Radio Control: Sport Aerobatics
Ron Van Putte
When you went out to the flying field the last time, did you just take everything off charge, load the car, drive to the field, unload, fuel the airplane, turn on the radio and take off? That's what I often do. However, we're asking for trouble when we skip a complete functional and safety check.
When is the last time you performed a full system inspection? The reliability of today's airplanes, radios and engines has lulled many of us into complacency. When I started in this hobby more than 25 years ago, a "good" day meant flying once or twice and bringing the plane home in one piece. Back then things routinely failed — relays, escapements, batteries, vacuum tubes, connectors, switches, engines, propellers, fuel proofing, rubber bands and radio interference — and those problems taught us to check everything before flight.
Today nearly everything works most of the time. Coupled with a natural reluctance to find anything wrong that might delay flying, this leads many to skip preflight checks until a sudden failure causes damage, lost equipment, or injury. I suspect many of those failures would never occur if periodic inspections and preventive maintenance were performed.
A good periodic inspection should be complete but fast and painless. Use a checklist so nothing is missed. I prefer working from the front of the airplane to the back. Below is a generalized checklist you can expand for your own aircraft.
- Engine
- Propeller
- Fuel tank and plumbing
- Radio system and batteries
- Servos and connectors
- Control linkages
- Control surface hinges
- General structure
Engine
- Verify all engine screws are tight.
- Inspect for leaks around gaskets and the muffler.
- Ensure the throttle clevis is tight on its threaded section — worn threads can deteriorate quickly and lead to loss of throttle control.
Propeller
- Check for cracks, missing pieces or other damage.
- If you sanded a blade to balance the propeller, confirm the repair and finish haven't allowed fuel to soak in and weaken the blade.
- Replace props that show any compromise; prop failures are common sources of accidents.
Fuel tank and plumbing
- Ensure the fuel tank is airtight.
- Inspect the stopper and fuel line for cracks, swelling or stickiness.
- If you use surgical rubber tubing, note that some fuels attack it and make it gummy; dissolved tubing can clog the needle valve. Silicone tubing is preferable.
Radio system and batteries
- Perform range checks regularly to detect deterioration or detuning.
- Check battery capacity periodically to find weak or failing cells.
- In a quiet shop, move the transmitter stick slowly and observe for smooth servo operation; jerky movement indicates dirty potentiometers or other issues.
- If a channel shows jerky operation, swap a known-good servo into that channel. If the problem moves with the servo, the servo is at fault; if it stays in the channel, the transmitter pot is likely the cause.
- Clean or service pots and refer to published maintenance articles (for example, MA, June 1979) for guidance.
Connectors and servos
- Inspect connectors for frayed wires and ensure contacts are bright and clean.
- Pay special attention to aileron and retract connectors, which are more exposed to dirt and fuel residue.
- If contacts look dull, use tuner cleaner and work the connectors back and forth to clean them.
- Check servo and servo tray screws; vibration can loosen them and cause trim changes or total control loss.
Control linkages
- Control linkage failure often results in a crash regardless of radio quality.
- After rough landings, inspect pushrods for fractures; they can fail from landing shocks.
- The weakest points are usually the threads where clevises screw onto rods or couplers. If a clevis wobbles, replace the clevis, coupler or rod as needed.
- Also inspect clevis pins and horn holes (rudder clevis and horn are especially vulnerable). Lock the pushrod and wiggle the control surface; any play indicates wear that should be corrected.
Control surface hinges
- Hinges are susceptible to engine vibration, aerodynamic loads and landing shocks.
- A departing rudder, elevator or aileron is very dangerous; detect and replace weak hinges before failure.
- In some cases a single hinge failure may jam a surface and be preferable to a complete loss, but prevention is best.
General structure
- Aircraft suffer wear from everyday flying. Inspect the airframe for damaged areas that can suddenly fail: wing failures, broken rubber bands, torn tail surfaces, etc.
- Many club newsletters report crashes that could have been prevented with a quick structural check.
Performing periodic inspections takes far less time than repairing or rebuilding a crashed airplane. I’d rather spend money on fuel and glow plugs than replace equipment damaged by preventable accidents.
Club involvement and responsibility
Club funds and facilities are community resources. A short excerpt from the Carrier (East Bay Radio Controllers) illustrates the point: four members noted the club had roughly $3,700 per year to spend, yet many active members don’t express their preferences. If you don’t take part, the active members will decide how to use the money. Speak up: it’s your club, your money, and your flying field.
Do the checks. Use a checklist. Fly safer, save money, and have better days at the field.
Transcribed from original scans by AI. Minor OCR errors may remain.
