AI helicopters: how to reduce pitch at takeoff

[Holger 0]

Hi everyone:for the last couple of days I have put the final touches on a custom set of .air and .cfg file for AI helicopters. I'm pretty happy with the results so far: takeoff and landing 150-200ft at ~35kts, cruise speed 90-130kts, and no crashes! I've also designed a bunch of custom AFCAD "heliports" that minimize taxiing including, as of this afternoon, a working AFCAD file for one of the add-on aircraft carriers -- whoopie, helicopters on catapults ;-)The one remaining "misbehavior" of the AI choppers (other than the inevitable lack of a nice simple hover) is their tendency for a very steep nose-up pitch (up to -30 degrees) for a few seconds after takeoff (see the attached screen shot). It's related to the low weight I need to specify (550 pounds) to get them to take off quickly, as well as unusually high levels for parameters, such as elevator trim and limits, Oswald, etc.I have tried different settings and combinations for any of the parameters in the aircraft.cfg file I could think of, including flight tuning, center of gravity, and MOI. None of those helped with reducing the steep pitch. Can anyone think of something I might have missed? So far I have done all the tweaking in the aircraft.cfg file; the only change I made to the .air file is to set breaking strength to max -- which throws the pilots right out of the cockpit ;-) and flaps lift was set at a very low 0.01 already. Any ideas/suggestions are highly appreciated!I believe an added difficulty is that these are AI aircraft and the FS ATC always guides them to reach cruise altitude as quickly as possible. Cheers, Holgerhttp://forums.avsim.com/user_files/3454.jpg

[wsieffert 0]

Beats hanging in the straps like we did in H-3 (Sikorsky S-61). I can't answer you why or how! If you are using the non-helicopter setting in the air file, it probably manages the aircraft like a fixed wing, i.e., rotate nose up to altitude.MS next version of FS has the R-22, it will be interesting to see how they managed a non-jet engine helicopter.

[Guest]

