A Watery Surprise: The crash of National Airlines flight 193
On the 8th of May 1978, a National Airlines Boeing 727 was on approach to Pensacola, Florida when it suddenly touched down in Escambia Bay amid heavy fog. The unplanned water landing caught everyone by surprise, including the crew, who were just as mystified as the passengers by the unexpected landing short of the runway. The plane came to a stop intact in less than four meters of water, but it rapidly began to sink, and many people didn’t know where to find the water survival equipment. Events took a dark turn when numerous passengers attempted to use seat cushions as flotation devices, a common piece of airplane wisdom which turned out to be less wise than was thought; despite the shallow water and plentiful life vests, three people drowned due to this mistaken belief. The National Transportation Safety Board found that an error by the air traffic controller had put the plane in a position where a safe approach was impossible, but the crew attempted to land anyway, resulting in an escalating chain of mistakes that led to the accident. But while crew performance has vastly improved, the debate about seat cushions and life vests continues to rage more than 40 years after the crash.
National Airlines flight 193 was a city hopper route serving the US Gulf Coast. Originating in Miami, Florida, the flight was scheduled to stop in Melbourne, Florida; Tampa, Florida; and New Orleans, Louisiana, before turning around and making two more stops in Mobile, Alabama and Pensacola, Florida. Like many airlines in the 1970s, National Airlines operated these flights using relatively large planes that it couldn’t hope to fill to capacity — in this case, the Boeing 727, which could seat over 130 passengers. On the night of the 8th of May 1978, just 52 of those seats were filled as flight 193 departed Mobile for its last leg of the night. Also on board were three flight attendants and three pilots: Captain George Kunz, First Officer Leonard Sanderson Jr., and Flight Engineer James Stockwell. When flight 193 took to the skies at 9:02 p.m., their working day was nearly done — Mobile and Pensacola were so close together that they could expect to be on the ground again in barely 20 minutes.
Of Pensacola Regional Airport’s two runways, only one had an instrument landing system that could guide flight 193 down through the overcast night, but this runway had been under construction for months and the ILS was out of service. Although this information was included in the pilots’ briefing materials, they appeared not to have read them, because the news caught the crew by surprise when the Pensacola controller informed them of the closure during their descent to the airport. Instead of a standard ILS approach, the controller told the crew that they would be landing using a rare Airport Surveillance Radar (ASR) approach. In an ASR approach, the pilots don’t tune their instruments to track any navigational aids; instead, the air traffic controller observes the flight on radar and tells the crew where to turn and where to descend until the plane is lined up and the runway is in sight. This type of approach relies on the controller providing advance notice of the planned descent and level off points so that the pilots know when to configure the airplane for the various approach phases.
The ASR approach procedure for runway 26 at Pensacola specified that the controller must place an incoming aircraft on the final approach course — that is, aligned with the runway — no less than two nautical miles (3.7km) outside the final approach fix. The final approach fix, or FAF, is the last fixed point on the approach pattern; it is the point where an incoming plane is allowed to descend to the minimum descent altitude (the lowest altitude permitted without seeing the runway), and it also delineates where the pilots must have their plane configured for landing. In this case, the FAF was located 6nm (11.1km) from the runway, so the controller needed to turn the southbound flight 193 onto the westbound approach course at least 8nm (14.8km) from the threshold.
However, the controller’s initial instruction for flight 193 to turn south had positioned it such that it would intercept the final approach course less than 8nm from the runway. At 9:19, still heading south, flight 193 received clearance to descend to the minimum descent altitude, in this case 480 feet. The controller also noted that they were 5.5nm northeast of the runway. Seventeen seconds later, the controller instructed them to turn to a heading of 250 degrees, which would put them on the final approach course only 4.5nm from the runway threshold, instead of the 8nm required. Captain Kunz began the turn onto the final approach course, but he apparently did not appreciate that he was being vectored to it inside the FAF.
