On the morning of August 14, 2005, the Greek Air Force F-16 fighter pilots approached the Boeing 737, which was no longer communicating. The military pilots saw an alarming picture: the commander's seat was empty, the co-pilot was lying on the control panel, at least three passengers were wearing oxygen masks, but they were unconscious. Thirty minutes later, the liner crashed about 40 kilometers from Athens. None of the 121 people on board survived, and in a year, Helios will shut down. All of this is due to a small switch that confused experienced pilots and caused a lot of trouble.
Hunger
The Boeing 737-300 of the small airline Helios Airways operated flight 522 on the Larnaca-Athens-Prague route. Almost immediately after departure from the Cypriot city, the liner started having problems. A warning about the unavailability of the plane for takeoff was activated, but it was already in the sky. Further, the alarm reported a malfunction in the air supply system. The crew contacted the ground engineer. They began to sort out the situation. The commander suggested that the problem was in the air supply system. He asked where the A / C circuit breaker is located in the Boeing 737. The specialist replied: "Behind the commander's chair." This was the last communication with flight 522.
The problem was quite different: the plane's pressure in the cabin dropped, and the higher it climbed, the faster it happened. When the liner reached an altitude of 4,250 meters (14 thousand feet), oxygen masks fell out in the cockpit. For some reason, this didn't bother the crew - they didn't even wear them. Signs of oxygen starvation are difficult to recognize. They can be compared to mild intoxication: fatigue, dizziness, disorientation, trouble concentrating. The pilots were looking for the cause of the malfunction and did not notice the symptoms in time.
At an altitude of about 5,500 meters (18,200 feet), the masks fell out in the passenger compartment. The exact actions of the stewards are unknown, but they were supposed to use oxygen tanks, help passengers put on masks and wait for the commander's message. But the pilots were already unconscious by that time. The liner flew under the control of automation.
Promotional video:
Wrong password. Try again
At least one of the crew members was able to get to the oxygen tank. 25-year-old steward Andreas Prodromu was in a terrible situation: everyone around was unconscious, the pilots did not give instructions, and a bulletproof door with a combination lock separated him from the cockpit. All would be fine - the guy studied piloting and could land the plane. But the problem is that he did not know the password for the door to the cockpit. According to the instructions, only the senior flight attendant had the code.
Such a strict condition appeared after September 11, 2001. Regulators and airlines have begun to improve flight safety. The changes affected the passage to the cockpit - now it was not easy even for flight attendants to get into it. As the case of Flight 522 showed, aviation experts solved one problem and caused another. If Prodromu had immediately got into the cockpit, it is possible that the disaster could have been avoided.
But the steward only got inside two hours later - it is still unclear how. Perhaps he entered passwords at random, or he managed to revive the senior flight attendant and find out the code. All this time, the dispatchers unsuccessfully tried to contact the Boeing 737 and did not understand why the board was silent. In such a situation, the worst can be assumed - capture. Remembering all the same on 11 September, Greece sent two combat F-16s to intercept. The fighters had to visually examine the condition of the aircraft and establish contact with it. Confirm the fears of the authorities - the liner could have been shot down so that the terrorists would not send it to the metropolis.
The last photo of the crashed Boeing 737 was taken by a fighter pilot.
After about 15 minutes of observation, a man without an oxygen mask appeared in the cockpit, who tried to take the commander's place. It was Andreas Prodrom, who managed to open the door. He took control. The pilot of one F-16 made a maneuver to attract attention, and soon there was a reaction: the steward waved his hand. The Boeing 737 was running low on fuel. The first engine stopped. The flight attendant gave a distress call - "Mayday" in a weak voice. However, the link was tuned to a different frequency and he was not heard. Soon after, the second engine froze. The plane planned until it crashed into a hill near Athens. All 115 passengers and 6 crew members were killed. No one died of hypoxia itself: the study of the remains showed that the death of people occurred during the crash of the liner.
Other passengers are very lucky
The F-16 pilots gave investigators valuable information about unconscious people and hanging oxygen masks. Experts began to look for the reasons for the depressurization. For such a case, as well as for many others, instructions are provided for the crew. By itself, the pressure drop (unless, of course, it is explosive, as was the case with the DC-10) cannot destroy the aircraft. The pilots have enough air to react and descend to a safe altitude, where hypoxia will not lead to loss of consciousness and the liner can be brought to the airport. The question is why all warnings, including dropped masks, were ignored.
Investigators began to study the biography of the pilots, the history of the aircraft and the airline. The deeper they dug, the more problems they found. Helios Airways saved on almost everything, including maintenance and crew training. The crashed Boeing 737 has had depressurization incidents before. In December 2004, this liner flew from Warsaw to Larnaca. Everything happened exactly as on the last flight: pressure drop, alarm, masks dropped. The flight attendant then noticed that a palm was passing through the gap between the door and the fuselage. The plane managed to land, but there were injuries: due to a sharp drop in pressure, three passengers complained of ear pain, they were hospitalized.
Special attention of experts was attracted by an incident that occurred on the eve of the disaster. Before the fatal flight, the liner was heading from London to Larnaca. During the flight, the crew noticed that one of the doors was frozen over, and strong blows were heard. The plane landed safely. The crew immediately reported the problem, and ground specialists began to test the door - if the problem was confirmed, it would be necessary to urgently change transport for the morning flight to Prague.
Freezing clearly indicated problems with tightness. The engineers simulated the pressure during the flight. Usually, an automatic system is responsible for this, which keeps conditions comfortable for a person at a height. But in some cases - for example, when simulating a problem on the ground - the system needs to be switched to manual mode, which the workers did. It was not possible to identify the problem - the interior withstood the pressure without leaks. The liner was allowed to the next flight. The craftsmen did everything according to the rules, with the exception of one detail. They did not return the pressure maintenance system to the automatic position. Nobody noticed this, including during the pre-flight check by the crew.
The switch on the bottom right turned out to be in MAN mode, while it should have been in the AUTO position.
But this still did not explain why experienced pilots (the commander's flight time was almost 17 thousand hours, the co-pilot's - 7.5 thousand hours) missed several alarms. It turned out that the crew misunderstood the system warning: the pressure drop signal is similar to what pilots hear on the ground when the aircraft is not ready for takeoff - for example, when the flaps are not extended or the brakes are activated. By that time, the liner was already in the air, and the pilots thought that the system worked by mistake. They did not take into account that the same signal could indicate a completely different problem.
Further warnings confused the crew more and more as the plane continued to climb, which only made people faint faster. The commander still believed that the problem lay in the air supply system. In fact, this was a consequence, not a reason: the automation reacted to the pressure change and turned off the fans. Hypoxia also began to influence the criticality of thinking. Apparently, in a stressful situation, the crew did not notice symptoms and lost consciousness.
***
Helios Airways existed for only a year after the disaster: by the decision of the Government of Cyprus, the carrier's accounts were frozen, and the company was gone. In 2012, a Greek court handed down a sentence to four airline employees: ten years in prison for manslaughter and negligence.
Author: Stanislav Ivaneiko
