markturner1960

Actually, both answers very helpful, thanks - i should have clarified in the OP, I had only left the boat for 20 minutes, so it was not a question of the S3 running out of loiter time or fuel, 4 hours is way more than I would need for any mission I make. So Zylls linke dvideo will probably show what I did wrong, however, I am still keen to understand the workings of the script......
 
Thanks guys.