If you are using all the channels, yes. An optical kill, or a choke servo, either require a dedicated channel available. You have to have individual on/off control like a gear switch, or something like that.

If you have a 50cc gasser, one servo per surface, that's 5 plus throttle is 6, so "kill (or choke)" could be the seventh channel.

I think many DX 7 users probably put the kill on the Gear channel; that's what I did when I was using the DX 7 way back.