def blade_angle(
prop,
bhp,
rpm,
tas,
altitude,
temp="std",
power_units="hp",
alt_units="ft",
temp_units="C",
speed_units="kt",
dia_units="in",
):
"""
Returns propeller blade angle.
"""
press_ratio = SA.alt2press_ratio(altitude, alt_units=alt_units)
if temp == "std":
temp = SA.alt2temp(altitude, temp_units=temp_units, alt_units=alt_units)
temp_ratio = U.temp_conv(temp, from_units=temp_units, to_units="K") / 288.15
density_ratio = press_ratio / temp_ratio
density = density_ratio * SA.Rho0
Cp = bhp2Cp(bhp, rpm, density, prop.dia, power_units=power_units, density_units="kg/m**3", dia_units=dia_units)
J = advance_ratio(tas, rpm, prop.dia, speed_units=speed_units, dia_units=dia_units)
blade_tip_mach = tip_mach(
tas, rpm, temp, prop.dia, speed_units=speed_units, temp_units=temp_units, dia_units=dia_units
)
blade_angle = cp2blade_angle(prop, Cp, J, blade_tip_mach)
return blade_angle
def blade_angle2bhp(
prop,
blade_angle,
rpm,
tas,
altitude,
temp="std",
power_units="hp",
alt_units="ft",
temp_units="C",
speed_units="kt",
dia_units="in",
):
"""
Returns returns engine power, given blade angle, rpm and flight conditions.
"""
press_ratio = SA.alt2press_ratio(altitude, alt_units=alt_units)
if temp == "std":
temp = SA.alt2temp(altitude, temp_units=temp_units, alt_units=alt_units)
temp_ratio = U.temp_conv(temp, from_units=temp_units, to_units="K") / 288.15
density_ratio = press_ratio / temp_ratio
density = density_ratio * SA.Rho0
# Cp = bhp2Cp(bhp, rpm, density, prop.dia, power_units = power_units, density_units = 'kg/m**3', dia_units = dia_units)
J = advance_ratio(tas, rpm, prop.dia, speed_units=speed_units, dia_units=dia_units)
blade_tip_mach = tip_mach(
tas, rpm, temp, prop.dia, speed_units=speed_units, temp_units=temp_units, dia_units=dia_units
)
Cp = blade_angle2cp(prop, blade_angle, J, blade_tip_mach)
bhp = cp2bhp(Cp, rpm, density, prop.dia, power_units=power_units, density_units="kg/m**3", dia_units=dia_units)
return bhp
def temp2speed_of_sound(temp,
temp_units=default_temp_units,
speed_units=default_speed_units):
"""
Return the speed of sound, given the air temperature.
The temperature units may be deg C, F, K or R ('C', 'F', 'K' or 'R').
The speed units may be 'kt', 'mph', 'km/h', 'm/s' and 'ft/s'.
If the units are not specified, the units in default_units.py are used.
Examples:
Determine speed of sound in knots at 15 deg (default temperature units):
>>> temp2speed_of_sound(15)
661.47882487301808
Determine speed of sound in mph at 120 deg F:
>>> temp2speed_of_sound(120, speed_units = 'mph', temp_units = 'F')
804.73500154991291
"""
# function tested in tests/test_std_atm.py
temp = U.temp_conv(temp, from_units=temp_units, to_units='K')
speed_of_sound = M.sqrt((1.4 * Rd) * temp)
speed_of_sound = U.speed_conv(speed_of_sound,
from_units='m/s',
to_units=speed_units)
return speed_of_sound
def alt2temp(H, alt_units=default_alt_units,
temp_units=default_temp_units):
"""Return the standard temperature for the specified altitude. Altitude
units may be feet ('ft'), metres ('m'), statute miles, ('sm') or
nautical miles ('nm'). Temperature units may be degrees C, F, K or R
('C', 'F', 'K' or 'R')
If the units are not specified, the units in default_units.py are used.
Examples:
Calculate the standard temperature (in default temperature units) at
5,000 (default altitude units):
>>> alt2temp(5000)
5.0939999999999941
Calculate the standard temperature in deg F at sea level:
>>> alt2temp(0, temp_units = 'F')
59.0
Calculate the standard temperature in deg K at 11,000 m:
>>> alt2temp(11000, alt_units = 'm', temp_units = 'K')
216.64999999999998
Calculate the standard temperature at 11 statute miles in deg R:
>>> alt2temp(11, alt_units = 'sm', temp_units = 'R')
389.96999999999997
The input value may be an expression:
>>> alt2temp(11 * 5280, temp_units = 'R')
389.96999999999997
"""
# Validated to 84000 m
# uses meters and degrees K for the internal calculations
# function tested in tests/test_std_atm.py
H = U.len_conv(H, from_units=alt_units, to_units='km')
if H <= 11:
temp = T0 + H * L0
elif H <= 20:
temp = T11
elif H <= 32:
temp = T20 + (H - 20) * L20
elif H <= 47:
temp = T32 + (H - 32) * L32
elif H <= 51:
temp = T47
elif H <= 71:
temp = T51 + (H - 51) * L51
elif H <= 84.852:
temp = T71 + (H - 71) * L71
else:
raise ValueError, \
'This function is only implemented for altitudes of 84.852 km and below.'
return U.temp_conv(temp, to_units=temp_units, from_units='K')
def temp2speed_of_sound(temp, temp_units=default_temp_units,
speed_units=default_speed_units):
"""
Return the speed of sound, given the air temperature.
The temperature units may be deg C, F, K or R ('C', 'F', 'K' or 'R').
The speed units may be 'kt', 'mph', 'km/h', 'm/s' and 'ft/s'.
If the units are not specified, the units in default_units.py are used.
Examples:
Determine speed of sound in knots at 15 deg (default temperature units):
>>> temp2speed_of_sound(15)
661.47882487301808
Determine speed of sound in mph at 120 deg F:
>>> temp2speed_of_sound(120, speed_units = 'mph', temp_units = 'F')
804.73500154991291
"""
# function tested in tests/test_std_atm.py
temp = U.temp_conv(temp, from_units=temp_units, to_units='K')
speed_of_sound = M.sqrt((1.4 * Rd) * temp)
speed_of_sound = U.speed_conv(speed_of_sound, from_units='m/s',
to_units=speed_units)
return speed_of_sound
def alt2temp(H, alt_units=default_alt_units, temp_units=default_temp_units):
"""Return the standard temperature for the specified altitude. Altitude
units may be feet ('ft'), metres ('m'), statute miles, ('sm') or
nautical miles ('nm'). Temperature units may be degrees C, F, K or R
('C', 'F', 'K' or 'R')
If the units are not specified, the units in default_units.py are used.
Examples:
Calculate the standard temperature (in default temperature units) at
5,000 (default altitude units):
>>> alt2temp(5000)
5.0939999999999941
Calculate the standard temperature in deg F at sea level:
>>> alt2temp(0, temp_units = 'F')
59.0
Calculate the standard temperature in deg K at 11,000 m:
>>> alt2temp(11000, alt_units = 'm', temp_units = 'K')
216.64999999999998
Calculate the standard temperature at 11 statute miles in deg R:
>>> alt2temp(11, alt_units = 'sm', temp_units = 'R')
389.96999999999997
The input value may be an expression:
>>> alt2temp(11 * 5280, temp_units = 'R')
389.96999999999997
"""
# Validated to 84000 m
# uses meters and degrees K for the internal calculations
# function tested in tests/test_std_atm.py
H = U.len_conv(H, from_units=alt_units, to_units='km')
if H <= 11:
temp = T0 + H * L0
elif H <= 20:
temp = T11
elif H <= 32:
temp = T20 + (H - 20) * L20
elif H <= 47:
temp = T32 + (H - 32) * L32
elif H <= 51:
temp = T47
elif H <= 71:
temp = T51 + (H - 51) * L51
elif H <= 84.852:
temp = T71 + (H - 71) * L71
else:
print(
'This function is only implemented for altitudes of 84.852 km and below.'
