Where can I send this?

If you're tired of reading and you want to speak with people, your best bets are RC Helicopter mailing list, the RC Helicopter newsgroup, and the RC Helicopter IRC channel (chat).

The mailing list requires that you have an email account, and it helps if you have a bit of extra time, too. It's not unusual to get 100 messages per day! Your humble FAQ author created a second email account specifically for h-list mail, so it doesn't bury his regular email account.

To join the mailing list (aka "the h-list"), go to www.uspilots.net and follow the 'mailing list maintenance' link to get signed up. Also, don't forget how to unsubscribe! Someday you'll want to.

If you ask a question on the mailing list, you'll typically get at least 4-5 responses over the next day or two.

The newsgroup requires newsreading software like Netscape Communicator or Outlook Express. Simply go to the rec.models.rc.helicopter newsgroup.

The newsgroup is slowest of the three media, but you will still have your answers within a couple days in most cases.

The IRC channel requires IRC software of course, for example PIRCH or MIRC. Go to rco.iglobal.net, port 6667, and join the #rcheli channel. If you need an answer right away, this is probably your best bet.

However, it can offer a few ideas that will hopefully make your decisions a little bit easier.

Also, no matter which product gets recommended, supporters (and even manufacturers) of other products are likely to complain. Your humble FAQ author doesn't want the flame mail! See the next section as well...

But remember, this document and the content herein are the opinions of the author(s), and they are entitled to them.

Nobody else is responsible for those opinions. Nobody else is liable for those opinions. Nobody else endorses those opinions.

But practically speaking, the helicopter becomes a tiny speck at 100 yards or more. If you can't see it clearly, you can't fly it properly. If you can't fly it carefully, you will crash it immediately.

So we tend to keep the helicopter close enough to where we can see not only where it is, but which way it's facing, which way it's leaning, how fast it's moving, and which side is up (this sounds like a joke, but it isn't!).

The average person's "sport" helicopter is still pretty quick though. A "30-class" helicopter typically has a top speed of 50-60 MPH, and a "60-class" helicopter typically has a top speed of 70-80 MPH.

$250 helicopter
$120 engine
$30 muffler
$250 radio system
$100 gyro
$75 starting equipment
$825 total

A more common figure for a 30-class helicopter breaks down like this:
$350 helicopter and upgrades
$120 engine
$50 exhaust system
$450 radio system
$250 gyro
$100 starting equipment
$100 various tools
$200 simulator
$1620 total

A common figure for a 60-class helicopter:
$750 helicopter and upgrades
$250 engine
$100 exhaust system
$450 radio system
$250 gyro
$100 starting equipment
$100 various tools
$200 simulator
$2200 total

And for the competition-oriented flyer who gets obsessed with the best and goes all-out, the cost might break down like this:
$1200 helicopter and upgrades
$250 engine
$100 exhaust system
$1200 radio system
$300 gyro
$200 rotor speed governor
$150 starting equipment
$200 various tools
$120 tachometer
$200 simulator
$3920 total

Three, four, and five bladed rotors are not unheard-of. They are most commonly used with "scale" models, where the builder is attempting to make a scaled-down replica of a real helicopter. In this case, the flying requirements are simpler (no aerobatics), so the stability of the flybar is traded off for the resemblance to the full-size helicopter.

Until the mid-1990s, most gyros were actually gyros - they had small flywheels, driven by an even smaller electric motor, to sense the rotation of the helicopter. In the later 1990s, piezoelectric oscillators began to replace the mechanical sensors. Though the sensor now oscillates, and doesn't really gyrate, the term "gyro" will probably be with us forever.

First, no matter which helicopter you buy these days, if you build it according to the instructions, it will serve you well. Each design has its own strengths and weaknesses, it's own die-hard fans and detractors. The most important differences have less to do with the helicopters themselves than your own situation. Ask yourself a few questions...

What do other people fly in your area?

Find out where other people fly in your area, and seek their advice. They will almost certainly be very helpful when you're starting out, and it's a good idea to start out with a helicopter that they are familiar with. That way, they will be better able to help you build, set up, and fly your new helicopter. They will be familiar with the shortcomings of your new helicopter (every helicopter has one or two) and they will be able to show you how to work around them.

What spare parts are available in your area?

If there is a local hobby shop that carries a good selection of spares for one or more models, this should affect your decision. Sooner or later, you will need spare parts, and the easier they are to obtain, the sooner you'll be flying again.

How much money do you want (or can you afford) to spend?

Many helicopters are available in two or more versions, each with different prices and different "upgrades" from the basic model. Typically the more expensive version will have more ball bearings where the less expensive version has simple bushings, for example. Typically, more money will buy you more reliability. If you continue to fly the helicopter a lot, you will probably end up replacing high-wear items (like bushings) with longer-lasting parts, so if you plan to be active in this hobby for a while, you will save money in the long run if you buy the more expensive kit. On the other hand, if your budget only allows for the less expensive version, you can simply replace those items over time if you find you need to.

