Avoiding Air Turbulence

Air Safety Week, Jan 21, 2008

Will air transport pilots soon have better ways to avoid clear air turbulence?

Two American and one British researcher may have developed an improvement in forecasting severe bumps in the air.

They will present two papers on the subject at the 13th Aviation, Range, and Aerospace Meteorology Conference on Jan. 21-24. The conference is part of the American Meteorological Society's Annual Meeting in New Orleans, LA.

The papers describe a new, more consistently successful technique for forecasting clear air turbulence. They build on a method developed earlier by one of the researchers, Donald McCann.

A New Direction in Clear-Air Turbulence Forecasting Based on Spontaneous Imbalance, Part I: Application of Theory will be presented by co-authors John Knox, University of Georgia; Donald McCann, McCann Aviation Weather Research; and Paul Williams, University of Reading, UK. The second paper entitled A New Direction in Clear-Air Turbulence Forecasting Based on Spontaneous Imbalance, Part II: Case Studies and Statistical Results will be briefed by co-authors McCann, Knox, and Williams. More information is available at www.mccannawr.com

Research into clear air turbulence continues as a recent rash of non- fatal incidents was logged by the news media, Canada's Transportation Safety Board (TSB) and the U.S. National Transportation Safety Board (NTSB). The latest incidents show that injury due to air turbulence remains a safety issue.

Air Canada Flight AC190, enroute to Toronto from Victoria, British Columbia, was diverted to Calgary, Alberta, on Jan. 10 after it experienced severe turbulence while flying over the Rocky Mountains.

The Airbus A319 was carrying 83 passengers and five crewmembers. Ten of those onboard, including two of the flight attendants buffeted about the cabin, were taken to local hospitals for treatment of minor non-life-threatening injuries and released.

Canada's Transportation Safety Board is investigating. A TSB spokesman is quoted as saying the A319 experienced control problems while in level flight at 35,000 feet.

An Air Canada spokesman wouldn't speculate on what the cause was, whether turbulence or otherwise. "All I can say is that as soon as the incident took place, the employees involved took the decision to divert the plane to Calgary. There will not only be an internal investigation but a governmental investigation to determine the cause," the Air Canada official reportedly stated.

But is possible that the Air Canada jetliner did not run into clear air turbulence but instead experienced wake turbulence from another civil transport. The U.S. National Transportation Safety Board (NTSB) is investigating whether a United Airlines aircraft, flying just ahead of the Air Canada Airbus, created wake turbulence that the Air Canada A319 encountered.

The NTSB is assisting the TSB with its investigation of the incident. They are analyzing the flight data recorder of the United aircraft and will pass on raw data to Canadian investigators.

And Christmas Day, Dec. 25, was upsetting passengers and crew aboard Alaska Airlines and Northwest Airlines flights.

On Christmas morning, a McDonnell Douglas DC-9-83 (N943AS) encountered severe turbulence during descent for landing at Ontario International Airport (ONT), Ontario, CA.

The twinjet, operated by Alaska Airlines as Flight 464, was not damaged. But one flight attendant sustained a serious injury and another flight attendant received minor injuries. The third flight attendant, the two flight crewmembers and the 109 passengers were not injured. Visual meteorological conditions prevailed, and an instrument flight rules flight plan was filed for the regularly scheduled domestic passenger flight. The flight had departed Seattle, Washington for Ontario.

According to information provided by Alaska Airlines, the flight was descending on the ONT ZIGGY 4 arrival in the vicinity of ZIGGY at an altitude of 8,300 to 8,500 feet above mean sea level when it encountered severe turbulence.

The two flight attendants who sustained injuries were both standing, completing final cabin duties in preparation for landing, when they were both knocked to the floor during the turbulence encounter.

Also on December 25, an Airbus A330-323 (N819NW) encountered severe turbulence during cruise flight approximately 1,300 nautical miles west of Honolulu, Hawaii.

The Airbus transport being operated by Northwest Airlines as Flight 16, was not damaged, but one flight attendant sustained serious injuries and another flight attendant and one passenger received minor injuries. The other seven flight attendants, 283 passengers, and three flight crewmembers were uninjured.

Night visual meteorological conditions prevailed, and an instrument flight rules flight plan was filed for the regularly scheduled international passenger flight. The flight had departed from Osaka, Japan for Honolulu. Following the severe turbulence encounter, the flight continued to Honolulu and landed without further incident.