RECIFE, Brazil – Air France and other airlines moved Tuesday to replace speed monitors suspected of feeding false information to the computers of Flight 447 and leading to a series of failures that broke the plane apart over the Atlantic Ocean. Four more bodies were pulled from the sea, and helicopters began ferrying other remains to shore.
A total of 28 bodies have been recovered; 200 others have yet to be found. Soldiers and medical personnel in surgical gowns carried off the remains in body bags on the Fernando de Noronha archipelago, to be flown to the coastal city of Recife, where experts will try to identify them using DNA and photos.
Identifying the bodies, looking at where they were seated on the plane and studying their injuries could provide clues to causes of the May 31 disaster, according to Peter Goelz, a former managing director of the National Transportation Safety Board.
"Since the victims from this tragedy came from all parts of the globe, international collaboration will be essential," Interpol Secretary General Ronald K. Noble said.
With the plane's data recorders still apparently deep in the ocean, investigators have been focusing on the possibility that external speed monitors — called Pitot tubes — iced over and gave false readings to the plane's computers in a thunderstorm.
The L-shaped metal tubes jut from the wing or fuselage of a plane, and are heated to prevent icing. The pressure of air entering the tubes lets sensors measure the speed and angle of flight. A malfunctioning Pitot tube could mislead computers controlling the plane to dangerously accelerate or decelerate.
Air France said it began replacing the Pitot tubes on its A330 and A340 jets in May after pilots reported several incidents of icing leading to a loss of airspeed data, and that it had already replaced the Pitots in smaller A320 jets after similar problems were reported.
"What we know is that other planes that have experienced incorrect airspeed indications have had the same Pitots. And airplanes with the new Pitot tubes have never had such problems," said Air France pilot Eric Derivry, a spokesman for the SNPL pilots union.
While no cause has been established for the disaster, Derivry said the Pitot failures create "a web of presumptions, but only presumptions," that they "could be a contributing factor."
The monitors had not yet been replaced on the A330 that was destroyed en route from Rio de Janeiro to Paris.
On Tuesday, the airline assured its pilots that none of its A330s or A340s would fly without at least two of the new instruments, and that all Air France A330s and A340s will have all three Pitots replaced by July.
Brazil's air force, meanwhile, said it is replacing the Pitot tubes on an Airbus A319 used by Brazil's president because of a recommendation the jet's manufacturer made more than a month before the Air France crash.
A memo sent to Air France pilots Monday by its smaller Alter union and obtained by The Associated Press urged them not to fly unless at least two of the three Pitot sensors on each plane had been replaced, citing a "strong presumption" among its pilot members that a Pitot problem precipitated the crash.
The union's memo also warned of a "real risk of loss of control" due to Pitot problems. But other pilots have said that the planes should remain flyable even if Pitot tubes ice over in thunderstorms. And the European Aviation Safety Agency issued a precautionary safety bulletin Tuesday reminding operators about existing procedures to safely fly the aircraft even when air speed indicators malfunction.
"We are aware of issues with this in the past, but at no time were they classified as safety-critical, neither by the authorities nor by the manufacturer," said Daniel Hoeltgen, the agency's spokesman.
Thales made the Pitot tubes on the jet that crashed, company spokeswoman Caroline Philips confirmed.
Some other carriers — including Delta Air Lines Inc. and the Middle East's Qatar Airways — said they are working to upgrade the devices on dozens of Airbus planes, and are warning pilots in the meantime.
"Until these installations are complete, we are communicating with our flight crews to reiterate the correct procedures to be used in the event of unreliable airspeed indications," Delta spokeswoman Betsy Talton said.
Delta subsidiary Northwest Airlines also has installed new Pitot tubes on its A319/320 aircraft, Talton said.
Some other major Airbus operators suggested Tuesday that the problem was isolated to Thales instruments, stressing that their aircraft use the Goodrich model and had no problems related to icing or loss of data. Executives at Dubai-based Emirates Airlines, Abu-Dhabi-based Either Airways and Qantas Airways were among those making this point.
"We are not concerned because its a different system in our aircraft," Qantas General Manager for Government and Corporate Affairs David Epstein said.
Airline industry officials also rallied to defend Airbus. At an industry conference in Kuala Lumpur, Emirates Airlines President Tim Clark said the Dubai-based company's 29 A330-200 planes have been flying since 1998 "and there is absolutely no reason why there should be any question over this plane. It is one of the best flying today."
Brazil's air force said search crews had recovered the vertical stabilizer from the tail section of Flight 447 — which also could provide key clues as to why the airliner went down and where best to search for the black boxes, which are located in the fuselage near the tail.
From images of the recovered tail section, the damage looks like a lateral fracture, said William Waldock, who teaches air crash investigation at Embry-Riddle Aeronautical University in Prescott, Arizona.
"That would reinforce the idea that the plane broke up in flight," Waldock said. "If it hits intact, everything shatters in tiny pieces."
Goelz said the faulty airspeed readings and the fact that the vertical stabilizer was sheared from the jet could be related.
The Airbus A330-200 has a "rudder limiter" which restricts the movement of the rudder — another part of the tail section — at high speeds. If it were to move too far while traveling fast, it could shear off and take the vertical stabilizer with it.
"If you had a wrong speed being fed to the computer by the Pitot tube, it might allow the rudder to over-travel," Goelz said.
Asked if the rudder or stabilizer being sheared off could have brought the jet down, Goelz said: "Absolutely. You need a rudder. And you need the (rudder) limiter on there to make sure the rudder doesn't get torn off or cause havoc with the plane's aerodynamics."
With the discovery of debris and bodies 45 miles (70 kilometers) from where the jet was last heard from, searchers are narrowing their hunt for the cockpit voice and flight data recorders. They must move quickly — acoustic beacons or "pingers" on the black boxes begin to fade 30 days after crashes.
The U.S. Navy is providing devices capable of picking up the pingers to a depth of 20,000 feet (6,100 meters) that will be slowly towed in a grid pattern across the search area. The French nuclear attack submarine Emeraude, arriving later this week, also will try to find the acoustic pings.
France, Brazil and the Pentagon have said there are no signs that terrorism was involved in the crash.