Most radios on the market at the time of this writing fall into one of three categories, as follows. The prices are of course approximate.

1. six channel, $250, entry level
2. eight channel, $500, mid-level
3. nine or ten channel, $1000, high-level

The entry level radios will provide enough functionality to allow for hovering, forward flight, and mild (airplane-style) aerobatics. If or when you get into advanced (or "3D") aerobatics, you will probably find yourself requiring finer control of the pitch and throttle curves, as well as programmable mixing and extra channels to control the gyro and perhaps governor.

The mid-level radios provide everything the average flyer needs - and almost everything the "extreme" flyer wants. They include very flexible pitch and throttle curves, a couple of programmable mixes (for example, to add throttle during tumbles), and extra channels to control gyro or governor settings.

The high-level radios include pretty much everything a person could want, and then some. They include even more flexible curves (for example, seven adjustable points per curves instead of three or five), more programmable mixes (would you like the governor to turn on automatically when you enter idle-up?), more channels for control of onboard electronics (in-flight adjustable mixture, governor speed settings, and so on).

Your best bet is a mid-level radio. If you can spare an additional $500 for a high-level radio, go right ahead, but if you can't, don't lose any sleep over it. If your budget allows only an entry-level radio, consider getting a less expensive helicopter to allow for a better radio. Helicopters are difficult to outgrow, and can be upgraded a few dollars at a time; a limited radio will limit your flying ability, and radios can only be replaced, not upgraded.

If the thought of building the kit worries you, then RC helicopters are not for you - rebuilding these things is just as much a part of the experience as buying fuel and shooting the breeze with other heli flyers in between flights.

As you build the kit, you will learn a great deal about how the helicopter works. The more you know about how it works, the better you will be able to make it work just the way you want it to. The less you know about how it works, the more trouble you will have making it work at all.

At some point, you will crash it. If you built it yourself, you will look at the wrecked helicoper, frown, identify the bent parts, remove them, buy new ones, install them, and fly again the following weekend.

If you buy this fabulously complicated machine pre-assembled, and then crash it, you might find yourself looking down at the big ball of twisted plastic and metal, weeping and wondering if you could at least get $15 for it on eBay.

Tuning helicopter engines is one third attention to detail, one third practice, and one third magic. They all adjust a little bit differently, and an experienced hand will save you countless hours of aggravation while you learn to recognize the signs of a lean mixture versus a rich mixture, or too much compression versus not enough, or too hot versus too cold, and so on.

Though they may cost $200 or more, a simulator will - without question - save you at least $200 in crash repair costs because it will let you do most of your crashes in the comfort and safety of an imaginary world. Really, it's worth it.

When a new flyer arrives at the field for his first day, you can always tell whether or not they have been practicing with a simulator. If they spend their first 5 weeks skipping along the ground, stopping, carrying the helicopter back to the center of the flying area, making four-inch-high skips off in another direction, and so on, they haven't had the luxury of getting through this phase of the learning curve over the course of a few evenings at home. If they spend 10 seconds skipping around, then lift into an eye-level hover for the rest of their fuel tank, they definitely have a simulator at home. Really, the difference is that dramatic.

Your humble FAQ author learned with the help of a simulator, and had no idea how lucky he was until he saw how much time and effort it took to learn the old-fashioned way.

As with the kit, radio, and engine choices, you will not find a specific recommendation here. Fortunately, the current crop of simulators are all quite good, and any one of them will help. You really can't go wrong. I am still to this day using a four-year-old simulator to learn brand-new 3D maneuvers.

Before you take your first flight, you should have the helicopter examined by an experienced flyer. There are many, many, many ways to connect all of the parts, and not very many of them will result in a flyable helicopter. An experienced flyer will be able to wiggle the control sticks and see whether or not the rotor blades and carburetor bits are moving as they should.

If you want to find pilots (and you certainly do!), you start by finding out where they fly. If you already know of a local field, you know where to find local pilots. If you don't know of any flying fields near you, find them! Look in phone books, magazines, etc for local hobby stores. Ask the people at the store where their customers go to fly airplanes or helicopters.

If you're polite, you'll most likely find that people who fly helicopters are more than happy to answer questions, show you their equipment, and so on. There just aren't enough of us that we can afford to be rude to newcomers! Ask questions, and take note of the answers.

Note, though, that it's a really bad idea to talk to or even approach someone while they are flying a model. It takes enourmous concentration, and a tap on the shoulder or unexpected "Hi there!" can be exceptionally nerve-wracking. Causing someone to crash their model is a widely recognized way not to make friends.

If you have email, and can withstand close to 100 messages per day, you should sign up for the "h-list," an email discussion group with about 350 people, from complete beginners to accomplished competitors from all over the world. For signup infomation, visit the uspilots.net web site, and follow the links for h-list maintenance.

