Hi QC,
I am fairly certain the 649's are single conversion PCM receivers (I'll have to check). One of these I have used considerably in my petrol powered model, no probs touch wood. I have the fail safe to completely kill the engine.
But the one that killed my patterniship, was the dual conversion. Top of the line. I have had many conflicting stories about single versus dual conversion, I ALWAYS use the dual Hitec for PPM, but have been often told the single conversion in PCM is good. I guess my petrol engine confirms that.
Battery voltage is good, TX battery is good.

I have actually gritted my teeth and just been out flying with the same Tx, but of course a PPM Hitec receiver, no probs.
There was no carbon fibre in the pattern ship, it was all nice and tight, nylon clevis on engine etc, hyde mount. I might add, I was using the same engine in an older pattern plane, but I was using the Hitec 7 channel PPM receiver.

But I go back to, I guess I will never know, except I now have a VERY FLAT R1000DS RX (there was some satisfaction in achieving that) that is now a NO conversion (something it was good at).

But the question still remains.

Why use PCM????????????????????????????????????????????

Sure, I've seen some guys go into fail safe and recover. But if it doesn't even give a glitch, how do you know what is wrong.
Do I know it went into failsafe? Yes!!!!. The engine dropped to idle (which I had set), and everything else was on hold, in this case, I was inverted with a little down elevator, so it basically outside looped (about 3 times) into the ground.
I must say, they were probably the most perfect loops I have NOT performed.