Is PCM a necessity?
07-18-2002, 12:57 AM
#1
Is PCM a necessity?
This thing's probably been beaten to death before but I don't know, maybe it's time to bring it up again.
Today I went to pick up my 30% Carden Extra which I had retrofitted with a ZDZ 60 and canister muffler, a quiet setup previously impossible until the release of the new small ZDZ canisters. The gentleman who did the work normally has three airplanes in his garage: three Carden CAP 232's; 30, 35, and 40 percent. I happened to notice the 30 percenter wasn't in there. "Where's your 30% CAP Fred", I said. "The 30% is no more!" he replied.
"What happened?"
"PCM lock."
"Whaddya mean?"
"Well, I was letting my buddy fly the plane. He lined it for a pass and as it came toward us he yelled 'I got nothin!' so I grabbed the box and he was right. Nothing. Absolutely nothing. It's the worst kind of crash you can possibly have because you just sit there and watch the plane go in. I had no control whatsoever. There was nothing I could do. I hate PCM!"
What's the deal? I've got a half dozen plain old PPM receivers, one Futaba and the rest FMA Fortress/ Quantum in everything from a 1/4 scale CAP to a hyper-fast Diamond Dust and all have been flawless. Never, ever a glitch!
Why the PCM? Sounds like when one of those locks up you are screwed, plain and simple!
Any comnments?
Today I went to pick up my 30% Carden Extra which I had retrofitted with a ZDZ 60 and canister muffler, a quiet setup previously impossible until the release of the new small ZDZ canisters. The gentleman who did the work normally has three airplanes in his garage: three Carden CAP 232's; 30, 35, and 40 percent. I happened to notice the 30 percenter wasn't in there. "Where's your 30% CAP Fred", I said. "The 30% is no more!" he replied.
"What happened?"
"PCM lock."
"Whaddya mean?"
"Well, I was letting my buddy fly the plane. He lined it for a pass and as it came toward us he yelled 'I got nothin!' so I grabbed the box and he was right. Nothing. Absolutely nothing. It's the worst kind of crash you can possibly have because you just sit there and watch the plane go in. I had no control whatsoever. There was nothing I could do. I hate PCM!"
What's the deal? I've got a half dozen plain old PPM receivers, one Futaba and the rest FMA Fortress/ Quantum in everything from a 1/4 scale CAP to a hyper-fast Diamond Dust and all have been flawless. Never, ever a glitch!
Why the PCM? Sounds like when one of those locks up you are screwed, plain and simple!
Any comnments?
07-18-2002, 03:32 AM
#2
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Is PCM a necessity?
Simply because the model did not respond does not mean it was a PCM lockout.
DId anything change when the model stopped reacting, i.e. did the throttle position change?
Did the post mortum reveal any information? was the battery up, switch good, RX functioning, crystal in place and such?
What radio system does your friend use?
Generally speaking PCM has the capability to pro-actively move any given control surface or servo to a pre-set parameter. This would be a significant clue as to a PCM lockout. Some pilots never set there parameters, so whatever the radio system is factory preprogrammed to do, is set to task.
PCM is regarded by all the top TOC competitors and other professionals in the field as the best of the best... Where money is no object.
PCM provides various improvements, refinements, RF interference rejection and model control verses FM/PPM...
And yes it's been covered many many times. Do a search, you'll find a wealth of information.
DId anything change when the model stopped reacting, i.e. did the throttle position change?
Did the post mortum reveal any information? was the battery up, switch good, RX functioning, crystal in place and such?
What radio system does your friend use?
Generally speaking PCM has the capability to pro-actively move any given control surface or servo to a pre-set parameter. This would be a significant clue as to a PCM lockout. Some pilots never set there parameters, so whatever the radio system is factory preprogrammed to do, is set to task.
PCM is regarded by all the top TOC competitors and other professionals in the field as the best of the best... Where money is no object.
PCM provides various improvements, refinements, RF interference rejection and model control verses FM/PPM...
And yes it's been covered many many times. Do a search, you'll find a wealth of information.
07-18-2002, 03:43 AM
#3
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PCM
Hi
He had to have something else wrong or when he set up the Cap, he had a problem and the PCM was just masking the problem. A problem can occur in any system PCM or PPM. I fly both, have not had any trouble with PCM "yet" but I do not have as much flight time on PCM as PPM. Two years ago I had a new giant scale bird with a new PPM RX. on the 8th flight I lost all control and after a short flight on its own it left a 30' trail of wreckage.
Charles
He had to have something else wrong or when he set up the Cap, he had a problem and the PCM was just masking the problem. A problem can occur in any system PCM or PPM. I fly both, have not had any trouble with PCM "yet" but I do not have as much flight time on PCM as PPM. Two years ago I had a new giant scale bird with a new PPM RX. on the 8th flight I lost all control and after a short flight on its own it left a 30' trail of wreckage.
Charles
07-18-2002, 04:07 AM
#4
Is PCM a necessity?
I had same problem with an FM/PPM system. All due respect here, I didn't call it PPM lockout. I lost all control of the aircraft, totally, nothing, nada. Watched it collide with mother earth, watching helplessly, and turned back into toothpicks.
Tech inspection though will tell you alot. The system worked immediately following the accident, and seemed OK. Being in the hobby forever though, knowing it had to be inspected after that hard of impact(or any impact for that matter), I sent receiver in for inspection. There was some sort of filter component that went south. Would have never known though without sending it in. Part was $3, labor $15. Done with no further problem, this was 3yrs ago, and receiver still working flawlessly.
Point is....it could be any system that looses signal for any number of reasons. Without inspection it's hard to say what it was. Was there an inspection done?
