Sully's Challenge: "Miracle on the Hudson" – Official Investigation & Full Report of the Federal Agency E-Book

National Transportation Safety Board

• Herausgeber: Madison & Adams Press
• Kategorie: Fachliteratur
• Sprache: Englisch
• Veröffentlichungsjahr: 2017

Seitenzahl: 321

Beschreibung

How can a 10 pound bird bring down a 150,000 pounds aircraft? How would you feel if you were the captain on that aircraft, responsible for 155 souls? What would you do to prevent the disaster? How would you communicate with other crew members and the passengers? How would you determine where to try to ditch the plane in an unprecedented situation? How would training and experience influence your decision? What lessons can we learn from Captain Sullenberger's calm actions which incredibly saved all lives onboard? Successful Ditching of US Airways Flight 1549 on Hudson River by Captain Chesley Sullenberger and First Officer Jeff Skiles on January 15, 2009 - This edition provides all the details of this incredible event, transcripts of pilot's communications and the final results of a thorough investigation. They analyzed in great detail the aircraft, the accident, the damages; the personnel on board and on the ground, their training and their communications, their actions during the accident; the survival aspects, the birds, the meteorology and more. Finally they drew their conclusions and put together their recommendations based on the results of the examination, to prevent similar events in the future.

Leseprobe

National Transportation Safety Board

Sully’s Challenge: “Miracle on the Hudson”

Official Investigation & Full Report of the Federal Agency

Madison & Adams Press, 2017. No claim to original U.S. Government Works Contact [email protected]

ISBN 978-80-268-7331-0

This is a publication of Madison & Adams Press. Our production consists of thoroughly prepared educational & informative editions: Advice & How-To Books, Encyclopedias, Law Anthologies, Declassified Documents, Legal & Criminal Files, Historical Books, Scientific & Medical Publications, Technical Handbooks and Manuals. All our publications are meticulously edited and formatted to the highest digital standard. The main goal of Madison & Adams Press is to make all informative books and records accessible to everyone in a high quality digital and print form.

Table of Contents

Executive Summary

1. Factual Information

1.1 History of Flight

1.2 Injuries to Persons

1.3 Damage to Airplane

1.4 Other Damage

1.5 Personnel Information

1.6 Airplane Information

1.7 Meteorological Information

1.8 Aids to Navigation

1.9 Communications

1.10 Airport Information

1.11 Flight Recorders

1.12 Wreckage and Impact Information

1.13 Medical and Pathological Information

1.14 Fire

1.15 Survival Aspects

1.16 Tests and Research

1.17 Organizational and Management Information

1.18 Additional Information

2. Analysis

2.1 General

2.2 Engine Analysis

2.3 Flight Crew Performance

2.4 Abnormal and Emergency Events Checklist Design

2.5 Pilot Training

2.6 Operational Difficulties Not Factored Into Certification Tests

2.7 High-AOA-Related Issues

2.8 Bird- and Other Wildlife-Strike Issues

2.9 Emergency Response

2.10 Survival Factors Issues

3. Conclusions

3.1 Findings

3.2 Probable Cause

4. Safety Recommendations

4.1 New Recommendations

4.2 Previously Issued Safety Recommendation Resulting From This Accident

Board Member Statement

5. Appendixes

Appendix A: Investigation and Public Hearing

Appendix B: Cockpit Voice Recorder Transcript

Appendix C: US Airways Engine Dual Failure Checklist

Figures

Tables

Abbreviations

Executive Summary

Table of Contents

On January 15, 2009, about 1527 eastern standard time, US Airways flight 1549, an Airbus Industrie A320-214, N106US, experienced an almost complete loss of thrust in both engines after encountering a flock of birds and was subsequently ditched on the Hudson River about 8.5 miles from LaGuardia Airport (LGA), New York City, New York. The flight was en route to Charlotte Douglas International Airport, Charlotte, North Carolina, and had departed LGA about 2 minutes before the in-flight event occurred. The 150 passengers, including a lap-held child, and 5 crewmembers evacuated the airplane via the forward and overwing exits. One flight attendant and four passengers were seriously injured, and the airplane was substantially damaged. The scheduled, domestic passenger flight was operating under the provisions of 14 Code of Federal Regulations Part 121 on an instrument flight rules flight plan. Visual meteorological conditions prevailed at the time of the accident.

The National Transportation Safety Board determines that the probable cause of this accident was the ingestion of large birds into each engine, which resulted in an almost total loss of thrust in both engines and the subsequent ditching on the Hudson River. Contributing to the fuselage damage and resulting unavailability of the aft slide/rafts were (1) the Federal Aviation Administration’s (FAA) approval of ditching certification without determining whether pilots could attain the ditching parameters without engine thrust, (2) the lack of industry flight crew training and guidance on ditching techniques, and (3) the captain’s resulting difficulty maintaining his intended airspeed on final approach due to the task saturation resulting from the emergency situation.

