Smoother Guidance - Less Emissions? GNSS-based Precision Approach Guidance vs. ILS

Abstract

In this paper we analyze the potential for fuel and CO2savings brought about by the smoother precision approach guidance of satellite-based navigation systems compared to the currently most used system, the instrument landing system (ILS). We conducted several simulated approaches in a Level D Full Flight Simulator of an Airbus A330-300 to determine if there is a measurable difference in fuel consumption and corresponding CO2emissions. To simulate ILS errors, we implemented an error model into the flight simulator representing real errors obtained from flight inspection. Due to the relatively small errors in guidance based on satellite navigation we used an ideal geometric glide path without errors as reference. Results showed that the smoother guidance alone does not provide significant fuel and emission savings. However, the vertical error of the ILS at the intercept altitude changes the effective glide path angle of the approach leading to potential savings or increased fuel use, depending if the error is positive or negative. Hence, no general statement can be made which system enables fuel savings, but it rather depends on the error characteristics of a specific ILS installation.