The right stick controls the helicopter's orientation on the pitch and roll axes. It's easiest to understand if you picture a little helicopter perched on top of the stick... If you push the stick forward, the nose dips down and the tail comes up, as if you were transitioning from a hover to forward flight. If you pull the stick backward, the nose goes up and the tail goes down, as if you were entering a loop. If you move the stick from side to side, the helicopter will roll from side to side.

Moving the left stick from side to side controls the helicopter's orientation about the yaw axis - like steering a car. If you move the stick to the left, the nose of the helicopter moves to the left, for a left turn; if you move the stick to the right, the nose of the helicopter moves to the right, for a right turn.

It is not unusual for a newcomer to set up the left stick in the opposite fashion, so the tail moves in the same direction as the stick. This is a bad idea! Nobody else will be able to fly your helicopter. Sometimes, when you're having trouble with your helicopter, it helps to have someone else fly it and experience it for themselves. A backwards setup will prevent others from giving you the assistance they would otherwise gladly offer.

Moving the left stick up and down controls both the throttle and the collective pitch. While you're learning, moving the stick upward will add pitch to the main rotor and will increase the engine power, causing the helicopter to climb. Moving the stick downward will cause the helicopter to descend.

Dual Rates
The dual rate switches let you choose how sensitive the control sticks are. Typically, "high rates" are used for aerobatics, which require a faster tumbles or pirouettes, and "low rates" are used for hovering, where slower, softer responses will give more precise control and smoother performance.

Gyro Rate / Gyro Mode
The gyro switch will affect the amount and type of feedback the gyro provides to help keep the helicopter stable about the yaw axis. In the past, it was common to use a high gyro rate for hovering, and a lower gyro rate for forward flight and aerobatics. With modern 'heading hold' gyros, the switch usually toggles between 'standard' gyro feedback and 'heading hold' gyro feedback. While heading hold is usually preferred for most types of flying, standard mode will allow the helicopter to "weathervane" a bit, which can be helpful in fast forward flight and rolling maneuvers.

Throttle Hold
This is for "autorotation," landing with the engine disengaged. This switch brings the engine to an idle and may select a special pitch curve, while leaving all other controls functioning normally. Most people select a pitch curve with about -4 degrees at the bottom and +10 degrees at the top, though some prefer a symmetrical curve like +/- 9 or 10 degrees for aerobatic (rolling or tumbling) autorotations.

Idle-Up
The name of this switch comes from days of old when all it really did was raise your idle setting. Today, it would be better labeled the "flight mode" switch. It selects between different pitch and throttle curves for hovering and aerobatic flight. Every flyer has their own preferences for flight modes - the following are merely one example of how things might be arranged.

In "normal mode," low stick will bring the engine to an idle and will put about -1 or -2 degrees of pitch in the main rotor. Half-stick will bring the engine and rotor to hover settings, perhaps 60% throttle and 4 or 5 degrees of pitch. With the stick all the way up, the engine will go to 100% throttle and the main rotor will have 8 to 10 degrees of pitch.

In "idle-up-1" the throttle curve begins to look take on a "V" shape, which helps keep the head speed up during descents and mild aerobatics like loops and rolls. Low stick might provide -4 degrees of pitch and 60% throttle, quarter stick -1 degrees and 30% throttle, half stick +2 degrees and 40% throttle, three-quarter stick +5 degrees and 60% throttle, and full stick +8 degrees and 100% throttle.

"Idle-up-2" is typically set up for "3D" aerobatics, in which the helicopter is configured to fly just as well inverted as right-side up. Typically the throttle curve is a true "V" shape, with 100% throttle at the top and bottom, and perhaps 40% in the middle. The pitch curve is typically very linear, for example -9 degrees at the bottom, 0 degrees at mid-stick, and +9 degrees at the top.

Note that this was written with the assumption that your helicopter's main rotor turns clockwise when viewed from above. This is true of most helicopters on the market today, but there are exceptions, mostly notably helicopters from Vario and Morley, and some Schluter models.

• hover tail-in
• hover nose-in
• hover side-on
• fly circles around yourself
• fly a figure-eight pattern
• do 180 stall turns
• do 540 stall turns
• fly circles out in front of yourself
• loop, roll

Some people suggest taking this all in order. In real life, you pretty much HAVE to do them in order because if you can't hover, you can't take off or land without killing your helicopter or your spectators. In the sim you can do anything safely!

Work on hovering, and when that gets frustrating, work on flying around. When that gets frustrating, work on hovering some more. Switch back and forth all you want, or just focus on one thing until you have it down. Just do whatever it takes to keep it interesting, so you stay motivated.

