Air Algerie - Swiftair

Swiftair MD-83 lost speed before rapid spiral descent

By: DAVID KAMINSKI-MORROW

LONDON

Source: 

14:32 7 Aug 2014

French investigators have determined that a Swiftair Boeing 
MD-83 lost over Mali entered a rapid spiral descent from which 
it failed to recover.

But the inquiry is being hampered by a lack of usable information
on the cockpit-voice recorder.

The aircraft, operating an Air Algerie service from Ouagadougou
on 24 July, had deviated to the left of its flightpath to skirt
around a storm system covering the northern tip of Burkina Faso.

French investigation authority BEA describes the course
change as “moderate”, typical of an adjustment to avoid such
weather. During this deviation, some 22min after take-off, the
aircraft levelled off at its cruising altitude of 31,000ft at about
01:37UTC.

But just 2min later, as it neared the northern edge of the
storm, the aircraft – which had been travelling at 273kt – began
to lose speed.

Its speed deteriorated to 160kt and the aircraft started
descending, says BEA, before the MD-83 suddenly began
turning left, losing height rapidly. The inquiry says it experienced
“large changes” in pitch and bank.

The aircraft entered a spiral descent, making about one and a
half rotations. Its flight-data recorder gave a final height
reading of 1,600ft and a speed of around 380kt, shortly after
01:47UTC.

BEA chief Remi Jouty says about 1s elapsed between this last
recorded point and the impact with the ground, just over the
Malian border in the Gao region.

While the flight-data recorder has allowed the investigation to
draw up a flightpath, aspects of the aircraft’s performance and
behaviour have yet to be assessed.

Jouty also states that the cockpit-voice recorder was “badly
damaged” in the impact.

Despite this, the tape inside was recovered and read but Jouty
says: “Unfortunately the recordings it contained cannot, so far,
be used.

“We’ve commenced actions to see whether we can extract
information from this tape. It’s too early to say whether we’ll
be able to achieve anything.”

He says there are unintelligible sounds on the tape but the
inquiry has not established the reasons why the recording is
poor. Jouty says that the problem is “not due to the crash”.

“We’re using the best specialists in the field to see what can be
done,” he adds.

Lack of cockpit-voice data has prompted the inquiry to
prioritise the collection of information from alternative sources,
including air-ground transmissions as well as possible
communications between the Swiftair pilots and the crews of
other aircraft.

“This should give us some information on what the crew
considered doing,” says Jouty.

Three international working groups will focus on the wreckage
and final trajectory of the aircraft, reconstruct the history of the
flight, and gather weather, air traffic control and other data.
Mali’s commission of inquiry, which is leading the investigation,
will publish an interim report in mid-September.