weights_BWB.py

@File : weights_BWB.py @Date : 2023/03/20 @Author : Eytan Adler @Description : BWB weight estimation methods

class openconcept.weights.weights_BWB.BWBEmptyWeight(**kwargs)

Bases: Group

Estimate the empty weight of a BWB.

Inputs:

ac|num_passengers_max (float) – Maximum number of passengers (scalar, dimensionless)
ac|num_flight_deck_crew (float) – Number of flight crew members (scalar, dimensionless)
ac|num_cabin_crew (float) – Number of flight attendants (scalar, dimensionless)
ac|cabin_pressure (float) – Cabin pressure (scalar, psi)
ac|aero|Mach_max (float) – Maximum aircraft Mach number (scalar, dimensionless)
ac|aero|Vstall_land (float) – Landing stall speed (scalar, knots)
ac|geom|centerbody|S_cabin (float) – Planform area of the pressurized centerbody cabin area (scalar, sq ft)
ac|geom|centerbody|S_aftbody (float) – Planform area of the centerbody aft of the cabin (scalar, sq ft)
ac|geom|centerbody|taper_aftbody (float) – Taper ratio of the ceterbody region aft of the cabin (scalar, dimensionless)
ac|geom|wing|S_ref (float) – Outboard wing planform reference area (scalar, sq ft)
ac|geom|wing|AR (float) – Outboard wing aspect ratio (scalar, dimensionless)
ac|geom|wing|c4sweep (float) – Outboard wing sweep at 25% mean aerodynamic chord (scalar, radians)
ac|geom|wing|taper (float) – Outboard wing taper ratio (scalar, dimensionless)
ac|geom|wing|toverc (float) – Outboard wing root thickness-to-chord ratio (scalar, dimensionless)
ac|geom|maingear|length (float) – Length of the main landing gear (scalar, inch)
ac|geom|maingear|num_wheels (float) – Total number of main landing gear wheels (scalar, dimensionless)
ac|geom|maingear|num_shock_struts (float) – Total number of main landing gear shock struts (scalar, dimensionless)
ac|geom|nosegear|length (float) – Length of the nose landing gear (scalar, inch)
ac|geom|nosegear|num_wheels (float) – Total number of nose landing gear wheels (scalar, dimensionless)
ac|geom|V_pressurized (float) – Volume of the pressurized cabin (scalar, cubic ft)
ac|propulsion|engine|rating (float) – Rated thrust of each engine (scalar, lbf)
ac|propulsion|num_engines (float) – Number of engines (scalar, dimensionless)
ac|weights|MTOW (float) – Maximum takeoff weight (scalar, lb)
ac|weights|MLW (float) – Maximum landing weight (scalar, lb)
ac|weights|W_fuel_max (float) – Maximum fuel weight (scalar, lb)

Outputs:

OEW (float) – Total operating empty weight (scalar, lb)
W_cabin (float) – Weight of the pressurized cabin region of the BWB without structural fudge factor multiplier (scalar, lb)
W_aftbody (float) – Weight of the centerbody region aft of the pressurized cabin without structural fudge factor multiplier (scalar, lb)
W_wing (float) – Estimated outboard wing weight without structural fudge factor multiplier (scalar, lb)
W_mlg (float) – Main landing gear weight without structural fudge factor multiplier (scalar, lb)
W_nlg (float) – Nose landing gear weight without structural fudge factor multiplier (scalar, lb)
W_nacelle (float) – Weight of the nacelles (scalar, lb)
W_structure (float) – Total structural weight = fudge factor * (W_cabin + W_aftbody + W_wing + W_mlg + W_nlg + W_nacelle) (scalar, lb)
W_engines (float) – Total dry engine weight (scalar, lb)
W_thrust_rev (float) – Total thrust reverser weight (scalar, lb)
W_eng_control (float) – Total engine control weight (scalar, lb)
W_fuelsystem (float) – Total fuel system weight including tanks and plumbing (scalar, lb)
W_eng_start (float) – Total engine starter weight (scalar, lb)
W_furnishings (float) – Weight estimate of seats, galleys, lavatories, and other furnishings (scalar, lb)
W_flight_controls (float) – Flight control system weight (scalar, lb)
W_avionics (float) – Intrumentation, avionics, and electronics weight (scalar, lb)
W_electrical (float) – Electrical system weight (scalar, lb)
W_ac_pressurize_antiice (float) – Air conditioning, pressurization, and anti-icing system weight (scalar, lb)
W_oxygen (float) – Oxygen system weight (scalar, lb)
W_APU (float) – Auxiliary power unit weight (scalar, lb)

