[Update: AA 331 did land on Runway 12 as I had guessed. A reader pointed out that there is no ILS approach to runway 30. Thus it makes perfect sense that they chose the ILS to Runway 12. However, some people reported that the aircraft touched down nearly half way down the runway. If true, that will undoubtedly turn out to be a contributing factor to this accident] At shortly before 10:30 PM last night, a landing American Airlines Boeing 737-800, that originated at Ronald Reagan Washington National Airport, overan the runway at Kingston, Jamaica's Norman Manley International Airport. Flight 331 reportedly crossed a road and may have ended up on a beach just short of the Caribbean. The Jamaica Observer reported 40 injured passengers and Jamaica TV reported in a CNN video that 4 of the injuries were serious. There were conflicting reports about whether the aircraft broke up into as many as three pieces after the accident.

According to the National Oceanic and Atmospheric Administration web site, the 10 PM weather in Kinston was reported to include heavy rain showers. The temperature was 69°F, dew point was 66°F and the winds were out of the northwest at 13 knots. Looking at a Google Maps satellite photo and comparing it with Jamaica TV’s report that the aircraft overran the runway and “crossed a road,” suggests that the aircraft landed on runway 12 with a tailwind. If so, the accident may turn out to be similar to a December 2005 accident at Chicago’s Midway Airport in which a Southwest Boeing 737-700 landed downwind with a 11 knot tailwind. It encountered poor braking action due to snow and ice on the runway and was still traveling at 53 knots as it overran the runway.



Landing with a tailwind increases landing distances. For example, a landing distance calculator for a Boeing 737-500 indicates that when landing at 61 tons with no wind on a dry runway, 4565 feet is required. However with poor braking action, the required landing distance increases to 8855 feet. The only runway at Kingston’s airport is 8786 feet long. With a 10 knot tailwind, the landing distances increase to 5055 feet and 10,370 feet respectively. With a 10 knot headwind, the landing distances decrease to 4435 feet and 8455 feet respectively.



While pilots are generally encouraged to land into a headwind, there are operational reasons when landing with a tailwind is preferred. In the case of the Southwest jet, an AOPA Pilot article said “Changing runways might have had a negative impact on operations at Chicago O’Hare International, 13 nm to the northwest, so the air traffic considerations must be weighed against the safety implications.”



It’s less clear that there were any compelling reasons why American Airlines flight 331 had to make a downwind landing. If the pilots did choose to land with a tailwind, more than likely they did so because they wanted to decrease their taxi time to the terminal. Had they landed with a headwind on runway 30, they would have had to taxi more than a mile to return to the terminal. By landing on runway 12, they would have rolled out next to the terminal, saving several minutes of taxi time.



If the pilots did make a downwind landing onto runway 12, then another subtle factor may have played a role: Flight 331 was running late. The flight stops in Miami before continuing on to Jamaica and according to American Airlines online schedule, Flight 331 departs at Miami at 7:25PM. But, according to www.flightaware.com, for the last seven days, the flight departed on average at 7:46 PM. But last night, it departed at 8:53 PM, about an hour and a half late.



Could Flight 331’s crew have felt pressured to save 2-3 minutes of taxi time because they were running late? Absolutely. Would a downwind landing have mattered with a normal, dry runway? No, not at all. But with heavy rains and a wet runway, the crew may have been betting that everything else would go right. In the case of the Southwest overrun at Midway airport, a compounding factor was that the thrust reversers were not deployed until 15 seconds after touchdown; the four airliners that landed in the 20 minutes prior all deployed their thrust reversers in 4 to 6 seconds after touchdown.



Risk management and safe flying is all about building in lots of extra margin into every decision. It’s reasonable to shave the margins—for example by making a downwind landing—but then it’s important that there are no additional compounding factors. It will be a long time before we know the full story behind exactly what happened last night at Jamaica, but one thing is certain. Somewhere in the process, a decision or malfunction eroded the safety margins, causing this accident.