Chicago, IL, USA
N197AN
BOEING 757-223
While performing the cockpit preflight, the captain noticed that the standby horizon was unpowered. After cycling the Standby Power Selector and the Battery Switch, the captain noted that five status messages were displayed on the engine indicating and crew alert system (EICAS) screen, although he could not remember the specific messages. Maintenance personnel subsequently cleared the messages and told the crew they were "good to go," without making a logbook entry. Approximately 30 minutes after takeoff several cockpit lights flickered; multiple EICAS messages appeared, including the AIR/GRD SYS caution message; the Standby Power OFF light illuminated; the autopilot disconnect warning sounded; and the autothrottles disconnected. The first officer referenced the STANDBY BUS OFF procedure in the QRH, turning the Standby Power selector to the BAT position. The QRH states that when BAT is selected the battery will provide bus power for approximately 30 minutes. Although the QRH did not instruct the crew to divert to the nearest suitable airport, it indicates that the battery will supply bus power for approximately 30 minutes and the captain reported to maintenance that the battery would be depleted. After consulting with company maintenance specialists, the crew elected to continue the flight. Battery power was depleted and numerous essential aircraft systems began to fail about 2 hours and 24 minutes after the flight crew switched the Standby Power selector to the BAT position. These systems included the stabilizer trim, the captain’s instrumentation, thrust reversers, anti-skid and others. The flight diverted to the closest airport, an emergency was declared, and the airplane was cleared to land on the 7,500-foot-long runway; the captain stated that due to problems controlling the airplane, he did not want to circle to land on a longer runway. The airplane touched down hard about 2,500 feet down the runway. The crew determined they were going to overrun the end of the runway, so the captain veered the airplane off the left side of the runway into the grass, where the airplane came to rest with seven of the eight main gear tires either blown out or deflated. Postaccident investigation revealed erosion on the B contacts within the K106 relay; a failure of the K106 electrical relay would result in the events described by the crew.
HISTORY OF FLIGHT On September 22, 2008, at 1342 central daylight time, a Boeing 757-223, N197AN, operated by American Airlines as flight 268, overran the side of Runway 22R (7,500 feet by 150 feet), while landing at the O’Hare International Airport (ORD), Chicago, Illinois. There were no injuries to the 2 flight crewmembers, 5 flight attendants, and 185 passengers. The airplane received minor damage to the landing gear. The scheduled domestic passenger flight was being operated under the provisions of Title 14 Code of Federal Regulations Part 121. Visual meteorological conditions prevailed and the flight was operating on an instrument flight rules flight plan. The flight originated from the Seattle-Tacoma International Airport (SEA), Seattle, Washington, at 0801 pacific daylight time, with an intended destination of the John F. Kennedy International Airport (JFK), New York, New York. (All times are central daylight unless noted.) The captain reported that prior to takeoff from SEA, he noticed that the standby horizon had tumbled with the flags in view and that it was unpowered. He turned the Standby Power Selector Off and On followed by turning the Battery Switch Off and On. The standby horizon righted itself and the flags disappeared. He noticed five status messages displayed on the lower engine indicating and crew alert system (EICAS) screen; however, he could not recall what the messages were. He then called maintenance to report the messages. A mechanic came into the cockpit, cleared the messages, and stated that they were “good to go.” No logbook entries were made regarding this event. The flight crew reported that just prior to leveling off at flight level (FL) 370, some cockpit lights flickered, multiple EICAS messages appeared including an AIR/GRD SYS caution message, and the Standby Power OFF light illuminated. In addition, the autopilot disconnect warning sounded and the autothrottles disconnected and the captain reported the autopilot began to act “squirrely”. According to the flight data recorder (FDR), electrical system anomalies began at 10:25:35, when the battery voltage spiked to approximately 31 volts direct current (VDC). The first officer referred to the quick reference handbook (QRH) regarding the AIR/GND SYS message. The flight crew then followed the procedure for STANDBY BUS OFF as referenced in the QRH, turning the Standby Power selector to the BAT position. The second step did not apply to their situation, so they stopped the checklist with the Standby Power selector in the BAT position. This QRH procedure also stated, “The battery will provide bus power for approximately 30 minutes.” The DISCHARGE light remained illuminated. The captain reported that he looked at the list of items on the page that may be inoperative with the standby bus unpowered. At 10:30:55, according to the FDR, the main battery discharge indicated “discharge” and the main battery voltage began to decrease. The first officer then performed the QRH Main Battery Charger checklist, which tests the main battery charger. The crew determined that this QRH procedure did not apply to the situation and they did not complete the checklist. The procedure stated that the battery discharge light should not be illuminated, but it was. The captain reported the airplane appeared to be stabilized with the Standby Power Selector in the BAT position. The captain contacted American Airlines maintenance technical support (Tulsa Tech) twice and subsequently elected to continue the flight on battery power. Conversation regarding the electrical anomalies between the captain and first officer continued throughout the flight. At 12:54:38, a sound similar to the master caution warning was heard on the cockpit voice recorder (CVR). The FDR indicated that this was