You are watching: The plane that flew too high
The aircraft affiliated in the accident. Image source: Andrés Dallimonti
West Caribbean Airmethods was a local airline serving assorted destinations in Colombia, Central America, and also the Caribbean. Founded in 1998, the airline initially operated little twin turboprop Let L-410s, yet soon upgraded to jet operations via the introduction of several McDonnell Douglas MD-82s, which it used both for scheduled solutions and charter flights. By 2005, the airline had currently occurred a troubled background. In March of that year, a West Caribbean Let L-410 cramelted shortly after takeoff from the island also of Providencia, killing 9 of the 14 civilization on board. Investigators uncovered that an engine failure had emerged on takeoff, and the pilots faicaused follow established engine out steps, bring about a loss of manage. Shortly after this accident, Colombian authorities fined the airline twice for safety and security violations. The initially time, they were recorded overloading a plane. Then the second fine came after authorities found that the airline had actually been violating crew rest minimums, failing to carry out compelled training, and keeping inconstant documents. All these difficulties caused the airline to autumn into significant financial trouble. By August 2005, just among West Caribbean’s 3 MD-82s was airworthy, as the other 2 were grounded pending maintenance for which the airline was unable to pay.
The course of flight 708. Map source: Google
It was against this background that West Caribbean Airmeans prepared to usage its one operational McDonnell Douglas MD-82 to move a group of tourists from the French Caribbean island also of Martinique ago home after a trip to Panama. The charter flight from Tocumales Internationwide Airport in Panama City to Fort de France Le Lamentin Internationwide Airport on Martinique had been booked by a Martinique-based travel firm, and virtually every one of the 152 passengers consisted of the tourists and their guides. Eight crewmembers additionally boarded the airplane, including 40-year-old Captain Omar Ospina and also 21-year-old First Officer David Muñoz, and four trip attendants, a maintenance technician, and an airline dispatcher. By the moment the airplane arrived in Panama City, it was currently running late — the preceding trip from Colombia was delayed because West Caribbean Airmethods had not phelp for the fuel.
Before takeoff, the crew filed a flight arrangement via Panamanian authorities. The plan made no point out of weather problems, despite a line of storms stretching across Panama’s east coastline and also dvery own right into Colombia and Venezuela. They additionally stated a cruising altitude of 35,000 feet, which was better than the MD-82 can safely fly under its current weight and also configuration. However, West Caribbean Airmethods flight 708 was cleared to fly, and the airplane took off from Panama City at 1:00 a.m. local time.
As trip 708 climbed toward its initial cruising altitude of 31,000 feet, the pilots detailed the weather problems ahead and turned on the engine anti-ice devices. Engine anti-ice diverts hot bleed air from the engines’ compression chambers and cycles it via a mechanism of tubes, heating the exterior of the engine to prevent the buildup of ice. However before, bereason the device siphons off some of the airflow though the engine, it reasons a reduction in power output while it’s active.
At 1:39 a.m., the pilots obtained clearance to climb from 31,000 to 33,000 feet. However, at their present weight through engine anti-ice on, it would not be possible for the engines to geneprice sufficient power to remajor at 33,000 feet. The pilots might have actually shown this using the aircraft performance tables in the trip hands-on, however they appeared not to have actually done so.
31,900 feet was the highest that flight 708 need to have actually been able to fly under the scenarios. Image source: Mayday
As flight 708 progressively climbed toward 33,000 feet, Captain Ospina ordered First Officer Muñoz to revolve the engine anti-ice off in order to boost climb performance. This showed adequate to acquire the plane to 33,000 feet. After leveling off, the pilots adjusted the autothrottle mode from “climb” to “cruise.” The autothrottle, the device which immediately adjusts engine power over the course of the trip, has variable settings that permit the pilots to collection just how a lot power it is permitted to geneprice. The maximum engine power that the autothrottle deserve to command also in cruise mode is much less than it deserve to command in climb mode. The pilots also commanded the autothrottle to keep a speed of 268 knots (496km/h), which it was just barely able to perform in cruise mode through engine anti-ice off.
