Airspeed conversions (true/calibrated/equivalent/Mach), atmospheric data, and more with built-in unit checking. Specific sub-modules include:
flightcondition: input altitude to compute common flight condition data.
Easily swap between true airspeed, calibrated airspeed, equivalent airspeed,
and Mach number. Includes atmospheric data.atmosphere: input altitude to compute atmospheric
data. Many relevant, derived quantities are included. The upper limit is
86 km for the
1993 International Standard Atmosphere model and
10,000 kilometers for the NRL MSIS model.units: built-in unit-checking and conversion using the
pint package.See the web application here: https://flightcondition.streamlit.app
Matthew C. Jones matt.c.jones.aoe@gmail.com
Install using the pip package-management system. The
easiest method is to open the terminal and run:
pip install flightcondition
Alternatively, manually download the source code, unpack, and run:
pip install <path/to/flightcondition>
Import all utilities with,
from flightcondition import *
or more explicitly as shown in the following examples.
The FlightCondition class is used to compute and interact with common flight
condition data. Inputs include altitude, velocity in some format, and an
optional length scale.
Input arguments include:
h (aliases include: alt, altitude)TAS (aliases include: tas, true_airspeed,
U_inf, V_inf)CAS (aliases include: cas,
calibrated_airspeed)EAS (aliases include: eas,
equivalent_airspeed)M (aliases include: mach, Mach, M_inf,
mach_number)L (aliases include: ell, bylen,
length, length_scale, l)Input quantities must be dimensionalized - see the usage below. Alternatively
use KTAS, KCAS, or KEAS for convenience. For example, KCAS=233
is equivalent to CAS=233*unit('knots').
The following tables list the quantities and the variables used to access them.
Quantities may be accessed by either (a) their abbreviated variable, e.g.
.TAS, or (b) by their full names, e.g. byname.true_airspeed. They
may also be accessed through their particular sub-category: byalt, byvel,
or bylen, e.g. .byvel.TAS or .byvel.byname.true_airspeed.
| Altitude Quantity | Variable | Full Name (via .byname.) |
|---|---|---|
| Geometric altitude | h | geometric_altitude |
| Geopotential altitude | H | geopotential_altitude |
| Pressure | p | pressure |
| Temperature | T | temperature |
| Density | rho | density |
| Sound speed | a | sounds_speed |
| Dynamic viscosity | mu | dynamic_viscosity |
| Kinematic viscosity | nu | kinematic_viscosity |
| Thermal conductivity | k | thermal_conductivity |
| Gravity | g | gravity |
| Mean free path | MFP | mean_free_path |
| Velocity Quantity | Name | Full Name (via .byname.) |
|---|---|---|
| True airspeed (TAS) | TAS | true_airspeed |
| Calibrated airspeed (CAS) | CAS | calibrated_airspeed |
| Equivalent airspeed (EAS) | EAS | equivalent_airspeed |
| Mach number | M | mach_number |
| Mach angle | mu_M | mach_angle |
| Dynamic pressure | q_inf | dynamic_pressure |
| Impact pressure | q_c | impact_pressure |
| Stagnation pressure | p0 | stagnation_pressure |
| Stagnation temperature | T0 | stagnation_temperature |
| Recovery temperature (laminar) | Tr_lamr | recovery_temperature_laminar |
| Recovery temperature (turbulent) | Tr_turb | recovery_temperature_turbulent |
| Reynolds number per unit length | Re_by_L | recovery_temperature_turbulent |
| Length-Scale Quantity | Name | Full Name (via .byname.) |
|---|---|---|
| Length scale | L | length_scale |
| Reynolds number | Re | reynolds_number |
| Boundary layer thickness (laminar) | h_BL_lamr | boundary_thickness_laminar |
| Boundary layer thickness (turbulent) | h_BL_turb | boundary_thickness_turbulent |
| Flat plate skin friction coefficient (laminar) | Cf_lamr | friction_coefficient_laminar |
| Flat plate skin friction coefficient (turbulent) | Cf_turb | friction_coefficient_turbulent |
from flightcondition import FlightCondition, unit
# Compute flight condition at 3 km, Mach 0.5
fc = FlightCondition(h=3*unit('km'), M=0.5)
# Uncomment to print summary of flight condition quantities:
#print(f"{fc}")
# Uncomment to print abbreviated output in US units:
#print(f"\n{fc.tostring(full_output=False, units="US")}")
# Convert true, calibrated, equivalent airspeeds
KTAS = fc.TAS.to('knots')
KCAS = fc.CAS.to('knots')
KEAS = fc.EAS.to('knots')
print(f"Flying at {KTAS.magnitude:.4g} KTAS,"
f" which is {KCAS.magnitude:.4g} KCAS,"
f" or {KEAS.magnitude:.4g} KEAS")
# >>> Flying at 319.4 KTAS, which is 277.7 KCAS, or 275.1 KEAS
# Access atmospheric data (see Atmosphere class for more)
h, p, T, rho, nu, a = fc.h, fc.p, fc.T, fc.rho, fc.nu, fc.a
print(f"The ambient temperature at {h.to('km'):.4g} is {T:.4g}")
# >>> The ambient temperature at 3 km is 268.7 K
# Change airspeed to 300 KEAS and altitude to 12 kft
fc.EAS = 300 * unit('knots')
fc.h = 12 * unit('kft')
#print(f"{fc}") # uncomment to print output
# Recompute for a range of altitudes at 275.14 knots-equivalent
# airspeed with a characteristic length scale of 10 meters
fc = FlightCondition(h=[0, 9.8425, 20]*unit('kft'),
EAS=275.14*unit('kt'),
L=10*unit('m'))
