Update! MSFS2020 - Beechcraft King Air 350i X Improvement Mod - V.1.13.17.0


Flight model modification version 1.12.13.5:

The book "Quest for Performance: The Evolution of Modern Aircraft" has no data about the King Air 350i. Therefore I use the Cessna 310 II data. The zero-lift drag coefficient CD,0 is 0.0267 and maximum lift-drag ratio (L/D)max is 13.0. The Asobo zero-lift drag coefficient CD,0 is 0.0318 and the measured maximum lift-drag ratio (L/D)max is 15.9, measured with the MSFS 2020 build-in DevMode tool Aircraft Editor, Debug, Sim Polar VhVs. The (L/D)max values differ and I think this is one reason for the "floating above the runway at landing" complains about Asobo flight models. 

MSFS 2020 has no propeller drag and no ground effects. Therefore I reduce (L/D)max by from 13.0 to 10.6. A higher CD,0 value needs a higher thrust_scalar value for the same level flight cruise speed at sea level. As second workaround I use increased gear drag and flaps drag with the drag_coef_gear and drag_coef_flaps parameters. 

[AIRPLANE_GEOMETRY]
wing_incidence = 0 ; const
oswald_efficiency_factor = 0.77 ; const
htail_incidence = 2.5 ; const

[FLIGHT_TUNING]
cruise_lift_scalar = 1 ; const
parasite_drag_scalar = 1.63 ; const
induced_drag_scalar = 1.3 ; 1.2 (sailplane, low power airplane) to 1.5 (piston, turboprop)
flap_induced_drag_scalar = 1.3 ; see induced_drag_scalar
pitch_stability = 0.04 ; const
roll_stability = 0.04 ; const
yaw_stability = 0.04 ; const

[AERODYNAMICS]
drag_coef_zero_lift = 0.03180 ; 0.01 (sailplane), 0.035 (GA plane), 0.05 (aerobatics plane)
compute_aero_center = 0 ; const
aero_center_lift = 0 ; const
lift_coef_at_drag_zero = 0.1 ; const
lift_coef_at_drag_zero_flaps = 0.1 ; const

Engine.0 = 160, 0, 0.5 ; 10, -8.4, 0.5 ; 160, 0, 0.5 ; Offset of the engine from the datum reference point. Each engine location specified increases the engine count (maximum of four engines allowed)
ThrustAnglesPitchHeading.0 = 0, 3 ; 0, 0 ; Thrust pitch and heading angles in degrees ( positive pitch down, positive heading right)
Engine.1 = 160, 0, 0.5 ; 10, 8.4, 0.5 ; 
ThrustAnglesPitchHeading.1 = 0, -3 ; 0, 0 ; 
The 3° ThrustAnglesPitchHeading.X.heading angle together with the Engine.X.longitudial of 160ft result in a distance of engine to center line of 8.4ft. But the engine is 160ft ahead of the airplane ...

cruise_speed = 263 ; 244 ; Max Operating Speed VMO, Sea Level to 21,000 feet
thrust_scalar = 1.43 ; 1
After changing the polar, changing of thrust is needed, too. I give the airplane thrust for 263 KIAS maximum level flight airspeed at sea level.

empty_weight_CG_position = 0.3, 0, 0 ; 1.0, 0, 0 ; Position of airplane empty weight CG relative to reference datum (FEET), z, x, y
Move center of gravity to 20% MAC

flaps-position.0 = 0, -1, 0 ; 0, 0, 0, 0, 0, 0, 0
flaps-position.1 = 20, 202, 1 ; 20, 202, 0.25, 0, 0, 0, 0
flaps-position.2 = 40, 158, 1 ; 40, 158, 1, 0, 0, 0, 0
The flaps drag results from sub-parameter Drag Coeff and flaps angle. Therefore 0 for 0° flaps and 1 for other settings gives linear progression of drag with flaps angle.

lift_scalar = 1 ; 1.43 ; Scalar coefficient to ponderate global flap lift coef (non dimensioned)
drag_scalar = 1 ; 1.43 ; Scalar coefficient to ponderate global flap drag coef (non dimensioned)
pitch_scalar = 1 ; 1.43 ; Scalar coefficient to ponderate global flap pitch coef (non dimensioned)
lift_coef_flaps = 0
drag_coef_flaps = 0.1
I control flaps lift/drag via [AERODYNAMICS] parameters.

wing_pos_apex_lon = -1 ; 0 ; Longitudinal (z) position of wing apex w.r.t reference datum (FEET)
Adjust to 3D model.

fuselage_length = 38.1 ; 42 ; Nose to vtail/htail apex (FEET)
fuselage_diameter = 6.5
fuselage_center_pos = -3, 0, 0.5 ; -1, 0, 0.5
Adjust for good Aircraft Editor, Debug, Sim Forces display.

elevator_up_limit = 40 ; 20 ; Elevator max deflection up angle (DEGREES)
elevator_down_limit = 28 ; 14 ; Elevator max deflection down angle (absolute value) (DEGREES)
The elevator effect is increased for better inverted flight behavior.

elevator_trim_neutral = 0 ; 2 ; Elevator trim max angle (absolute value) (DEGREES), for indicators only (no influence on flight model)
This is a green area in the non-cockpit elevator trim display.

cruise_lift_scalar = 1.0 ; 
parasite_drag_scalar = 1.63 ; 1
drag_coef_zero_lift = 0.03180
I control wings lift/drag via [AERODYNAMICS] and [FLIGHT_TUNING] parameters.

lift_coef_flaps = 0 ; 0.85970
lift_coef_spoilers = 0 ; -0.10000
drag_coef_flaps = 0.11 ; 0.11530
drag_coef_gear = 0.02 ; 0.01000
drag_coef_spoilers = 0 ; 0.10000
Airplane has flaps and rectractable gear, but no spoilers.

slats_level_1 = 0
flaps_level_1 = 0
slats_level_2 = 20 ; 0
flaps_level_2 = 20 ; 0
slats_level_3 = 40 ; 0
flaps_level_3 = 40 ; 0
; slats_level_full = 0
; flaps_level_full = 0
Fix flaps position display in non-cockpit view.

toe_brakes_scale = 0.7 ; 0.5
Increase "brake power" to hold airplane with brake at full thrust on ground.

fuel_flow_scalar = 0.7 ; 1
Set fuel consumption to 6h at 75%.

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