Driven by the 2009 crash of an Air France Airbus A330 into the Atlantic Ocean, researchers at the U.S. National Center for Atmospheric Research (NCAR) have developed a prototype system that combines satellite data and computer weather models to map storms above remote ocean regions.
The information, which is assembled into eight-hour forecasts that are updated every three hours, is intended to alert pilots on transoceanic flights, as well as air traffic control (ATC), to the potential for dangerous weather conditions in time to allow them to alter their flight plans. The forecasts cover about half of the Atlantic Ocean and about two-thirds of the Pacific — the areas where the NCAR has access to geostationary satellite data.
Pilots of transoceanic flights currently have preflight weather briefings and, in some cases, updates about every four hours during flight, as well as onboard radar. These sources of information have limitations, however; for example, unforecast hazardous storms can develop quickly, and onboard radar cannot see through intense precipitation or long distances beyond the radar range.
As a result, the NCAR says, “pilots often must choose between detouring hundreds of miles around potentially stormy areas or flying through a region that may or may not contain intense weather,” including wind shear, icing conditions, lightning and turbulence.
“These new forecasts can help fill an important gap in our aviation system,” said Cathy Kessinger of NCAR, the project’s lead researcher. “Pilots have had limited information about atmospheric conditions as they fly over the ocean, where conditions can be severe. By providing them with a picture of where significant storms will be during an eight-hour period, the system can contribute to both the safety and comfort of passengers on flights over the ocean.”
The system allows for development of flight-specific maps that complement on-board radar systems, Kessinger said, noting that maps can be prepared for any airplane crossing, as long as the mapmakers know the airplane’s tail number and position. The final product is delivered by an aircraft communications addressing and reporting system (ACARS) printer on the flight deck.
“It shows what’s ahead, one to two hours, similar to on-board radar, but it sees farther,” she added. “On-board radar can see a rainstorm, but there can be attenuation problems. From a satellite, you can see how high the clouds are, and together, you get a more complete picture.”
For example, if the system had existed at the time of the Air France crash on June 1, 2009, it could have given the pilots of the Airbus A330-200 more information about the complex of storms that lay ahead of them on their planned route from Rio de Janeiro, Brazil, to Paris, and they could have altered their course, Kessinger said.
The system would have provided information similar to that shown in Figure 1, which depicts cloud top heights of 30,000 ft and 40,000 ft on June 1, 2009, at the last known position of the Air France flight.
Instead, according to the final accident report by the French Bureau d’Enquêtes et d’Analyses (BEA), about two hours after their departure, the pilots were told by the Air France operations center that they were approaching an area of developing convective activity. Soon afterward, the airplane flew into clouds in the inter-tropical convergence zone — an area near the equator characterized by warm, humid, buoyant air and frequent thunderstorms.1
Meteorological conditions there were “not exceptional for the month of June,” the accident report said. “There were powerful cumulonimbus clusters on the route of AF 447. Some of them could have been the centre of some notable turbulence.
“An additional meteorological analysis showed the presence of strong condensation towards AF 447’s flight level, probably associated with convection phenomena. The precise composition of the cloud masses above 30,000 ft is little known.”
The report added that the flight crews of other airplanes had altered their routes to avoid the clouds, and that the crew of the accident airplane had “made a heading change of 12 degrees to the left of their route.”
Ultimately, the airplane’s air data sources became unreliable, probably because ice crystals were obstructing pitot tubes, the report said. Although the pilots knew the data were incorrect, they did not conduct associated checklist procedures, and the airplane entered a stall and descended into the Atlantic, killing all 228 passengers and crewmembers.
Rain and Wind
Other pilots who might have benefitted from having information that the system can provide, Kessinger said, were those flying a United Airlines Boeing 747-400 from Sydney, Australia, to San Francisco on Feb. 19, 2013, when the airplane encountered turbulence over the Pacific Ocean. One flight attendant fell as she walked down an aisle and later was treated at a hospital for a broken wrist; the other 219 passengers and crewmembers were not injured.2
Although the seatbelt sign was illuminated, flight attendants had not been required to be seated, the NTSB said.
Kessinger said that, if the prototype system had been in place, the flight crew would have seen the storms in their path and expected strong convectively induced turbulence.
