Airbus A320-214 accident at New York, 15 Jan 2009

Accident narrative

**Loss of Thrust in Both Engines After Encountering a Flock of Birds and Subsequent Ditching on the Hudson River**

On January 15, 2009, about 1527 eastern standard time, US Airways flight 1549, an Airbus A320-214, experienced an almost complete loss of thrust in both engines after encountering a flock of birds. The airplane was subsequently ditched on the Hudson River about 8.5 miles from LaGuardia Airport in New York City. The 150 passengers, including a lap-held child, and 5 crewmembers evacuated the airplane. One flight attendant and four passengers were seriously injured, and the airplane was substantially damaged.

**The Flight** The scheduled domestic passenger flight was en route to Charlotte Douglas International Airport (CLT) in North Carolina. The captain, 57, had accumulated 19,663 total flight hours, including 4,765 hours in A320 airplanes. The first officer, 49, had 15,643 total flight hours, including 37 hours in A320 airplanes.

At 1524:54, the LaGuardia (LGA) air traffic control tower cleared the flight for takeoff from runway 4. The first officer was the pilot flying, and the captain was the pilot monitoring. The takeoff and initial climb were uneventful. At 1525:51, the captain contacted the departure controller, advising that the airplane was at 700 feet and climbing to 5,000 feet.

**The Sequence of Events** At 1527:10.4, the captain stated, "birds." One second later, the cockpit voice recorder (CVR) recorded the sound of thumps and thuds followed by a shuddering sound. Flight data recorder (FDR) data indicated the bird encounter occurred at an altitude of 2,818 feet above ground level, about 4.5 miles north-northwest of the approach end of runway 22 at LGA. Immediately after the encounter, both engines’ fan and core speeds started to decelerate.

At 1527:14, the first officer stated, "uh oh," and the captain stated, "we got one rol- both of ‘em rolling back." At 1527:19, the captain stated, "ignition, start," and about two seconds later, "I’m starting the APU [auxiliary power unit]." At 1527:23, the captain took over control of the airplane, stating, "my aircraft."

The captain instructed the first officer to get the quick reference handbook (QRH) for loss of thrust on both engines. At 1527:33, the captain transmitted to the departure controller: "mayday mayday mayday…this is…Cactus fifteen thirty nine hit birds, we’ve lost thrust in both engines, we’re turning back towards LaGuardia."

At 1527:50, the first officer began conducting Part 1 of the Engine Dual Failure checklist. He noted that the checklist called for an optimum relight airspeed of 300 knots, stating, "we don't have that," to which the captain responded, "we don't."

At 1528:05, the departure controller asked if the captain wanted to try to land on runway 13 at LGA. The captain responded, "we’re unable. we may end up in the Hudson." At 1528:36, the airplane's traffic collision avoidance system transmitted a "traffic traffic" alert as the airplane passed close above a helicopter.

At 1528:46, the controller stated that runway 4 at LGA was available. The captain responded, "I’m not sure we can make any runway. Uh what’s over to our right anything in New Jersey maybe Teterboro?" The controller offered Teterboro Airport (TEB), and the captain initially replied, "yes." However, at 1529:21, when the controller offered runway 1 at TEB, the captain stated, "we can't do it." The controller asked which runway at TEB he would like, and the captain responded, "we're gonna be in the Hudson."

At 1529:11, the captain announced on the public address system, "this is the Captain, brace for impact." The first officer continued attempts to restart the engines, manipulating the engine master switches, but at 1529:44 stated, "no relight." The captain then called for flaps, and the first officer selected flaps 2.

During the final descent, the ground proximity warning system (GPWS) issued multiple alerts, including "too low, terrain," "too low, gear," and "pull up." At 1530:43, the airplane touched down on the Hudson River. FDR data indicated the airplane ditched at an airspeed of 125 knots calibrated airspeed, a pitch angle of 9.5 degrees, and a descent rate of 12.5 feet per second.

**Evacuation and Emergency Response** Within seconds after the ditching, the crew and passengers initiated the evacuation. Water impact damage to the aft fuselage allowed a large volume of water to enter the airplane rapidly, rendering the two aft doors and their slide/rafts unusable. Flight attendant B and passengers in the aft cabin redirected occupants to move forward over the seats to escape the rising water.

At the forward exits, flight attendant A opened door 1L, but the slide/raft did not inflate automatically; she pulled the manual inflation handle and it inflated. Flight attendant C opened door 1R, which began to close and impinge on the slide/raft; she assigned a passenger to hold the door open. Passengers also opened the four overwing exits, which automatically deployed the off-wing ramp/slides, and evacuated onto the wings and the ramp/slides.

New York Waterway ferries operating nearby responded immediately. The first ferry arrived on scene about 1534, and six others arrived by 1540. U.S. Coast Guard and Fire Department of New York vessels also responded. All occupants were rescued from the slide/rafts, wings, and water.

