Smart air-data probe for fault-tolerant flow measurements

This paper deals with the development of a smart multi-hole probe for aircraft air data parameters. The system aims at the calculation of static and total pressures, and the angle-of-attack and angle-of-sideslip (fine output data) starting from the elaboration of the pressure measurements on holes (raw input data). The probe, characterized by fault-tolerant capabilities with respect the loss of one pressure data, is developed as an embedded system that includes MEMS pressure/temperature sensors and a control electronics implementing multiple reconstructions of the flow measurements, up to obtain fault-tolerant output data. The basic idea for the reconstruction algorithm is that, in the normal envelope of aircraft flow angles (≤15° for both attack and sideslip), the shape of the pressure field around the stagnation point of a hemispherical body is essentially independent from the flow angles. Thus, once characterised the aerodynamic flow at the aircraft installation for zero angle of attack and sideslip, the reconstruction is performed by minimising the errors between the five pressure measurements on the probe tip and the predictions of models imposing a set of locations of the stagnation point. The external geometry of the probe is designed and validated by CFD simulations. In particular, CFD simulations have been performed to verify both the basic concept and the capability of the algorithm to provide the flow angles even if one of the pressure measurements is not available. The work describes the reconstruction algorithm and the system development, from the conceptual phase, up to the manufacturing of the first prototype to be used for the experimental tests.