Choosing a RC Helicopter

Choosing a Helicopter      
THE BUDGET
For beginners into this hobby, the first question that comes into mind is which helicopter to buy. This is very often associated strongly with the budget available. A word of warning is that this hobby is not cheap by any means. Even if you find purchasing your first helicopter affordable and cheap, you will soon find that repair and maintenance costs will amount to quite a bit. Of course you will also soon learn that the “itch factor” will kick in and you will find yourself spending money on parts, upgrades or even new helicopters just because this hobby is so darn addictive. Anyway you have been warned. Now is the time to read on and enjoy!
Also please keep in mind that even the most experienced pilots will have a crash or two now and then. This could be due to sheer cockiness or lack of concentration or even mechanical failure when flying a helicopter. Replacing parts on a precision machine could really run up your budget. If you are cost conscious then a good place to start would be a .30 size engine helicopter with collective pitch and good availability of parts.
    

CHOOSING THE RIGHT HELICOPTER
 Raptor 30Deciding on your first helicopter can give you a migraine. You can basically choose from two types of helicopters; a collective pitch or a non-collective pitch machine.
A collective pitch machine basically means that the pitch of the rotor blades changes according to your throttle/pitch stick position. A non-collective pitch machine means that the blades are of fixed pitch and the lift of a helicopter is basically controlled by increasing or decreasing the speed at which the rotor turns.
To the beginner, a collective pitch machine is harder to set up but is easier to fly because it can maintain constant head speed all the time which means control is always there regardless whether you are ascending or descending. The collective pitch machine is also more expensive due to more moving parts and the requirement to have an added servo for pitch control. A collective pitch machine is always recommended for beginners but if budget is a limitation factor, you can always learn to fly on a fixed pitch machine like I did on a “Mini Dragonfly”. Additionally the collective pitch machine will allow you to develop your flying skills without having to upgrade from a fixed pitch machine later on.
 

    Quick Lesson on Head Speed & Control: The faster a set of rotor blades spin, the better response you will have from the cyclic controls. For a collective pitch machine, you can set the rotor to spin at a certain fixed rate e.g. 100% throttle and yet have the helicopter remain on the ground by having 0 degrees of pitch on the blades. Normally this does not happen but it just basically illustrates how a collective pitch machine is different from a fixed pitch machine which will take off even before you hit the 100% throttle position. You can never change the throttle & pitch combination. To descend on a Fixed Pitch helicopter, you will have to reduce throttle to reduce the rotor head speed which is equivalent to lift. This in-turn will effectively reduce the amount of cyclic control on the helicopter thus making it more sluggish. This is the main reason why it is easier for the beginner to learn to fly on a Collective Pitch Machine.

In addition to the helicopter type (Collective & Fixed Pitch), the size of a helicopter will dictate the stability and reaction time for each model. Generally the bigger the helicopter, the more “stable” the craft, especially in stronger winds. Small micro / mini electric helicopters will definitely be more twitchy as compared to the larger gas powered ones. The sheer weight of larger machines normally weighs down the machine making it more sluggish and allowing beginners to have more reaction time. However larger machines are by no means sluggish as the power plant is normally more than enough to make them perform the wildest acrobatic maneuvers. The ability of each helicopter to perform stunts depends on the design of the craft in addition to the power plant it has.
 

THE POWER PLANT (ENGINE / MOTOR)
OS .91 Heli Engine An engine for a helicopter is similar to that of a model aircraft engine. The only difference is the larger heat sink on top of the engine for better cooling. Model Engines normally will require model fuel and a host of other accessories to start, run and maintain the engines (e.g. electric starters & etc)
Motors that comes with electric model helicopters are normally “Brushed” Motors. These tend to wear out relatively quickly and you will find that you will need to upgrade to “Brushless” motors (along with brushless speed controllers) if you’re really serious about flying and wish to put the helicopter through its many hours of flight. For better long lasting flights, people normally use lipo (lithium polymer) batteries as opposed to Nicad / Ni-MH batteries. Other accessories like a special lipo battery charger will be required plus the batteries can be just as costly as model fuel since they tend to damage easily under excessive current load or drainage.
 

THE RADIO & RECEIVER
JR Propo PCM 9XII Controller Helicopter Radios are different from Aircraft radios in many ways. The most obvious is the capability of Helicopter Radios to electronically mix certain functions like pitch and throttle (via curves or points), tail rotor and throttle via Revo Mixing. Most radio these days have different modes that allow a modeler to switch between Airplane, Helicopter and Glider Modes like the JR 9XII Radio that I have. Most radios also hold quite a number of model memories which means you can use the same controller with different models that you own. All you would need are extra sets of receivers and servos.
Different radios come with different servos & receivers. Some even come with nicad battery packs while others don’t. It is important that for helicopter radios to have servos with output shafts that are ball-bearing driven to reduce friction under heavy constant usage & vibrations from a helicopter. Speedy servos are also important for increased response times especially for the tail rotor control which is normally connected through gyros. Many helicopter radios come packaged with five ball bearing-ed servos and a large batter packs to handle the extra load and movements on servos.
Futaba S 9252 Hi-Torque Ball Bearing Servo The things to look out for and to have in a helicopter radio would be:

  • Ball-Bearing Servos (5 Servos are needed: Throttle, Collective Pitch, Tail Rotor, Cyclic Left/Right, Cyclic Forward/Backward)
  • Large capacity receiver/servo battery packs 1200mah or more
  • Minimum 5 points Throttle & Pitch Curve settings
  • Throttle Hold Capability
  • 3 Flight Modes (Normal, Idle Up 1 & Idle Up 2)
  • Revo Mixing
  • PCM / PPM Receiver

 

GYROS
 Just like other equipment on board a helicopter, the gyro is perhaps the most important aid equipment that will help a modeler pilot his helicopter. A gyro is basically an electro-mechanical device used in a helicopter to help stabilize the tail of a helicopter during flight. As with all gyroscopes, it aids by detecting unwanted movements around the yawing axis. An unwanted right handed swing of the chopper will be countered by a left input of the tail by the gyro to maintain heading of the chopper & vice-versa for a left handed swing. Swings about the main shaft axis normally occur when a helicopter powers up or down due to the torque of the motor and rotor blades.
A gyro is a device used to correct such unwanted swings and is normally attached electronically in between the tail servos that control tail pitch and the receiver. A sensor, either mechanical or peizio in nature, will measure unwanted change in yaw of the aircraft and will correct the situation by increasing or decreasing the tail rotor pitch to stabilize the movement.
Flying a helicopter without a gyro will definitely be a handful and quite a challenge even to more experienced pilots.

Leave a Reply

Your email address will not be published. Required fields are marked *


Notice: Undefined variable: post_ID in /home/opp/public_html/wp-content/plugins/anti_spam_image.php on line 33