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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 GY240 is a very popular beginner gyro and is very easy to setup. Also, the GY240 does not require a sensitivity channel and therefore can be used with four-channel radios. However, it does have a very slow pirouette rate and you will eventually outgrow it.
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.
The Piccoboard used on the Piccolo is a single board with the following items:
Yaw rate gyro (expandable to heading hold on the Plus or Pro)
Main motor ESC (brushed
Tail motor ESC (brushed)
The older versions of the Piccoboard had extremely fragile gyro sensors and are not recommended for beginners. Supposedly the recent ones are more durable. For more detailed information on the various versions of the Piccoboard, consult Paul Goelz's Piccolo site.
The newer Piccoboards can be upgraded to a Plus by installing a four pin header into the four holes on the PCB.
The difference between the Piccoboard/Piccoboard Plus and the Pro is the Pro can handle a larger main motor and the BEC capacity is doubled. My guess is the Piccoboard has about a ~7 amp ESC for the main motor, and the Piccoboard Plus has about a ~10 amp ESC for the main motor.
The Piccoboard is not necessary for the Piccolo, and can be replaced by either:
A yaw rate gyro + two ESCs (w/BEC) (requires revo mixing on transmitter)
A yaw rate gyro + one ESC (w/BEC) + one TREC ESC w/mixing option (no revo mix required on transmitter for this configuration)
A heading hold gyro + two ESCs (w/BEC) + transmitter (no revo mix required on transmitter for this configuration)
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.
See the section Section 23.6, “How gyros work” for more information on gyros.