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Radio Ruminations

Currently there are three 'price points' in the heli radio market. In the $200-$250 range, you have the six-channel Futaba 6X, JR 622 (or is it the 642?), and Airtronics RD6000. In the $400-$600 range, you have the eight-channel Futaba "Super Eight" and the JR 8103. In the just-over-$1000 range, you have the nine- and ten-channel Futaba 9Z and JR 10X, respectively.

I can't say much about the 6-channel radios as I have little experience with them. Suffice to say that they will do all you need for hovering, forward flight, and basic (airplane-style) aerobatics. The JR is somewhatever preferable to the Futaba in my humble opinion. The Airtronics appears superior to both in most ways, but I haven't seen one yet so I can't say for sure.

The 8-channel radios will do everything you need, ever. When I got into this, I assumed that if I stuck with it for a while and "got serious," I would upgrade to one of the $1000+ systems, but here I am four years later with three helicopters and nine plaques from various contests, and I have yet to feel limited by my radio. I might get a 9Z if I find a great deal on one, but I'm in no hurry.

The 'flagship' 9Z and 10X will do everything you need, and then some. If you really want one, go for it. If you're wondering if you need one, you probably don't. Most folks I know who use these radios have most of the advanced features disabled, making me wonder why they didn't stick with an 8-channel system and pocket the extra $500-$600 they spent on unused p-mixes and disabled flight modes.

RCD/Hitec makes radios that cost significantly less; I want to believe that they are indeed a better deal, but I've been burned in the past when buying less expensive equipment (car stereo quipment, for example). Sad, but true. Maybe if I knew some folks with RCD gear I wouldn't be so cynical?

See this page for a quick overview of the PCM vs PPM (aka FM) tradeoffs.

Setup Suggestions

For a while when I was using non-heading-hold gyros, I moved Gyro sensitivity to channel 7 which uses a 3-position switch on the front of the transmitter. In the bottom position, the gyro is set to low gain for pirouettes and the like; in the top position, it's set to high gain for hovering; in the middle position, it activates a rudder-to-gyro programmable mix which allows for fast pirouettes and 540 - 900 - 1080+ stall turns.

I have also been using channel 8 to control the gyro gain. This is really handy when dialing in a new piezo for the first few flights, since you can tweak the gain quickly using the knob on the front of the transmitter.

The 8U transmitter includes a pair of dedicated 5-point mixers originally intended for control of a remote needle valve. The master 'channel' is the throttle stick position, the slave is channel 8, and there are separate curves for normal and idle-up flight modes. If you hook up your gyro gain to channel 8, you can have a high gain in hover, and a slightly reduced gain in idle up to keep it from wagging in fast forward flight. That makes for one less switch to flip while keeping the highest possible gain at all times, which appeals to me. For more detail, see this web page.

The 8U allows you to assign dual rate functions to different switches, so I put both aileron and elevator rates on the "A" switch (rather than A and D). This allows me to adjust the entire cyclic response at once, which suits the way I think of things. This also frees up the "D" switch for other things...

If you've given your helicopter a new engine, or new blades, you might be wondering how much pitch is appropriate. If you have a spare p-mix, you can set up something 'dual rates' for your collective. This lets you try two different pitch ranges in each of the flight modes, which I find helpful when evaluating pitch <-> RPM tradeoffs.

PMIX-2:
Channels: PIT -> PIT
Percentages: +20 / +20 (for starters, use more or less as you please)
Turn off all the mixing options; link off, etc
Assign the mix to switch D

When you're satisfied with a pitch range, it's probably best to either disable the mix and set the ATVs to give you the range you want, or set things up so that the 'low' rate is what you fly with 90% of the time and the 'high' rate is just extra pitch for drag racing or whatever.

In my opinion, flying around on 'high' rates is somewhere between a potential annoyance and a potential disaster. The other day I was wondering why my heli wasn't performing, and it turned out I had the collective on the 'low' rate... annoying. Had I starting doing low tumbles at the start of a flight, it might have been enough to cause a crash. On the other hand, if you normally use 'low' rates and accidentally hit 'high' rates, you'll be more reponsive and thus more able to recover from the surprise.

Flight Packs

For my first heli - Kyosho Concept SRX - the standard S3001 servos included with the Futaba 8UHF system were sufficient. With one ball bearing, a speed of .22 seconds and 37 oz/in torque, they are run-of-the-mill servos. For a beginner-s 30-size helicopter, they're adequate. The tail rotor servo was the first to be upgraded, as a JR 2700G took its place. This set of servos performed well, even in an Expert fun-fly contest in which I took 3rd place and in freestyle contest in which I took 3rd and 2nd places.

After 3 years of continued (ab)use, one of the S3001s failed in flight, so I retired the whole set. So, if you're learning with S3001s or servos of that caliber, don't feel like you have to upgrade them to get good performance. They work. But relegate them to an RC car or something less dangerous after three years or so, OK?

When I bought my Futura SE, I put in what I thought would the 'best of breed' for each servo. If you don't see your current favorite servo listed here, that's because this was in 1996...

Collective: JR 4000
Cyclics: Futaba 9202
Rudder: Futaba 9203
Throttle: Futaba 9403

In retrospect... I have a JR 2700G rudder servo in my Concept, I think it might be a little faster than the 9203. Not by much though - some experiementation is in order here. I doubt the difference is all that great. 2700 and 9203 are both great rudder servos. Airtronics has one of the same caliber, but I haven't tried it. It's part number 987654321 or something like that.

Where do these people come up with their servo part numbers? Airtronics especially. What is it, the telephone number (or extension) of the engineer who developed the servo?

Anyhow, I figured the 9403 would make a great throttle servo since it's pretty fast (.16 or .17 if I recall correctly) with medium torque (just under 40 oz/in). The throttle requires the least work (or torque) of any of the servos, so 40 oz/in is plenty. The high speed should make it a good match for the GV-1 governor. Seems to work quite well!

The JR 4000 is a remarkable servo. Fast and strong. I can't imagine a better servo for collective. You may have read the ads where they talk about trying to twist a servo arm while the radio system is turned on - they claim that regular servos feel kinda squishy but the JR 4000 feels like the gears are locked... It sounded bogus to me, but they're right. If money's no object, they probably would make for great cyclic servos as well. I might even try one on the throttle with the GV-1, I don't know.

So far I have no complaints about the performance of any of the servos. The Futura flies wonderfully, so I'm not really in a hurry to change anything.