In all the simulator tests we conducted, the aircraft begins a turn shortly after fuel exhaustion. The turn evolves into a very steep spiral descent with bank angles close to 90 degrees in some cases. Phugoids were also observed. Speeds over the 500 KIAS (instrument display limit) were observed. Those were "indicated", not true. True airspeed was probaly close to Mach 1 in some cases observed (off the chart).