Contributing to the survivability of the accident was (1) the decision-making of the flight crewmembers and their crew resource management during the accident sequence; (2) the fortuitous use of an airplane that was equipped for an extended overwater flight, including the availability of the forward slide/rafts, even though it was not required to be so equipped; (3) the performance of the cabin crewmembers while expediting the evacuation of the airplane; and (4) the proximity of the emergency responders to the accident site and their immediate and appropriate response to the accident.

The safety issues discussed in this report relate to the following: in-flight engine diagnostics, engine bird-ingestion certification testing, emergency and abnormal checklist design, dual-engine failure and ditching training, training on the effects of flight envelope limitations on airplane response to pilot inputs, validation of operational procedures and requirements for airplane ditching certification, and wildlife hazard mitigation. The report also discusses survival-related issues, including passenger brace positions; slide/raft stowage; passenger immersion protection; life line usage; life vest stowage, retrieval, and donning; preflight safety briefings; and passenger education. Safety recommendations concerning these issues are addressed to the FAA, the U.S. Department of Agriculture, and the European Aviation Safety Agency.

1. Factual Information

Table of Contents

1.1 History of Flight

Table of Contents

On January 15, 2009, about 1527 eastern standard time (EST),1 US Airways flight 1549, an Airbus Industrie A320-214, N106US, experienced an almost total loss of thrust in both engines after encountering a flock of birds and was subsequently ditched on the Hudson River about 8.5 miles from LaGuardia Airport (LGA), New York City, New York. The flight was en route to Charlotte Douglas International Airport (CLT), Charlotte, North Carolina, and had departed LGA about 2 minutes before the in-flight event occurred. The 150 passengers, including a lap-held child, and 5 crewmembers evacuated the airplane via the forward and overwing exits. One flight attendant and four passengers received serious injuries, and the airplane was substantially damaged. The scheduled, domestic passenger flight was operating under the provisions of 14 Code of Federal Regulations (CFR) Part 121 on an instrument flight rules flight plan. Visual meteorological conditions prevailed at the time of the accident.2

The accident flight was the last flight of a 4-day trip sequence for the flight and cabin crewmembers3 and the second flight of the day in the accident airplane. The flight crew flew from Pittsburgh International Airport (PIT), Pittsburgh, Pennsylvania, to CLT on a different airplane and then flew the accident airplane from CLT to LGA. The flight crew reported that the flight from CLT to LGA was uneventful.

According to the cockpit voice recorder (CVR) transcript, at 1524:54, the LGA air traffic control tower (ATCT) local controller cleared the flight for takeoff from runway 4. At this time, the first officer was the pilot flying (PF), and the captain was the pilot monitoring (PM). According to the accident flight crew and CVR and flight data recorder (FDR) data, the takeoff and initial portion of the climb were uneventful.

At 1525:45, the LGA ATCT local controller instructed the flight crew to contact the New York Terminal Radar Approach Control (TRACON) LGA departure controller. The captain contacted the departure controller at 1525:51, advising him that the airplane was at 700 feet4 and climbing to 5,000 feet. The controller then instructed the flight to climb to and maintain 15,000 feet, and the captain acknowledged the instruction.

According to the CVR transcript, at 1527:10.4, the captain stated, “birds.” One second later, the CVR recorded the sound of thumps and thuds followed by a shuddering sound. According to FDR data, the bird encounter occurred when the airplane was at an altitude of 2,818 feet above ground level (agl) and a distance of about 4.5 miles north-northwest of the approach end of runway 22 at LGA. At 1527:13, a sound similar to a decrease in engine noise or frequency began on the CVR recording. FDR data indicated that, immediately after the bird encounter, both engines’ fan and core (N1 and N2, respectively) speeds started to decelerate. (See section 1.16.1.1 for more information about the airplane’s performance during the accident sequence.)

At 1527:14, the first officer stated, “uh oh,” followed by the captain stating, “we got one rol- both of ‘em rolling back.” At 1527:18, the cockpit area microphone (CAM) recorded the beginning of a rumbling sound. At 1527:19, the captain stated, “[engine] ignition, start,” and, about 2 seconds later, “I’m starting the APU [auxiliary power unit].”5 At 1527:23, the captain took over control of the airplane, stating, “my aircraft.”

