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Testimony before the Committee on Transportation and Infrastructure Subcommittee on Aviation House of Representatives Regarding Aviation Operations During Severe Weather Conditions
Jim Hall
Committee on Transportation and Infrastructure Subcommittee on Aviation House of Representatives Regarding Aviation Operations During Severe Weather Conditions
7/22/1999

Oral testimony as presented:

Chairman Duncan and Members of the Committee, it is a pleasure to represent the National Transportation Safety Board before you today to discuss hazardous weather and aviation safety in the airport terminal area.

Before I begin, I would like to introduce Dr. Bernard Loeb, Director of the Board's Office of Aviation Safety.

Weather-related aviation accidents occur too frequently. Current data indicates that 33% of all fatal accidents are weather related. Of the weather-related fatal accidents that occur, close to 40% occur in the airport terminal area.

Weather hazards in the airport terminal area continue to be a significant safety concern. These hazards include: low ceilings and visibility; airplane airframe icing, both on the ground and airborne in the airport terminal area; runway contamination by ice, snow, and water; and thunderstorms and convective activity, which produces low-altitude windshear, strong and gusty winds, heavy rains, hail, and lightning. As the recent accident in Little Rock, Arkansas, that took the lives of 11 people shows, thunderstorms and convective activity continue to be among the most significant issues in aviation, especially in the airport terminal area.

The Little Rock accident occurred June 1, 1999, and involved American Airlines flight 1420, an MD-82 on a flight from Dallas, Texas, to Little Rock. The aircraft crashed after landing, resulting in 11 fatalities, including the captain. At the time of the accident, there were heavy thunderstorms in the area of the airport. Although the investigation is ongoing, we can share the following preliminary information on the weather conditions with you.

    · A thunderstorm was in progress at the airport at the time of the accident. As you are aware, the National Weather Service provides six levels of weather echo intensity; Level 1 is a weak intensity with light to moderate turbulence, and Level 6 is extreme with possible severe turbulence. Level 6 was reported in the airport area at the time of the accident. The two charts show Little Rock's National Weather Service Doppler weather radar for the approximately five minutes leading up to the accident. The center of the airport is located at the cross marked with LIT. This type of information is not provided to the controllers.

    · Before the accident, the NWS issued a Convective SIGMET advisory for severe thunderstorms, and a Severe Weather Forecast Alert was in effect for an area that included the airport, both of which the pilot received. A Severe Thunderstorm Warning to the public was issued by the NWS and was in effect for an area that included the Little Rock airport. This information is also not provided to the controllers or flight crew. The Severe Thunderstorm Warning is not an aviation product and is not typically provided to air traffic control or flight crews. We will be evaluating this issue as part of our investigation.

    · The airport did not have a Terminal Doppler Weather Radar or an Airport Surveillance Radar with the ability to depict weather echoes and intensities. It did have an improved Low Level Windshear Alert System that issued several alerts prior to the accident which the pilot did receive. The pilot also received updates on the winds during the final approach.

    · A Doppler weather radar operated by the National Weather Service was located six nautical miles north-northwest of the airport and provided detailed and accurate information on the thunderstorms, including wind speeds, in the Little Rock area to NWS personnel. NWS personnel used this information to formulate and disseminate severe weather warnings to the public. However, this information was not available in real time to the flight crew, air traffic control personnel, or approach control. Safety Board investigators are looking into this issue as part of its investigation.

    · According to an interview with the first officer, the flight crew was using their airborne weather avoidance radar to display the location and intensity of the thunderstorms. The thunderstorms in the airport terminal area should have been displayed on the aircraft's radar as significant weather echoes indicating hazardous weather. This issue is also being looked into as part of the Board's investigation.

Because the Safety Board's investigation is on-going, no conclusions have been reached; however, there are a number of important questions that are being addressed, such as:

    · Why did the flight crew continue the approach and landing at Little Rock?

    · What additional weather information and training should flight crews have to augment their decision-making process?

    · What was the aircraft airborne avoidance weather radar showing, and how are flight crews trained to interpret and use the radar display?

    · What are the limitations of airborne weather avoidance radar in the terminal area and what improvements need to be made?

The Safety Board will be considering all of these concerns in its investigation of the accident at Little Rock, evaluating what actions should be taken to address the concerns, and developing, as appropriate, recommendations for corrective action.

Two days after the Little Rock accident, on June 3, 1999, the Massachusetts Institute of Technology's Lincoln Laboratories issued a report sponsored by NASA's Ames Research Center entitled "An Assessment of Thunderstorm Penetrations and Deviations by Commercial Aircraft in the Terminal Area," focusing on Dallas-Fort Worth airspace. The report's findings are based on data from slightly more than 60 hours of convective weather. During that time there were nearly 2,000 airplane encounters with that type of weather.

