Please excuse if I have double posted, I thought my post hade gone by yesterday but It does not appear in forum.Can anybody tell me what the small fins perpendicular to the fuselage at the Boeing 737 800's tailcone are? As you can see in attached picture they are placed between the vertical and horizontal tailMany thanks,Jonhttp://forums.avsim.net/user_files/163790.jpg

Those are vortex generators. They keep the airflow energized over an aircrafts surface.

I thought that, but vortex generators are used to control the boundary layer and so need only be little stubby things (in comparison), these things are somewhat large (if I'm looking at the right things). Perhaps they are, just not what I would expect from a VG.

Many thanks your anwsers. Never Heard of Vortex Generators, and your anwsers made me able to search on them and learn how they work. Found this very interesting:http://old.smartcockpit.com/operations/Vor...0Generators.PDFYou even have a picture of the same B737 VGs:

My dad said something about the large size needed for the amount of detached flow. He knows that airplane a little more then I do so I'll take his word for it.