At 1527:28, the captain instructed the first officer to “get the QRH [quick reference handbook] loss of thrust on both engines.”6 At 1527:33, the captain reported the emergency situation to the LGA departure controller, stating, “mayday mayday mayday…this is…Cactus fifteen thirty nine hit birds, we’ve lost thrust in both engines, we’re turning back towards LaGuardia.”7 The LGA departure controller acknowledged the captain’s statement and then instructed him to turn left heading 220°.

At 1527:50, the first officer began conducting Part 1 of the QRH ENG DUAL FAILURE checklist (Engine Dual Failure checklist), stating, “if fuel remaining, engine mode selector, ignition,” and the captain responded, “ignition.” The first officer then stated, “thrust levers confirm idle,” and the captain responded, “idle.” About 4 seconds later, the first officer stated, “airspeed optimum relight. three hundred knots. we don’t have that,” and the captain responded, “we don’t.”8

At 1528:05, the LGA departure controller asked the captain if he wanted to try to land on runway 13 at LGA if it was available, and the captain responded, “we’re unable. we may end up in the Hudson [River].” The rumbling sound that the CVR started recording at 1527:18 ended at 1528:08. At 1528:14, the first officer stated, “emergency electrical power…emergency generator not online.” At 1528:19, the captain stated, “it’s online.” The first officer then stated, “ATC [air traffic control] notify.” At 1528:25, the captain stated, “The left one’s [engine] coming back up a little bit.”

At 1528:31, the LGA departure controller stated that it was going to be “left traffic for runway three one,” and the captain responded, “unable.” At 1528:36, the traffic collision avoidance system (TCAS) on the airplane transmitted, “traffic traffic.”9 At 1528:46, the controller stated that runway 4 at LGA was available, and 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?”10 The controller replied, “ok yeah, off your right side is Teterboro Airport [TEB].” Subsequently, the departure controller asked the captain if he wanted to try going to TEB, and the captain replied, “yes.”

At 1528:45, while the captain was communicating with ATC, the first officer stated, “FAC [flight augmentation computer] one off, then on.” Fifteen seconds later, the first officer stated, “no relight after thirty seconds, engine master one and two confirm.”11 At 1529:11, the captain announced on the public address (PA) system, “this is the Captain, brace for impact.” At 1529:14.9, the CVR recorded the ground proximity warning system (GPWS) warning alert, “one thousand.”12 At 1529:16, the first officer stated, “engine master two, back on,” and the captain responded, “back on.”

At 1529:21, the CVR recorded the LGA departure controller instructing the captain to turn right 280° and stating that the airplane could land on runway 1 at TEB. At the same time, the CVR recorded the first officer asking the captain, “is that all the power you got? (wanna) number one? Or we got power on number one.” In response to the controller, the captain stated, “we can’t do it.” In response to the first officer, the captain stated, “go ahead, try [relighting] number 1 [engine].” FDR data indicated that engine master switch 1 was moved to the OFF position at 1529:27. The departure controller then asked the captain which runway at TEB he would like, and the captain responded, “we’re gonna be in the Hudson.”

At 1529:36, the first officer stated, “I put it [the engine master switch] back on,” and the captain replied, “ok put it back on…put it back on.” At 1529:44, the first officer stated, “no relight,” and the captain replied, “ok let’s go put the flaps out, put the flaps out.” At 1529:53, the LGA departure controller stated that he had lost radar contact with the airplane, but he continued trying to communicate with the captain, stating, “you also got Newark airport off your two o’clock in about seven miles.”13 See figure 1 for the flight track of the airplane.

Figure 1. Flight track of the airplane.

At 1530:01, the first officer stated, “got flaps out,” and, at 1530:03, stated, “two hundred fifty feet in the air.” He then stated, “hundred and seventy knots…got no power on either one? Try the other one?” The captain responded, “try the other one.” At 1530:16, the first officer stated, “hundred and fifty knots,” and, at 1530:17, stated, “got flaps two, you want more?” The captain replied, “no, let’s stay at two,” and then asked the first officer, “got any ideas?” The first officer responded, “actually not.”

At 1530:24, the GPWS issued a “terrain, terrain” warning followed by “pull up,” which repeated to the end of the CVR recording. At 1530:38 The first officer then stated, “switch?”14 The captain replied, “yes.” At 1530:41.1, the GPWS issued a 50-foot warning.15 The CVR recording ended at 1530:43.7., the captain stated, “we’re gonna brace.”

Within seconds after the ditching on the Hudson River, the crewmembers and passengers initiated evacuation of the airplane. Subsequently, all of the occupants were evacuated from the airplane and rescued by area responders. (See sections 1.15.5 and 1.15.6 for information about the emergency evacuation and response, respectively.) Figure 2 shows the airplane occupants on the wings and in the slide/rafts after the evacuation.