The report indicates that almost two-thirds of the airplane encounters resulted in the airplane flying through the convective activity. Instead of deviating around storms in the airspace around an airport while approaching to land, pilots regularly penetrated storms with significant precipitation. Arriving aircraft were more likely to penetrate storms when they were following another aircraft, more than 15 minutes behind on their scheduled trip, or flying after dark. This information is disconcerting, as it suggests there is a tendency for air carrier pilots to penetrate convective activity, similar to that at Little Rock, near the airport.

Mr. Chairman, we are encouraged with the development of much needed equipment and other recent improvements with regard to weather reporting and dissemination. However, the most up-to-date technology is ineffective unless flight crews reexamine their decision-making process, and airlines reevaluate their procedures and training regarding flight in and near significant weather echoes located in the airport terminal area.

That completes my formal testimony, Mr. Chairman. I would be pleased to respond to any questions you may have.


 

for the record:

Chairman Duncan and Members of the Committee, it is a pleasure to represent the National Transportation Safety Board before you today to discuss hazardous weather and aviation safety in the airport terminal area.

Weather-related aviation accidents occur too frequently. Current data indicates that 33% of all fatal accidents are weather related. Of the weather-related fatal accidents that occur, close to 40% occur in the airport terminal area.

Weather hazards in the airport terminal area continue to be a significant safety concern. These hazards include: low ceilings and visibility; airplane airframe icing, both on the ground and airborne in the airport terminal area; runway contamination by ice, snow, and water; and thunderstorms and convective activity, which produces low-altitude windshear, strong and gusty winds, heavy rains, hail, and lightning. As the recent accident in Little Rock, Arkansas, that took the lives of 11 people shows, thunderstorms and convective activity continue to be among the most significant issues in aviation, especially in the airport terminal area.

Prior to the Little Rock accident, some of the worst aviation accidents in the United States over past 25 years involved thunderstorms and convective activity in the airport terminal area, including:

    · June 1975 - an Eastern Airlines Boeing 727 crashed on approach to John F. Kennedy International Airport resulting in 113 fatalities;

    · July 1982 - a Pan American Airlines Boeing 727 crashed following takeoff at New Orleans International Airport, Kenner, Louisiana, resulting in 153 fatalities;

    · August 1985 - a Delta Airlines Lockheed L-1011 crashed on approach to Dallas/Ft. Worth International Airport, Texas, resulting in 135 fatalities; and

    · July 1994 -- a USAir DC-9 crashed following a missed approach at Charlotte/Douglas International Airport, Charlotte, North Carolina, resulting in 37 fatalities.

As a result of the earlier accidents and other weather-related investigations, the Safety Board has issued over 120 weather-related safety recommendations, many of which addressed the hazards of thunderstorms and convective activity in the airport terminal area. Those recommendations deal with the need to disseminate real time, accurate weather information to flight crews and air traffic control personnel; the need to develop and implement weather systems to detect and warn of hazardous weather in the airport terminal area; and flight crew procedures and training in areas of hazardous weather.

Mr. Chairman, as a result of our safety recommendations, and with the support of this Committee, industry, and other government agencies, ground-based weather systems have been put in place at many major airports to detect and warn of the hazards associated with thunderstorms and convective activity, such as low altitude windshear and strong gusty winds. These systems include the Terminal Doppler Weather Radar (TDWR), Airport Surveillance Radar (ASR-9) with weather echo discrimination, and the improved Low Level Windshear Alert System (LLWAS). There are currently 39 TDWRs in operation at high threat airports such as Atlanta, Georgia; Denver, Colorado; and St. Louis, Missouri. A total of 45 TDWRs will be installed by the year 2000. There are approximately 110 LLWASs and 125 ASR-9s with weather echo discrimination now in service. The ASR-9s, in addition to providing aircraft position and data, provide six levels of weather echo intensity information to controllers. Five additional ASR-9s will be commissioned over the next three years.

In addition, much more work is in progress as a result of Safety Board recommendations asking the FAA to address thunderstorm and convective hazards in the airport terminal areas. In June 1990, the Safety Board recommended that a modular windshear detection enhancement to the ASR-9 be developed, and that the enhanced equipment -- ASR-9 Weather System Processor (WSP) -- be installed at air carrier airports not scheduled for a TDWR system or as an interim measure at airports scheduled for late TDWR installations (A-90-84). This recommendation is in an open acceptable status, and the FAA has developed the windshear enhancement to the ASR-9 and is moving ahead with the deployment of the ASR-9 WSP. There are currently two prototype WSPs in operation in Albuquerque, New Mexico and Austin, Texas. Approximately 35 WSPs will be implemented at moderate traffic density or high density airports that do not have a high threat of severe weather such as Norfolk, Virginia; Birmingham, Alabama; and Los Angeles, California, between 2000 to 2002. The ASR-9 WSP will provide windshear, gust front, and wind shift detections, as well as a forecast of convective storm motion.

