# RCAIDE/Library/Plots/Performance/plot_V_n_diagram.py
#
#
# Created: Feb 2026, M. Clarke
# ----------------------------------------------------------------------------------------------------------------------
# IMPORT
# ----------------------------------------------------------------------------------------------------------------------
# RCAIDE imports
from RCAIDE.Framework.Core import Units
from RCAIDE.Library.Plots.Common import set_axes, plot_style
# Pacakge imports
from matplotlib import pyplot as plt
# ----------------------------------------------------------------------------------------------------------------------
# PLOTS
# ----------------------------------------------------------------------------------------------------------------------
[docs]
def plot_V_n_diagram(V_n_data,
vehicle = None,
save_figure = False,
show_legend = True,
save_filename = "V_n_Diagram",
file_type =".png",
generate_report = False,
width = 8,
height = 6):
""" Plot graph, save the final figure, and create results output file
Source:
Inputs:
V_n_data.
airspeeds.positive [kts]
airspeeds.negative [kts]
Vc [kts]
Vd [kts]
Vs1.positive [kts]
negative [kts]
Va.positive [kts]
negative [kts]
load_factors.positive [Unitless]
negative [Unitless]
gust_load_factors.positive [Unitless]
negative [Unitless]
weight [lb]
altitude [ft]
vehicle._base.tag [Unitless]
Uref_rough [ft/s]
Uref_cruise [ft/s]
Uref_dive [ft/s]
Outputs:
Properties Used:
N/A
Description:
"""
# Unpack
load_factors_pos = V_n_data.load_factors.positive
load_factors_neg = V_n_data.load_factors.negative
airspeeds_pos = V_n_data.airspeeds.positive
airspeeds_neg = V_n_data.airspeeds.negative
Vc = V_n_data.Vc
Vd = V_n_data.Vd
Vs1_pos = V_n_data.Vs1.positive
Vs1_neg = V_n_data.Vs1.negative
Va_pos = V_n_data.Va.positive
Va_neg = V_n_data.Va.negative
gust_load_factors_pos = V_n_data.gust_load_factors.positive
gust_load_factors_neg = V_n_data.gust_load_factors.negative
weight = V_n_data.weight
altitude = V_n_data.altitude
Uref_rough = V_n_data.gust_data.airspeeds.rough_gust
Uref_cruise = V_n_data.gust_data.airspeeds.cruise_gust
Uref_dive = V_n_data.gust_data.airspeeds.dive_gust
category_tag = V_n_data.category_tag
#-----------------------------
# Plotting the V-n diagram
#-----------------------------
# get plotting style
ps = plot_style()
parameters = {'axes.labelsize': ps.axis_font_size,
'xtick.labelsize': ps.axis_font_size,
'ytick.labelsize': ps.axis_font_size,
'axes.titlesize': ps.title_font_size}
plt.rcParams.update(parameters)
fig = plt.figure(save_filename)
fig.set_size_inches(width,height)
ax = fig.add_subplot(1,1,1)
ax.fill(airspeeds_pos, load_factors_pos, c='b', alpha=0.3)
ax.fill(airspeeds_neg, load_factors_neg, c='b', alpha=0.3)
ax.plot(airspeeds_pos, load_factors_pos, c='b')
ax.plot(airspeeds_neg, load_factors_neg, c='b')
# Plotting gust lines
ax.plot([0, Vc,1.05*Vd],[1,gust_load_factors_pos[2],gust_load_factors_pos[len(gust_load_factors_pos)-3]],'--', c='r', label = ('Gust ' + str(round(Uref_cruise)) + 'fps'))
ax.plot([0, Vd,1.05*Vd],[1,gust_load_factors_pos[3],gust_load_factors_pos[len(gust_load_factors_pos)-2]],'--', c='g', label = ('Gust ' + str(round(Uref_dive)) + 'fps'))
ax.plot([0, Vc,1.05*Vd],[1,gust_load_factors_neg[2],gust_load_factors_neg[len(gust_load_factors_neg)-3]],'--', c='r')
ax.plot([0, Vd,1.05*Vd],[1,gust_load_factors_neg[3],gust_load_factors_neg[len(gust_load_factors_neg)-2]],'--', c='g')
if category_tag == 'commuter':
ax.plot([0, 1.05*Vd],[1,gust_load_factors_pos[len(gust_load_factors_pos)-1]],'--', c='m', label = ('Gust ' + str(round(Uref_rough)) + 'fps'))
ax.plot([0, 1.05*Vd],[1,gust_load_factors_neg[len(gust_load_factors_neg)-1]],'--', c='m')
# Formating the plot
ax.set_xlabel('Airspeed, KEAS')
ax.set_ylabel('Load Factor')
ax.legend()
ax.grid()
#---------------------------------
# Creating results output file
#---------------------------------
if generate_report:
fres = open("V_n_diagram_results_" + V_n_data.tag +".dat","w")
fres.write('V-n diagram summary\n')
fres.write('-------------------\n')
fres.write('Aircraft: ' + V_n_data.tag + '\n')
fres.write('category: ' + V_n_data.category + '\n')
fres.write('FAR certification: Part ' + V_n_data.FAR_part_number + '\n')
fres.write('Weight = ' + str(round(weight)) + ' lb\n')
fres.write('Altitude = ' + str(round(altitude)) + ' ft\n')
fres.write('---------------------------------------------------------------\n\n')
fres.write('Airspeeds: \n')
fres.write(' Positive stall speed (Vs1) = ' + str(round(Vs1_pos,1)) + ' KEAS\n')
fres.write(' Negative stall speed (Vs1) = ' + str(round(Vs1_neg,1)) + ' KEAS\n')
fres.write(' Positive maneuver speed (Va) = ' + str(round(Va_pos,1)) + ' KEAS\n')
fres.write(' Negative maneuver speed (Va) = ' + str(round(Va_neg,1)) + ' KEAS\n')
fres.write(' Cruise speed (Vc) = ' + str(round(Vc,1)) + ' KEAS\n')
fres.write(' Dive speed (Vd) = ' + str(round(Vd,1)) + ' KEAS\n')
fres.write('Load factors: \n')
fres.write(' Positive limit load factor (n+) = ' + str(round(max(load_factors_pos),2)) + '\n')
fres.write(' Negative limit load factor (n-) = ' + str(round(min(load_factors_neg),2)) + '\n')
fres.write(' Positive load factor at Vd = ' + str(round(V_n_data.limit_loads.dive.positive,2)) + '\n')
fres.write(' Negative load factor at Vd = ' + str(round(V_n_data.limit_loads.dive.negative,2)) + '\n')
# Adjusting the sub-plots for legend
fig.tight_layout()
if save_figure:
fig.savefig(save_filename + file_type)
return fig
