Aviation News Item: 09269

3rd Jun 2010

Source: ubmaviationnews.com

The Transportation Safety Board of Canada (TSB) has issued a report into a wake turbulence incident between an Air Canada A319 and a United Airlines 747-400 on January 10, 2008, in which 11 people onboard the Airbus were injured. The narrowbody was cruising at flight level (FL) 350 below the 747 (FL370) at a lower speed and slightly diverging course over the state of Washington, US. When the two aircraft were 8.1nm apart, the A319 was instructed by air traffic control (ATC) to climb to FL370. As the Airbus was climbing through FL366, 10.7nm behind the 747, sharp jolts were felt and the aircraft rolled 5.6 degrees to the right, which was countered by the autopilot with aileron input. The aircraft then rolled past wings level to 27.8 degrees left. When this roll was near its maximum, the captain disengaged the autopilot and autothrottles and attempted to correct the roll manually.
The crew assumed they had a flight control problem and were unaware the aircraft had encountered wake turbulence. The captain reacted to the roll movement with alternating aileron and rudder inputs, including six cyclic rudder reversals from left to right. This was followed by a series of four rolls with varying bank angles of up to 55 degrees. During the roll oscillations, the aircraft continued the climb to FL369 and then descended to FL355, where the pilots regained straight and level flight. The crew declared an emergency and diverted the flight to Calgary International Airport, Alberta where it landed uneventfully. A post-flight inspection revealed that the rear vertical stabiliser attachment fitting was subjected to loads of 129 per cent of limit load, and the rear fuselage fitting to 121 per cent of limit load.

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