# Compute additional derived quantities - explore the class for more!
print(f"\nThe dynamic pressure in psi is {fc.q_inf.to('psi'):.3g}")
# >>> The dynamic pressure in psi is [1.78 1.78 1.78] psi
print(f"The Reynolds number is {fc.Re:.3g}")
# >>> The Reynolds number is [9.69e+07 8.82e+07 7.95e+07]
h_yplus100 = fc.wall_distance_from_yplus(100)
print(f"The wall distance where y+=100 is {h_yplus100.to('in'):.3g}")
# >>> The wall distance where y+=100 is [0.0126 0.0138 0.0153] in
# Alternatively access quantities by their full name
print(fc.TAS == fc.byname.true_airspeed)
# >>> [ True True True]
# Or by their sub-categories: `byalt`, `byvel`, or `bylen`
print(fc.byvel.TAS == fc.byvel.byname.true_airspeed)
# >>> [ True True True]
The Atmosphere class can be used to compute and interact with common standard
atmosphere data and derived quantities. See the list of output quantities in
the FlightCondition documentation above.
See also layer for layer properties such as layer.name for the layer name.
Note that all Atmosphere properties can be accessed through the
FlightCondition class, however, this class stands on its own if the
additional velocity and length-scale quantities are not desired.
The input argument is geometric altitude h. Aliases include alt and
altitude. Note that these geometric altitude must be input as dimensional
length quantities - see the usage below. Alternatively input
un-dimensionalized numbers using h_kft or h_km for kilofeet and kilometers
respectively.
from flightcondition import Atmosphere, unit
# Compute atmospheric data for a scalar or array of altitudes
h = [0.0, 44.2, 81.0] * unit('km')
atm = Atmosphere(h)
# Uncomment to print all atmospheric quantities:
#print(f"\n{atm}")
# Uncomment to print while specifying abbreviated output in US units:
#print(f"\n{atm.tostring(full_output=False, units="US")}")
# See also the linspace() function from numpy, e.g.
# h = linspace(0, 81.0, 82) * unit('km')
# Access individual properties and convert to desired units: "
p, T, rho, nu, a, k = atm.p, atm.T, atm.rho, atm.nu, atm.a, atm.k
print(f"\nThe pressure in psi is {p.to('psi'):.3g}")
# >>> The pressure in psi is [14.7 0.024 0.000129] psi
# Compute additional properties such as mean free path
# Explore the class data structure for all options
print( f"\nThe mean free path = {atm.MFP:.3g}")
# >>> The mean free path = [7.25e-08 4.04e-05 0.00564] yd
Conveniently input, output, and convert units using pint units.
from flightcondition import unit, printv
h = 33 * unit('km')
print(h.to('kft'))
# >>> 108.26771653543307 kft
printv(h, to='kft')
# >>> h = 108.27 kft
U_inf = 20 * unit('knots')
rho_inf = 1.225 * unit('kg/m^3')
q_inf = 0.5*rho_inf*U_inf**2
printv(q_inf, to='psi')
# >>> q_inf = 0.0094042 psi
Note that pint does not support conflicting unit
registries so avoid interactions between flightcondition.unit and a separate
pint.UnitRegistry.
A command line interface (CLI) is included for convenience but with limited
functionality. Run flightcondition -h for help.
An example call is given for the flight condition of 233 knots-equivalent-airspeed at 23 kilofeet with a length scale of 4 feet and abbreviated output:
flightcondition --h 23 kft --EAS 233 knots --L 4 ft --no-full-output
===========================================================
Flight Condition (units=US, full_output=False)
===========================================================
------------------ Altitude Quantities ------------------
geometric_altitude h = 23 kft
pressure p = 857.25 lbf/ft²
temperature T = 436.74 °R
density rho = 1.1435×10⁻³ slug/ft³
sound_speed a = 1024.5 ft/s
kinematic_viscosity nu = 2.8509×10⁻⁴ ft²/s
------------------ Velocity Quantities ------------------
mach_number M = 0.55344
true_airspeed TAS = 335.93 kt
calibrated_airspeed CAS = 238.14 kt
equivalent_airspeed EAS = 233 kt
reynolds_per_length Re_by_L = 1.6573×10⁵ 1/in
------------------ Length Quantities ------------------
length_scale L = 4 ft
reynolds_number Re = 7.9551×10⁶
Alternatively use the --KEAS 233 syntactic sugar to omit the knots unit.
See also --KTAS and --KCAS.
See the web application here: https://flightcondition.streamlit.app
model=standard, Atmospheric quantities follow the
1993 International Standard Atmosphere model.model=msis, atmospheric quantities follow the NRL MSIS model.
Note that model=msis is automatically enabled for altitudes higher than
80 kilometers.CAS, q_c, p_0)flightcondition is maintained using unit tests to maintain functionality and
accuracy. Even so, see the Disclaimer below.
flightcondition is licensed under the MIT LICENSE. See the
LICENSE
document.
The software is provided "as is", without warranty of any kind, express or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose and noninfringement. In no event shall the authors or copyright holders be liable for any claim, damages or other liability, whether in an action of contract, tort or otherwise, arising from, out of or in connection with the software or the use or other dealings in the software.
FAQs
Airspeed conversions (true/calibrated/equivalent/Mach),
We found that flightcondition demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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