Chapter 4. Helicopter Parts Selection

Table of Contents

4.1. Control system
4.2. Servos
4.3. Batteries and related items
4.4. Motors and related items
4.5. Upgrades

4.1. Control system

4.1.1. Receiver

If you are using a gyro without remote sensitivity (like the GY240) on a fixed pitch heli, then you only need a four channel receiver (channels 1-4).

If you are using a gyro with remote sensitivity (like the GY401) on a fixed pitch heli, then you need a receiver which can receive channels 1-5.

If you are using a gyro without remote sensitivity (like the GY240) on a collective pitch heli, then you need a receiver which can receive channels 1-4 and channel 6.

If you are using a gyro with remote sensitivity (like the GY401) on a collective pitch heli, then you need a receiver which can receive channels 1-6.

See Section 9.1, “Channel assignments” for individual channel assignments for Futaba/JR etc. transmitters.)

Single conversion receivers will work fine for indoor microhelis, but are not recommended for larger outdoor helis. The larger motors in larger helis will generate much more electrical interference which will overload a single conversion receiver and cause severe glitching. A large helicopter which is out of control is very dangerous! Therefore, use a good quality dual conversion or PCM receiver for larger helis.

There have been many reports of some Berg 4/5/6 channel receivers manufactured after November 2004 having serious range issues. If you purchase one of these, please be sure to throughly test it before flying it in a heli.

4.1.2. Antenna

For indoor micro helis on 72 Mhz, the Azarr M72-I works well. This is a 0.3 gram antenna which is designed for indoor use.

For outdoor helis, the Deans one-piece antenna works well. The two-piece is not recommended because the threaded coupler can vibrate loose and cause glitching during flight.

4.1.3. Gyros

See Chapter 29, Glossary for a definition of Yaw-Rate Gyro and Heading Hold Gyro .

See Section 28.1.7, “How gyros work” in Chapter 28, Technical Appendix for more information on gyros.

The first question people invariably ask is: "Can I fly a helicopter without a gyro?" The answer is basically no. The helicopter's tail would be too sensitive to random air currents. Before helicopter gyros were invented, the world endurance record for flying a model helicopter was 5.65 seconds by John Burkham in 1969 in the "Super Susie" model.

A heading hold gyro is highly recommended for beginners. There are four reasons for this:

  • A heading hold gyro is much easier to configure than a yaw rate gyro. The yaw rate gyro requires the revo mix curve to be set up correctly before learning hovering, and this is tricky to set up for beginners.

  • The heading hold gyro will "lock" the tail at one heading rather than just dampening random tail movement. This is very good because you only need to learn two joystick axes initally instead of three. This means you can learn the right joystick first, then learn the left joystick later(for mode 2) instead of trying to learn both joysticks simultaneously. This makes learning hovering much, much, easier.

  • The revo mix (required for a yaw rate gyro) will not compensate for the battery voltage dropping as the battery discharges. So, near the end of a flight, you will need to hold some rudder to keep the heli from turning. This makes learning hovering more difficult.

  • A yaw rate gyro will require the revo mix to be changed every time the weight or headspeed changes.

    • If you install a modification which changes the heli weight, you will need to readjust the revo mix.

    • If you change the pinion to a different tooth count, you will need to adjust the revo mix.

    • If you have battery packs which are different weights, you will need to adjust the revo mix between packs.

The differences between the GY240 and GY401 are:

  • The GY401 has a DS mode switch to enable a high-speed (200 hz) update for digital servos. The GY240 does not have a DS mode switch, but will still work with digital servos using the normal update rate (50 hz).

  • The GY401 has a limit adjustment so the tail servo travel can be electronically limited as well as mechanically limited. The GY240 does not have a limit adjustment so the tail servo travel can only be mechanically limited.

  • The GY401 has a remote gain lead (which plugs into a receiver channel) so the gyro gain can be set from the transmitter. This lead MUST receive a valid transmitter signal and cannot be left unplugged. The GY240 has a gain adjustment on the gyro and does not support remote gain.

  • The GY401 has a very fast pirouette rate. The GY240 has a very slow pirouette rate.

Futaba GY240 gyro

The GY401 is a more advanced gyro with many adjustment options. It requires a dedicated channel for sensitivity adjustment so it requires a radio with at least five channels. Also, the sensitivity is a little tricky to set up properly.

I would recommend purchasing a GY401 unless you have a four-channel radio, in which case you can only use the GY240.The GY240 also works slightly better than the GY401 on micro helis with tail motors, such as the FP Piccolo and clone because the GY240 seems to handle slow tail response better than the GY401.

Most heading hold gyros (other than the Futaba GY series) seem to have drifting problems. This is caused by the gyro's expectation of the rudder "center stick" position being different from the transmitter's center stick position. This can be very frustrating because the one click of the subtrim can be the difference between the heli slowly turning left and the heli slowly turning right.

The Futaba GY series seems to calibrate the center stick position at power-up which eliminates the need to use rudder subtrim. Therefore I highly recommend the GY240 or GY401 for beginners.

The inexpensive Hobbico gyro is NOT recommended for beginners. It is a yaw rate gyro, which makes hovering difficult for beginners. Also, it is very fragile and there are many reports of it breaking on the first heli crash from only 1.5 feet of altitude.

TREC ESC by Dionysus Designs

The TREC ESC by Dionysus Designs is a special ESC with built-in mixing options. It is a tail motor ESC that can read the throttle signal and do its own revo mixing. It also has many other features such as a 17 point throttle curve, low voltage monitor, etc. and weighs only six grams.

If you use two separate ESCs with their own BECs, don't forget to disable one of the BECs on one of the ESCs otherwise they may "fight" each other and overheat causing a BEC failure. To check for this, power up both ESCs (without motors attached) and see if the BECs of the ESCs run hot.

The GWS PHA-01 mixer board is similar to the Piccoboard, except it is not upgradable to a heading hold gyro. It is not really recommended for microhelis because it is very prone to overheating and will shut down abruptly when it overheats. It will also not re-arm until it cools down which can take 10-15 minutes. If you must use one, be sure to mount it where it will get airflow (NOT inside the cabinet on the side of the heli).

The Century CN2000-4 gyro+mixer board is also similar to the Piccoboard and is also not upgradable to a heading hold gyro.

The Century CNE052 mixer board is similar to a Piccoboard without a gyro (i.e. mixer + dual ESC). You must use a separate gyro with this board.

All of these combo units (Piccoboards, PHA-01, CN2000-4, CNE052) are only usable on submicro and microhelis. They will not work on larger helis such as the Corona, ECO 8, Logo 10, etc.

4.1.4. FMA Copilot

Some people have used the FMA copilot on their Corona heli. This is a device which will "level" the helicopter for you if you release (center) the cyclic control. It will not work indoors because it needs to see the horizon to work properly. It does not replace a gyro, so you will still need a gyro.

The FMA copilot is nice, but really isn't really necessary unless you are having problems learning hovering. If you have a limited budget, then it is more important to buy a good heading hold gyro than the FMA copilot.

Also, you will likely outgrow the FMA copilot after a few months and remove it whereas you will not outgrow a good heading hold gyro. Therefore I recommend buying a good heading hold gyro first, and purchasing an FMA copilot later if you become frustrated with learning hovering.

4.1.5. Revo mixing

If a transmitter without revo mixing capability is used with a yaw rate gyro, then some sort of revo mixing capability is required on the heli. Some heli motor controllers such as the Piccoboard, TREC, and 3-in-1 boards include revo mixing capability.

Dionysus Designs also manufactures a separate revo mixing board which allows the use of both brushed and brushless main and tail motor ESCs.