jimsoque

My Feedback: (2)

Alright you radio hounds, I need some intel.... Here's the picture. I fly a Stinger 120 full wing, Zenoah G-38, Hitec 615 and 605 servos and 1100mA battery pack. No metal on metal, all ball links or clevis to control horns. The throttle servo is 12.5 inches away from the engine, and again no metal to metal. There are no noise traps in my extensions and only one extension each per servo, the longest is 24 inches for the aileron servos, the others are shorter. At my field Sunday, I had a serious hit with loss of elevator control, and a locked aileron for only seconds of flight, but it was enough for me to ground the plane. Thank god no crash occured. My Transmitter is a Futaba FM Super 7, and Futaba RD 127 Receiver. Ch 12. It took 6 guys to figure out the sutuation, and it was suggested to me, when I fly Gas engine, I must have a PCM Receiver! Radio noise, I was told, is unavoidable. Any thoughts as to the truth of this suggestion?

DMcQuinn

My Feedback: (13)

I do not believe that PCM is required to fly gas. Properly set up, (and it sounds like your setup was fine), you should not see loss of control using a gas engine.
I'd look elsewhere.

R Plante

Are your tail brace wires metal? If they are loose the vibration will give you metal to metal contact and intermitent interference. Learned that one the hard way. I assume you have a resistor plug ? If possible switch plugs. I fly gas with both ppm and pcm rxs no problem with either.

good luck

wgeffon

My Feedback: (4)

PCM is NOT needed to fly gas.
I use PPM with no problems. Make sure all your extensions are heavy duty wire. Smaller diameter extensions can cause voltage loss along the line to the servos.

How was te range check with the motor on and motor off?

SMALLFLY-

My Feedback: (19)

I would check the RX. I have had several 127's and they have a reputation for cracking capacitors after hits and hard landings. Are you using a bosch metal plug cap, that may help as well

drandles

My Feedback: (8)

When I was putting my H9 Taylorcraft (gas) together I was getting some jitter on my servos when I touched a piece of piano wire to the metal servo arm (this was without the engine running). I put in a PCM receiver and did the same test and had no jitters. Some will say you will mask problems by using a PCM receiver- that’s just semantics. My Taylorcraft flies flawlessly – no glitches. So buy a PCM receiver, have fun, and go fly.

On my 1/5 scale Cessna 182 (glow engine) I once in a while would get the ailerons going full tilt for no apparent reason just as you have described. I tried everything from electrical chokes to magnetic chokes, made sure there was no metal to metal contact, and even twisted my servo wires, heavy duty wires, and on and on. None of these methods got rid of the occasional lockups. I was considering buying an optical isolator, but I already thought I had too much money invested in this plane. I sold the Cessna rather than destroy it or put $80 into an optical isolator.

After my experience with the Taylorcraft, I realize I could have avoided problems with the Cessna by using a PCM receiver. Either that or buy the optical isolator. If you’re going to put the money into your plane you might as well buy the PCM receiver. Do you think Jason Shulman risks his planes by using an FM receiver? There’s a reason the big boys use PCM.

I have been flying radio control for 35 years. I will never again risk an expensive model by not using a PCM receiver. Do what you will with yours.



Dale Randles

Rodney

You do not need a PCM receiver to reliably fly gas. I have been flying with only PPM for the last 15 years with no problems using primarily Futaba but also some FMA and one Hitec, all with no problems. If you are getting hit on PPM, you will also get hit on PCM but it is more apt to sneak up on you and bite you hard when you least expect it. Do check out your switch wiring as it is the most probably point of intermittent failure in your aircraft wiring and switches have been known to fail after many hours of vibration like you get from the big gassers. FMA provides a shock mounted heavy duty switch and probably other companies do also, well worth the investment.

sfaust

My Feedback: (11)

PCM will not resolve the problem. Quite the opposite in fact. You need to track down what caused the interference, and resolve it. Don't just drop in a PCM receiver and expect it to fix the problem for you. Those that advise you to do this do not understand how PPM and PCM receivers work, and are in fact giving you very bad advice. PCM will only mask the interference and give you the false sense that everything is alright, yet the interference is still there and will bite you when you least expect it.

From what you stated, it sounds like you did everything correctly with the installation. Check over everything again very carefully. You might find something that changed from the initial flights. Complete a series of range checks (ie, right side, front, left, engine on, etc). You may even find that the interference wasn't from the gas engine at all, but was something external to the airplane. I've done that before after hours and hours of checking for gas engine related interference, only to find the glitching only happened at a specific field (duh).

Half my gassers are PPM and the other half are PCM. They are both very reliable.