I'm very comfy with todays systems really. PCM or PPM/FM.
Again all due respect, but "lockout" really means.....
..."something happened and I have no idea what it was."
I wouldnt worry about PCM any more then I would worry about FM though. This is just my opinion, and definately not meant to offend anyone.
Tech inspection though will tell you alot. The system worked immediately following the accident, and seemed OK. Being in the hobby forever though, knowing it had to be inspected after that hard of impact(or any impact for that matter), I sent receiver in for inspection. There was some sort of filter component that went south. Would have never known though without sending it in. Part was $3, labor $15. Done with no further problem, this was 3yrs ago, and receiver still working flawlessly.
Point is....it could be any system that looses signal for any number of reasons. Without inspection it's hard to say what it was. Was there an inspection done?
I'm very comfy with todays systems really. PCM or PPM/FM.
Again all due respect, but "lockout" really means.....
..."something happened and I have no idea what it was."
I wouldnt worry about PCM any more then I would worry about FM though. This is just my opinion, and definately not meant to offend anyone.
07-18-2002, 09:36 AM
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Is PCM a necessity?
Most people program one or more channels on their planes to go to a particular position. Did he have his fail safe set to idle the engine with signal loss?
If he didn't have any control with PCM, I would doubt that he would have any with FM. Also, if he has Futaba equipment and he considers the receiver junk, he can toss it my way!
If he didn't have any control with PCM, I would doubt that he would have any with FM. Also, if he has Futaba equipment and he considers the receiver junk, he can toss it my way!
07-18-2002, 01:41 PM
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PCM is better
If he had a PCM lockout, then the throttle if he programmed it as everyone does would have gone to idle when he had no control. It sounds like the plane kept flying with no throttle chance, so, either it wasn't a pcm lockout or he didn't program it.
PCM doesn't hide issues as people seem to think, in fact it tells you about them. When you set your throttle to go to idle, if you have a radio issue, the throttle will drop and come back, and then you know you are "getting hit" as they call it. Basically you are losing the signal, for one reason or another, and, if gives you a chance to land and try to solve the problem by rerouting wires or looking for noise issues.
With FM, instead of just a throttle cut, the plane goes crazy and jumps all over the sky as the servos frantically jitter, and, it scares the heck out of you. FM is not as good as PCM (trust me), and, in some cases it can't recover from this and you might end up crashing (or you could be low and just slammed into the ground unexpectedly). PCM is much more favorable, and, it has saved me many times by clueing me in on reception issues.
PCM never locks up forever, its usually a split second unless there is some serious interferance like someone on your channel. If he locked up forever, its possible the battery got unplugged, and, hence no response at all and no throttling back to idle to indicate a lockout, provided he programmed it to do so.
Just my 2 cents worth....
-=>Raja.
PCM doesn't hide issues as people seem to think, in fact it tells you about them. When you set your throttle to go to idle, if you have a radio issue, the throttle will drop and come back, and then you know you are "getting hit" as they call it. Basically you are losing the signal, for one reason or another, and, if gives you a chance to land and try to solve the problem by rerouting wires or looking for noise issues.
With FM, instead of just a throttle cut, the plane goes crazy and jumps all over the sky as the servos frantically jitter, and, it scares the heck out of you. FM is not as good as PCM (trust me), and, in some cases it can't recover from this and you might end up crashing (or you could be low and just slammed into the ground unexpectedly). PCM is much more favorable, and, it has saved me many times by clueing me in on reception issues.
PCM never locks up forever, its usually a split second unless there is some serious interferance like someone on your channel. If he locked up forever, its possible the battery got unplugged, and, hence no response at all and no throttling back to idle to indicate a lockout, provided he programmed it to do so.
Just my 2 cents worth....
-=>Raja.
07-18-2002, 07:43 PM
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PCM?
I'd have to agree with the previous several posts. With the description given either it was NOT PCM lockout, or it was PCM failsafe becasue of a very serious hit such as another TX on. Sounds to me like a RX failure or RX powered off. I'd look for loose connections, bad RX (send it in and have it checked), etc.
Is PCM required, necessary, etc. IMO the anwser is No, but it sure is nice... I only run PCM. This issue was beat to death (PPM vs PCM vs IPD) a couple of months ago. Just search for PPM, PCM, IPD in the radio forum.
Real sorry to hear about the plane. I'm sure it was a nice flier. I'd probably go home and cry if I put any of my Cardens in that hard.
Is PCM required, necessary, etc. IMO the anwser is No, but it sure is nice... I only run PCM. This issue was beat to death (PPM vs PCM vs IPD) a couple of months ago. Just search for PPM, PCM, IPD in the radio forum.
Real sorry to hear about the plane. I'm sure it was a nice flier. I'd probably go home and cry if I put any of my Cardens in that hard.
07-19-2002, 11:28 PM
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Is PCM a necessity?
Not knowing what TX & RX were used in the situation you described, Sounds like same problem I had in a Ohio Ultimate using a Futaba 7 UAF Super TX and a Pcm 1024 129 DP RX,.3.2 Walker engine.I would be flying and all of a sudden no control and then few seconds latter I could regain control,After a few times of that I sent Radio off to Futaba for check up.Received system back saying no problems were found,By then it was winter ,Going on internet and going to Futaba FAQ I ran across a situation same as mine, It says that sometimes a 7 ch TX can't talk to a 129 DP RX unless the RX has been updated.In FAQ it will tell you what to look for, I took my RX top off and sure enough after sending it in they missed doing the update, If I hadn't caught it I would probably put the plane in. Guess it pays to check,
