FFX 737-800: FS9 closes when weight changes.

[BGen_SirJohn]

Okay, I'm having a strange problem with the FFX 737-800.

I'm trying to change the weights to make it a bit more like the BBJ2, which is based on the same airframe and systems, but whenever I try to change the weights, FS9 closes as soon as I click on the OK button. It doesn't crash (there are no error messages), it just closes.

Ideally, I'd like to get my hands on a .cfg file for the thing that has the correct weight and balance for a BBJ (3 passengers, 2 flight crew, and a flight attendant, with baggage and provisions for trans-Atlantic flights), but just a fix for this problem would be greatly appreciated.

[wsieffert]

It may be that the aircraft is not set up for you to take advantage of changing the weights. Open the aircraft.cfg file for the aircraft and look at the &l;WEIGHT_AND_BALANCE&r; section, default B737-400 shown:

&l;WEIGHT_AND_BALANCE&r;
max_gross_weight = 150000 // (pounds)
empty_weight = 74170 // (pounds)

reference_datum_position = 0, 0, 0 // (feet) distance from FlightSim Reference position: (1/4 chord, centerline, waterline)
empty_weight_CG_position = -5, 0, 0 // (feet) longitudinal, lateral, vertical distance from specified datum

max_number_of_stations = 50

station_load.0 = "170.0, 41.0, -1.5, 0.0, Pilot" //Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.1 = "170.0, 41.0, 1.5, 0.0, Co-Pilot" //Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.2 = "510.0, 0.0, 0.0, 0.0, Crew" //Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.3 = "1360.0, 25.5, 0.0, 0.0, First Class" //Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.4 = "8160.0, 11.0, 0.0, 0.0, Coach 3-10" //Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.5 = "8160.0, -10.0, 0.0, 0.0, Coach 11-18" //Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.6 = "7140.0, -30.5, 0.0, 0.0, Coach 19-25" //Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.7 = "10000.0, 20.5, 0.0, 0.0, Forward Baggage" //Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)
station_load.8 = "4000.0, -27.5, 0.0, 0.0, Aft Baggage" //Weight (lbs), longitudinal, lateral, vertical positions from datum (feet)

;Moments of Inertia
empty_weight_pitch_MOI = 3172439
empty_weight_roll_MOI = 2262183
empty_weight_yaw_MOI = 3337024
empty_weight_coupled_MOI = 0

&l;fuel&r;
Center1 = 0, 0, 0, 2313, 0 //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
LeftMain = -3, -19, 0, 1500, 0 //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
RightMain = -3, 19, 0, 1500, 0 //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
fuel_type = 2 //Fuel type: 1 = Avgas, 2 = JetA
number_of_tank_selectors = 1
electric_pump=0

The important areas are that the empty weight added to all the station weights plus the fuel weight cannot be larger than the max gross weight.

If you load the default B737-400, you will see at the first instance the total weight is 149,420lbs depending on how fast you placed the simulator in pause. Therefore, the total weight is less than the max gross weight of 150,000lbs.

The other area of concern is the CG position. If you look at the CG position for the empty weight value, it is 5ft behind the datum point. Next notice that all the station loads list the weight and their respective CG positions referenced to the datum.

In many cases, the aircraft designer doesn't provide station loads but places the empty weight plus station loads under the empty weight value. In an aircraft that doesn't have station loads the CG position is placed in the CG empty weight area to provide the CG for empty weight plus station loads.

You option is to try and remove the station loads from the empty weight, then distribute the load throughout the aircraft. You will have to ensure the resultent final CG and the total station load is identical to the original aircraft.

If the aircraft is not setup for distributed loads and you make a change, it is probably making such a big change in either weight or CG that the program doesn't like the values and quits.

Jet Fuel wt = 1gal x 6.7lb
Weight x Arm = Moment (generally expressed in Lb, inches, Lb-in)

W. Sieffert