)
return U.temp_conv(temp, to_units=temp_units, from_units='K')
def temp2temp_ratio(temp, temp_units=default_temp_units):
"""
Return the temperature ratio
"""
theta = U.temp_conv(temp, from_units = temp_units, to_units='K') / T0
return theta
def temp2temp_ratio(temp, temp_units=default_temp_units):
"""
Return the temperature ratio
"""
theta = U.temp_conv(temp, from_units=temp_units, to_units='K') / T0
return theta
def prop_eff(
prop,
bhp,
rpm,
tas,
altitude,
temp="std",
power_units="hp",
alt_units="ft",
temp_units="C",
speed_units="kt",
dia_units="in",
):
"""
Returns propeller efficiency based on engine power provided to the propeller.
"""
press_ratio = SA.alt2press_ratio(altitude, alt_units=alt_units)
if temp == "std":
temp = SA.alt2temp(altitude, temp_units=temp_units, alt_units=alt_units)
temp_ratio = U.temp_conv(temp, from_units=temp_units, to_units="K") / 288.15
density_ratio = press_ratio / temp_ratio
density = density_ratio * SA.Rho0
Cp = bhp2Cp(bhp, rpm, density, prop.dia, power_units=power_units, density_units="kg/m**3", dia_units=dia_units)
J = advance_ratio(tas, rpm, prop.dia, speed_units=speed_units, dia_units=dia_units)
blade_tip_mach = tip_mach(
tas, rpm, temp, prop.dia, speed_units=speed_units, temp_units=temp_units, dia_units=dia_units
)
prop_eff = cp2eff(prop, Cp, J, blade_tip_mach)
if N.isnan(prop_eff):
raise ValueError, "Out of range inputs"
return prop_eff
def alt2kinematic_viscosity(H, T='std', alt_units=default_alt_units, temp_units=default_temp_units, kinematic_viscosity_units=default_kinematic_viscosity_units):
"""
Return kinematic viscosity, given altitude and an optional temperature input.
"""
density = alt2density(H, alt_units, density_units='kg/m**3')
isa_temp = alt2temp(H, alt_units, 'K')
if T != 'std':
isa_temp = alt2temp(H, alt_units, 'K')
T = U.temp_conv(T, temp_units, 'K')
density *= isa_temp / T
else:
T = U.temp_conv(isa_temp, 'K', temp_units)
u = temp2dynamic_viscosity(T, temp_units, 'Pa s')
v = u / density
v = U.kinematic_viscosity_conv(v, 'm**2/s', kinematic_viscosity_units)
return v
def pwr(rpm, MP, altitude, temp = 'std', alt_units = 'ft', temp_units = 'C'):
"""
Returns horsepower for Lycoming O-360-A series engines, given:
rpm - engine speed in revolutions per minute
MP - manifold pressure (" HG)
altitude - pressure altitude
temp - ambient temperature (optional - std temperature is used if no
temperature is input).
alt_units - (optional) - units for altitude, ft, m, or km
(default is ft)
temp_units - (optional) - units for temperature, C, F, K or R
(default is deg C)
The function replicates Lycoming curve ??????? and is valid at mixture
for maximum power.
Examples:
Determine power at 2620 rpm, 28 inches HG manifold pressure, 0 ft,
and -10 deg C:
>>> pwr(2620, 28, 0, -10)
183.91485642478889
Determine power at 2500 rpm, 25" MP, 5000 ft and 0 deg F:
>>> pwr(2500, 25, 5000, 0, temp_units = 'F')
164.10572738791328
Determine power at 2200 rpm, 20" MP, 2000 metres and -5 deg C
>>> pwr(2200, 20, 2000, -5, alt_units = 'm')
111.72954664842844
Determine power at 2200 rpm, 20" MP, 2000 metres and standard
temperature:
>>> pwr(2200, 20, 2000, alt_units = 'm')
110.29915330621547
"""
# convert units
altitude = U.length_conv(altitude, from_units = alt_units, to_units = 'ft')
if temp == 'std':
temp = SA.alt2temp(altitude, temp_units = temp_units)
temp = U.temp_conv(temp, from_units = temp_units, to_units = 'K')
# get standard temperature
temp_std = SA.alt2temp(altitude, temp_units = 'K')
# get power at standard temperature
pwr_std = _pwr_std_temp(rpm, MP, altitude)
# correct power for non-standard temperature
pwr = pwr_std * M.sqrt(temp_std / temp)
return pwr
def pwr(rpm, MP, altitude, temp = 'std', alt_units = 'ft', temp_units = 'C'):
"""
Returns horsepower for Lycoming IO-360-A series engines, given:
rpm - engine speed in revolutions per minute
MP - manifold pressure (" HG)
altitude - pressure altitude
temp - ambient temperature (optional - std temperature is used if no
temperature is input).
alt_units - (optional) - units for altitude, ft, m, or km
(default is ft)
temp_units - (optional) - units for temperature, C, F, K or R
(default is deg C)
The function replicates Lycoming curve 12700-A, and is valid at mixture
for maximum power.
Examples:
Determine power at 2620 rpm, 28 inches HG manifold pressure, 0 ft, and
-10 deg C:
>>> pwr(2620, 28, 0, -10)
197.71751932574702
Determine power at 2500 rpm, 25" MP, 5000 ft and 0 deg F:
>>> pwr(2500, 25, 5000, 0, temp_units = 'F')
171.87810350172663
Determine power at 2200 rpm, 20" MP, 2000 metres and -5 deg C
>>> pwr(2200, 20, 2000, -5, alt_units = 'm')
108.60284092217333
Determine power at 2200 rpm, 20" MP, 2000 metres and standard
temperature:
>>> pwr(2200, 20, 2000, alt_units = 'm')
107.2124765533882
"""
# convert units
altitude = U.length_conv(altitude, from_units = alt_units, to_units = 'ft')
if temp == 'std':
temp = SA.alt2temp(altitude, temp_units = temp_units)
temp = U.temp_conv(temp, from_units = temp_units, to_units = 'K')
# get standard temperature
temp_std = SA.alt2temp(altitude, temp_units = 'K')
# get power at standard temperature
pwr_std = _pwr_std_temp(rpm, MP, altitude)
# correct power for non-standard temperature
pwr = pwr_std * M.sqrt(temp_std / temp)
return pwr
def pwr(rpm, MP, altitude, temp='std', alt_units='ft', temp_units='C'):
"""
Returns horsepower for Lycoming O-360-A series engines, given:
rpm - engine speed in revolutions per minute
MP - manifold pressure (" HG)
altitude - pressure altitude
temp - ambient temperature (optional - std temperature is used if no
temperature is input).
alt_units - (optional) - units for altitude, ft, m, or km
(default is ft)
temp_units - (optional) - units for temperature, C, F, K or R
(default is deg C)
The function replicates Lycoming curve ??????? and is valid at mixture
for maximum power.
Examples:
Determine power at 2620 rpm, 28 inches HG manifold pressure, 0 ft,
and -10 deg C:
>>> pwr(2620, 28, 0, -10)
183.91485642478889
Determine power at 2500 rpm, 25" MP, 5000 ft and 0 deg F:
>>> pwr(2500, 25, 5000, 0, temp_units = 'F')
164.10572738791328
Determine power at 2200 rpm, 20" MP, 2000 metres and -5 deg C
>>> pwr(2200, 20, 2000, -5, alt_units = 'm')
111.72954664842844
Determine power at 2200 rpm, 20" MP, 2000 metres and standard
temperature:
>>> pwr(2200, 20, 2000, alt_units = 'm')
110.29915330621547
"""
# convert units
altitude = U.length_conv(altitude, from_units=alt_units, to_units='ft')
if temp == 'std':
temp = SA.alt2temp(altitude, temp_units=temp_units)
temp = U.temp_conv(temp, from_units=temp_units, to_units='K')
# get standard temperature
temp_std = SA.alt2temp(altitude, temp_units='K')
# get power at standard temperature
pwr_std = _pwr_std_temp(rpm, MP, altitude)
# correct power for non-standard temperature
pwr = pwr_std * np.sqrt(temp_std / temp)
return pwr
def pwr(rpm, MP, altitude, temp='std', alt_units='ft', temp_units='C'):
"""
Returns horsepower for Lycoming IO-360-A series engines, given:
rpm - engine speed in revolutions per minute
MP - manifold pressure (" HG)
altitude - pressure altitude
temp - ambient temperature (optional - std temperature is used if no
temperature is input).
alt_units - (optional) - units for altitude, ft, m, or km
(default is ft)
temp_units - (optional) - units for temperature, C, F, K or R
(default is deg C)
The function replicates Lycoming curve 12700-A, and is valid at mixture
for maximum power.
