Namibian investigators have yet to conclude human factors assessments in their inquiry into the fatal loss of a Mozambican Embraer 190, but face the task of explaining apparent sabotage by the captain.
En route from Maputo to Luanda the aircraft had reached a waypoint designated EXEDU, within the Gaborone flight information region over Botswana, when it departed its flight level of 38,000ft and began to descend.
There is no evidence that the aircraft was behaving abnormally and no mechanical problems have emerged from the probe into the 29 November crash.
Initial findings from the inquiry, says a source familiar with the situation, show that the first officer left the cockpit for the lavatory a few minutes before the sudden descent.
Autopilot remained engaged for the entire accident sequence. Crucially there were several manual airspeed selections, and three altitude selection changes, the final one 592ft. Typical ground elevation in the region is over 3,000ft above sea level.
The probe has determined that the autothrottle of the aircraft was manually re-engaged and that the thrust level changed to idle.
Flight-data recordings – which were read by the US National Transportation Safety Board – indicate that the speed-brake was manually operated, deploying the spoilers, and that this remained the case throughout the remainder of the flight. The aircraft descended at an airspeed close to its maximum operating limit.
As the aircraft descended there were “low and high chimes”, says the source, as well as “repeated banging”, suggesting calls to enter the cockpit.
None of the occupants survived as the twinjet struck the ground in Namibia’s Mbwabwata National Park.
Investigators have yet to explain the actions, simply saying that they illustrate “clear intent” and that the reasons are “unknown”. A team is to explore regulatory and airline management matters as part of the effort to understand the event.