By Ashley Williams, AccuWeather staff writer
Nelson Marinho holds a photo of his son Nelson Marinho, seen with his family, a passenger on Air France flight 447 that was reported missing on its way from Rio de Janeiro to Paris, Wednesday, June 3, 2009. Brazil's military found a 3-mile (5-kilometer) path of wreckage in the Atlantic Ocean, confirming that the jet carrying 228 people crashed in the sea, according to Defense Minister Nelson Jobim. (AP Photo/Patricia Santos)
On May 31, 2009, Air France Flight 447 took to the skies at 7:29 p.m., Brazilian Standard Time, from Rio de Janeiro Galeão Airport with 216 passengers and 12 flight and cabin crew members on board. The scheduled flight was due to fly into Paris Charles de Gaulle Airport after just over 11 hours in the air, crossing the equator, which separates southern and northern portions of the Atlantic Ocean.
Three experienced pilots were on board: Captain Marc Dubois, a 58-year-old Air France veteran who had flown with the airline since 1988 and had more than 10,900 flying hours under his belt; 32-year-old first officer and co-pilot Pierre-Cèdric Bonin, approaching his sixth year with the airline; and 37-year-old first officer and co-pilot David Robert, who had flown over 4,400 hours on Airbus 330 aircraft.
The flight started off as fairly routine, according to Captain Shem Malmquist, an accident investigator, visiting professor at the Florida Institute of Technology's College of Aeronautics and co-author of “Angle of Attack: Air France 447 and the Future of Aviation Safety.”
"Across the equator is a band called Intertropical Convergence Zone, where the air from the southern and northern hemispheres converge,” Malmquist told AccuWeather. “Where that happens is essentially a continual band of low pressure, which makes it very easy for thunderstorms to grow, so there’s always weather along that route in various areas.”
Severe thunderstorms were reported in the area where the aircraft flew; however, no crews flying a similar route in the same time periodreported any unusually severe weather, according to AirSafe.com.
The captain and one of the first officers were initially at the front of the plane at the aircraft’s departure from Rio. Captain Dubois eventually took time to rest. “Departing in the fairly early evening, no one is really going to be tired enough to sleep right away. So, the captain did what is very typical and chose the middle rest period.” The in-flight weather radar showed nothing out of the ordinary prior to his retreat.
The two pilots in the cockpit eventually noticed a bit of weather occurring in the path ahead, Malmquist said. “They did turn the radar gain up, which allows them to pick up more of the frozen particulate, because aircraft in-flight weather radars usually are not very good at picking up anything other than wet water,” Malmquist said.
(AP Photo/Francois Mori)
The pilots then took the plane on a slight turn when they began experiencing what sounded like hail falling. It turns out that they’d lost all three air speed indicators while flying in high, thin air at 35,000 feet.
“Coupled with the loss of air speed indicators, it also led to altimeter errors and a few other things, like the loss of the autopilot,” Malmquist said. Records showed no distress or emergency signalssent from the crew, though the plane itself sent several automatically generated maintenance messages back to Air France, according to AirSafe.com.
At this point, the crew struggled to keep the wings level, according to Malmquist. During their attempts, the aircraft’s nose slowly crept upward, entering the plane into an aerodynamic stall. “One of the problems is we really don’t train pilots on how to recognize or what an aerodynamic stall looks like, especially in a big airplane at high altitude,” Malmquist said, adding that pilots tend to equate what they’ve experienced in smaller airplanes or in simulators with what a stall should be.
The pilots tried to call Captain Dubois back to the cockpit just after the stall occurred; he returned about 90 seconds into it. Unfortunately, said Malmquist, the three of them ran out of time to sort out the problem. “If [the captain had] been up front in the first place, it probably wouldn’t have happened,” he said.
Members of the Brazil's Navy recover debris from Air France Flight 447 in the Atlantic Ocean. (Brazil Air Force)
Weather’s role
Malmquist noted that something not commonly taught to pilots is that storms over the ocean in tropical regions, particularly those that happen at night, tend to “rain out” by about 20,000 feet, which means that liquid water lies below this point, while everything above it is frozen.
“It slowly percolates up and re-energizes at about 30,000 feet. In that process, they create these high-altitude ice crystals,” Malmquist said. The pilots on the doomed Flight 447 encountered an area of such crystals, and they weren’t scanning low enough in the air to see that they were entering a convective area.
“They were looking up too high and setting the radar tilt where you would if you were trying to avoid a storm over Kansas, and it just doesn’t work over those oceanic areas,” Malmquist told AccuWeather.
Encountering these ice crystals overwhelmed and obstructed the pitot tubes, which are devices that measure air speed as well as the impact pressure of air. This led to the loss of the plane’s air speed, disconnection of some of the plane’s automatic systems and the pilots receiving incorrect speed indications.
“In this case, the high-altitude ice crystal phenomena were really just not well-known,” Malmquist said. The time between the aircraft stalling to the time that it violently crashed into the sea on June 1, 2009, was just three minutes.
All 228 souls on board perished, forever altering the lives of the families they left behind.
Along with some bodies of the passengers, several pieces of the wreckage and debris — but not all — were recovered in the days, weeks, months and years following the accident. An investigation from the Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA), an agency of the French government, found that the plane was largely intact when it hit the water’s surface, with no oxygen masks released or life jackets out of their containers.
Workers unload debris belonging to crashed Air France Flight 447 from the Brazilian Navy's Constitution Frigate in the port of Recife, northeast of Brazil, Sunday, June 14, 2009. (AP Photo/Eraldo Peres)
RELATED:
5 years after MH370's disappearance: Will the search continue in the greatest aviation mystery of modern history?
Exploring the weather hazards behind 5 deadly, notorious plane crashes
7 different types of turbulence and how pilots navigate this nuisance while flying
Why it's so critical to deice planes prior to takeoff
In addition to the blocking of the pitot tubes by ice crystals, the BEA attributed the crash’s cause to factors including the crew’s failure to make the connection between the loss of indicated air speeds and the appropriate procedure necessary to save the plane; the crew not identifying the approach to stall; and the crew’s failure to diagnose the stall situation, which led to a lack of actions that would have made the plane’s recovery possible, according to the final crash investigation report.
Changes since the crash
“I don’t think the aspect of understanding or interpreting the weather was really realized during the initial investigation. It was focused really on how the pilots responded to it,” Malmquist said. “I’d say pretty much nothing has happened in terms of improving pilot training for weather avoidance, unfortunately.”
However, stall training has seen some changes and improvements since the deadly Air France Flight 447 crash a decade ago.
“Just introduced [in 2019] was expanded envelope training, and simulators had to be reprogrammed to better replicate the effects of stalls at altitude,” Malmquist said. It’s not perfect, he added, because its limitations mean that due to the amount of force and the way a stall actually feels in a large airplane at altitude, if a pilot were to replicate the stall on a simulator, it could actually break the simulators.”
“They’re just not made for that kind of force and vibration,” he said. Adding to the issues with stalls is that pilots generally don’t recognize them if they’re not anticipating them. “This is an ongoing issue that when they’re not anticipating them, they tend to discount it,” Malmquist said.
No comments:
Post a Comment