Your humble FAQ author mostly learned hovering and forward flight at about the same time in the sim. Then, in real life, it was almost like starting over and things went in roughly the following order:

• hover tail-in
• circles around myself
• figure-eight
• hover nose-in
• stall turns
• hover side-on
• loop
• roll
• circles in front of myself

This is NOT necessarily the best order, but things just happened that way. I have a web page about this experience, you might find it amusing:

Diary of a Helicopter Novice

That page was key to your humble FAQ author's first autorotations. There are just a few things I would like to add:

I did my first approaches in normal mode, which I had set up so that low stick gave me about -3 degrees of pitch and a nice idle. I practiced descending this way to get used to the sound, the head speed, the rate of approach, and so on. When the helicopter got down to 30 feet or so, I slowly raised the left stick, which reapplied power and allowed me to level out and fly on smoothly.

When I was comfortable with that, I started using the throttle hold switch. I would descend at low stick (again, about -3 degrees), flare, and turn off throttle hold so I could fly away safely. I did this several times, each time flaring a bit lower. There came a time when I figured I was almost ready to land, I would just flare at 3-5 feet a couple times and then finally I'd (gasp!) do it for real. As it happened, I descended planning to flare and 3 feet, and I just landed it instead. Everyone is always surprised at how easy it is after landing their first auto, and I was no exception.

Now go back and read HeliBuf's page once more, and have at it.

Good luck!

1) Throttle goes to an idle. This will help slow the rotors, making the crash less damaging for both the helicopter and whatever it hits. This will also reduce (and change the frequency of) the vibration present in the helicopter, which will sometimes restore control, at least long enough to hit throttle hold and glide in.

2) Collective pitch holds last position. For years I brought this to center (zero degrees collective pitch), until someone in the newsgroups pointed out that no matter which side is up, you're almost certainly using the rotor to generate lift - so keeping the collective in the same position will be almost guaranteed to slow the rotor, and keep the heli airborne longest, and without causing an abrupt change of direction.

3) Both cyclic servos go to center, and the rudder channel goes to center. If I lose control, I want the helicopter to remain in the same attitude until I get it back. If I don't have to follow it though a roll or tumble or pirouette, I'm that much more likely to regain control with my brain as soon as I regain control with my radio.

4) Gyro goes to heading hold mode, again to help keep the heli's orientation from changing.

It's been said that different PCM settings just mean the heli will crash "over here" instead of "over there" and I'm inclined to agree. However, the above settings seem the most likely to prevent serious injury to other flyers and spectators in the event that the helicopter remains out of control long enough to hit the ground (which is usually not very long at all). And in the event that the radio connection is restored, the above settings seem most likely to allow me to regain control and return the helicopter to earth safely.

If the gyro direction is set wrong, the gyro will not act to reduce heading changes, instead it will act to amplify heading changes. The slightest touch of the rudder will cause the gyro to rapidly apply full rudder in that direction.

Helicopters are hard enough to fly without a gyro helping you. They're pretty much impossible to fly with the gyro fighting you every step of the way.

Different gyros use different methods to set the gyro direction. There may be a small switch, a screen in the setup menu, a jumper, or you may need to install the gyro upside-down to reverse its effect. Consult your gyro's instructions.

But it's better to be able to detect this condition before unleashing a five-foot flying lawnmower upon yourself and your neighbors. Fortunately, it's not too difficult.

Remove the canopy, turn on your transmitter and helicopter, and wait for the gyro to 'wake up' if necessary. For this test, the gyro should be in standard (not heading hold) mode.

Push the rudder stick to the left, and watch which way the tail rotor servo moves. Return the rudder stick to center. Pick up the helicopter, and hold it with a finger or thumb atop the rudder servo horn. Yaw the helicopter to the right, as violently as you can (within reason of course). You should feel the rudder servo moving just as it did when you commanded left rudder. If it moves the opposite direction instead, do not fly until you have reversed the gyro and completed this test successfully.

That said, consider the following potential problems, roughly in order of likelihood:

• Is the gyro gain high enough? If you can turn it up without causing the tail to wag, you should do so.
• Is the tail rotor pitch slider able to move from end to end without binding?
• Is there any slop in the tail rotor pitch linkage?
• Is the tail drivetrain slipping? This is common with the LMH-100 series, and with helicopters that use belt-drive tails.
• Are the tail blades long enough?
• Are the main rotor blades balanced?
• Are the tail rotor blades balanced?
• Is your flybar bent?
• Does the engine run smoother if it set the mixture a little bit richer? A little bit leaner?
• Are your flybar paddles level? This can induce vibrations.
• Is your flybar balanced? If you disconnect all of the flybar links, it should balance perfectly.
• Is the main shaft straight, or could it have been bent in a crash?
• Is the cooling fan dial-indicated to within 1 o 2 thousandths of an inch?
• Is the tail rotor output shaft straight?
• Is your gyro mounting foam correct for the gyro you are using? The CSM gyro, for example, works best with the foam it is shipped with, which is different than anything else out there.
• Are the tail rotor blade grip bearings working smoothly, or have they become notchy?
• Do you need a faster tail rotor servo?
• Is your tail rotor servo working properly? or have the gears worn down? has the motor weakened?
• Are your feathering shaft(s) straight, or could they have been damaged in a crash?

