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In March 1977, in what remains the world’s deadliest aviation accident, two passenger jumbo jets collided on a runway at Tenerife, Canary Islands, causing the deaths of 583 passengers and crew. In the U.S., the deadliest U.S. runway incursion accident occurred in August 2006 when Comair flight 5191, a regional jet, crashed after taking off from the wrong runway, killing 49 of the 50 people onboard. The worst U.S. runway incursion accident involving two aircraft was a collision between a USAir 737 and a Skywest Metroliner commuter airplane at Los Angeles International Airport in February 1991, which killed 34 people.
A recent runway incursion illustrates the danger of these situations. On September 19, 2008, a runway incursion involving a Mesa Airlines Canadair Regional Jet (CRJ)-700, and a Cessna R172K occurred at the Lehigh Valley International Airport in Allentown, Pennsylvania. There were 4 crewmembers and 56 passengers aboard the CRJ-700. The Cessna aircraft was on landing roll when the tower controller instructed the Mesa Airlines CRJ-700 to taxi into position and hold on the same runway. The controller instructed the Cessna pilot to exit the runway at taxiway A4 and then cleared the Mesa Airlines CRJ-700 for takeoff. During their takeoff roll, the Mesa Airlines crew heard the Cessna pilot say that he had missed the taxiway A4 turnoff and ask to exit at taxiway B. The CRJ-700 crew saw the Cessna ahead, aborted the takeoff at about 120 knots, and swerved around the Cessna. The Mesa Airlines crew estimated they missed colliding with the Cessna by 10 feet.
The runway incursion issue has been on the Safety Board’s Most Wanted List since its inception in 1990. In the late 1980s, an inordinate number of runway incursions/ground collision accidents resulted in substantial loss of life, and the Board issued numerous safety recommendations addressing the issue. The Federal Aviation Administration (FAA) has since taken action to inform controllers of potential runway incursions, improve airport markings, and install the Airport Movement Area Safety System (AMASS) and Airport Surface Detection Equipment Model X (ASDE-X). These systems are an improvement but are not sufficient as designed to prevent all runway incursions. The runway incursion rate in the United States has not appreciably changed over the past 4 years and stands at about 6.1 runway incursions per 1,000,000 tower operations, despite these improvements.
Information needs to be provided directly to flight crews as expeditiously as possible to prevent runway incursions. The issue is one of reaction time. Safety Board investigations have found that AMASS is not adequate to prevent serious runway collisions because too much time is lost routing valuable information through ATC. After an AMASS alert, the controller must determine the nature of the problem, determine the location, identify the aircraft involved, and determine what action to take. Only after all of these determinations have been made can appropriate warnings or instructions be issued. The flight crew must then respond to the situation and take action. Simulations of AMASS performance using data from actual incursions show that alerts may occur as little as 8 to 11 seconds before a potential collision. In recent incidents,(1) AMASS did not alert controllers in time to be effective, and the situations were instead resolved by flight crew actions that sometimes bordered on heroics or simple luck.
Until there is a system in place to positively control ground movements of all aircraft, with direct warning to pilots, the potential for this type of disaster will continue to be high.
ATC procedures should require specific clearances, rather than rely on implied clearances, for aircraft to cross runways. This requirement would reduce the chance of a runway incursion because pilots would have to obtain an explicit clearance before crossing any runway; without such a clearance, the pilot would be required to hold short. Further, if aircraft need to be cleared to cross multiple runways, controllers should issue an explicit crossing instruction for each runway after the previous runway has been crossed.
