IHS ESDU Pitot and static errors due to non-steady flight. 85011

ESDU 85011 treats the additional corrections to the pitot and static pressures, registered by their sensors in unsteady flight conditions, required to allow the use of the steady-flight calibrations. The corrections arise because there is a lag in the transmission of a pressure change at the sensor ports to the instrumentation. That lag is caused by acoustic and friction effects in the airflow in the system when the pressures are changing but, for high- performance aircraft, includes contributions from the inertia of the air mass in the pressure system in accelerated flight and, when the static ports are relatively small, a lag additional to that found in ground calibrations that is thought to be due to the flow through the ports themselves. ESDU 85011 provides estimation methods for each contribution to lag for use when measured values are not available, and allows corrections derived from ground (or flight) calibrations to be adjusted to apply to different conditions from those under which they were obtained. A practical worked example demonstrates how the methods are applied.