Landmark Accidents: Chain Reaction

Collision on 30R at St. Louis

August 1, 2000

To learn more about safe aircraft ground operations, take the AOPA Air Safety Foundation's interactive online Runway Safety Program.

Runway safety and ground operations continue to be a high-visibility issue for the FAA and the pilot community. How hard could it be to operate an aircraft on the ground? Turns out that it can be as complex as many flight operations and for a small percentage of pilots and their passengers, a mistake can be fatal.

The statistics in the accompanying article (" Examining the Causes," p. 76) will provide an overview of the problem and information about what the AOPA Air Safety Foundation is doing to help. We'll review an accident that helped bring runway safety to the forefront of industry consciousness. In this case, a professional charter pilot didn't realize that he was on the wrong runway. Neither did the controller. Airport design and operations issues contributed to the confusion.

On November 22, 1994, at 2203 (10:03 p.m.) Central Standard Time (CST), Trans World Airlines (TWA) Flight 427, a McDonnell Douglas MD-80 series jet, collided with a Cessna 441 Conquest II at the intersection of Runway 30R and Taxiway Romeo at Lambert-St. Louis International Airport.

The Conquest, with one passenger and a private pilot observer on a charter flight from Iron Mountain, Michigan, landed on Runway 30R at St. Louis uneventfully at around 2140. The pilot was Part 135-qualified with nearly 8,000 hours of flight time, including more than 2,000 hours in the Conquest alone. The Conquest dropped off the passenger at Midcoast Aviation, where the pilot and observer prepared for the return flight. Midcoast personnel reported that they appeared to be in a pleasant mood but seemed eager to return home.

At 2158, the Conquest pilot advised ground control that he was ready to taxi. The ground controller issued taxi instructions to "Back-taxi into position, hold Runway Three-One; let me know on this frequency when you're ready for departure." The pilot acknowledged by stating "Kilo Mike." Although not formally defined at the time of the accident, a clearance to "back-taxi" on an active run-way means to use that runway to taxi in a direction opposite to departing or landing traffic to reach the takeoff position.

The MD-82 ground operations were routine. The crew received instructions to taxi to Runway 30R for departure. At 2201:23, the local controller cleared the MD-82 for takeoff on Runway 30R, with instructions to fly a heading of 335 degrees. The first officer confirmed the assigned heading, and the airplane taxied onto Runway 30R. At 2202:29, the Conquest pilot advised the local controller, "Kilo Mike's ready to go on the right side." The controller responded, "Roger, I can't roll you simultaneously with the, uh, traffic departing from the right. Just continue holding in position. I'll have something for you in just a second."

As the MD-82 began its takeoff roll, the first officer operated the flight controls while the captain advanced and set the throttles. About three seconds after reaching 80 knots, an additional crewmember in the cockpit jump seat yelled, "There's an airplane!"

The captain and first officer reported that they both saw the Conquest on the runway at the same instant. Both pilots applied the brakes, and the captain used left rudder in an attempt to steer the MD-82 around the Conquest. Approximately two seconds later, the right wing of the jet sliced through the top of the 441's fuselage. The jet crew maintained directional control and brought it to a stop. The MD-82 sustained substantial damage during the collision, but there were no serious injuries. The Conquest was destroyed. Both the pilot and pilot observer were killed.

The crew on the MD-82 stated that they did not observe the Conquest or its position lights at any point during their takeoff roll and only saw the Conquest when the lights from the MD-82 illuminated it. In accordance with TWA's normal procedure, the MD-82 had all external lights on during the takeoff roll. The investigation concluded that the Conquest probably did not have its strobe lights on before the accident. It is believed that the pilot turned on the wing-mounted landing lights only a few seconds before impact as he received takeoff clearance. It was too late for either the tower or the TWA crew to identify the aircraft on the runway and prevent the collision.

Weather was not a factor, with clear skies and unlimited visibility. The ground controller was working four positions at the time of the accident, each of which is normally staffed with a separate controller during periods of peak traffic. However, the NTSB did not consider that to be a factor in the accident. Tower controllers indicated that traffic was moderate at the time of the accident.

