Helios Airways Flight 522
5B-DBY, the Boeing 737 involved in the accident
|Date||14 August 2005|
|Summary||Crashed following crew incapacitation due to loss of pressurization|
|Site||Grammatiko, Marathon, Greece |
|Aircraft type||Boeing 737-31S|
|IATA flight No.||ZU522|
|ICAO flight No.||HCY522|
|Call sign||HELIOS 522|
|Flight origin||Larnaca International Airport, Larnaca, Cyprus|
|Stopover||Athens International Airport, Greece|
|Destination||Prague Ruzyně Int'l Airport, Prague, Czech Republic|
Helios Airways Flight 522 was a scheduled passenger flight from Larnaca, Cyprus to Prague, Czech Republic with a stopover to Athens, Greece, that crashed on 14 August 2005, killing all 121 passengers and crew on board. A loss of cabin pressurization incapacitated the crew, leaving the aircraft flying on autopilot until it ran out of fuel and crashed near Grammatiko, Greece. It was the deadliest aviation accident in Greek history.
The aircraft involved in this accident, initially registered D-ADBQ, was first flown on 29 December 1997 and operated by DBA from 1998. It was leased by Helios Airways on 16 April 2004, when it was re-registered 5B-DBY with nickname Olympia. Besides the downed aircraft, the Helios fleet also included two leased Boeing 737-800s and an Airbus A319-100 which were delivered on 14 May 2005.
The plane had arrived at Larnaca International Airport at 01:25 local time on the day of the accident.:3 It was scheduled to leave Larnaca at 09:00 and fly to Prague Ruzyně International Airport with a stop off at Athens International Airport where it was due to arrive at 10:45.:4 The captain of the flight was Hans-Jürgen Merten, a 59-year-old German contract pilot hired by Helios for holiday flights, who had been flying for 35 years (previously for Interflug before 1990) and had accrued a total of 16,900 flight hours, including 5,500 hours on the Boeing 737. The first officer was Pampos Charalambous, a 51-year-old Cypriot pilot who had flown exclusively for Helios for the past five years, accruing 7,549 flight hours throughout his career, 3,991 of them on the Boeing 737. Louisa Vouteri, a 32-year-old Greek national living in Cyprus, had replaced a sick colleague as the chief flight attendant.
Flight and crash
|Date: 14 August 2005|
All times Eastern European Summer Time (EEST) (UTC + 3) in 24 h format
|09:07||Departs Larnaca International Airport|
|09:12||Cabin Altitude Warning sounds at |
12,040 feet (3,670 m)
|09:14||Pilots report air conditioning problem|
|09:20||Last contact with crew;|
Altitude is 28,900 feet (8,809 m)
|09:23||Now at 34,000 feet (10,400 m);|
Probably on autopilot
|09:37||Enters Athens flight information region;|
Nicosia ATC informs Athens ATC that
radio contact has been lost.:17 Aircraft begins circling Athens on autopilot
|10:12–10:50||No response to radio calls from Athens ATC|
|10:45||Scheduled arrival in Athens|
|10:54||Athens Joint Rescue Coordination Centre|
alerted to possible renegade aircraft:18
|11:05||Two F-16 fighters depart Nea Anchialos|
|11:24||Located by F-16s over Aegean island of Kea|
|11:32||Fighters see co-pilot slumped over, |
cabin oxygen deployed, no signs of terrorism
|11:49||Fighters see an individual in the cockpit,|
apparently trying to regain control of aircraft
|11:50||Left (#1) engine stops operating,|
presumably due to fuel depletion
|11:54||CVR records a total of five mayday messages|
|12:00||Right (#2) engine stops operating|
|12:04||Aircraft crashes in mountains|
near Grammatiko, Greece
When the aircraft arrived from London earlier that morning, the previous flight crew had reported a frozen door seal and abnormal noises coming from the right aft service door. They requested a full inspection of the door.:33–34 The inspection was carried out by a ground engineer who then performed a pressurization leak check. In order to carry out this check without requiring the aircraft's engines, the pressurisation system was set to "manual". However, the engineer failed to reset it to "auto" on completion of the test.:171
After the aircraft was returned into service, the flight crew overlooked the pressurisation system state on three occasions: during the pre-flight procedure, the after-start check, and the after take-off check. During these checks, no one in the flight crew noticed the incorrect setting.:171 The aircraft took off at 9:07:16 with the pressurisation system still set to "manual", and the aft outflow valve partially open.:78
As the aircraft climbed, the pressure inside the cabin gradually decreased. As it passed through an altitude of 12,040 feet (3,670 m), the cabin altitude warning horn sounded.:16 The warning should have prompted the crew to stop climbing,:133 but it was misidentified by the crew as a take-off configuration warning, which signals that the aircraft is not ready for take-off, and can only sound on the ground. The alert sound is identical for both warnings.:133
In the next few minutes, several warning lights on the overhead panel in the cockpit illuminated. One or both of the equipment cooling warning lights came on to indicate low airflow through the cooling fans (a result of the decreased air density), accompanied by the master caution light. The passenger oxygen light illuminated when, at an altitude of approximately 18,000 feet (5,500 m), the oxygen masks in the passenger cabin automatically deployed.:17,134