Hi there,I have also been working on AI CHOPPPERS. I have a bell JetRanger with gtow of 3200 lbs and empty weight of 2100 lbs. It takes off in a distance of 150 to 200 ft. I am using the C208 AIR file with modified wing length and area, and modified prop numbers. The cruise speed is unrealistic for Bell 206. I have been trying to solve the pitch problem as well. I was wondering if moving the c of g forward to lower the nose might work. What do you think?my aircraft config file appears below. As you can see, I have tried several different AIR files over a period of time.//C208B air file and cfg file used for this experiment. The title "AI TEST BELL HELICOPTER from C172" remains unchanged for the sake of expediency, even though the files are from C208B and not C172.fltsim.0title=AI TEST BELL HELICOPTER from C172//sim=Bell_206B_JetRanger//sim=Cessna172SPsim=cessna208B//sim=Goodyear defendermodel=panel=sound=texture=kb_checklists=Bell_206B_JetRanger_checkkb_reference=Bell_206B_JetRanger_refprop_anim_ratio=-1.76atc_id_color=0xc6eff7ffatc_id=CGTNSatc_model=ui_manufacturer=Bellui_type=HB06ui_variation=Blue with whitevisual_damage=1description=The Bell 206 series has accumulated an astounding array of impressive statistics. More than 6,000 JetRangers are flying worldwide in roles as diverse as corporate transportation, police surveillance, and United States Army aviation training. The series has flown over 26 million flight hours, and a few JetRangers are flying with more than 30,000 hours on their airframes.atc_flight_number=atc_airline=atc_heavy=0Generalatc_type=JETRANGERperformance=Cruise Speed tn115 kts 132 mph 213 km/hnnEnginenAllison 250-C20J 420 shpnnMaximum Rangen435 nm t 500 m 805 kmnnService Ceilingn20,000 ft 6,096 mnnHovering Ceilingn19,600 5,974 mnnFuel Capacityn91 U.S. gal 344 LnnEmpty Weightn1,640 lb 744 kgnnMaximum Gross Weightn3,200 lb 1,451 kgnnMaximum Gross Weight (External Loading)n3,350 lb 1,519 kgnnLengthtn31.2 ftt 9.51 mnnRotor Spann33.3 ftt 10.15 mnnHeightn11.7 ftt 3.51 mnnSeating tnUp to 5 nnUseful Loadtn1,498 lbt 679 kgneditable=1atc_model=HB06WEIGHT_AND_BALANCEmax_gross_weight= 3200.000empty_weight= 2100.000reference_datum_position= 16.200, 0.000, 0.000empty_weight_CG_position= -15.400, 0.000, 0.000max_number_of_stations=50station_load.0= 170.000, -11.300, -1.500, 0.000station_load.1= 170.000, -11.300, 1.500, 0.000station_load.2= 170.000, -13.900, -1.500, 0.000station_load.3= 170.000, -13.900, 1.500, 0.000station_load.4= 170.000, -17.200, -1.500, 0.000station_load.5= 170.000, -17.200, 1.500, 0.000station_load.6= 170.000, -20.200, -1.500, 0.000station_load.7= 170.000, -20.200, 1.500, 0.000station_load.8= 170.000, -23.200, -1.500, 0.000station_load.9= 170.000, -23.200, 1.500, 0.000station_load.10= 200.000, -16.200, 0.000, -5.000;Moments of Inertiaempty_weight_pitch_MOI= 8874.870empty_weight_roll_MOI= 6026.960empty_weight_yaw_MOI= 11858.540empty_weight_coupled_MOI= 0.000CG_forward_limit= 0.000CG_aft_limit= 1.000flight_tuningcruise_lift_scalar=1.000parasite_drag_scalar=1.000induced_drag_scalar=1.000elevator_effectiveness=1.000aileron_effectiveness=1.000rudder_effectiveness=1.000pitch_stability=1.000roll_stability=1.000yaw_stability=1.000elevator_trim_effectiveness=1.000aileron_trim_effectiveness=1.000rudder_trim_effectiveness=1.000GeneralEngineDataengine_type= 5Engine.0= -4.400, 0.000, 0.000fuel_flow_scalar= 1.120propellerthrust_scalar=0.501propeller_type= 0propeller_diameter= 36.000propeller_blades= 2propeller_moi= 7383.000beta_max= 45.000beta_min= 15.600min_gov_rpm= 25520.000prop_tc= 0.004gear_reduction_ratio= 17.400fixed_pitch_beta= 0.000low_speed_theory_limit= 80.000prop_sync_available= 0prop_deice_available= 1prop_feathering_available= 1prop_auto_feathering_available= 1min_rpm_for_feather= 700.000beta_feather= 88.000power_absorbed_cf= 0.900defeathering_accumulators_available= 0prop_reverse_available= 1minimum_on_ground_beta= 1.000minimum_reverse_beta= -14.000TurbineEngineDatafuel_flow_gain= 0.011inlet_area= 1.000rated_N2_rpm= 35000.000static_thrust= 1500.000afterburner_available= 0turboprop_enginepower_scalar=1.000maximum_torque= 10000.000max_rpm_mechanical_efficiency_scalar=0.501idle_rpm_mechanical_efficiency_scalar=1.000max_rpm_friction_scalar=1.000idle_rpm_friction_scalar=1.000pitot_staticvertical_speed_time_constant=1.0 //Increasing this value will cause a more instantaneous reaction in the VSIRadios// Radio Type=availiable, standby frequency, has glide slopeAudio.1=1Com.1=1, 1Com.2=1, 1Nav.1=1, 1, 1Nav.2=1, 1, 0Adf.1=1Transponder.1=1Marker.1=1LIGHTS//Types: 1=beacon, 2=strobe, 3=navigation, 4=cockpit light.0=3, -16.30, -26.41, 3.35, fx_navredlight.1=3, -16.30, 26.41, 3.35, fx_navgrelight.2=3, -42.28, 0.00, 2.10, fx_navwhilight.3=2, -16.56, -26.51, 3.35, fx_strobelight.4=2, -16.56, 26.51, 3.35, fx_strobelight.5=1, -40.25, 0.00, 10.01, fx_beaconlight.6=4, -11.61, 0.00, 0.98, fx_vclightkeyboard_response//Breakpoint speeds (knots) on the keyboard increments of control surfaces.