Stormy night approach into LIT was ‘a can of worms’

 - May 23, 2008, 6:45 AM

Once again, the deadly duo of “get-there-itis” and fatigue joined forces to seduce an airline crew into attempting a landing at Little Rock National Airport (LIT) as a line of severe thunderstorms was passing through the area on June 1, 1999.

“Aw, we’re going right into this,” said the American Airlines captain as Flight 1420 turned onto base for Runway 4R just before midnight. Later, as the MD-82 encountered decreasing visibility, heavy rains and increasing crosswinds, he conceded, “This is a can of worms.”

The twinjet touched down 2,000 ft past the threshold of the 7,200-ft runway and skidded off the end, where it struck several tubes extending outward from the left edge of the ILS localizer array 411 ft beyond the end of the runway, passed through a chain-link security fence, went down a rock embankment to a flood plain about 15 ft below the runway elevation and hit the structure supporting the Runway 22L approach lights.

Among the findings of the NTSB was that the flight crew did not arm the automatic spoiler system before landing or manually deploy the spoilers after touching down. The investigators determined that during the landing rollout, the thrust reversers deployed, but both engine pressure ratios exceeded the maximum reverse setting several times, causing directional control problems and reduced rudder effectiveness. They also found that the pilots applied the wheel brakes manually, rather than in the automatic mode.

The captain and 10 passengers were killed; the first officer (FO), the flight attendants and 105 passengers received serious or minor injuries; and 24 passengers were not injured. The airplane was destroyed by impact forces and a postcrash fire.

The NTSB concluded that during the descent into the terminal area, the flight crewmembers could have “reasonably” believed they could reach the airport before the thunderstorm. That belief may have been reinforced because the FO was able to maintain visual contact with the runway as they were vectored for the final approach course.

Nevertheless, the Safety Board said the probable causes of the accident were the flight crew’s failure to discontinue the approach when severe thunderstorms and their associated hazards to flight operations had moved into the airport area, and the flight crew’s failure to ensure that the spoilers had extended after touchdown.

Contributing to the accident, the NTSB continued, were the flight crew’s impaired performance resulting from fatigue and the situational stress associated with the intent to land under the circumstances; continuation of the approach to a landing when American Airlines’ maximum crosswind component was exceeded; and use of reverse thrust greater than 1.3 engine pressure ratio after landing.

The cockpit voice recorder (CVR) indicated that the crew had a high workload during the airplane’s final approach segment, when they had to maneuver the MD-82 in increasing turbulence, configure it for landing and run the remaining items on the “before-landing checklist, as well as evaluate the rapidly changing weather and visibility conditions and several wind reports.”

At the public hearing on the crash in Little Rock in January last year, the FO recol-
lected how “fast and compressed” everything seemed to happen as they were making their base-to-final turn. At the time, the flight crew had been on duty for about 13 hr and awake for about 16 hr.

As a result of the accident, the NTSB called on the FAA to establish a joint government-industry working group to reduce thunderstorm penetrations and, as a near-term goal, establish clear and objective criteria to help pilots recognize the signs of severe convective activity and improve decision-making.

The Safety Board also reiterated its 1999 recommendation that the FAA come up with scientifically based hours-of-service regulations that provide predictable work and rest schedules and consider circadian rhythms and sleep and rest requirements.

In its recommendation for a government-industry working group to “address, understand and develop effective operational strategies to reduce thunderstorm penetrations, and verify that these strategies are incorporated into air carrier flight manuals and training programs as the strategies become available,” the NTSB said the group should focus its efforts on all facets of the airspace system, including ground- and cockpit-based solutions.

In response to a question by AIN on how long it might take to develop such strategies, and what form they might take, new NTSB chairman Marion Blakey replied, “I wish I were in position to conjecture usefully on that.” At a Safety Board meeting in October in Washington to adopt its final report on the crash, it was brought out that there are 1,000 such penetrations of severe thunderstorms each year.