Examples:
Determine power at 2620 rpm, 28 inches HG manifold pressure, 0 ft, and
-10 deg C:
>>> pwr(2620, 28, 0, -10)
197.71751932574702
Determine power at 2500 rpm, 25" MP, 5000 ft and 0 deg F:
>>> pwr(2500, 25, 5000, 0, temp_units = 'F')
171.87810350172663
Determine power at 2200 rpm, 20" MP, 2000 metres and -5 deg C
>>> pwr(2200, 20, 2000, -5, alt_units = 'm')
108.60284092217333
Determine power at 2200 rpm, 20" MP, 2000 metres and standard
temperature:
>>> pwr(2200, 20, 2000, alt_units = 'm')
107.2124765533882
"""
# convert units
altitude = U.length_conv(altitude, from_units=alt_units, to_units='ft')
if temp == 'std':
temp = SA.alt2temp(altitude, temp_units=temp_units)
temp = U.temp_conv(temp, from_units=temp_units, to_units='K')
# get standard temperature
temp_std = SA.alt2temp(altitude, temp_units='K')
# get power at standard temperature
pwr_std = _pwr_std_temp(rpm, MP, altitude)
# correct power for non-standard temperature
pwr = pwr_std * M.sqrt(temp_std / temp)
return pwr
def temp2dynamic_viscosity(T, temp_units=default_temp_units,
dynamic_viscosity_units=default_dynamic_viscosity_units):
"""
Return dynamic viscosity given the air temperature.
Formula from US Standard Atmosphere, 1976 section 1.3.11 on page 19.
"""
T = U.temp_conv(T, temp_units, 'K')
u = 1.458e-6 * T**1.5 / (T + 110.4)
u = U.dynamic_viscosity_conv(u, 'Pa s', dynamic_viscosity_units)
return u
def prop_eff(prop,
bhp,
rpm,
tas,
altitude,
temp='std',
power_units='hp',
alt_units='ft',
temp_units='C',
speed_units='kt',
dia_units='in'):
"""
Returns propeller efficiency based on engine power provided to the propeller.
"""
press_ratio = SA.alt2press_ratio(altitude, alt_units=alt_units)
if temp == 'std':
temp = SA.alt2temp(altitude,
temp_units=temp_units,
alt_units=alt_units)
temp_ratio = U.temp_conv(temp, from_units=temp_units,
to_units='K') / 288.15
density_ratio = press_ratio / temp_ratio
density = density_ratio * SA.Rho0
Cp = bhp2Cp(bhp,
rpm,
density,
prop.dia,
power_units=power_units,
density_units='kg/m**3',
dia_units=dia_units)
J = advance_ratio(tas,
rpm,
prop.dia,
speed_units=speed_units,
dia_units=dia_units)
blade_tip_mach = tip_mach(tas,
rpm,
temp,
prop.dia,
speed_units=speed_units,
temp_units=temp_units,
dia_units=dia_units)
prop_eff = cp2eff(prop, Cp, J, blade_tip_mach)
if N.isnan(prop_eff):
raise ValueError('Out of range inputs')
return prop_eff
def temp2dynamic_viscosity(
T,
temp_units=default_temp_units,
dynamic_viscosity_units=default_dynamic_viscosity_units):
"""
Return dynamic viscosity given the air temperature.
Formula from US Standard Atmosphere, 1976 section 1.3.11 on page 19.
"""
T = U.temp_conv(T, temp_units, 'K')
u = 1.458e-6 * T**1.5 / (T + 110.4)
u = U.dynamic_viscosity_conv(u, 'Pa s', dynamic_viscosity_units)
return u
def alt2kinematic_viscosity(
H,
T='std',
alt_units=default_alt_units,
temp_units=default_temp_units,
kinematic_viscosity_units=default_kinematic_viscosity_units):
"""
Return kinematic viscosity, given altitude and an optional temperature input.
"""
density = alt2density(H, alt_units, density_units='kg/m**3')
isa_temp = alt2temp(H, alt_units, 'K')
if T != 'std':
isa_temp = alt2temp(H, alt_units, 'K')
T = U.temp_conv(T, temp_units, 'K')
density *= isa_temp / T
else:
T = U.temp_conv(isa_temp, 'K', temp_units)
u = temp2dynamic_viscosity(T, temp_units, 'Pa s')
v = u / density
v = U.kinematic_viscosity_conv(v, 'm**2/s', kinematic_viscosity_units)
return v
def blade_angle2bhp(prop,
blade_angle,
rpm,
tas,
altitude,
temp='std',
power_units='hp',
alt_units='ft',
temp_units='C',
speed_units='kt',
dia_units='in'):
"""
Returns returns engine power, given blade angle, rpm and flight conditions.
"""
press_ratio = SA.alt2press_ratio(altitude, alt_units=alt_units)
if temp == 'std':
temp = SA.alt2temp(altitude,
temp_units=temp_units,
alt_units=alt_units)
temp_ratio = U.temp_conv(temp, from_units=temp_units,
to_units='K') / 288.15
density_ratio = press_ratio / temp_ratio
density = density_ratio * SA.Rho0
# Cp = bhp2Cp(bhp, rpm, density, prop.dia, power_units = power_units, density_units = 'kg/m**3', dia_units = dia_units)
J = advance_ratio(tas,
rpm,
prop.dia,
speed_units=speed_units,
dia_units=dia_units)
blade_tip_mach = tip_mach(tas,
rpm,
temp,
prop.dia,
speed_units=speed_units,
temp_units=temp_units,
dia_units=dia_units)
Cp = blade_angle2cp(prop, blade_angle, J, blade_tip_mach)
bhp = cp2bhp(Cp,
rpm,
density,
prop.dia,
power_units=power_units,
density_units='kg/m**3',
dia_units=dia_units)
return bhp
def pp(rpm, MP, altitude, temp = 'std', alt_units = 'ft', temp_units = 'C'):
"""
Returns percent power for Lycoming IO-360-A series engines, given:
rpm - engine speed in revolutions per minute
MP - manifold pressure (" HG)
altitude - pressure altitude
temp - ambient temperature (optional - std temperature is used if no
temperature is input).
alt_units - (optional) - units for altitude, ft, m, or km
(default is ft)
temp_units - (optional) - units for temperature, C, F, K or R
(default is deg C)
The function replicates Lycoming curve 12700-A, and is valid at mixture
for maximum power.
Note: the output is rounded off to two decimal places.
