A Different Approach: The crash of TWA flight 514
On the first of December 1974, a Trans World Airlines Boeing 727 on approach to Washington, D.C. suddenly slammed into the side of Mount Weather, Virginia, instantly killing all 92 people on board. As investigators sorted through the massive trail of mangled debris, one question quickly moved to the forefront: why had TWA flight 514 descended to an altitude of just 1,670 feet while still 50 kilometers from its destination? Controversy erupted over the nature of the approach to the airport. Was the crash the fault of the pilots or the air traffic controller? As accusations of blame flew in every direction, investigators realized that the answer was simultaneously both, and neither — in fact, pilots and controllers around the country were not using the same set of standard terminology, leading to a misunderstanding that sent flight 514 into the side of a mountain. The situation had become so dangerous that only six weeks earlier, a United Airlines jet had narrowly escaped the exact same fate. In an effort to halt an escalating worldwide death toll, the National Transportation Safety Board successfully pushed for radical new safety improvements that secured the place of TWA flight 514 as one of the most influential accidents in aviation history.
TWA flight 514 was a regularly scheduled flight from Indianapolis, Indiana, to Washington National Airport in Washington, D.C., with a stop in Columbus, Ohio. In command of the three-engine Boeing 727 were Captain Richard Brock, First Officer Lenard Kresheck, and Flight Engineer Thomas Safranek, all of whom had clean records with no problems noted in training. Joining them for the second segment from Columbus to Washington were four flight attendants and 85 passengers, totaling 92 people on board. Flight 514 departed Columbus at 10:24 a.m., 11 minutes late.
Twelve minutes after takeoff, the crew received some unwelcome news: due to bad weather, Washington National Airport was closed to all traffic. Weather observers had recorded crosswinds gusting up to 49 knots (91km/h), far above the safe landing limit. Flight 514 was ordered to divert to Dulles, Washington’s other major airport, located 36 kilometers west of D.C. in a suburban area of northern Virginia. For the passengers, news of the diversion was an inconvenience, but far from the end of the world.
At 10:48, already more than half way through the short flight, the crew made contact with the regional air traffic control center in Washington, D.C. As flight 514 descended to an intermediate altitude of 23,000 feet, Captain Brock turned over control to First Officer Kresheck, and the crew discussed how they would approach the airport. The extended centerline of runway 12, the planned landing runway, proceeded northwest on a heading of 300 degrees; this imaginary line was referred to as the “300˚ radial of Armel,” Armel being the radio beacon located at Dulles Airport. Their plan was to fly to the Front Royal radio beacon, which was located on the south side of the 300˚ radial of Armel, then fly east to intercept the radial and follow it to the runway, as shown in the above diagram. The published approach procedure for runway 12 also followed the 300˚ radial, but the official approach only began at the Round Hill beacon, located some 18 nautical miles (33km) northwest of the airport — well after the point where the pilots of flight 514 would intercept the radial. At 10:51, the controller cleared the crew to intercept the 300˚ radial at a point 25nm (46km) northwest of Armel and instructed them to maintain an altitude of 8,000 feet.
The approach via Front Royal due east to the 300˚ radial was not an officially published procedure. The pilots’ approach charts for runway 12 showed the approach beginning at the Round Hill beacon, which was therefore referred to as the “initial approach fix” — the point at which a flight officially enters the named approach pattern. The chart also displayed a point 6nm (11km) from the airport, with no further points before reaching the runway. This made the 6nm point the “final approach fix,” that is, the last point on the named approach pattern. The chart also included a profile or side view of the approach beginning from the final approach fix and continuing to the runway. All of this information would come into play as flight 514 began its descent toward the airport.
At 11:01, the controller cleared flight 514 to descend to 7,000 feet and handed it off to Dulles approach control. At 11:04, while the flight was still 44nm (81.5km) from the airport, the Dulles controller cleared flight 514 to approach runway 12. At this point, a critical misunderstanding occurred. When the controller told Captain Brock that he was “cleared for approach,” Brock believed this meant that the controller was providing him with “radar guidance;” that is, that the controller was monitoring his position and altitude and would point out any deviation from the proper approach path. He also believed that when under radar guidance, if the controller did not give him a minimum altitude alongside the approach clearance, then they were supposed to descend to the altitude specified for the final approach fix. His chart showed that the minimum descent altitude at the 6nm final approach fix was 1,800 feet; therefore, he told the other pilots that they should descend from 7,000 feet to 1,800 feet right away. “Eighteen hundred is the bottom,” he said, and First Officer Kresheck replied, “Start down!”