Implementation of the Safety Board’s recommendations will reduce the chances of a runway collision between two airplanes, and will also reduce the risk of a pilot mistakenly selecting an incorrect runway, as occurred in the August 27, 2006, Comair flight 5191 accident in Lexington, Kentucky. If the revisions recommended had been implemented before that accident, these procedures would have provided the flight crew with better awareness of the airplane’s position along the taxi route and would have required the controller to visually observe the airplane’s position and monitor the taxi as the airplane progressed toward the departure runway. In addition, research and analysis sponsored by the FAA has cited pilot and controller concerns about the adequacy of runway crossing requirements, and most of these pilots and controllers thought that it would be beneficial to adopt the procedures recommended. In addition, if a moving map display or an automatic system to warn pilots when taking off from the wrong runway were available, the pilots would likely have not made their catastrophic mistake.
Analysis performed by the Flight Safety Foundation has shown that runway excursions accounted for approximately 29 percent of all accidents involving turboprop and turbojet aircraft worldwide between 1995 and 2006.(2) A runway excursion occurs when an aircraft either overruns or undershoots a runway while landing or taking off. Existing FAA regulations do not specify either the type of arrival landing distance assessment that should be performed or a safety margin that should be applied. The FAA advocates a minimum safety margin of 15 percent for arrival landing distance assessments and a 15-percent factor is included in the European Aviation Safety Agency and Joint Airworthiness Authorities operational requirements for contaminated runway landing performance. The FAA has sought voluntary operator compliance with performing landing distance assessments and applying a 15-percent safety margin. However, runway overruns continue to occur in the United States when the flight crews have not performed a landing distance assessment before landing on a contaminated runway.
Summary of Action
For several years the FAA has been evaluating various technologies that can provide a direct warning to pilots of a runway incursion risk. One of the most promising of these technologies, Runway Status Lights (RWSLs), is a series of runway lights not unlike traffic lights that tell pilots whether or not runways are clear. The FAA performed an operational evaluation of an RWSL system at the Dallas/Ft. Worth airport that was been completed in June 2005 and showed promising results. RWSLs are currently being tested in San Diego and will be tested in Los Angeles soon. In July 2008, the FAA announced its plan to issue a contract to install RWSLs at 22 airports (including Dallas/Ft. Worth, San Diego, and Los Angeles) by 2011. Other technologies being evaluated by the FAA include a system called the Final Approach Runway Occupancy Signal (FAROS), which is being tested at the Long Beach/Daugherty Field Airport in California. FAROS activates a flashing light visible to landing pilots to warn them that the runway is occupied and hazardous. The FAA is also evaluating low-cost commercially available radar surveillance systems appropriate for medium and smaller airports. Two such systems using different technologies are currently being tested at Spokane, Washington; however, these systems do not provide a direct cockpit warning, but rely on voice communication between controllers and pilots.
In addition, the FAA sponsored an industry-government working group through RTCA Special Committee 186 to develop an Operational Safety Assessment (OSA) of surface alerting using Automatic Dependent Surveillance – Broadcast (ADS-B). The FAA believes that the OSA will lead to the development of a minimum operational performance specification for an ADS-B based surface alerting application that would provide a direct cockpit warning of a runway incursion risk.
The FAA is taking commendable actions, particularly in expanding the RWSL program to a number of airports. However, many of these systems are still being evaluated. In 2011, 11 years after the issuance of the recommendation for a direct warning to the cockpit, only 22 airports will have RWSLs installed. The FAA’s plans to develop standards for a system based on ADS-B to provide a direct cockpit warning are also commendable, although the FAA’s proposed requirements for ADS-B do not include a requirement for ADS-B In (3), which will be necessary for such a system.
The FAA announced that it will provide funding for users who agree to equip their aircraft with an Electronic Flight Bag, which includes Moving Map Displays, or an aural runway alerting system. The FAA’s program to encourage users to equip their aircraft with moving map displays is commendable, but it is not a requirement, and the program is limited to no more than $5 million. As a result, the program is not likely to result in widespread adoption of moving map technology. FAA standards for this equipment, as well as commercial products and installations, are already available.
