RADIO CONTROL: HELICOPTERS
Paul Tradelius, 6704 Santiago, Ft. Worth, TX 76133
By now most of the country is out of the grips of winter, and our thoughts are again returning to flying helicopters. If you did not perform a thorough end-of-flying-season maintenance inspection on your favorite machine, now is the time to take a close look at it. Even for those who have good flying weather year-round, it’s a good idea to give your helicopter a careful inspection to make sure it’s ready for summer.
Not every helicopter will be the same or require the same attention in every area, but some basics apply to all helicopters.
Bearings
Helicopters use many bearings to provide a smooth rolling surface at high rpm and under great load. I’m no different from anyone else: I just expect them to continue doing their excellent job with only a few drops of oil now and then. If your helicopter has given you one or more flying seasons of service, now may be a good time to inspect those bearings and replace any that are worn or feel gritty as you spin them.
Before you start disassembly, be aware that you have two maintenance alternatives:
- Disassemble the various parts containing the bearings, then decide which (if any) need to be replaced. The advantage is you only purchase the bearings that are needed; the disadvantage is you must keep parts of the helicopter disassembled until the new bearings arrive.
- Preorder the bearings you think will need to be replaced and have them available as you work. I prefer this option because I know I will have everything ready when I get a chance to tear the helicopter down. If there are bearings I decide not to change, I keep the new ones as spares.
Some people prefer to change the high wear/load bearings whether they appear to need changing or not, believing this prevents later problems and keeps the helicopter flying longer in top shape.
The first thing I do is look at the blow-up diagram of the helicopter and identify the areas that require disassembly to reach the bearings. Once I identify the bearings I think will need replacement, they can be ordered from the manufacturer/distributor or from a bearing supplier such as Boca Bearing (7040 W. Palmetto Park Rd., Suite 2304, Boca Raton, FL 33433). Owner Allen Baum is very knowledgeable about bearings; telling him the make and model and the part numbers from the blow-up diagram usually gets you exactly what you need.
Some pilots also disassemble their engines periodically and replace those bearings as well; Allen carries nearly all the bearings we will ever need.
Batteries
Radio equipment has come a long way in recent years, giving us computer technology in programming and reliability, but all is lost if the batteries let us down while flying. If you have not checked your transmitter and receiver batteries lately, here are two tests that will increase your confidence in them.
#### Cycling test Take your fully charged battery pack and discharge it at a known rate. From the time it takes to discharge, calculate the capacity of the pack in mAh and compare it to the stated capacity. If the capacity checks out, everything is fine.
If it does not check out and you are handy with a soldering iron and can get exact replacement cells, you may inspect each cell with a voltmeter to find defective ones and replace only those cells. My view is more pessimistic: if one or more cells are bad, the others are soon to follow. I usually cut the connector off the pack and either use the pack as a doorstop or bring it to a recycling center that accepts batteries.
#### Dendrite check Dendrites are tiny whisker-like growths in a battery that cause internal shorting. An easy dendrite check is:
- Charge and immediately cycle the battery pack to determine its capacity (as above).
- If the battery tests good, fully charge it again and let it sit a few days. Ni-Cd packs typically self-discharge about 1%–2% per day; after five days they should lose roughly 5%–10% of their capacity.
- After five days, cycle the pack again to determine its capacity. If it’s about 90% of your previous reading, all is fine. If it shows only about 75% after sitting five days, you likely have dendrites.
Opinions vary on whether a pack with dendrites should be retired; the decision is yours. Some believe dendrites can be “cut” by quick-charging or charging with a pulse charger such as the Micropace units, but replacement is often the safer choice.
Because batteries have become the weakest link in our radio systems, several new products have come on the market to cycle and analyze batteries and detect problems before they cause an inflight failure.
Battery products and equipment
- Micropace Inc. (Box 648, Northville, MI 48167) — Micropace offers a compact AC unit that discharges batteries at a regulated 300 mA rate down to 1.1 volts per cell, then automatically switches to charge mode (selectable at 55 or 120 mA) for 15 hours and then to trickle charge. The Micropace uses a light system that blinks to display battery capacity down to 1 mAh instead of a digital readout.
- Hitec RCD, Inc. (10729 Wheatlands Ave., Suite C, Santee, CA 92071) — The Multi Charge-A-Matic works from a 12-volt DC source (car battery or cigarette lighter) and can charge everything from a 4.8-volt pack up to a 12-volt field battery. It is an automatic peak-detection charger that allows you to choose charge current and reverts to trickle charge when batteries are full. The unit also offers an Efficiency Tester that cycles/discharges at selectable currents and displays efficiency via multicolored LEDs.
- SR Batteries (Box 287, Bellport, NY 11713) — SR makes a fine line of batteries and support equipment and is well known for high-quality Ni-Cd batteries. SR also manufactures the Smart Charger/Cycler, which runs from a 12-volt source (or AC-to-DC converter), charges 2–28 cells with both peak and temperature detection, and features an LCD display to adjust fast/slow charge and discharge functions. It’s state-of-the-art for battery testing.
- Vencon Technologies Inc. (5 Graymar Ave., Downsview, Ontario M3H 3B5, Canada) — Vencon offers the Ultimate Battery Analyzer, which will charge, fast-charge, and revert to trickle charge while plotting results on your computer for saving or printing. It provides many parameters to suit particular batteries and helps you spot problems before they can cause an in-flight failure.
Although bearings and batteries are critical to proper helicopter operation, a routine maintenance and lubrication program is also needed to catch potential problems before they develop into a mishap.
Start at the front of your helicopter and look closely at each item for tightness and wear. Items with bearings or slides need a drop or two of oil periodically to maintain smooth operation. It doesn’t matter much whether you use a high-priced oil with additives or plain 3-IN-ONE oil—just use something.
A final point on preventative maintenance: inspect your helicopter carefully while you clean it. If something does not look right, it probably isn’t. Looking and poking will often find screws or bolts that have worked themselves loose or parts that are bent or worn and should be replaced.
These maintenance tips do not take a lot of time or effort, but they will help you enjoy the full flying season that is right around the corner.
Transcribed from original scans by AI. Minor OCR errors may remain.
