Stuka Stunt Main Forum · 20 of 20 known posts recovered
Tom McClain
There have, unfortunately, been many. The safety record of C/L is actually rather appalling. Someone gets killed every few years by flying into power lines, the last one I am aware of being a guy who used to fly out at Alameda showing his grandson/nephew how to fly in the late 90's.
Of course the most famous was the flight into power lines that led to the lawsuit that resulted in most C/L accessories being discontinued, particularly the Hot Rock.
The injury record is also poor, the Joe Armstead incident at Whittier Narrows being notable for it's wide-ranging scope.
Brett
First, electricity is generated when either a magnetic field is moved past a conductor, or a conductor is moved through a magnetic field.
It's a known fact that electricity moving through a wire establishes a magnetic field around the conductor, the higher the voltage the bigger the magnetic field around that conductor becomes.
Now, here we come, flying our tethered planes, with steel lines, excellent conductors. So, there's a nearby high power line with that rather large magnetic field being induced around the conductors. The tethered plane flies through this magnetic field, and we have now made our plane and wires part of a generator system. Remember, a conductor moving through a magnetic field will generate electricity. How much depends on two things, the stregnth of the magnetic field, and the speed the conductor moves through this field. The hapless pilot, is now holding the end of the conductor, and the only way the charge can ground is through him, or her.
Approaching thunderstorms aparently either have a magnetic field, or are carrying an electrical charge of it's own some distance from the storm itself. We've all experienced a static jolt from this condition. I'm sure there are other cases, as we've also all been shocked in clear dry weather as well.
I was once told that if we could harness the difference in potential between the earth and the upper atmoshere, we wouldn't need any other power source. This is probably what is happening when we get "static" shocks while flying. You may have noticed that the main safe thing to do when getting static shocks is to fly low and run out the fuel.
The point of this is to alert as to why we don't have to touch the wires to get in trouble, rather just flying too near power lines can cause harmful, if not leathal electrical injury.
John
Gents,
In regard to hydro wires, I have the following to relate. This is a cut and paste from some mail I sent to an r/c flier. The topic of the day was carbon fiber mat and push rods. I made light of the fact that they are electrically conductive, ...I see now that my closing "case history" could have ended in a much different way. It also brought home the warnings as printed on the kit instructions i.e.: "Don't fly near, or in the vicinity of electric wires and hydro poles." Read on:
Greg,
I intercepted your mail via remote access from the work place desk top, ..gotta love this computer stuff, ..to bad there only a fad (?), ha ha ha.
Electro conducto: Yep I think that you are correct in your thinking. I've heard it mentioned before with r/c fliers and their use of carbon fiber push rods, (another fav. of us c/l guys btw.) . These items can play with your RF transmissions and stuff I believe. I'm not sure of the required "proximity" that the problems arise at, but hear tell they are there.
General rule of thumb on conductance: If a conductor (carbon fiber) is cutting (flying through) the lines of flux of a magnetic field, a EMF (electromotive force i.e.: electricity) is being generated. The faster the lines of flux are cut, the higher the generated EMF. The stronger the magnetic field, the more EMF generated. Been here, done that yet again, and am still here to tell about it.
Case history: 1977 flying a 42" Carl Goldberg Models "Shoestring" Stunter in a school yard, ...our normal flying site at the time. The yard is ringed by electrical poles carrying I don't know what kinda voltage. Weather conditions where just right, humidity, temp, etc. As I'm flying around my brother (crew chief) is jumping up and down and pointing at me. I look all around but can not see what he's so excited about. "YOur hair, ..YOUR HAIR is STANDING STRAIGHT UP!" he says. I put my hand near my head, and sure enough it's out like a pin cushion. About this time I start to feel shocks through the handle and my hand. We fly on seven strand stainless steel cables, 60ft long in this case. The handle also has a steel cable that contacts the palm of my hand. As the flight progresses the shocks are getting both stronger, and coming more often. Lucky for us we also brought a large tee shirt, ..one of dads old ones, to the field as a wipe down cloth. It took bro three tries but he finally manages to throw the tee into the prop of the Shoe as I bring it by at shoulder height, ..the engine stops, and it glides (kinda) to earth unharmed, ...my hair is still standing up when I land the thing. That ended the flying for the day. Later on I learn about mag fields, and conductance etc. What I think was happening was we were cutting the magnetic field coming off the hydro poles and wire that surround the field. We flew here all the time, approx 25 yards from any electrical poles or wires and never had a problem until that day. Mom always said I was a well grounded guy, ..go figure.
Tony
Second story to relate: We must protect them from themselves: While flying a SIG Twister (the one pictured in the fuselage thread in fact) I was mobbed by a Cub Scout Troop that had just finished up there den meeting at the local park. With the meeting over they all rushed toward the airplane now flying in circles in the middle of the field. They had enough sense to stop before reaching me, ..but the bulk of them were inside the flight circle by 5 or 10ft, ..sitting down (thank you lord) , facing away from me, and watching the plane go by over their heads from inside the circle! I've never seen anything like this in my c/l history, ..I'd never even thought to do this as a kid myself. Just seemed to make more sense to me to stay clear of the airplanes flight path and lines. Perhaps a "no brainer" for most of us, but there you have it. The un-knowing having no idea about the possible dangers of the spectacle. The ground crew got them all moved in short order, but I was amazed none the less.
