Simviation Forum - Center of gravity trouble ?

Apr 6^th, 2004 at 4:47pm

Woodylepic Offline
Colonel
Quebec Canada

Posts: 330

I realy dont enderstand what is wrong in this aircraft.cfg Sad

i have recalculate hall the airplane geometry and have change all the data you have tel to me to change.

whene my 3 fuel tank are empty the plane still not flyable and the tail drager is under the runway (i have check the data of the tail position in gmax whit the tape im sure all is set at good place Roll Eyes

whene the plane is full of fuel the tail in under ground and plane still not flyable goinf left right Grin

the contact point is at good place i have checked in gmax 5 time whit tape

the 2 bright light you see is my reference datum the right one. and my C.o.G the left one

whene i put the center of gravity or the ref datum at 7.24 ft ahead the wing
the plane seem to be flyable ??? but the plane not landable

in gmax my plane wing is set at the crossline (1/4 edge of the front wing) like the fs2004 sdk jenny.gmax file

and exterior and interior pivot point is set at same place at x=0.00 y=0.00 z=00.00 on cross line

here my aircraft.cfg rewrited whit your new data

[fltsim.0]
title=Levasseur_PL8
sim=Levasseur_PL8
model=
panel=
sound=
texture=
kb_checklists=Levasseur_PL8_check
kb_reference=Levasseur_PL8_ref
atc_id=Levasseur PL8
atc_id_color=0xffffffff
ui_manufacturer=Levasseur
ui_type=PL 8 "Oiseaux Blanc"
ui_variation=""
description="Dérivé du Levasseur triplace PL4 ( avion de reconnaissance) de l'aéronavale, le PL8

[General]
atc_type=Levasseur
atc_model=PL8
editable=0
performance="Vitesse maximale\n120 mph 104 noeuds 193 km/h\n\nVitesse de croisière\n103 mph 89 noeuds 165 km/h\n\nMotorisation\nLorraine 12Ed 450 CV\n\nHélice\nBipale, à pas fixe\n\nAutonomie maximale\n4 349 mille 7 000 km\n\nCapacité en carburant\n1064 gal u.s 4 025 litre\n\nPoids à vide\n4 199 livres 1 905 kg\n\nPoids total maximal\n11 089 livres 5 030 kg\n\nLongueur\n32 pieds, 9,75 m\n\nEnvergure\n47 pied, 10 pouces 14,60 m\n\nHauteur\n12 pied, 9 pouces 3,89 m\n\nNombre de places\n2\n\nCharge utile\n390 livres 177 kg"

[WEIGHT_AND_BALANCE]
max_gross_weight=11089 // (pounds)
empty_weight=4199 // (pounds)

reference_datum_position=0.00, 0.0, 0.0 // (feet) distance from FlightSim Reference position: (1/4 chord, centerline, waterline)
empty_weight_CG_position=0.00, 0, 0 // (feet) longitudinal, lateral, vertical distance from specified datum

max_number_of_stations=4

station_load.0="175.0, -10.77, -0.81, 0.94, Pilote" //Weight, longitudinal, lateral, vertical distance from specified datum
station_load.1="175.0, -10.82, 0.81, 0.89, Navigateur" //Weight, longitudinal, lateral, vertical distance from specified datum
station_load.2="20.0, -10.25, -0.81, -0.67, Bagage Pilot" //Weight, longitudinal, lateral, vertical distance from specified datum
station_load.3="20.0, -10.26, 0.81, -0.67, Bagage Navigateur" //Weight, longitudinal, lateral, vertical distance from specified datum

;Moments of Inertia
empty_weight_pitch_MOI=5305.28 //MOI= moment of inertie
empty_weight_roll_MOI=5152.86 //MOI= moment of inertie
empty_weight_yaw_MOI=10458.14 //MOI= moment of inertie
empty_weight_coupled_MOI=0.0

[flight_tuning]
cruise_lift_scalar=1.0
parasite_drag_scalar=1.0
induced_drag_scalar=1.0
elevator_effectiveness=1.0
aileron_effectiveness=1.0
rudder_effectiveness=1.0
pitch_stability=1.0
roll_stability=1.0
yaw_stability=1.0
elevator_trim_effectiveness=1.0
aileron_trim_effectiveness=1.0
rudder_trim_effectiveness=1.0

[Flaps.0]
type=1
span-outboard=0.00
extending-time=1.00
system_type=3
flaps-position.0=0.0
flaps-position.1=180.0

[GeneralEngineData]
engine_type=0 //0=Piston, 1=Jet, 2=None, 3=Helo-Turbine, 4=Rocket, 5=Turboprop
Engine.0=9.34, 0.0, 0.0 //(feet) longitudinal, lateral, vertical distance from reference datum
fuel_flow_scalar=0.932 //Fuel flow scalar
min_throttle_limit=0.0 //Minimum percent throttle. Generally negative for turbine reverser
master_ignition_switch=1

« Last Edit: Apr 7^th, 2004 at 5:17pm by Woodylepic »

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Reply #1 - Apr 6^th, 2004 at 8:48pm

Milton Offline
Colonel
Props forever!