Examples:
Determine power at 2620 rpm, 28 inches HG manifold pressure, 0 ft, and
-10 deg C:
>>> pp(2620, 28, 0, -10)
'98.86%'
Determine power at 2500 rpm, 25" MP, 5000 ft and 0 deg F:
>>> pp(2500, 25, 5000, 0, temp_units = 'F')
'85.94%'
Determine power at 2200 rpm, 20" MP, 2000 metres and -5 deg C
>>> pp(2200, 20, 2000, -5, alt_units = 'm')
'54.30%'
Determine power at 2200 rpm, 20" MP, 2000 metres and standard
temperature:
>>> pp(2200, 20, 2000, alt_units = 'm')
'53.61%'
"""
altitude = U.length_conv(altitude, from_units = alt_units, to_units = 'ft')
if temp == 'std':
temp = SA.alt2temp(altitude, temp_units = temp_units)
temp = U.temp_conv(temp, from_units = temp_units, to_units = 'C')
pp = pwr(rpm, MP, altitude, temp) / 2
# return pp
return '%.2f' % (pp) + '%'
def pp(rpm, MP, altitude, temp='std', alt_units='ft', temp_units='C'):
"""
Returns percent power for Lycoming IO-360-A series engines, given:
rpm - engine speed in revolutions per minute
MP - manifold pressure (" HG)
altitude - pressure altitude
temp - ambient temperature (optional - std temperature is used if no
temperature is input).
alt_units - (optional) - units for altitude, ft, m, or km
(default is ft)
temp_units - (optional) - units for temperature, C, F, K or R
(default is deg C)
The function replicates Lycoming curve 12700-A, and is valid at mixture
for maximum power.
Note: the output is rounded off to two decimal places.
Examples:
Determine power at 2620 rpm, 28 inches HG manifold pressure, 0 ft, and
-10 deg C:
>>> pp(2620, 28, 0, -10)
'98.86%'
Determine power at 2500 rpm, 25" MP, 5000 ft and 0 deg F:
>>> pp(2500, 25, 5000, 0, temp_units = 'F')
'85.94%'
Determine power at 2200 rpm, 20" MP, 2000 metres and -5 deg C
>>> pp(2200, 20, 2000, -5, alt_units = 'm')
'54.30%'
Determine power at 2200 rpm, 20" MP, 2000 metres and standard
temperature:
>>> pp(2200, 20, 2000, alt_units = 'm')
'53.61%'
"""
altitude = U.length_conv(altitude, from_units=alt_units, to_units='ft')
if temp == 'std':
temp = SA.alt2temp(altitude, temp_units=temp_units)
temp = U.temp_conv(temp, from_units=temp_units, to_units='C')
pp = pwr(rpm, MP, altitude, temp) / 2
# return pp
return '%.2f' % (pp) + '%'
def power_alt(ff, n, Hp, OAT, k=.00283, k2=.007, ff_units='USG/h', temp_units = 'F'):
"""
Alternate, simplified method to determine power. Assume that the fuel
flow for peak EGT varies linearly with density ratio and rpm. Then use
the main power method to calculate power for cases where there is not a
good indication of fuel flow at peak EGT. Only applicable to Lycoming
IO-360A series engines. Based on a very limited set of flight test data,
so the accuracy of the fuel flow at peak EGT has not been established
under all conditions.
"""
oat = U.temp_conv(OAT, from_units='F', to_units='R')
dr = SA.alt_temp2density_ratio(Hp, OAT, temp_units='F')
ff_peak_EGT = k * dr * n + k2 * oat
p = power(ff, ff_peak_EGT, n)
return p
def blade_angle(prop,
bhp,
rpm,
tas,
altitude,
temp='std',
power_units='hp',
alt_units='ft',
temp_units='C',
speed_units='kt',
dia_units='in'):
"""
Returns propeller blade angle.
"""
press_ratio = SA.alt2press_ratio(altitude, alt_units=alt_units)
if temp == 'std':
temp = SA.alt2temp(altitude,
temp_units=temp_units,
alt_units=alt_units)
temp_ratio = U.temp_conv(temp, from_units=temp_units,
to_units='K') / 288.15
density_ratio = press_ratio / temp_ratio
density = density_ratio * SA.Rho0
Cp = bhp2Cp(bhp,
rpm,
density,
prop.dia,
power_units=power_units,
density_units='kg/m**3',
dia_units=dia_units)
J = advance_ratio(tas,
rpm,
prop.dia,
speed_units=speed_units,
dia_units=dia_units)
blade_tip_mach = tip_mach(tas,
rpm,
temp,
prop.dia,
speed_units=speed_units,
temp_units=temp_units,
dia_units=dia_units)
blade_angle = cp2blade_angle(prop, Cp, J, blade_tip_mach)
return blade_angle
def pp2mp(percent_power,
rpm,
altitude,
temp='std',
alt_units='ft',
temp_units='C'):
"""
Returns manifold pressure in inches of mercury for a given percent
power, rpm, altitude and temperature (temperature input is optional
- standard temperature is used if no temperature is input).
Note: the output is rounded off to two decimal places.
Examples:
Determine manifold pressure required for 62.5% power at 2550 rpm
at 8000 ft and 10 deg C:
>>> pp2mp(62.5, 2550, 8000, 10)
'19.45'
Determine manifold pressure required for 75% power at 2500 rpm at
7500 ft at 10 deg F:
>>> pp2mp(75, 2500, 7500, 10, temp_units = 'F')
'22.25'
Determine manifold pressure required for 55% power at 2400 rpm at
9,500 ft at standard temperature:
>>> pp2mp(55, 2400, 9500)
'18.18'
"""
if percent_power <= 0:
raise ValueError('Power input must be positive.')
# convert units
altitude = U.length_conv(altitude, from_units=alt_units, to_units='ft')
if temp == 'std':
temp = SA.alt2temp(altitude, temp_units=temp_units)
temp = U.temp_conv(temp, from_units=temp_units, to_units='C')
pwr_seek = percent_power * 2
mp = pwr2mp(pwr_seek, rpm, altitude, temp)
return mp
def pp2rpm(percent_power,
mp,
altitude,
temp='std',
alt_units='ft',
temp_units='C'):
"""
Returns manifold pressure in inches of mercury for a given percent
power, rpm, altitude and temperature (temperature input is optional -
standard temperature is used if no temperature is input).
Examples:
Determine rpm required for 125 hp at 20 inches HG manifold pressure at
8000 ft and 10 deg C:
>>> pp2rpm(62.5, 20, 8000, 10)
2246
Determine rpm required for 75% power at 22 inches HG manifold pressure
at 6500 ft and 10 deg F:
>>> pp2rpm(75, 22, 6500, 10, temp_units = 'F')
2345
Determine rpm required for 55% power at at 18 inches HG manifold
pressure at 9,500 ft at standard temperature:
>>> pp2rpm(55, 18, 9500)
2423
"""
if percent_power <= 0:
raise ValueError('Power input must be positive.')
# convert units
altitude = U.length_conv(altitude, from_units=alt_units, to_units='ft')
if temp == 'std':
temp = SA.alt2temp(altitude, temp_units=temp_units)
temp = U.temp_conv(temp, from_units=temp_units, to_units='C')
pwr_seek = percent_power * 1.8
# print('Temp:', temp)
print('Power seeked:', pwr_seek)
rpm = pwr2rpm(pwr_seek, mp, altitude, temp)
return rpm
def density_alt2temp(
density_alt_seek,
press_alt,
alt_units=default_alt_units,
temp_units=default_temp_units,
):
"""
Return temperature to achieve a desired density altitude.
If the units are not specified, the units in default_units.py are used.
"""
low = -100 # initial lower guess
high = 100 # initial upper guess
# confirm initial low and high are OK:
da_low = density_alt(press_alt, low, alt_units=alt_units)
if da_low > density_alt_seek:
print('Initial low guess too high.')
da_high = density_alt(press_alt, high, alt_units=alt_units)
if da_high < density_alt_seek:
print('Initial high guess too low.')
guess = (low + high) / 2.
da_guess = density_alt(press_alt, guess, alt_units=alt_units)
# keep iterating until da is within 1 ft of desired value
while M.fabs(da_guess - density_alt_seek) > 1:
if da_guess > density_alt_seek:
high = guess
else:
low = guess
guess = (low + high) / 2.
da_guess = density_alt(press_alt, guess, alt_units=alt_units)
guess = U.temp_conv(guess, from_units='C', to_units=temp_units)
return guess
def density_alt2temp(
density_alt_seek,
press_alt,
alt_units=default_alt_units,
temp_units=default_temp_units,
):
"""
Return temperature to achieve a desired density altitude.