Shortly after the cabin altitude warning sounded, the captain radioed the Helios operations centre and reported "the take-off configuration warning on" and "cooling equipment normal and alternate off line".:16 He then spoke to the ground engineer and repeatedly stated that the "cooling ventilation fan lights were off".:16 The engineer (the one who had conducted the pressurization leak check) asked "Can you confirm that the pressurization panel is set to AUTO?" However, the captain, already experiencing the onset of hypoxia's initial symptoms,:135 disregarded the question and instead asked in reply, "Where are my equipment cooling circuit breakers?".:17 This was the last communication with the aircraft.:137
The aircraft continued to climb until it leveled off at FL340, approximately 34,000 feet (10,000 m).:17 Between 09:30 and 09:40, Nicosia ATC repeatedly attempted to contact the aircraft, without success.:17 At 09:37, the aircraft passed from Cyprus flight information region (FIR) into Athens FIR, without making contact with Athens ATC.:17 Nineteen attempts to contact the aircraft between 10:12 and 10:50 also met with no response,:17–18 and at 10:40 the aircraft entered the holding pattern for Athens Airport, at the KEA VHF omnidirectional range, still at FL340.:18 It remained in the holding pattern, under control of the auto-pilot, for the next 70 minutes.:18
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 intercepted the passenger jet at 11:24 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.:18
At 11:49, flight attendant Andreas Prodromou entered the cockpit and sat down in the captain's seat, having remained conscious by using a portable oxygen supply.:139 Prodromou held a UK Commercial Pilot Licence,:27 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.:139 Prodromou waved at the F-16s very briefly, but almost as soon as he entered the cockpit, the left engine flamed out due to fuel exhaustion:19 and the plane left the holding pattern and started to descend.:19 Ten minutes after the loss of power from the left engine, the right engine also flamed out,:19 and just before 12:04 the aircraft crashed into hills near Grammatiko, 40 km (25 mi; 22 nmi) from Athens, killing all 121 passengers and crew on board.:19
The aircraft was carrying 115 passengers and a crew of six. The passengers included 67 due to disembark at Athens, with the remainder continuing to Prague. The bodies of 118 people were recovered. The passenger list included 93 adults and 22 children. The passengers comprised 103 Cypriot nationals and 12 Greek nationals.
The flight data recorder and cockpit voice recorder were sent to Paris for analysis.:51–52 The CVR recording enabled investigators to identify Prodromou as the flight attendant who entered the cockpit in order to try to save the plane. He called "Mayday" five times but, because the radio was still tuned to Larnaca, not Athens, he was not heard by ATC. His voice was recognized by colleagues who listened to the CVR recording.:139
Many of the bodies recovered were burned beyond recognition by the post-impact fire.:57 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.:69
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 12 minutes,:45 normally sufficient for an emergency descent to 10,000 feet (3,000 m), where atmospheric pressure is sufficient for humans to sustain consciousness without supplemental oxygen. Cabin crew have access to portable oxygen sets with considerably longer duration.:44
The Hellenic Air Accident Investigation and Aviation Safety Board (AAIASB) listed the direct causal chain of events that led to the accident as:
- non-recognition by the pilots that the pressurisation system was set to "manual",
- non-identification by the crew of the true nature of the problem,
- incapacitation of the crew due to hypoxia,
- eventual fuel starvation,
- impact with the ground.:171
Previous pressurization problems
On 16 December 2004, during an earlier flight from Warsaw, the same aircraft experienced a rapid loss of cabin pressure and the crew made an 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.:113
The mother of the first officer killed in this crash claimed that her son had repeatedly complained to Helios about the aircraft getting cold. Passengers also reported problems with air conditioning on Helios flights. During the 10 weeks before the crash, the aircraft's environmental control system was repaired or inspected seven times.:115
A 2003 flight of a Boeing 737 between Marseilles and London Gatwick showed that a cabin-wide pressurization fault can be recognized by the flight crew. A problem was first noticed when the crew began to feel some discomfort in their ears. This was shortly followed by the cabin altitude warning horn which indicated that the cabin altitude had exceeded 10,000 feet (3,000 m) and this was seen to continue to climb on the cockpit gauge. At the same time, the primary AUTO mode of the pressure control failed, shortly followed by the secondary STBY mode. The crew selected the first manual pressure control mode, but were unable to control the cabin altitude. An emergency descent and subsequent diversion to Lyon was carried out. The failure of the pressurization control system was traced to burnt electrical wiring in the area aft of the aft cargo hold. The wiring loom had been damaged by abrasion with either a p-clip or "zip" strap that, over time, exposed the conductors, leading to short circuits and subsequent burning of the wires. There was no other damage. The wiring for all the modes of operation of the rear outflow valve, in addition to other services, run through this loom.
