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Flight Dynamics for the Ala Littoria S.73 I-ASTI
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I-ASTI was the fifth of nine S.73s delivered to Ala Littoria 1935-36. This production batch were all powered by imported Wright R-1820-52F Cyclone engines. No Italian engines of equivalent quality existed at that time. Earlier and later deliveries to Ala Littoria had different engines. Like the DC-3 the S.73 is a whole family of different aircraft with a singular ATC flight planning (search and rescue) identity.
These flight and engine dynamics replicate I-ASTI in particular.
[fltsim.0]
title=S73 I-ASTI ver. 2.0
sim=S-73
model=
panel=
sound=
texture=
kb_checklists=
kb_reference=Ala_littoria_S73_ref
atc_id=I-ASTI
ui_manufacturer=Savoia Marchetti
ui_type=S73
ui_variation=Ala Littoria with Wright Cyclone engines
atc_heavy=0
atc_airline=Ala Littoria
atc_flight_number=
description=By 1935 Ala Littoria was the main Italian airline and from November this 'flagship' version of the S.73, which required military grade fuel, flew the very demanding 'Linea Imperiale' linking Benghazi in Libya to Mogadishu in Somalia with a branch line service to Addis Abeba in Ethiopia. See History.txt for more detail.
[General]
atc_type=S73
atc_model=S73
performance=Press F10 and then lowest icon for step by step on screen handling notes. The S.73 of 1935 switched to a low wing allowing shorter, stronger gear legs and easier engine access. Highly optimised for use in Africa where very strong landing gear was essential the S.73 was the best trans African airliner of its day. However the S.73 relied on wide source (RDF/GPS) navigation infrastucture which required a crew of 5 despite having seats for a maximum of 18 passengers and only 8 with standard fuel. See History.txt for more detail.
[Views]
eyepoint = 6.35, -0.85, 3
[fuel]
The real aircraft had eight small fuel tanks in the wooden wing structure with minimal offset from CoG to minimise roll and yaw inertia which were already high for that timeframe.
Maximum fuel load was 5880lbs of high lead military grade 87 Octane fuel. Most of the maximum fuel load was required to operate the longest stages of the 'Linea Imperiale' from Mogadishu in Italian Somaliland to Benghazi in Libya. See History.txt for more detail.
The S.73 had 18 passenger seats, but it could not carry anything like 18 passengers over most stages of the Linea Imperiale. In practice the payload had to be restricted to just eight passengers plus bags on the most critical stages despite the need for a crew of five to operate the route using wide source navigation techniques. This allowed 4480lbs of AVGAS to be loaded.
LeftMain = 0, 0, 0, 287, 0
RightMain = 0, 0, 0, 287, 0
Center1 = 0, 0, 0, 172, 0
fuel_type = 1
number_of_tank_selectors = 2
electric_pump=1
[WEIGHT_AND_BALANCE]
When I-ASTI was delivered to Ala Littoria its 'empty' weight was roughly 15,870lbs, but this included almost 500lbs of lubricating oil for the three engines.
When I-ASTI was delivered to Ala Littoria max gross was no more than 10,430Kg which is about 22,950lbs. The S.73 may have been operated at overload weights by the Regia Aeronatica and/or the co-belligerant air force under war emergency powers later.
empty_weight = 15870 ;including oil, catering etc
max_gross_weight = 22950 ;with Cyclone engines
Due to the very strong landing gear it was safe to land the S.73 at the original max gross after an emergency return.
reference_datum_position = 0, 0, 0
empty_weight_CG_position = 0, 0, 0
station_load.0 = 1000, 0, 0, 0 ;5 crew with bags
station_load.1 = 1600, 0, 0, 0 ;8 pax with bags is max payload with 4480lbs of fuel.
15870 'empty' + 1000 crew + 1600 payload = 18470 with zero fuel
22950 - 18470 = max 4480lbs of AVGAS with 5 crew and 8 pax plus bags. This equates to about 746 USG of modern unleaded AVGAS. The calorific value of fuel depends on mass not volume. The correct *mass* must be encoded as a false volume in FS9.
Moments of Inertia
empty_weight_pitch_MOI = 120000
empty_weight_roll_MOI = 260000
empty_weight_yaw_MOI = 300000
empty_weight_coupled_MOI = 0.000
[GeneralEngineData]
engine_type = 0
Engine.0 = 4.2, -9.6, -2.3
Engine.1 = 12.2, 0, 0
Engine.2 = 4.2, 9.6, -2.3
fuel_flow_scalar = 1 ;Cyclone autolean more economical than Mistral
min_throttle_limit = 0.1
master_ignition_switch = 1
[piston_engine]
The Wright R-1820-F52 Cyclone was rated (with some rounding) as follows;
TOGA = 875hp at 39 inches MAP and 2200 rpm at sea level in ISA
Rated = 760hp at 36 inches below FL58 in ISA subject to temperature limits which were not difficult to avoid in the S.73 which had open cowls.
