On the morning of June 30, 1956, two airliners took off within minutes of each other from Los Angeles. United Flight 718 for Kansas City, a DC-7, climbed eastward above the great Mojave Desert to its requested cruise altitude of 21,000 feet. The other was a Lockheed Super Constellation, TWA Flight 2, also climbing toward the east. Destination: Chicago Midway. Both were on instrument flight plans under the control of the CAA (Civil Aeronautics Authority). TWA 2 was assigned 19,000 feet.
Over Arizona, both airliners obtained clearances to divert "off airways."
It was the custom of that time on commercial flights to give passengers a view of the Grand Canyon. There were towering clouds over much of Arizona, and the pilot of TWA 2 radioed a request for a higher altitude in order to fly above them. The request was denied by the CAA enroute controller in Salt Lake City.
According to the "hemispheric rule," eastbound instrument flights are assigned odd altitudes. The next such for TWA 2 would have been 21,000 feet, which was already occupied by United 718. The pilot of the Constellation elected to go "visual" and cancelled his instrument flight plan. Under the visual flight rules in effect at that time, a plane could legally fly at any altitude and in any direction so long as it remained clear of clouds. "See and avoid" then became the operative principle for separation. TWA 2 climbed to 21,000 feet.
Unknown to each other, the two airliners -- one a silver-winged cylinder with tall tail marked in red, white, and blue, the other having an inflected fuselage, gleaming white, and triple tail -- each with four perfect engines delivering rated power, each gently banking above the clouds, their passengers gaping at the natural wonders below -- two crafted marvels of performance and reliability took up momentary courses that converged in the sky.
All persons aboard both planes, a total of 128, died. Front pages around the world pictured only sooted rocks and aluminum shards glinting on the desert cliffs. Inaccessible silence. The worst such tragedy of its time. But not the last.
Air Traffic Control (ATC) began after World War II in the control towers at a handful of the busiest airports. The purpose of ATC, stated simply, is to keep airplanes from running into each other. In the beginning, the job was uncomplicated. Planes were few, communications light. Soon enough, the workload began to build.
By the early fifties, a couple of dozen "enroute centers" had been established in small office buildings scattered about the country. Each center employed a few civil servants in white shirts and neckties who donned headsets and sat at desks, speaking intently into bulky microphones. On tables beside them were slanting trays which held hand-written "flight progress strips." Each tray represented an airway segment; each flight strip represented an aircraft aloft. Information about flights came in by teletype. As planes came under control of the center, flight strips were filled out and loaded individually into 6-inch aluminum extrusions. These fit between bars on the trays, each bar corresponding to one thousand feet in altitude. A push-button beside each bar operated a mechanical release that enabled a controller to drop a strip down to the next bar after first clearing the flight to descend.
That was the extent of technology in the early fifties. There were no radars. Imagine Air Traffic Control with no radars! At the time of the midair collision over the Grand Canyon there was only one surveillance radar in operation -- in Washington D.C.
The nation was shocked. Government had to act. The CAA became the FAA (Federal Aviation Administration), with expanded responsibilities and, some say, contradictory missions: regulation and promotion of civilian air transportation.
Appropriations for technology increased a hundredfold, and "modernization of the airways" began. Commerce in the sky flourished at an even faster pace, and midair collisions would become more frequent, shocking the public's sensibilities. "Crowded skies" topped the list of passenger fears.
The Grand Canyon crash horrified us more than others. The haunting thought would return to our minds: thundering airliners weaving among the clouds above wide open spaces and then...
We shook our heads. Statistical anomaly.
By the late fifties, the first turbojets came into service. Sleek, shrieking airliners whisked an affluent segment of the population into the sky to stare down on cities and farmlands and highways. Passengers increased in numbers, stifling their fears in order to join a hurried elite. Cocktails in hand, they pointed at their watches and chortled at the crawling pace of railroad trains and ant-like cars six miles below.
Day and night in all kinds of weather, airplanes filled the airspace above our cities. Alongside the 707's flew Constellations and Martinliners, criss-crossing in the sky. Electras and Convairs approached aerodromes of the time, mixed with DC-6's and -7's -- not to mention the fabulous fleet of venerable DC-3's. Near metropolitan airports, planes rushed through the sky, passing above and below one another at all different speeds -- now overtaking one another, now jinking away from one another, now converging to compete with one another for the runway.
Still, Air Traffic Control had not yet claimed its primacy. In 1959, radar equipment on the ground was both primitive and decrepit. Technicians struggled to keep operational the SPA-8 PPIs (plan position indicators), wartime relics. Radios were still the "low-freq" variety, each with a "coffee-grinder" for tuning; frequencies were crowded and croaky. Only later would cockpits and towers get the earliest VHF (very high frequency) transceivers, with detented frequency selectors.
Pilots barked imperious requests ("Uh, Approach, why the delay?") Controllers, chain-smokers all, stared for hours into their radarscopes. They still had to keep track of planes by flight strips, mounted in those extruded aluminum holders. The slotted racks now stood beside the radarscopes, but the strips were still passed by hand from rack to rack, controller to controller as the corresponding flights proceed from fix to fix, sector to sector. Controllers found themselves forced to shuffle vital data inside their heads. They tracked as many as a dozen blurry radar blips jerking across the screen, all the while answering radio calls and giving clearances and handing off flights to other controllers. Thankless, mind-numbing work, with no room for error.
Responsibility for each flight was ambiguously shared between the pilot enthroned in his cockpit, and the controller sweating in front of his glowing green bottle. The pilot, though unable to perceive the overall traffic situation, was nevertheless boss of the flight. The air traffic controller viewed the evolving scene on the radar screen and could spot potential conflicts; however, in the late fifties, controllers still found themselves constrained to perform an advisory service. They negotiated with pilots. "Turn right, heading 270," really meant: "Please head west now if you don't mind."
Since nothing on the screen revealed the identity of each blip, controllers often had to assign extraneous maneuvers and then try to figure out who was who by observing the consequent radar track. Forget the altitude of a given plane and you had to ask the pilot. "American three-twelve, say altitude."
"Level at eight thousand, same as I just told you."
Two airliners collided over the Grand Canyon. A handful of years later, the air traffic controllers had their radars. But the rush of events in the sky continued to outstrip technological developments on the ground, much as the jets streaked along above the trains. The system, such as it was, relied increasingly on human perfection.
Thus, unseen to the passengers aloft, the controllers squinted and listened and shuffled and talked -- minute by minute spanning the gap between relentless demand and critical limitations imposed by outmoded hardware. Yet, sometimes months go by and there are no midair collisions.
We shake our heads. Statistical anomaly.
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