| The following question are relevant only to Electric RC planes
This really isn't true ... but I'll answer in the context of electric R/C planes.
| 1. Is there any ARF electric plane currently in market that uses more | than 6 channels?
Here's one -- the Ultra Stick Mini --
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If configured with quad flaps, you'll need seven channels for full functionality, but you can put the flaps on a Y cable and get by with six. (But you'd be giving up full span ailerons, which I guess isn't a big deal.)
Of course, this plane could be configured to work on four channels too. Or even three, if you were willing to give up rudder control, but I wouldn't suggest that.
| 2. Is PCM radio worth for electric flying for weekend fun. Does PCM | radio need expensive or special servos or receiver?
This has already been covered, but PCM isn't used much in electrics, since the new DSP receivers offer many of the benefits for a lot less money and weight.
| 3. When I buy a radio, should I buy receiver / servo / from the same | brand / company?
You don't have to, but it's not a bad policy if you don't know what's compatibile with what. Personally, I have a Futaba 9C TX, and have it talking to receivers from Berg, FMA, Sombra Labs, Hitec and Futaba.
| 4. Will any servo (brand, size, torque) work with any radio / receiver?
Generally, yes. | 5. Can I use a brushed or brushless motor on any type of lipo battery | pack? I'm plannning to buy a lipo that would give me longer fying time | ( > 15 minutes). Does high capacity lipo require special motors?
That's two questions. Yes and no are the answers.
| 6. I'm convinced on a 6 channel futuba / JR / Hitec. Your | recommendation? I will be flying only electric planes / glider / simple | helis in the near future. Should I go for the ones with more channels?
Seven channels will give you even more flexibility, but six isn't bad.
Given that you want to fly electrics and six channels is probably enough, the Spektrum DX6 might be just perfect for you, and the price is right. And you'll never have to worry about channel conflicts with it ...
| 7. Will any ESC work with any receiver / motor?
Two questions again :)
Will it work with any RX -- usually yes.
Will it work with any motor -- no. Brushed motors need brushed ESCs and brushless motors need brushless ESCs. And of cours the ESC needs to be able to support the current draw of the motor, and sometimes there's issues about the timing or frequency of the ESC needing to match the motor (but they're rare.) Getting a ESC and motor as a matched set isn't a bad idea if you don't know the specifics.
| 8. I know what BEC is, but Is this a part of the receiver or something | else?
It's usually part of the ESC, but can be seperate. It's almost never part of the RX.
| 9. What is a synthesizer? Does it mean I can fly my plane at the same | time when someone else is also flying?
Already covered nicely ...