Testimony of Carol Carmody
Acting Chairman, National Transportation Safety Board
before the Committee on Transportation and Infrastructure
Subcommittee on Aviation
House of Representatives
Regarding Runway Incursions
June 26, 2001

Good morning, Chairman Mica and members of the Committee. I am glad to be here representing the National Transportation Safety Board (NTSB) before you today to provide testimony on runway safety and anti-blocking radios.

As demonstrated by last summer's flight cancellations, the continued growth of commercial aviation and the general aviation fleet increasingly strain the U.S aviation system infrastructure. This growth is challenging the Federal Aviation Administration's (FAA) air traffic control (ATC) system, and requires additional oversight and vigilance to ensure the safety of the aviation system.

According to the FAA, the number of air travelers will increase from 604 million in 2000, to more than 926 million by 2012. In addition, the FAA projects that aircraft operations at air route traffic control centers will increase from 46 million in 2000, to about 63 million in 2012. The number of passengers on foreign flag air carriers traveling to or from the United States is also expected to increase from approximately 139 million in 2000, to 267 million by 2012.

This increase in traffic highlights the potential for more incidents or accidents on runways. Federal Aviation Administration data show there were 431 runway incursions in the United States last year, more than twice the 200 incursions that occurred in 1994, and a significant increase from the 322 incursions in 1999. In 2000, the rate of runway incursions per 100,000 operations was .64, up from .46 in 1999. Through June 10 of this year, 178 runway incursions were reported - 4 more than during the same period in 2000.

The following eight incidents are runway incursions that occurred since February 2000 in which we have reviewed information:

  1. February 2000 -- At Detroit, Michigan, the crew of a Northwest DC-10 on final approach initiated a go-around maneuver to avoid a Northwest A320 cleared for takeoff. The airplanes missed each other by 300 feet vertical and .44 miles horizontal.
  2. March 2000 -- At Sarasota, Florida, the tower air traffic controller cleared a Cessna airplane onto the runway in front of another Cessna airplane that had been cleared for takeoff, resulting in a collision and the loss of four lives. In our final report, we cited failures in air traffic control procedures as causal and contributing factors.
  3. May 2000 -- At Chicago's Midway Airport, an American Trans Air Boeing 727 was on final approach when the flight crew initiated a go-around maneuver shortly before landing to avoid a Rockwell Aero Commander that was holding on the runway awaiting takeoff clearance. The Boeing 727 passed about 60 feet over the other aircraft.
  4. May 2000 -- At Chicago's Midway Airport, a Cessna Citation business jet was holding in position on a runway awaiting takeoff clearance when the tower controller cleared a Beech King Air to land on the same runway. Distracted with other duties, the controller failed to resolve the conflict until the King Air crossed the airport boundary. The controller instructed the King Air pilot to go around, but not in time to avoid overflying the Citation. The aircraft missed each other by an estimated 400 feet.
  5. December 2000 -- At Providence, Rhode Island, the flight crew of a US Airways A320 aborted its takeoff because the front of a Southwest Boeing 737 was protruding over the hold short line on the active runway. The US Airways airplane was traveling at approximately 30 to 70 knots when it passed in front of the Southwest airplane. Because the visibility was 1/4 mile with fog and blowing snow, the tower could not see the area of the incursion. The tower was not equipped with a ground radar system or other type of ground movement safety system.
  6. January 2001 -- At Seattle-Tacoma International Airport, a TWA MD-80 flew over an American Airlines MD-80, missing it by an estimated 60 feet. The tower local controller had cleared the TWA aircraft for takeoff from runway 16L and instructed the American Airlines airplane to hold short of the runway. However, the flight crew misunderstood the controller and crossed 16L. Visibility at the time of the incident was 1/4 mile with fog.
  7. March 2001 -- At Fort Lauderdale International Airport, Florida, a Delta Air Lines Boeing 767 flew over a US Airways Boeing 737, missing it by less than 100 feet. The Delta airplane was cleared to land on runway 27R while on 5-mile final approach, and the US Airways airplane was cleared to taxi into position and hold on runway 27R. At the time of the incident, the tower controller was distracted by other duties and failed to advise the Delta flight crew of the US Airways airplane's departure from runway 27R or to advise the US Airways flight crew of the Delta airplane's arrival, as required by FAA procedures.
  8. May 2001 - At Dallas/Fort Worth International Airport, Texas, an American Airlines Fokker 100 missed colliding with an Amflight metroliner by approximately 100 feet. The controller instructed the Amflight airplane to cross runway 18L and turn onto a taxiway. The pilot crossed the runway, then turned back on to the runway in front of the departing American flight.

