Powerlines
Editor: In November 1995, Brent Stockwell wrote a Balloon Life article called Ballooning, Electricity, and Powerlines. In his article, he correctly stated that most serious injuries in powerline accidents are caused by the basket being severed from the envelope. He also correctly stated that the severing is commonly due to mechanical abrasion of the suspension cables. In the January 1996 issue of Balloon Life, Earl R. Smith wrote a letter to the editor stating that Mr. Stockwell was incorrect about the cause of basket severing and that instead of mechanical abrasion, electrical melting of the suspension lines was always the cause. I must take strong exception to Mr. Smith’s letter because it perpetuates a false understanding of the dangers of powerlines. Mr. Stockwell was correct in stating that mechanical abrasion is the most common cause of suspension line failure in powerline accidents.

I have all too often inspected suspension lines that have been involved in powerline accidents. After reading Mr. Smith’s letter, George Hahn and I inspected a balloon system that was involved in a fatal powerline accident several years ago in Albuquerque. I choose this aircraft for no other reason than it was close by and readily available for inspection. The balloon was a Fire Fly AX-7 with 18 metal suspension cables. The balloon struck a set of 365 kV transmission lines; the basket was severed and both occupants died from trauma associated with the fall. Inspection of the suspension cables showed that 7 of the lines were melted due to electrical current flow. The remaining 11 lines were severed due to mechanical abrasion caused by the smaller diameter suspension lines rubbing transversely to the larger powerline conductors. Any one of those suspension lines should have been able to support the entire basket. My experience has shown this to be the common scenario in powerline accidents. Mr. Stockwell is also correct in stating that Kevlar and similar cables offer no additional protection against this type of cable severing.

The example cited by the Editor of the August, 1993, Colorado balloon accident is an excellent example of the point I’m making. In this accident, six people were killed when the basket they were riding in was severed from the envelope after striking a powerline. In this accident, the powerline was under construction and the lines were not even energized! I disagree with the editor’s statement that the balloon hit the "powerline with such force that it cut through the cables." It doesn’t take much force at all to sever suspension cables, only two loaded cables rubbing against each other. The small individual strands, that make up a single suspension line, are broken one at a time. When one of the small strands break, it places even more load on the remaining strands and they fail quicker and quicker. Total cable failure can happen in an instant.

The important point in this matter is to avoid hitting powerlines. Don’t rely on non conductive components to prevent disaster in the event of an accident. I refer Mr. Smith to the BFA Powerline Safety Manual for additional reading on this subject. This manual also shows photographs of both mechanically and electrically severed suspension lines.

Steven M. Shope
Albuquerque, New Mexico

Mr. Shope edited Powerline Safety Manual published by the Balloon Federation of America. Reviewed in Balloon Life, November 1994.

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