Did as The Frog suggested and lo and behold got them to start. The fly in the ointment is you apparently MUST go to the default Cessna first, you can't just go to the airport you want with the 212 loaded. This means landing and shutting down the engines for whatever reasons, then restarting them and completing the flight, is OUT. Second thing I discovered is if you look closely at the 172's panel and floorboard, on the floorboard to the right of centerline is a small red handle on a push-pull rod going in and out of the firewall. This the fuel cutoff. I made SURE that was pulled out, opening the master fuel valve. Next thing to do was cycle the 172's fuel tank lever below the inst. panel to l/r/back to center, where draw was labeled "all." Last thing to do was push the mixture right into the firewall using the keyboard setting for "full rich." I then was able to start the engines per your instructions. That's great, and I greatly appreciate your assistance, since this is an excellent helo sim once you get everything working. I took a test hop and landed right away, then shut down and attempted a restart. No go. I still apparently have to go back to the default aircraft, set everything up as described above, then stop everything and load the 212. Still pretty disappointing. I did change my keyboard mapping to set certain keys to open the fuel valves for engines 1 and 2 using the "F+1" and "F+2" keys, am using "F+A" to open all fuel valves for all engines - which should equate with the fuel cutoff for the C-172 as described above. Unfortunately that did not have the desired effect, even though I set the mixture to full rich in the 212 using the keyboard keys, plus set up the individual throttles on the collective. I haven't shut down the sim then restarted yet, maybe you have to do that to make the new selections be registered by the sim. I'll give that a try and see what happens.