Air Data Computer - Minimum Performance Standard
This SAE Aerospace Standard (AS) covers air data computer equipment (hereinafter designated the computer) which when connected to sources of aircraft electrical power, static pressure, total pressure, outside air temperature, and others specified by the manufacturer (singly or in combination) provides some or all of the following computed air data output signals (in analog and/or digital form) which may supply primary flight instruments: pressure altitude; pressure altitude, baro-corrected; vertical speed; calibrated airspeed; mach number; maximum allowable airspeed; overspeed warning; and total air temperature. In addition, the computer may supply one or more of the following signals: pressure altitude, digitized; equivalent airspeed; true airspeed; static air temperature; altitude hold; airspeed hold; mach hold; angle of attack; flight control gain scheduling; and others.
Rationale: FAA TSO-C106 refers to SAE AS8002A for the minimum performance requirements that must be met to receive TSO authorization. EASA has harmonized ETSO-C106 with FAA TSO-C106 as the first step to improve the qualification standards for air data computers. Comments received during the implementation of Reduced Vertical Separation Minimum (RVSM) standards for transport aircraft have highlighted the following areas for improvement:
1) The AS8002A minimum altitude performance requirements are not sufficiently conservative in the RVSM altitude range of 29,000 to 41,000 feet. Most current aircraft manufacturer’s altitude requirements are also more conservative than the AS8002A requirements outside of the RVSM regime.
2) The AS8002A minimum altitude performance requirements do not address long term stability of the air data computer which can impact aircraft level compliance to RVSM.
3) The AS8002A requirements for barometric corrected altitude and static source error corrections performance are not aligned with current performance of digital air data computers.
4) The TSO and AS8002A environmental requirements are per RTCA DO-160B which is not consistent with RTCA DO-160G the current industry standard.