The Safety Board is also assisting in the investigation of an October 2000, accident in which 81 people died when a Singapore Airlines Boeing 747 struck a concrete barrier and hit a construction site as it mistakenly took off from a closed runway at Taipei's Chiang Kai-shek International Airport, Taiwan.

Fortunately, there have been few actual collisions and the number of fatalities has been small. Although 75 percent of runway incursions this calendar year have involved small general aviation aircraft, many of the factors involved could affect air carrier airplanes, and the potential for a catastrophic accident only increases with time if the rate of errors is not reduced.

In 1991, the NTSB recommended that the FAA expedite efforts to fund the development and implementation of an operational system analogous to the airborne conflict alert system to alert controllers to pending runway incursions at all terminal facilities that are scheduled to receive airport surface detection equipment (A-91-29). In March 2000, nine years after the recommendation was made, the Board changed its status from "Open-Acceptable" to "Open-Unacceptable" action because the Board does not believe that AMASS as currently designed meets the safety goals of the original system promised by the FAA. AMASS does not appear to be able to provide sufficient warning time to prevent some runway collisions and does not provide direct warnings to flight crews and other vehicle operators.

The runway incursion issue has remained on the Board's "Most Wanted" list since its inception in 1990. This list highlights issues the Board believes have the most potential to improve safety, save lives, and reduce accidents and injuries.

Since 1973, the Safety Board has issued over 100 safety recommendations regarding runway incursion issues. On July 6, 2000, following a special Board meeting, the Safety Board issued six additional safety recommendations to the FAA regarding this matter, and information regarding those recommendations is provided below. You will note that three of the six recommendations are in an unacceptable status.

  1. Require, at all airports with scheduled passenger service, a ground movement safety system that will prevent runway incursions; the system should provide a direct warning capability to flight crews. In addition, demonstrate through computer simulations or other means that the system will, in fact, prevent incursions (A-00-66);
  2. Require that all runway crossings be authorized only by specific air traffic control clearance (A-00-67);
  3. Require that when aircraft need to cross multiple runways, air traffic controllers issue an explicit crossing instruction for each runway after the previous runway has been crossed (A-00-68);
  4. Discontinue the practice of allowing departing aircraft to hold on active runways at nighttime or any time when ceiling and visibility conditions preclude arriving aircraft from seeing traffic on the runway in time to initiate a safe go-around maneuver (A-00-69) (in an unacceptable status);
  5. Adopt the landing clearance procedure recommended by International Civil Aviation Organization (ICAO) Document 4444-RAC/501 (A-00-70) (in an unacceptable status); and
  6. Require the use of standard ICAO phraseology for airport surface operations and periodically emphasize to controllers the need to use this phraseology and to speak at reasonable rates when communicating with all flight crews, especially those whose primary language is not English (A-00-71) (in an unacceptable status).

Although the FAA has taken numerous actions in response to Safety Board recommendations, as well other runway incursion-related recommendations made by the Department of Transportation's Inspector General and others, it is disconcerting that the number of runway incursions has not diminished. The Safety Board remains concerned that FAA's efforts to address runway incursions through technological development falls short of what is needed, and believes some operational measures - as recommended - should be taken.