“We’re not sure what is the best form that should take,” admitted John Clark, director of the NTSB’s office of aviation safety. “In the simplest form, we could name six big parameters and if three of them fall, you get out of there. Perhaps something like that is effective.”

Clark said that some other training aids–such as those for rejected takeoffs, wake vortices and wind shear–have taken about a year to develop, and a similar timetable might be realistic for new thunderstorm guidelines. He also suggested that rather than creating a new group, a “perfect forum” might be the already-existing Commercial Aviation Safety Team (CAST).

Similarly, neither Blakey nor Clark could estimate any timeline for FAA action on new flight, duty and rest regulations. In 1995 the FAA issued a notice of proposed rulemaking (NPRM) on the subject, which resulted in thousands of public comments. But no further action was ever made public.

Then in 1999, the FAA assured Congress that updated pilot flight- and duty-time regulations would be out early last year. When that didn’t materialize, last August 31 members of Congress–noting that the current regulations have been in effect since 1985–again urged the FAA to take immediate action.

“We’re certainly available to discuss any issues they want,” said Clark. “But how they proceed and how they want to work with industry to try to get resolution on this, I don’t have a clue. It seems to be at an impasse, and we just want to raise the issue again and get them to go at it again until we get a resolution.”

Flight 1420 was the third and final flight leg of the first day of a three-day sequence for the flight crew. The captain and FO reported to O’Hare International Airport for the first leg at about 10:30 a.m. CDT, and departed at about 11:43 a.m. to Salt Lake City International Airport (SLC). The second leg took them from SLC to Dallas/Fort Worth International Airport (DFW).

But Flight 1420’s departure from DFW was delayed because the airplane that was to be used for the last leg had not arrived due to weather. Another airplane was substituted, and the flight departed at 10:40 p.m. CDT, which was about 2 hr 12 min later than the scheduled departure time.

Before leaving DFW the crew was advised of widely scattered thunderstorms along the route, including an area of severe thunderstorm activity. While en route, severe thunderstorm activity was reported moving into the Little Rock area, and a company message suggested they expedite their arrival to beat the weather if possible.

The CVR did not contain any discussion between the pilots about the possibility of holding to allow the storm to pass or diverting to one of the alternate airports. When they arrived in the Little Rock terminal area, the tower controller advised the flight crew that a thunderstorm located northwest of the airport was moving “through the area.” The first officer said in a post-accident interview that, during the descent into LIT, he and the captain thought that there was “some time” to make the approach.

The crew was initially planning to land on Runway 22L, but based on changing wind direction, they requested Runway 4R so there would be a headwind during landing. Despite the thunderstorms in the area, the flight crew, particularly the FO, was able to see the airport during most of the maneuvering to final and during the final approach segment.

As the MD-82 neared the runway, however, they encountered decreasing visibility, heavy rain and increasing crosswinds. In a post-accident interview, the FO indicated there was urgency to land at this point because the weather was “up against” the airport.

As the captain continued the approach through the decision height to a landing, they added an additional 20 kt to the normal approach speed because of the weather, making it slightly more than 150 kt. The calculated groundspeed at touchdown was 160 kt.

Flight 1420 touched down about 2,000 ft from the runway threshold, to the right of the runway centerline, and moved rapidly to the right. Shortly after touchdown, the FO stated, “We’re sliding.”

According to calculations based on flight data recorder (FDR) information, the aircraft was subjected to a 20- to 25-kt crosswind component during the landing. When it ran off the runway, its speed was calculated at 97 kt, and it was still doing 83 kt when it hit the light supports.

NTSB found that the aircraft’s performance after landing was consistent with the friction coefficient of a wet runway and without the spoilers extended. Hydroplaning was not found to be a factor in the airplane’s inability to stop on the runway. Additionally, calculations demonstrated that had the spoilers been deployed, it would have been possible to stop the airplane on the runway.