Approximation of pilot operational behavior affecting noise footprint in steep approaches

Landing aircraft create noise that disturbs residents living close to airports. One method to reduce such noise is to fly the final approach at a steeper glide slope than the normal 3.0 glide slope, thus increasing the distance between the source of the noise and the ground. If this is performed, there is a risk that the operational behavior of the pilot counteracts the noise reduction possible to achieve, due to the fact that the pilot must manage the aircraft's speed on a steeper glide slope. For practical reasons, there are few live trials and studies on pilot behavior during steeper approaches. In this project, a method to approximate pilot operational behavior during slightly steeper approaches, using flight data recorder data from standard approaches, was developed. The method exploits the fact that flying an approach in tailwind conditions creates the same operational challenges for a pilot as flying a steeper than normal approach does. The method was applied to 1159 flights. The results indicate that the pilots' operational behavior will change when glide slope angle increases. Extension of final flap and landing gear in steeper approaches will take place at a greater height but closer to the airport than for standard 3.0 ILS approaches. The result can be a reduction of the noise from arriving aircraft by up to 2 dB in some areas beneath the approach path if a 3.5 glide slope angle is used.