Gender:
Posts: 301

Woody,

Hard to say looking at just this info but one issue may be the crash point#8 is 9 feet behind the rear wheel and likely underground.

You should probably place the CoG at 0,0,0 with the reference point if it is at 1/4 chord.

Have you tried using a navlight in the lights section to double check all your critical points? I highly recommend doing this.

If your ref point is 1/4 chord, it seems your main gear is too far forward at +7.07 and your tail wheel would be about where the pilot is sitting.

Wing area seems too small. For a 50 foot wing at about 7-8 feet, it should be more like 350-400 square feet. How are you accounting for a bi-plane?

Wing chord of 4.17' is too small I would think. Maybe more like 7-8 feet.

Sometimes it helps to draw this out on paper and record the measurements so you can visually see results.

Milton&&Dash 7, Aero Commanders, Howard 500, D18S, Spartan, XP47J, Beechcraft A28 (Grizzly)

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Reply #2 - Apr 6^th, 2004 at 9:41pm

Woodylepic Offline
Colonel
Quebec Canada

Posts: 330

//moteur loraine 12 ed
// poid a vide 390 kg
//480 ch a 2300 tr/mn
// cylindrer 25 litre (127 cubic inches)
// regime 1100 tr/mn economique, 2300 tr/mn decolage 1850 tr/mn normale
//compression 6
//consomation dessence (sans reducteur 103kg/heure 145 litre/heure densiter .715kg/l (a plein regime)
//essence 4025 litre/40 heure=100.625 litre/heure
//densiter fs2004 gasoline=.718 kg/l

[piston_engine]
power_scalar=1.0 //Piston power scalar
cylinder_displacement=127 //Cubic inches per cylinder
compression_ratio=6.0 //Compression ratio
number_of_cylinders=12 //Number of cylinders
number_of_magnetos=2 / /Number of magnetos on the piston engine. Only values of 1 and 2 are supported.
max_rated_rpm=2300 //Max rated RPM
max_rated_hp=480 //Max rated HP
fuel_metering_type=1 //0=Fuel Injected, 1=Gravity Carburetor, 2=Aerobatic Carburetor
cooling_type=1 //0=Cooling type Air, 1=Cooling type Liquid
normalized_starter_torque=0.3 //Starter torque factor
turbocharged=0 //Is it turbocharged? 0=FALSE, 1=TRUE
max_design_mp=0 //Max design manifold pressure, (inHg)
min_design_mp=0 //Min design manifold pressure, (inHg)
critical_altitude=0 //Altitude to which the turbocharger will provide max design manifold pressure (feet)
emergency_boost_type=0 //0=None, 1=Water Injection, 2=Methanol/Water injection, 3=War Emergency Power
emergency_boost_mp_offset=0 //Additional manifold pressure supplied by emergency boost
emergency_boost_gain_offset=0 //Multiplier on manifold pressure due to emergency boost
fuel_air_auto_mixture=1 //Automixture available? 0=FALSE, 1=TRUE
auto_ignition=0 //Auto-Ignition available? 0=FALSE, 1=TRUE
max_rpm_mechanical_efficiency_scalar=1.0 //Scalar on maximum RPM mechanical efficiency
idle_rpm_mechanical_efficiency_scalar=1.0 //Scalar on idle RPM mechanical efficiency
max_rpm_friction_scalar=1.0 //Scalar on maximum RPM friction
idle_rpm_friction_scalar=1.0

