Turbulence likely cause of Mexico jet crash that killed ministers

Saturday, November 15, 2008

This image from a NASA test clearly shows how even small aircraft can produce powerful turbulence

Wake turbulence from a larger aircraft is believed to be the cause of a crash of a Mexican government Learjet 45 into rush-hour traffic in Mexico City earlier this month. All nine on board, including Interior Minister Juan Camilo Mourino, and five on the ground were killed.

As well as Mourino, anti-drug advisor Jose Luis Santiago Vasconcelos died in the wreck, leading to speculation of murder. There have been rumours the jet may have been sabotaged or bombed, but both of these have been ruled out, as have mechanical failure.

To try to prevent conspiracy theories, there has been unusual openness to the press over the accident. The investigation is being led by Mexico, who have been joined by teams from Britain and the United States.

Instead, the readout from the Cockpit Voice Recorder (CVR) coupled with the knowledge that the aircraft had come in too close behind another suggest the likely cause to be an encounter with wake turbulence - dangerously unstable air left behind by an aircraft as it passes through an area. The Learjet came within 4.15 nautical miles of a Boeing 767-300 on the same approach towards Mexico City International Airport, whereas for safety there should have been around 5 nautical miles of separation between the two.

It has also been revealed that air traffic control instructed the accident aircraft's flight crew to slow down to keep back from the airliner, but that this had not happened. The pilots may have lacked adequate training, as they are reported to have experienced difficulties and unfamiliarity with the plane's controls. The CVR transcript reveals that the pilots were aware they had hit severe turbulence immediately prior to the crash.

"Wow, check out this turbulence!" pilot Martin Oliva exclaimed to co-pilot Alvaro Sanchez. Apparently panic-stricken, he then asks "Alvaro, what should we do, Alvaro?" and is told "Give it [control of the aircraft] to me, give it to me, give it to me!" Sanchez then says simply "God."

It was to be his last word. The plane became uncontrollable and crashed down at a forty-two degree angle, killing all on board.

The investigation continues.


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