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Old 01-11-2006, 02:26 PM
8iggles is offline
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"I believe I can fly"
Sheffield, United Kingdom
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PCM or PPM

We are just entering into the world of petrol, and everyone seems to run pcm? We were wondering if there is a reason why? Can you run ppm with petrol?

We have only ever run ppm with our glow stuff and we get the occasional glitch, but never had anything serious. For some reason, it's always in the same corner of the field as though we are flying through something.

The only thing that bothers us about PCM is the lock out, How does it work? With the little glitches are you likely to get a lockout?

Is the minimum failsafe device a Kill Switch?

Thanks
Shaun and Ollie
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Old 01-11-2006, 02:37 PM
Kiwi is offline
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Re: PCM or PPM

OK,

There will be a million opinions on this but heres my $ worth.

In a long discussion with Mr Fred Marks of FMA Direct fame he once told me. Kiwi it just comes down to whether you want to crash wings level or in a knife edge dive. The result is the same.

PCM has some fantastic and in my opinion necessary advantages. If nothing else happens PCM will shut the engine down to idle or stop if so programmed. PPM will not do that without an additional gadget installed.

For the throttle cut failsafe alone I will not use PPM.

Of course FMA make a PPM rx with failsafe so in that case my arguement is moot.

Just make sure you have a throttle cut to idle or off with either system and you will be fine. As a good example if you go to the Joe Nall and do not have a throttle fail safe system working then you dont fly!!!!

Kiwi
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Old 01-11-2006, 02:38 PM
Boulder is offline
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Re: PCM or PPM

Hi Fellas,

I use PCM on everything of size and value. You can use PCM on any type of aircraft, gas or glow.

The way I have my fail safe set is all surfaces remain usable, but the throttle goes to idle in the event that there is some radio interference or power glitch. The way to recover from the idle position, which is not really idle but 20% of the throttle curve, is to move your throttle stick to idle and then back up, the throttle will come back giving you notice to land immediately.

The main reason I use PCM isn't the fail safe, it is the additional protection from inadvertant transmitter interference. If you have a PCM receiver on, let's say ch. 40, someone turning on their transmitter would not only have to be on ch. 40, but they would also have to have their transmitter set to PCM mode. This makes it less likely to be hit at the field. I know this doesn't make it impossible to get hit, just less likely.
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Old 01-11-2006, 03:15 PM
Flyboy1958 is offline
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Re: PCM or PPM

Good point, I didn't know that someone on the same ch. had to also be PCM. That's nice to know.
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Old 01-11-2006, 03:22 PM
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Re: PCM or PPM

Hi

I have a very little knowledge about petrol engines and models, but I think, that these engines may cause some problems due to it's ignition system, especially when it's external (the other than magneto).

I may be wrong so please feel free to correct me :]
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Old 01-11-2006, 03:25 PM
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Re: PCM or PPM

Quote:
Originally Posted by Kuba
Hi

I have a very little knowledge about petrol engines and models, but I think, that these engines may cause some problems due to it's ignition system, especially when it's external (the other than magneto).

I may be wrong so please feel free to correct me :]
It's all about the positioning of the receiver in conjunction with the ignition. I don't recall the recommended distance, but I usually make sure my receiver is more than 12" away from the ignition. I have heard it said that some won't use a PCM receiver, they don't see the need.
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Old 01-11-2006, 06:37 PM
8iggles is offline
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"I believe I can fly"
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Re: PCM or PPM

Thanks for the replies, I think we will start with ppm with an additional failsafe on the throttle and see how we go

Are there any devices that cut your ignition in a radio failiure, and that you could asign a switch say if your throttle servo or linkage jammed ?

cheers Shaun
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Old 01-11-2006, 09:21 PM
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Re: PCM or PPM

Quote:
Originally Posted by 8iggles
Thanks for the replies, I think we will start with ppm with an additional failsafe on the throttle and see how we go

Are there any devices that cut your ignition in a radio failiure, and that you could asign a switch say if your throttle servo or linkage jammed ?

cheers Shaun
try this...

http://www.smart-fly.com/Products/Ignition/ignition.htm
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Old 01-27-2006, 01:40 PM
8iggles is offline
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"I believe I can fly"
Sheffield, United Kingdom
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Re: PCM or PPM

I've just been reading about multiplex IPD receivers and they look like you have failsafe but without the permanent lockout as with PCM

Anyone had any experience with these?

http://www.modelspot.com/mpx/mpxfaq.htm

http://www.modelspot.com/mpx/ipd.htm

cheers Shaun
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