[propeller]
thrust_scalar=1.0 //Propeller thrust scalar
propeller_type=1 //0=Constant Speed, 1=Fixed Pitch
propeller_diameter=12.0 //Propeller Diameter, (feet)
propeller_blades=2 //Number of propeller blades
propeller_moi=22.00 //Propeller moment of inertia
beta_max=0.0 //Maximum blade pitch angle for constant speed prop, (degrees)
beta_min=0.0 //Minimum blade pitch angle for constant speed prop, (degrees)
min_gov_rpm=1000 //Miminum governed RPM
prop_tc=0.01 //Prop time-constant
gear_reduction_ratio=1.0 //Propeller gear reduction ratio
fixed_pitch_beta=19 //Fixed pitch angle of fixed pitch prop, (degrees)
low_speed_theory_limit=80 //Speed at which low speed theory becomes blended in (feet/second)
prop_sync_available=0 //Prop synchronization available? 0=FALSE, 1=TRUE
prop_deice_available=0 //Prop de-icing available? 0=FALSE, 1=TRUE
prop_feathering_available=0
prop_auto_feathering_available=0
beta_feather=0.000000
power_absorbed_cf=0
defeathering_accumulators_available=0
prop_reverse_available=0 //Prop reverse available? 0=FALSE, 1=TRUE
minimum_on_ground_beta=0 //Miminum pitch angle on ground, (degrees)
minimum_reverse_beta=0 //Minimum pitch angle in reverse, (degrees)

[contact_points]
point.0=1, 0.46, -3.45, -6.75, 1200, 0, 1.29, 0.0, .400, 2.5, 1.0, 1.5, 1.5, 2.0, 0.0, 0.0 ;ROUE GAUCHE
point.1=1, 0.46, 3.45, -6.75, 1200, 0, 1.29, 0.0, .400, 2.5, 1.0, 1.5, 1.5, 3.0, 0.0, 0.0 ;ROUE DROITE
point.2=3, -21.63, 0.0, -1.51, 1200, 0, 1.0, 0.0, 0.400, 2.5, 0.595, 2.0, 2.0, 7.0, 0.0, 0.0 ;PATE QUEU
//point.3=4, 1.61, -2.07, -1.00, 800, 0, 0.0, 0.0, 0.000, 0.0, 1.0, 1.5, 1.5, 2.0, 0.0, 0.0 ;FLOATEUR AVANT GAUCHE
//point.4=4, 1.61, 2.07, -1.00, 800, 0, 0.0, 0.0, 0.000, 0.0, 1.0, 1.5, 1.5, 3.0, 0.0, 0.0 ;FLOATEUR AVANT DROITE
//point.5=4, -14.31, -4.5, -0.89, 1600, 0, 0.00, 0.0, 0.95, 2.5, 0.65, 0.0, 0.0, 7, 0.0, 0.0 ;FLOATEUR QUEU GAUCHE
//point.6=4, -14.31, 4.5, -0.89, 1600, 0, 0.00, 0.0, 0.95, 2.5, 0.65, 0.0, 0.0, 7, 0.0, 0.0 ;FLOATEUR QUEU DROITE
point.7=2, 9.34, -0.00, 0.00, 1800, 0, 0.00, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 5, 0.0, 0.0 ;SCRAP POINT
point.8=2,-23.82, 0.00, 0.00, 1800, 0, 0.00, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 6, 0.0, 0.0
point.9=2, -2.02, -23.67, 0.00, 1800, 0, 0.00, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 7, 0.0, 0.0
point.10=2, -2.02, 23.67, 0.00, 1800, 0, 0.00, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 7, 0.0, 0.0

static_pitch=13.86
static_cg_height=5.81
gear_system_type=3

[Views]
eyepoint=-11.11, -0.81, 2.74

« Last Edit: Apr 7^th, 2004 at 5:26pm by Woodylepic »

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Reply #3 - Apr 6^th, 2004 at 10:09pm

Woodylepic Offline
Colonel
Quebec Canada

Posts: 330

[LIGHTS]
//Types: 1=beacon, 2=strobe, 3=navigation, 4=cockpit, 5=landing x,y,z
light.1=3, 0.46, -3.45, -6.75, fx_navred
light.2=3, 0.46, 3.45, -6.75, fx_navgre
light.3=3, -21.63, 0.0, -1.51, fx_navwhi
light.4=3, 0.00, 0.0, 6.00, fx_navwhi
light.5=3, -1.2, 0.00, 6.00, fx_navwhi

[Radios]
// Radio Type=availiable, standby frequency, has glide slope
Audio.1=1
Com.1=1, 0
Nav.1=0, 0, 0
Adf.1=1
Transponder.1=0
Marker.1=0

[keyboard_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=200, 1000
aileron=200, 1000
rudder=200, 1000

[direction_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=4
direction_indicator.0=1,0
direction_indicator.1=2,0

[attitude_indicators]
//Type: 0=None, 1=Vacuum Gyro, 2=Electric Gyro
attitude_indicator.0=0

[turn_indicators]
//Type: 0=None, 1=Electric Gyro, 2= Vacuum Gyro
turn_indicator.0=0