In 1991, the FAA stated that the cornerstone of its runway incursion efforts was the development and implementation of the Airport Movement Area Safety System, or AMASS. AMASS works by generating an audible and visual alert to controllers when an aircraft or vehicle is occupying a runway and an arriving aircraft is 1/2 to 3/4 mile from the runway threshold or a departing aircraft on the runway is detected by the system and is moving at approximately 80 feet per second or 47 knots. The visual and audible alert parameters were not based on human performance studies, but were empirically determined based on tests conducted with a prototype AMASS system.

Following the investigation of an incident that occurred at O'Hare International Airport in 1999, the NTSB asked the FAA to conduct a simulation of AMASS performance using data from several runway incursion incidents investigated by the Safety Board. The simulations showed that AMASS would not have generated warnings in sufficient time for controllers and flight crews to respond effectively and prevent the incidents. Following the simulation, the FAA modified its position in 1999 and stated that AMASS would not prevent runway incursions but, rather, runway collisions. Incidentally, of the eight incidents I mentioned earlier, half would not have been prevented by AMASS.

Since the FAA awarded its AMASS development contract in September 1990, there has been one delay after another. For example:

The FAA has also stated that AMASS is expected to be operational at 32 of the nation's busiest airports by 2003. The Safety Board remains concerned, judging by past schedule revisions, that even this schedule will not be met. The Board also believes that current AMASS parameters may not provide controllers and flight crews sufficient time to intervene and react to maintain safe separation in all circumstances. We believe that a key element that is missing is to provide a direct warning to flight crews or vehicle operators. Therefore, we question the viability of AMASS to prevent runway collisions under various conditions, and believe the FAA should conduct additional simulations of AMASS's performance to test its ability to provide effective alerts under real-world conditions.

In October 1993, the FAA reported that it was evaluating several different technologies for managing airport surface movements, including differential global positioning systems, loop and magnetic sensors, and marine X-band radar systems, in lieu of installing full airport surface detection equipment, also known as ASDE, at lower-activity airports. On March 23, 1998, the FAA stated that it was continuing research and development of low-cost ASDE alternatives, including evaluation of marine X-band radar and phased-array radar systems. In addition, the FAA is collaborating with the National Aeronautics and Space Administration (NASA) to test and demonstrate an integrated surface movement management system. Safety Board staff have been briefed by NASA on its work on heads-up displays and moving map displays that would provide aircraft movement information directly to pilots. The initial demonstrations for these technologies have indicated that they provide real time position to flight crews and may prevent incursions by improving the situational awareness of both pilots and controllers. These technologies appear to offer reliable accurate traffic information directly to flight crews much faster than transmitting ground-based alerts to aircraft.

The FAA advised the Board that on November 22, 2000, it awarded the ASDE-X contract to Sensis Corporation, and that an operational readiness demonstration was scheduled for April 2003. Informal discussions with the FAA indicate that the ASDE-X system, as currently designed, will provide aircraft identification to air traffic controllers. It does not, however, provide any conflict alert information, nor does it provide information to pilots or vehicle operators. Future design changes would incorporate AMASS conflict alert logic into the ASDE-X system. As the FAA has so far been unable to implement comprehensive conflict logic in AMASS, the Safety Board is concerned that the same technical problems may affect ASDE-X.

Mr. Chairman, in 1993, FAA estimated that AMASS would cost $59.8 million and be installed in 1996. The Department of Transportation's Inspector General reported in March 2000, that costs were then estimated to reach $151.8 million, a $92 million increase. We can only assume that this figure is higher today. Board staff has also been advised that the cost of the ASDE-X systems has increased from an initial projection of $100,000 to approximately $4.6 million due to operational requirements.

It has been nearly 10 years since the Board issued its recommendation that the FAA expedite efforts to fund the development and implementation of an operational system to alert controllers to pending runway incursions at all terminal facilities that are scheduled to receive airport surface detection equipment. Ten years later, only two AMASS systems have been commissioned for full operational use at airports in the United States. Despite many years of research and development and the expenditure of over $150 million, the FAA has been unable to procure ground movement safety systems suitable for use at airports to prevent runway incursions. In February 2001, the FAA awarded five contracts for new surface technology; however, none of them will provide information directly to flight crews as the Safety Board has recommended. The FAA needs to establish criteria for installation of airport ground movement safety systems and commit to a specific date for completion of the acquisition and delivery of these systems.

