The aircraft, operating as flight ET409, departed Beirut's
Rafic Hariri airport at 00:41 UTC on 25 January 2010 but crashed into the
Mediterranean Sea around 5nm south-west of the airport after a flight lasting
just 4min 15s, killing all 90 people on board.
In the conclusions, the report, produced by the Lebanese
Civil Aviation Authority, said that the probable causes of the accident were
the "flight crew's mismanagement of the aircraft's speed, altitude,
headings and attitude through inconsistent flight control inputs resulting in
loss of control".
The night departure and course changes to avoid weather,
combined with the captain's relative inexperience as pilot-in-command on the
type, may have led to the captain "reaching a situation of loss of
situational awareness similar to a subtle incapacitation and the [first
officer's] failure to recognise it or to intervene accordingly".
During the brief flight, the flight data recorder and
cockpit voice recorder captured two "prolonged" stick shaker alarms
of 27s and 26s as the aircraft entered stall situations, 11 aural "bank
angle" warnings and a final overspeed warning towards the end of the 737's
descent.
The aircraft had a maximum angle of attack of 32e_SDgr,
maximum bank angle of 118e_SDgr left and maximum recorded speed of 407.5kt,
said the report.
No mechanical defects were found on the 2002 airframe
(ET-ANB) and the two CFM International CFM56-7BE engines performed normally, it
said.
It suggests that the pairing of the pilots may have been a
contributory factor. The captain had only secured his release to fly solo on
the type 51 days prior to the accident, in which time he had accumulated 188h.
While the inquiry report said he had over 3,700h as
pilot-in-command, it said nearly 2,500h were on "different light and spray
aircraft".
The first officer, however, had a total of 673h, of which
350h were as first officer on 737-700 and -800s.
Although the pairing was within the airline's
recommendation, which states that "a captain who has less than 300 hours
and first officer who has less than 100 hours on type should not be scheduled
together", the report added: "That level of experience, although
within the required approved standard, did not constitute a comfortable margin
that would allow the crew to have enough confidence in the operation of the
aircraft under demanding conditions, especially when we consider that the
captain's experience on the 737-700/800 was acquired in the 51 days preceding
the accident."
The first officer also demonstrated a lack of assertiveness to intervene when faced with the captain's "strange flying behaviour", it said.
Ethiopian Airlines should revise its cockpit relationship
management policies, it said, to stress the leadership and assertiveness
required of a first officer. Crew pairings should also be reconsidered, it
added.
However, Ethiopian Airlines has angrily dismissed the report
as "biased, lacking evidence, incomplete and [failing to] present the full
account of the accident". It remains convinced that the aircraft disintegrated
in mid-air due to an explosion.
In a statement, Captain Desta Zeru, vice-president flight
operations at Ethiopian Airlines, said the flight data and cockpit voice
recorders show that the pilot was making "appropriate inputs in an effort
to control the aircraft".
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