If the units are not specified, the units in default_units.py are used.
"""
low = -100. # initial lower guess
high = 100. # initial upper guess
# confirm initial low and high are OK:
da_low = density_alt(press_alt, low, alt_units=alt_units)
if da_low > density_alt_seek:
raise ValueError('Initial low guess too high.')
da_high = density_alt(press_alt, high, alt_units=alt_units)
if da_high < density_alt_seek:
raise ValueError('Initial high guess too low.')
guess = (low + high) / 2.
da_guess = density_alt(press_alt, guess, alt_units=alt_units)
# keep iterating until da is within 1 ft of desired value
while M.fabs(da_guess - density_alt_seek) > 1:
if da_guess > density_alt_seek:
high = guess
else:
low = guess
guess = (low + high) / 2.
da_guess = density_alt(press_alt, guess, alt_units=alt_units)
guess = U.temp_conv(guess, from_units='C', to_units=temp_units)
return guess
def pp2mp(percent_power, rpm, altitude, temp = 'std', alt_units = 'ft', temp_units = 'C'):
"""
Returns manifold pressure in inches of mercury for a given percent
power, rpm, altitude and temperature (temperature input is optional
- standard temperature is used if no temperature is input).
Note: the output is rounded off to two decimal places.
Examples:
Determine manifold pressure required for 62.5% power at 2550 rpm
at 8000 ft and 10 deg C:
>>> pp2mp(62.5, 2550, 8000, 10)
'19.45'
Determine manifold pressure required for 75% power at 2500 rpm at
7500 ft at 10 deg F:
>>> pp2mp(75, 2500, 7500, 10, temp_units = 'F')
'22.25'
Determine manifold pressure required for 55% power at 2400 rpm at
9,500 ft at standard temperature:
>>> pp2mp(55, 2400, 9500)
'18.18'
"""
if percent_power <= 0:
raise ValueError, 'Power input must be positive.'
# convert units
altitude = U.length_conv(altitude, from_units = alt_units, to_units = 'ft')
if temp == 'std':
temp = SA.alt2temp(altitude, temp_units = temp_units)
temp = U.temp_conv(temp, from_units = temp_units, to_units = 'C')
pwr_seek = percent_power * 2
mp = pwr2mp(pwr_seek, rpm, altitude, temp)
return mp
def pp2rpm(percent_power, mp, altitude, temp = 'std', alt_units = 'ft', temp_units = 'C'): """ Returns manifold pressure in inches of mercury for a given percent power, rpm, altitude and temperature (temperature input is optional - standard temperature is used if no temperature is input). Examples: Determine rpm required for 125 hp at 20 inches HG manifold pressure at 8000 ft and 10 deg C: >>> pp2rpm(62.5, 20, 8000, 10) 2246 Determine rpm required for 75% power at 22 inches HG manifold pressure at 6500 ft and 10 deg F: >>> pp2rpm(75, 22, 6500, 10, temp_units = 'F') 2345 Determine rpm required for 55% power at at 18 inches HG manifold pressure at 9,500 ft at standard temperature: >>> pp2rpm(55, 18, 9500) 2423 """ if percent_power <= 0: raise ValueError, 'Power input must be positive.' # convert units altitude = U.length_conv(altitude, from_units = alt_units, to_units = 'ft') if temp == 'std': temp = SA.alt2temp(altitude, temp_units = temp_units) temp = U.temp_conv(temp, from_units = temp_units, to_units = 'C') pwr_seek = percent_power * 1.8 # print 'Temp:', temp print 'Power seeked:', pwr_seek rpm = pwr2rpm(pwr_seek, mp, altitude, temp) return rpm
def power_alt(ff,
n,
Hp,
OAT,
k=.00283,
k2=.007,
ff_units='USG/h',
temp_units='F'):
"""
Alternate, simplified method to determine power. Assume that the fuel
flow for peak EGT varies linearly with density ratio and rpm. Then use
the main power method to calculate power for cases where there is not a
good indication of fuel flow at peak EGT. Only applicable to Lycoming
IO-360A series engines. Based on a very limited set of flight test data,
so the accuracy of the fuel flow at peak EGT has not been established
under all conditions.
"""
oat = U.temp_conv(OAT, from_units='F', to_units='R')
dr = SA.alt_temp2density_ratio(Hp, OAT, temp_units='F')
ff_peak_EGT = k * dr * n + k2 * oat
p = power(ff, ff_peak_EGT, n)
return p
def test_08(self):
Value = U.temp_conv(180, from_units='R', to_units='K')
Truth = 100
self.failUnless(RE(Value, Truth) <= 1e-5)
def test_07(self):
Value = U.temp_conv(100, from_units='K', to_units='R')
Truth = 180
self.failUnless(RE(Value, Truth) <= 1e-5)
def sat_press(
T='FALSE',
DP='FALSE',
RH=0.0,
temp_units=default_temp_units,
press_units=default_press_units,
):
"""
Return the saturated vapour pressure of water. Either the dew point, or
the temperature and the relative humidity must be specified. If both the
dew point and relative humidity are specified, the relative humidity value
is ignored.
If the temperature and dew point are both specified, the dew point cannot
be greater than the temperature:
If the units are not specified, the units in default_units.py are used.
>>> sat_press(T=10, DP=11)
Traceback (most recent call last):
File '<stdin>', line 1, in <module>
File 'std_atm.py', line 795, in sat_press
raise ValueError, 'The dew point cannot be greater than the temperature.'
ValueError: The dew point cannot be greater than the temperature.
Dew point is 11 deg (default temperature units). Find the water vapour
pressure in default pressure units:
>>> sat_press(DP=11)
0.38741015927568667
Dew point is 65 deg F. Find the water vapour pressure in default pressure units:
>>> sat_press(DP=65, temp_units = 'F')
0.62207710701956165
Dew point is 212 deg F (the boiling point of water at sea level).
Find the water vapour pressure in lb per sq. inch:
>>> sat_press(DP=212, temp_units = 'F', press_units = 'psi')
14.696764873564959
Temperature is 30 deg C. Find the water vapour pressure in default pressure units:
for 50% relative humidity:
>>> sat_press(T=30, RH = 0.5)
0.62647666996057927
"""
if DP != 'FALSE':
# use dew point method
if T != 'FALSE':
if DP > T:
print('The dew point cannot be greater than the temperature.')
DP = U.temp_conv(DP, from_units=temp_units, to_units='C')
# calculate vapour pressure
Pv = _sat_press(DP) * 100
else:
if RH == 'FALSE':
print(
'Either DP (dew point) or RH (relative humidity) must be specified.'
)
# relative humidity is specified
# confirm relative humidity is in range
if RH < 0 or RH > 1:
print('The relative humidity must be in the range of 0 to 1.')
if T == 'FALSE':
print(
'If the relative humidity is specified, the temperature must also be specified.'
)
T = U.temp_conv(T, from_units=temp_units, to_units='C')
Pv = _sat_press(T) * 100
Pv *= RH
Pv = U.press_conv(Pv, from_units='pa', to_units=press_units)
return Pv
def test_13(self):
Value = U.temp_conv(373.15, from_units='K', to_units='F')
Truth = 212
self.failUnless(RE(Value, Truth) <= 1e-8)
def density_alt_table(
density_alt_seek,
alt_range=2000,
alt_inc=100,
alt_units=default_alt_units,
temp_units=default_temp_units,
multi_units=False,
file='',
format='text',
):
"""
Return a text or html table of required temperature vs pressure altitude.
If the units are not specified, the units in default_units.py are used.