This list is not complete, but it should get you started, and will address the most common "gyro" problems.

If you have no luck, consider the gyro itself - see if you can try a different gyro, preferably of the same make and model. Try changing servos, too.

That said, your humble FAQ author has tried all of the above, and his Concept SRX still doesn't behave as well as it used to!

First, and easiest, inspect your control throws. Reducing your throws will allow for softer response and slower rolls. Increasing them will speed up your rolls and make the controls more sensitive, but be careful not to bind the swashplate by trying to tilt it too far!

Second, and also free of charge: if you have flybar weights installed, move them closer to the rotor head or remove them entirely for faster rolls. Move them outward for slower rolls and a more stable hover.

Third, and also free if your helicopter allows it, change your Bell:Hiller mixing to allow more Bell input (direct from the swashplate) and less Hiller input (from the flybar) for faster rolls. Adjusting for more Hiller input will give you slower rolls and more stability.

Though it may seem counter-intuitive at first, the flybar actually slows down your rolls, so reducing the flybar's leverage on the main blades will speed up your roll rate. On many helicopters, this is adjustable via mixing levers attached to the blade grips. On others, it requires an upgrade part (the Concept series, for example, requires an aftermarket adjustable flybar seesaw). On others, it requres creativity... the Futura SE, for example, has non-adjustable Bell:Hiller mixing, at a ratio of 1:1. At least one Futura has been spotted with XCell adjustable mixing levers installed. Your humble FAQ author has a set of these levers for his own Futura SE, but hasn't yet gotten around to installing them yet.

Fourth, and usually fairly inexpensive, try new flybar paddles. Lighter paddles will speed up the roll rate; heavier paddles will slow down the roll rate.

Fifth, and most expensive, try new rotor blades. Different airfoils will affect your roll rate, as will different lengths. "Reflex" or "S-curve" airfoils tend to be more responsive, but more twitchy in a hover (this includes collective response as well as cyclic). Traditional airfoils are more stable.

Heavier blades will slow your roll rate, and extend the 'hang time' at the end of your autorotations. Lighter blades will accellerate your roll rate, but at the expense of autorotation performance.

A standard fuel tank setup will have a two pieces of tubing connected. First, a simple "pressure" line, which attaches to a fitting at the top of the tank and typically connects to the muffler (which supply pressure). Second, an "intake" line, which connects to the carburetor at one end, and which terminates in the middle of the tank, with a klunk. The klunk is typically a brass weight with a hole drilled through the center - it attaches to the end of the fuel line and helps keep the end of the fuel line submerged, so the fuel line doesn't end up sucking air into the carburetor.

A uniflow tank will have three pieces of tubing connected. The old "pressure" line is now a "vent" line. It remains attached to the fitting at the top of the tank, but instead of going to the muffler, it ends in open air, with a valve or plug to keep the line sealed. In flight, it remains sealed - it is unsealed only to allow air to escape when filling the tank with fuel. The "intake" line remains unchanged. The third line is the new "pressure" line. One end is connected to the muffler (as before) and the other end is in the middle of the tank, with a klunk on it.

The klunk on the pressure line does the same thing as the klunk on the intake line - it keeps the end of the line submerged, even as the fuel sloshes around during loops and rolls and such.

A conventional tank will often cause the mixture to "lean out" as the tank empties. This is because when the tank is full, the fuel naturally "wants" to siphon out into the carburetor. As the fuel level goes down, the carburetor may actually need to "suck" to draw fuel up into the engine. The fuel pressure changes, but since the carburetor's suction does not change, the mixture ends up changing instead. Uniflow tanks cure this problem.

Conventional tanks are also sometimes subject to mixture changes between upright and inverted flight. Uniflow does not solve this problem entirely, but it can improve things enough to make some people swear by it in some of their helicopters (your humble FAQ author included).

Check back again for a link to a site with a good uniflow diagram to help explain how to set up a uniflow tank and how uniflow works to ensure a more consistent fuel/air mixture.

There is no free lunch, however... uniflow has a couple of disadvantages.

First, fueling becomes a little bit more tedious, as you must remember to open the vent line before filling the tank - otherwise you end up pumping fuel into the tank (through the intake line) across the tank (which cannot vent air or expand to accomodate the additional fuel) out of the tank (via the pressure line, which is submerged), and into the muffler. The amount of fuel that can pool up in your muffler before you realize what you've done can be embarassing.

