Controllers failed to notice the disappearance of a LAM Embraer 190 lost over Namibia and damage to its emergency locator transmitter contributed to a long delay in reaching the crash site.
Circumstances of the 29 November 2013 accident – the result of the captain’s deliberately piloting the jet into the ground – are likely to underpin the case for improvements to aircraft tracking.
The aircraft had been under radar surveillance in Botswanan airspace when it rapidly lost altitude until radar contact was lost at 14,100ft. Namibia’s wide-area multilateration system continued to track the descent to 6,600ft.
But Botswana’s Gaborone area centre controller did not realise the aircraft had deviated from its assigned altitude of 38,000ft. Botswana’s radar system did not trigger any alarm in response to the aircraft’s sudden departure from cruise.
The inquiry into the accident determined that only one controller – rather than the usual two – was overseeing the whole of Botswanan upper airspace, covering both east and west sectors.
While the Embraer had been operating in the west sector, the controller had been distracted by a false conflict report in the east sector, and failed to notice the disappearance.
Oblivious to the loss of contact, the Gaborone controller passed handover instructions to the crew as the aircraft prepared to enter Angolan airspace. But the crew did not respond and the flight also failed to report at the AGRAM waypoint to which it had previously been cleared.
The Namibian-led investigation found the Embraer’s emergency locator transmitter was “relatively intact” but had failed to generate a signal because its co-axial antenna cable had separated on impact.
“There was no reception of [locator] transmission by the global emergency centres,” says the inquiry.
With no alert activated by Gaborone air traffic control, the aircraft’s absence was not noted until nearly 2h later, when Angolan controllers in Luanda – the flight’s destination – informed Gaborone area centre that the flight had not made contact.
Namibian authorities initiated search-and-rescue efforts after establishing that the aircraft was missing, says the inquiry. But weather conditions forced the abandonment of the search until the following day, when the wreckage was located in Bwabwata national park.
Bwabwata is an extensive but remote region and the inquiry points out that a functioning emergency locator, capable of operating even after a high-energy impact, is essential to improving the efficiency of a search.
It suggests that locator transmitters could utilise an integral antenna rather than one which relies on a connection to a fuselage antenna.
Investigators have also recommended that ICAO should “expedite” the advancement of flight-tracking capabilities in order to provide early warning about abnormal aircraft behaviour.