As trip 708 tracked to the south, trying to discover a path with the storms, the pilots aobtain came to be came to around ice. At 1:48, they turned the engine anti-ice units earlier on. In this configuration, the autothrottle might not command also sufficient power in cruise mode to maintain the schosen airrate of 268 knots. Their speed slowly started to decrease, and also the autothrottle mode indication changed to “Mach ATL” to alert the pilots to the truth that the autothrottle was unable to reach the desired airrate. However before, neither of them noticed, probably bereason a trip attendant had actually just carried them dessert.
The airplane was now in a dangerously unstable position due to a standard principle of fluid dynamics. In standard terms, lift is a function of airrate (the velocity of the aircraft family member to the bordering air mass), air thickness, wing area, and angle of attack (the pitch angle of the plane family member to the direction of airflow). When flying directly and level, air density and also wing area are roughly constant, while airspeed and also angle of attack deserve to change. To keep a constant amount of lift (and therefore level flight), any decrease in airspeed need to be countered by a matching rise in angle of attack. Otherwise, lift will decrease and also the airplane will certainly descfinish. On West Caribbean Airmeans trip 708, the autothrottle was unable to apply enough engine power to maintain the compelled airspeed. However before, the pilots had collection the autopilot to “altitude hold” mode, commanding it to preserve an altitude of 33,000 feet. To host the aircraft this level, the autopilot had actually to maintain the amount of lift acting on the aircraft despite the loss in speed. Because of this, it boosted the angle of assault to keep the equation well balanced.
A in-depth explanation of the partnership between lift, rate, and also angle of strike. Image source: the CIAA/JIAAC
Over the next numerous minutes, the plane’s airrate ongoing to drop, and also the autopilot ongoing to boost the angle of attack to compensate. At 1:52, the pilots turned the engine anti-ice off. However, within the minute, Captain Ospina turned it back on, and likewise switched the autothrottle from cruise to climb. But while max climb power would have actually been adequate to maintain 33,000 feet earlier in the flight, this was no much longer the case.
Perhaps counterintuitively, the amount of engine power required to preserve a particular rate at a details altitude adheres to a parabolic trajectory, which in the case of trip 708 was centered on a speed of 256 knots. Both over and also listed below this crucial rate, the amount of engine thrust essential to maintain a consistent velocity rises. Because of this, as flight 708 decelerated past 256 knots, the amount of extra thrust required to proccasion the ongoing loss of rate progressively raised, till the power compelled was higher than the power easily accessible in any configuration. In such a situation, an aircraft is sassist to be “behind the power curve,” and the only way stabilize the trip is by pitching dvery own to descfinish. As an outcome, the pilots’ decision to switch the autothrottle to climb mode came also late, bereason they had actually currently decelerated as well much for the additional power accessible in this mode to gain the aircraft back ahead of the power curve.
What is the power curve? Image source: the CIAA/JIAAC
By 1:57, the autopilot had actually raised the plane’s angle of assault to even more than 7.5 degrees, far past a normal value for cruise. At this allude, First Officer Muñoz said that they to descend earlier to 31,000 feet, although he didn’t voice his factors for doing so. Captain Ospina agreed, and they got permission from air website traffic control to start the descent. But till they descended much sufficient to obtain back ahead of the power curve, their speed continued to decay and the angle of attack continued to increase. 35 secs into the descent, at an altitude of about 31,700 feet, the airplane gotten in a pocket of disturbance. A significant updraft struck the plane from below, resulting in a additionally spike in its angle of strike. At the same time, the high angle of attack resulted in a space of unstable air to create behind the wings, interrupting airflow into the tail-installed engines and resulting in a drop in power output. This put the aircraft dangerously close to a stall, in which the angle of attack becomes so excellent that air stops flowing smoothly over the optimal of the wings and also lift starts to decrease. To warn the pilots of the impending stall, an audible “STALL!” warning started to blare, accompanied by the stick shaker, which physically shakes the pilots’ control columns. This was a authorize that they essential to automatically pitch dvery own and also rise power to acquire rate and also reduce their angle of strike.
