Air speed sensors on the AF 447 Airbus A330-200 are the latest item to draw scrutiny as investigators try to ascertain through their only real clues so far -- a series of maintenance messages – what brought down the airliner with 228 on board.

Meanwhile, Brazilian authorities are saying the first bodies have been recovered, including with other wreckage from AF 447. According to local reports, seats and other items belonging to the aircraft are also now being salvaged.

Paul-Louis Arslanian, the head of the French air accident investigation office, BEA, says a pitot tube failure has not been identified the primary problem. However, he confirms that the mishap aircraft had not yet undergone a pitot tube upgrade Airbus had recommended to operators.

While stressing the pitot sensor has not been implicated, Arslanian says on any aircraft they can be contaminated and fail. He added that the upgrade recommendation does not imply the old device was faulty.

The pitot tube is drawing attention because some of the 24 Acars (automatic communications and reporting system) messages point to inconsistencies in speed measurements. The 24 messages were received during a four minute period before all contact with the aircraft was lost at 2:14 UTC. Fourteen of the Acars messages were received in the last minute alone.

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 - will also have triggered fault warnings, including the Air Data Inertial Reference Units.

Pilots would still be able to fly the aircraft, although operations are more challenging particularly in the potentially hazardous conditions the A330 was traversing. 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.

An A330 pilot says that in those conditions, flying with autopilot is advisable because a change in pitch can quickly lead to loss of control. The autopilot was switched off on the mishap aircraft, although it's not certain if the system automatically disabled or pilots chose to take control.

Investigators haven’t established if the pitot tube was contaminated, including ice crystals formal because of humid air as temperatures fell in the cumulonimbus cloud. One issue under review will be whether the AF 447 crew had opted to heat the pitot tube.

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 time the fatal sequence of events took place. 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 from the U.S., 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 detached.

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.

Among the many still unexplained issues is the lack of any communication from the flight crew. Arslanian said controllers had no reason to try to contact the aircraft until it was feared lost.

The aircraft was 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 ft., but was still at 35,000 ft. at the time of the mishap, says Alain Bouillard, who leads the accident investigation team.

[Graphics: BEA]