Tony
Several years ago, Mike Rogers was flying one of his 60 Patternmasters. I was outside the circle with I believe Jim Borelli, Bob Lampione and Hank Forbes. Engaged in conversation, all four of us failed to notice a man in his early twenties, i.e., not a child, who had walked into the circle. Mike had finished his pattern and was flying high, so he also didn't notice. When we finally saw the man, he was half way to the center! Of course we shouted at him and got him out. The man explained that he just wanted to ask the flyer a question.
We cannot assume that people, adults as well as children, realize the potential dangers of our models.
That was Joe Armstead's accident. I think Keith knows more about this than I do, but I think I have the basic outline right.
A speed plane (I think D, but maybe B) had been wrecked and "repaired" using 5-minute epoxy to hold the monoline unit in. It came loose in flight, flew through a toolbox, then through Joe's lower leg. This pulverized both bones in the lower leg. Someone at the field was a orthopedic surgeon (Rudner?), which probably helped save him from bleeding to death. They eventually re-connected the remaing ends, then put it in traction for years to cause it to grow to normal length. It was amazing to think he kept his leg. Reportedly, he's fine now, but he doesn't fly model airplanes any more.
The model had reportedly passed the pull test before the flight, but came loose when the controls pulled out.
Several effects of this - the fence at Whittier Narrows, the "I won't sue AMA" disclaimer, the catch fence requirement, and indirectly, the "line size boost when the record gets over 200 mph" rule. The AMA peformance during this incident was not entirely satisfactory, in my opinion, but it's water under the bridge.
Brett
Let me relate the facts surrounding a nearly very serious or possibly fatal accident occurring at a contest I was attending in Rome Georgia. I had made my first flight and had taken my model off the circle and sat it down where everyone else had been rolling in their lines. I had rolled in my lines and was bending down wiping oil from the tail section of my plane. At the same time John Simpson was starting his takeoff for his first flight across on the other side of the circle. I wasn't paying any attention to John. It seems that he had moved to one side of the circle so that his model would completely miss some landing tiedowns on the aircraft parking area we were using. Unbeknowst to me, it was in my direction about 10-12 feet. I thought that I was completely clear of any flying areas because several people had been sitting exactly where I was wiping down my plane and no aircrart approached anywhere near them. Well, to get this story a little shorter. While doing my wiping I heard a screaming Aero Tiger .36 coming from behind me. When I heard it making a lot more noise than it should have I instinctively ducked forward to get as low as I could. On my way forward I was struck in the back around the left kidney area by Johns' inboard wing. His plane then bounced over my right shoulder with the prop of the spinning Tiger .36 just barely missing my ear. I wasn't sure if I had been hit by the spinner or propellor or not, and was in a good bit of pain in my lower left back around my kidney. After being inspected by bystanders, I was found to have a minor laceration to my back neck and kidney area from Johns' leadouts. My back hurt for a couple of weeks. If John had been a few inches closer to the center of the circle, I would have had an appendage of an Aero Tiger .36 sticking into my back. I was very lucky that I was not seriously injured or worse in this accident. From now on, I will never, and absolutely, have never, turned my back on any aircraft flying when I have been closer than 20 feet from the circle. Maybe this will help prevent a similar calamity from occurring to someone else.
Oh, John's only Nats plane was totally destroyed during in this incident that happened on the Memorial Day weekend. Only some quick building work allowed him to participate in the 2000 Nats.
Jim Pollock
Darwin had a lot to say about this subject!
Brett
Hi guys,
No doubt this stuff can be dangerous.
Here's a thing or two about the electrical dangers.
Getting electricity transferred because you're moving conductors in the magnetic field is inductive coupling. There are no sparks or lightning bolts involved. The windings of wires inside your car's ignition coil never actually touch, and electricity can pass between the two (by design, the size of the coils, diameter of the wire, frequency of the electricity, etc) with virtually no resistance. Similiarly, capacitors are simply metal plates (or some other conductive material) spaced just so, but never touching, and the same thing occurs, this is capacitive coupling. Clearly, electrocution of this sort is quite rare because a lot of planets have to line up to get you.
A point of technical order, power doesn't "jump". In electricity power is the product of the voltage (the size of the water hose) and current (how much water is running through the water hose) (in other words, multiply the two). In alternating current it's usually referred to in "volt amps" or VA's. The term most people recognize is watts. You can have a 100 watt light bulb that operates on 1 volt and uses 100 amps (which would require a wire about 1" in diameter), or one that operates on 100 volts, but then only requires 1 amp (which would require a wire about 1/64" in diameter, see why the power companies lines are so high voltage?). They both consume 100 watts of power. Only half of what power is, is responsible for creating the ability to jump, and that is the voltage, or EMF, the "E" in E=IR. Just about anything can conduct electricity if there is enough force pushing it along. In other words, the higher the voltage, the more things exist that can conduct it. At one point, even dry air can conduct electricy, to the tune of about 1 inch per 20,000 volts. Clearly, air is not a good conductor, but when we're talking high voltage power lines, or lightning bolts, it IS a conductor.
Sorry if this is more technical than you can stand, another hobby of mine is amateur radio, another good way to electrocute yourself. The main point is that there are two entirely different ways to get yourself with respect to c/l and powerlines without ever touching them. Having some understanding of them helps you to make more informed decisions.
Oh, one more thing about the recommended 300', no high tension line can arc that far, no magnetic field is strong enough at that distance to hurt you if you fly through it, so why so far? I figure if you're on 70' lines (sort of worst case), if one wire breaks at the handle you could feasibly extend your little wire conductor to 140' from you with a direct connection to your hand if you're using a metal bellcrank and EZ Just. Operating at a 100% safety factor puts you right at 280', pretty close to 300.
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