Kunz was in fact expecting the controller to tell him his distance from the FAF, as required by the ASR approach procedure. But the controller mistakenly believed that he didn’t need to provide the distance to the FAF if he had already cleared the plane to descend to the minimum descent altitude (MDA). From the controller’s perspective, the main function of the FAF was to be the point at which a flight can descend to the MDA, but he failed to appreciate that it also plays a critical role in the timing of changes pilots must make to the airplane’s configuration. In fact, standard procedures dictated that the pilots must finish the before landing checklist prior to reaching the FAF. As flight 193 passed abeam the FAF and intercepted the final approach course, the crew had not even begun this checklist because the controller never told them how far away the FAF was.
The consequence of this delay to the landing checklist was that Captain Kunz began his descent toward the MDA in a different configuration than he was used to. Normally by this point, the flaps would be extended to 30 degrees and the landing gear would be down, but instead the gear was still stowed and the flaps were at 25 degrees. He established the plane in a descent of 1,000 feet per minute, but without the fully extended flaps and landing gear causing extra drag, their speed was 10–15 knots too high. It was clear that Kunz was struggling to balance both descent rate and speed in an unusual configuration. To bring their speed down, he reduced engine power to idle; this fixed their speed but caused their descent rate to increase. Now flight 193 was dropping at 1,600 feet per minute, well above the maximum recommended on final approach, and falling faster with every passing moment.
After just a few seconds, the landing gear warning horn began to blare, informing them that they were too close to the ground with the landing gear stowed. Only now did Kunz seem to realize that they were well past the FAF and needed to perform the before landing checklist. “Gear down,” he ordered; a second later, he called out, “Landing final checklist!” Flight Engineer Stockwell pulled out the before landing checklist and began to configure the airplane, while Captain Kunz tried to maintain the optimal pitch angle and First Officer Sanderson scanned the darkness for some sign of the runway. No one noticed that when the gear and flaps were extended in accordance with the checklist, the extra drag in combination with idle power on the engines had caused their descent rate to increase to 2,000 feet per minute.
Right as the crew finished rushing through the checklist, the plane’s ground proximity warning system (GPWS) detected that they were only 500 feet above the ground and descending quickly. Suddenly, the cockpit was filled with the sound of a robotic voice calling out, “WOOP WOOP, PULL UP! WOOP WOOP, PULL UP!” Simultaneously, a light illuminated in front of each pilot informing them that they were descending past the MDA. But Kunz and Sanderson, who were unaware that they had been descending at 2,000 feet per minute, found the warning confusing. Why was it sounding now? Was the warning false?
Did you get your thing?” Kunz asked, barely audible under the blare of the alarm.
“Descent rate’s keeping it up,” said Sanderson. To rein in their descent rate, Kunz began to pull back lightly on the controls. At the same time, Flight Engineer Stockwell mistakenly thought he heard Kunz tell him to silence the alarm. He reached over and flipped a switch to inhibit the GPWS, causing the warning to cease. Coincidentally, this convinced Kunz that his minor adjustment to their descent rate had corrected the problem. No one had noticed that they were only 250 feet above the ground and dropping fast.
Seven seconds after Stockwell silenced the terrain warning, Sanderson finally looked at his altimeter and exclaimed, “Hey, hey, we’re down to fifty feet!” But before Captain Kunz could even react to his first officer’s warning, the 727 suddenly slammed into the surface of Escambia Bay. With an enormous splash, the plane plowed forward through the water for barely a hundred meters before lurching to an abrupt halt. For those in the front of the plane, the crash didn’t feel much worse than a regular hard landing, but in the tail section, the impact forces tore out the bottom of the fuselage, taking the 727’s ventral staircase and the cargo doors with it; passengers seated in this area were thrown hard against the seats in front of them, causing serious injuries. Nevertheless, by the time the plane came to a stop, all 58 passengers and crew were alive. With the plane floating in water that was just four meters deep, it seemed that they had dodged a bullet. Little did they know the worst was yet to come.
Also on Escambia Bay that night was tugboat pilot Glenn McDonald, who was struggling to find his way amid the darkness and fog while pushing an unwieldy barge. He watched in astonishment as the lights of flight 193 descended lower and lower until the plane crashed into the water just a few hundred meters from his boat. He immediately changed course toward the stricken plane, determined to save as many people as possible.