In October 1999, the FAA established a National Runway Safety Program to identify the potential severity of an incursion and reduce the likelihood of incursions through training, technology, communications, procedures, airport signs/marking/lighting, data analysis and developing local solutions. The FAA's initiatives include:

As I mentioned earlier, since the technology was not mature, in July 2000, the Safety Board issued recommendations aimed at changing air traffic control procedures and phraseology. Three of those recommendations were initially rejected by the FAA, and none have been implemented. Technological advances may help accomplish some of the FAA's goals, but there is no single solution that encompasses all situations. Awareness and education are important, but in a system as complex as airport traffic control, human mistakes are unavoidable. That is why many of the Board's recommendations over the years have focused on building in essential redundancies and avoiding the use of procedures that leave the ATC system vulnerable to inevitable lapses in human performance.

In June 2000, the FAA held a Runway Incursion Summit at which 10 recommendations were adopted. The criteria for the development and adoption of the recommendations were that they have the greatest impact on the reduction of runway incursions, and that they be able to be completed by December 2000. The status of the recommendations adopted and their subject matters are provided in Attachment A.

Although none of the recommendations were completed within the planned timeframe, we urge the FAA to continue to explore methods to make certain that the air traffic environment is robust and able to minimize the impact of human mistakes before they result in an accident or incident.


The Committee also asked that the Board discuss anti-blocking radios. Clear and complete radio communications are necessary for adequate separation of aircraft and to ensure that aircraft are receiving and following ATC guidance. A known hazard to effective communications is incomplete, partial, or blocked radio communications when two persons inadvertently talk on the frequency at the same time or in the event of a stuck microphone key.

Although the Safety Board has not investigated a major domestic accident in which blocked or "stepped-on" communications was a factor, we have participated in the investigations of two foreign accidents where blocked communications was a factor. Those accidents were the 1976 collision of two Boeing 747s at Tenerife, and the 1989 controlled flight into terrain of a Boeing 707 in the Azores. We believe reports of blocked communications from air traffic controllers and pilots indicate that the potential safety implications are real and need to be addressed.

On July 20, 1993, the FAA issued a Technical Standard Order (TSO), TSO-C128, for "Devices that Prevent Blocked Channels Used in Two-way Radio Communications Due to Unintentional Transmissions," and on April 11, 1994, issued TSO-C122 for "Devices the Prevent Blocked Channels Used in Two-way Radio Communications Due to Simultaneous Transmissions." Compliance with these two TSOs, however, was voluntary and the aviation community did not respond.

The Safety Board staff has been informed that the FAA is considering publishing a notice of proposed rulemaking that would establish the requirements for anti-blocking technology. This effort appears to be on hold pending sufficient staff resources and the completion of other higher priority projects.

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



  1. Enhanced Operational Tower Controller Training -- scheduled for completion during the first quarter of FY 02;
  2. Foreign Air Carrier Pilot Training, Education, and Awareness -- scheduled for completion by the end of the 4th quarter of FY 01;
  3. Advisory Circular for Airport Surface Operations -- under final review (was supposed to be completed last month);
  4. Airport Markings -- (the painting of wide hold short lines) -- has not been accomplished at most airports;
  5. Education, Training and Awareness for Pilots, Controllers, and Vehicle Operators -- expected to be completed the end of this month;
  6. Memory Enhancement Techniques for Tower Controllers -- expected to be completed by the 4th quarter of FY 01;
  7. Pilot/Controller Communications Phraseology Review -- expected to be completed by the end of the first quarter of FY 02;
  8. Improved Pilot Evaluation and Testing -- expected to be completed by the end of this month;
  9. Air Traffic Teamwork Enhancement Training for Tower Controllers -- completed in May 2001; and
  10. Technology Assessment -- on-going.

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