Second, during an abrupt transition from high throttle settings to idle (e.g. practicing autorotations), uniflow can cause the mixture to become rich for a moment before the excess pressure is exhausted. Depending on the engine, helicopter, fuel, altitude, humidity, phase of moon, etc, this can actually be severe enough to cause the engine to quit! Before practicing full autorotations with a new uniflow setup, it's wise to practice a couple of small ones (from a waist-high hover) first to find out if this is going to present a problem.

Personally, I have found uniflow to be VERY effective in my Concept 30 SRX and OS 32sx, using both a muffler and a tuned pipe. I have personally never had the aforementioned throttle-hold problem, but perhaps I'm just lucky?

It's worth noting as well that high-pressure systems suchs as modern YS engines do NOT require uniflow to obtain a consistent mixture. These engines use crankcase pressure instead of muffler pressure, and use internal regulators to keep the mixture consistent.

Fritz Blackburn has a web page with excellent diagrams of uniflow and header tank fuel systems.

You can find the CG by lifting the helicopter by the blade grips or by the inside ends of the flybar. If the tips of the skids leave the ground first, your helicopter is tail-heavy (this is not good). If the tails of the skids lift off first, your helicopter is nose-heavy (this is better). If the skids remain level, your helicopter's CG is right under the mainshaft (how much fuel is in the tank and what will happen when that changes?).

Your humble FAQ author's helicopters have foward-mounted fuel tanks, and he prefers to set them up so that when thet tanki s empty, the CG is directly under (or just barely forward of) the main shaft; with a full tank, the CG moves a bit forward of the main shaft.

Any flying object will have a tendency to orient itself so that the CG leads the aerodynamic center (also called the center of pressure, or CP). On most helicopters, the tail rotor and tail fins act to place the CP well aft of the main shaft, so if the CG is located forward of the main shaft, your helicopter will tend to "weathervane" into a nose-first orientation.

When you are learning, this nose-first tendency will be helpful, especially during autorotations. Should you progress into backward and sideways flight, or backward autorotations, you will be better served by a more neutral CG/CP relationship. (Hence the popularity of "skeletal" or even nonexistent tail fins.)

Note that aerodynamic tendencies are only part of the picture. With a heading hold gyro and a reasonable main rotor setup (i.e. anything but massive and feather-light flybar paddles), the helicopter will maintain whatever attitude the pilot commands, regardless of the helicopter's CG and CP. With a driven tail, the helicopter will maintain whatever attitude the pilot commands, even during an autorotation. At worst, an uncooperative CG/CP relationship will mostly show itself in decreased rotor energy as the tail fights against the weathervane effect.

CG adjustments are typically made by moving the receiver battery forward and backard. Adding weight should be considered a last resort, since you can typically get the same effect by moving the battery further foward. Moving the tail rotor servo from the front of the chassis (if the kit places the servo there to begin with) to the front of the tail boom will often shift the CG significantly rearward (which is often a challenge to remedy).

Normal is used for starting the engine, so the throttle setting at low stick needs to be a nice idle. Depending on your radio, this means that the bottom 25% or 50% of the stick range will cause your head speed to drop off. At the beginning and end of a flight, this is a good thing. In mid-flight, this is a very bad thing. It causes your cyclics to go mushy, it reduces your collective response, it confuses your gyro, and it's just generally bad news all around.

When you get into forward flight you also get into descents, since that's how you get from "up there" to "down here." You may find yourself needing quick cyclic corrections and lots of collective in order to arrest the descent. If you transtion from forward flight to hover in normal mode (aka idle-up-zero), you may find yourself with no head speed at a time when you need it more than ever. This can get expensive.

An idle-up flight mode will allow you go use the whole range of stick movement without losing head speed.

When you start out with forward flight, an idle-up-1 pitch range like -4.5 to 9.5 is just the ticket. -4 to +8 if you have less power, -5 to +10 if you have more. When you get into more advanced aerobatics, you'll find yourself wanting a symmetical range like -9 to +9. If you ask me, that's what idle-up-2 is there for.

So, you can have idle-up-zero for starting and finishing your flights, idle-up-one for FF and mild aerobatics (loops, start turns, etc), and, when you're ready, idle-up-two for more adventurous aerobatics (hovering tumbles, sustained inverted flight, etc).

Many folks like to use the same pitch curve in all modes. I'm not one of them, but I do see the attraction to this. Your collective "feel" is always the same, and you can switch between modes with no bobble as the pitch curve changes.

The advantage to reduced pitch ranges like -4 to +9 is that the collective stick is less sensitive when the collective range is smaller. It's got much the same effect as a dual rate switch. I continued using this sort of idle-up-1 range in my Concept SRX until I was well into 3D stuff. These days I've gotten accustomed to using idle-up-2 all the time, but I'd do the same thing again if I had to start over. The softer collective was a nice aid when I was working on hovering pirouettes and other upright-only stuff.

