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Helios Airways Flight 522

Artist's depiction of 5B-DBY being met by two F-16s of the Hellenic Air Force at 3400 ft
Accident summary
Date 14 August 2005 (2005-08-14)
Type Pilot incapacitation due to
hypoxia brought about by
depressurization, leading to
fuel starvation
Site Marathon, Greece
Passengers 115
Crew 6
Injuries 0
Fatalities 121 (all)
Survivors 0
Aircraft type Boeing 737-31S
Operator Helios Airways
Tail number 5B-DBY
Flight origin Larnaca International Airport
Stopover Athens International Airport
Destination Ruzyně International Airport

Helios Airways Flight 522 (HCY 522 or ZU522) was a Helios Airways Boeing 737-31S flight that crashed on 14 August 2005 at 12:04 EEST into a mountain north of Marathon and Varnavas, Greece. Rescue teams located wreckage near the community of Grammatiko 40 km (25 miles) from Athens. All 121 on board were killed.



The aircraft involved in this incident was first flown on 29 December 1997 and had been operated by DBA until it was leased by Helios Airways on 16 April 2004 and nicknamed Olympia, with registration 5B-DBY.[1] Aside from the downed aircraft, the Helios fleet consisted of two leased Boeing 737-800s and an Airbus A319-111 delivered on 14 May 2005.

With 121 dead, this was 2005's deadliest aircraft crash to that date (it was exceeded two days later by the West Caribbean Airways Flight 708 crash, which killed 160) and was the second accident of the year that caused more than 100 fatalities, the first being Kam Air Flight 904 with 104 deaths. It is the 69th crash of a Boeing 737 (the most numerous passenger jet aircraft in the world) since it was brought into service in 1968.

Flight and crash

Path of Helios Airways Flight 522
Date: 14 August 2005
All times EEST (UTC + 3h), PM in bold
Time Event
0900 Scheduled departure
0907 Departs Larnaca International Airport
0911 Pilots report air conditioning problem
0912 Cabin Altitude Warning sounds at 12,040 feet (3,670 m)
0920 Last contact with Nicosia ATC;
Altitude is 28,900 feet (8,809 m)
0923 Now at 34,000 feet (10,400 m);
Probably on autopilot
0937 Enters Athens Flight Information Region
1007 No response to radio calls from Athens ATC
1020 Athens ATC calls Larnaca ATC;
Gets report of air conditioning problem
1024 Hellenic Air Force (HAF) alerted
to possible renegade aircraft
1045 Scheduled arrival in Athens
1047 HAF reassured that the problem
seemed to have been solved
1055 HAF ordered to intercept by Chief of
General Staff, Admiral Panagiotis Chinofotis
1105 Two F-16 fighters depart Nea Anchialos
1124 Located by F-16s over Aegean island of Kea
1132 Fighters see co-pilot slumped over,
cabin oxygen deployed, no signs of terrorism
1149 Fighters see an individual in the cockpit,
apparently trying to regain control of aircraft
1150 Left (#1) engine stops operating,
presumably due to fuel starvation
1154 CVR records two MAYDAY messages
1200 Right (#2) engine stops operating
1204 Aircraft crashes in mountains
near Grammatikos, Greece

Hans-Jürgen Merten, who was a German contract pilot hired by Helios for the holiday flights, served as the captain. Pampos Charalambous, a Cypriot who flew for Helios, served as the first officer.[2] 32-year old Louisa Vouteri, a Greek national living in Cyprus who served as a chief purser, replaced a sick colleague.[3]

The flight, which left Larnaca, Cyprus at 06:07 local time, was en route to Athens, and was scheduled to continue to Prague. Before take-off the crew failed to set the pressurisation system to "Auto," which is contrary to standard Boeing procedures. Minutes after take-off the cabin altitude horn activated as a result of pressurization. It was, however, misidentified by the crew as a take-off configuration warning, which signals the plane is not ready for take-off, and can only sound on the ground. The horn can be silenced by the crew with a switch on the overhead panel.