Meanwhile on the 727, the 52 passengers struggled to figure out what to do next. As the flight from Mobile to Pensacola was considered an overland flight, the passenger briefing hadn’t included any instructions on what to do in the event of a water landing, nor did it mention where to find the life vests. As a result, many of the passengers didn’t know where the life vests were located, and some of those who did know struggled to extract them from under their seats. Worse still, 24 people — including all the crewmembers — thought that the seat cushions could be used as flotation devices. While true on some airplanes, this wasn’t the case on a 727 outfitted for overland flight, and it was actually equipped with regular seat cushions. As water began to pour in through the ruptured ventral stairway, passengers fled through the exits and into the bay, only to discover that their supposedly buoyant seat cushions actually weren’t buoyant at all. The cushions couldn’t support a person’s weight and in fact began to disintegrate as soon as they made contact with water, leaving several people flailing helplessly as their cushions fell apart like wet paper. Some managed to swim to safety on the wings, but others sank into the murky water, never to resurface.
Throughout the evacuation, the pilots and flight attendants worked hard to make sure everyone escaped safely. After First Officer Sanderson and a flight attendant both fell through a hole in the galley floor, they began rerouting passengers to different exits. As the plane sank deeper, the pilots repeatedly swam down into the submerged rear of the cabin to make sure everyone had escaped. And after leaving the plane, Captain Kunz found several seriously injured passengers struggling to stay afloat. After realizing that the plane had hit the bottom of the bay and would not sink further, he began to drag injured passengers over to the still-exposed roof of the cockpit, where he hauled them onto this relatively dry land to await rescue. Within minutes of the crash, Glenn McDonald’s barge arrived on the scene, and his crew began pulling stranded passengers out of the water. Several shrimp boats eventually arrived as well, their crews choosing to dump their catches to make room for survivors. By the time emergency crews found the plane some 30 minutes after the accident, McDonald and the shrimp boats had already rescued practically everyone, an act of heroism for which everyone involved will be eternally grateful.
Unfortunately, a head count after the rescue revealed that three passengers — two young women and an older man — had drowned in the shallow water after believing their seat cushions would keep them afloat. A crash which could have been remembered as a miracle had instead turned into a tragedy.
As investigators from the National Transportation Safety Board made their way to Pensacola, recovery crews used a crane to lift the partially submerged plane out of the water and carried it by barge it to a nearby shipyard. The visible damage was surprisingly minimal, and in isolation it could have been repaired, but inspectors from National Airlines found that prolonged exposure to seawater had initiated widespread corrosion, as a result of which the plane had to be written off and torn up for scrap.
Meanwhile, investigators faced two main questions: why did the plane come down in the bay five and a half kilometers short of the runway, and why did three people drown after an otherwise survivable crash?
The cause of the fatalities turned out to be relatively simple. Because this was an overland flight, the plane didn’t need to be equipped with water survival gear such as life rafts and buoyant seat cushions, while passengers were under the impression that all planes had these features. Overland flights also didn’t require discussion of water survival equipment during the passenger safety briefing, removing the most obvious opportunity to correct this misconception. In fact, this mistaken belief was so widespread that even the crewmembers believed their seat cushions could be used as flotation devices. This myth originated from the fact that planes outfitted for long-range flights over water often did have seat cushions which can be used in this way, and on these flights the presence of buoyant cushions was always pointed out to the passengers; however, no airplane was specifically required to carry such cushions. Passengers and crewmembers who had heard safety briefings on overwater flights thus assumed that all airplanes carried the same equipment. In fact, flight 193 wasn’t even required to carry life jackets. Federal Aviation Administration regulations only required flotation devices (life jackets and/or some other device) if the plane was to be operated over water of “such size and depth that life preservers or flotation means would be required for the survival of its occupants.” Escambia Bay, which was only a few kilometers wide and rarely more than a few meters deep, didn’t qualify. The passengers were lucky that National Airlines had decided to equip all its 727s with life jackets anyway; had the airline not done so, more might have died.