The FAA held a “Call to Action” on August 15, 2007, where key aviation industry representatives met for 1 day to discuss short- and long-term measures to improve the safety of airport operations. The participants identified the issue of taxi clearances as an area in need of improvement, and the FAA is conducting a review of taxi clearance policies. The FAA has completed a safety risk analysis, is reviewing a resulting safety risk management plan, and is considering what changes, if any, need to be made. Eight years after the Safety Board issued recommendations concerning taxi clearance procedures, and more than a year after the Call to Action meeting, where these issues were identified as critical safety concerns, the FAA has neither taken the actions recommended nor indicated to the Safety Board any plans to do so.
The FAA developed a voluntary guidance document for performing landing distance assessments with a 15-percent safety margin. The FAA surveyed 14 Code of Federal Regulations Part 121 operators and found that 92 percent of U.S. airline passengers are now being carried by air carriers in full or partial compliance with the practices recommended. The FAA is forming an aviation rulemaking committee (ARC) to review regulations affecting certification and operation of airplanes and airports for airplane takeoff and landing operations on contaminated runways. However, within the past year, the Safety Board completed two investigations of runway overrun accidents for which landing distance assessments had not been conducted. (4) Based on these recent accidents, it appears that the FAA’s guidance has not been effective.
Actions Remaining
Implement a safety system for ground movement that will ensure the safe movement of airplanes on the ground and provide direct warning capability to the flight crews. Implement ATC procedures requiring an explicit clearance for each runway crossing. Require operators to install cockpit moving map displays or an automatic system that alerts pilots when a takeoff is attempted on a taxiway or a runway other than the one intended. Require operators to conduct arrival landing distance assessments before every landing based on existing performance data, actual conditions, and incorporating a minimum safety margin of 15 percent.
Safety Recommendations
A-00-66 (FAA)
Issued July 6, 2000
Added to the Most Wanted List: 2001
Status: Open—Unacceptable Response
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. (Source: Recommendation letter to the FAA regarding runway incursions, July 6, 2000.)
A-00-67 (FAA)
Issued July 6, 2000
Added to the Most Wanted List: 2007
Status: Open—Unacceptable Response
Amend 14 Code of Federal Regulations (CFR) Section 91.129(I) to require that all runway crossings be authorized only by specific air traffic control clearance, and ensure that U.S. pilots, U.S. personnel assigned to move aircraft, and pilots operating under 14 CFR Part 129 receive adequate notification of the change. (Source: Recommendation letter to the FAA regarding runway incursions, July 6, 2000.)
A-00-68 (FAA)
Issued July 6, 2000
Added to the Most Wanted List: 2007
Status: Open—Unacceptable Response
Amend FAA Order 7110.65, “Air Traffic Control,” to 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. (Source: (Source: Recommendation letter to the FAA regarding runway incursions, July 6, 2000.)
A-07-45 (FAA)
Issued August 28, 2007
Added to the Most Wanted List: 2008
Status: Open—Acceptable Response
Require that all 14 Code of Federal Regulations Part 91K, 121, and 135 operators install on their aircraft cockpit moving map displays or an automatic system that alerts pilots when a takeoff is attempted on a taxiway or a runway other than the one intended. (Source: Attempted Takeoff From Wrong Runway Comair Flight 5191 Bombardier CL-600-2B19, N431CA Lexington, Kentucky August 27, 2006. [NTSB/AAR-07-05])
A-07-57 (FAA) (Urgent)
Issued October 2, 2007 (Superseded A-06-16)
Added to the Most Wanted List: 2007
Status: Open—Unacceptable Response
Immediately require all 14 Code of Federal Regulations Part 121, 135, and 91 subpart K operators to conduct arrival landing distance assessments before every landing based on existing performance data, actual conditions, and incorporating a minimum safety margin of 15 percent. (Source: Runway Overrun and Collision Southwest Airlines Flight 1248 Boeing 737-74H, N471WN Midway Airport Chicago, Illinois, December 8, 2005. [NTSB/AAR-07-06])
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