I am not sure how he light off the Estes rockets, but I did it by using a extra servo and channel. just made a simple on/off switch with the servo arm to make the connection for the battery/fuse circuit. I used the throttle channel and when I wanted to light off the rocket I just moved the throtle to full and when the servo arem moved forward it made contact with the other end of the wire. The battery I used was the 4.8v receiver battery.

I guess you could also use a landing gear channel for the same thing.

Larry