Source code for RCAIDE.Library.Methods.Performance.estimate_take_off_weight_given_TOFL

# RCAIDE/Library/Methods/Performance/estimate_take_off_weight_given_TOFL.py

# Created: Apr 2025, M. Clarke  
# ----------------------------------------------------------------------
#   Imports
# ----------------------------------------------------------------------
import RCAIDE
from RCAIDE.Library.Methods.Performance.estimate_take_off_field_length import estimate_take_off_field_length
from RCAIDE.Library.Mission.Common.Pre_Process  import geometry_preprocess_routine  

import numpy as np

# ----------------------------------------------------------------------
#  Find Takeoff Weight Given TOFL
# ----------------------------------------------------------------------


def estimate_take_off_weight_given_TOFL(analyses=None,target_tofl=0.0,altitude = 0, delta_isa = 0):
    """
    Estimates the maximum allowable takeoff weight for a given takeoff field length requirement.

    Parameters
    ----------
    vehicle : Vehicle
        The vehicle instance containing:
            - mass_properties.operating_empty : float
                Operating empty weight [kg]
            - mass_properties.max_takeoff : float
                Maximum takeoff weight [kg]
    analyses : Analyses
        Container with atmosphere and aerodynamic analyses
    target_tofl : float or ndarray
        Target takeoff field length(s) [m]
    altitude : float, optional
        Airport altitude [m], default 0
    delta_isa : float, optional
        Temperature offset from ISA conditions [K], default 0

    Returns
    -------
    max_tow : ndarray
        Maximum allowable takeoff weight(s) for given field length(s) [kg]

    Notes
    -----
    Uses an interpolation approach by:
        1. Creating array of possible takeoff weights between OEW and 110% MTOW
        2. Computing TOFL for each weight
        3. Interpolating to find weight that gives target TOFL

    **Major Assumptions**
        * Linear interpolation between computed points is valid
        * Target TOFL is within achievable range
        * Meets assumptions from estimate_take_off_field_length

    **Theory**
    Takeoff field length varies approximately with W/T where:
        * W = aircraft weight
        * T = available thrust

    .. math::
        TOFL \propto \\frac{W}{T}

    See Also
    --------
    RCAIDE.Library.Methods.Performance.estimate_take_off_field_length
    """       
 
    if type(analyses) != RCAIDE.Framework.Analyses.Vehicle:
        raise AttributeError('RCAIDE analyses must be defined')
    
    if target_tofl ==0.0:
        raise AttributeError('Takeoff field length must be greater than zero')

    # ---------------------------------------------- 
    # Preprocess Geometry 
    # ---------------------------------------------- 
    geometry_preprocess_routine(analyses)
            
    #unpack
    vehicle   = analyses.vehicle
    tow_lower = vehicle.mass_properties.operating_empty
    tow_upper = 1.10 * vehicle.mass_properties.max_takeoff

    #saving initial reference takeoff weight
    tow_ref = vehicle.mass_properties.max_takeoff

    tow_vec = np.linspace(tow_lower,tow_upper,50)
    tofl    = np.zeros_like(tow_vec)

    for id,tow in enumerate(tow_vec):
        vehicle.mass_properties.takeoff = tow
        tofl[id], _ = estimate_take_off_field_length(analyses,altitude = 0, delta_isa = 0)

    target_tofl = np.atleast_1d(target_tofl)
    max_tow     = np.zeros_like(target_tofl)

    for id,toflid in enumerate(target_tofl):
        max_tow[id] = np.interp(toflid,tofl,tow_vec)

    #reset the initial takeoff weight
    vehicle.mass_properties.max_takeoff = tow_ref

    return max_tow