RADIO CONTROL HELICOPTERS
Paul Tradelius 4302 39th St. West Apt. #5, Bradenton, FL 34205
LAST MONTH I had ideas to help progress with flying after hovering proficiency was attained. But some fliers suggested discussing basics that should actually be considered prior to hovering proficiency. And since the snow is starting to melt in many parts of the country (at least I hope so), many of you will be taking that new helicopter you have been assembling all winter out for its first test flight.
Although helicopter assembly manuals are very good now (they have improved greatly throughout the years), there are still some setup basics to check and understand before initial hovering attempts. A little more work on the bench now will save time and aggravation later at the flying field.
Basic setup vs. radio adjustments
Have a good basic mechanical setup rather than relying on the functions of a computer radio. When the servo arm is in the center (neutral) position, it should be perpendicular to the pushrod, and the pushrod should be connected to the appropriate hole in the arm. Use a hole closer to the center of the servo arm to decrease servo throw rather than decreasing the servo movement electronically. Setup guidelines should be in the helicopter instructions; reserve only small control changes in the radio to suit your particular flying needs.
Servo direction and throws
Make sure servo direction is set correctly, and set all throws at 100%. I have seen many new helicopters at fields, ready for their maiden flights, with servos operating in the wrong direction. This is basic, but it must be checked prior to flight after other adjustments have been made. Have the throws set at 100% (don't forget both right and left throw) so the helicopter will react equally in both directions. Many times people have come to me complaining that their helicopters would not turn properly one way or the other, only to find that the servo throw was reduced in one direction.
Servo arms and linkages
Use balls and links at the servo and bellcranks (instead of Z-bends) to reduce slop in the control system. Some manufacturers recommend Z-bends in pushrods because it's easy and saves the cost of balls and links. But the big problem is the size of the hole and how it wears with time. If the hole in the servo arm is not large enough, the pushrod will bind; if the hole is too big, there will be slop in the whole control system.
Wiring and routing
Bundle wires carefully and keep them away from moving parts or side frames where vibration could cause problems. When initially mounting servos and other components, I pay little attention to where I will eventually route the excess wires. Although helicopter instruction manuals usually show the servo layout in great detail, I often need to place the on/off switch in a different location or move the battery pack to adjust the center of gravity. Do these things as needed, then make the aircraft look as neat as possible.
I initially use tie wraps (cable ties) to secure the wires to the side frame where needed. The extra wires from servos, battery, etc., are folded over and held together with more ties.
When all of the wires are as tidy as I can make them, turn on the helicopter and move all controls to their extremes and look for anything rubbing against a wire bundle. One of my close friends in Texas recently lost a helicopter because a wire bundle rubbing against the side frame eventually cut the wire in two.
The antenna wire
The antenna is often the last wire secured to the helicopter, and most people give it very little thought. The standard wire antenna supplied with the receiver can give good signal reception, but the wire must be stretched out and secured to the helicopter to avoid getting in the way of the moving rotor system or hot engine parts.
A common technique is to stretch the antenna from the bottom of the helicopter to the bottom of the vertical fin or to the horizontal fin tip, and use a rubber band to keep tension on the wire as it's attached to the fin.
Take care not to use too many knots in the wire or to fold the wire over itself, because doing either can detune the antenna circuit. Using a rubber band presents the problem of the rubber band breaking and allowing the antenna to get tangled in the rotor system. Little things like securing the antenna wire can cause major difficulties if not done properly, so take extra time and study your particular helicopter and antenna arrangement.
Properly adjusting the tail rotor pitch
This is possibly the biggest problem a novice has when building a new helicopter. People call me saying that their helicopter just spins on the ground and no matter what control input they make, it won't stop. This problem can be caused by one of the following:
- Reversed tail rotor servo.
- Tail rotor pitch not set properly. With the radio on and the throttle stick in midrange position, there should be about five inches of positive pitch in the tail rotor. For clockwise-rotating main rotor blades, the tail rotor should be trying to pull the helicopter's tail to the left.
- Reversed gyro. To check this, move the tail rotor stick to the right and see which way the servo moves. Now pick up the helicopter and swing the nose to the left. The tail rotor servo should move slightly in the same (right) direction, trying to bring the nose back to the right. If the gyro is reversed, look for a reversing switch on the gyro. If one is not available, reverse the gyro upside down to cure the problem.
Main rotor blades won't come up to speed
This could be caused by a rich engine not producing enough power, but it is usually caused by too much rotor blade pitch. With the throttle stick in midrange position, the main rotor blades should have about four inches of pitch—any more will produce too much drag for the engine to handle, since the engine is not producing full power at midstick.
By closely following helicopter and radio instruction manuals and considering these points, most common problems can be avoided so you can really enjoy this challenging and rewarding hobby.
Transcribed from original scans by AI. Minor OCR errors may remain.
