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Sherlock Ohms

Earth Station Stopped by Lightning

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William K.
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Platinum
Re: Points of Concern
William K.   8/27/2013 9:13:45 PM
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Cabe, with the paperwork needed to get an emergency airdrop of those parts they could have built a paper roof over the whole installation. That was part of the problem.

Cabe Atwell
User Rank
Blogger
Re: Points of Concern
Cabe Atwell   8/27/2013 2:41:37 PM
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That's an incredible story! Too bad the replacement parts couldn't be airdropped. It would have saved a lot of headaches. 

William K.
User Rank
Platinum
Re: Points of Concern
William K.   8/26/2013 12:46:27 PM
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Tool_Man, I don't feel qualified to comment on the other branches of the service, so I didn't. And on many occasions, after lightning has dissipated the charge in one place, it does not hit there again for a while. Besides that, sometimes you just need to ignore hazards. It seems to have worked in that case.

Tool_maker
User Rank
Platinum
Re: Points of Concern
Tool_maker   8/26/2013 12:18:51 PM
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  I guess I must have misread the whole story. They went out in a driving thunderstorm and climbed a tower that had been struck by lightning. I assumed since the storm was  still in force the lightning was still a possibility. My concern had nothing to do with climbing a tower or harness use or OSHA regulations. I was not aware lightning followed OSHA rules, but I do know that when lightning presents a clear and present danger golfers are chased off the courses, ballgames are postponed and people are sent inside.

  Many trades climb towers or poles or work on roofs, but I do not think many do it while lightning is in the area. That is the sole point I was trying to make and I still question the judgement of someone who fails to see the possibility of serious electrical injury no matter how many times it has been practiced.

  By the way, the marines are not the only branch of the service that trains to do a job. All branches drill and practice routines over and over until they become second nature, so they do not have to stop and think before they react in a crisis situation.

William K.
User Rank
Platinum
Re: Points of Concern
William K.   8/26/2013 11:14:45 AM
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Tool man, there is a HUGE difference between depending on blind luck and depending on your self and the things that you know that you can do because you have practiced them a lot. That includes climbing on assorted structures and a lot of other activities. For a tech who had never done anything besides inside benchwork it woulod indeed have been a crazy attempt, but for foloks who have climbed around on a structure a lot it would be just one more exercise. That is why the analogy to the Marines: they KNOW what they can do, because they have done it.

The whole concept does indeed fly right in the face of the ISO9000 thing, which attempts to make jobs so defined that any fool off the street can do it as well as any other person, so that all workers would be interchangeable. That approach is only maoderately applicable to floor sweeping, though. 

The reality is that understanding, practice, and a bit of real insight are needed to do many of the tasks correctly and safely. Not rearing heights is not enough, one must also know and understand how to use the safety belts.

Tool_maker
User Rank
Platinum
Re: Points of Concern
Tool_maker   8/26/2013 7:09:46 AM
NO RATINGS
  I fail to see how keeping a radio tower up and running can be compared to reaction in a combat situation, but perhaps I under estimated the importance. As far the marine combat I guess that could be warranted as I put my time in an Army infantry unit in Vietnam. There is a world of difference between risking life and limb to aid fellow GI's engaged in enemy contact and challenging lightning to keep a radio tower in operation, but as I said in my original post, I am glad there are people willing to take that chance.

  Perhaps crazy was too strong a term, but in my mind when I see people challanging natures fury and depending on luck to remain unscathed the vision that comes to mind is Russian roulette. That is not setting aside all thoughts of self preservation, but trusting to blind luck with the life of the participant as the bet. Call it what you will, but do not compare it military valor. 

78RPM
User Rank
Gold
A Good Case for Drones
78RPM   8/25/2013 3:09:55 PM
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Wouldn't it have been great to have a hexacopter with a light and a camera to inspect the damage? In my state and others, drone use has been limited by legislatures and it is illegal in some states to use them for photography. While I understand their concerns for privacy invasion, legislators are putting the brakes on too hard and this can limit useful innovation. I see that some businesses and states are ready to make preemptive bans on Google Glass.

akili
User Rank
Iron
Still there but no lions!
akili   8/23/2013 10:45:11 AM
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The station is still there (Google Earth 1° 1'2.66"S 36°29'50.43"E) but forty years on it's now surrounded by shambas and huts so the lions and leopards and antelopes are long gone from the area. If you look at the photos on Google Earth, our dish is the nearer one.  The second dish was built some years later by a Japanese company.

