RADIO CONTROL HELICOPTERS
Paul Tradelius, 4620 Barracuda Dr., Bradenton FL 34208; E-mail: [email protected]
SPRING HELICOPTER INSPECTION
This is the time of year many of us like to see: the worst of the winter is behind us, and we're planning a new year of flying. Before you dust off last year’s pride and joy, check to make sure your helicopter is ready for another summer of fun flying.
Checking your helicopter doesn't take much time, and can easily be accomplished on a rainy afternoon when there is nothing better to do. A little time spent now will pay big dividends on the flying field. Here are some of the major areas I pay particular attention to.
Canopy
You wouldn't think the canopy would require much inspection, or that it could affect the helicopter's performance, but there is more here than meets the eye. I have seen canopies that were cracked, bent, crooked, etc., making the helicopter all but impossible to handle in fast forward flight.
- The canopy is the first thing the air "sees" as it hits the helicopter; try to have the canopy on straight and in an aerodynamic shape.
- Check the canopy-mounting system to make sure it's secure and in alignment.
- Worn rubber grommets, enlarged mounting holes, or poor-fitting parts can cause the canopy to detract from performance and appearance.
For mounting holes that have worn to an unacceptable size, try patching from the inside with fiberglass cloth and resin. After the initial layer cures, add another layer or two for additional strength. Drill the correct-size hole to fit the new rubber grommet.
Blade-covering material (or simple shelf paper) can also be used to give your canopy a different look for the new year. This material is inexpensive, easy to apply, and can be cut into any design shape you like.
Servo Tray and Servos
Many years ago, wooden servo trays were glued together and bolted to metal side frames. The wood would crack and cause servos to move out of position. Most helicopters now use molded servo mounts to eliminate this problem, but the servo mounts should still be checked to make sure they are securely mounted to the main frame.
- Try to move the servo tray from side-to-side by grabbing it and checking for any movement.
- Look for any silver dust—small bits of aluminum worn from a loose screw.
- Retighten all screws holding the servo tray in position.
- Servos should be securely mounted to the tray without being so tight that the rubber grommets lose their shock-absorbing function.
- You should be able to rock the servo slightly from side-to-side when you apply pressure to the servo wheel. (A loose servo will not provide accurate control.)
Pushrods and Controls
- Disconnect the pushrod from each servo and move the pushrod back and forth as the servo would, looking for any binding or tight spots.
- To do this accurately, make sure the rotor blades are extended to their normal flying position.
- A little lubricant where the pushrods go through the guides is helpful.
Engine, Muffler, and Vibration
The engine and muffler are sources of high-frequency vibration in the helicopter. Effects from vibration can usually be seen as foam in the fuel tank, and should be checked throughout the flying season.
- Loose bolts or parts are usually easy to spot by looking for silver oil residue from worn aluminum.
- Use an extra lock nut on engine bolts when possible, and plenty of Loctite®.
- Mufflers that consist of several parts have a tendency to come apart; JB Weld® does a good job of keeping mufflers together after a thorough cleaning with lacquer thinner.
Lower-frequency vibration is produced by the head and rotor blade system. This usually shows up as a vibrating canopy, tailboom, or skids.
- Make sure rotor blades are free from all damage; replace if there is any doubt.
- Damaged rotor blades can come off in flight and cause serious damage—keep blades in good condition.
Rotor Head and Bearings
The head doesn't take much punishment during normal operation, but the truss roller bearings are critical to proper blade movement as the blades change pitch throughout flight.
- Disassemble the head and lubricate the thrust bearings and other major parts of the head.
- Refer to your blow-up diagram or building instructions and make sure thrust bearings are installed correctly—there is a front side and a back side, and incorrect installation will greatly affect flight performance.
- All bearings should be lubricated and the gear mesh checked.
Clean old fuel from the tank and carburetor, and lubricate the tailboom as needed.
If everything looks good, you will probably not need to rebalance the head and blades, but since you have come this far it won't take much more time to do the job right. A digital gram scale and a rotor balancer give the best results for balancing.
Tailboom and Tail Rotor
The last part to inspect is the tailboom and rotor. Depending on the type of tail-rotor drive system, the idea is to inspect, lubricate, and make sure everything is tight.
- Take the tail rotor apart and inspect the gears and bearings for wear.
- I drill two holes in the tail rotor case, plug them with small grub screws, and use the grub screws to lubricate the tail rotor gears throughout the season.
- By taking out both grub screws I can force grease into one hole until it starts to come out of the other, ensuring the tail rotor is full of grease; the grease liquefies very quickly in warm weather.
Final Checks
- When you have everything inspected, charge the batteries and give the helicopter a range check.
- Make sure the rotor blades are in flying position and the canopy is on.
- Try to have the helicopter on a stand and above ground.
- Have a friend watch the servos as you walk away, making sure you get the minimum range as specified for your radio.
- Cycle the batteries to make sure they are ready for another season. Batteries have become the weakest link to happy flying, so replace them if there is any doubt about performance.
Your helicopter may have other parts that require more inspection prior to a summer of flying, but this should cover the major portions and get you safely back into the air.
Transcribed from original scans by AI. Minor OCR errors may remain.