Following the USAir accident at Charlotte, North Carolina, the Safety Board recommended that the FAA review all LLWAS installations and make necessary changes to ensure optimum performance of the system (A-95-47). The FAA has accepted this recommendation and plans to complete upgrades to the system by replacing and/or relocating sensor poles and installing new hardware and software. The FAA expects completion of system upgrades by 2001.

The Safety Board also recommended that the FAA re-evaluate the CWSU program and that procedures be developed to enable meteorologists to disseminate information about rapidly developing hazardous weather conditions, such as thunderstorms and low altitude windshear, to FAA Terminal Radar Approach Controls (TRACONs) and tower facilities immediately upon detection (A-95-48). The FAA is complying with the intent of this recommendation by standardizing CWSU operations on a national basis. In addition, the FAA is working with the NWS to rewrite the national CWSU order to reflect air traffic requirements for hazardous weather support and dissemination.

An important and valuable program now in development is the Integrated Terminal Weather System (ITWS), a ground-based system which will integrate data from FAA and NWS sensor systems, such as the TDWR, LLWAS, and the national network of Doppler Weather Radars (WSR-88D) to provide a suite of weather information products to pilots and controllers, such as thunderstorm intensity, location and motion, as well as thunderstorm gust front predictions. There are currently four ITWS prototypes in operation -- Memphis, Tennessee; Orlando, Florida; Dallas, Texas; and New York -- and future enhancements include a 30-60- minute organized convection forecast product and enhanced ITWS product distribution to airline dispatch. Approximately 34 ITWS systems, placed at locations where there is a TDWR, are scheduled to be installed during the 2001 to 2002 time frame.

Mr. Chairman, although we are encouraged with the development of this much needed equipment and other recent improvements with regard to weather reporting and dissemination, the Board has been concerned about the timeliness of the scheduled implementation of the needed equipment. The recommendation regarding the enhanced ASR-9 system was issued in 1990; we currently have only two prototypes in operation. The recommendation that all LLWAS installations be reviewed and necessary changes made to ensure optimum performance was issued in 1995; system upgrades will not be completed until 2001. We urge that development and installation of much needed technology be expedited.

Mr. Chairman, according to the FAA, there are approximately 380 airports with scheduled air service -- most of those airports will not have TDWR, ASR-9 WSP, ITWS, or LLWAS. It is imperative that a program be developed and implemented that integrates the enormous amount of valuable weather information available from a variety of other systems, such as the national networks of Doppler Weather Radars (WSR-88D), automated surface observations systems, and lightning detection systems. Such information must be rapidly disseminated to flight crews, air traffic controllers, and dispatchers, in an economical, user friendly format. The timeliness of such a program is imperative.

NASA has developed an Aviation Weather Information (AWIN) program which will provide improved weather information, including thunderstorms, windshear, and turbulence, not simply data, to users in the National Airspace System, and will foster improved usage of this information. AWIN will provide this information to the flight deck and other weather information users such as air traffic controllers and airline dispatchers. We believe this is an important and valuable aviation safety program that can improve the safety of air travel, and we urge its continued development and implementation in an expedited manner.

As you are aware, airborne weather avoidance radar represents an important aircraft system used by pilots to detect areas of hazardous weather. New aircraft are equipped with the latest state-of-the-art airborne weather avoidance radar technology. The color displays are easier to interpret than the older monochrome displays, and they provide an enhanced ability to measure the intensity of weather activity. Some units are also able to depict windshear and turbulence near convective activity.

Not all aircraft, however, have the newest technology weather avoidance radar. Some of the radar equipment in older airliners are more than 30 years old and air carriers are not always quick to retrofit older generation airplanes with the newest units.

Mr. Chairman, we need to ensure that pilots have weather detection and avoidance equipment that provides them with an accurate and timely means to interpret, evaluate and avoid all types of hazardous weather, rather than equipment that is just barely adequate.

But state-of-the-art weather detection equipment is useless unless the flight crew is trained in its use. In discussions with airline crews, we have learned that flight crew training among the nation's airline companies for airborne weather radar ranges from cursory to complete and comprehensive. The Safety Board is aware, from reviewing flight manuals of manufacturers and air carriers, that some manufacturers and air carriers provide little more than a drawing of the radar control panel in the aircraft operating manual with no guidance in how to operate or interpret the displayed information.

We not only need to ensure that pilots have the best airborne weather interpretive equipment available, we also need to ensure that flight crews have the necessary training to be able to get the most from that equipment. We are concerned with these problems, and the Safety Board's staff is currently evaluating information from previous accidents and incidents regarding airborne weather avoidance radar and associated training.