But this wasn’t what the controller intended when he cleared flight 514 to approach runway 12. The controller believed that he was not providing radar guidance and that the crew was responsible for its own navigation, absolving him of any obligation to provide them with a minimum altitude. The pilots could figure that out on their own by reading their charts. This misunderstanding came about because controllers were given full discretion to decide whether they could provide a radar “service” for an inbound aircraft, while pilots did not necessarily know whether a controller was providing radar service for them or not, and usually assumed that if they were in an area covered by radar, that radar service would be provided. When the controller cleared flight 514 for the approach without specifying a minimum altitude, Brock believed that this meant there were no obstructions between his position and the airport — otherwise the controller surely would have told him not to descend below some particular altitude. Tragically, he was wrong.
At 11:07, as the plane descended toward 1,800 feet amid moderate turbulence, Captain Brock studied the approach chart a little closer. To his surprise, he discovered that it showed a minimum descent altitude of 3,400 feet between Front Royal and Round Hill, the initial approach fix. This contradicted what he had been led to believe by the controller. “You know,” he said, “this dumb sheet says it’s thirty-four hundred to Round Hill — is our minimum altitude.”
“Where do you see that?” Flight Engineer Safranek asked.
After Brock showed the other pilots the indication on the chart, First Officer Kresheck said, “When he clears you, that means you can go to your — ”
“Initial approach,” someone interrupted.
“Initial approach altitude,” Brock clarified.
“We’re out of twenty eight [hundred] for eighteen [hundred],” said Safranek.
“Right,” someone replied. “One [thousand] to go.”
Remarkably, the pilots had decided that the relatively ambiguous clearance from air traffic control overrode the minimum descent altitude specified on their approach chart! This came in spite of the fact that the approach chart clearly showed mountains rising to 1,930 and 1,764 feet on either side of their course — a fact which might have eluded them because they were not on any of the radials shown on the chart. In all likelihood, they wouldn’t have been able to determine their exact position until after they had turned onto the 300˚ radial of Armel. There was one other factor that contributed to their confusion, however: the profile view of the approach began at the final approach fix instead of the initial approach fix, obscuring the fact that a descent from 3,400 feet to 1,800 feet was only supposed to happen after passing Round Hill.
Rain and snow enveloped the plane as it descended through the clouds, finally reaching 1,800 feet around the time it arrived at the 300˚ radial. “Dark in here,” Kresheck said. “Bumpy too.”
Brock, who had been expecting to break through the cloud base, commented, “I had ground contact a minute ago.”
“Yeah, I did too,” said Kresheck. Turbulence battered the plane, causing its altitude to fluctuate to more than 100 feet below their target. Noticing that they were slipping below 1,800 feet, Kresheck said, “…power on this bitch!”
“Yeah — you got a high sink rate,” said Brock.
“We’re going uphill,” someone said.
“We’re right there, we’re on course,” said Safranek.
“You ought to see the ground outside in just a minute,” said Brock.
Another jolt of turbulence struck the plane. “Hang in there, boy,” said Safranek, “we’re getting seasick!”
“Boy, it was — it wanted to go right down through there, man,” said Kresheck. “Must have had a hell of a downdraft!” The flight passed over the Shenandoah River, holding steady just below 1,800 feet, its pilots unaware that they were on a collision course with a fog-shrouded mountain.
At 11:09 and 14 seconds, the radio altimeter emitted a chime, informing the crew that they were 500 feet above the ground. This was much closer than any of the pilots thought they should be. “Boy!” Brock shouted, “Get some power on!” Kresheck pushed the throttles forward to climb out of whatever they had gotten themselves into. A few seconds after the first warning, the radio altimeter issued another chime, now telling the crew that they were only 100 feet above the ground. This time, no one even got a chance to react. Less than two seconds later, TWA flight 514 clipped trees near the summit of Mount Weather at an altitude of 1,670 feet. The 727 cut a wide swathe through the forest before it slammed into the ground, slid across the Blue Ridge Mountain Road, and smashed headlong into a rock outcropping. The impact triggered a massive explosion, sending pieces of the plane cartwheeling over the top of the mountain as a wave of fire tore through the trees behind them. By the time the debris came to a stop, little remained that was recognizable as part of an airplane. None of the 92 passengers and crew had survived.
