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National Advisory Committee for Aeronautics, Technical Notes - A Method of Calibrating Airspeed Installations on Airplanes at Transonic and Supersonic Speeds by Use of Temperature Measurements

A.method is described of calibrating airspeed installations on
airplanes at transonic and supersonic speeds by use of instrumentation
in the airplane only. The method consists in first making a survey of
temperature, static pressure, and total pressure over the desired range
of altitudes at speeds for which the airspeed calibration is known.
The airplane is then flown at speeds for which the calibration is
desired through the range of altitude surveyed, and the measurements
of temperature, static pressure, and total pressure are repeated.

The values of total pressure and indicated temperature at a given instant
in the calibration run, together with the temperature recovery factor
of the thermometer, define the relation between ambient temperature and
static pressure at that instant. Comparison of this relation with that
determined from the survey gives the value of free-stream static
pressure at that instant. The static-pressure error is then obtained
by subtracting the free-stream static pressure from the indicated static
pressure. This method requires precise measurements of temperature. An
accuracy in the calibration of 1.0 percent of Mach number near a Mach
number of 1.0 correspOnds to an accuracy in the measurement of temperature.

The static-pressure source of a pitot-static airspeed installation
on an airplane may be calibrated at low altitude and subsonic speeds, -J
principally in level flight, by any one or more of several methods --
described in reference 1. For levelgflight runs, dives, and maneuvers
at high speeds and high altitudes, the radar method described in refer-
ence 2 may be used. In this method, the radar-phototheodolite tracking
equipment is used to establish the geometric altitude of thé airplane
in surveys of atmospheric pressure made at speeds for which the airspeed
calibration is known and in maneuvers under conditions for which the
calibration is desired.