Above 14,000 ft (4,267 m) cabin altitude, the oxygen masks in the cabin automatically deployed. An Oxy ON warning light on the overhead panel in the cabin illuminates when this happens. At this point, the crew contacted the ground engineers. Minutes later a master caution warning light activated, indicating an abnormal situation in a system. This was misinterpreted by the crew that systems were overheating.

At some point later the captain radioed the engineer on the ground to say that the ventilation fan lights were off. This suggests that the captain was suffering from hypoxia, as the 737-300 has no such lights. The engineer asked the captain to repeat. The captain then said that the equipment cooling lights were off, which again suggested confusion. The engineer said, "this is normal, please confirm the problem." The engineer then asked, "Can you confirm that the pressurization system is set to AUTO?" The captain, however, disregarded the question and instead asked in reply, "Where are my equipment cooling circuit breakers?" The engineer then asked whether the crew could see the circuit breakers, but received no response.

After the flight failed to contact air traffic control upon entering Greek air space, two F-16 fighter aircraft from the Hellenic Air Force 111th Combat Wing were scrambled from Nea Anchialos Air Base to establish visual contact. They noted that the aircraft appeared to be on autopilot. In accordance with the rules for handling "renegade" aircraft incidents (where the aircraft is not under pilot control), one fighter approached to within 300 ft (91 m), and saw the first officer was slumped motionless at the controls. The pilot could also see that the captain was not upright in the cockpit and that oxygen masks were seen dangling in the passenger cabin.

Crash area of the flight in red

Later, the F-16 pilots saw the flight attendant Andreas Prodromou enter the cockpit and sit at the controls, seemingly trying to regain control of the aircraft. He eventually noticed the F-16, and signaled him. The pilot pointed forward as if to ask, "Can you carry on flying?" Prodromou responded by shaking his head and pointing downward. The cockpit voice recorder recorded him calling "mayday" multiple times. Within minutes, due to lack of fuel, the engines failed in quick succession and the aircraft began to descend. Prodromou grabbed the yoke and attempted to steer, but the plane continued, hit the ground and exploded. At the time of impact, the passengers and crew were likely unconscious but breathing. None survived.

The aircraft was carrying 115 passengers and a crew of 6. The passengers included 67 due to disembark at Athens, with the remainder continuing to Prague. The bodies of 118 individuals were recovered.[4] The passenger list included 93 adults and 22 people under the age of 18. Cypriot nationals comprised 103 of the passengers and Greek nationals comprised the remaining 12.[5]

The cause of the crash (according to air crash investigations) was that the cabin pressurization control valve was set to manual and was not switched back to auto after post-maintenance pressurisation testing was completed. As a result, the cabin never pressurised during the ascent to 35,000 feet (11,000 m). The flight attendant seen in the cockpit managed to stay conscious by using the spare oxygen bottles provided in the passenger cabin for crew use.


Suspicions that the aircraft had been hijacked were ruled out by Greece's foreign ministry. Initial claims that the aircraft was shot down by the fighter jets have been refuted by eyewitnesses and the government.

Loss of cabin pressure—which, without prompt alleviation, would cause pilot unconsciousness—is the leading theory explaining the accident. This would account for the release of oxygen masks in the passenger cabin. Weighing against this is the fact that the pilots should have been able to don their own fast-acting masks and make an emergency descent to a safe altitude provided that they recognized the pressurization system as the source of the alarm and acted before their minds were too impaired by hypoxia.

The flight data recorder and cockpit voice recorder were sent to Paris for analysis. Authorities served a search warrant on Helios Airways' headquarters in Larnaca, Cyprus, and seized "documents or any other evidence which might be useful in the investigation of the possibility of criminal offences."

