teams have recovered 17 bodies so far, and wreckage from the Atlantic
Ocean off the coast of Brazil from Air France Flight 447, an A330-200
that accident investigators have revealed had not yet undergone a pitot
tube upgrade the airline was introducing throughout its fleet.
Air speed sensors have come
into focus early in the investigation of what happed to AF 447 when
it crashed a week ago on its way from Rio de Janeiro to Paris with 228
persons on board.
The pitot tube is drawing attention
because some of the 24 Acars (automatic communications and reporting
system) messages point to inconsistencies in speed measurements on the
aircraft just before all contact was lost at 2:14 UTC. The 24 messages
were received during a four minute period, with 14 received in the last
The Acars messages point to
a discrepancy between three of the aircraft's speed data inputs of more
than 30 knots within a period of less than a second. As a result, the
system reported a fault and other subsystems - relying on the speed
data - also triggered fault warnings, including the Air Data Inertial
Paul-Louis Arslanian, the head
of the French air accident investigation office, BEA, says a pitot tube
failure has not been confirmed, merely that the Acars messages point
to speed sensors disagreeing with each other. However, he confirms that
the aircraft had not yet undergone a pitot tube upgrade the airline
In a statement defending its
actions, Air France says only since May of last year has it seen increased
loss of air speed data associated with icing in the pitot probes on
A330s and A340s and argues it has been instrumental in driving the upgrade
The airline says it upgraded
pitot probes on A320 narrow bodies following Airbus's advice in September
2007 to do so; it didn't do so on the Airbus wide bodies because at
the time water ingestion did not appear to be a problem and no recommendation
had been made to do so. Air France insists it asked for a fix once it
started seeing anomalies on its A330s and A340s, but that Airbus at
first said the A320 issue was different. The carrier says Airbus only
let it be known that the A320 improvement could also benefit the A330
and A340. Once it heard that, Air France says it launched the A330,
A340 pitot tube upgrade program on April 27 without waiting for a recommendation
The pitot tube upgrade Airbus
developed is designed to improve measurement capability of the system.
While stressing the pitot sensor
has not been implicated, Arslanian says on any aircraft these probes
can be contaminated and fail. He added that the upgrade program does
not imply the old device was faulty.
Industry officials and pilots
note that the aircraft should still be flyable even if the speed sensors
malfunctioned, suggesting if the anomaly turns out to be related to
the crash, it would likely be only one in a series of events that brought
down AF 447.
However, flying the aircraft
would be more challenging with such a system anomaly, particularly in
the potentially hazardous conditions the A330 was traversing. One of
the Acars messages indicates the autopilot was turned off, possibly
automatically. Meteorologists supporting the BEA have identified a severe
cumulonimbus cloud in the area the A330 was flying, but have not been
able to pinpoint exactly the conditions the aircraft had to pass through.
After the accident, Airbus
sent a reminder to pilots of all its aircraft types on maintaining proper
speed and on other procedures when flying with ambiguous speed information.
Arslanian notes such a message to operators is routine.
He also points out that the
regular Acars reports on aircraft location and speed indicate a routine
flight up to the incident. However, he also notes that the Acars messages
have so far not allowed investigators to draw conclusions about aircraft
speed around the final minutes of the flight. And, he adds, the data
from Acars may be insufficient to ever establish that information.
"For the time being, we
are working with what we have, which isn't much," Arslanian says.
A French vessel, two American
ships and a French nuclear submarine will try to track down the cockpit
voice and data recorders. The ships will tow microphones to detect the
37.5 kHz signal. However, Arslanian reiterated concerns the recorders
may not be found and notes the pinger emitting the signal could have
Meanwhile, the French navy's
oceanographic office will try to gain a better sense of what the sea-bed
looks like, to aid recovery operations, says Laurent Kerleguer, from
the oceanographic department. The ocean in the region can be up to 4,600
meters deep, but is very mountainous leading to elevations where the
ocean floor is only 860 meters. The Pourquoi Pas vessel has been dispatched
to undertake the research.
The aircraft departed Rio de
Janeiro at 10:03 UTC on its way to Paris. The A330 took off with a weight
of 233 metric tons and 68 metric tons of fuel. It was climbing to 37,000
feet, but was still at 35,000 feet at the time of the mishap, says Alain
Bouillard, who leads the accident investigation team.
Photo credit: Airbus