around the time that battery power was depleted; approximately 2 hours 24 minutes after the flight crew switched the Standby Power selector to the BAT position. The first officer stated the first indication of a problem was that the auto-throttle light illuminated, the auto-throttles disconnected, and the autopilot became “squirrelly.” According to the captain, numerous cockpit systems then began to fail. At 12:57:35, the captain stated, “…I’ve lost my whole side here.” The captain then told the first officer, “…everything’s working on your side so you got the airplane the rest of the leg.” At 13:15:48, the captain contacted American Airlines dispatch stating that the electrical problems they were experiencing were getting worse and they needed to divert to ORD. The captain contacted the Chicago Air route Traffic Control Center (ARTCC) stating that they needed to divert to ORD because of electrical problems. The controller cleared the airplane to ORD via radar vectors and cleared the airplane to begin a descent. The airplane was over western Michigan at this time. It was around this time that the flight attendants discovered the public address (PA) system and the interphone were inoperative. The number one flight attendant wrote a note and slipped it under the cockpit door informing the flight crew of their communication problems. A short time later, the captain opened the cockpit door and told the flight attendants that they were diverting to ORD. One of the flight attendants then walked through the aisle informing the passengers of the unscheduled landing. At 13:20:39, the ARTCC controller asked the flight crew if they needed any assistance. The captain replied that they were alright. He stated that more than one electrical system had failed and it appeared everything was functioning, but their backups were “going away.” He also informed the controller that they were unable to fly an instrument landing system (ILS) approach. The controller continued to issue radar vectors to the airport and descents. At 13:22:02, the captain tried to make a PA announcement informing the passengers that they had an “electrical complication” and they were diverting to ORD. He was not aware whether or not the PA system was working. At 13:32:04, the captain contacted ORD approach control stating they were at 10,000 feet and slowing down. He stated they had “almost no indications in the cockpit” and emergency equipment was not required. The first officer reported the captain’s instruments were all inoperative and that he was flying the airplane. As the airplane decelerated, the first officer realized the main stabilizer trim and the alternate stabilizer trim were inoperative. He stated he had a “hand full of airplane.” At 13:39:18, the captain reporting having the airport in sight. The local controller then cleared the airplane for the visual approach to Runway 22R. At 13:39:53, the first officer stated, “we’re close to being an emergency right now. We don’t have trim.” At 13:40:25, the captain declared an emergency. The controller cleared the airplane to land and stated that emergency crews were on standby. The captain then assisted the first officer on the flight controls and they continued the landing approach. The captain reported that the systems they needed to slow the airplane on the runway appeared normal, and because of the flight control issues they did not want to perform a go-around and land on a longer runway. The captain reported it was very difficult to maintain pitch control of the airplane, so he stopped the flap extension at 20. The captain reported they made a good landing, but the nose of the airplane touched down a “little firmer than I cared for.” The first officer selected reverse thrust, but nothing happened. The captain stated the spoilers were armed, but they did not automatically deploy. He reported he manually deployed the spoilers, but still was not sure if they deployed. The first officer reported that he applied the brakes, but they were insufficient and did not feel normal. The captain reported he was concerned about the brake function and accumulator pressure, so he made one smooth application of the brakes, which did not “perform well.” Due to obstructions off the end of the runway, the captain elected to veer the airplane off the left side of the runway into the grass. Airport personnel and firefighters who witnessed the landing reported the airplane appeared to be fast and it touched down approximately 2,500 feet down the runway, near the intersection of taxiway Papa. They reported the airplane touched down hard, and they heard several loud “pops” when the airplane contacted the runway. Skid marks from the left main gear began near the point of touchdown, followed 165 feet later by skid marks from the right main gear. These skid marks were visible for the entire length of the runway up until the airplane departed the pavement. The airplane came to rest with all three landing gear off the left side of the pavement. The nose of the airplane came to rest approximately 100 feet prior to the end of the blast pad pavement which extended 397 feet past the departure end of the runway. After coming to a stop, the flight crew was not able to shut the engines down with either the fuel cutoff valves or by activating the fire handles. Airport firefighting and rescue (ARFF) personnel, and American Airlines maintenance personnel boarded the airplane. The engines were subsequently shutdown by depressing the fire handles and recycling the generator control switch. Once the engines were shut down, the passengers were deplaned through the L1 and R3 doors using portable stairs. DAMAGE TO AIRCRAFT Damage to the airplane was confined to the landing gear. Seven of the eight main landing gear tires were either blown out or deflated during the landing. PERSONNEL INFORMATION The captain, age 50, held an airline transport pilot certificate with an airplane multi-engine rating and commercial privileges for single-engine land airplanes. He also held type ratings for B-757 and B-767 airplanes, and a certified flight instructor certificate, issued February 21, 2008, with a single engine land rating. In addition, the