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Is PCM needed for gas plane?

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Old 05-19-2003, 08:14 PM
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Paul Cataldo
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Default Is PCM needed for gas plane?

Guys,
I have read a lot about interference when converting to a gas engine. Is this something I should EXPECT, or are there a lot of you guys out there flying gas with standard FM receivers?
I am about to set up my first gas plane, and would like to know if I need to be prepared to spend an extra $100 on a Futaba PCM receiver for my 9C.
Thanks fellas.
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Old 05-19-2003, 08:26 PM
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Default Is PCM needed for gas plane?

I have flown gas with FM. Never had a problem. I would personally rather have a PCM in a gas bird, but that is just my preferance. I fly PCM an almost everything now. Have been for years. Just a personal preference though.
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Old 05-19-2003, 08:45 PM
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Default Is PCM needed for gas plane?

Gas/ignition engines existed long before PCM with very few problems. Those who have had problems could usually track the cause to a non resistor plug or poor contact somewhere in the ignition system or kill switch.

John
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Old 05-19-2003, 09:49 PM
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Default Is PCM needed for gas plane?

No - PCM is not REQUIRED for gas engines. as John said, gas has been around long before PCM was available. Even AM was used before FM was available.

If you do use PCM, it is still important to eliminate any interference inherant in the plane, rather than letting PCM "hide" the problem. Use standard PPM to diagnose, then upgrade to PCM if desired.
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Old 05-20-2003, 01:55 PM
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Default Is PCM needed for gas plane?

Although I do use PCM in my current gasser heli, I still use AM in my gasser boat and last gasser heli was FM with no problems at all.
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Old 05-20-2003, 03:50 PM
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Default Is PCM needed for gas plane?

Paul - I forgot to mention in my previous post that it is important with all tyes of receivers to maintain complete electrical seperation between the engine and the radio system. Preferably 10 inches or more. Also, do not use conductive materials for your throttle pushrod, and use a nylon connector. Vibration of metal on metal ANYWHERE on the plane can cause interference.

Some people have put their radios right next to the engine with no ill effects, but it is not recommended.

My only gasser is using FM-PPM with 14 inches of seperation and ground based range tests (engine running) are consistantly at or near 50 paces. 1-2 paces less than when the engine is off.

Futaba recommends using FM-PPM for gassers (click here) during setup, then switching to PCM after all interference has been removed.
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Old 05-20-2003, 09:14 PM
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Default Is PCM needed for gas plane?

strato is very correct there. I should have also mentioned that. I had the kill switch in the rear cockpit with the radio switch. Kept sending the radio into failsafe. Moved the kill switch to the front cockpit and have not had the trouble any more. Keep them apart.
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