No emergency power. No feathering. No airscrew de-icing.
Use of TOGA power was only allowed if the tank selected for take off contained military grade high lead 87 octane AVGAS. Under all other circumstances take off was conducted using only Rated power. This is why there were 8 fuel tanks for 3 engines. Military grade AVGAS was only available to Ala Littoria in a vey few places along the Imperial route, which were both under Regia Aeronautica control, and easy to supply by ship. The military grade fuel was carefully safeguarded in its own tanks and never adulterated with airline grade 76 Octane in the other three tanks.
Once power was retarded from TOGA the flight engineer switched tanks to one containing only airline grade fuel. The tanks containing military grade fuel were used as little as possible to ensure that some would remain available for subsequent take offs and approaches at teh minor airstrips down the Imperial route. Tanks containing military grade fuel were selected when downwind to land so that go around power would be available on final if required. If it became necessary to top up a tank normally containing military grade fuel with airline grade fuel all subsequent take offs and go arounds had to be flown using only Rated power until the tanks were drained and refilled with military grade fuel at a major Italian military base.
cylinder_displacement=202.55
compression_ratio=6.45
number_of_cylinders=9
max_rated_rpm=2200
max_rated_hp=875 ;TOGA
critical_altitude=3900
fuel_metering_type=1
cooling_type=0
normalized_starter_torque=3
turbocharged=1
max_design_mp=39
min_design_mp=0
emergency_boost_type=0
emergency_boost_mp_offset=0.000000
emergency_boost_gain_offset=0.000000
fuel_air_auto_mixture=0
auto_ignition=0
max_rpm_mechanical_efficiency_scalar=1.000000
idle_rpm_mechanical_efficiency_scalar=1.000000
max_rpm_friction_scalar=1.000000
idle_rpm_friction_scalar=1.000000
[propeller]
I-ASTI had Savoia two pitch screws. MSFS cannot simulate variable pitch screws. It can only simulate constant speed or fixed pitch screws. If the aircraft is operated in accordance with the supplied handling notes performance in all stages of flight will approximate the real I-ASTI.
propeller_type=1
propeller_blades=3
gear_reduction_ratio=1.45
propeller_diameter=12.5
propeller_moi=10
beta_max=20
beta_min=20
fixed_pitch_beta=20
minimum_on_ground_beta=20
prop_sync_available=0
prop_deice_available=0
prop_feathering_available=0
prop_reverse_available=0
min_rpm_for_feather=0
beta_feather=0.0
power_absorbed_cf=0
minimum_reverse_beta=0
defeathering_accumulators_available=0
prop_auto_feathering_available=0
min_gov_rpm=650.000000
prop_tc=0.010000
low_speed_theory_limit=80.000000
[airplane_geometry]
oswald_efficiency_factor= 0.7
wing_area = 1001 ;93 square metres
wing_span = 78.7 ;24 metres
wing_root_chord = 16.9
wing_pos_apex_lon = 3.25
wing_pos_apex_vert = -2.500
htail_area = 175.000
htail_span = 20.000
htail_pos_lon = -36.000
htail_pos_vert = 0.000
htail_incidence = 0.000
htail_sweep = 40.000
vtail_area = 81.200
vtail_span = 10.000
vtail_sweep = 45.000
vtail_pos_lon = -36.000
vtail_pos_vert = 3.400
elevator_area = 75.000
aileron_area = 37.100
rudder_area = 37.000
elevator_up_limit = 18.000
elevator_down_limit = 15.000
aileron_up_limit = 18.000
aileron_down_limit = 18.000
rudder_limit = 25.000
elevator_trim_limit = 15.000
spoiler_limit = 0
spoilerons_available = 0
aileron_to_spoileron_gain = 0
min_ailerons_for_spoilerons = 0
min_flaps_for_spoilerons = 0
wing_dihedral = 0
wing_incidence = 0
wing_twist = 0
wing_winglets_flag = 0
wing_sweep = 0
[Flaps.0]
Slow moving and probably very fragile flaps. The Vfe ratings below may be generous and are estimated.
type= 1
span-outboard= 0.550
extending-time= 15
system_type= 0
flaps-position.0= 0,0
flaps-position.1= 12, 111 ;Vfe1 200 KmIAS
flaps-position.2= 24, 97 ;Vfe2 175 KMIAS
flaps-position.3= 38, 83 ;Vfe3 150 KmIAS
[Reference Speeds]
flaps_up_stall_speed = 57
full_flaps_stall_speed = 49
cruise_speed = 181
max_indicated_speed = 168 ;310 Km needs to warn Vno not Vne due to the unpatched weather module bugs within FS9 which are only corrected by a registered copy of FSUIPC.
