Analysis of ILS receiver output data and comparison to U.S. flight inspection tolerances

ICAO Annex 10 contains the integrity and continuity requirements for instrument landing systems (ILS) ground systems. Service providers are required to demonstrate that systems offered for operational service comply with these requirements. This includes an assessment of integrity and an evaluation of continuity of service as part of the initial certification and activities to guarantee continued compliance over the life-cycle of the system. In assessing integrity, the signals are monitored to ensure that performance is within the requirements established by ICAO. In the United States the vertical and horizontal guidance signals provided by the ILS are also verified by the Federal Aviation Administration Flight Inspection. Extensive ground and flight tests are made to ensure that all parameters of the radiated signal are compliant with ICAO Annex 10. Flight inspection aircraft fly specific flight profiles and measure the radiated signal. The measured data is then compared to the radiated signal requirements. The signal requirements, which are known as tolerance limits, are also dependent on the category of flight. This paper details the various flight profiles used to evaluate the radiated signal. In addition, the requirements and the analysis techniques are provided.