Expectation frequently plays a large part in accident chains. Pilots expect to hear a particular clearance and sometimes do not notice when changes occur. The NTSB, in reconstructing the scenario, felt it was unlikely that the pilot was lost; instead it seemed that he had the preconception that he would be departing Runway 30R. The Conquest had just landed on 30R, and all other traffic was using runways 30R and 30L.

Airport factors

In 1986, because of increased traffic activity and consequent delays, the St. Louis airport authority temporarily designated taxiway Foxtrot as Runway 13/31, which was to be used only for departures by regional airline and GA aircraft. Despite the landing prohibition, a 1,838-foot displaced threshold was incorporated into the Runway 31 marking scheme. The trial program was successful at reducing delays, and in 1988 the conversion became permanent with the signage, surface markings, and lighting for day and night use.

In 1991, three air-carrier aircraft mistook Runway 13 for Runway 12L. To avoid confusion, the Runway 13/31 edge lights were set to a lower intensity setting than that of the Runway 12L/30R edge lights. The Runway 13/31 lights were turned up to high intensity for a departing aircraft on its takeoff roll and dimmed as soon as the aircraft was airborne. The dimmed lights on Runway 31 apparently did not distract the pilot from his misconception that Runway 30R was his departure runway.

On the night of the accident, the ATIS listed the active runways as 30R and 30L. Runway 31 was not identified, since it was only used for occasional departures and controllers did not treat it as an active runway. On the Conquest's inbound flight, the taxi clearance to the ramp did not include a clearance to cross Runway 31. The Safety Board believed that if it had been referenced as a runway for occasional general aviation departures on the ATIS broadcast, the pilot may have noted the proper runway in his taxi clearance.

Another cue that made it easy to overlook Runway 31 was its proximity to the Midcoast ramp on Taxiway Whiskey. Unlike the typical airport layout in which a ramp exit leads to a parallel taxiway, Runway 31, when not being used as a taxiway, was adjacent to the ramp exit. Several local pilots acknowledged that closeness to the Midcoast ramp created confusion.

The Conquest pilot had an airport diagram available in the cockpit. However, believing that the taxi route to Runway 30R was obvious, he may not have used the diagram. Dim lighting in the cockpit and the competing tasks of taxiing and performing checklists increased the distraction factor.

Runway 31 had markings, signage, and lighting consistent with FAA airport certification requirements. However, it was only 75 feet wide and looked like a taxiway. In contrast, runways 30R and 30L were 150 and 200 feet wide, respectively. At the exit of the Midcoast ramp, there were three signs indicating Runway 31 on the left side of the entrance to Taxiway Whiskey. The farthest sign was installed in compliance with the FAA's revised signage requirements but was not yet in full service and was not lit. Behind this sign and slightly to its left was the in-service hold-position sign. To the right of the two hold-position signs was a wooden sign that read: "Active Runway Contact Ground 121.9." The hold-position signs for Runway 13/31 were not lit the night of the accident, but they were clearly visible in the ambient light from the Midcoast ramp floodlights.

Following the accident, the airport installed taxi-holding position "wig-wag" lights at Taxiway Whiskey to enhance the presence of Runway 13/31 for aircraft exiting the Midcoast ramp. The displaced threshold on Runway 31 was removed.

The control tower was located about one and one-quarter miles from the collision site. Controllers stated that the Conquest was visible while it was on the ramp but disappeared after leaving the lighted area.

The Conquest pilot entered Runway 30R from Taxiway Romeo, some 2,500 feet from the threshold. The pilot should not have entered the runway at an intersection without specific clearance to do so. Since the pilot expected Runway 30R, the fact that he was not entering at the end of the runway was a subtle point.

