Abstract:

The position of the pressure air data sensor on an aircraft will affect the measurement of ambient static pressure. Also, for some aircraft this may be influenced by the engine intake flow field; then the pressure error will be a function of engine operating condition.

This Technical Memorandum shows an example of a subsonic aircraft powered by a single turbofan engine (fed by air intakes positioned either side of the forward fuselage) for which performance data are available from the engine manufacturer. The aircraft is fitted with a nose-mounted instrumentation boom which carries angle of attack and sideslip vanes aft of a Pitot-static head. The probe had been tested in a wind tunnel, hence pressure correction coefficients were available for the probe uninfluenced by the aircraft.

The configuration of the aircraft is such that the forward fuselage is heavily influenced by the engine intake flow field and static pressure corrections were found to correlate with intake mass flow ratio. The modelling presented is applicable to subsonic flight and in manoeuvres where sideslip is not significant. Also, it is assumed that there is no error in the measured total pressure.