captain held a flight engineer certificate which contained a turbojet rating, and a mechanic’s certificate with airframe and powerplant ratings. The captain was issued a first-class medical certificate on August 13, 2008. The medical certificate contained the limitation “must have available glasses for near vision.” The captain reported having a total flight time of 11,285 hours, 580 of which were in B-757 airplanes. The captain was hired by Ozark Airlines on June 24, 1985. He was furloughed after about a year. He was then recalled and flew B-727 airplanes. When Ozark Airlines was purchased by TWA, he continued to fly B-727s for TWA. He then became a ground school and simulator instructor on MD-80, B-727, and B-757/767 airplanes. He began working for American Airlines during the TWA/American merger in 2001. The first officer, age 49, held an airline transport pilot certificate with an airplane multi-engine rating. He held type ratings for B-707, B-720, B-757, B-767, CL-65, and DC-9 airplanes. The first officer also held a flight engineer certificate which contained a Turbojet rating. The first officer was issued a first-class medical certificate on June 2, 2008. The medical certificate contained the limitation “must have available glasses for near vision.” The first officer reported having a total flight time of 11,700 hours, 1,635 of which were in B-757 airplanes. The first officer was hired by TWA on October 7, 1988, and has flown for American Airlines since the TWA/American merger in 2001. While flying for TWA, he was a flight engineer on B-727 airplanes and a first officer on DC-9, MD-80, and B-757/767 airplanes. He was also a captain on MD-80s. While employed by American Airlines, he flew as first officer on the MD-80 and as captain on the CRJ (American Eagle) and MD-80. The incident occurred on his first trip sequence at American Airlines as a first officer on the B-757. The first officer had been displaced from being a MD-80 captain because of seniority issues. The incident occurred on the second day of a four day trip. AIRCRAFT INFORMATION The airplane, a Boeing 757-223, serial number 32391, was manufactured on November 1, 2001. The airplane was configured to carry 197 people: 2 flight crewmembers, 7 flight attendants, and 188 passengers. American Airlines added the airplane to their operating certificate on December 3, 2001. At the time of the incident, the airplane had accumulated a total time of 22,094 hours with 7,474 total cycles. The airplane was equipped with two Rolls Royce RB211-53 turbofan engines and a Honeywell Auxiliary Power Unit (APU). At the time of the incident, the number 1 engine had a total time of 50,909 hours with 16,369 cycles, and the number 2 engine had a total time of 22,094 hours with 7,474 cycles. The APU had accumulated a total time of 38,303 hours with 13,740 cycles. Electrical System The electrical system consists of a 115 volt alternating current (AC) system and a 28 volt direct current (DC) system. The AC power is supplied by two integrated driver generators (IDGs), one driven by each engine. The APU provides in-flight backup to the IDGs. The system is controlled by three generator control units and one bus power control unit (BPCU). Two main 28 volt DC power channels are supplied by two transformer rectifier units (TRUs). The TRU convert main 115 volt AC power to 28 volt DC power. The main battery and its charger provide a backup source for the standby power system. The battery/standby power electrical system can supply DC and AC power to selected flight instruments, communications and navigation systems, and other critical systems, if there are AC and DC electrical power system failures. The battery/standby power system consists of the following buses: Hot Battery bus, Battery bus, Standby DC bus, and the Standby AC bus. The aircraft schematic diagrams show that when the standby power selector is in the BAT position, the main battery is the sole source of power for these busses. In addition, the main battery charger is unpowered, and the battery will not be recharged. Maintenance Records The airplane was maintained on a Continuous Airworthiness Maintenance Program (CAMP). The last Service Check performed on the airplane was accomplished on September 21, 2008. The last A Check/Periodic Check was performed on September 20, 2008. The last B Check was performed on September 6, 2008, and the last Light/Heavy C Check was performed on June 27, 2007, at an aircraft total time of 17,963 hours. A review of the aircraft logbook for the month of September showed several discrepancies regarding the aircraft’s electrical system. Those included: 9/15/08 Flight attendant reported that all cabins lights (including emergency lights) flashed several times on takeoff. Action Taken: Replaced transfer relay K102. 9/17/08 Aft Cargo DET 2 message. Action Taken: Performed Eng/APU/Cargo fire detection test. Normal. 9/18/08 No hot water in aft left lav. Action Taken: Reset water heater. 9/18/08 No hot water in aft right lav. Action Taken: Reset water heater. 9/19/08 Aircraft will not accept external power. Action Taken: Reset BPCU. 9/19/08 Emergency lights in aft galley blinking. Action Taken: Operational Check OK. 9/20/08 Emergency light on in-flight. Can’t turn them off. Action taken: Performed light test. Could not duplicate. 9/20/08 Emergency lights blinking during takeoff. Action Taken: Replaced broken light bulb and performed light adjustment test. 9/21/08 Emergency lights on then off 3 minutes later. Action Taken: Replaced MOD5537 at M10801. 9/22/08 At FL370 numerous electrical anomalies occurred including the left reverser caution light, standby altitude indicator, battery discharge light, the autopilot and autothrottles disconnected and aircraft started a left roll. Two pages of master cautions appeared along with several status messages. Action Taken: Replaced BPCU. Between September 2007 and the incident, there were 15 entries
The failure of an electrical relay due to eroded contacts and the flight crew's decision to continue a flight that was operating on battery power.
Source: NTSB Aviation Accident Database
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