendency develops. While there should be some roll tendency, this is very much exaggerated with the current model.I have toyed with different MOI values as well. These are the calculated MOI values based on Tom Goodrick's manual, which is based on the forumlas from Professer Jan Roskam (based on a B737 aircraft):empty_weight_pitch_MOI = 1171257.626459empty_weight_roll_MOI = 475451.3775465empty_weight_yaw_MOI = 1651288.3077018empty_weight_coupled_MOI = 1000.00Even with these changes the yaw axis damping is poor. Sometimes it appears that the rudder is "over-powered". To summerize:1) directional control following a V1 cut is nearly impossible with the Y/D on.2) With the Y/D off, directional control is possible, but it is somewhat difficult to balance between too much rudder and not enough.3) At level-off and as speed increases, the amount of rudder required decreases to zero passing about 180 kts. While the rudder should become more effective and control force decrease as the aircraft accelerates, there should still be rudder required if T/O thrust is used. In level flight and thrust set to maintain best L/D speed, the amount of rudder requried to maintain directional control will be minimal.Any thoughts, ides, suggestions on how to improve directional control and yaw stablity for the flight model?Thanks,Rich BollWichita, KS.

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yes, the correct value is 25 degrees.I've send an email for bob and other beta test to see how the aircraft works with the .air and .cfg modified.I will recive a feedback in few days.regards,

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Thanks!Let me know if I can help as well. My email address is richjb@onemain.comBest,Rich Boll

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