A friend of mine gave me his Phoenix Sukhoi SU-31.46 as a starter airplane. But it HAD a gas engine, and he and I want to convert it to electric. My question is: What size electric motor do I need to get this 6-pound airplane into the air? What size and pitch of prop would work best? I have a 450-class electric helicopter, but am sure that nothing is large enough for this thing! Anybody have any suggestions?

http://www3.towerhobbies.com/cgi-bin...?&I=LXMHP5&P=7

i have a 35-30-1250 and it works great
your going to need some lipo's (id go with 4's or 5's)
get them at hobbycity.com the cheapest place around, shipping is about 20 bucks, ems in 1 week, others in 3 weeks (if you cant wait)

as for the esc, could get a gp silver series (i have the 25amp one for my motor), they work well
or you could get one from hobbycity.com (much cheaper, work fine)

I know this isn't answering your question but is that going to be your first airplane? If so, do yourself a favor and put it away and start out with something else. A Sukhoi is not a good first airplane even if you have heli experience.

As for converting, go to www.electrifly.com or www.e-fliterc.com, both will have guidelines for picking the right motor and speed controller.