def twrequired_sec(self, wingloading_pa):
"""T/W required for a service ceiling for a range of wing loadings"""
if self.servceil_m == -1:
secmsg = "Climb rate not specified in the designbrief dictionary."
raise ValueError(secmsg)
if self.secclimbspd_kias == -1:
secmsg = "Best climb speed not specified in the designbrief dictionary."
raise ValueError(secmsg)
secclimbspeed_mpsias = co.kts2mps(self.secclimbspd_kias)
secclimbspeed_mpstas = self.designatm.eas2tas(secclimbspeed_mpsias,
self.servceil_m)
wingloading_pa = actools.recastasnpfloatarray(wingloading_pa)
# W/S at the start of the service ceiling test point may be less than MTOW/S
wingloading_pa = wingloading_pa * self.sec_weight_fraction
inddragfact = self.induceddragfact(whichoswald=123)
qclimb_pa = self.designatm.dynamicpressure_pa(secclimbspeed_mpstas,
self.servceil_m)
# Service ceiling typically defined in terms of climb rate (at best climb speed) of
# dropping to 100feet/min ~ 0.508m/s
climbrate_mps = co.fpm2mps(100)
# What true climb rate does 100 feet/minute correspond to?
climbrate_mpstroc = self.designatm.eas2tas(climbrate_mps,
self.servceil_m)
twratio = climbrate_mpstroc / secclimbspeed_mpstas + \
(1 / wingloading_pa) * qclimb_pa * self.cdminclean + \
(inddragfact / qclimb_pa) * wingloading_pa
# What SL T/W will yield the required T/W at the actual altitude?
temp_c = self.designatm.airtemp_c(self.servceil_m)
pressure_pa = self.designatm.airpress_pa(self.servceil_m)
density_kgpm3 = self.designatm.airdens_kgpm3(self.servceil_m)
mach = self.designatm.mach(secclimbspeed_mpstas, self.servceil_m)
corr = self._altcorr(temp_c, pressure_pa, mach, density_kgpm3)
twratio = twratio / corr
# Map back to T/MTOW if service ceiling test start weight is less than MTOW
twratio = twratio * self.sec_weight_fraction
if len(twratio) == 1:
return twratio[0]
return twratio
def twrequired_clm(self, wingloading_pa):
"""Calculates the T/W required for climbing for a range of wing loadings.
**Parameters**
wingloading_pa
float or numpy array, list of wing loading values in Pa.
**Returns**
twratio
array, thrust to weight ratio required for the given wing loadings.
**See also** ``twrequired``
**Notes**
1. Use `twrequired` if a full constraint analysis is desired, as this integrates
the take-off, turn, climb, cruise, and service ceiling constraints, as well as
computing the combined constraint boundary.
2. The calculation currently approximates climb performance on the constant TAS
assumption (though note that the design brief dictionary variable must specify the
climb speed as IAS, which is the operationally relevant figure) - a future version
of the code will remove this approximation and assume constant IAS.
**Example**
Given a climb rate (in feet per minute) and a climb speed (KIAS), as well as an
altitude (in a given atmosphere) where these must be achieved, as well as
a set of basic geometrical and aerodynamic performance parameters, compute the necessary
T/W ratio to hold the specified climb rate.
::
from ADRpy import atmospheres as at
from ADRpy import constraintanalysis as ca
designbrief = {'climbalt_m': 0, 'climbspeed_kias': 101,
'climbrate_fpm': 1398}
etap = {'climb': 0.8}
designperformance = {'CDminclean': 0.0254, 'etaprop' :etap}
designdef = {'aspectratio': 10.12, 'sweep_le_deg': 2,
'sweep_mt_deg': 0, 'bpr': -1}
TOW_kg = 1542.0
designatm = at.Atmosphere()
concept = ca.AircraftConcept(designbrief, designdef,
designperformance, designatm)
wingloadinglist_pa = [1250, 1500, 1750]
twratio = concept.twrequired_clm(wingloadinglist_pa)
print('T/W: ', twratio)
Output: ::
T/W: [ 0.20249491 0.2033384 0.20578177]
"""
if self.climbspeed_kias == -1:
turnmsg = "Climb speed not specified in the designbrief dictionary."
raise ValueError(turnmsg)
climbspeed_mpsias = co.kts2mps(self.climbspeed_kias)
# Assuming that the climb rate is 'indicated'
if self.climbrate_fpm == -1:
turnmsg = "Climb rate not specified in the designbrief dictionary."
raise ValueError(turnmsg)
climbrate_mps = co.fpm2mps(self.climbrate_fpm)
climbspeed_mpstas = self.designatm.eas2tas(climbspeed_mpsias, self.servceil_m)
climbrate_mpstroc = self.designatm.eas2tas(climbrate_mps, self.servceil_m)
wingloading_pa = actools.recastasnpfloatarray(wingloading_pa)
# W/S at the start of the specified climb segment may be less than MTOW/S
wingloading_pa = wingloading_pa * self.climb_weight_fraction
inddragfact = self.induceddragfact(whichoswald=123)
qclimb_pa = self.designatm.dynamicpressure_pa(climbspeed_mpstas, self.climbalt_m)
cos_sq_theta = (1 - (climbrate_mpstroc / climbspeed_mpstas) ** 2)
# To be implemented, as 1 + (V/g)*(dV/dh)
accel_fact = 1.0
twratio = accel_fact * climbrate_mpstroc / climbspeed_mpstas + \
(1 / wingloading_pa) * qclimb_pa * self.cdminclean + \
(inddragfact / qclimb_pa) * wingloading_pa * cos_sq_theta
# What SL T/W will yield the required T/W at the actual altitude?
temp_c = self.designatm.airtemp_c(self.climbalt_m)
pressure_pa = self.designatm.airpress_pa(self.climbalt_m)
density_kgpm3 = self.designatm.airdens_kgpm3(self.climbalt_m)
mach = self.designatm.mach(climbspeed_mpstas, self.climbalt_m)
corr = self._altcorr(temp_c, pressure_pa, mach, density_kgpm3)
twratio = twratio / corr
# Map back to T/MTOW if climb start weight is less than MTOW
twratio = twratio * self.climb_weight_fraction
if len(twratio) == 1:
return twratio[0]
return twratio