In addition to the decisions and actions of the flight crewmembers, overwater safety equipment likely saved lives that might have otherwise been lost to drowning, the NTSB said.
Today the Safety Board met to conclude its 15-month investigation into the January 15, 2009, accident in which a US Airways A320 jetliner bound for Charlotte was ditched into the Hudson River after striking a flock of Canada geese shortly after departing New York's LaGuardia Airport. All of the 150 passengers and five crewmembers survived.
Investigators said that had the airplane not been equipped with forward slide/rafts, many of the 64 occupants of those rafts would likely have been submerged in the 41-degree Hudson River, potentially causing a phenomenon called "cold shock," which can lead to drowning in as little as five minutes.
The accident flight had the additional safety equipment available only because the particular aircraft operated that day happened to be certified for extended overwater (EOW) operations even though current FAA regulations did not require the flight from New York to Charlotte to be so equipped.
Good visibility, calm waters, and proximity of passenger ferries, which rescued everyone on flight 1549 within 20 minutes, were other post-accident factors the Safety Board credited with the survival of all aboard the aircraft.
"Once the birds and the airplane collided and the accident became inevitable, so many things went right," said NTSB Chairman Deborah A.P. Hersman. "This is 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."
The Safety Board said that the probable cause of the accident was the ingestion of large birds into each engine, resulting in an almost total loss of engine power. Contributing to the severity of the fuselage damage and resulting unavailability of the aft slide/rafts, the Board cited the FAA's inadequate ditching certification standards, lack of industry training on ditching techniques, and the captain's resulting difficulty maintaining his intended airspeed on final approach due to task saturation resulting from the emergency situation.
The report adopted by the Safety Board today validated the Captain's decision to ditch into the Hudson River saying that it "provided the highest probability that the accident would be survivable." Contributing to the survivability of the accident was the crew resource management between the captain and first officer, which allowed them to maintain control of the airplane, increasing the survivability of the impact with the water.
In addressing the hazards that birds pose to aircraft of all sizes, the report noted that most bird strike events occur within 500 feet of the ground while flight 1549 struck geese at 2700 feet. Investigators said that this difference demonstrates that "bird strike hazards to commercial aircraft are not limited to any predictable scenario."
Concluding that engine screens or changes to design would not be a viable solution to protect against bird ingestion events on commercial jetliners, the Board made it clear that the potential for significant damage from encounters with birds remains a challenge to the aviation community.
As part of its extensive examination into the behavior of the passengers and crewmembers from the time the plane left the gate at LaGuardia to the moment the last person was rescued in the river, the Board noted that since most of the passengers indicated that they had not paid attention to the preflight oral safety briefing, "more creative and effective methods of conveying safety information to passengers" was needed. Survival factors investigators also found that passengers had significant problems in donning the life vests that were stowed under each seat.
The Board made 35 safety recommendations on engine and aircraft certification standards, checklist design, flight crew training, airport wildlife mitigation, cabin safety equipment, and preflight passenger briefings.
"I believe the safety recommendations that have come out of this investigation have an extraordinary origin -- a very serious accident in which everyone survived," said Chairman Hersman. "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 synopsis of the Board's report, including the probable cause, conclusions, and recommendations, is available on the NTSB's website.
The Board's full report will be available on the website in several weeks.