It was a normal day in London. The pilots and the passenger had woken up very early in the morning to get ready for the flight to Larnaca, Cyprus from London, England. During the flight the crew saw that the Boeing 737’s door seals had frozen. There were also strange noises coming from the right aft service door. They did what they were supposed to so; they reported it and requested a full inspection of the door. There came a full inspection as was requested. The inspection was carried out by a ground engineer who worked at Larnaca Airport. The engineer then performed a pressurization leak check. He did not fly the plane or start the engines. To do a pressurization leak check you need to switch the pressurization system to ‘manual’. He also did that. He did not however switch the system back ‘to automatic’. The ground engineer did not find any abnormalities so he just approved the plane. The Boeing went into service. A new crew came. The new crew did the pre-flight procedure, the after-start check, and the after take-off check. During all of these procedures and checks neither of the pilots saw that the small button was switched to ‘manual’. The pressurization system was still switched to ‘manual when the plane took off heading towards Athens International Airport at nine o’clock. The aft outflow valve was left partially open. As the airplane climbed the air became thinner and thinner. At 12,040 feet the cabin altitude alarm sounded because the air pressure was so low. Someway the crew made the mistake of thinking that the alarm was from the take-off configuration warning. Which is strange because that alarm can only sound when the plane is on the ground. The plane was still climbing. It had an altitude of 18,000 feet. At that point the oxygen masks in the passenger cabin automatically deployed. Then the pilots contacted the same ground engineer that that switched the pressurization system to ‘manual’. The pilots reported seeing issues like
“the take-off configuration warning on” and “cooling equipment normal and alternate off line”. The ground engineer responded to that by asking: “Can you confirm that the pressurization panel is set to AUTO?”
The captain was experiencing the onset of hypoxia’s initial and disregarded the question and instead asked in reply, “Where are my equipment cooling circuit breakers?”. Hypoxia is a condition in which the body does not get enough oxygen. It dramatically affects performance. A person who gets hypoxia will after a couple of minutes will lose consciousness and a little bit after that that person will eventually pass away. Hypoxia often occurs at high altitudes. That is why on high mountains people need oxygen tanks.
After that there was no communication with the aircraft anymore.
The pilots did not know that that was the last contact they would make with anyone outside the plane. After a couple of minutes the pilots became unconscious and the plane kept climbing to flight level 340 about the same as 34,000 feet. The plane remained in the holding pattern under the control of the autopilot for the next 70 minutes until its fuel ran out. Before its fuel ran out the air traffic control tried to make contact, but was unable to actually do so. The air traffic control got so worried that they called two F-16 fighter aircraft from The Hellenic Air Force to come. The Hellenic Air force belongs to Greece. The reason that the Hellenic Air Forces were activated and not the forces from Cyprus for example was that the airplane was flying in greek airspace.
They intercepted the passenger jet and observed that the first officer was slumped motionless at the controls and the captain’s seat was empty. They also reported that oxygen masks were dangling in the passenger cabin.
Seven minutes later flight attendant Andreas Prodromou entered the cockpit and sat down in the captain’s seat, having remained conscious by using a portable oxygen supply. Prodromou held a UK Commercial Pilot Licence,but was not qualified to fly the Boeing 737. Crash investigators concluded that Prodromou’s experience was insufficient for him to be able to gain control of the aircraft under the circumstances. Prodromou waved at the F16s very briefly, but almost as soon as he entered the cockpit, the left engine turned off due to fuel exhaustion and the plane left the holding pattern and started to descend. Ten minutes after the loss of power from the left engine, the right engine also turned off and five minutes after that the aircraft crashed into hills near Grammatiko, 40 km (about 25 mi) from Athens, killing all 121 passengers and crew on board. The young flight attendant had not succeeded to save the plane and the people aboard.
The crew that flew from London requested that inspection because they were worried about the potential safety consequences of that. If they did not request the inspection, then probably the next crew and passengers would not crash and die as a result of it.
The crash left a legacy. The training of the pilots became more elaborate in what to do in such situation and there came a digital procedure so that the pilots do not overlook anything.
I think that it is strange that the pilots failed to notice that the pressurization system was on ‘manual’ because ‘turn the pressurization to ‘auto’ was on all three lists. I also think its strange that although the pilots had oxygen masks they were suffering of hypoxia.
You can read about the crash on Wikipedia here.
You can read about the crash on The Guardian here.