[EFFECTS]
wake=fx_wake
water=fx_spray
dirt=fx_tchdrt
concrete=fx_sparks
touchdown=fx_tchdwn_s, 1
startup=fx_engstrt_vega
windshield_rain_effect_available=0       //Do not draw rain on this windshield

[electrical]
max_battery_voltage=0
generator_alternator_voltage=12
max_generator_alternator_amps=35
autopilot=0, 5 , 17.0
light_nav=0, 5 , 17.0
light_panel=0, 5 , 17.0

[fuel]
Center1=-5.74, 0.00, .653, 354, 0.0 //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
Center2=-3.10, 0.00, .653, 354, 0.0 //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
Center3=-0.48, 0.00, .653, 354, 0.0 //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)

fuel_type=1    //Fuel type: 1 = Aviationgas, 2 = JetA
number_of_tank_selectors=3
electric_pump=0

« Last Edit: Apr 7^th, 2004 at 4:56pm by Woodylepic »

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Reply #4 - Apr 6^th, 2004 at 11:14pm

SilverFox441 Offline
Colonel
Now What?
Mississauga, Ontario, Canada

Gender:
Posts: 1467

Your settings:

vtail_area=3.12    //Square feet
vtail_span=3.17       //Feet, tip to body

and

htail_area=4.38    //Square feet
htail_span=16.24 //Feet

Don't seem to make sense.

For the VTailnumbers to make sense the Vtail would have to have a chord of less than 1'! (actually about 11.8 inches) Judging from your image the real chord is in the area of 4-5 feet. This would give you an area of 12.5-15 square feet. This would make the plane more stable in yaw.

It looks like a similar area miscalculation may have been made in the horizontal numbers.

Should make the plane more flyable.

Steve (Silver Fox) Daly

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Reply #5 - Apr 6^th, 2004 at 11:49pm

Woodylepic Offline
Colonel
Quebec Canada

Posts: 330

[airplane_geometry]
wing_area=775.81    //Square feet
wing_span=47.89 //Feet
wing_root_chord=8.10    //Feet
wing_dihedral=2.60 //Degrees
wing_incidence=2.10 //Degrees
wing_twist=0.0 //Degrees
oswald_efficiency_factor=0.6 //Measure of lift effeciency of wing
wing_winglets_flag=0    //Are winglets available?
wing_sweep=2.3 //Degrees, wing leading edge
wing_pos_apex_lon=2.02    //Feet, longitudinal distance from reference point, negative going aft
wing_pos_apex_vert=1.94 //Feet, vertical distance from reference point, positive going up

htail_area=77.38    //Square feet
htail_span=16.23 //Feet
htail_pos_lon=-19.17    //Feet, longitudinal distance from reference point, negative going aft
htail_pos_vert=-1.37 //Feet, vertical distance from reference point, positive going up
htail_incidence=0 //Degrees
htail_sweep=26.0 //Degrees, horizontal tail leading vtail_area    = 18.0 //Square feet

vtail_area=38.76    //Square feet
vtail_span=6.22    //Feet, tip to body
vtail_sweep=25.0 //Degrees, vertical tail leading edge
vtail_pos_lon=-19.17       //Feet, longitudinal distance from reference point, negative going aft
vtail_pos_vert=2.62       //Feet, vertical distance from reference point, positive going up

elevator_area=38.00       //Square feet
aileron_area=20.51    //Square feet
rudder_area=17.66    //Square feet
elevator_up_limit=25.0 //Degrees
elevator_down_limit=25.0 //Degrees
aileron_up_limit=16.0 //Degrees
aileron_down_limit=16.0 //Degrees
rudder_limit=30.0 //Degrees
elevator_trim_limit=0.0 //Degrees
spoiler_limit=0.01 //Degrees
spoilerons_available=1    //Spoilerons Available?
aileron_to_spoileron_gain=0 //Aileron to spoileron gain
min_ailerons_for_spoilerons=0       //Degrees
min_flaps_for_spoilerons=0    //Minimum flap handle position when spoilerons activate

[Reference Speeds]
flaps_up_stall_speed=62.5 //Knots True (KTAS)
full_flaps_stall_speed=62.5 //Knots True (KTAS)
cruise_speed=89.09    //Knots True (KTAS)
max_indicated_speed=200 //Red line (KIAS)

