When I switch to RTL mode the aircraft turns back to home and begins to circle, but when RTL mode is selected it slowly starts to decend and eventually I have to take over. I have 100 M. selected as my default alt. I have a APM 2.0 with 2.60 firmware and a airspeed sensor enabled. Is there some adjustment to top this from happening? Attached is a tlog.2012-09-07%2022-23-07.tlog
the log you uploaded shows there is no gps fix for the entire log.
Sorry, attached the wrong tlog, here is a new one. The RTL mode are at 27% and 78% approx.