Model Helicopter Gyros Explained
By Jeff Barrington - Mid Devon Heli Club

The purpose of the gyro is to stabilize the tail, without it the model would be almost unflyable. Early gyros had a motor and two flywheels inside and at the time worked quite well but they are no match compared to piezo gyros, which have no motor but use an electronic sensor.

Piezo Gyros
Modern piezo gyros have never been so good and are no longer an expensive alternative but an essential part of the radio system. Modern peizo gyros can cost anything from 40 to 300. So how much should you spend and which one should you buy?

Well at the lower end of the scale the gyro will be single rate adjusted on the gyro itself and will not have pilot authority, while at the top of the range it will probably be dual rate in both normal and heading lock mode (sometimes called heading hold or AVCS), selectable from the transmitter, and it will also have full pilot authority.

Modern piezo gyros have a very fast response, and will need a servo, which can keep up with the gyro output. Servo speed is measured by the number of seconds it takes for the servo to turn 60 degrees so a digital servo with a speed of 0.12s/60 to 0.08s/60 is the ideal but you will have to pay around 60 to 125 for it.

Gyro Gain
The best way to adjust gyro gain is to turn it up until the tail wags in forward flight then turn it down a little. You should be able to get near 100% gain, if you cant then try changing the length of the rudder servo arm, there is no point spending serious money on a good gyro and then only using 50% gain.

Pilot Authority
On a standard gyro when you input a rudder command the gyro will try to correct the tail back to the centre, the higher the gain on the gyro, the less tail authority you will have.
With pilot authority the gyro gain decreases as you input commands so you can have 100% gyro gain and still have full tail authority.

Heading Lock
With the gyro in normal mode the tail will weathercock to some extent so when flying circuits or hovering in to wind the tail will tend to follow the line of the model. In heading lock mode the tail stays wherever you put it, so it is quite easy to fly the model sideways or backwards at speed without losing the tail position. The only downside to heading lock mode is that you have to steer the tail all the time as it will not naturally follow the model, and if you enter a manoeuvre, say a loop, with the tail offline it will stay offline throughout the manoeuvre. If you are not sure which mode the gyro is in, with the radio on and without the engine going, move the rudder control fully to one side, if heading lock is selected the servo will stay at one end until you move the stick back to the other side.

Mixing Makes
I have used Futaba, JR, and CSM gyros on JR radio systems with no problems at all but I would advise the use of a matching rudder servo in the case of JR or Futaba, as they would have been designed to work with their own servo.

 
Up Grades & Add Ons
By Jeff Barrington - Mid Devon Heli Club

If you have only recently started in this hobby you probably have a 30-sized model with wooden blades and basic radio equipment, fair enough, you don't want to spend too much on a new venture, as you may not like it. As your flying progresses you will want to improve your equipment accordingly. Here are some of my suggeastions on what to upgrade.

Exhaust System
I mention this first, as a quiet muffler is absolutely essential, flying sites are lost due to noise complaints so the quieter the better. Avoid tuned pipes as they are generally noisier, the extra power is not needed and the engine is much more difficult to set up.

Main Blades
Most carbon glass blades will be an improvement on the wooden ones that came with the model. There are 2 main types or sections, semi symmetrical which have a flat bottom to give more lift, and fully symmetrical which are the same shape both sides. Which ones you go for depend on your flying style but without getting to complicated, symmetrical blades are better for aerobatics. They give the same pitch inverted as they do the right way up, where as semis generally perform better in autorotation.

Radio
More of an essential than an upgrade is a PCM receiver, as PPM receivers have no fail-safe system. If your transmitter is a very basic one it might only have 1 or 2 pitch and throttle curves and probably only 3 point curves at that. This will be limiting, particularly if you want to progress to aerobatics. The more expensive transmitters will have a minimum of 3 pitch and throttle curves, and many more functions, which become more useful as you progress.

Gyro, Servo and Tail Control
The best gyro you can afford along with a suitably fast rudder servo will probably be the most noticeable upgrade you will get, depending on what gyro you had before of course.

My Raptor 30 cost a little over 200 but the gyro and servo cost nearly 300! The point is no matter how good the model it will be much better with a good gyro. The control from the rudder servo to the tail pitch control will vary from one model to the other. A smooth straight direct control is desirable, tail boom mounted servo brackets and carbon rod upgrades are available to suit most models and these tend to work best.

Servos
The latest digital servos are much more accurate and responsive and start at around 40, although if you have a 60 sized machine you may want to spend more on higher torque servos.

Fuel Header Tank
There are at least 3 good reasons to fit a header tank, it will stop problems with fuel foaming, it gives a consistent level of fuel no matter how much fuel is in the main tank or what ever the attitude of the model, and you get longer flight times.

Metal Upgrades
There are plenty of after market metal upgrades available for most makes of helicopter. They are usually anodised in purple or gold colour and even if they are not needed they do look nice on the model. A metal swash plate is probably the first upgrade, followed by the washout assembly and many more.