Read the following threads for more information on the differences
http://www.rcuniverse.com/showthread...hreadid=473062
http://www.rcuniverse.com/showthread...hreadid=355152
http://www.rcuniverse.com/showthread...hreadid=339931
http://www.rcuniverse.com/showthread...hreadid=246442]

rcflyguy_26

My Feedback: (8)

I fly the rcd 3500 FM and have no trouble! Sunday out flying, we had two other guys get "hit" one lost the aircraft, the other saved it! They both had PCM Receivers! I was told by Pete Waters at KMI that the futaba rec will not last long in gas planes. This may be your problem.

Later, Scott

FLYBOY

My Feedback: (11)

How far is your kill switch from the rec. I had mine in the back cockpit along with the switch for the radio. I had to move the kill switch to the front cockpit and that took care of the problem. They were too close together.

jimsoque

My Feedback: (2)

Gentlemen - It is with great enthusiasm that I wish to thank you for your responses to my dilema. In just 3 short days, many of you have posted superb suggestions, and with your experience to guide me, I hope to have many years with this plane, Sunday being only her second day out.
FLYBOY -I knew about the killswitch issue, and mine is on the firewall, starboard side, 24" from the receiver, the battery at the CG, receiver is behind the cockpit, foam padded, antenna is down the fuse shaft and out the tail end.
RP- I use 60 lb steel wrapped in plastic fishing line, barrel crimps, metal landing gear straps, anchored with 2-56 hardware through the tail surfaces. I was thinking of switching to the Plastic landing gear straps for brace material- perhaps this is the key.
WG- I'll get some heavy duty extensions, thanks. I never thought about the voltage loss with 6 servos, and only an 1100 mAmp batt pack. The range check with morot on at 100 feet was perfect.
SF+RC26- The 127 has ad a great life- maybe it's time for a new, and Hitec is a good offering these days, don't know about PPM or PCM yet. I'll have to try the bosch metal plug cap as well.
DRAN- There is one other source of metal to metal contact that is hard to avoid. I use 4-40 Dubro ball link-set up, with 4-40 hdw on heavy duty servo arms on 6 points, ailerons, elevators, and rudder pull/pull. I like the idea of purchasig a PCM receiver in addition to the other points of concern from our fliers. Perhaps I should dump the Ball links and just go with simple Z-bends! Although, in some instances, this is hard to do.
ROD - A friend gave me a heavy duty switch to try, going back to the shop soon.
SFAUST- I'll recheck all my connections, and change to heavier duty connectors as you suggested. As far as the other, my glitches occured at the Northwest most corner of our field, three times on a given day. You may have a point there.
With many thanks to my contributors,
Sincerely,
Jim Soque

Jim D

My Feedback: (8)

My first gasser was (is) a Stinger 120 / G38. I fly it using a JR 8103 on FM (PPM) with a Hitec Supreme 3600 Receiver. I get full throttle range checks over 100 ft with the antennae collapsed and the radio pointed straight at the plane.

There are lots of problems that can cause radio issues, most of which the previous posters have covered. Using FM (PPM) with gas is not one of them.

Ch0pp3r

My Feedback: (3)

I am an electrical engineer. I am also an RC pilot like you guys and share the same experiences. I have flown gas motors on FM for 15 years. I have yet to have a radio interference problem that had an unknown cause. My 2 cents worth is as follows.
You have checked all the obvious things and if you did this properly you can check those off the list. I would then guess that the transmitter and/or the receiver are out of tune. It happens all the time. I have worked on radio gear for 25 years. The parts age and the frequency tuning change over time. Improper vibration osolation will also cause this. So will dropping transmitters and receivers or possibly a rough car ride while not in a transmitter case. This I guarantee. It does not matter weather you have Futaba or JR or anything else. If you try a known good transmitter and receiver combo in the plane I would guess that your troubles will go away. If not then go back to step one, because you missed something. Once you osolate the problem to your transmitter and/or receiver combo, send them both to a qualified shop or to the manufacturer to be tuned properly. You will get back radio gear that is like new. I have tested my gear myself and when I find a propblem have sent gear back to Futaba. I have always been pleased with the results.

It is also possible that you have a frequency specific problem related to outside influences. You have to have a spectrum analyzer to solve that type of problem. No radio equipment can be expected to reject somebody else transmitting on the same frequency. Pager companies, cell phones and HAM people do it all the time. FM will show hits and irratic behavour. PCM might fly a little while then go to a total loss situation.

Just my 2 cents. I hope you find it useful.

Chuck

RCPilot100

My Feedback: (4)

I would suspect the Rx. It seems you have everything else the way it should be, so the obvious next thing is the Rx. I had one repaired about a year ago after a crash due to some idiot turning on the same freq. It needed a new antenna wire and a check out. My radio guy said that the Rx needed several parts because they regulary go bad on this particular Rx due to vibration. It is repaired now but I am hesitant to use it. After asking around, he was right, others seem to have mysterious problems with it over time.

Dan