In this article, we investigate the impact of redundant MEMS-IMU on a loosely coupled INS/GBAS system. Therefore, we considered and analyze the combined performance of three identically and orthogonally mounted low-cost IMUs. It is shown that due to the redundancy, the INS based position error is reduced by an average factor of two. In conventional GBAS, no position solution can be obtain while GPS outages which lead to a full system failure. It is demonstrated that our redundant INS/ GBAS integration sufficiently bridges GPS outages up to 10 seconds. Hence, the system availability is significantly improved. Additionally, an integrity concept is introduced providing integrity information even in the case where no GPS solution is available. This is essential for all safety-of-life applications such as civil aviation. We analyze our concept both, analytically and by Monte-Carlo Simulations. Our investigations clearly show that the robustness of the GBAS can be dramatically increased while maintaining low-costs and low-complexity.