Gary A. Shaw
Safety Comes First
5063 Benton Boulevard, Pace, FL 32571
Electrics Spring to Life
For those who enjoy flying electric models, one of their greatest advantages is obvious: they start with the push of a button. Equally obvious — and potentially dangerous — is one of their greatest disadvantages: they start with the push of a button.
Push the button and the model is "armed" for flight. Push it again and the model is no longer armed. Simple enough, but the simplicity can create a serious safety concern. Unless you have the appropriate transmitter in your hands and/or know the on/off switch positions of every airplane around you, it's nearly impossible to tell if a buddy's model is armed. If someone leaves a model on in the pits, the next person using the same frequency could suddenly find themselves controlling two aircraft.
A Real Incident (Dick Miller, Wernersville, PA)
During a recent KRC event, an elderly individual landed his four-foot plane rather hard. After retrieving it, he gave it a cursory examination for damage. Finding none, he proceeded to stand over the plane with it between his legs and ran the batteries down to almost complete exhaustion (motor running wide open). He then discovered the wooden prop was very badly fractured during the landing — lucky it didn't separate in his face.
But what followed was even more incredible. Leaving his plane positioned behind the flight line, he returned his transmitter to the impound area and left the immediate area without further contact with his plane (he didn't shut it off). Shortly thereafter, his motor came to life and the plane headed for a group of people standing well behind the flight line. The channel was now being used by another pilot, who suddenly found himself controlling two planes.
Both myself and another individual literally dove for the runaway plane and managed to turn the receiver off before any damage was done. "That's the second time he's done that today," was the comment from my fellow co-grabber.
The happening is no reflection on the operation of KRC — the affair was well run, the impound area was well staffed, and flight line managers were located at all pilot stations. We just have individuals who simply forget. I've done it myself. The advantage of electrics — that they start at the push of a button — also makes them very dangerous.
No safety switch was used on the craft in question. I doubt that safety switches alone would solve the problem; they can be forgotten too. So I began thinking of ways to eliminate this problem.
Proposed Solutions
Dick suggests two simple, inexpensive devices that can greatly reduce the risk.
- Fail-safe motor-control latching circuit
- All parts are available from Radio Shack.
- Additional weight is negligible for modern models.
- No separate safety switch is required; control is via the motor control signal and supply voltage.
- Operation:
- Turn on the transmitter, then the receiver (normal operation).
- Push the fail-safe button to activate a relay and connect power to the motor control.
- The relay stays energized as long as the transmitter is on and does not interfere with control operation.
- After landing, if the receiver is inadvertently left on, turning off the transmitter removes the signal relay; the relay drops out and electrically disengages the motor.
- Dick attached detailed schematics and has built a prototype on 1/16" board using Radio Shack parts. The unit reportedly weighed about nine grams. Initial success was reported with an Airtronics VG4R system, but Dick cautions that more testing is needed to ensure compatibility across radio brands and to investigate potential null-signal areas.
- Audio-visual indicator (LED/Piezo)
- Uses a combined LED/Piezo element to blink and beep if an aircraft receiver is left on.
- Extremely light and uses just three inexpensive components.
- Installation is simple: three components on a connector wired together and plugged into an open receiver channel.
Dick promised updated schematics and testing results of both ideas. If you'd like a personal copy, send an SASE to:
Gary Shaw 5063 Benton Boulevard Pace, FL 32571
That's the short and sweet of it for this month. Looking forward to receiving some mail at my new address — should be a little more seasonal and much less crowded!
Transcribed from original scans by AI. Minor OCR errors may remain.
