Probably already been posted but there is a list of "fixes" [link]http://www.horizonhobby.com/Products/Bulletin.aspx?ProdId=EFLH1100[/link]

Glad to see some old guys like me playing...

Mine did that had to rev it up a little more than average then it would jump 3 feet into the air then act fine... Mine was the center huba nd rotor head not being as smooth as they could... they were binding ever so slightly... the link above has fix but rather than the 15/32 drill bit I used a dremel tool to "polish" the hub and rotor assy. I also coated with silicone grease and it works like a charm now.

But there are about 6 things that can casue that... see the link