Local residents reported that visibility was as little as 16 meters in falling snow with 74km/h winds whipping over the mountaintop when they arrived on the desolate scene. Pieces of the plane and its occupants were strewn across an area covering over 8,000 square meters, a massive debris field filled with the eerie light of spot fires and the shattered trunks of countless trees. Emergency services arriving on the scene could do nothing more than close the highway and start working to recover the bodies, carrying the remains of 92 people off the mountain as a gentle white blanket of snow slowly covered the wreckage. When news stations got wind of the crash, the first thing they did was to check whether any prominent politicians had been on board. Although US Senator Birch Bayh (D-Indiana) had been scheduled to board the return flight to Indianapolis, no major public figures died in the crash. Some broadcasters repeatedly stated that “no one of importance was on board” — a deeply painful line for those whose loved ones had perished.
As the National Transportation Safety Board reviewed the contents of the black boxes and interviewed the air traffic controller, evidence of a misunderstanding emerged. The pilots clearly believed they were under radar guidance, while the controller insisted that they were not. The pilots believed the controller’s statements implied they could descend to 1,800 feet; the controller believed that the pilots were responsible for their own terrain avoidance. Because both parties thought the other was in charge, nobody was paying attention to whether flight 514 might be on a collision course with terrain. The controller also stated that the plane’s altitude was obscured on his screen for some time due to an overlapping weather return, and by the time he asked the pilots to clarify, the crash had already occurred.
The NTSB felt that the controller should have provided radar guidance and offered a minimum descent altitude. But at the same time, the absence of this information didn’t excuse the pilots, who should have exercised a little common sense and realized that the minimum descent altitudes shown on their chart exist for a reason. Contributing to the problem was a poorly designed approach chart that didn’t prominently display the minimum altitude at the Round Hill approach fix. Had a minimum of 3,400 feet been clearly displayed on the profile view with an emphasis on its necessity for terrain clearance, the pilots might have reconsidered their decision to descend.
But as it turned out, the problem extended far beyond this particular set of people. Several weeks before the crash, a pilot at United Airlines used an anonymous incident reporting system to reveal that he had descended below the minimum descent altitude on approach to Dulles after receiving approach clearance while still 25nm (46km) from the airport. The flight narrowly missed striking Mount Weather and subsequently made a safe landing. As a result of the incident, United conducted an internal review and found that some pilots were routinely violating minimum descent altitudes when given approach clearance early. It then issued a notice to its pilots advising them to check what minimum altitudes apply to their route before assuming they have permission to descend to the altitude of the final approach fix. However, United Airlines didn’t inform the FAA, so other carriers never learned of the issue.
The problem was in fact far more common than anyone initially realized. Just 30 minutes before the crash of TWA flight 514, an American Airlines Boeing 727 on approach to runway 12 at Dulles was cleared for approach without a specified minimum altitude. The captain then asked the controller to clarify whether they could descend to the altitude of the final approach fix, and the controller stated that they could not. The flight continued without incident. With such confusion apparently occurring several times a day, it was only a matter of time before a pilot failed to ask for clarification, descended too soon, and crashed into a mountain. The identities of the pilots and controllers involved in the eventual accident, and any mistakes they might have made, scarcely mattered.
As more and more people testified at the NTSB’s public hearings, it became clearer how the system had gotten so muddled. While providing radar guidance to aircraft, controllers did sometimes order pilots to fly below the minimum descent altitudes shown on their charts — because controllers used their own set of minimums that differed from those used by pilots. As a result, pilots became accustomed to controllers sending them below official minimums, and began to rely less on their approach charts to ensure terrain avoidance. This occurred despite the fact that controllers were not always tracking inbound flights on radar as pilots generally assumed. In 1970, TWA complained to the Federal Aviation Administration about these discrepancies in understanding between pilots and controllers, but the FAA took no immediate action, arguing that pilots didn’t need to know whether they were under radar guidance or not. Furthermore, the FAA-issued airman’s manual in use when the pilots of flight 514 first learned to fly stated that upon receiving an approach clearance, one should descend to the “approach altitude” as soon as possible. This line was deleted without explanation in 1970, and it was unlikely that any pilots who had been exposed to the old version would have noticed the change.
