What Caused The Crash Of Helios Airways Flight 522 In 2005?

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The crash of Helios Airways flight 522 is one of the most unusual and shocking aviation accidents of the 21st century. It involved a Boeing 737 that came down near Grammatiko in eastern Greece. But what exactly caused the crash of this so-called ‘ghost plane’?

Helios Boeing 737
The aircraft involved was named Olympia. Photo: Alan Lebeda via Wikimedia Commons

The flight in question

Helios Airways was a low-cost airline based in Larnaca, Cyprus. From 1998, it operated both scheduled and charter flights from the Mediterranean island nation to various European and North African destinations, stretching from Dublin to Cairo.

One of Helios’s scheduled destinations was the Czech capital of Prague, and it flew there from Larnaca under the flight number ZU522. This flight also featured an intermediate stopover in the Greek capital of Athens. Its scheduled departure time from Larnaca was 09:00 local time, and, on August 14th, 2005, it took to the skies just seven minutes late.

How did the accident begin?

Just five minutes after takeoff, the aircraft’s cabin altitude warning horn sounded, prompting the crew to halt the climb. At this stage, the plane was passing through an altitude of 12,040 feet. However, the sound was identical to that of the takeoff configuration warning, and the crew disregarded it, believing it to be this alarm instead.

Helios Airways Boeing 737
ZU522 was scheduled to stop in Athens on its way from Larnaca to Prague. Photo: Richard Janura via Wikimedia Commons

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As such, they were unaware of the loss of cabin pressure currently occurring onboard. Seven minutes into the flight, the pilots reported an air conditioning problem, and contacted the airline’s operations department. Meanwhile, oxygen masks had deployed upon reaching an altitude of 18,000 feet.

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By the time the operations center made its last contact with the crew, at 09:20 (13 minutes into the flight), communication with the pilots was becoming increasingly difficult. This was because they were beginning to experience symptoms of hypoxia as a result of the loss of cabin pressure. The aircraft eventually stopped climbing at 34,000 feet at 09:23.

ZU522 Flightpath
The flight path of Helios Airways flight 522. Image: Oona Räisänen via Wikimedia Commons

The interception

Upon entering the Athens flight information region at 09:37, the aircraft began circling on autopilot as the further loss of pressure had incapacitated the crew. With the pilots continuing not to respond to air traffic control messages, two Greek F-16 fighter jets were dispatched to intercept the flight. They took off at 11:05, and located the plane at 11:24. The fighter pilots reported a curious scene in the cockpit.

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Specifically, the captain’s seat was empty, while the first officer was slumped unconscious over the controls. They then witnessed a flight attendant enter the cockpit with a portable oxygen supply at 11:49, who, along with his partner, attempted to control the aircraft. He even acknowledged the F-16 pilots with a wave, but, shortly afterward, the plane’s left engine flamed out due to fuel exhaustion, causing it to descend.

Helios Boeing 737
The aircraft flew on autopilot until it ran out of fuel. Photo: Aero Icarus via Wikimedia Commons

The crash and the cause

While the flight attendant, Andreas Prodromou, was unable to regain control of the plane, he was heroically able to turn it away from Athens during the descent, preventing ground casualties. However, the fate of the aircraft’s 115 passengers and six crew was sealed, with all 121 occupants losing their lives when Helios Airways flight 522 crashed into mountainous terrain near Grammatiko, Greece, at 12:04.

But what was the root cause of this tragedy? It was found that an engineer had carried out a pressurization leak check on the aircraft earlier that day. However, this had involved the engineer setting the pressurization system to manual to avoid running the engines for the check. Upon completing the check, they forgot to reset the pressurization system to auto, which ultimately led to the loss of pressure that incapacitated the flight’s crew.

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The aircraft involved

The plane that crashed in this tragic accident was a Boeing 737-300 with the registration 5B-DBY. According to Planespotters.net, the aircraft had originally been delivered brand-new to German low-cost carrier Deutsche BA as D-ADBQ in January 1998.

Deutsche BA Boeing 737
The aircraft during its early years at Deutsche BA. Photo: wiltshirespotter via Wikimedia Commons

In 2002, the airline rebranded as simply DBA, and altered the plane’s configuration. It went from seating 122 passengers across two classes (40 business class and 82 economy class) to a 136-seat all-economy configuration.

Helios then began leasing the aircraft from Deutsche Structured Finance in April 2004. As such, the aircraft had only been with the airline for just over a year at the time of the crash. All in all, it had been in service for just over seven and a half years.

Helios Airways rebranded itself as Ajet and withdrew from scheduled operations in March 2006. Despite this, it eventually permanently suspended its remaining charter flights in November that year, and ceased to exist as an airline thereafter.

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