have concluded that an incorrectly-set cabin pressurisation switch, and the
failure to recognise warnings of oxygen depletion, led to the fatal loss of a
Helios Airways Boeing 737-300 aircraft in Greece
final report into the accident, released today, shows that the crew did not
realise that the pressurisation selector was in the ‘manual’ position while
carrying out pre-flight procedures or while reading checklists – it says the
switch could have been left in the ‘manual’ position, rather than returned to
the ‘automatic’ position, during non-scheduled maintenance.
flight ZU522 departed the Cypriot city of Larnaca
for Prague on 14 August
last year with 115 passengers and six crew members. But the aircraft failed to
pressurise as it climbed to cruise altitude, incapacitating the crew and
leading to the 737’s crashing as the engines ran out of fuel.
from the immediate contributory factors the final report identifies four latent
causes of the accident, including deficiencies in the operator’s organisation,
safety culture and quality management.
cites “inadequate application” of crew resource management principles. The
investigators also list “ineffectiveness of measures” taken by Boeing in response to previous
pressurisation incidents on the aircraft type.
the report also points to a creeping, underlying failure of safety oversight by
the Helios 737 was climbing through 16,000ft – having been cleared to flight
level 340 – the captain contacted the company’s operations centre to report a
take-off configuration warning and a problem with the equipment cooling system.
oxygen masks deployed in the cabin as the aircraft climbed through 18,200ft.
But the inquiry report says that the flight crew failed to identify
cabin-altitude warnings and did not notice indications that mask deployment had
the following eight minutes, several communications between the captain and the
operations centre took place regarding the original problems relayed to the
operations centre. But these ended as the 737 climbed through 28,900ft – after
which there was no response to radio calls, the crew having succumbed to
hypoxia as the aircraft failed to pressurise.
state that lack of cabin crew procedures to address the loss of pressurisation,
and continuation of the climb despite the deployment of masks, contributed to
737 automatically followed its pre-programmed course, levelling at FL340 and overflying the Kea VOR, southeast
of Athens, at 10:21 –
74min after take-off.
passed Athens International
and subsequently entered the holding pattern for the Kea VOR, where it
Martin F-16 fighters from the Hellenic Air Force intercepted the jet at 11:24, 46min after it first entered
the hold, while the 737 was performing its sixth cycle in the pattern.
of the F-16 pilots reported that the captain’s seat was not occupied and that a
person in the first officer’s seat was slumped over the instruments. The pilot
also reported seeing deployed oxygen masks in the cabin and three motionless
passengers, seated in the cabin, wearing them.
minutes after interception, with no radio response from the 737, the F-16 pilot
saw a person without a mask enter the cockpit and sit in the captain’s seat.
The F-16 pilot was unable to attract the individual’s attention.
minute later, fuel exhaustion caused the left CFM International CFM56 engine to
stop operating, and the aircraft began descending. Two unsuccessful ‘Mayday’
calls, made four minutes after the flame-out, were later discovered on the
the aircraft descended past 7,100ft, the right-hand engine succumbed to fuel
depletion, having continued operating for ten minutes longer than the other powerplant. Three minutes later,
at 12:03, the 737 struck terrain about 33km northwest of Athens Airport.
None of those on board survived.
Airways rebranded itself
under a new name, A Jet, earlier this year.
interim safety recommendations were made during the course of the
investigation, including five to the US National Transportation Safety Board
and Boeing. The final report says that four of these have already resulted in
US FAA, it adds, issued an airworthiness directive informing flight crews about
improved procedures for pre-flight set-up of the cabin pressurisation system
and better procedures for responding to cabin-altitude warning horns.
the final report adds another 11 safety recommendations directed at the Cypriot
Government, ICAO, the European Aviation Safety Agency and the Joint Aviation
Authorities. These centre on correcting safety deficiencies relating to
maintenance procedures, pilot training, organisational issues of the operator,
and overall safety oversight.