Aircraft
The aircraft was an Airbus A320-214, registered N106US, powered by two GE Aviation/Snecma-designed CFM56-5B4/P turbofan engines manufactured in France and the U.S. One of 74 A320s then in service in the US Airways fleet, it was built by Airbus with final assembly at its facility at Aéroport de Toulouse-Blagnac in France in June 1999. Delivered to the carrier on August 2, 1999, the airliner was registered to Wells Fargo Bank Northwest, NA, as owner/lessor with AIG listed as the lead insurer.
The aircraft's FAA-required maintenance records, released by US Airways the day after the accident, showed that when N106US was written off, its airframe had logged 16,299 cycles (flights) totaling 25,241.08 flight hours. Total time on the engines was 19,182 hours on the left (#1) and 26,466 hours on the right (#2). The last A Check, a maintenance check performed every 550 flight hours, was passed on December 6, 2008, and the last C Check (annual comprehensive inspection) on April 19, 2008.
The Airbus A320 is a digital fly-by-wire aircraft: the flight control surfaces are moved by electrical and hydraulic actuators controlled by a digital computer. The computer interprets pilot commands via input from a side-stick, making adjustments on its own to keep the plane stable and on course, which is particularly useful after engine failure by allowing the pilots to concentrate on engine restart and landing planning.
The mechanical energy of the two engines is the primary source of routine electrical power and hydraulic pressure for the aircraft flight control systems. The aircraft also has an auxiliary power unit (APU), which can provide backup electrical power for the aircraft, including its electrically powered hydraulic pumps; and a ram air turbine (RAT), a type of wind turbine that can be deployed into the airstream to provide backup hydraulic pressure and electrical power at certain speeds. According to the NTSB, both the APU and the RAT were operating as the plane descended into the Hudson, although it was not clear whether the RAT had been deployed manually or automatically.
The Airbus A320 has a "ditching" button that closes valves and openings underneath the aircraft, including the outflow valve, the air inlet for the emergency RAT, the avionics inlet, the extract valve, and the flow control valve. It is meant to slow flooding in a water landing. The flight crew did not activate the "ditch switch" during the incident. Sullenberger later noted that it probably would not have been effective anyway, since the force of the water impact tore holes in the plane's fuselage much larger than the openings sealed by the switch.
Read more about this topic: US Airways Flight 1549