Lots of folks like to set the mid-stick position to their hovering pitch, e.g. 5 degrees. The advantage to this is that you still hover at half-stick. However, with 5.5 degrees at mid-stick, you may have 4 degrees of collective in the top half of the stick travel (very soft and gradual) and a whopping 10 degrees of collective range in the bottom half of the stick travel (relatively twitchy). This will leave you with a different collective "feel" depending on whether you're climbing or descenting. With a mid-stick pitch of 2.5 degrees, you'd have 7 degrees of travel in either direction, and a more consistent "feel" across the stick's entire range.

You'll end up hovering at 5/8-stick instead of 1/2-stick, but who cares? When you get into idle-up-2 you'll be hovering at 3/4 stick upright (and 1/4 stick inverted), so hovering at 1/2 stick isn't exactly mandatory! You might as well get used to controlling the hover colletive based on how the heli behaves, not on where you thumb is at.

I believe that throttle curves should be set up to maintain a constant head speed at the corresponding collective settings. Note that this almost never works out to a linear curve.

Here are some initial settings to consider for idle-up-1:

full stick .. 9.5 - 100%
3/4 stick .. 6.0 - 65%
1/2 stick .. 2.5 - 35%
1/4 stick .. -2.0 - 30%
low stick .. -4.5 - 0% in normal, 20% in idle-up-1

When you get into loops and rolls, you'll want to boost the low stick throttle to 50% or so, to keep the head speed up while you're inverted.

Notice that each step in the pitch curve is a difference of 3.5 degrees. That keeps your collective feel consistent from top to bottom.

Notice also that I guessed at the throttle settings as I went along. You'll want to change those I'm sure... They should get you into the ballpark though. If you hear the rotor overspeeding or underspeeding in certain stick positions, adjust the corresponding throttle setting as necessary.

Here are some initial settings to consider for idle-up-1:

full stick .. 9.50 - 100%
3/4 stick .. 4.25 - 65%
1/2 stick .. 0.00 - 40%
1/4 stick .. -4.25 - 65%
low stick .. -9.50 - 100%

Notice that each step in the pitch curve is a difference of 4.25 degrees. Again, that keeps your collective feel consistent from top to bottom.

Notice again that I guessed at the throttle settings as I went along. As with the idle-up-1 example, they should get you into the ballpark. If you hear the rotor overspeeding or underspeeding in certain stick positions, adjust the corresponding throttle setting as necessary.

It helps to have a friend with an optical tach set help you up your throttle curve, but your ears will get you pretty close. It just takes a bit more trial and error that way. your friend's ears can help too - have they listen when you fly, and ask them if they noticed the head overspeeding or underspeeding. Figure out when this happens, figure out where your stick was when it happened, and make the appropriate adjustments.

Different kinds of blades will have different lead-lag angles, depending on the chordwise position of the blade's center of gravity (closer to the leading edge, or closer to the trailing edge) and the shape of the blade's airfoil. As long as the blades are well matched (chordwise and spanwise CG, airfoil, weight), you can expect them to 'seek' identical lead/lag angles.

Try holding the helicopter with the nose pointing straight up and the blades sticking out sidewise. If the blades rotate downward under their own weight, the blade bolts should be tightened. If they blades remain in position, the bolts are tight enough.

Note that this is not, in my opinion, a critical adjustment. If the tension is 'high' enough to keep the blades from lagging at low head speeds, you'll be less likely to have boom strikes. If the tension is 'low' enough to allow the blades to find their proper lead-lag angles, you'll be less likely to have vibration problems. If the tension is low enough to not crack the blade grip or blade bolt, you'll be less likely to see the rotorblade depart in flight. There is a LOT of room for variation between these extremes, so don't lose too much sleep over this.

I tighten the bolts until they start to get snug, then wiggle the blade back and forth by hand, making very small adjustments to the bolt tension until the blades start to feel tight in the grips. There is no need to torque down on these bolts.

I will assume that gyro gain is controlled by a two-position switch on your transmitter.

With a standard gyro, a "center" signal on the gain channel will give you 50% gyro gain. Changing the gyro gain signal to either direction will raise or lower the gain - the question is, which direction raises the gain and which direction lowers the gin?

Set the gyro channel ATVs to 100% in either direction. Put the switch in the position you want for 'high' gain. Turn on the transmitter and receiver, and wait for the gyro to 'wake up.' Pick up the helicopter by the rotor head with one hand, and use your other hand to wiggle the tail boom left and right as quickly as you can. Listen to the sound the rudder servo makes. Remember that sound.

Now put the switch into the position you want for 'low' gain. Pick up the heli and wiggle it again. If the servo makes less noise, or no noise at all, your high and low gain settings are in the right positions. IF the servo makes more noise, you need to reverse your gyro gain channel.

