Stall Testing on a Transport Category Airplane

Martina Hierle, German Aerospace Center, DLR, Weßling, Germany
Steffen Gemsa, German Aerospace Center, DLR, Weßling, Germany

Abstract

DLR´s new atmospheric research aircraft HALO is based on one of the most advanced busi-ness aviation airplanes: The Gulfstream G550. Equipped with a fully integrated EFIS cockpit that uses multiple sensor systems to provided excessive information to the flight crew, the airplane is capable of flying up to 6750nm in range and up to 51000ft in altitude.

DLR designed and developed a variety of external modifications to carry or support scientific equipment. During flight test of those modifications DLR´s Flight Experiments had to face the fact, that these changes on the airplane had the potential to interfere with the air data sensor system and therefore question the performance of the whole system.

DLR went into flight test in a very careful and built up procedure, to assess the performance and the potential weak-nesses of the unmodified airplane systems and then – step by step – develop more challeng-ing flight test efforts. Stores on the forward fuselage, pods under the airplane’s wings and multiple air inlet probes were tested excessively. It turned out that the so called Belly Pod under the forward fuselage was the most critical modification and interferes with the air data system in fact. Higher stick pusher speeds were observed in the flight test campaign potentially changing the take-off speed schedule and performance of the airplane.

Finally it could be demonstrated that the airplane was not limited by the stall speed but by the single engine maneuverability, producing a speed margin big enough to cope with the increased stick pusher speeds.