all 9c radios have both pcm and ppm modes in their transmitters. It takes about 3 seconds to shift from one mode to the other. the part that is not easy to shift is the reciever. they are built for pcm or ppm and can not be changed. The 9c radios that come with pcm default to pcm mode when you set up a new plane in memory. ppm and pcm are both equally reliable under optimum conditions. If ppm was no good then it would not be on the market. If you are experiencing problems in an area while using ppm then there is no garentee that pcm will fix the problem. It might only be masking a potential failure. It is better to solve the problem by determining the cause of interference and avoiding it by changing frequencies or repairing defective equipment. The pcm provide a higher level of reliability and predictability if you get jammed. What I mean to say is if you are flying a large airplane I beleive it is safer for all concerned that if you get shot down that a pcm failsafe lockout will provide better predictability of where the impact zone will be so that people can get out of its way