"""
Estimation of horizontal tail area
"""
# This file is part of FAST-OAD : A framework for rapid Overall Aircraft Design
# Copyright (C) 2021 ONERA & ISAE-SUPAERO
# FAST is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
import numpy as np
import openmdao.api as om
from scipy.constants import g
from fastoad.model_base import Atmosphere
[docs]class ComputeHTArea(om.ExplicitComponent):
"""
Computes area of horizontal tail plane
Area is computed to fulfill aircraft balance requirement at rotation speed
"""
[docs] def setup(self):
self.add_input("data:geometry:fuselage:length", val=np.nan, units="m")
self.add_input("data:geometry:wing:MAC:at25percent:x", val=np.nan, units="m")
self.add_input("data:geometry:wing:area", val=np.nan, units="m**2")
self.add_input("data:geometry:wing:MAC:length", val=np.nan, units="m")
self.add_input("data:geometry:has_T_tail", val=np.nan)
self.add_input("data:weight:airframe:landing_gear:main:CG:x", val=np.nan, units="m")
self.add_input("data:weight:airframe:landing_gear:front:CG:x", val=np.nan, units="m")
self.add_input("data:weight:aircraft:MTOW", val=np.nan, units="kg")
self.add_input("settings:weight:aircraft:CG:range", val=0.3)
self.add_input("settings:weight:airframe:landing_gear:front:weight_ratio", val=0.08)
self.add_input(
"settings:geometry:horizontal_tail:position_ratio_on_fuselage",
val=0.91,
desc="(does not apply for T-tails) distance to aircraft nose of 25% MAC of "
"horizontal tail divided by fuselage length",
)
self.add_output(
"data:geometry:horizontal_tail:MAC:at25percent:x:from_wingMAC25", units="m", ref=30.0
)
self.add_output("data:geometry:horizontal_tail:wetted_area", units="m**2", ref=100.0)
self.add_output("data:geometry:horizontal_tail:area", units="m**2", ref=50.0)
[docs] def setup_partials(self):
self.declare_partials("*", "*", method="fd")
self.declare_partials(
"data:geometry:horizontal_tail:MAC:at25percent:x:from_wingMAC25",
["data:geometry:fuselage:length", "data:geometry:wing:MAC:at25percent:x"],
method="fd",
)
[docs] def compute(self, inputs, outputs, discrete_inputs=None, discrete_outputs=None):
# Area of HTP is computed so its "lift" can counter the moment of weight
# on front landing gear w.r.t. main landing gear when the CG is in its
# most front position.
tail_type = np.round(inputs["data:geometry:has_T_tail"])
fuselage_length = inputs["data:geometry:fuselage:length"]
x_wing_aero_center = inputs["data:geometry:wing:MAC:at25percent:x"]
x_main_lg = inputs["data:weight:airframe:landing_gear:main:CG:x"]
x_front_lg = inputs["data:weight:airframe:landing_gear:front:CG:x"]
mtow = inputs["data:weight:aircraft:MTOW"]
wing_area = inputs["data:geometry:wing:area"]
wing_mac = inputs["data:geometry:wing:MAC:length"]
cg_range = inputs["settings:weight:aircraft:CG:range"]
front_lg_weight_ratio = inputs["settings:weight:airframe:landing_gear:front:weight_ratio"]
htp_aero_center_ratio = inputs[
"settings:geometry:horizontal_tail:position_ratio_on_fuselage"
]
delta_lg = x_main_lg - x_front_lg
atm = Atmosphere(0.0)
rho = atm.density
vspeed = atm.speed_of_sound * 0.2 # assume the corresponding Mach of VR is 0.2
# Proportion of weight on front landing gear is equal to distance between
# main landing gear and center of gravity, divided by distance between landing gears.
# If CG is in the most front position, the distance between main landing gear
# and center of gravity is:
distance_cg_to_mlg = front_lg_weight_ratio * delta_lg + wing_mac * cg_range
# So with this front CG, moment of (weight on front landing gear) w.r.t.
# main landing gear is:
m_front_lg = mtow * g * distance_cg_to_mlg
# Moment coefficient
pdyn = 0.5 * rho * vspeed ** 2
cm_front_lg = m_front_lg / (pdyn * wing_area * wing_mac)
# # CM of MTOW on main landing gear w.r.t 25% wing MAC
# lever_arm = front_lg_weight_ratio * delta_lg # lever arm wrt CoG
# lever_arm += wing_mac * cg_range # and now wrt 25% wing MAC
# cm_wheel = mtow * g * lever_arm / (pdyn * wing_area * wing_mac)
ht_volume_coeff = cm_front_lg
if tail_type == 1:
aero_centers_distance = fuselage_length - x_wing_aero_center
wet_area_coeff = 1.6
elif tail_type == 0:
aero_centers_distance = htp_aero_center_ratio * fuselage_length - x_wing_aero_center
wet_area_coeff = 2.0
else:
raise ValueError("Value of data:geometry:has_T_tail can only be 0 or 1")
htp_area = ht_volume_coeff / aero_centers_distance * wing_area * wing_mac
wet_area_htp = wet_area_coeff * htp_area
outputs[
"data:geometry:horizontal_tail:MAC:at25percent:x:from_wingMAC25"
] = aero_centers_distance
outputs["data:geometry:horizontal_tail:wetted_area"] = wet_area_htp
outputs["data:geometry:horizontal_tail:area"] = htp_area