Figure 2. A photograph showing the airplane occupants on the wings and in the slide/rafts after the evacuation.

1.2 Injuries to Persons

Table of Contents

Table 1. Injury chart.

Injuries

Flight Crew

Cabin Crew

Passengers

Other

Total

Fatal

0

0

0

0

0

Serious

0

1

4

0

5

Minor

0

0

95

0

95

None

2

2

51

0

55

Total

2

3

150

0

155

Note: Title 49 CFR 830.2, “Definitions,” states that a minor injury is any injury that does not qualify as a fatal or serious injury. The regulation defines a serious injury as any injury that (1) requires hospitalization for more than 48 hours, starting within 7 days from the date that the injury was received; (2) results in a fracture of any bone, except simple fractures of fingers, toes, or the nose; (3) causes severe hemorrhages or nerve, muscle, or tendon damage; (4) involves any internal organ; or (5) involves second- or third-degree burns or any burns affecting more than 5 percent of the body surface.

1.3 Damage to Airplane

Table of Contents

The airplane was substantially damaged.

1.4 Other Damage

Table of Contents

No other damage occurred as a result of this accident.

1.5 Personnel Information

Table of Contents

1.5.1 The Captain

The captain, age 57, was hired by Pacific Southwest Airlines on February 25, 1980.16 Before this, he flew McDonnell Douglas F-4 airplanes for the U.S. Air Force. At the time of the accident, he held a single- and multi-engine airline transport pilot (ATP) certificate, issued August 7, 2002, with type ratings in A320, Boeing 737, McDonnell Douglas DC-9, Learjet, and British Aerospace AVR-146 airplanes. The captain held a first-class Federal Aviation Administration (FAA) airman medical certificate, dated December 1, 2008, with no limitations.

According to US Airways records, the captain had accumulated 19,663 total flight hours, including 8,930 hours as pilot-in-command, 4,765 hours of which were in A320 airplanes. He had flown 155, 83, 39, and 5 hours in the 90, 60, and 30 days, and 24 hours, respectively, before the accident flight. The captain’s last A320 line check occurred on December 27, 2007; his last recurrent ground training occurred on February 19, 2008; and his last proficiency check occurred on February 21, 2008. A search of FAA records revealed no accident or incident history, enforcement action, pilot certificate or rating failure, or retest history. A search of the National Driver Register found no record of driver’s license suspension or revocation.

The captain stated that he was in excellent health, that he was not taking any prescription medications at the time of the accident, and that he had not taken any medications that might have affected his performance in the 72 hours before the accident. He stated that he drank occasionally but that he had not drunk any alcohol in the week and a half before the accident. The captain reported no major changes to his health, financial situation, or personal life in the last year. A US Airways first officer who had flown with the captain on a six-leg trip sequence in December 2008 described him as exceptionally intelligent, polite, and professional.

1.5.1.1 The Captain’s 72-Hour History

From December 31, 2008, to January 11, 2009, the captain was off duty at his home in the San Francisco, California, area. The captain stated that, when he was off duty, he typically went to sleep about 2300 and woke about 0700 Pacific standard time (PST). He stated that he typically needed about 8 hours of sleep to feel rested.

On January 12, the captain began a 4-day trip sequence with the first officer. He stated that they departed CLT at 1806 and arrived at San Francisco International Airport (SFO), San Francisco, California, at 2119 PST.17 He stated that he spent the evening at home and that he went to sleep about 2300 PST.

On January 13, the captain awoke about 0700 PST and ate breakfast. He stated that he left his house about 1100 PST and arrived at SFO about 1220 PST. The flight departed SFO about 1315 PST and arrived at PIT about 2100. The captain stated that the total layover time in Pittsburgh was about 10 hours. He added that he did not recall what time he went to bed.

On January 14, the captain awoke about 0510 and ate breakfast. He stated that the quality of his sleep the previous night was good or average and that, although he did not get 8 hours of sleep, he was “ok” and felt “normal.” The flight crew flew from PIT to LGA and then back to PIT. The captain stated that the total layover time in Pittsburgh was long. He added that he went for a walk around town, ate dinner, answered some e-mails, and went to bed about 2200.

On January 15, the captain awoke about 0640. He stated that the quality of his sleep the previous night was good and that he felt rested. The captain ate breakfast at PIT. The captain’s first flight departed PIT at 0856 and arrived at CLT at 1055, at which point the flight crew changed to the accident airplane. The captain stated that he did not get anything to eat in CLT. The flight departed CLT at 1154 and arrived at LGA at 1423. The captain stated that, because they had a quick turnaround at LGA, he purchased a sandwich to eat on the airplane after departure.

