Avionics News February 2012 - 23

World War II pilots suffered numerous midairs, many stemming from tight bomber formations during daylight raids. Planners designed the tight packs of bombers to help them combine their defensive might and leave no space for enemy fighters to penetrate those formations. Of course, with no room for a small fighter plane, the large, lessmaneuverable bombers also flew with little to no margin for error. Errors of such nature were expected in the unpredictable, often frantic flying of aerial combat. But, the issue gained critical status for civil aviation in the post-war years, when America’s

ensuing years until a collision between a singleengine Cessna 172 and a Pacific Southwest Airlines Boeing 727 over San Diego on Sept. 25, 1978. After that collision, new rules and requirements were developed, elevating the four-digit encoding transponder to an altitude-reporting beacon and required equipment on aircraft seeking access to the nation’s busiest airspace. Today, those technological and automated systems have built upon Mode C transponders to create on-board traffic alert and collision avoidance systems, predominantly in commer-

Sadly, near midair and actual midair collisions remain one of aviation’s most vexing issues, one that seemingly resists solutions both simple and human – the Mark II eyeball see-and-avoid system – and technological and automated.
commercial and private aviation segments began to grow significantly. Barely a decade beyond the war’s end, the specter of the midair collision became its most startling and most graphic. On a crisp, clear, cloudless Saturday morning, June 30, 1956, United Airlines Flight 718 collided with Trans World Airlines Flight 2. The United Douglas DC-7 and the TWA Lockheed Super Constellation closed on each other at an angle of about 25 degrees, each planning to select an airway a few miles ahead. The collision killed all 58 aboard the DC-7 and the 70 on the Connie. With air traffic control in its infancy and aircraft control shared between controllers and dispatchers, steps were taken to mitigate the prospects of a repeat. But, even those steps fell short of eliminating the risks, as discovered repeatedly during the cial and business-turbine aircraft. Effective collision avoidance systems have been slower to penetrate the bulk of general aviation. This is particularly true at the lower end of the spectrum, where the majority of pilots fly the majority of the aircraft, primarily for personal and business needs. While good, effective systems have been around for more than two decades, the relative costs continue to hold them out of reach for many aircraft owners. In reality, even today’s most cost-effective, inthe-aircraft gear can command an investment half the value of many older general aviation aircraft; hence, the potential and appeal of lower-cost, portable systems, particularly ones capable of interfacing with a display.
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Avionics News February 2012

Table of Contents for the Digital Edition of Avionics News February 2012