AF447 crash probe urges tracking mandate

Air accident chiefs investigating the fatal Air France Flight 447 flight are urging UN aviation agency ICAO to make ADS-C tracking technology and datalink mandatory in those zones where high frequency radio (HF) remains the only means of communication.

France’s Bureau d’Enquêtes et d’Analyses (BEA) stated in its final report into the 2009 crash of the A330 aircraft that radio communications with air traffic control on the day of the accident were unreliable.

An interim report of the AF447 accident investigation earlier revealed that;

• It took five days to find the first floating wreckage,
• The last position report made by the crew was at 01:35 GMT and the last automated report was at 02:10, but the first alerts to start a search and rescue effort were only raised between 08:00 and 08:30,
• The crew made three attempts to contact the Dakar air traffic control using FANS1/A technology but had not succeeded by the time the aircraft was lost.

A ICAO High Level Safety Conference later identified issues surrounding coordination between Atlantico and Dakar Flight Information Region (FIRs) as contributing to the excessive delay in alerting the search and rescue (SAR) services to the disappearance of AF447.

Recounting the controllers’ and crew’s planned actions, the BEA said that before entering the Atlantico FIR, the controller of the Recife Area Control Centre (ACC) had asked the crew to contact his counterpart in the Dakar Oceanic ACC after reaching the TASIL waypoint.

“This practice enabled the crew to leave Atlantico FIR even in the event of loss of HF radio contact, which must have been quite common. The crew of Flight 447, in these conditions, probably considered that it was not necessary to make other position reports before TASIL. The crew was doubtless counting on a SELCAL call from the controller of Atlantico ACC in case of need after passing INTOL point,” said BEA.

SELCAL, or Selective Calling, is a signalling system used in conjunction with HF radio communications. It is used to alert pilots communicating with air traffic control of an incoming radio message on HF.

“The controller of Atlantico ACC could have expected to receive position reports from the crew when they passed SALPU and ORARO points. Because of the bad quality of the HF noted on that day, he was not surprised by this and he doubtless did not make the call via SELCAL, considering that he would not, in those conditions, receive an answer,” said the BEA.

“This lack of radio contacts was likely interpreted as normal by all those involved. It contributed to making the controller lose awareness of Flight 447. The relieving of the Atlantico ACC controller shortly before the expected exit of Atlantico FIR may have reinforced this loss of awareness.”

BEA said that the lack of contact between the Atlantico ACC controller and the crew before the transfer to Dakar oceanic ACC, then the lack of contact between the Dakar oceanic ACC controller and the Atlantico ACC controller after the estimated passage of the TASIL point meant that Flight 447 was not monitored effectively.

“These strategies of deferring information led in fact to the suspension of the alert service in each of these FIRs, thus compromising the triggering of alerts within appropriate timeframes,” the BEA said.

BEA also reported that a Eurocat system installed in the Senegal operations room was being assessed in an experimental context on the day of the event and was partly replacing the system in place.

“It was not accompanied by training for all the controllers on duty, or with user guidelines. The specifics of its use were consequently poorly understood,” said the BEA.

BEA called this an ‘ambiguous’ use of a non-operational system in a control room which encouraged the creation of a representation of Flight AF447 in the Dakar centre with no connection with its real position, a situation which distanced the controller from monitoring his traffic.

A failure to detect an error in the formatting of a flight plan in the Eurocat system made it impossible for the crew to establish a satellite connection with a view to a position report by ADS-C, or exchanges by Controller Pilot Data Link Communications (CPDLC).

“However, a simulation of the flight that was undertaken in the context of the investigation showed that ADS-C connection would likely have alerted the controller [in both Brazil and Senegal] as soon as there was a loss of altitude generated by the loss of Mach (330 feet),” the BEA stated.

The BEA said it would recommend that €€the Brazilian and Senegalese authorities make mandatory airlines’ use of ADS-C and CPDLC functions in vulnerable zones. It said it would also recommend that €€ICAO request the two states to accelerate the operational implementation of air traffic control and communication systems that would provide a permanent and reliable link.

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