PCM Receivers - What's the Point?

[Steve]

As I understand it, PCM receivers basically monitor the quality of the incoming signal and make appropriate corrections, and when (if) the quality drops below a certain level, they go into fail-safe mode.

What is the point of this?

If a PPM receiver is getting a poor signal, you get some glitches, which is an excellent indicator that something is not right out there.

If a PCM receiver gets a poor signal, nothing happens (because it is always making adjustments) until all of a sudden it just goes into fail-safe, and the thing drops out of the sky.

When the signal reaches a certain level of poor-ness, the thing just crashes anyway, so what's the point in spending all that extra money on a PCM receiver? I think I'd rather see the twitches and get it down on the ground in one piece for an investigation if possible.

Doesn't PCM stand for Permanent Crash Mode?





...... or am I getting the wrong end of the stick?

[Disc]

Okay,

PCM goes into failsafe mode if theres a radio glitch and you can
set what your Throttle does etc.

So basically some one switchs on while your flying instead of your
heli going madly out of control it just switchs into failsafe.

Far Better than it ploughing uncontrolably into the pits or if your at
a display into a crowd at FULL throttle.

PCM can be set to allow a certain amount of Signal LOSS before it
kicks in.

Look at it like this got a BIG Heli Carbon blades spinning at 18000 rpm
and PPM receiver and some one switchs on and sends the Heli out of
Control..... Now wheres it going to go?

PCM Fail safe kicks in and puts the engine to idle and Blades to 0
degrees. Heli goes in of course but in controled shut down. Won't
go in an unexpected direction unlike PPM.

[Ade_Law]

as disc says. when pcm failsafes its much less likely to kill somebody as you can ensure the amount of energy in the model is decreasing and thats the MAIN point.

there are 2 levels in PCM lock out. first what happens is that it goes to hold mode, it leaves the controls where it last got a proper signal.

if after X time it still hasnt had a proper signal it goes into full failsafe mode and puts the controls to what you last set them to.

once the rx recieves valid data then the it gives back control.

the point at which it goes into the first mode is way beyond where ppm would be a gittering wreck. but also once it goes into failsafe its not game over either.

i used to fly ppm in helis when i first started flying. believe me a partial lock out is far nicer than a glitch. I was doing a fast low tight circle on a 90 size heli when it glitched, it lept about 50ft upwards. this could easily have been 50ft downwards and into the ground at high speed. on a partial lockout it just carries on in the track you left it on.

Ade