- Education and Science
How The 1956 Grand Canyon Mid-air Collision Changed Aviation History
There are two main types of aviation: military and civil.
Military Aviation includes the use of aircraft for warfare purposes or under the authority of military bodies.
Civil Aviation is virtually the use of aircraft for any purpose that is not military. This includes scheduled air transport and general aviation.
- Scheduled air transport - Commercial flights domestic or abroad, used to transport passengers or cargo, at regular consistent times.
- General aviation - Non-scheduled flights that can be both private or commercial. Includes small civilian aircraft, aircraft that are not planes (balloons, hang gliders, etc.), and law enforcement aircraft that do not fly regularly.
The World Before Regulation
The early days of air travel were highly unregulated. Public opinion about commercial air was mostly negative, particularly in concern over safety. Air Traffic Control (ATC) was virtually non-existent for much of the early 20th century. As a result, there were many tragic crashes that tarnished the reputation of aviation as a public transportation option.
During these early years Europe was seen as one of the safer areas to fly. The first air traffic control station that catered to civilian flights opened in 1921 at Croydon Airport in London, more than a decade prior to the United States. (Military operations had seen control operations from as early as the 1910s, but until this point civil aviation was seen as too unpopular to require air traffic standards.)
In 1926, U.S. President Calvin Coolidge signed the Air Commerce Act which, among other responsibilities, allowed for the new Aeronautic branch of the Department of Commerce to establish safety regulations. It was hoped these measures would strengthen the public perception of civil aviation.
The Air Commerce Act allowed the Department of Commerce to implement new regulations that were virtually unheard of at the time. Civilian pilots were required to obtain a license, and all aircraft had to pass an "airworthiness" check to assure their aircraft was fit to fly. One of the first attempts at traffic control was also implemented with the establishment of "airways", though these were still vague. As civil aviation increased in popularity, the skies became more crowded, leading to higher danger of mid-air collisions.
The first U.S. ATC tower opened in Chicago in 1930, regulating the ground operations and airspace around the airport. However, open skies were still a hazard, prompting the Bureau of Air Commerce (the Aeronautics Branch successor) to establish the first three ATC centers to monitor airways. Pilots were expected to check in with these stations all along their routes, while controllers monitored the position of the craft through the use of maps, blackboards, and occasionally primitive radar. These methods continued for many years, until one crash forever changed the way the world treated aviation.
Airspace - The entire span of air within a block of altitudes around a specific area. Airspace can be regulated across large distances, including entire countries or bodies of water. It can also be more strictly regulated over certain areas such as military bases.
Airway - A specific corridor between two destinations at a particular altitude. Pilots generally have to stay within a certain height and width of a corridor. Some aircraft are only allowed to fly in a particular airway, such as jets.
On June 30, 1956 two commercial passenger airplanes collided over the Grand Canyon, resulting in the deaths of all 128 passengers and crew. It was the first air accident to result in over 100 fatalities in the U.S., making it the deadliest accident at the time. The resulting investigation revealed the ineffectual methods of air traffic control across the world and helped lead to the creation of the Federal Aviation Agency (later known as the Federal Aviation Administration).
At the time of the crash, communication with ATC was a complicated process. Individual airlines would set up their own waypoint stations along certain airways to communicate via radio with pilots in the air. The dispatchers at these stations could then relay messages from the pilots to the airport ATC that controlled that airspace. For example, if a pilot from a TWA flight wanted to request a change in altitude, he would contact the closest TWA dispatcher, who would inform the airport ATC of the request and then relay the response back to the pilot. Dispatchers would also track aircraft by verbally confirming with the pilot details such as altitude and heading and writing it down. (These stations typically did not have any form of radar system.)
The danger lay in the fact that ATC often did not have a direct reference for where an airplane was at any given time. Pilots were required to intercept waypoints along their route, but it was still common practice to go "off airways" between waypoints. The reasons a pilot may deviate from an established route included avoidance of undesirable weather and sightseeing for passengers. As long as they stayed within the right altitude they were free to do what they liked; much of the open airspace over the U.S. was unregulated.
The fault in this system was revealed when two planes flying "off airways" collided over the Grand Canyon in 1956. United Airlines Flight 718 (a Douglas DC-7 Mainliner) flying from Los Angeles to Chicago had been authorized to a flight level of 21,000 feet, which was maintained for the duration of the flight until the crash. TWA Flight 2 (a Lockheed L-1049 Super Constellation) flying from Los Angeles to Kansas City had been authorized to 19,000 feet.
When Flight 2 encountered a row of thunderheads, Captain Jack Gandy requested a level of 21,000 in order to avoid the bad weather. ATC initially denied this request, knowing that they lacked the ability to keep the TWA and United flights separated at the same altitude. Captain Gandy then requested a "1,000 on top" clearance, meaning he wanted to fly 1,000 feet above the clouds. This permission was granted, with instructions that the TWA crew observe Visual Flight Rules for the duration of the action. Typically referred to as "see and be seen" rules (later "see and avoid"), VFR placed the responsibility for maintaining aircraft separation on the crew of the aircraft.
Climbing above the clouds placed the TWA flight at 21,000 feet, setting the stage for the tragedy to unfold. Travelling at separate headings towards their respective destinations, the two airplanes collided at 10:30 AM over the Grand Canyon. When both flights failed to report in at the next way point (known as the "Painted Desert Line"), both TWA and United dispatchers reported the aircraft as missing to ATC. Soon after, reports of wreckage in the canyon reached authorities, and the Civil Aeronautics Board launched an investigation.
Location where the craft impacted the terrain after colliding. The area was extremely hard to get to, making investigation more difficult.
Despite the lack of modern tools such as cockpit voice and flight data recorders, CAB investigators were able to determine that the two flights were unable to see each other until just seconds before collision. This was revealed as the angle of damage to the planes, as well as the location of ground impacts, indicated that the United flight attempted a downward evasive maneuver to avoid the TWA flight.
Why the two flights were unable to see each other was not fully known. Speculative answers given included hindrance by bad weather and crew preoccupation with other duties. Whatever the true answer was, the CAB investigation revealed huge inadequacies in the way civil airspace was handled. Findings of particular note included the ATC's failure to warn either flight of the potential for collision because they were not legally required to do so, and the lack of ATC's ability to monitor the location of flights because they had insufficient equipment.
This accident prompted public outcry over the inadequacy of U.S. ATC operations, which had changed very little from the 1930s. Congressional hearings led to a $250 million (over $2 trillion in 2014) overhaul of ATC systems, introducing modern radar systems and increasing the amount of ATC employees at stations across the country.
A couple of years later, after another collision involving a civil aircraft and a military fighter jet killed 49 people in 1958, congress finally established the Federal Aviation Agency to finally bring full control to the nationwide airspace. Both civil and military aviation was brought under the authority of the FAA, which implemented stricter airway corridor controls. The results were enormous, drastically lowering instances of mid-air collisions in U.S. airspace.
In 2014, the site of the crash was made a National Historic Landmark. It is the first time a U.S. landmark has been designated for an event that occurred in the air.
So interesting it's addictive, this documentary series combines eyewitness accounts and incredibly detailed reenactments to show some of the worst air accidents and the lessons learned from them. (There's even an episode on the Grand Canyon disaster.)