HELLENIC REPUBLIC
MINISTRY OF TRANSPORT & COMMUNICATIONS
AIR ACCIDENT INVESTIGATION
& AVIATION SAFETY BOARD
(AAIASB)
AIRCRAFT ACCIDENT REPORT
Accident of the a/c 5B-DBY of Helios Airways,
Flight HCY522 on August 14, 2005,
in the area of Grammatiko, Attikis,
33 km Northwest Of Athens International Airport
The accident investigation was carried out by the Accident Investigation and
Aviation Safety Board in accordance with:
HELLENIC REPUBLIC
MINISTRY OF TRANSPORT & COMMUNICATIONS
AIR ACCIDENT INVESTIGATION
& AVIATION SAFETY BOARD
(AAIASB)
AIRCRAFT ACCIDENT REPORT
HELIOS AIRWAYS FLIGHT HCY522
BOEING 737-31S
AT GRAMMATIKO, HELLAS
ON 14 AUGUST 2005
11 / 2006
ii
ACCIDENT INVESTIGATION REPORT
11 / 2006
Accident of the a/c 5B-DBY of Helios Airways,
Flight HCY522 on August 14, 2005,
in the area of Grammatiko, Attikis,
33 km Northwest Of Athens International Airport
The accident investigation was carried out by the Accident Investigation and
Aviation Safety Board in accordance with:
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2.2.6 Cruise
According to the statements submitted by the F-16 aircraft pilots that intercepted flight
HCY522 during its cruise at FL340, the Captain’s seat was vacant and the First Officer
was slumped over the aircraft controls. The Board believed that the Captain got out of
his seat possibly to check the circuit breakers. The flight crew oxygen masks were not
found in the wreckage but the First Officer was observed later (when the aircraft
descended) to not be wearing an oxygen mask. Therefore, the Board believed that the
flight crew failed to don the oxygen masks and make use of the flight deck oxygen
system. Thus, they succumbed to the effects of the hypoxic conditions. The Board
believed that the DNA finding that the flight deck observer oxygen masks contained
biological material that was consistent with the DNA of the First Officer was a result of
the severe impact forces.
The F-16 pilot stated that the flight deck and cabin windows were free of mist and frost.
He observed no detectable movement in the cabin by passengers or cabin crew. In fact,
he only reported seeing three passengers seated and wearing oxygen masks. The fact that
the passengers were seen wearing oxygen masks confirmed that the passenger oxygen
masks deployed from the Passenger Service Units, as they were designed to do when the
cabin altitude exceeded 14 000 ft, and as indicated by the FDR data. Furthermore, at
least some of the passengers were able to make use of these masks and the Board
concluded that at least some of the aircraft occupants were conscious during the climb to
cruising level.
It was not possible to determine whether any of the cabin crew members were conscious
during the climb, if they had been in a position to don oxygen masks as prescribed by the
procedures, and whether they demonstrated or instructed the passengers in the use of the
oxygen masks that had deployed. The amount of oxygen supplied by the passenger
oxygen system was designed to last 12 minutes. In order to retain consciousness after the
depletion of the oxygen from the passenger oxygen system, a person on board would
have had to make use of one of the additional means of oxygen supply available on board
the aircraft, i.e. the portable oxygen bottles. All four oxygen bottles were retrieved from
the wreckage; three bottles were found with their valves in the open position. The Board
concluded that these bottles were most likely used by someone on board the aircraft.
The observations by the F-16 pilot indicated that the aircraft never suffered any structural
or mechanical damage, either prior to or during the intercept. There was no evidence of
fire or smoke, or any fluids (hydraulic, fuel) from the aircraft – and hence no evidence of
loss of aircraft control. The aircraft continued to fly along the FMS-programmed route
via the EVENO and RODOS waypoints. During this time, the Athinai and Nicosia Air
Traffic Controllers repeatedly called flight HCY522 and exhausted all available means to
establish contact with the aircraft, but without success.
2.2.7 Descent
As the aircraft flew the KEA holding pattern at FL340 for the tenth time, at 08:48:05 h,
the F-16 pilot reported seeing a male person wearing a light blue shirt and a dark vest,
but not wearing an oxygen mask, enter the cockpit. This was confirmed by the CVR
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transcript. The sounds identified matched those of someone using the prescribed access
procedure to enter the cockpit, followed by sounds similar to the flight deck door
opening. The person proceeded to sit down in the Captain’s seat. At the same time, the
CVR transcript contained sounds that were identified as the inflation of an oxygen mask
harness. The Board believed that the F-16 pilot may not have been able to observe an
oxygen mask on the person’s face, because the portable oxygen bottle mask was clear in
According to the FDR data, at 08:49:50 h, the left engine of the accident aircraft flamed
out due to fuel starvation. This was confirmed by the statement of the F-16 pilot that
fumes were observed to come out of the left engine exhaust pipe, which was a normal
indication of engine flameout in flight. At this time, the aircraft exited the holding pattern
by starting a left descending turn and followed an uneven flight path of fluctuating
speeds and altitudes. The Board considered this evidence that the person in the Captain’s
seat was making an effort to control the aircraft. The F-16 pilot followed the accident
aircraft, continuing to attempt to attract the person’s attention but without success.
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 08:55:05
h 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.
During this time, the aircraft continued to descend towards the ground. Only once did
the person in the Captain’s seat appear to notice the F-16 and responded to his hand
signals, but there was no evidence that he attempted to follow the F-16 aircraft. The
Board believed that any person with the cabin attendant’s commercial pilot license
background, under the prevailing conditions of potential hypoxia and extreme stress,
would have been unable to gain control of a B737 with one engine stopped due to fuel
The second engine flamed out at 08:59:47 h, also due to fuel starvation. The aircraft
continued to descend without engine power and without electrical power except for the
instruments and systems which were powered by the aircraft battery. It was not likely,
nor reasonable to assume, that the APU would have been started for electrical power. It
impacted the ground at 09:03:32 h. According to the observations reported by the F-16
pilot and the way in which the aircraft impacted the ground, the person at the controls
appeared to have made an attempt to level the aircraft to alleviate the impact.
2.3 Cabin Crew Performance
2.3.1 Preflight, Taxi, and Takeoff
No data existed to establish the cabin crew preflight activities with any certainty. It was
assumed that before boarding the aircraft, the four cabin crew members participated in
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the required pre-flight safety briefing, and that the briefing was conducted together with
the flight crew. The length and content of this brief, the manner in which it was
administered, the time in which it was accomplished, the conditions under which it was
carried out, and whether everyone was present, were all factors that likely set the tone for
crew interactions during the accident flight. The Board could not determine whether the
Captain invited the cabin crew to feel free to communicate with the flight deck during the
flight if necessary (i.e. other than the required “safety checks” every 20 minutes) and if
so, under what circumstances he was open to calls from the cabin crew. During postaccident
interviews with other cabin crew members, the Board did not receive any reports
that the Captain set up any type of negative climate wherein he did not allow the cabin
crew to seek contact with the flight deck, if and when the need arose.
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http://www.aaiasb.gr/imagies/stories/documents/11_2006_EN.pdf
