What is Flight Test Equipment?
Typical names for these devices are nose booms, wing booms, trailing cones and trailing bombs. These products provide pressure and airflow direction data to data acquisition and air data computers for computation of aircraft orientation, airspeed, altitude, and related information. This range of parameters is collectively known as “air data” and is generally comprised of:
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total pressure: the sum of local atmospheric pressures plus dynamic (operating (ram or impact)) pressures. Algebraically, total pressure (Pt) equals the sum of static pressure (Ps) plus impact pressure (qc)
Pt = Ps + qc |
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| Ps |
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static pressure: the absolute pressure of still sir surrounding a body; the atmospheric pressure at the flight level of the aircraft |
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| Qc |
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impact pressure: a calculated value, it is the difference between total pressure and static pressure; it is the pressure created by the forward speed of the aircraft |
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| α |
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angle of attack: the angle measured in the XZ plane between the X axis and the relative air flow; also designated as AOA, alpha, or α; angle of attack is not the same concept as ‘pitch’ which indicates the rotation of the aircraft relative to three imaginary lines running through an airplane and intersecting at right angles at the airplane’s center of gravity |
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| β |
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angle of sideslip: the angle measured in the XY plane between the X axis and the relative air flow; also designated as AOS, bets, or β; angle of sideslip is not the same concept as ‘yaw’ which indicates the rotation of the aircraft relative to three imaginary lines running through an airplane and intersecting at right angles at the airplane’s center of gravity |
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| TT |
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total air temperature: the temperature of an airflow measured as the airflow is brought to rest without removal or addition of heat; also designated as TAT or TT |
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| OAT |
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outside air temperature: the temperature of the static outside temperature without the effects of airspeed; also designated as OAT |
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The above parameters allow a number of other parameters to be calculated such as airspeed, altitude, true airspeed, and Mach number.
Useful References:
Military Specification MIL-P-26292 (USAF)
"Pilot and Static Pressure Systems, Installation and Inspection Of"
NASA Reference Publication 1046
"Measurement of Aircraft Speed and Altitude," Wm. Gracey, May 1980 #N80-24296
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