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Saturday, March 1, 2014

Blind Trust

Safety Watch: March 2014

By Terry Terrell 

During the period when English sailors began to rule the seas from wooden ships, navigation was not considered a particularly desirable duty, since it often resulted in the hanging of the aspiring pilot from the yardarm, with the outgoing candidate left to dangle for days as a reminder to the next volunteer that being inaccurate would not be warmly received. Latitude was a fairly well understood concept, since reckoning one’s north/south position was a relatively straightforward proposition, based on averaging the elevation of the sun and other heavenly bodies as they traversed the sky from east to west. But, since the accurate measurement of time had not yet been mastered, and in view of the inconvenient fact that one’s left and right orientation on the surface of the earth, with reference to those same heavenly bodies, changes continuously, getting a handle on exactly where one was with reference to east and west was persistent in proving elusive, and those who failed on behalf of undertaking the necessary chore of accurately finishing each leg of a voyage by not missing an important destination, such as a critical life-sustaining island, as an offhand example, were not rewarded kindly.

Eventually, though, acceptably accurate time measurement was achieved in some parts of Europe, and zeroing in on the left/right coordinate was thereby accomplished, so identifying a precise location of a point position on the surface of the globe – literally in due course – became possible. Nowadays we enjoy the use of our own artificially installed heavenly bodies, from which we are normally able to electronically measure extremely accurate proximities at any given instant, and so the navigation problem would seem to be conclusively solved. Alas, however, perfect navigation can still sometimes prove elusive.

When rotary wing aircraft began to become active participants in civilian aviation not many years after World War II, dead reckoning and pilotage, having proven fundamentally reliable to seafarers over the centuries, were the logical order of the day. These time-tested but comparatively loose navigational strategies were adequate for broad general purposes, but there was widespread longing for precision in navigational accuracy that was simply not possible with the map, compass and clock. VOR systems, developed primarily for airplane use at the time, were available to helicopter operators, but “omni-ranging,” didn’t provide the global coverage, or the accuracy, that helicopter operations really required. LORAN systems were eventually developed, able to define aircraft positional information described in terms of pure latitude and longitude, but once again coverage was limited to what fixed transmitter positions on the surface of the earth could offer, and errors were common in many geographic regions. Additionally, the complexities of operating far-flung ground transmitter sites could never be considered completely secure against threats posed by political instability, or war. Ultimately, though, U.S. military developmental initiatives led the way in developing the satellite-based global positioning system, originally aimed at enabling weapons delivery accuracy, but nowadays taken for granted by vast numbers of more casual users, both inside and outside the military, by placing an array of artificial satellite stations in relatively high earth orbit, and programing receivers to interpret extremely accurate physical distance from each satellite, based on transmitted pulse synchronization and the constancy of the speed of light, and radio signaling (by calculating “range shells,” or three-dimensional equivalents of traditionally familiar “range arcs,” from known instantaneous positions of satellites). The modern era, then, would seem to have rendered the fundamental challenges of the navigation problem finally conquered, but such, unfortunately, is still not entirely the case.

We’ve all seen pilots who seem helpless until waypoints are fully entered into navigation computers, and are then comfortable unthinkingly following all manner of flight instrument commands, demonstrating a blind faith in electronic boxes completely misplaced when the risk of a digital entry mistake, among many other possible errors, is considered. While the basic tenet that trusting instruments rather than instincts in aviation is generally recommended, it must also be appreciated that navigation is actually accomplished in the human mind, and that all navigational tools, to include even the most sophisticated, are blind, and must be used primarily to confirm and fine tune perspectives already approximated as part of the situational awareness of the pilot.

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