Wake turbulence studied in crash of Learjet in Mexico

 - December 1, 2008, 5:52 AM

On November 4 Learjet 45 XC-VMC crashed into a mixed residential and commercial area in central Mexico City during an approach to Benito Juarez International Airport in clear weather. All nine occupants were killed. Five people on the ground were also killed and another 40 people injured.

The aircraft was owned by Mexico’s Interior Ministry but operated under contract by a private company. Capt. Martín de Jesús Oliva Pérez and copilot Álvaro Sánchez y Jiménez were both rated in the aircraft.

According to Mexico’s state-run Notimex news agency, Gilberto Lopez Meyer, Mexico’s director of airports and auxiliary services, issued a statement saying the crash was the result of the left engine separating from the aircraft at approximately 150 to 186 mph while on approach over central Mexico City.

When release of the passenger list showed that Mexican Interior Secretary Juan Camilo Mourino, 37, and Jose Luis Santiago Vasconcelos were among those on board the Learjet, speculation about sabotage ran rife.

Mourino was in charge of Mexico’s domestic security and was one of President Felipe Calderon’s top aides. Vasconcelos was a former key player in the war on drugs and a well known anti-drug prosecutor. He had survived attempts on his life.

Luis Téllez, Mexican secretary of communication and transportation, said an examination of the wreckage did not indicate any trace of explosives. Investigators determined that the engines were functioning at high speed and the aircraft did not explode in flight because the wreckage was confined to a small area on the ground.

A preliminary report suggests pilot error as a result of encountering wake turbulence from an airliner it was following on approach. Téllez said the evidence indicates the Learjet approached a Boeing 767-300 at a distance that was less than the norm. Just before the crash, the Learjet was 4.15 nm behind the 767. Standard flight procedures require a separation of 5 nm.

Téllez continued, “We also have preliminary evidence that the crew was not sufficiently familiar with operating the Learjet 45. The flight’s voice recorder showed that the crew felt the turbulence just before the pilot lost control” and, according to Téllez, revealed that the pilots’ voices reflected “anguish, impotence and frustration.”

The communication secretary emphasized that these were preliminary findings and it would likely be several months before all the facts are known. The NTSB, the UK’s Civil Aviation Authority and representatives from Bombardier, the aircraft manufacturer, and Honeywell, the engine manufacturer, are assisting with the investigation.