Question: You experience an engine failure at a fairly charitable altitude (say 4500 feet) during a cross-country flight. There aren’t any airports within gliding range, but you immediately see a perfectly straight clearing in the heavily wooded area over which you are flying (which fortunately, appears to be relatively flat) You notice that it continues off into the middle distance, at which point it abruptly changes direction by about 25 degrees and continues again in another long, straight line. Why might you not want to even think about landing there?
A) You’re seeing a highway in the making. Unfortunately, you are also seeing terrain that has yet to be graded and cleared of what is probably some fairly large scale debris. Just because it’s clear of trees doesn’t mean that it is also free of bushes, gullies, or boulders. In fact, most narrow right-of-way clearings in heavily wooded areas are festooned with fairly large and potentially fatal obstacles.
B) It is most likely an unused or abandoned ski slope. (And as you might infer, it sure as heck won’t be level.)
C) You aren’t looking at a highway, or a highway-to-be. You’re looking at a power line. Or rather, you will be, once you descend further.
Unlike gently curving superhighways, ‘highways’ for high-power transmission lines progress in a series of usually perfectly straight lines.
D) It could be the right of way for a natural gas transmission line.
Most portions are underground, but you wouldn’t want to find out the hard way where the above ground sections are.
Answer:
By the time you got below 1000 feet above ground level, you would probably be sorry you picked it, because that’s when you would likely begin to see the towers, or their short dark shadows. Highways are built with smooth graceful curves for long-range visibility and minimum skidding when the road surface is wet, but power transmission lines are usually built perfectly straight. And there’s a reason. Where towers run straight, the pull of the wires on opposite sides of each tower exert equal and opposite forces, and thus don’t act to ‘tip’ any one tower over. Where the direction must be inevitably changed however, there is then a resultant force toward the inside of the bend that has to be compensated by something that provides a pulling force in the opposite direction-towards the outside of the bend. These forces are usually provided by strong cables attached to solidly anchored bases near the tower (or towers) in question. Since construction for such corner towers is significantly more costly, and a gradual curve would require several of them, power lines, unlike highways, usually have single sharp bends. The answer is choice C.