When it came time to publish the final report, the team of five lead investigators could not agree on whether the pilots or the controller should be found at fault. A majority of three ruled that the pilots were ultimately responsible for their own terrain clearance, although they acknowledged that their failure to do so was a result of misleading and ambiguous cues from the air traffic controller. However, two investigators dissented, writing that the root cause was the controller’s failure to provide the pilots with a minimum descent altitude. The difference between the two sides hinged on whether or not flight 514 was (or should have been) under radar guidance when the approach clearance was issued. But all the investigators agreed on one thing: something was terribly wrong with America’s airways.
Shocked by the scale of the mess it had uncovered, the NTSB in its final report indicted the entire aviation system as fatally deficient. Investigators wrote, “The system should clearly require controllers to give the pilots specific information regarding their positions relative to the approach fix and a minimum altitude to which the flight could descend before arriving at that fix. Pilots should not be faced with the necessity of choosing from among several courses of action to comply with a clearance.” It further stated that there were no common definitions of terms like “final approach course” or “radar arrival,” and that a universal lexicon must be established, along with a single book of procedures for use by both pilots and air traffic controllers so that they will always be on the same page. The FAA agreed, and began assembling such a lexicon to be issued to all pilots and controllers within a year after the accident. The NTSB also recommended that the cartographic style of all approach charts be standardized; that the profile view on approach charts include not only the final approach fix, but also the initial and intermediate approach fixes; that controllers inform pilots immediately if they observe a flight deviating from a safe course or altitude; that an automatic system be created to warn controllers when such deviations occur; and that a nationwide incident reporting system be created, allowing pilots to speak up about incidents without fear of reprisal. The FAA responded with swift and decisive action to implement all of these changes.
But while these changes alone already represented a massive improvement to safety, the NTSB was not done. They wanted not just to tackle procedural issues, but also the broader problem of “controlled flight into terrain” accidents. At the time of the crash of TWA flight 514, the only warning that pilots would receive when flying toward terrain was a pair of altitude alert chimes from the radio altimeter, and even then only if the crew had set it correctly. In the case of flight 514, the first of these warnings came only seven seconds before impact, rendering it effectively useless. Instead, the NTSB asked the FAA to mandate that all airliners carry a dedicated ground proximity warning system that would give pilots an unambiguous order to climb with sufficient advance notice to avoid impact. In the case of flight 514, only five to ten additional seconds to react could have meant the difference between life and death. The NTSB identified a further ten accidents within the past several years in the US alone that could have been prevented by such a system. As a result of this recommendation, the FAA immediately took action, requiring that all US airliners have a ground proximity warning system by the end of 1975.
The scale of the safety improvement that has come as a result of this rule is difficult to comprehend. The number of controlled flight into terrain accidents in the United States immediately underwent a drastic reduction, and the same occurred worldwide as more and more countries also mandated the system. Although it didn’t completely eliminate the problem, the effect has nevertheless been profound. The number of lives saved by the introduction of the ground proximity warning system can probably be measured in the tens of thousands, making it one of the most important safety advances in aviation history.
Despite its enormous safety impact, the crash of TWA flight 514 is largely forgotten today, overshadowed by the many other deadlier and more spectacular disasters that befell the industry in the 1970s. The subtleties of approach procedures were never as captivating to the public as the drama of massive mechanical failures or scandalous design shortcuts. 46 years after the crash on Mount Weather, the forest has regrown over the place where the wreckage of flight 514 came to rest. The only sign of the tragedy that unfolded there is a pair of crosses and a small plaque atop the rock outcropping beside the Blue Ridge Mountain Road, easily mistaken for the makeshift memorials to car crash victims that populate the margins of America’s highways. But while there are no sprawling memorial parks or big budget made-for-TV documentaries to commemorate the crash of TWA flight 514, those who still grieve for the 92 victims can take solace in the fact that because of their unwanted sacrifice, untold masses have been saved from countless future accidents that never came to be.
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