[Aztek1701]

Hi Again,

Hmm, okay, that is an interesting payload. (flying minesweeper? ) If money isnt an problem, then Id suggest a Century predator carbon...

http://www.centuryheli.com/products/...m?currentid=95

or maybe even a predator condor..

http://www.centuryheli.com/products/...?currentid=335

This is NOT a cheap machine though. However, predators are frequently used to lift camera packages and the like so they at a guess they can lift a payload of about 10lbs (the condor has a RATED lift capacity of 15lbs) and an endurance of about 30 minutes.

The smaller of the 2 machines has carbon frames so wont affect your sensor package as much however you might have to consider the interferance from the spark ignition systems. Id also consider getting a helicommand 3A which can mantain a fixed hover position (altitude included.) for you.. http://at.robbe-online.net/rims_at.storefront/en.
Again, not cheap but might help to do what you need.

I would be VERY careful about that 3ft hover altitude because at 3ft the heli will be in ground effect and will be majorly affected by its own rotorwash. Im not saying that its impossible to do but it will be an unpredictable operation. You might also want to think about GPS autopilots (which I THINK exist but are quite rare)

Hope this helps... Good luck with your project

Azzy