The sequence of events which put flight 193 in the bay in the first place proved to be more complicated. The error chain began when the controller gave instructions which caused the flight to intercept the final approach course too close to the runway. This would have been justifiable grounds for the controller to terminate the approach, but he didn’t do so because the pilots didn’t tell him that they were experiencing any difficulties. The controller’s failure to inform the pilots that they would intercept the final approach course inside the approach fix caused the before-landing checklist to be delayed. Because the pilots expected to begin the checklist while a certain distance away from the approach fix, and the controller never mentioned this distance, the cue to perform the checklist never came. As a result, they began the descent to the MDA without being properly configured. While descending in a low-drag configuration, the captain reduced thrust to idle to achieve his desired airspeed. However, once the plane was in the proper high-drag configuration, he failed to add thrust back, resulting in a descent rate that peaked at twice the nominal value.
Normally during final approach, both the captain and the first officer would monitor their descent rate and altitude to make sure any deviations are quickly spotted. The reason that the plane must be fully configured prior to passing the FAF is so that monitoring parameters and looking for the runway can take center stage. In this case, however, the delayed before-landing checklist ate into the time they were supposed to spend monitoring the final approach; as a result, the pilots did not see that their descent rate was 2,000 feet per minute. In interviews with the NTSB, the pilots further added that their “internal clocks” were still tuned to a descent rate of 1,000fpm. After many similar approaches, a pilot gains an intuitive understanding of how long it takes to get to a certain point and when certain tasks must be performed; however, this approach was not similar to previous ones they had flown. As a result, several important items were missed. For example, First Officer Sanderson didn’t make the required altitude callouts, which start at 1,000 feet, because he “never got to 1,000 feet mentally.” He was used to a certain amount of time passing before reaching this altitude and he never transitioned into the mental mode in which he expected to make altitude callouts.
It is important to remember how quickly the situation really unfolded. The onset of the steeper-than-normal descent occurred only 44 seconds before the plane impacted the bay. For the first 25 of those seconds, the crew rushed through the before-landing checklist. (During some of this time, Sanderson was also looking outside the plane for the runway.) At about second 26, the GPWS sounded, and continued to sound for around nine seconds before the Flight Engineer Stockwell turned it off. During this time, the plane descended below the MDA. Around six seconds after turning off the GPWS, Stockwell reset the system, but it normally took four seconds to boot up, and only three more seconds passed before the plane crashed into the water. With this in mind, it is easy to see how the distraction of the delayed checklist caused the pilots to miss the danger of the situation until it was too late. Studies in the 1970s showed that pilots only spent around 3–5% of their instrument-scanning time looking at the altimeter. When coupled with distractions like looking for the runway or performing a checklist, it’s plausible to go 44 seconds without checking the plane’s altitude (although it must be emphasized that this doesn’t excuse the pilots’ failure to do so). Furthermore, both Kunz and Sanderson claimed they misread the airplane’s altimeter during the final portion of the descent. The 727 used a “drum-pointer” altimeter where hundreds of feet were displayed on a dial, while thousands of feet were shown on a rotating drum. The thousands drum was hard to see, however, and studies had shown that pilots often didn’t look at it (although they were usually not aware of this omission). Thus, having not mentally passed 1,000 feet, Kunz saw “500” on the dial and assumed this meant 1,500 feet. Sanderson said he made the exact same error at 100 feet.
All the aforementioned factors came together to cause the crew to ignore the GPWS warning. All three pilots knew that the GPWS could be triggered if they used a descent rate greater than 1,700fpm while below 2,500 feet; considering that this might be the reason for the warning, Kunz resolved to decrease their rate of descent until the warning stopped. In reality, Kunz had not made a large enough input to correct the problem; the GPWS actually went silent because Stockwell had turned it off. (The warning was so loud — around 100 decibels — that normal communication was almost impossible, and his misinterpretation of Kunz’s statement is entirely believable.) Simultaneous with the onset of the alarm, Kunz said he glanced at his altimeter and saw 1,500 feet, and when he looked outside he could see no terrain through the darkness and fog. The coincidence of these elements led him to believe that the plane was no longer in danger when the warning went away. But the NTSB found it frustrating that Kunz’s first reaction to the ground proximity warning telling him to “pull up” was not in fact to pull up; at the very least, he should have attempted to positively ascertain their actual proximity to the ground. Ironically, the other set of warnings related to their altitude — the lights that came on when they passed the MDA — ended up being completely overshadowed by the GPWS, and none of the pilots saw them.