As angle of strike increases, air circulation behind the wing becomes increasingly disrupted. Image source: safepilots.org
First Officer Muñoz instantly well-known the difficulty. “It’s a stall, Capi!” he exdeclared. “It’s a stall!”
But Captain Ospina didn’t react to his initially officer’s comments. Instead, he seemed to be focused on the engine gauges, which proved a loss of thrust in both engines. The reduction in thrust remained in reality a symptom of a stall, but Ospina appeared to believe that the engines were the resource of the difficulty. Instead of taking any activity, he ordered his first officer to request a lower altitude from air traffic regulate, and also Muñoz dutifully obeyed!
The airplane then stalled and also started to loss from the skies, descending at a rate of 5,000 feet per minute, speeding up downward ever much faster with each passing moment. Neither pilot took any type of action to recover from the stall, and also in truth Captain Ospina made it worse by including nose up stabilizer trim. No one began or even mentioned any type of emergency checklist.
At 1:58, the air web traffic controller, perplexed by the crew’s request for a rapid descent, called and also asked, “Do you have any problem on board?”
To Muñoz, Ospina shouted, “Affirmative, tell him we have actually flame out on both engines!” Once aacquire, Muñoz passed this on to ATC.
“Roger, proceed descent at pilot’s discretion,” the controller replied.
By now they were plunging downward at an astonishing rate of 12,000 feet per minute. At 1:59, Muñoz reported to ATC, “We are at 14,000 feet!”
“And going down!” shelp Ospina. “The aircraft is uncontrollable!”
“The airplane is uncontrollable!” Muñoz recurring to ATC.
“Roger, confirm human being on board, intention, and distance from any kind of nav assist if feasible,” shelp the controller.
“One hundred and fifty two!” Muñoz gasped. “The aircraft is uncontrollable!”
The plane had actually currently entered what is well-known as a deep stall. On T-tail aircraft prefer the MD-82, it is feasible to enter a stall perspective in which the wings completely block the circulation of air over the elevators, staying clear of the pilots from controlling the plane’s pitch. Once a airplane has entered such a condition, recoextremely is impossible.
“I understand also, 152 civilization on board,” the controller replied.
“Affirmative!” sassist Muñoz.
“Confirm what level are you crossing at this time, Whisvital Charlie Whiscrucial 708?” asked the controller. But tright here was no reply.
Inside the cockpit, the pilots sassist nopoint, sitting like deer in the headlights as the aircraft plunged toward the ground. The ground proximity warning blared, “WHOOP WHOOP PULL UP, SINK RATE, WHOOP WHOOP PULL UP!” But tbelow was nothing they might do. At 2:00 a.m. and also 31 secs, West Caribbean Airways flight 708 slammed belly-initially right into a marshy field west of Lake Maracaibo, triggering a massive explosion that sent debris flying high right into the air. The influence obliterated the aircraft and also instantly killed all 160 human being on board. In a rural area in the dead of night, tbelow were no witnesses to attest to their final moments.
A simulation of the final moments of trip 708. Video source: Mayday
Upon hearing the crash, local residents rushed to aid, but they were faced with a grisly scene: bit was left of the airplane, besides the tail; much of the wreckage was burning and bodies were scattered everywhere. By the time emergency services arrived, it was clear that no one had actually survived. That made West Caribbean Airways flight 708 the most dangerous aircraft crash in the history of Venezuela. The French abroad department of Martinique was also left reeling — practically all the passengers hailed from tbelow, and few world on the island were more than a level or 2 of separation from one of the victims. Under push to uncover the cause conveniently, Venezuela’s Aircraft Accidents Investigation Committee (CIAA) invited its French, American, and Colombian countercomponents to take component in a huge worldwide inquiry.
Footage of the after-effects of the crash reveals that little bit stayed of the airplane. Video source: Mayday
Early media reports focused on the pilots’ frantic dianxiety call, in which they asserted that both of their engines had failed. But an examination of the ruined engines suggested that they were generating power at influence, and the readout from the trip data recorder evidenced this. The genuine sequence of occasions appeared to be much even more subtle. On the a lot of fundamental level, the pilots tried to fly at an altitude that exceeded the aircraft’s performance borders. With the autothrottle unable to maintain the selected airrate, the autopilot preserved increasing the angle of strike to compensate, till the AOA exceeded the instrumental allude and the aircraft stalled.