"""
line_buffer = []
if format == 'text':
line_buffer.append(
'Pressure altitudes and temperatures for a density ')
line_buffer.append('altitude of ' + str(density_alt_seek) + ' ' +
alt_units)
line_buffer.append('(assuming dry air)\n')
if multi_units:
line_buffer.append(' Pressure Temp Temp')
line_buffer.append(' Altitude')
line_buffer.append(' (' + alt_units + ') (deg C) (deg F)')
else:
line_buffer.append(' Pressure Temp')
line_buffer.append(' Altitude')
line_buffer.append(' (' + alt_units + ') (deg ' +
temp_units + ')')
elif format == 'html':
print('creating html')
else:
print('Invalid format. Must be either "text" or "html"')
if multi_units:
for alt in range(max(density_alt_seek - alt_range / 2., 0),
density_alt_seek + alt_range / 2. + alt_inc, alt_inc):
temp_c = density_alt2temp(density_alt_seek,
alt,
alt_units=alt_units)
temp_f = U.temp_conv(temp_c, from_units='C', to_units='F')
alt_str = L.format('%.*f', (0, alt), grouping=True)
temp_c_str = '%.1f' % temp_c
temp_f_str = '%.1f' % temp_f
line_buffer.append(
alt_str.rjust(6) + temp_c_str.rjust(11) + temp_f_str.rjust(10))
else:
for alt in range(max(density_alt_seek - alt_range / 2., 0),
density_alt_seek + alt_range / 2. + alt_inc, alt_inc):
alt_str = L.format('%.*f', (0, alt), grouping=True)
temp_str = '%.1f' % density_alt2temp(density_alt_seek,
alt,
temp_units=temp_units,
alt_units=alt_units)
line_buffer.append(alt_str.rjust(6) + temp_str.rjust(11))
if file != '':
OUT = open(file, 'w')
for line in line_buffer:
OUT.write(line + '\n')
print('file selected')
else:
return '\n'.join(line_buffer)
def test_08(self):
Value = U.temp_conv(180, from_units='R', to_units='K')
Truth = 100
self.failUnless(RE(Value, Truth) <= 1e-8)
def test_11(self):
Value = U.temp_conv(671.67, from_units='R', to_units='C')
Truth = 100
self.failUnless(RE(Value, Truth) <= 1e-8)
def test_02(self):
Value = U.temp_conv(100, from_units='C', to_units='F')
Truth = 212
self.failUnless(RE(Value, Truth) <= 1e-5)
def sat_press(
T='FALSE',
DP='FALSE',
RH=0.0,
temp_units=default_temp_units,
press_units=default_press_units,
):
"""
Return the saturated vapour pressure of water. Either the dew point, or
the temperature and the relative humidity must be specified. If both the
dew point and relative humidity are specified, the relative humidity value
is ignored.
If the temperature and dew point are both specified, the dew point cannot
be greater than the temperature:
If the units are not specified, the units in default_units.py are used.
>>> sat_press(T=10, DP=11)
Traceback (most recent call last):
File '<stdin>', line 1, in <module>
File 'std_atm.py', line 795, in sat_press
raise ValueError, 'The dew point cannot be greater than the temperature.'
ValueError: The dew point cannot be greater than the temperature.
Dew point is 11 deg (default temperature units). Find the water vapour
pressure in default pressure units:
>>> sat_press(DP=11)
0.38741015927568667
Dew point is 65 deg F. Find the water vapour pressure in default pressure units:
>>> sat_press(DP=65, temp_units = 'F')
0.62207710701956165
Dew point is 212 deg F (the boiling point of water at sea level).
Find the water vapour pressure in lb per sq. inch:
>>> sat_press(DP=212, temp_units = 'F', press_units = 'psi')
14.696764873564959
Temperature is 30 deg C. Find the water vapour pressure in default pressure units:
for 50% relative humidity:
>>> sat_press(T=30, RH = 0.5)
0.62647666996057927
"""
if DP != 'FALSE':
# use dew point method
if T != 'FALSE':
if DP > T:
raise ValueError('The dew point cannot be greater than the temperature.')
DP = U.temp_conv(DP, from_units=temp_units, to_units='C')
# calculate vapour pressure
Pv = _sat_press(DP) * 100.
else:
if RH == 'FALSE':
raise ValueError('Either DP (dew point) or RH (relative humidity) must be specified.')
# relative humidity is specified
# confirm relative humidity is in range
if RH < 0 or RH > 1:
raise ValueError('The relative humidity must be in the range of 0 to 1.')
if T == 'FALSE':
raise ValueError('If the relative humidity is specified, the temperature must also be specified.')
T = U.temp_conv(T, from_units=temp_units, to_units='C')
Pv = _sat_press(T) * 100.
Pv *= RH
Pv = U.press_conv(Pv, from_units='pa', to_units=press_units)
return Pv
def test_13(self):
Value = U.temp_conv(373.15, from_units='K', to_units='F')
Truth = 212
self.failUnless(RE(Value, Truth) <= 1e-5)
def test_14(self):
Value = U.temp_conv(-148, from_units='F', to_units='K')
Truth = 173.15
self.failUnless(RE(Value, Truth) <= 1e-5)
def test_12(self):
Value = U.temp_conv(-100, from_units='C', to_units='R')
Truth = 311.67
self.failUnless(RE(Value, Truth) <= 1e-5)
def test_11(self):
Value = U.temp_conv(671.67, from_units='R', to_units='C')
Truth = 100
self.failUnless(RE(Value, Truth) <= 1e-5)
def test_09(self):
Value = U.temp_conv(32, from_units='F', to_units='R')
Truth = 491.67
self.failUnless(RE(Value, Truth) <= 1e-5)
def test_04(self):
Value = U.temp_conv(212, from_units='F', to_units='C')
Truth = 100
self.failUnless(RE(Value, Truth) <= 1e-8)
def density_alt(
H,
T,
alt_setting=P0 / 100.,
DP='FALSE',
RH=0.0,
alt_units=default_alt_units,
temp_units=default_temp_units,
):
"""
Return density altitude, given the pressure altitude and the
temperature with altitudes in units of feet ('ft'), metres ('m'),
statute miles, ('sm') or nautical miles ('nm'), and temperature in units
of deg C, F, K or R ('C', 'F', 'K' or 'R').
Mandatory parametres:
H = altitude
T = temperature
Optional parametres:
alt_setting = altimeter setting (defaults to 29.9213 if not provided
DP = dew point
RH = relative humidity
alt_units = units for the altitude. 'ft', 'm', or 'km'.
temp_units = units for the temperature and dew point. 'C', 'F', 'K'
or 'R'.
The altimeter setting units are assumed to be inches of HG, unless the
value is greater than 35. In this case the units are assumed to be mb.
If the dew point or relative humidity are not specified, the air is
assumed to be completely dry. If both the dew point and relative humidity
are specified, the relative humidity value is ignored.
If the units are not specified, the units in default_units.py are used.
The method is from: http://wahiduddin.net/calc/density_altitude.htm
Examples:
Calculate the density altitude in default altitude units for a pressure
altitude of 7000 default altitude units and a temperature of 15 deg
(default temperature units). The altimeter setting is not specified, so it
defaults to standard pressure of 29.9213 in HG or 1013.25 mb:
>>> density_alt(7000, 15)
8595.3122796056014
Calculate the density altitude in default altitude units for a pressure
altitude of 7000 default altitude units and a temperature of 85 deg F.
The altimeter setting is not specified, so it defaults to standard pressure
of 29.9213 in HG or 1013.25 mb. The dew point and relative humidity are
not specified, so the air is assumed to be dry:
>>> density_alt(7000, 85, temp_units = 'F')
10159.073046375761
Calculate the density altitude in default altitude units for a pressure
altitude of 7000 default altitude units, an altimeter setting of 29.80 and
a temperature of 85 deg F and a dew point of 55 deg F:
>>> density_alt(7000, 85, 29.80, 55, temp_units = 'F')
10522.777736545509
Calculate the density altitude in metres for a pressure altitude of
2000 m, an altimeter setting of 1010 mb, a temperature of 15 deg (default
temperature units) and a relative humidity of 50%:
>>> density_alt(2000, 15, 1010, alt_units = 'm', RH = 0.5)
2529.8235607713582
The dew point may be specified in one of two ways: as the fourth
argument on the command line, or via the keyword argument DP.