At the end of its report, the NTSB criticized the pilots’ professionalism, primarily in their failure to respond correctly to the GPWS. But the board also praised their actions after the crash, which helped ensure those who were seriously injured did not drown once the plane began to sink. Further praise was reserved for Glenn McDonald and the other boaters, who also contributed greatly to the survival of 55 of the 58 passengers and crew.
Although the NTSB report on the crash didn’t include any recommendations, a lot has changed since the crash of flight 193. Pilots are rigorously trained to react immediately to GPWS warnings. Drum pointer altimeters have almost completely disappeared. Crew resource management training has helped pilots distribute workloads more effectively, leading to fewer situations in which no one is monitoring the instruments. And flight attendants are required to mention all available water survival equipment even if the flight is over land.
However, flight 193 offered several additional lessons in the area of passenger safety, particularly the use and availability of flotation devices, which could use more scrutiny. In fact, FAA rules for flotation devices on airplanes have not appreciably changed since 1978. There were, and remain, three levels of water survival gear that could be required on a given flight. The highest tier is for flights over water more than 50 nautical miles from the nearest shore; these flights must have rafts, signal flares, life vests, and several other items. The middle tier is for flights which may go over water, but not more than 50 nautical miles from land; these flights must have an “approved flotation means for each occupant,” which might be a life vest or a buoyant seat cushion. Finally, overland routes — like National Airlines flight 193 — need not have any flotation devices at all. Individual airlines and manufacturers have made some improvements; namely, almost every airliner now flying in the US comes with seat cushions that meet minimum buoyancy requirements, which the cushions on flight 193 did not. The myth of the seat cushion as a flotation device is now, with few exceptions, reality. Furthermore, many airlines equip all their planes with life vests so that they can use any plane on both overland and overwater routes. This came in handy when US Airways flight 1549 ditched in the Hudson River in 2009. That flight was considered overland and wasn’t required to have any flotation devices, but US Airways had equipped the plane with life vests so that it could perform overwater flights if needed.
The problem is that not every airline does this, because they aren’t required to. Although airlines are increasingly choosing to stock life vests, it remains entirely possible that you could be on a US airliner flying up to 50 nautical miles from land with only a seat cushion to hang on to if you end up in the water. And studies have shown that in practice, a person trying to hang on to an airplane seat cushion for flotation has only a few minutes before the cushion is swept away by a wave, the person loses their grip, or some other event takes place which renders the device useless.
While this fact has been the primary driver for airlines to stock life vests, there is also a vocal segment of the aviation community which believes life vests are actually useless. Among the points commonly cited to support this view is the fact that most people don’t put their life vests on correctly. For example, on US Airways flight 1549, only four people correctly fastened their waist straps to keep the vests in place after entering the water. In fact, only 33 passengers on that flight donned life vests at all. Had all these passengers decided to go without, the death toll still would have been zero. The argument further notes that most water landings happen without much prior notice, and a life vest takes too long to put on when trying to escape a plane that is filling with water. In reality, this argument suggests that not enough time has been taken to research historical water landings. Several such accidents, such as ALM flight 980 (1970), Ethiopian Airlines flight 961 (1996), and Tuninter flight 1153 (2005) involved sufficient time for everyone to put on their life vests before touchdown. In two of these accidents, rescue was an hour or more away, so it’s hard to argue that life vests didn’t save lives. However, two of these accidents also involved people inflating their life vests while still inside the plane, which led to unnecessary deaths. So are life vests really a net positive? Well, no one actually knows, because no scientific studies have been conducted to answer this question. It seems that after so many decades, it might be useful for the FAA to set up a study and settle the debate once and for all. Only then will we know whether the rules for flotation devices ought to be changed.
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