Effective radio communications between the Conquest pilot and ATC were critical to establishing a mutual understanding. The ground controller's multiple frequencies were congested with almost continuous communication, which resulted in several simultaneous transmissions in the 20 minutes before the accident. Additionally, there was some indication that the Conquest pilot might have experienced communication radio difficulty. Specifically, the pilot complained about his communication radios during the inbound flight to St. Louis, and several subsequent transmissions were garbled. The Cessna pilot did not state the departure runway in any of his clearance readbacks. Had the proper readback procedure been followed, the controller would have had an opportunity to correct the problem early on. The Conquest pilot's final request to the local controller that "Kilo Mike's ready to go on the right side" also failed to provide the controller with another opportunity to catch the error. The proper phraseology should have been, "Conquest Kilo Mike holding in position Runway three-zero- right at Romeo, ready for departure." This would have alerted the controller — and possibly the TWA crew — that a collision was imminent.

Airport surface detection equipment (ASDE-3 ground radar) was installed and undergoing testing. It was in out-of-test-service mode on the night of the accident because of hardware failure. The NTSB felt that controllers would have had a higher probability of spotting the Conquest sitting on the runway for nearly three minutes if the ASDE had been operational. AMASS (airport movement area safety system) has become a controversial program because of extensive delays, technical and human factors issues, and resulting cost overruns. AMASS supplements ASDE by using a computer to spot conflicts between vehicles or aircraft entering runways and provides an alert to controllers who then radio the vehicle or aircraft involved. Had AMASS been operational, it too would have provided a warning.

Many subtle cues were missed, and some became evident only in retrospect. The pilot expected to depart from the runway on which he had landed only minutes before. The assigned departure runway looked like a taxiway, and the pilot never read back the clearance to give the controller a chance to catch the pilot's mistake. He failed to use strobe or landing lights while holding in position to increase the aircraft's visibility, although they may have been activated just before impact. Complacency, darkness, perhaps a touch of fatigue, and a nonstandard airport configuration completed the links in this accident chain.


Links to more information about runway incursions are available on AOPA Online. See also the index of "Safety Pilot" articles, organized by subject. Bruce Landsberg is executive director of the AOPA Air Safety Foundation.


Examining the causes

GA causing disproportionate share

BY JOHN STEUERNAGLE

The AOPA Air Safety Foundation reviewed one year's worth of pilot surface deviations — 490 incidents from September 1998 to August 1999 — to analyze the nature of the pilot contribution to the problem. Some of our findings may be surprising:

  • 61.8 percent of pilot surface deviations resulted from taxi operations.
  • 12.7 percent involved taking off without clearance; 10.8 percent landing without clearance.
  • 9.6 percent involved landing on the wrong runway or at the wrong airport.
  • General aviation operations accounted for 68.8 percent of deviations. The rest are attributable to professional air carrier or charter operations.
  • Most deviations occurred during day/VFR operations. (The vast majority of runway incursion accidents occur at night or in IMC.)
  • In more than half of the cases (52.6 percent), deviating pilots were not following ATC instructions.
  • 17.3 percent reported pilot distractions.
  • 11.8 percent were disoriented or lost.
  • Private pilots were responsible for 33 percent of the deviations studied. Because they account for 40.1 percent of the pilot population, private pilots were underrepresented in this sample.
  • Airline transport pilots (ATPs) represent 21.2 percent of the population, yet they were overrepresented with 30.1 percent of the deviations. Since they fly more frequently, they also have greater exposure.
  • Commercial pilots had 24.3 percent and certificated flight instructors had 15.2 percent, respectively, while student pilots had 7.9 percent of the deviations.
  • 22 percent of the deviating pilots had fewer than 300 hours of flight experience; 18 percent had more than 10,000 hours.

Clearly, surface deviations are not confined to one certificate or experience level. Confusion and lack of knowledge certainly account for some deviation incidents, but complacency seems to be equally represented.

Few runway incursions or pilot deviations result in aircraft accidents. Usually the system of checks and balances practiced by pilots and controllers ensures that at least one party to a potential collision becomes aware of the developing situation and stops the accident chain. All runway incursion accidents to date in the United States have included at least one of the following factors: night, poor visibility, or ATC operational error.

Airport Ground Operations. Airport runways and taxiways are marked with signs, lights, and surface paint according to FAA standards. Each intersection of runways or of runway and taxiway is a potential incursion location. Consider these four major issues.