However before, this was not the first time this had occurred. In 2002, a Spirit Airlines MD-82 encountered a lot the same set of circumstances, only in that situation, the pilots reacted effectively to the stall warnings and also regot regulate of the plane. The flight diverted to Wichita, Kansas and no one was hurt. In the wake of the event, Boeing issued a bulletin to all MD-80 series operators informing them that once flying at an altitude over the aircraft’s performance limit, the autopilot could keep boosting the AOA till it stalled the aircraft. However before, there was no evidence that West Caribbean Airmethods had actually ever passed this bulletin on to its pilots. (Keep in mind that Boeing took over production of previous McDonnell Douglas aircraft types after the 2 companies’ merger in 1997.)
An aerial view of the crash scene. Image source: The Bureau of Aircraft Accidents Archives
Typically, the autopilot on the MD-82 will disconnect prior to getting to a stall. This case showed to be an exception to that rule. But that hardly abresolved the pilots, who barely did anything to fly the airplane. Upon hearing the stall warning, they have to have actually instinctively pitched the nose down and also increased power without also having to think about it. Instead, Captain Ospina came to be fixated to the allude of delusion on a regarded loss of engine power. It seemed that he totally tuned out not simply the apparent stall warnings, but additionally his copilot’s exhortation that “It’s a stall, Capi!”
But if First Officer Muñoz knew they were stalling, why didn’t he take control? Interviews via world who kbrand-new the pilots revealed that Muñoz had actually a really submissive personality, while Ospina was very a lot a leading figure in the cockpit. Compounding this dynamic was the reality that Muñoz was only 21 years old, bacount fifty percent the age of his captain. Not just would certainly he have actually been cynical to defy Ospina, he can have convinced himself that he was the one reacting erroneously after Ospina ignored the stall warnings. Furthermore, the pilots’ statements and actions (or lack thereof) were suggestive of a dissociation from truth. In the middle of the night, confused by what their airplane was informing them, they can have actually shed the capability to think rationally and identify whether they instance they were in was real. As they plummeted downward from 31,000 feet, they could have actually been asking themselves: is this fact, or just a negative dream?
Soldiers guard the crash site from looters. Image source: The Bureau of Aircraft Accidents Archives
Investigators additionally had actually to ask why the pilots attempted to fly at 33,000 feet in the initially place, and also why they didn’t notice that they were losing rate. Throughout the crucial 10-minute duration where their airrate was decaying, they appeared to be distracted by the continuous meal business, and numerous communications with air website traffic regulate as they were handed off from the Colombian sector to the Venezuelan sector. They also might have actually simply put as well a lot trust in the autothrottle’s capability to keep whatever rate they asked of it.
Anvarious other red flag was that their filed flight plan called for a cruising altitude of 35,000 feet, which verified that they were unacquainted through the capabilities of their aircraft. Many kind of of their actions over the course of the flight suggested that they likewise had actually a bad understanding of just how the aircraft would react to their inputs. This called into question the high quality of the training at West Caribbean Airways, which had currently been cited for significant training violations previously that very same year. It was clear from looking at the pilots’ documents that bit had readjusted as an outcome of the citation. Neither pilot had been trained to anticipate or recover from a high altitude stall. Their expertise of aircraft units was rudimentary at finest. And they had actually not received detailed Crew Reresource Management (CRM) training. But that was not the just disbenefit that the pilots had actually going right into this trip.