Most of the bodies recovered were burned beyond visual identification by the fierce fires that raged for hours in the dry brush and grass covering the crash site. However, it was determined that a body found in the cockpit area was that of a male flight attendant[6] and DNA testing revealed that the blood on the aircraft controls was that of flight attendant Andreas Prodromou, a pilot-in-training with approximately 260–270 hours of training completed. Autopsies on the crash victims showed that all were alive at the time of impact, but it could not be determined whether they were conscious as well. Prodromou was not originally scheduled to be on the flight; he joined the crew so he could spend time with his girlfriend, a fellow Helios flight attendant.[2]


Decompression hypothesis

Helios Airways aircraft 5B-DBY at London Luton Airport in 2004

The preliminary investigation reports state that the maintenance performed on the aircraft had left the pressurization control on a 'manual' setting, in which the aircraft would not pressurise automatically on ascending; the pre-takeoff check had not disclosed nor corrected this. As the aircraft passed 10,000 feet (3,000 m), the cabin altitude alert horn sounded. The horn also sounds if the aircraft is not properly set for take off, e.g. flaps not set, and thus it was assumed to be a false warning. The aircrew found a lack of a common language and inadequate English a hindrance in solving the problem. The aircrew called maintenance to ask how to disable the horn, and were told where to find the circuit-breaker. The pilot left his seat to see to the circuit breaker and both aircrew lost consciousness shortly afterwards.

The leading explanation for the accident is that the cabin pressurisation did not operate and this condition was not recognised by the crew before they became disabled. Decompression would have been fairly gradual as the aircraft climbed under the control of the flight management system. The pressurisation failure warning on this model should operate when the effective altitude of the cabin air reaches 10,000 ft (3,000 m) at which altitude a fit person will have full mental capacity.

The emergency oxygen supply in the passenger cabin of this model of Boeing 737 is provided by chemical generators that provide enough oxygen, through breathing masks, to sustain consciousness for about 15 minutes, normally sufficient for an emergency descent to 10,000 feet (3,000 m), where atmospheric pressure is sufficient to sustain life without supplemental oxygen. Cabin crew have access to portable oxygen sets with considerably longer duration. Emergency oxygen for the flight crew comes from a dedicated tank.

Previous pressurization problems

On 16 December 2004, during an earlier flight from Warsaw, the accident aircraft experienced a rapid loss of cabin pressure, and the crew made a successful emergency descent. The cabin crew reported to the captain that there had been a bang from the aft service door, and that there was a hand-sized hole in the door's seal. The Air Accident and Incident Investigation Board (AAIIB) of Cyprus could not conclusively determine the causes of the incident, but indicated two possibilities: an electrical malfunction causing the opening of the outflow valve, or the inadvertent opening of the aft service door.[7]

The mother of the first officer killed in the crash of Flight 522 claimed that her son had repeatedly complained to Helios about the aircraft getting old. Passengers also reported problems with air conditioning on Helios flights.[8] During the two months before the crash, the aircraft's Environmental Control System required repair five times.[9]

On the morning of the crash, after the aircraft arrived at Larnaca on a flight from the United Kingdom, the cabin crew reported an abnormal noise coming from the right aft service door during the flight. Helios engineers performed a visual inspection of the door and a pressurization leak check, and reported no defects, leaks, or abnormal noises.

Private investigation

One year after the accident, the Discovery Channel aired a documentary detailing a private investigation, made in cooperation with Advanced Aviation Technology Ltd., arguing that a design failure of the Boeing 737 may have contributed to the accident.

All wiring for the pressurization system was in one wiring loom to the outflow valve in the aft of the Boeing 737. During a Boeing 737-436 G-DOCE flight in May 2003, a failure in this loom opened the outflow valve, which caused the cabin to depressurize. The same wiring failure probably caused erroneous indications to the crew that the standby pressurization system had failed and that the outflow valve was fully closed and unresponsive to pilot input. After seeing indication of the standby pressurization failure, the crew switched the pressurization control to manual mode and made an emergency descent.[10]

Discovery Channel reported its findings on the G-DOCE incident to the Hellenic Republic's Air Accident Investigation & Aviation Safety Board.

