Safety Comes First
5063 Benton Boulevard, Pace FL 32561
Glad to be back. I believe it's appropriate to begin this column with an apology for the sudden disappearance of my column about six months ago. As indicated by the Publications Manager in the June 1995 Model Aviation, I found out on very short notice that I had a new six-month job assignment with the United Nations in Croatia/Bosnia, which required that I give up writing for a time.
I survived the "experience" and eagerly returned home to my family and friends. I can honestly say that I enjoyed the opportunity to work for the UN, although I truly missed spending those lazy summer afternoons at the flying field with "the gang." Funny how being out of the country for long periods makes the homecoming that much sweeter. I'm glad to be back!
For those of you who wrote to me in my absence and provided SASEs, you'll receive a response very soon if you haven't already. Thanks for continuing to write, for your words of encouragement, and, of course, for the material you send.
I Learned About Flying From That:
This story comes from a concerned modeler who wanted everyone to know what can happen if you flip servo-reversing switches after starting the model. After reading the mail I received while away, it appears the following scenario has been repeated several times across the country—most often with computer radios.
The Weather Channel predicted good flying weather the next day, so the fellow hurried out to his workbench to plug his radio into the charger for a quick overnight charge. After packing the support gear into his car the next morning, he went back to unplug the transmitter and found it completely discharged—it seems he had left the transmitter on all night. No problem, because another transmitter on the same frequency still had a good charge, so off to the field he went.
He went through his usual preflight, especially the range check, walking 150 feet away to verify the controls still moved. They did, so he fueled up and started the engine. After warming up and checking the traffic pattern he taxied to the flight line and began takeoff. To his dismay, when he pushed the stick right the plane turned left—he had apparently forgotten to check for reversed controls.
Since the engine was idling and the plane was stationary, he thought he could quickly reverse the rudder without shutting everything down. He believed the rudder was on channel three, so he reversed that channel—only to discover, to his horror, that channel three controlled the throttle. Before his muddled brain could react, the plane became airborne, promptly lost power, and impacted the ground. Fortunately the damage wasn't too severe, though it ended his flying day.
Later a mind-numbing thought occurred: what if the plane had been pointed toward the flight line instead of away from it? As it turned out, only one fellow flier at the field observed the situation—and the potential victim of the carelessness.
So what did I learn from this experience?
- Charge radios correctly — and make sure they are off before beginning the charge.
- Always check that control surfaces move in the proper direction.
- If anything is discovered to be wrong during preflight, correct it before attempting to fly. Once corrected, conduct another preflight before flying.
I've talked about the perils of flipping servo-reversing switches in the past, although the focus in recent years has shifted to computer radios. Always conduct a thorough preflight and range check of the aircraft before flying. This includes checking nuts and bolts, correct servo operation, a proper range check (with the antenna collapsed if applicable), and verifying antenna condition. If something doesn't seem right, be sure—enlist the help of another modeler; a second set of eyes can catch what you missed. A personal rule I follow is: stay on the ground if you find something wrong before flying. It's a pain doing homework before leaving the house, but better that than letting Murphy follow you to the flying field.
It Fell Off:
Another letter I received described the aggravation of suddenly seeing something drop from the airplane while flying. Was it a servo, muffler, or wheel? Could the pilot still control the airplane? Here is the story:
A few weeks ago, a couple of us were at the field getting our planes ready. I was a little slow with my preflight checks and was still messing around with my plane when another club member was taxiing out. I paused to watch the takeoff. The takeoff was nice and smooth until, right at liftoff, I noticed a small object bouncing along the ground below the now-airborne aircraft. I was puzzled until I heard the pilot exclaim, "I just lost a wheel!"
Fortunately, I had sufficient presence of mind to follow and retrieve the wheel. The pilot then had the problem of landing a plane with only two of its three wheels. A low flyby revealed a bare axle where the left main wheel used to be. He had to decide how to position the plane on landing to minimize damage from the exposed axle scraping the dirt at 20 mph. He correctly elected a slow approach with the right wing low, touch down as softly as possible, and hope for the best.
He executed the landing masterfully. Because he had a sturdy ship, all that happened was a deep furrow in the runway and a scuffed right wing from a substantial ground loop.
What did I learn from this experience? Now every one of my preflights includes a wheel-collar check for tightness of the screw.
Additional points when installing wheel collars:
- Grind a flat spot on the axle to give the screw something to bite.
- Consider applying a drop or two of permanent Loctite (or similar compound) to the threads of the screw during installation to keep it from working loose in flight.
PET Containers
Since I wrote about PET containers almost a year and a half ago, I've been getting a lot of mail—some asking for clarification and some pointing out other areas where preflight checks can prevent problems. Perhaps the most common letters described being fooled by servo-reversing switches after starting a model (see above). Others told of numerous PET failures that resulted in total or near-total devastation of models.
To date I'm not aware of anyone being injured during a PET explosion, although the possibility of injury from shrapnel is obvious. Trust me when I say I understand how devastating shrapnel can, since I witnessed the effects first-hand while overseas.
To recap how these containers are produced, and to what tolerances, here is a review of a past conversation with Jerry Broderick, Quality Control Division of the Orlando-based Constar Company (PET manufacturer):
A very hot (about 600°F) plastic material is blown down a tube into a specific container mold. Since the mold is water-jacketed (cooled), the plastic quickly cools, creating a usable plastic container (very simplified).
Random samples of various-size containers are then chosen for quality control testing and forwarded to a burst-testing chamber. Containers selected for testing are first filled with water and then pressurized to 150 psi. If they don't burst, the sampling of that specific lot is considered satisfactory and they're forwarded to bottlers for use. When filled by bottlers, containers are pressurized with nitrogen to 73 psi and then filled with product.
Jerry added that experiments with containers at pressures above 150 psi always resulted in violent failures and damage to their testing chamber. As he described it, "The access door to the burst chamber is covered by a 1/4-inch-thick PVC sliding hatch. When a container fails (filled with water), the door is usually blown to bits."
Based on his experience with the chamber, Jerry was not surprised to learn about models being turned into confetti when a PET container fails after being filled with compressed air. As mentioned previously, PET containers were not manufactured to be used as pressure vessels for model aircraft.
That's it for this month. Until next time, keep the wheels on the bottom and have a happy holiday season!
Transcribed from original scans by AI. Minor OCR errors may remain.