1.5.2 The First Officer

The first officer, age 49, was hired by US Airways on April 7, 1986. At the time of the accident, he held a multiengine ATP certificate, issued December 31, 2008, with type ratings in A320,18 Boeing 737, and Fokker 100 airplanes. The first officer held a first-class FAA airman medical certificate, dated October 7, 2008, with the limitation that he “must wear corrective lenses.” The first officer stated during postaccident interviews that he was wearing corrective lenses at the time of the accident.

According to US Airways records, the first officer had accumulated 15,643 total flight hours, including 8,977 hours as second-in-command (SIC). The first officer had 37 hours in A320 airplanes, all as SIC. He had flown 124, 55, 37, and 5 hours in the 90, 60, and 30 days, and 24 hours, respectively, before the accident flight. The first officer’s last line check on the A320 occurred on January 8, 2009, and his last proficiency check occurred on December 31, 2008. A search of FAA records revealed no accident or incident history, enforcement action, pilot certificate or rating failure, or retest history. A search of the National Driver Register found no record of driver’s license suspension or revocation.

The first officer stated that he was in good health, that he was not taking any prescription medications at the time of the accident, and that he had not taken any medications that might have affected his performance in the 72 hours before the accident. He stated that he had not drunk alcohol in the last 10 years. The first officer reported no major changes to his health, financial situation, or personal life in the last year. A US Airways check airman who had flown with the first officer for the first officer’s operating experience in January 2009 described him as a very good pilot.

1.5.2.1 The First Officer’s 72-Hour History

From January 9 through 11, 2009, the first officer was off duty at his home in Madison, Wisconsin. He stated that he typically needed about 7 hours of sleep to feel rested.

On January 12, the first officer began the 4-day trip sequence with the captain.19 He stated that, after arriving at SFO from CLT at 2119 PST on January 12, he went to sleep about 2300 PST. The first officer could not recall when he awoke on January 13, but he stated that he felt rested. He stated that the layover in Pittsburgh was less than 8 hours and that he did not recall what time he went to bed.

On January 14, the first officer awoke about 0510. He stated that, after flying from PIT to LGA and then back to PIT, the pilots had a long layover in Pittsburgh. He stated that he did not recall when he went to bed. On January 15, the first officer awoke about 0640. He stated that he felt rested and that the quality of his sleep was good. He stated that he did not eat breakfast, which was typical for him. The first officer stated that, after the flight arrived at CLT, he ate at the airport. He stated that after they arrived at LGA, he got off the airplane and performed a walk around. He stated that they had a quick turn at LGA because the flight had arrived late.

1.5.3 The Flight Attendants

Flight attendant A, age 51, was located at the aft-facing, forward jumpseat (outboard). She received her initial ground training on June 22, 1982; her initial extended overwater (EOW)20 training on August 20, 1990; and her last recurrent training on January 31, 2008. Flight attendant B, age 58, was located at the forward-facing, “direct-view” jumpseat (aft, center aisle). She received her initial ground training on September 15, 1970; her initial EOW training on September 18, 1989; and her last recurrent training on July 17, 2008. Flight attendant C, age 57, was located at the aft-facing, forward jumpseat (inboard). She received her initial ground training on February 27, 1980; her initial EOW training on October 17, 1989; and her last recurrent training on January 31, 2008.

1.6 Airplane Information

Table of Contents

1.6.1 General Information

Airbus, the manufacturer of the A320 airplane, is headquartered in Toulouse, France. The A320-100/200 series airplanes were type certificated for operation in the United States by the FAA under a bilateral airworthiness agreement between the United States and French governments. The FAA approved the A320 type certificate (TC) on December 15, 1988. The A320-214 model was approved on December 12, 1996.

The manufacture of the accident airplane was completed by June 15, 1999. The airplane was delivered new to US Airways and was put on its Part 121 operating certificate on August 3, 1999. At the time of the accident, the airplane had accumulated 25,241 total flight hours and 16,299 total cycles.21 The airplane’s last major maintenance inspection was conducted when the airplane had accumulated 24,912 flight hours.

According to the weight and balance manifest provided by US Airways,22 the airplane departed LGA with a takeoff weight of 151,510 pounds,23 which was below the maximum limitation takeoff weight of 151,600 pounds. Assuming a fuel burn of 1,500 pounds during the climb to 3,000 feet and descent at idle thrust, the airplane’s weight when it was ditched on the Hudson River was estimated to be about 150,000 pounds. The corresponding center of gravity (cg) was 31.1 percent mean aerodynamic chord (MAC), which was within the takeoff cg limits of between 18.1 and 39.9 percent MAC.