The tail was the just piece of the airplane recognizable from the air. Image source: The Bureau of Aircraft Accidents Archives
As investigators looked into the pilots’ daily lives, they uncovered that flying was more than likely not the only point on their minds. West Caribbean’s dire financial instance had actually left it unable to pay pilots on time, and Captain Ospina had actually not obtained a payexamine in 6 months. He had actually recently started a restaurant as a 2nd source of revenue, without which he would have actually been unable to feed his family. Running this organization consumed a lot of the time that he was expected to spfinish resting. Both also challenged looming uncertainty about the long-term prospects of their careers. With West Caribbean Airways teetering on the brink of insolvency, they feared waking up one morning to discover that their employer no much longer existed. The level of anxiety lugged on by these components was most likely high, but Captain Ospina’s latest recertification had no examine of his psychoemotional state, so the exact manifeterminal of this stress couldn’t be established.
Anvarious other aerial check out of the crash website. Image source: Panorama Maracaibo
Within a day of the accident, Colombian authorities inabsolutely suspended West Caribbean Airways’ operating certificate. For such a little airline to have 2 deadly crashes in a solitary year proved beyond all doubt that it need to not be flying. In October 2005, West Caribbean went bankrupt and also sold off its 4 staying airplanes.
The case of West Caribbean Airmethods flight 708 illustprices the prestige of cshed surveillance, or even preemptive grounding, of small airlines that are struggling financially. This was neither the initially nor the last situation of an airline on the edge of bankruptcy cutting corners at the expense of lives. For instance, in December 2005, Chalk’s Ocean Airmeans flight 101 cramelted after takeoff from Miami after a wing dropped off in trip, killing all 20 world on board. The company’s finances were deep in the red, its owners had been trying to unproperly to offer it, and maintenance had fallen by the wayside in an initiative to save money. And in 2016, LaMia trip 2933 cramelted in Colombia, killing 71 of the 77 civilization on board, consisting of many of Brazil’s Chapecoense footround team. LaMia, a Bolivian charter airline with just one operational airplane, had actually been in such deep financial trouble that it deliberately undersustained its airplanes in order to conserve money. On trip 2933, they cut it as well cshed, and the plane ran out of gas. After both of the previously mentioned accidents, the airlines in question were grounded, but a closer examicountry could have led authorities to shut them dvery own earlier.
Some various other recent accidents involving high-altitude stalls.
West Caribbean Airways trip 708 was likewise not the just accident involving a high altitude stall from which the pilots faicaused recover. Many famously, on the initially of June 2009, Air France flight 447 disappeared over the Atlantic Ocean with the loss of all 228 passengers and also crew. While flying through a storm, the Airbus A330’s pitot tubes, which measure airspeed, froze and stopped providing valid indevelopment. The initially officer reacted incorrectly, pitching the airplane up till it stalled. He continued to pitch up all the method until the aircraft hit the sea, supposedly never before realizing that he remained in a stall and also required to pitch dvery own. Several other comparable mishaps have actually arisen in recent years, consisting of the 2014 crashes of Air Algerie trip 5017 and Indonesia Air Asia trip 8501, which claimed an unified 278 resides. It is difficult to describe why every one of these pilots faicaused percreate among the many basic emergency maneuvers, taught from day one of trip training. But the answer could lie in the effective ability of the human brain to discard any kind of indevelopment that does not support its preconceived photo of the situation. On West Caribbean flight 708, Captain Ospina’s initial determicountry that tright here was somepoint wrong via his engines might have prevented him from assimilating indevelopment that pointed to a various resource for the difficulty.
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An artist’s work commemoprices those who shed their lives in the crash. Image source: Maria Guevara
In its final report, released in 2010, the Venezuelan CIAA recommfinished that pilots obtain much better training on exactly how to use aircraft performance tables; that airlines be forced to administer training in recoexceptionally from high-altitude stalls; that authorities continually monitor the financial state of every airline to ensure that it is capable of giving an enough margin of safety; that MD-80 series pilots be taught around mishaps involving the aircraft’s miscellaneous autopilot and autothrottle modes; that pilots obtain brand-new training on techniques to maintain situational awareness; that Boeing include an alarm or warning to inform crews that the aircraft is exceeding its performance limits; and that the design of trip information recorder offered on the plane be modified to record the aircraft’s angle of attack. It stays to be viewed whether these efforts, and those complying with the comparable crashes that have occurred given that, will certainly result a permanent reduction in pilot errors involving high altitude stalls.