On giving Aerostar Endorsements I get a clearance up to 8000 ft over Richmond and tell the student at 148 kts to roll into a steep turn and pull back to the stall and it will suddenly (within a second) flick upside down and go verticall and it usually then takes him several thousand feet to pull out. they will then usually say I didn’t know an aeroplane would do that no one has ever shown that to me before.