HAP-alpha: Development of System Identification Manoeuvres for Low-Altitude Flight Testing of a Flexible High-Altitude Platform

Kurzfassung

This paper deals with the development of flight test manoeuvres that are defined for low-altitude flight testing of high-altitude platforms (HAP). Due to such aircraft's particularities, typical system identification manoeuvres are not always applicable and need to be adjusted. In addition, novel manoeuvres are defined. The results show that classical doublet manoeuvres are applicable when the time units are increased and/or comparatively strong control inputs are applied. A 13211-pitch manoeuvre is used instead of the better-known 3211 to limit airspeed excursions and a 121-bank input is used in lieu of a bank-to-bank manoeuvre. Frequency sweeps using aileron, stabiliser or rudder yield sufficient excitations of the structural modes and rudder doublets are the most critical with respect to loads. A final exemplary system identification test shows the general feasibility of the manoeuvres for obtaining adequate aircraft parameters. The work presented in this paper is conducted within the project HAP-alpha, in which the German Aerospace Center (DLR) is developing a flexible, solar-powered, fixed-wing HAP. In the project, an extensive low-altitude flight test campaign is planned, which will include dedicated test manoeuvres aimed at model validation and system identification.