Regarding spares, we were supposed to have spare radome diaphragms, they just hadn't yet arrived and nobody thought we would need a new one within the first three months of operation.  I don't envy you having the whole waveguide system without strategic partitions - we were lucky the way the water became trapped quite quickly.  If it had gone all the way it would have taken a week to get it clean and dry.

On the safety aspects, we think that the lightning struck the hand-rails around the small platform at the apex of the tripod.  The access was provided for the aircraft warning beacon that was the only bit of electrical equipment inside the dish.  Our dish-walkers were some thirty feet below this point so we hoped that if the lightning did strike again they wouldn't be fried.  But as remarked elsewhere, sometimes you just have to get on with it and take calculated risks to get the job done.

We did take heart from the fact that the radome was the only casualty, so the basic lightning protection was fine.  We had big flexible earth straps across the elevation bearings to prevent arcs inside the roller bearings, plus three huge spring-loaded carbon brushes that pressed from the rotating king-post to the azimuth bull-gear and top bearing ring.  All 300 tons of our antenna floated on Teflon bearing pads and without the earthing brushes the only electrical path from the king-post to ground would be along the thousands of wires that went through the azimuth cable-wrap machine.  A lightning strike through there would have wrecked everything and put us off-air for months.

The extra loss due to the plastic sheet was just a few tenths of a dB, barely significant in the overall scheme of things.  Hence the lack of urgency to replace it.  The transmitter power was typically just a few hundred watts so even if a few percent of that was dissipated in the plastic sheet it wasn't enough to cause a problem.  The Mylar was OK up to the full 2.5kW if it had been needed but these large stations were so over-engineered and over-specified they never even approached the limits.

Finally, our deputy station manager had some inspired moments but he also had some notable and embarassing disasters.  We ALL love those euphoric moments when we suddenly see the answer to a problem - but beware of getting too attached to an idea.  It might just be wrong and if you persist when all around are saying "but..." then occasionally you will get egg on your face.  But that's what makes engineering such fun.  Only yesterday I met some of the old gang in London for a nostalgia session and we still regard those days as some of the best of our lives.

William K.
User Rank
Platinum
Re: Points of Concern
William K.   8/22/2013 6:14:42 PM
NO RATINGS
Toolguy, it seems that you are not aware of the "set aside all thoughts of self preservation" way of thinking. You would not make it into the special forces or get very far in the ranks of the United States Marines Force. Besides all of that, just because something has the potential to be dangerous does not mean that it will be fatal. Sometimes it is required to do things that have a potential risk. So please don't go calling those who are not chained down by their fears "crazy", OK? Some of us do find that upon occasion we need to venture into areas where the results of a mistake could be bad. But some of us don't chose to surrender to fear.

Of course, as in this tale, the folks venturing outside had a good grasp of the risks, but they understood exactly how to do what they needed to do. Being prepared and knowing just what to do are two very powerful risk reduction tools. The unprepared and unknowing should stay out of the way, since they are the ones who have the problems.

Tool_maker
User Rank
Platinum
Points of Concern
Tool_maker   8/22/2013 3:27:01 PM
NO RATINGS
  I have several comments on this article. First: "Brave volunteers" is a misnomer. People willing to venture into a virtual Lightning Catcher, at the hieght of a storm are not brave, they are crazy. Thank goodness such people exist in such cases and thank goodness they did not get fried. Second: the improvisational charactor of repair speaks volumes about the ability of the crew. I hope they were properly recognized and rewarded. Too often today workers are willing to sit on their hands while waiting for a solution to fall from the sky.

  Lastly, it reminds us of how truly powerless we are in the face of nature's violence. Of course we handle the small and even most of the big stuff, but when weather hits with its full fury, we can do little more than watch in awe.

  A great, well written story. Thanks for sharing.

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