Fluke RPM4-AD, Руководство по эксплуатации и обслуживанию

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RPM4-AD™ OPERATION AND MAINTENANCE MANUAL
© 2005-2007 DH Instruments, a Fluke Company Page 136
True Airspeed
True airspeed is the airspeed adjusted for the current altitude and specified temperature.
The measured static pressure and input temperature impact the final air speed value. The
fundamental equations and process are identical to the calibrated airspeed case. The
exception is that the P and T values are the current static pressure and temperature instead
of standard pressure (101325 Pa) and temperature (15 ºC by convention) at sea level.
Subsonic speeds (V<a
t
)
Supersonic speeds (V>a
t
)
Airspeed variable definitions
VARIABLE DESCRIPTION
V
c
Calculated airspeed in meters per second assuming sea level atmospheric
conditions. P = 101325 Pa and T = 288.15K
V
t
Calculated true airspeed in meters per second. The measured value for static
pressure and user input value for temperature are used to determine V.
V
Calculated air speed in meters per second. The input P and T conditions determine
true or calibrated air speed.
a
t
Speed of sound as a function of static temperature.
q
c
The differential pressure in Pa.
P
Static pressure in Pa. For calibrated airspeed, 101325Pa is always used.
T
Static temperature in K. For calibrated airspeed, 288.15K (15 ºC) is always used.
P
t
The optionally input total pressure in Pa. This pressure is also referred to as the
dynamic pressure.
R
Gas constant. 287.05287 j/(Kkg)
γ
Constant ratio of specific heats of air (1.400).
M
Calculated Mach number as a function of static pressure.
q
c
The input or calculated differential pressure converted into Pa.