Testing Safety Critical Ada Code Using Non Real Time Testing

Abstract

Testing the Flight Control Laws and the Airdata Algorithm form a major part of the Flight Control System development cycle. These two safety critical software are validated and verified on very costly rigs in every aircraft development program. The Indian Light Combat Aircraft, with fixed gains and the limited first flight envelope, was successfully test flown without a single software fault starting January 4, 2001. This paper highlights a new methodology followed by the LCA team to test and certify the digital fly-by-wire control law. The philosophy used is to test the quadruplex software in a single strand mode. Only the Control Laws and the Airdata Algorithm are tested against a validated FORTRAN model. The Model code is developed by the Control Law designers and represents the functionality in totality. A fault injection methodology is used on the model, called “Delta Model”, to verify the efficacy of the test cases. The paper discusses the methods, typical cases and shares some of the experiences of the Indian LCA Team.