>>> density_alt(2000, 15, 1010, alt_units = 'm', DP = 5)
2530.7533211614682
The relative humidity must be in the range of 0 to 1:
>>> density_alt(2000, 15, 1010, alt_units = 'm', RH = 1.1)
Traceback (most recent call last):
File \"<stdin>\", line 1, in <module>
File \"std_atm.py\", line 852, in density_alt
Pv = sat_press(T, DP, RH, temp_units, press_units='pa')
File \"std_atm.py\", line 962, in sat_press
'The relative humidity must be in the range of 0 to 1.'
ValueError: The relative humidity must be in the range of 0 to 1.
"""
Rv = 461.495 # gas constant for water vapour
# saturated vapour pressure
if DP == 'FALSE' and RH == 0:
Pv = 0
else:
Pv = sat_press(T, DP, RH, temp_units, press_units='pa')
# dry air pressure
Pd = dry_press(H, Pv, alt_setting=alt_setting, alt_units=alt_units,
press_units='pa')
T = U.temp_conv(T, from_units=temp_units, to_units='K')
D = Pd / (Rd * T) + Pv / (Rv * T)
DR = D / Rho0
return density_ratio2alt(DR, alt_units)
def test_05(self):
Value = U.temp_conv(473.15, from_units='K', to_units='C')
Truth = 200.
self.failUnless(RE(Value, Truth) <= 1e-8)
def density_alt_table(
density_alt_seek,
alt_range=2000,
alt_inc=100.,
alt_units=default_alt_units,
temp_units=default_temp_units,
multi_units=False,
file='',
format='text',
):
"""
Return a text or html table of required temperature vs pressure altitude.
If the units are not specified, the units in default_units.py are used.
"""
line_buffer = []
if format == 'text':
line_buffer.append('Pressure altitudes and temperatures for a density '
)
line_buffer.append('altitude of ' + str(density_alt_seek) + ' '
+ alt_units)
line_buffer.append('(assuming dry air)\n')
if multi_units:
line_buffer.append(' Pressure Temp Temp')
line_buffer.append(' Altitude')
line_buffer.append(' (' + alt_units
+ ') (deg C) (deg F)')
else:
line_buffer.append(' Pressure Temp')
line_buffer.append(' Altitude')
line_buffer.append(' (' + alt_units + ') (deg '
+ temp_units + ')')
elif format == 'html':
print('creating html')
else:
raise ValueError('Invalid format. Must be either "text" or "html"')
if multi_units:
for alt in range(max(density_alt_seek - alt_range / 2., 0),
density_alt_seek + alt_range / 2. + alt_inc,
alt_inc):
temp_c = density_alt2temp(density_alt_seek, alt,
alt_units=alt_units)
temp_f = U.temp_conv(temp_c, from_units='C', to_units='F')
alt_str = L.format('%.*f', (0, alt), grouping=True)
temp_c_str = '%.1f' % temp_c
temp_f_str = '%.1f' % temp_f
line_buffer.append(alt_str.rjust(6) + temp_c_str.rjust(11)
+ temp_f_str.rjust(10))
else:
for alt in range(max(density_alt_seek - alt_range / 2., 0),
density_alt_seek + alt_range / 2. + alt_inc,
alt_inc):
alt_str = L.format('%.*f', (0, alt), grouping=True)
temp_str = '%.1f' % density_alt2temp(density_alt_seek, alt,
temp_units=temp_units, alt_units=alt_units)
line_buffer.append(alt_str.rjust(6) + temp_str.rjust(11))
if file != '':
OUT = open(file, 'w')
for line in line_buffer:
OUT.write(line + '\n')
print('file selected')
else:
return '\n'.join(line_buffer)
def test_09(self):
Value = U.temp_conv(32, from_units='F', to_units='R')
Truth = 491.67
self.failUnless(RE(Value, Truth) <= 1e-8)
def test_14(self):
Value = U.temp_conv(-148, from_units='F', to_units='K')
Truth = 173.15
self.assertTrue(RE(Value, Truth) <= 1e-8)
def test_12(self):
Value = U.temp_conv(-100, from_units='C', to_units='R')
Truth = 311.67
self.failUnless(RE(Value, Truth) <= 1e-8)
def pwr2mp(pwr_seek,
rpm,
altitude,
temp='std',
alt_units='ft',
temp_units='C'):
"""
Returns manifold pressure in inches of mercury for a given power, rpm,
altitude and temperature (temperature input is optional - standard
temperature is used if no temperature is input).
Note: the output is rounded off to two decimal places.
Examples:
Determine manifold pressure required for 125 hp at 2550 rpm at 8000 ft
and 10 deg C:
>>> pwr2mp(125, 2550, 8000, 10)
'19.45'
Determine manifold pressure required for 75% power at 2500 rpm at
7500 ft at 10 deg F:
>>> pwr2mp(.75 * 200, 2500, 7500, 10, temp_units = 'F')
'22.25'
Determine manifold pressure required for 55% power at 2400 rpm at
9,500 ft at standard temperature:
>>> pwr2mp(.55 * 200, 2400, 9500)
'18.18'
"""
if pwr_seek <= 0:
raise ValueError('Power input must be positive.')
low = 0 # initial lower guess
high = 35 # initial upper guess
# convert units
altitude = U.length_conv(altitude, from_units=alt_units, to_units='ft')
if temp == 'std':
temp = SA.alt2temp(altitude, temp_units=temp_units)
temp = U.temp_conv(temp, from_units=temp_units, to_units='C')
# confirm initial low and high are OK:
pwr_low = pwr(rpm, low, altitude, temp)
if pwr_low > pwr_seek:
raise ValueError('Initial low guess too high.')
pwr_high = pwr(rpm, high, altitude, temp)
if pwr_high < pwr_seek:
raise ValueError('Initial high guess too low.')
guess = (low + high) / 2.
pwr_guess = pwr(rpm, guess, altitude, temp)
# keep iterating until power is within 0.1% of desired value
while M.fabs(pwr_guess - pwr_seek) / pwr_seek > 1e-3:
if pwr_guess > pwr_seek:
high = guess
else:
low = guess
guess = (low + high) / 2.
pwr_guess = pwr(rpm, guess, altitude, temp)
# result = int(guess) + round(guess % 1, 2))
# return guess
# return result
return '%.2f' % (guess)
def test_14(self):
Value = U.temp_conv(-148, from_units='F', to_units='K')
Truth = 173.15
self.failUnless(RE(Value, Truth) <= 1e-8)
def pwr2rpm(pwr_seek,
mp,
altitude,
temp='std',
alt_units='ft',
temp_units='C'):
"""
Returns rpm for a given power, manifold pressure in inches of mercury,
altitude and temperature (temperature input is optional - standard
temperature is used if no temperature is input).
Note: the output is rounded off to the nearest rpm.