The airplane was configured with 12 first-class passenger seats; 138 economy-class passenger seats; two cockpit flight crew seats; two cockpit observer seats; and five retractable flight attendant jumpseats. Two wall-mounted, aft-facing jumpseats were located at the left, forward passenger door (1L); a bulkhead-mounted, forward-facing jumpseat was located in the aft aisle; and wall-mounted, aft-facing jumpseats were located on each side of the aft galley.

1.6.2 Airspeed Displays

The airplane was equipped with two primary flight displays (PFD), one located on each pilot’s instrument panel. On the left side of each PFD was an airspeed scale with a grey background and a fixed yellow reference line and triangle. A white scale was overlaid on, and moved in front of, the background and reference line and triangle, indicating airspeed. In addition to the airplane airspeed, the following characteristic and protection speeds, in part, were presented on the airspeed scale (see figure 3):

Green dot speed, which is the airspeed that provides the best lift over drag ratio. If a pilot maintains this airspeed, the airplane will have the maximum range for glided flight. Green dot speed is represented by a green circle on the right side of the airspeed tape.

F speed, which is used as a target speed on approach (not the final approach speed) when the airplane is in CONF 2 or CONF 3.

24

F speed is represented by an “F” on the airspeed scale.

V

LS

,

which is the lowest selectable airspeed providing an appropriate margin to the stall speed. V

LS

is represented by the top of an amber strip along the airspeed scale and is computed by the FAC based on aerodynamic data.

α PROT, which is the alpha-protection speed. α PROT is represented by the top of a black and amber strip along the airspeed scale. The alpha-protection speed corresponds to the angle-of-attack (AOA) at which the alpha-protection mode (see section 1.6.3) becomes active. It varies according to airplane weight and configuration.

α MAX, which is the maximum AOA speed. α MAX is represented by the top of a red strip along the airspeed scale. Maximum AOA speed corresponds to the maximum AOA that may be reached in pitch normal law (see section 1.6.3) and varied according to airplane weight and configuration.

Figure 3. The A320 airspeed scale, including select characteristics and protection speeds.

1.6.3 Flight Envelope Protections

The A320 is a “fly-by-wire” airplane, which means that pilot control inputs on the sidesticks are processed by flight control computers that then send electrical signals to the hydraulic actuators that move the pitch and roll flight control surfaces (the ailerons, spoilers, and elevators).25 The A320 fly-by-wire design incorporates flight envelope protections; the flight computers are designed to prevent exceedence of the safe flight envelope in the pitch-and-roll axes when in “normal law,” which is the normal operating mode of the airplane’s electronic flight control system. Normal law is one of three sets of control laws (the other two control laws are “alternate law” and “direct law”), which are provided according to the status of the computers, peripherals, and hydraulic generation. The airplane cannot be stalled in normal law. According to the Airbus Flight Crew Training Manual, control law is the “relationship between the…PF’s input on the sidestick, and the aircraft’s response,” which determines the handling characteristics of the aircraft.

The A320 flight envelope protections also incorporate a high-AOA protection, which is available from takeoff to landing and is intended, in part, to allow the pilot to pull full aft on the sidestick to achieve and maintain the maximum possible performance while minimizing the risk of stall or loss of control.

Regarding the high-AOA protection, the Airbus Flight Crew Operating Manual (FCOM) stated, in part, that, under normal law, when the AOA becomes greater than a threshold value, the system switches elevator control from flight mode to protection mode, in which the AOA is proportional to sidestick deflection. The AOA will not exceed the allowable maximum even if the pilot gently pulls the sidestick full aft. If the pilot releases the sidestick, the AOA returns to the alpha-protection threshold value and stays there. Under certain conditions, additional features built into the system can attenuate pilot sidestick pitch inputs, preventing the airplane from reaching the maximum AOA.

1.6.4 Low-Speed or -Energy Warning

The A320 also incorporated an aural warning, which was available when the airplane was operating in normal law, to enhance the pilot’s awareness of a low-speed or -energy condition. This warning is only available when the airplane is in CONF 2, CONF 3, or full flaps. The Airbus FCOM states the following:

An aural low-energy “SPEED SPEED SPEED” warning, repeated every 5 seconds, warns the pilot that the aircraft’s energy level is going below a threshold under which he will have to increase thrust, in order to regain a positive flight path angle through pitch control.

However, the low-energy warning is overridden when the airplane is below 100 feet radio altitude or when a GPWS alert is triggered. According to CVR and FDR data, GPWS alerts were triggered repeatedly during the descent, and no low-energy level alert was generated.