As mentioned earlier, we are currently investigating the accident that occurred June 1, 1999, in Little Rock, Arkansas, involving American Airlines flight 1420, an MD-82 from Dallas, Texas, to Little Rock. The aircraft crashed after landing at Little Rock, resulting in 11 fatalities, including the captain. At the time of the accident, there were heavy thunderstorms in the area of the airport. Although the investigation is ongoing, we can share the following preliminary information on the weather conditions with you.

    · A thunderstorm was in progress at the airport at the time of the accident. As you are aware, the National Weather Service provides six levels of weather echo intensity; Level 1 is a weak intensity with light to moderate turbulence, and Level 6 is extreme with possible severe turbulence. Level 6 was reported in the airport area at the time of the accident.

    · At the time of the accident, the NWS issued a Convective SIGMET advisory for severe thunderstorms, and a Severe Weather Forecast Alert was in effect for an area that included the airport, both of which the pilot received. A Severe Thunderstorm Warning to the public was issued by the NWS and was in effect for an area that included the Little Rock airport. This information is also not provided to the controllers or flight crew. The Severe Thunderstorm Warning is not an aviation product and is not typically provided to air traffic control or flight crews. We will be evaluating this issue as part of our investigation.

    · The airport did not have a TDWR or an ASR-9 with the ability to depict weather echoes and intensities. It did have an improved LLWAS that issued several alerts prior to the accident which the pilot did receive. The pilot also received updates on the winds during the final approach.

    · A Doppler weather radar (WSR-88D) operated by the NWS was located six nautical miles north-northwest of the airport and provided detailed and accurate information on the thunderstorms, including wind speeds, in the Little Rock area to NWS personnel. NWS personnel used this information to formulate and disseminate severe weather warnings to the public. However, this information was not available in real time to the flight crew, air traffic control personnel, or approach control. Safety Board investigators are looking into this issue as part of its investigation.

    · According to an interview with the first officer, the flight crew was using their airborne weather avoidance radar to display the location and intensity of the thunderstorms. The thunderstorms in the airport terminal area should have been displayed on the aircraft's radar as significant weather echoes indicating hazardous weather. This is an issue that is being looked into as part of the Board's investigation.

Because the Safety Board's investigation is on-going, no conclusions have been reached; however, there are a number of important questions that are being addressed, such as:

    · Why did the flight crew continue the approach and landing at Little Rock?

    · What additional weather information and training should flight crews have to augment their decision-making process?

    · What was the aircraft airborne avoidance weather radar showing, and how are flight crews trained to interpret and use the radar display?

    · What are the limitations of airborne weather avoidance radar in the terminal area and what improvements need to be made?

Two days after the Little Rock accident, on June 3, 1999, the Massachusetts Institute of Technology's Lincoln Laboratories issued a report sponsored by NASA's Ames Research Center entitled "An Assessment of Thunderstorm Penetrations and Deviations by Commercial Aircraft in the Terminal Area," focusing on Dallas-Fort Worth airspace. The report's findings are based on data from slightly more than 60 hours of convective weather. During that time there were nearly 2,000 airplane encounters with that type of weather.

The report indicates that almost two-thirds of the airplane encounters resulted in the airplane flying through the convective activity. Instead of deviating around storms in the airspace around an airport while approaching to land, pilots regularly penetrated storms with significant precipitation. Arriving aircraft were more likely to penetrate storms when they were following another aircraft, more than 15 minutes behind on their scheduled trip, or flying after dark. This information is disconcerting, as it suggests there is a tendency for air-carrier pilots to penetrate convective activity, similar to that at Little Rock, near the airport. Industry and the government must now develop and implement strategies to reduce these penetrations.

Mr. Chairman, technologies are available today that can accurately detect and warn of thunderstorm and convective hazards in the airport terminal area, and can prevent accidents related to these hazards. However, industry and government must develop the means to package, and to disseminate rapidly and economically, to flight crews, air traffic controllers, and dispatchers, the enormous amount of information the technologies provide, to help them make informed decisions. This information must be in a user-friendly format, and appropriate training must be developed and provided to the users of the information. Also, aircraft must be equipped with the latest airborne weather avoidance radar, and flight crews must be properly trained on the use of the radar. In addition, flight crews must reexamine their decision-making process, and airlines must reevaluate their procedures and training, regarding flight in and near significant weather echoes located in the airport terminal area.

The Safety Board will be considering all of these concerns in its investigation of the accident at Little Rock, evaluating what actions should be taken to address the concerns, and developing, as appropriate, recommendations for corrective action.

That completes my formal testimony Mr. Chairman. I would be pleased to respond to your questions.