You can setup a throttle cut. That's an old transmitter so not sure if you need a mix or its already in the menu.

Gas engines you're best to have an optical ignition kill like the RC Excel and not rely on the transmitter/receiver/servo solely to kill the engine in which case you just install the kill switch in the plane and assign a channel to it.

https://www.valleyviewrc.com/electronics/kill-switches the one with the BEC eliminates the need for a separate ignition battery which is desirable on a plane that size (well any size but especially the smaller ones)