Tuesday, May 4, 2010

The United States National Transportation Safety Board (NTSB) has completed its investigation into the ditching of US Airways Flight 1549 into New York’s Hudson River. The fifteen-month probe began after the Airbus A320 performed a water landing when bird strikes damaged both engines in a move dubbed the “Miracle on the Hudson” by the media. Nobody was killed.

The NTSB’s final report, adopted after a board meeting today, concluded that a combination of safety equipment better than the mandatory minimums and good reactions by the crew were the main reasons the 150 passengers and five crew survived. The board stated that the aircraft’s equipment met the standards required for “extended overwater operations”, equipment that was not needed for the January 2009 flight.

The aircraft was equiped with escape slides that doubled as water rafts at the front and aft emergency exits, but the aft ones were rendered unavailable. Airbus assumed when designing the aircraft that only one engine would be inoperative during an emergency ditching, and current emergency checklists assume plenty of prior warning for dual-engine failure since the aircraft would be at a high altitude. The A320 was at just 2,700 feet when the incident occurred, having just taken off when it collided with a flock of Canada geese, almost completely removing the engines’ ability to generate thrust.

The final report has blamed a number of factors for extensive fuselage damage caused in the impact, which cracked a rear bulkhead and caused the aircraft to flood, as well as taking the rear slides out of action. The board said standards aircraft should meet in ditchings — set by the Federal Aviation Authority (FAA) — were inadequate, training in industry was not sufficient for ditchings and the high level of tasks the crew had to focus on made it difficult for the pilot to maintain his airspeed. The pilot’s decision to ditch was credited as being the best possible solution to the emergency.

The NTSB noted that while the rear rafts failed, 64 people climbed into the forward rafts, and said many of these people would have been immersed in the frigid river. The board claimed that this could induce “cold shock”, which can lead to drowning within minutes.

The report found that the good visibility, calm water, nearby ferries which provided rescues within twenty minutes and good cockpit resource management, allowing the crew to maintain control, were further factors that contributed to the survival of those on board. However, it also found that “more creative and effective methods of conveying safety information to passengers” are required after learning that most passengers had not paid attention to the in-flight safety announcement. It also noted that many passengers had difficulty putting on the life vests supplied under the seats.

The report further stated that the accident was hard to predict due to the fact that bird strikes tend to occur much lower, usually below 500 feet. It considered the possibilities of fitting engine screens or redesigning engines to mitigate bird strike risk, but these proposals were rejected after consideration since they were deemed unfeasable.

NTSB Chairman Deborah A.P. Hersman described the circumstances as “a great example of the professionalism of the crewmembers, air traffic controllers and emergency responders who all played a role in preserving the safety of everyone aboard.” She further discussed the safety recommendations the report will contain when it is released. “I believe the safety recommendations that have come out of this investigation have an extraordinary origin – a very serious accident in which everyone survived. Even in an accident where everyone survives, there are lessons learned and areas that could use improvement. Our report today takes these lessons learned so that, if our recommendations are implemented, every passenger and crewmember may have the opportunity to benefit from the advances in safety.” A total of 35 recommendations have been made seeking improved checklists for emergencies, better certification standards for aircraft and their engines, advances in crew training, better safety equipment and improved safety briefings to passengers.

One result of these findings is that the board will likely ask the FAA to require emergency equipment for water landings on all commercial aircraft. The FAA has until now held that such a move would place a disproportionately high cost on airlines.