ANALYSIS: Airlines make advances in turbulence avoidance

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American Airlines has equipped more than 350 aircraft with a system it says provides pilots with more timely and accurate turbulence reports.

The airline tells Flightglobal that 367 of its Boeing 737, 757 and 767 aircraft are now fitted with the Turbulence Automated PIREP System manufactured by WSI, a division of The Weather Company, which is based in Andover, Massachusetts.

David Clark, American's senior manager for flight operations efficiency and quality control, tells Flightglobal that the system helps American ensure smoother, safer flights.

The system does not actually detect turbulence. However, it gives pilots more timely warnings of the possible presence of turbulence, facilitating avoidance, say experts.

"It's a step forward in that [pilots] don't have to go searching for turbulence reports," Peter Dunn, a former United Airlines captain and assistant professor of aeronautics at the Florida Institute of Technology, says of communications systems like WSI's.

Aircraft equipped with WSI's system automatically send turbulence reports, including accelerometer data, to WSI's data centre when they experience turbulence that exceeds set parameters, says WSI vice-president Mark Miller.

Those reports are reviewed by WSI's meteorologists and integrated with traditional pilot turbulence reports – so-called PIREPs – and weather information, including radar and satellite data and lightning and convection reports.

WSI then generates turbulence advisories, notifying customers of areas where turbulence may be present, Miller says.

Pilots and dispatchers can use the advisories to plan flightpaths, and dispatchers can transmit almost real-time advisories to pilots, who can print them in the air, says Miller.

WSI's turbulence information will become more accurate as more airlines adopt the technology, says Clark, because more users mean more reports will be filed with WSI.

The information will be particularly useful to pilots flying remote overwater routes where turbulence reports can be scarce, says Clark.

"The [other airlines], we hope, will follow suit. The more they participate, the more information we will have in the Pacific and Atlantic," he adds.

American spent about 18 months equipping its aircraft with the system. The airline has a fleet of 618 aircraft, including 221 737-800s, 92 757-200s and 69 767s, Flightglobal's Ascend Online database shows.

The airline is considering installing the technology on some of its 56 777 aircraft, but not on its 165 MD-80s, which will be retired as American takes delivery of new 737s and Airbus A319s and A321s, Clark says.

WSI declines to say which other customers use its system, but a significant percentage of aircraft in another North American airline's fleet have it, the company says.

Aircraft owned by an Asia Pacific-based carrier also have the system, and a European airline is in the final stages of receiving approval for its use, Miller adds.

Clark says one of the primary benefits is the timeliness of WSI's turbulence warnings, which can be transmitted to aircraft in almost real time.

By comparison, pilots flying aircraft without an automated system might wait 35-40min as updates are relayed through air traffic controllers and dispatchers, Clark says.

Despite forecasting advances, there remains a lot of mystery about turbulence, says Dunn from the Florida Institute of Technology.

Certain patterns of upper air movement are classic prescriptions for turbulence, he says. For instance, if the river of air called the jet stream is moving at, say, 125mph, pilots will likely find bumps along the stream's edge.

"It's like If you have three beers and follow that with three martinis, you can probably expect to have a headache in the morning," Dunn says.

But predicting the severity of the bumps is more uncertain, and sometimes pilots find smooth air in areas of expected turbulence, he adds: "What you can't tell is whether this river you are going down is the Amazon or... the Potomac."

Because of forecasting limitations, pilots primarily receive turbulence information from other pilots flying ahead of them, Dunn says, adding that many pilots give one- or two-word ride reports every time they transition to a new air traffic controller.

Pilots also monitor other pilots' radio conversations for turbulence tips, says Dunn.

The tone of the conversations reveals the extent of the turbulence, Dunn says: "When pilots start asking for different attitude, then you know that they are getting an uncomfortable ride."

JetBlue Airways tells Flightglobal that the most accurate and timely information comes while the aircraft is airborne, from others ahead of it.

When operating over water and out of radar coverage, pilots talk about turbulence over the radio, adds the airline, which does not use an automated turbulence reporting system.

JetBlue's pilots also use Apple iPads to view stored weather graphs. In the future, when more of JetBlue's fleet have wireless internet, pilots will be able to get updated weather graphs while in flight, adds the airline.

Dispatchers at US Airways, which is poised to merge with American in December, use WSI's flightplan guidance charts and other tools to select the best routes, considering factors like turbulence and convection activity, says Bob Skinner, US Airways' managing director of flight training and standards.

Pilots receive turbulence information in a flight release and weather package, which typically are printed 1h prior to departure, adds Skinner, who is also a US Airways captain.

Once airborne, pilots work with dispatchers and air traffic controllers to avoid turbulence, Skinner adds.

Southwest also uses a WSI turbulence-forecasting product to help plan smooth routes, and pilots in the cockpit receive turbulence updates through ACARS, the aircraft communications, addressing and reporting system, Southwest says.

Atlanta-based Delta Air Lines tells Flightglobal it uses a sensor-based reporting system to help plan for turbulence, adding that it is also testing new technology that it believe will provide improved identification of weather hazards.

Another US carrier, Virgin America, says it is also testing new turbulence technology, but does not elaborate.

Turbulence and storms remain a threat to commercial airliners, notes Dunn. "Look at what happened to Air France 447," he says.

Investigators suspect the Airbus A330-200's pitot tubes were obstructed by ice crystals as the aircraft passed through thunderstorms.

One of the pilots failed to the diagnose the problem and pulled up on the aircraft's stick, causing the aircraft to stall and crash in the Atlantic Ocean, investigators suspect.

All 228 passengers and crew died in the June 2009 accident.