The Helios Airways Flight 522 crashed in Greece, killing all 121 people on board, due to loss of cabin pressurization caused by a pressurization control valve being left in the "Manual" position after maintenance. As the plane ascended, the cabin failed to pressurize, knocking out the pilots and crew from hypoxia. A flight attendant attempted to regain control but crashed as the plane lost power from lack of fuel. The crash was the result of a maintenance error and crew's failure to recognize the pressurization problem.

1. CG render: 5B-DBY being met by two F-16s of the Hellenic Air Force at flight level 340
HELIOS AIRWAYS FLIGHT 522
1Helios 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.
BACKGROUND
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. Aside from the downed aircraft, the Helios fleet
consisted of two leased Boeing 737-800s and an Airbus A319-111 delivered May 14, 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.
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2. FLIGHT AND CRASH
Hans-Jürgen Merten, a former East German who was a 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. 32-year old Louisa Vouteri, a Greek national living in
Cyprus who served as a chief purser, replaced a sick colleague.
The flight, which left Larnaca, Cyprus at 09:07 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 pressurisation. 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 (4,300 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 is evidence 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 was evidence of
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 feet (100 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.
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3. 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 have been recovered. 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.
The cause of the crash (according to air crash investigations) was that the cabin
pressurisation 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.
INVESTIGATION
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 recognised the pressurisation system as the
source of the alarm and acted before their minds were too impaired by hypoxia.
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4. 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 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.
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 pressurisation 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. This model
of Boeing 737 has a warning horn which is used both to signal loss of pressurisation and
incorrect take-off configuration such as incorrect flap or trim setting. The crew may have
failed to realise that the warning horn indicated pressurisation failure and became
incapacitated while attempting to suppress a warning occurring in what seemed to them an
inappropriate phase of flight. 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
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5. 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 PRESSURISATION PROBLEMS
On 16 December 2004, during a flight from Warsaw, the ill-fated aircraft had suffered a
loss of cabin pressure and three passengers were rushed to hospital upon arrival in
Larnaca. 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 cold. Passengers also
reported problems with air conditioning on Helios flights.
During the two months before the crash, the aircraft's Environmental Control System
required repair five times. On the morning of the crash, after the aircraft arrived at Larnaca
on a flight from the United Kingdom, the cabin crew complained about an abnormal noise
coming from its rear door. Inspection by Helios engineers disclosed no problem and the
aircraft was allowed to take off without any repairs. In retrospect, the noise is consistent
with faulty sealing of the door that would allow gradual decompression of cabin air as the
aircraft gained altitude, resulting in initially subtle but increasing cognitive dysfunction
among the flight crew and delay in recognising the danger until it was too late.
The aircraft underwent maintenance on the night prior to the accident. The pressurisation
system was checked, but after completion of the tests the Pressurisation Mode Selector
(PMS) was reportedly left in the "Manual" position instead of the "Auto" mode. In manual
mode the crew had to manually open or close the outflow valves in order to control the
cabin pressure. The post-crash position of the outflow valves was one-third in the open
position, so that the cabin would not pressurise after takeoff. The PMS mode selection was
apparently not changed to automatic during the pre-departure checks by the crew.
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. It presented
evidence that a design failure of the Boeing 737 may have contributed to the accident.
Contrary to the concept of redundancy, all wiring related to the pressure system were in
one wiring loom to the outflow valve in the aft of the aircraft. A failure in this loom caused
a pressurisation incident with a Boeing 737-436 G-DOCE in May 2003. During this incident
the pressurisation control system presented wrong indications to the pilots and was finally
switched to manual position like found in the Helios 522 wreckage.
According to the Helios 522 final report, in a previous pressurisation incident with the
Helios accident aircraft: "The Captain stated that there might have been a problem with the
outflow valve." The Air Accident and Incident Investigation Board (AAIB) of Cyprus was not
able to reach a conclusive decision as to the causes of this previous incident, but indicated
as one of two possibilities: "An electrical malfunction caused the opening of the outflow
valve."
The official accident investigation board was informed by Discovery Channel of the
similarities with the G-DOCE incident. But in the final report neither the G-DOCE incident
nor any wiring loom issues were mentioned.
News media widely reported that shortly before the crash a passenger sent a text message
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6. 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. 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.
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.
SUBSEQUENT DEVELOPMENTS
• The flight Larnaca-Athens-Prague has been renumbered ZU604/5.
• The service between Larnaca and Prague is to be discontinued from 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 (www.flyhelios.com)" to "αjet
(www.ajet.com)".
• 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.
• Helios air crash families sue Boeing on 24 July 2007
DRAMATISATION
The Canadian television series Mayday, which examines aerial incidents, their causes and
results, created a documentary episode about the disaster.
REFERENCES
1. ^ 737 Production list
2. ^ a b "Ghost Plane." Mayday
3. ^ "Two trying to save jet ID'd ." News 24.
4.
5.
6. ^ "Pilot 'alive when plane crashed'", CNN, 2005-07-17
7.
8. ^ " Helios 737 crashed with no fuel and student pilot at the controls" Radar Vector,
2005-08- 21
9. ^ ASN Aircraft accident description Boeing 737-31S 5B-DBY – Grammatikos
10.^ AAIB Bulletin No: 6/2004
11.^ Phillips, Don (August 16, 2005). "Crash inquiry focuses on oxygen mask use",
International Herald Tribune. Retrieved on 2007-06-24.
12.^ "Hoax crash SMS: Man freed", News 24 (2005-08-17). Retrieved on 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 on 2007-07-26.
EXTERNAL LINKS
6

7. • Aircraft Incident Report of Helios Airways Flight HCY522 at Grammatiko, Greece on
14 August 2005 (published in English, released in November 2006)
• Complete report of the official investigation by the Greek air safety investigations
committee (published in Greek, released in October 2006).
• 360° Virtual tours & panoramic photos taken shortly after the crash
• Complete passenger list
• BBC article
• CNN article
• ERT article
• Sky News article
• Helios Airways
• Cyprus News Agency
• in.gr (Greek)
• Aviation Safety Network
• CBS News on Voice recorder
• The Age timeline
• ERT article in English: First official estimations
• Debate in comp.risks regarding possible design problems that contributed to the
crash
• Aviation Safety Network Accident Description
• Greek News Online article
• "Helios 737 crashed with no fuel", Flight International, 2005-08-24
• http://www.carsurvey.org/air/review_11283.html (Complaint about AC written one
week before the crash by a passenger).
ACCIDENT TIMELINE (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
0915 Alarm sounds at 14,000 feet (4,300 m)
0916 Last contact with Nicosia ATC; Altitude is 22,000 feet (6,700 m)
0924 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) alertedto possible renegade aircraft
1045 Scheduled arrival in Athens
1047 HAF reassured that the problemseemed to have been solved
1055 HAF ordered to intercept by Chief ofGeneral Staff, Admiral Panagiotis
Chinofotis
1105 Two F-16 fighters depart Nea Anchialos
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8. 1120 Located by F-16s over Aegean island of Kea
1125 Fighters see co-pilot slumped over,cabin oxygen deployed, no signs of
terrorism
1141 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
1200 Right (#2) engine stops operating
1205 Aircraft crashes in mountains near Grammatikos, Greece
SUMMARY
Date 14 August 2005
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
Survivors 0
Aircraft type Boeing 737-31S
Operator Helios Airways
Tail number 5B-DBY
Flight origin Larnaca International Airport
Stopover Athens International Airport
Destination Ruzyne` International Airport
8 8http://en.wikipedia.org/wiki/Helios_Airways_Flight_522
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