Now set the gyro gain ATV's to 50% in either direction. To raise the gain of the 'low' setting, decrease the ATV for the low setting. To raise the gain of the 'high' setting, increase the ATV of the high setting. Having them set for 50% in either direction will give you a place to start. Different people have different ideas about what is the "best" use of the high and low gain settings, that's another subject on its own.

For most heading hold gyros, it's a bit more complicated. "Center" for the gain channel is 0% gain. Changing the gain channel all the way to one side will give you lots of standard gain, changing the gain channel all the way to the other side will give you lots of heading hold gain. The question is, which direction is which?

Set the gyro channel ATVs to 100% in either direction. Put the switch in the position you want for 'high' gain. Turn on the transmitter and receiver, and wait for the gyro to 'wake up.' Put the gain switch in the position you want for heading hold mode. Move the rudder stick to the left, hold it there for a second, and move it back to center. If the rudder servo stays off of one side, you're really in heading hold mode. If the servo returns to center as soon as the stick returns to center, you're in normal mode. Reverse your gyro gain channel to make this heading hold mode. Just to be sure, repeat this experiment with the gain switch in the position you want for standard mode. No matter how much you wiggle the rudder stick, the rudder servo should always return to center when you let go of the rudder stick. In heading hold mode, the rudder servo will act like it has a mind of its own.

Increasing the gyro channel ATV will increase the gain you have in the associated gyro mode. Decreasing the gyro channel ATV will decrease the gain you have in the associated gyro mode.

For example, it seems that whenever someone buys a new kit, they always want to know what isn't in the instructions! Try as they might, manufacturers always omit a few details that can make construction and setup a little bit easier.

New submissions are welcome! If you'd like to share a construction, maintenance, or setup suggestion for your helicopter, please send it to: helifaq@whatever.net

With lots of negative pitch and lots of cyclic, it's possible to throw the washout levers too far and bind them. This will result immediately strip out your cyclic servos (as the rocks back and forth at 1700 RPM), and catastrophe is sure to follow.

For a little extra safety, replace two of the balls on the upper/inner swashplate ring. The balls they instruct you to use have a 2 or 3mm standoff - replace them with the shorter no-standoff balls. I think you can scrounge them from elsewhere in the kit, but I'm not certain. I bought mine used and the previous owner already took care of it.

The balls that connect to the links that go up toward the blade grips can remain stock. The balls that connect to the washout lever should be shortened. This will give you slightly less input to the flybar, but you will still have enough to hit the limits on the rotor head. I assure you it flies well this way. I have yet to see a Futura in my area that hasn't been modified like this, in fact.

You will still need to be careful when setting up your radio - make sure that when you give full down collective and full cyclic, the washout levers aren't able to over-extend and bind. If you keep the bell links short, you can basically move the swashplate up on the main shaft while keeping the same amount of negative pitch. This keeps the washout happy.

The way my heli is set up, binding is impossible in flight. I never worry about it anymore.

Robbe produces an upgrade package to address this (part number S1025). The upgrade is relatively inexpensive and worth a look if you can't get the pitch range you want without risking your safety.

Three things to watch during construction:

Take care when tighening the bolts that hold the engine mount to the chassis. They hold the engine mount in place vertically, and determines the drive belt alignment. It's really no trouble to get it right, but if you overlook it you might have a surprise auto and a big wad of steel wool where the drive belt should be. Boy did I feel silly. :)

There's one thing that might be my fault and might be the kit, I'm not sure which. Build the rudder linkage before installing the tail boom. Line up the rudder linkage at each end as you slide boom into the mounting block. I pushed the boom in too far, now I can't back it out(!), and it's affected my rudder linkage geometry. Probably my fault, but keep an eye out for it.

Finally, I direct your attention to the small gear that sits above the large pulley and drives the main gear. The shaft that holds the gear and pulley can slip inside the bearings. Use loctite 290 to bind the shaft and the inner bearing race. This is probably enough on its own, but I was also advised to peen the shaft as well (score it with a punch or something to scuff it up). I'm told the shaft and bearing can gall each other, which sounds like bad news for the main gear.

The tail rotor's "flybar" must be able to tilt freely.

The metal block set-screwed to the end of the rudder control rod must be installed with the set-screw facing down, or your will face uncontrollable pirouettes as the gyro amplifies yawing motions instead of reducing them.

If you have significantly more rudder authority to one side than the other, you can adjust the pitch of the flybar paddles to bring things into balance.

Your rudder servo must exercise the entire travel of the tail rotor pitch change mechanism.

Unfortunately, even with a piezo gyro, the LMH will not be as stable as a 30 or 60 class helicopter. Larger helicopters typically have a main-to-tail rotor speed ratio of 1:4.6 or thereabouts. The LMH main:tail ratio is close to 1:2. This reduced tail rotor speed limits the performance of the tail rotor significantly. One can only hope the the Lite Machines folks (or an aftermarket company?) will offer a revised tail rotor gear ratio as an upgrade.