If you are going to the US for more than 18 hours of study (flight and ground training)per week and it is the primary reason for visiting, then you will require a visa. If not, then according to the rules you don't even qualify for one.
My suggestion would be that if you are in doubt, instead of listening to advice on a forum, or trying to search through the stupid number of immigration websites, call your embassy. If will be a lot cheaper than wasting $200 of flying money. Call the information line and tell them you're visiting for tourism, but want to do a short course of study, 5(?) hours total for a night rating, and ask them if you need a visa. You stand a better chance of getting an accurate answer, although given my experiences with immigration, no guarantees!