**What the Investigation Found: Engines and Certification** The Board found that both CFM56-5B4/P engines were operating normally until they each ingested at least two Canada geese weighing about 8 pounds each. Both engine spinners exhibited soft-body impact damage, indicating a bird was ingested near the inner radius of each engine inlet and entered the core.

In both engines, low-pressure compressor inlet guide vanes were fractured and ingested into the core, causing secondary damage. In the left engine, the high-pressure compressor variable guide vanes were disconnected, blocking airflow. In the right engine, the variable guide vanes were destroyed, causing continuous compressor stalls. The Board concluded that the mechanical damage prevented the engines from providing sufficient thrust to sustain flight, and no pilot action could have returned them to operational status.

The Board noted that the size and number of the birds well exceeded the certification standards in effect when the engine was certificated. The engines had been tested to withstand a single 4-pound bird, and later a 2.5-pound bird volleyed into the core. The Board concluded that an engine of this size cannot withstand the ingestion of an 8-pound bird into the core, and that current small and medium flocking bird tests would be more stringent if conducted at the lowest expected fan speed rather than 100-percent fan speed, as a slower speed allows more bird mass to enter the core.

The Board also noted that the flight crew spent 30 to 40 seconds trying to relight the engines because they were unaware of the extent of the internal damage. The Board concluded that if the electronic control system had been capable of informing the crew about the engines' operational status, they would not have spent valuable time trying to relight them.

**What the Investigation Found: Flight Crew Performance and Checklists** The Board concluded that the captain’s decision to ditch on the Hudson River provided the highest probability of survival. Postaccident flight simulations showed that a successful landing at LGA or TEB would have required the airplane to be turned toward the airport immediately after the bird strike, without any delay to recognize the situation or decide on a course of action. A simulation that included a 35-second delay for decision-making was not successful.

The Board found that the captain's immediate action to start the APU improved the outcome of the ditching. The APU ensured electrical power was available and that the fly-by-wire airplane remained in "normal law," maintaining flight envelope protections that prevent a stall.

The flight crew used the QRH Engine Dual Failure checklist, which the Board noted was the most applicable checklist available. However, the checklist was designed for a dual-engine failure at high altitude (above 20,000 feet). Because of the low altitude and limited time, the crew could only complete about one-third of the checklist and never reached the ditching procedures located in Part 3. The Board concluded that a checklist specifically designed for a low-altitude dual-engine failure is needed.

The Board found that the captain had difficulty maintaining his intended airspeed during the final approach. The checklist called for "green dot" speed (the optimum glide speed), but FDR data showed the airplane was flown at or below VLS (the lowest selectable airspeed providing an appropriate margin to stall) for most of the descent. The Board concluded this resulted from high workload, stress, and task saturation. Furthermore, the A320's low-energy aural warning was inhibited by the GPWS alerts, meaning the crew was not aurally warned of the low-speed state. The low airspeed resulted in high angles-of-attack, which contributed to difficulties in flaring the airplane and the high descent rate at touchdown.

During the last 50 feet, the captain pulled the sidestick to its aft limit to flare the airplane. However, because the airplane was in the alpha-protection mode, the flight control system attenuated his inputs, limiting the nose-up response even though a margin remained before the maximum allowable angle-of-attack. The Board noted that Airbus training does not inform pilots that sidestick inputs may be attenuated in this mode.

The captain's decision to use flaps 2 for the ditching was deemed reasonable by the Board, as it was consistent with the limited guidance available regarding forced landings without power, which suggests using a lesser flap setting to maintain energy for the flare.

**What the Investigation Found: Airframe and Ditching Certification** The airplane met the structural ditching certification regulations in effect at the time. The A320 ditching certification was based on scale model tests of similar aircraft and assumed a descent rate of 3.5 feet per second and an 11-degree pitch.

The accident airplane touched down at a descent rate of 12.5 feet per second. The Board found that this high-energy impact caused external pressures that significantly exceeded certification values, resulting in the large-scale collapse of the aft fuselage frames, cargo floor, and passenger floor struts.

The Board concluded that the certification process did not evaluate whether pilots could actually attain the ditching parameters without engine power. Flight simulations indicated that attaining these parameters without power is exceptionally difficult. Consequently, the Board found that the assumption that a ditched fuselage will remain intact enough to allow the use of aft slide/rafts is flawed.

**What the Investigation Found: Survival Factors** The airplane was equipped for extended overwater (EOW) operations, meaning it carried passenger life vests and four 44-person slide/rafts. Because the flight was not an EOW route, it was not required to carry this equipment. The Board concluded that this fortuitous equipage contributed to the lack of fatalities, as about 64 occupants were rescued from the forward slide/rafts. Without them, passengers would have been forced into the 41°F water, where cold shock and swimming failure can cause death within minutes.

Passengers also utilized the off-wing ramp/slides. However, these were designed for ground evacuations and lacked quick-release girts, meaning passengers could not detach them from the sinking airplane. The airplane was also equipped with life lines for the overwing exits, but they were not used; the Board noted that passengers are not briefed on their existence.

During the impact, the FR65 vertical beam—a nonstructural beam b