The Board reported no evidence of wiring failure in Flight 522, and did not mention the G-DOCE incident. Because all available flight data showed the pressurization control in manual mode and the outflow valve open at a constant angle, and because there was no evidence the flight crew ever changed the pressurization mode, the Board concluded that the pressurization system had been set to manual for the entire flight, which caused the pressurization failure.[7]


News media widely reported that shortly before the crash a passenger sent a text message indicating that one of the flight crew had become blue in the face, or roughly translated as "The pilot is dead. Farewell, my cousin, here we're frozen." Police later arrested Nektarios-Sotirios Voutas, who admitted that he had made up the story and given several interviews in order to get attention.[11] Voutas was tried by a court of first instance on 17 August 2005 and received a suspended 6-month imprisonment sentence under a 42-month probation term.[12]

Another hoax involved photographs allegedly showing the aircraft being chased by Greek fighter jets. The photos were actually of a Helios 737-800 (rather than the crashed 737-300) with the registration altered and the fighter jets added.[13]

Subsequent developments

  • The flight Larnaca-Athens-Prague has been renumbered ZU604/5.
  • The service between Larnaca and Prague was discontinued on 26 August 2005.
  • The company announced successful safety checks on their Boeing fleet 29 August 2005 and put them back into service.
  • The company renamed itself from "Helios Airways (" to "αjet (".
  • The Government of the Republic of Cyprus detained Ajet’s aircraft and froze the company’s bank accounts. Ajet no longer operates flights as of 11 June 2006.

Lawsuits and criminal proceedings

Families of the dead filed a lawsuit against Boeing on 24 July 2007. Their lawyer, Constantinos Droungas, said "Boeing put the same alarm in place for two different types of dysfunction. One was a minor fault, but the other - the loss of oxygen in the cockpit - is extremely important". He also said that similar problems had been encountered before on Boeings in Ireland and Norway. The families are claiming 76 million euros in compensation from Boeing.[14]

In early 2008, an Athens prosecutor charged six people with manslaughter. Reports at the time said the suspects were two Britons, one Bulgarian national and three Cypriots.[15]

On 23 December 2008, five Helios Airways officials were charged with manslaughter and of causing death by recklessness/negligence. Cyprus' Deputy Attorney General Akis Papasavvas would not identify those charged, but said the suspects had until 26 February (3pm) 2009 to appear before court and answer the charges – effectively to enter a plea.[16][17][18][19]

Relatives of the dead filed a class action suit against the Cypriot Government – specifically the Department of Civil Aviation – for negligence that led to the air disaster. They claim that the DCA was turning a blind eye to airlines’ loose enforcement of regulations, and that in general the department cut corners when it came to flight safety.[15]


The Canadian television series Mayday, which examines aerial incidents, their causes and results, created a documentary episode, titled Ghost Plane, about the disaster. Discovery Channel UK also produced a 45-minute documentary about the accident, titled Aircrash Unsolved: The Mystery of Flight 522.


  1. ^ 737 Production list
  2. ^ a b "Ghost Plane." Mayday
  3. ^ "Two trying to save jet ID'd ." News 24.
  4. ^ Greek "Αεροπορική τραγωδία" Flash.GR
  5. ^ Greek Ο κατάλογος των θυμάτων ERT
  6. ^ "Pilot 'alive when plane crashed'", CNN, 2005-07-17
  7. ^ a b$file/FINAL%20REPORT%205B-DBY.pdf
  8. ^ news - Βεβαρημένο το παρελθόν του αεροσκάφους που συνετρίβη, σύμφωνα με μάρτυρες
  9. ^ " Helios 737 crashed with no fuel and student pilot at the controls" Radar Vector, 2005-08-21
  10. ^
  11. ^ Phillips, Don (16 August 2005). "Crash inquiry focuses on oxygen mask use". International Herald Tribune. Retrieved 2007-06-24.  
  12. ^ "Hoax crash SMS: Man freed". News 24. 2005-08-17.,,2-10-1462_1755572,00.html. Retrieved 2007-06-24.  
  13. ^ "Fake Helios pictures identified", Flight International, 2005-08-17
  14. ^ "Cyprus air crash victims' families make 76 mln eur legal claim against Boeing". Forbes (AFX News). 25 July 2007. Retrieved 2007-07-26.  
  15. ^ a b
  16. ^
  17. ^
  18. ^ [1]
  19. ^

External links

Coordinates: 38°13.894′N 23°58.214′E / 38.231567°N 23.970233°E / 38.231567; 23.970233


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