Evaluation of Landing Procedures for a High-Altitude Platform with Skid-Type Landing Gear Based on Pilot-in-the-Loop Simulations

In the context of the project HAP, the German Aerospace Center (DLR) is currently developing a solar-powered high-altitude platform. The underlying vehicle is a fixed-wing aircraft that is supposed to be stationed in the stratosphere for 30 days. Due to, among others, low achievable rates of descent, the use of skids as landing gear and its high susceptibility to wind, landing this aircraft is a very challenging task. Hence, it requires a landing procedure, which is specifically tailored to the aircraft's particularities. In addition, this procedure needs to be relatively easy to follow by pilots especially in adverse atmospheric conditions. This paper deals with a pilot-in-the-loop simulation campaign that is conducted in order to assess a landing procedure which has been developed for the high-altitude platform in earlier works. Within this campaign, the pilots are supposed to land the aircraft following this specifically developed procedure in atmospheric turbulence conditions. In addition, they also land the aircraft following a reference procedure, which is based on a conventional landing. In doing so, the altitude at which a flare is performed and/or the propellers are shut down is varied. Finally, the novel procedure's overall feasibility from a piloting point of view and its potential to reduce the risks during landing are assessed. The results show that the developed procedure proves to reduce the risk of inadvertent ground contact of the aircraft payload compartment, which is associated with serious damage to aircraft structure and payload. However, since the novel procedure is challenging for the pilots, some improvements to the procedure are proposed to make it easier to follow