[autopilot]
autopilot_available=1
flight_director_available=0
pitch_takeoff_ga=0.0
default_vertical_speed=700.000000
autothrottle_available=0
direction_indicator=1
max_pitch=10.000000
max_pitch_acceleration=1.000000
max_pitch_velocity_lo_alt=2.000000
max_pitch_velocity_hi_alt=1.500000
max_pitch_velocity_lo_alt_breakpoint=20000.000000
max_pitch_velocity_hi_alt_breakpoint=28000.000000
max_bank=25.000000
max_bank_acceleration=1.800000
max_bank_velocity=3.000000
max_throttle_rate=0.100000
nav_proportional_control=9.000000
nav_integrator_control=0.250000
nav_derivative_control=0.000000
nav_integrator_boundary=2.500000
nav_derivative_boundary=0.000000
gs_proportional_control=9.520000
gs_integrator_control=0.260000
gs_derivative_control=0.000000
gs_integrator_boundary=0.700000
gs_derivative_boundary=0.000000
yaw_damper_gain=0.0
default_bank_mode=2    //Default to Heading Hold

[forcefeedback]
ground_bumps_magnitude1=2600 ; 0 - 10000
ground_bumps_angle1=8900    ; 0 - 35999 degrees
ground_bumps_intercept1=5.0
ground_bumps_slope1=0.6
ground_bumps_magnitude2=1200 ; 0 - 10000
ground_bumps_angle2=9100    ; 0 - 35999 degrees
ground_bumps_intercept2=0.085
ground_bumps_slope2=0.65
crash_magnitude1=10000 ; 0 - 10000
crash_direction1=01000 ; 0 - 35999 degrees
crash_magnitude2=10000 ; 0 - 10000
crash_direction2=9000 ; 0 - 35999 degrees
crash_period2=75000    ; in microseconds
crash_duration2=3500000       ; in microseconds

[stall_warning]
type=1

[exits]
number_of_exits=0

[brakes]
toe_brakes_scale=1.000000
parking_brake=1

[hydraulic_system]
normal_pressure=0.000000

in the fs2004 sdk he the formule for measuring the yaw is

MOI = EmptyWeight * (D^2 / K)

Pitch Roll Yaw
D = Length (feet) Wingspan (feet) 0.5* (Length+Wingspan)

K = 810 1870 770

MY LENGT= 31.89968 FEET
MY SPAN IS 47.88748 FEET

MY empty_weight_yaw_MOI IS 31.9878+47.89968=79.88748 FEET *.5=39.94374^2=1595.502365/770=2.072080994*4199.763=8702.249091

but your wright i have check some other aircraft file and the yaw MOI is the sum of the pitch and roll moi i will try hall ou said and give you info soon thank very much !

« Last Edit: Apr 7^th, 2004 at 5:22pm by Woodylepic »

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Reply #6 - Apr 7^th, 2004 at 1:01am

Milton Offline
Colonel
Props forever!

Gender:
Posts: 301

Woody,

The vtail numbers and rudder still look low to me. My guess is rudder is around 18 sq. feet and vtail around 36'. Include all of the vtail and rudder area together above and below the htail.

Your empty_weight_yaw_MOI=8702.24 looks very low. This might be a big part of your issue. It is typically about equal to the sum of your pitch and roll moi numbers ... in this case about 10460.

Also, check your realism settings in FS for p-factor and torque ... drop to 50% and try it.

Also, in the aircraft.cfg look at these options:

Contact Points Section
tailwheel_lock = 1

Flight Tuning Section
torque_on_roll = 1
P_factor_scaler=0.1

In the .cfg, I usually include the rudder area with the vtail area.

The wing apex longitude should be the positive distance from ref point (assuming 1/4 chord-MAC) to the leading edge of the wing. This will help eliminate some heavy nose feel.

Hope this helps.

Milton&&Dash 7, Aero Commanders, Howard 500, D18S, Spartan, XP47J, Beechcraft A28 (Grizzly)

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Reply #7 - Apr 7^th, 2004 at 10:55am

Woodylepic Offline
Colonel
Quebec Canada

Posts: 330

i have remake all my geometry to day check up there

pls tel me if you see some error

i have a question here

i have 2 wing so i must double my wing area that right ?

if yes i have set wing area at 775.81 ft ^2 (387.905ft^2 *2)
some plane in c.o.f seem to have only 1 wing the jenny have 1 wing area but the viker vimy is acurate whit 2 wing area ?

« Last Edit: Apr 7^th, 2004 at 5:21pm by Woodylepic »

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Reply #8 - Apr 9^th, 2004 at 10:15pm

Woodylepic Offline
Colonel
Quebec Canada

Posts: 330

Have find the trouble the tail below ground was my center of gravity at 0.0 to ahead and my laterale instability was the fault of my .air file i have made some change in my air file my plane is now flyable thank very much for your help.

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