Examples:
Determine rpm required for 125 hp at 20 inches HG manifold pressure at
8000 ft and 10 deg C:
>>> pwr2rpm(125, 20, 8000, 10)
2477
Determine rpm required for 75% power at 22 inches HG manifold pressure
at 6500 ft and 10 deg F:
>>> pwr2rpm(.75 * 200, 22, 6500, 10, temp_units = 'F')
2547
Determine rpm required for 55% power at at 18 inches HG manifold
pressure at 9,500 ft at standard temperature:
>>> pwr2rpm(.55 * 200, 18, 9500)
2423
"""
if pwr_seek <= 0:
raise ValueError('Power input must be positive.')
low = 1000 # initial lower guess
high = 3500 # initial upper guess
# convert units
altitude = U.length_conv(altitude, from_units=alt_units, to_units='ft')
if temp == 'std':
temp = SA.alt2temp(altitude, temp_units=temp_units)
temp = U.temp_conv(temp, from_units=temp_units, to_units='C')
# confirm initial low and high are OK:
pwr_low = pwr(low, mp, altitude, temp)
# print "pwr_low=", pwr_low
if pwr_low > pwr_seek:
raise ValueError('Initial low guess too high.')
pwr_high = pwr(high, mp, altitude, temp)
# print "pwr_high=", pwr_high
if pwr_high < pwr_seek:
# print "pwr_high=", pwr_high
print("Function called was IO.pwr(%f, %f, %f, %f)" %
(high, mp, altitude, temp))
raise ValueError('Initial high guess too low.')
guess = (low + high) / 2.
pwr_guess = pwr(guess, mp, altitude, temp)
# keep iterating until power is within 0.1% of desired value
while M.fabs(pwr_guess - pwr_seek) / pwr_seek > 1e-4:
if pwr_guess > pwr_seek:
high = guess
else:
low = guess
guess = (low + high) / 2.
pwr_guess = pwr(guess, mp, altitude, temp)
return int(round(guess, 0))
def test_10(self):
Value = U.temp_conv(671.67, from_units='R', to_units='F')
Truth = 212
self.failUnless(RE(Value, Truth) <= 1e-5)
def prop_data(
prop,
bhp,
rpm,
tas,
altitude,
temp="std",
power_units="hp",
alt_units="ft",
temp_units="C",
speed_units="kt",
dia_units="in",
thrust_units="lb",
):
"""
Returns advance ratio, power coefficient, thrust coefficient, blade tip
mach number, propeller efficiency and thrust.
Validated against Excel spreadsheet provided by Les Doud (Hartzell).
"""
press_ratio = SA.alt2press_ratio(altitude, alt_units=alt_units)
if temp == "std":
temp = SA.alt2temp(altitude, temp_units=temp_units, alt_units=alt_units)
temp_ratio = U.temp_conv(temp, from_units=temp_units, to_units="K") / 288.15
density_ratio = press_ratio / temp_ratio
density = density_ratio * SA.Rho0
Cp = bhp2Cp(bhp, rpm, density, prop.dia, power_units=power_units, density_units="kg/m**3", dia_units=dia_units)
J = advance_ratio(tas, rpm, prop.dia, speed_units=speed_units, dia_units=dia_units)
blade_tip_mach = tip_mach(
tas, rpm, temp, prop.dia, speed_units=speed_units, temp_units=temp_units, dia_units=dia_units
)
prop_eff = cp2eff(prop, Cp, J, blade_tip_mach)
try:
Ct = cp2ct(prop, Cp, J, blade_tip_mach)
except:
Ct = cp2ct_alt(
prop,
Cp,
bhp,
rpm,
tas,
altitude,
temp=temp,
power_units=power_units,
alt_units=alt_units,
temp_units=temp_units,
speed_units=speed_units,
)
if prop_eff > 0.1:
thrust = eff2thrust(
prop_eff, bhp, tas, power_units=power_units, speed_units=speed_units, thrust_units=thrust_units
)
else:
thrust = ct2thrust(
Ct, density, rpm, prop.dia, thrust_units=thrust_units, density_units="kg/m**3", dia_units=dia_units
)
# data_block = 'J = ' + str(J) + '\nCp = ' + str(Cp) + '\n Tip mach = ' + str(blade_tip_mach) + '\n Ct = ' + str(Ct) + '\n Thrust = ' + str(thrust) + ' ' + thrust_units + '\n Prop efficiency = ' + str(prop_eff)
print " prop = ", prop.prop
print " J = %.3f" % J
print " Cp = %.5f" % Cp
print " Tip Mach = %.3f" % blade_tip_mach
print " Ct = %.3f" % Ct
print " Thrust = %.2f" % thrust, thrust_units
print "Prop efficiency = %.4f" % prop_eff
print " Thrust HP = %.2f" % bhp * prop_eff
return
def density_alt(
H,
T,
alt_setting=P0,
DP='FALSE',
RH=0.0,
alt_units=default_alt_units,
temp_units=default_temp_units,
):
"""
Return density altitude, given the pressure altitude and the
temperature with altitudes in units of feet ('ft'), metres ('m'),
statute miles, ('sm') or nautical miles ('nm'), and temperature in units
of deg C, F, K or R ('C', 'F', 'K' or 'R').
Mandatory parametres:
H = altitude
T = temperature
Optional parametres:
alt_setting = altimeter setting (defaults to 29.9213 if not provided
DP = dew point
RH = relative humidity
alt_units = units for the altitude. 'ft', 'm', or 'km'.
temp_units = units for the temperature and dew point. 'C', 'F', 'K'
or 'R'.
The altimeter setting units are assumed to be inches of HG, unless the
value is greater than 35. In this case the units are assumed to be mb.
If the dew point or relative humidity are not specified, the air is
assumed to be completely dry. If both the dew point and relative humidity
are specified, the relative humidity value is ignored.
If the units are not specified, the units in default_units.py are used.
The method is from: http://wahiduddin.net/calc/density_altitude.htm
Examples:
Calculate the density altitude in default altitude units for a pressure
altitude of 7000 default altitude units and a temperature of 15 deg
(default temperature units). The altimeter setting is not specified, so it
defaults to standard pressure of 29.9213 in HG or 1013.25 mb:
>>> density_alt(7000, 15)
8595.3465863232504
Calculate the density altitude in default altitude units for a pressure
altitude of 7000 default altitude units and a temperature of 85 deg F.
The altimeter setting is not specified, so it defaults to standard pressure
of 29.9213 in HG or 1013.25 mb. The dew point and relative humidity are
not specified, so the air is assumed to be dry:
>>> density_alt(7000, 85, temp_units = 'F')
10159.10696106757
Calculate the density altitude in default altitude units for a pressure
altitude of 7000 default altitude units, an altimeter setting of 29.80 and
a temperature of 85 deg F and a dew point of 55 deg F:
>>> density_alt(7000, 85, 29.80, 55, temp_units = 'F')
10522.776013011618
Calculate the density altitude in metres for a pressure altitude of
2000 m, an altimeter setting of 1010 mb, a temperature of 15 deg (default
temperature units) and a relative humidity of 50%:
>>> density_alt(2000, 15, 1010, alt_units = 'm', RH = 0.5)
2529.8230634449737
The dew point may be specified in one of two ways: as the fourth
argument on the command line, or via the keyword argument DP.
>>> density_alt(2000, 15, 1010, alt_units = 'm', DP = 5)
2530.7528237990618
The relative humidity must be in the range of 0 to 1:
>>> density_alt(2000, 15, 1010, alt_units = 'm', RH = 1.1)
Traceback (most recent call last):
File '<stdin>', line 1, in ?
File 'std_atm.py', line 533, in density_alt
raise ValueError, 'The relative humidity must be in the range of 0 to 1.'
ValueError: The relative humidity must be in the range of 0 to 1.
"""
Rv = 461.495 # gas constant for water vapour
# saturated vapour pressure
if DP == 'FALSE' and RH == 0:
Pv = 0
else:
Pv = sat_press(T, DP, RH, temp_units, press_units='pa')
# dry air pressure
Pd = dry_press(H,
Pv,
alt_setting=alt_setting,
alt_units=alt_units,
press_units='pa')
T = U.temp_conv(T, from_units=temp_units, to_units='K')
D = Pd / (Rd * T) + Pv / (Rv * T)
DR = D / Rho0
return density_ratio2alt(DR, alt_units)
def test_02(self):
Value = U.temp_conv(100, from_units='C', to_units='F')
Truth = 212
self.failUnless(RE(Value, Truth) <= 1e-8)
def test_05(self):
Value = U.temp_conv(473.15, from_units='K', to_units='C')
Truth = 200.
self.failUnless(RE(Value, Truth) <= 1e-5)
def test_04(self):
Value = U.temp_conv(212, from_units='F', to_units='C')
Truth = 100
self.failUnless(RE(Value, Truth) <= 1e-5)
