Hi Deathwish
Thanks for your reply. I found this on eBay at rc-sub-workshop (H.K) to explain how to use the pump to compress air, as you said.
and maybe an electric flight esc, with failsafe on the throttle channel, could open the valve when radio contact was lost...
http://www.youtube.com/watch?v=Oey7q...layer_embedded
Regards
Chris