//Speed at which the incremenet is reduced to 1/2 and 1/8 respectively.elevator=100, 180aileron=200, 1000rudder=200, 1000direction_indicators//1 Type: 0=None, 1=Vacuum Gyro, 2=Electric Gyro, 3=Electro-Mag Slaved Compass, 4=Slaved to another//2 Indicator number of slaving indicator if Type=4direction_indicator.0=3,0//0 Class//1 Longitudinal Position (feet)//2 Lateral Position (feet)//3 Vertical Position (feet)//4 Impact Damage Threshold (Feet Per Minute)//5 Brake Map (0=None, 1=Left, 2=Right)//6 Wheel Radius (feet)//7 Steer Angle (degrees)//8 Static Compression (feet) (0 if rigid)//9 Max/Static Compression Ratio//10 Damping Ratio (0=Undamped, 1=Critically Damped)//11 Extension Time (seconds)//12 Retraction Time (seconds)//13 Sound Type[contact_points]point.0= 1.000, -4.700, 0.000, -5.400, 1500.000, 0.000, 0.500, 22.000, 0.300, 2.500, 0.700, 0.000, 0.000, 0.000, 0.000, 0.000point.1= 1.000, -18.000, -6.000, -5.400, 2500.000, 1.000, 0.500, 0.000, 0.300, 2.500, 0.700, 0.000, 0.000, 2.000, 0.000, 0.000point.2= 1.000, -18.000, 6.000, -5.400, 2500.000, 2.000, 0.500, 0.000, 0.300, 2.500, 0.700, 0.000, 0.000, 3.000, 0.000, 0.000point.3= 2.000, -15.900, -26.000, 3.000, 1800.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 5.000, 0.000, 0.000point.4= 2.000, -15.900, 26.000, 3.000, 1800.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 6.000, 0.000, 0.000point.5= 2.000, -39.230, 0.000, 0.000, 1800.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 9.000, 0.000, 0.000point.6= 2.000, -2.500, 0.000, -2.170, 1800.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 4.000, 0.000, 0.000point.7= 2.000, -42.000, 0.000, 10.000, 1800.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 7.000, 0.000, 0.000max_number_of_points=21static_pitch= 0.240static_cg_height= 5.110Viewseyepoint=-12.1, -1.4, 2.12 //(feet) longitudinal, lateral, vertical distance from reference datumfuelLeftMain= -18.400, -1.100, 2.500, 166.000, 3.600RightMain= -18.400, 1.100, 2.500, 166.000, 3.600fuel_type=2 //Fuel type: 1 = Avgas, 2 = JetAnumber_of_tank_selectors=1 EFFECTSwake=fx_wakewater=fx_spraydirt=fx_tchdrtconcrete=fx_sparkstouchdown=fx_tchdwn_s, 1exitsnumber_of_exits=2exit_rate.0=0.4 ;Percent per secondexit_rate.1=0.4 ;Percent per secondairplane_geometrywing_area= 944.000wing_span= 96.000wing_root_chord= 9.800wing_dihedral= 3.000wing_incidence= 0.000wing_twist= 3.000oswald_efficiency_factor= 0.700wing_winglets_flag= 0wing_sweep= 0.000wing_pos_apex_lon= -16.000wing_pos_apex_vert= 0.000htail_area= 39.000htail_span= 11.700htail_pos_lon= -30.900htail_pos_vert= 0.000htail_incidence= 2.000htail_sweep= 5.000vtail_area= 18.000vtail_span= 4.800vtail_sweep= 45.000vtail_pos_lon= -28.800vtail_pos_vert= 1.500elevator_area= 26.600aileron_area= 18.300rudder_area= 6.700elevator_up_limit= 28.000elevator_down_limit= 21.000aileron_up_limit= 20.000aileron_down_limit= 15.000rudder_limit= 24.000elevator_trim_limit= 19.500spoiler_limit= 20.000spoilerons_available= 1aileron_to_spoileron_gain= 1.000min_ailerons_for_spoilerons= 0.000min_flaps_for_spoilerons= 0.000Reference Speedsflaps_up_stall_speed= 66.000full_flaps_stall_speed= 52.800cruise_speed= 175.000autopilotautopilot_available=1flight_director_available=1default_vertical_speed=1000.0autothrottle_available=0pitch_takeoff_ga=8.000000forcefeedbackgear_bump_nose_magnitude=3000 ; 0 - 10000gear_bump_nose_direction=18000 ; 0 - 35999 degreesgear_bump_nose_duration=250000 ; in microsecondsgear_bump_left_magnitude=2700 ; 0 - 10000gear_bump_left_direction=35500 ; 0 - 35999 degreesgear_bump_left_duration=250000 ; in microsecondsgear_bump_right_magnitude=2700 ; 0 - 10000gear_bump_right_direction=00500 ; 0 - 35999 degreesgear_bump_right_duration=250000 ; in microsecondsground_bumps_magnitude1=1300 ; 0 - 10000ground_bumps_angle1=08900 ; 0 - 35999 degreesground_bumps_intercept1=3.0ground_bumps_slope1=0.20ground_bumps_magnitude2=200 ; 0 - 10000ground_bumps_angle2=09100 ; 0 - 35999 degreesground_bumps_intercept2=1.075ground_bumps_slope2=0.035crash_magnitude1=10000 ; 0 - 10000crash_direction1=01000 ; 0 - 35999 degreescrash_magnitude2=10000 ; 0 - 10000crash_direction2=9000 ; 0 - 35999 degreescrash_period2=75000 ; in microsecondscrash_duration2=2500000 ; in microsecondsFlaps.0type= 1span-outboard= 0.500extending-time= 5.700system_type= 0damaging-speed= 0.000blowout-speed= 0.000lift_scalar= 1.000drag_scalar= 1.000pitch_scalar= 1.000flaps-position.0= 0.000, 0.000flaps-position.1= 10.000, 0.000flaps-position.2= 20.000, 0.000flaps-position.3= 30.000, 0.000yours in simming...Dextersbones