1.6.5 Electrical and Hydraulic Systems

The airplane was equipped with two integrated-drive generators (IDG), one mounted on each engine, which normally supply electrical power to the airplane systems. An IDG will only supply electrical power when the N2 speed is about 54 percent or more. The airplane was also equipped with an APU that drives a third, or auxiliary, generator, which can replace the electrical power normally supplied by either IDG.

If both the primary and auxiliary power sources are lost, a ram air turbine (RAT) contained in a compartment in the left airplane belly fairing supplies hydraulic power to the controlled-speed motor generator, which then provides electrical power to the airplane. During normal conditions, the RAT is retracted into the fuselage and does not operate. When all of the airplane’s electrical power is lost and the airplane has an airspeed greater than 100 knots (kts), the RAT will automatically deploy and begin providing electrical power. The RAT was found in the extended position when the airplane was recovered from the water. Both RAT blades were present, and no major deformation of the blades was observed.

The airplane is equipped with three main hydraulic systems, referred to as green, blue, and yellow, which together supply hydraulic power at 3,000 pounds per square inch (psi) to the airplane’s main hydraulic power users, including the flight controls. The slats are powered by both the green and blue hydraulic systems, and the flaps are powered by both the green and yellow hydraulic systems. The three hydraulic systems are not hydraulically connected.

Each of the three hydraulic systems is pressurized by either an engine-driven or electric motor-driven pump. The blue system’s electric pump supplies hydraulic power when either engine is operating. The green and yellow systems’ engine-driven pumps are connected to the left and right engine, respectively, and these pumps supply hydraulic power when their respective engine is operating. The engine-driven hydraulic pumps are driven by the N2 spool and are able to supply hydraulic pressure as long as the engine is rotating. Generally, the lower the N2 speed, the lower the hydraulic flow that can be delivered by the engine-driven hydraulic pumps.

1.6.6 Engines

The airplane was equipped with two CFM International CFM56-5B4/P dual-rotor, turbofan engines. CFM is a partnership between General Electric Company (GE) in the United States and Société Nationale d’Étude et de Construction de Moteurs d’Aviation (Snecma) in France.26 The CFM engines were jointly certificated under a bilateral agreement between the FAA and the French Direction Générale de L’Aviation Civile (DGAC) in accordance with 14 CFR Part 33 regulations and Joint Aviation Authorities (JAA) Joint Aviation Regulations–Engines (JAR-E) requirements, jointly referred to as Part 33.27 At a minimum, all of the FAA requirements had to be met for certification, and, if a JAA requirement was more stringent than an FAA requirement, then the more stringent standard had to be met for certification. The FAA issued the CFM56-5B4/P engine a domestic TC on June 20, 1996; at that time, Amendment 33-11 to 14 CFR 33.77, “Foreign Object Ingestion,” was the basis for compliance.

The left engine, serial number (S/N) 779-828, was manufactured on September 12, 2000, and installed on the airplane on January 15, 2008. At the time of installation, the left engine had accumulated 16,233 hours and 11,897 cycles since new (CSN). At the time of the accident, the left engine had accumulated 19,182 hours, 13,125 CSN, and 2,949 flight hours since its last maintenance inspection.

The right engine, S/N 779-776, was manufactured on February 16, 2001, and installed on the airplane on May 28, 2006. At the time of installation, the right engine had accumulated 17,916 hours and 6,755 CSN. At the time of the accident, the right engine had accumulated 26,466 hours, 10,340 CSN, and 8,550 flight hours since its last maintenance inspection. The CFM56-5B4/P engine comprises an inlet area, which contains a gas-turbine-driven ducted fan; a 5-stage,28 low-pressure compressor (LPC) (also referred to as the “booster”); a 9-stage, high-pressure compressor (HPC); a combustor; a single-stage, high-pressure turbine (HPT); a 4-stage, low-pressure turbine (LPT);29 and an exit exhaust nozzle. Figure 4 shows a cutaway of a turbofan engine.

Figure 4. Cutaway of a turbofan engine showing the LPC, HPC, combustor, HPT, and LPT.

The ducted fan comprises a two-piece spinner with an aluminum alloy front cone and rear frustum. The rear frustum is bolted to the fan disk and is part of the fan blade retention system. Thirty-six titanium fan blades, which incorporate a midspan damper for support, are installed into the fan disk. A steel alloy fan inlet case, which is designed to contain a failed fan blade and any associated debris, is bolted to the fan frame structure and the fan cowl inner barrel.

Sixty-eight fan outlet guide vanes (OGV) are located between the rotor and the frame struts within the fan inlet case and are designed to direct the secondary airflow to the bypass duct. The inner surface of the fan inlet case is lined with 6 forward acoustical panels, 1 shroud, 6 midacoustical panels, and 12 aft-acoustical panels.

