coindex

I am in the process of building an Extra 300S 60series and trying to decide whether or not I should use my JR PCM synthesized 10ch receiver or my airtronics 6ch ppm receiver.
My last extra 300 I had crashed and I was using my pcm receiver at the time. Crash still unknown why. I've checked the receiver all over, range tested it on my servos and everything works fine same with the PPM.
So, should I go with the PCM or the PPM receiver. My trnasmitter im using is the 7202 JR which does have failsafe features for the PCM mode.


2) Second question is if I do go with the PCM receiver, what should I set my failsafes at? The following is what i'm thinking:

1. elevator - 25 - 30% up so the nose doesn't dive into the ground on decent
2. rudder - neutral position so it hopefully doens't go into a flat spin
3. aelerons - neutral to keep plane at level flight
4. throttle - low idle (if it doesn't stall out or engine still has power)

does this sound fairly good?

MR G

Coindex,

I have recently spent some time researching this exact subject (PPM vs PCM). My personal opinion is the PCM has more reliability due to the checks done on recieved data packets from the TX prior to executing the TX commands, while PPM just executes the commands as the RX interprets irregardless of what the commands are( no validity check is performed in PPM).

There is more to it than what is stated above but thats the jist of it. With that being said, I still use PPM, just not in my big birds(Gassers). It is best to do a proper range check without and with the engine running before taking off!! If you get a good range check I don't think it will matter whether you are using PPM or PCM.

I believe the best failsafe settings are to hold the last settings for all control sufaces, except for throttle it should be set to go to 10% - 20% throttle(flight idle). Reason being is that you are never sure when failsafe will kick in. If you are in an inverted pass, your current failsafe settings will spell doom for your plane.

MR G

altavillan

My Feedback: (1)

Do a stress test on your servos too. Plug all the crashed servos into the rx, turn everything on and one at a time hold the servo arm from moving freely. Don't stop it completely just put a strong load on it. A load equal to how much torque your servo needs to move it's flight control surface. See if one looses power real quick. The motors will work just fine when cool but make them work and warm up they might be week.
It's a good thing to stress check servos this way as an occasional preflight test.

daven

My Feedback: (1)

I have used both in many applications. For overall reliability, I have had better luck with PCM receivers.

Many would argue that failsafe is to protect spectators, not to save the plane. Many set their failsafe to zero throttle, and max deflection on surfaces so it will tumble to the ground.

TFF

If the plane was a 60 size plane I doubt it was a receiver problem as long as it was in good shape and installed right unless you fly in a known high RF area; if you think so the PCM is masking the problem and what will happen is it will go failsafe. Failsafe does not mean it wont crash it is just a tool to try to save your plane in a bad situation. I have both kinds but most are PPM. My PCMs are in biplanes with metal flying wires and they are necessary there.

MR G

Dave,

I don't agree with failsafe settings to put the aircraft in a tumble toward the ground. Be aware that a falisafe status may only be a momentary thing. And without the ability to know when the failsafe will occur also means you cannot know the attitude of the aircraft whe failsafe kicks in. For this reason I believe it is best to hold all control surfaces and bring the engine to idle.

I agree that the safety of the spectators and other fliers are paramount and would rather totally destroy an airplane in the middle of an empty field than risk hurting anyone.

MR G

BuschBarber

My Feedback: (2)

There are those who would rather Fight the plane to the ground than stand helpless with it locked out. I think the most important channel is the Throttle, as this, more than anything else, determines how long an affected aircraft will stay in the air, uncontrolled. I think Hold is the best Failsafe setting for all other channels unless you have a sailplane or some other light, unpowered aircraft where you want it just to fly a shallow circle rather than flying off into the horizon. Most of the time, a Failsafe event is just for a second or two.

I have used PPM and PCM receivers. I can't say I have had any fewer Interference issues with PCM than with PPM.

cap10b

Use PPM to test fly and get the bugs out and then when your happy switch to PCM. Works for me. Better yet switch to PPM on 2.4

jds