[Guest Kurt]

You can adjust the cruise speed in the .cfg file.[Reference Speeds]flaps_up_stall_speed=68.0full_flaps_stall_speed=54.0cruise_speed=85.0Kurt M

[Holger 0]

Howdy:Kurt: actually, the reference speeds section doesn't seem tohave much of an impact on the achieved cruise speed, i.e., ifthe plane is too powerful it'll fly faster anyway (though itmight deploy spoilers in midflight in an effort to reducespeed). Conversely, if the power isn't there, the plane willnot reach cruise speed. Regarding matters of speed, I've hadbetter results with changing the power_scalar, thrust_scalaror horse power (for piston engines) settings.Dexterbones: thanks for attaching your chopper AI version.I'll give it a try with one of my helicopter models. Thereare so many different options for tweaking that it's alwaysinteresting to see what others came up with.With the help of another chopper AI "addict", Ihave managed to reduce the TO pitch quite a bit, and COG doesindeed play a role in this (though we ended up having toadjust the MOI settings to avoid porpoising or rolling duringparts of the flight. I'm about ready to wrap up what I haveand send it to my beta testers. The files should be availablewithin a couple weeks. I fully expect that there's more thatcan be done to improve AI helicopter flight behavior butbelieve that the file packages will be a good start for the26 different models I've been working with.Cheers, Holger