  • Is the intersection clearly marked? Each intersection will be marked with at least lighted signs and pavement paint that extends across the intersection. Visibility of these markings, particularly the painted lines, varies considerably.
  • Are the pilot and controller aware of which aircraft is at which intersection? Disoriented or lost pilots may not realize which intersection they are approaching. Disorientation is more likely when pilots don't have a current airport diagram that clearly depicts all taxiways and runways.
  • Is the pilot cleared to enter the runway at this intersection? Federal Aviation Regulation 91.129(i) states in part, "A clearance to 'taxi to' the takeoff runway assigned to the aircraft is not a clearance to cross that assigned takeoff runway, or to taxi on that runway at any point, but is a clearance to cross other runways that intersect the taxi route to that assigned takeoff runway." This means that sometimes pilots must hold for further clearance at a given intersection and at other times may taxi across with no further clearance. This regulation contributes to confusion and in ASF's opinion should be changed to exercise positive control.
  • Are controllers certain about which aircraft they are clearing onto a runway? Confusion as to which aircraft is being cleared has led to deviations, incursions, and at least one accident. Preliminary accident data indicate that a fatal accident at Sarasota, Florida, this spring resulted from controller confusion and failure of a pilot to verify that the runway was clear prior to entering.

Entering a runway when you're not supposed to be there is the aeronautical equivalent of running a stop sign. Most of the time there is no collision, but the potential is always there. Runways are dangerous places. Do not cross or line up on one unless you have clearance to be there and have visually verified that there is no conflicting traffic either upfield or downfield.

Caution is equally important at nontowered airports. A major collision occurred between a regional airliner and a Beech King Air flown by a professional pilot who failed to exercise basic airmanship skills (see " Safety Pilot: Collision at Quincy," December 1997 Pilot). Courtesy and following proper procedure at nontowered airports will prevent these tragedies.

What we are doing. AOPA and the AOPA Air Safety Foundation are engaged in a multifaceted program to reduce runway incursions and incidents. Program initiatives include:

  • Airport taxi diagrams. ASF in collaboration with the FAA has made current FAA towered airport diagrams available to all pilots through ASF's Web site.
  • Operations at Towered Airports Safety Advisor . One of a series of pilot safety advisors produced by ASF. It addresses all aspects of operating to, from, and on towered airports and includes a runway incursion prevention message.
  • Operations at Towered Airports video. Addresses all aspects of towered airport operations and includes a re-creation of a runway incursion incident.
  • Operations at Towered Airports video, Long Beach version. The City of Long Beach, California, provided funding for production and distribution of a Long Beach-specific version of the Operations at Towered Airports video. This version has been distributed free of charge to more than 2,000 pilots.
  • "Operations at Towered Airports" seminars. Together with the FAA Aviation Safety Program, ASF has presented many free interactive pilot training seminars on towered airport operations. A professional ASF aviation educator, assisted by local ATC personnel, runs the seminars.
  • Runway Incursion "Hot Spots" video. Produced with funding from the city of Long Beach, California, this short video depicts specific runway incursion problem areas at Long Beach airport. Runway incursion prevention strategies and procedures are also discussed. The video is distributed free of charge by Long Beach airport. ASF is offering similar video production services to other towered airports.
  • Operations at Nontowered Airports Safety Advisor . Comprehensive guide to procedures and techniques for proper operations at airports without control towers — available online or in print.
  • Safety posters were distributed to more than 5,000 flight schools and FBOs.

Recommendations.

  • Change FAR 91.129(i) to require positive clearance to cross or taxi on any runway.
  • Ensure that each runway intersection is clearly marked for day and night operations. This includes readily discernable paint markings and possibly some form of special lighting.
  • Make airport diagrams available to all pilots and encourage their use.
  • Encourage GPS developers and database providers to include airport diagrams on in-cockpit map displays.
  • Continue pilot education initiatives. Flight instructors, designated examiners, and flight schools should emphasize ground operations for both towered and nontowered airports in certificate training and during flight reviews.


John Steuernagle is vice president of operations for the AOPA Air Safety Foundation.