In common with many vintage era airliners this version of the S.73 had enough power to rip its own tail off in level flight at low altitude if it encountered moderate turbulence. Some care must be excercised to moderate dynamic drag (IAS) < 310 KmIAS (but especially when descending) to avoid structural failure.
[Radios]
Com.1 = 1, 0
Com.2 = 0, 0
Nav.1 = 1, 0, 0 ;LBA receivers may have been fitted any time from the late 1930s onwards.
Nav.2 = 0, 0, 0
Adf.1 = 1 ;Probably no ADF until 9/43 but MFDF from delivery. Goniometer for use with MFDF
Adf.2 = 0
Transponder.1 = 1 ;IFF fitted post June 1940, else post 1943
Audio.1 = 1
Marker.1 = 1 ;These aircraft would have had audio fan marker receivers in Ala Littoria and military service whther or not they hadp MKR lights. MKR and Master Audio should be ON when flying a Lorenz Beam Approach.
[contact_points]
//GEAR
point.0 = 1, -40.67, 0, -2.9, 1200, 0, 1.01, 40, 0.3 , 2.5, 0.9 , 0, 0, 0, 0, 0
point.1 = 1, 1, -8.82, -10.8, 1600, 1, 1.98, 0, 0.4 , 2.5, 0.85, 0, 0, 2, 0, 0
point.2 = 1, 1, 8.82, -10.8, 1600, 2, 1.98, 0, 0.4 , 2.5, 0.85, 0, 0, 3, 0, 0
//SCRAPES
point.3= 2, -1.600, -39.000, 0.000, 800.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000,5.000, 0.000, 0.000
point.4= 2, -1.600, 39.000, 0.000, 800.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 6.000, 0.000, 0.000
point.5= 2, -44.100, 0.000, 0.81, 800.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 9.000, 0.000, 0.000
point.6= 2, 16.45, 0.000, -6.07, 800.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 4.000, 0.000, 0.000
point.7= 2, 7.64, -9.56, -8.25, 800.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 4.000, 0.000, 0.000
point.8= 2, 7.64, 9.56, -8.25, 800.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000, 4.000, 0.000, 0.000
static_pitch = 10
static_cg_height = 10.3
tailwheel_lock = 0
[brakes]
parking_brake = 1
toe_brakes_scale = 0.25 ;drum brakes at this date were ineffective and subject to fading
[hydraulic_system]
normal_pressure = 732.0 //PSI
electric_pumps = 0 //no electric pumps
engine_map = 1,1,0,0 //pumps on Eng1,2
[LIGHTS]
//Types: 1=beacon, 2=strobe, 3=navigation, 4=cockpit, 5=landing
light.0 = 3, -5.59, -39.13, 0.06, fx_navred
light.1 = 3, -5.59, 39.16, 0.1, fx_navgre
light.2 = 3, -44.06, 0, 0.87, fx_navwhi
light.3 = 4, 7.2, 0, 2.46, fx_vclight
light.4 = 4, 4.67, 1.5, 1.63, fx_vclight
light.5 = 5, 16.72, 0, -5.03, Newll
light.6 = 5, 5.36, -0.71, -4.29, fx_SM74_landing
light.7 = 5, 5.36, 0.71, -4.29, fx_SM74_landing
[keyboard_response]
elevator =200, 1000
aileron =200, 1000
rudder =200, 1000
[direction_indicators]
direction_indicator.0=1,0
direction_indicator.1=2,0
[attitude_indicators]
attitude_indicator.0 = 1
attitude_indicator.1 = 2
[turn_indicators]
turn_indicator.0=2,0
[autopilot]
autopilot_available= 1
direction_indicator=1
attitude_indicator =0
default_pitch_mode=0
max_bank=3 //HDG hold by rudder trim
max_bank_acceleration=1
max_bank_velocity=3
default_bank_mode=2
default_vertical_speed=0
autothrottle_available=0
pitch_takeoff_ga=8.000000
max_pitch=0
max_pitch_acceleration=0
max_pitch_velocity_lo_alt=0
max_pitch_velocity_hi_alt=0
max_pitch_velocity_lo_alt_breakpoint=0
max_pitch_velocity_hi_alt_breakpoint=0
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=0.000000
[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 ;unlikely in real life
[exits]
number_of_exits = 1
exit_rate.0 = 0.27 ;Percent per second
[EFFECTS]
wake=fx_wake
water=fx_spray
dirt=fx_tchdrt
concrete=fx_sparks
startup=fx_engstrt_jenny
touchdown=fx_tchdwn_s, 1
[electrical]
max_battery_voltage = 24
generator_alternator_voltage = 25
max_generator_alternator_amps = 100
[flight_tuning]
FS9 miscalculates these by default
p_factor_on_yaw = 0.01
torque_on_roll = 0.01
gyro_precession_on_yaw = 0.01
gyro_precession_on_pitch = 0.01