The company announced successful safety checks on their Boeing fleet on 29 August 2005 and put them back into service. It later changed its name from Helios Airways to αjet. However, when authorities in Cyprus detained the company's aircraft and froze the company's bank accounts about a year later, the airline announced that it would stop operating on 31 October 2006.
In March 2011, the Federal Aviation Administration in the United States released an Airworthiness Directive requiring all Boeing 737 aircraft from −100 to −500 models to be fitted with two additional cockpit warning lights. These would indicate problems with take-off configuration or pressurization. Aircraft on the United States civil register were required to have the additional lights by 14 March 2014.
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 sued for 76 million euros in compensation from Boeing. The case against Boeing was settled out of court.
In early 2008, an Athens prosecutor charged six former employees with manslaughter over the incident. Reports at the time said the suspects were two Britons, one Bulgarian national, and three Cypriots.
On 23 December 2008, Helios Airways and four of its officials were charged in Cyprus with 119 counts of manslaughter and of causing death by recklessness and negligence. The four officials were former chief pilot Ianko Stoimenov, chairman of the board Andreas Drakos, chief executive officer Demetris Pantazis, and operations manager Giorgos Kikidis. The trial began in November 2009; the state prosecutors finished presenting their case in June 2011. The case was dismissed, and the defendants acquitted, on 21 December 2011. The panel of judges hearing the case ruled that there was no "causal association between the defendants and the negligence they were charged with for the fatal accident". An appeal was filed by the Cypriot Attorney-general, and in December 2012 the Supreme Court set aside the acquittal and ordered a new trial. Two months later, the retrial was dropped under double jeopardy rules, as the charges had already been heard in Athens.
In December 2011, shortly after the end of the case in Cyprus, a new trial began in a Greek magistrate's court in which chief executive officer Demetris Pantazis, flight operations manager Giorgos Kikkides, former chief pilot Ianko Stoimenov and chief engineer Alan Irwin were charged with manslaughter. All except Irwin had been previously charged and acquitted by the Cypriot authorities. In April 2012 all were found guilty and sentenced to 10 years imprisonment and remained free on bail pending an appeal.
By 2013 Alan Irwin was successful in his appeal. All the other defendants lost their appeals.  Their sentence of 10 years was ordered to stand but the defendants were given the option to buy out their sentence for around €79,000 each. Stoimenov was spared jail after the intervention of the Bulgarian government who felt he was innocent of the charges.
Greek investigators blamed the crash of the Helios Airways flight outside Athens on human error after the aircraft failed to pressurize after taking off from Larnaca Airport. Prosecutors in both countries blamed airline officials for cutting corners on safety operations while also saying that they failed to act on advice that the pilots did not meet the necessary aviation standards.
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 ignoring airlines' loose enforcement of regulations, and that in general the department cut corners when it came to flight safety.[needs update]
In 2020 a Guardian investigation uncovered a FAA assessment of the Boeing 737 in response to the Helios crash. The report "acknowledged that the pressurisation failure and the warning system were “likely a significant contributing factor”". Since the crash Boeing has updated affected 737 models with two additional lights to warn of pressurisation problems.
In popular culture
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The F-16 pilots reported seeing the co-pilot slumped in his seat and the captain's seat empty.
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- AAIASB final report, section 1.11.2 "Flight Data Recorder (FDR)", p. 40 (PDF page 52 of 198): "The FDR was found near the right aft service door and was recovered from the accident site on 14 August 2005, the day of the accident (Photo – FDR). It was taken to the readout facilities of BEA and the read out began on 17 August 2005"
- AAIASB final report, section 2.2.7 "Descent", p. 127 (PDF page 139 of 198): "During the initial descent, at 08:54:18 h, the CVR record contained a MAYDAY call from the person in the Captain’s seat. The call was not transmitted over the VHF radio; it was only picked up the CVR microphone. The second MAYDAY call was at 08:55:05h followed by a third one a few seconds later. Based on the fact that there was only one male cabin attendant on board the accident aircraft, that the voice on the CVR was identified by colleagues to match that of the male cabin attendant, and that the person that entered the cockpit was wearing a Helios cabin attendant uniform, the Board concluded that the person that entered the cockpit and made efforts to control the aircraft was the male cabin crew member."
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Attorney General Petros Clerides told The Associated Press that he dropped the charges because European Union laws stipulate that defendants tried and convicted in one EU country can't be tried for the same crime in another EU country.
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