The Air France crash “focused industry attention to the need for additional, aircraft-specific weather information in the cockpit, particularly for transoceanic flights,” Kessinger and her colleagues wrote early this year in The Journal of Air Traffic Control.2 “As long-range and ultra-long-range intercontinental flights become routine, weather information provided during preflight planning may not be adequate when a flight most needs hazardous weather information. The main motivator for this research is the need for hazardous weather information updates in data-sparse regions while the aircraft is en route.”
They wrote that their work — funded by the U.S. National Aeronautics and Space Administration’s Applied Sciences Program and performed along with the Massachusetts Institute of Technology’s Lincoln Laboratory, the U.S. Naval Research Laboratory and the University of Wisconsin–Madison — had its roots in an earlier collaboration. That earlier effort, which involved the U.S. Federal Aviation Administration (FAA) Aviation Weather Research Program’s (AWRP’s) Oceanic Weather Product Development Team and United Airlines, focused on a satellite-based product that identified convective cloud top heights “on a two-waypoint look-ahead display that integrated the aircraft position and flight direction.”
When deep convection along the route was considered significant, the information was delivered to the flight crew of a United Boeing 777 in the form of an American Standard Code of Information Interchange (ASCII) character display on the flight deck’s ACARS printer.
The AWRP also demonstrated the uplink of a “look-ahead” turbulence-severity product, delivering the information to the flight decks of specific United airplanes.
“Once pilots became familiar with the character graphic and its underlying meteorological basis, they generally welcomed the updated information with its strategic awareness of deep convection or forecast turbulence along the flight’s vertical and horizontal profile,” the researchers wrote.
Nevertheless, they noted that better understanding is needed of the potential benefits, as well as related human factors and safety issues, of these systems for flight crewmembers, oceanic air traffic managers and airline dispatchers.
The prototype system was demonstrated in a research cockpit simulator — configured as an Airbus A320/330 — operated by the FAA’s William J. Hughes Technical Center, using weather scenarios from the inter-tropical convergence zone. Cloud top height information (CTOP) was “derived from GOES [geostationary operational environmental satellite] infrared imagery, mapped to flight level using model soundings and presented on an EFB [electronic flight bag] in both a character graphic display format [designed to resemble an ACARS printout] and a color graphic,” the researchers said.
In addition, satellite and radar weather data were depicted on the simulator’s navigation display. Four current, experienced pilots — with training in the cockpit simulator as well as the weather scenarios — flew the demonstration flights. ATC and dispatch communications were simulated as required throughout the demonstration.
The researchers said the enhanced weather information “was valuable in all aspects observed — crew situational awareness, workload reduction (ATC, dispatch and flight crew), more precise weather hazard avoidance and crew decision making.”
Pilots participating in the demonstration flights said afterward that the information made available by the system was “much more effective” than the basic weather information available on the flight deck. They said that the EFB character graphic was “understandable and desired in place of the updates” but that the color graphic displayed on the EFB was preferred.
The simulator demonstration showed that pilots “developed (and became proficient with) strategies that involved many small heading changes using the CTOP display for guidance, then supplementing these initial deviations with radar when the storms came into view,” the researchers said. “This minimized the total deviation from the course.”
Using the navigational display radar information alone, the researchers added that “pilots were tempted to thread the needle through the storm areas. However, the CTOP indicated the potential for attenuated returns behind the initial line of storms.”
The researchers wrote that additional research and product development are needed before the system can be implemented. Future demonstrations, they said, should use fully integrated EFBs and broadband Internet service, with a goal of enabling a “seamless transition from continental to oceanic weather updating.”
- BEA. Final Report on the Accident on 1st June 2009 to the Airbus A330-203, Registered F-CZCP, Operated by Air France, Flight AF 447, Rio de Janeiro–Paris (English translation). July 5, 2012.
- U.S. National Transportation Safety Board. Preliminary accident report No. WPR13LA131. Feb. 19, 2013.
- Lindholm, Tenny; Kessinger, Cathy; Blackburn, Gary; Gaydos, Andy. “Weather Technology in the Cockpit.” The Journal of Air Traffic Control Volume 55 (Quarter 1, 2013): 17–21.