Air enters the engine inlet area, passes through the ducted fan, and is then channeled to two distinct flow paths. Most of the air bypasses the engine core and is directed through the bypass duct, providing about 70 percent of the engine’s overall thrust. The remaining air enters the engine core, where it is compressed; mixed with fuel; combusted; expanded through the LPT, providing rotational power to the fan; and then exhausted, supplying about 30 percent of the engine’s overall thrust. Figure 5 shows the two airflow paths through the turbofan engine.

Figure 5. A diagram showing the two airflow paths through the turbofan engine.

A bird may strike any part of the engine inlet area. If a bird enters the inlet near the outer radius, it will most likely strike only the fan blades, continue along the bypass duct, and be ejected at the rear of the engine. In this case, the fan blades may exhibit some form of leading edge impact damage and may bend and fracture. Debris continuing downstream can damage the bypass duct and fan OGVs. All of this damage negatively affects thrust production; however, typically, the engine will still be able to operate at a lower thrust level.

If a bird enters the inlet near the inner radius close to the spinner, a portion of the bird may be ingested by the engine core, possibly damaging the internal components, including the inlet guide vanes (IGV), LPC and HPC vanes and blades, or the combustor. If the damage is sufficient, the engine may stall or flame out,30 rendering it unable to produce appreciable thrust. (See section 1.12.2 for information about the damage sustained by both engines as a result of the bird strike.)

1.6.6.1 Bird-Ingestion Certification Requirements

1.6.6.1.1 Requirements at the Time of Certification

As noted, 14 CFR Part 33 regulations contain the airworthiness standards that engines are required to comply with to obtain an FAA TC. The aircraft engine certification process consists of many certification tests or analyses that demonstrate that the engine is compliant with its TC basis, and the TC is issued upon successful completion of all of the certification requirements.

As noted, the CFM56-5B4/P engine was certificated in 1996; at that time, the engine had to meet the bird-ingestion requirements contained in 14 CFR 33.77, “Foreign Object Ingestion,” Amendment 33-11,31 which included bird-ingestion requirements that had been added on March 26, 1984, with the issuance of Amendment 33-10. Section 33.77 stated, in part, the following:

(a) Ingestion of a 4-pound [large-sized] bird …may not cause the engine to—

(1) Catch fire;

(2) Burst (release hazardous fragments through the engine case);

(3) Generate loads greater than those specified in Sec. 33.23(a);32 or

(4) Lose the capability of being shut down.

(b) Ingestion of 3-ounce birds or 1 1/2-pound [medium-sized] birds33…may not—

(1) Cause more than a sustained 25 percent power or thrust loss;

(2) Require the engine to be shut down within 5 minutes from time of ingestion; or

(3) Result in a potentially hazardous34 condition.

According to Section 33.77, the medium bird-ingestion criterion for CFM56-5B4/P-sized engines was seven, 1 1/2-pound birds volleyed35 into critical areas of the engine (two birds were volleyed into the engine core area, and five birds were volleyed into the fan blade area at midspan, outer panel, and two intermediate locations) in rapid sequence to simulate a flock encounter. The large-bird ingestion criterion for CFM56-5B4/P-sized engines was a single, 4-pound bird volleyed into a critical area of the fan but not in the core area.

To comply with these requirements, the CFM56-5B4/P engine was subjected to a medium-bird test, which was intended to test the fan blades, structure, and core machinery for resistance to impact from, and ingestion of, multiple medium-sized birds. The engine was also subjected to a large-bird test, which was intended to test the fan blades, flammable fluid lines, and support structure for resistance to impact from, and ingestion of, a single, large bird. These tests were performed with the engine at 100-percent takeoff power.

A December 15, 1992, test report stated that, during the medium-bird ingestion test, the CFM56-5B4/P engine continued to operate with no more than a 25-percent loss of thrust for 5 minutes after the bird ingestion and demonstrated no hazard to the aircraft and no change in handling characteristics after the birds were ingested. The report stated that the engine met the medium-bird test requirements, and the FAA and the DGAC jointly approved the report.

An August 25, 1992, test report stated that, during the large-bird ingestion test, the CFM56-5B4/P engine did not release hazardous fragments, the fan imbalance was negligible, and the test generated lower loads and fan blade distress than the fan blade-out test.36 The report stated that the engine met the large-bird test requirements, and the FAA and the DGAC jointly approved the report.

In early 1993, additional tests were conducted to comply with DGAC CFM56-5B1/-5B2-5B4 Special Condition No. 1,37