Options:

structural_fudge (float) – Multiplier on the structural weight to allow the user to account for miscellaneous items and advanced materials. Structural weight includes wing, horizontal stabilizer, vertical stabilizer, fuselage, landing gear, and nacelle weights. By default 1.0 (scalar, dimensionless)
total_fudge (float) – Multiplier on the final operating empty weight estimate. Structural components have both the structural fudge and total fudge factors applied. By default 1.0 (scalar, dimensionless)
wing_weight_multiplier (float) – Multiplier on wing weight. This can be used as a very rough way of increasing wing weight due to lack of inertial load relief from the fuel. By default 1.0 (scalar, dimensionless)
n_ult (float) – Ultimate load factor, 1.5 x limit load factor, by default 1.5 x 2.5 (scalar, dimensionless)
n_land_ult (float) – Ultimate landing load factor, which is 1.5 times the gear load factor (defined in equation 11.11). Table 11.5 gives reasonable gear load factor values for different aircraft types, with commercial aircraft in the 2.7-3 range. Default is taken at 2.8, thus the ultimate landing load factor is 2.8 x 1.5 (scalar, dimensionless)
control_surface_area_frac (float) – Fraction of the total wing area covered by control surfaces and flaps, by default 0.1 (scalar, dimensionless)
kneeling_main_gear_parameter (float) – Set to 1.126 for kneeling main gear and 1 otherwise, by default 1 (scalar, dimensionless)
kneeling_nose_gear_parameter (float) – Set to 1.15 for kneeling nose gear and 1 otherwise, by default 1 (scalar, dimensionless)
K_lav (float) – Lavatory coefficient; 0.31 for short ranges and 1.11 for long ranges, by default 0.7
K_buf (float) – Food provisions coefficient; 1.02 for short range and 5.68 for very long range, by default 4
coeff_fc (float) – K_fc in Roskam times any additional coefficient. The book says take K_fc as 0.44 for un-powered flight controls and 0.64 for powered flight controls. Multiply this coefficient by 1.2 if leading edge devices are employed. If lift dumpers are employed, use a factor of 1.15. By default 1.2 * 0.64.
coeff_avionics (float) – Roskam notes that the avionics weight estimates are probably conservative for modern computer-based flight management and navigation systems. This coefficient is multiplied by the Roskam estimate to account for this. By default 0.5.
APU_weight_frac (float) – Auxiliary power unit weight divided by maximum takeoff weight, by deafult 0.0085.

class openconcept.weights.weights_BWB.CabinWeight_BWB(**kwargs)

Bases: ExplicitComponent

Compute the weight of the pressurized cabin portion of a BWB centerbody. Estimate is based on a curve fit of FEA models. Details described in “A Sizing Methodology for the Conceptual Design of Blended-Wing-Body Transports” by Kevin R. Bradley.

Inputs:

ac|geom|centerbody|S_cabin (float) – Planform area of the pressurized centerbody cabin area (scalar, sq ft)
ac|weights|MTOW (float) – Maximum takeoff weight (scalar, lb)

Outputs:

W_cabin (float) – Weight of the pressurized cabin region of the BWB (scalar, lb)

class openconcept.weights.weights_BWB.AftbodyWeight_BWB(**kwargs)

Bases: ExplicitComponent

Compute the weight of the portion of the centerbody aft of the pressurized region (behind the rear spar). Estimate is based on a curve fit of FEA models. Details described in “A Sizing Methodology for the Conceptual Design of Blended-Wing-Body Transports” by Kevin R. Bradley.

Inputs:

ac|geom|centerbody|S_aftbody (float) – Planform area of the centerbody aft of the cabin (scalar, sq ft)
ac|geom|centerbody|taper_aftbody (float) – Taper ratio of the ceterbody region aft of the cabin (scalar, dimensionless)
ac|propulsion|num_engines (float) – Number of engines (scalar, dimensionless)
ac|weights|MTOW (float) – Maximum takeoff weight (scalar, lb)

Outputs:

W_aftbody (float) – Weight of the centerbody region aft of the pressurized cabin (scalar, lb)