Alaska Airlines Flight 261 was a scheduled international passenger flight from Licenciado Gustavo Díaz Ordaz International Airport in Puerto Vallarta, Jalisco, Mexico, to Seattle–Tacoma International Airport near Seattle, Washington, United States, with an intermediate stop at San Francisco International Airport in San Francisco, California. On January 31, 2000, the McDonnell Douglas MD-83 operating the flight crashed into the Pacific Ocean roughly 2.7 miles (4.3 km; 2.3 nmi) north of Anacapa Island, California, following a catastrophic loss of pitch control, while attempting to divert to Los Angeles International Airport. The accident killed all 88 on board – two pilots, three cabin crew members, and 83 passengers.
The subsequent investigation by the National Transportation Safety Board (NTSB) determined that inadequate maintenance led to excessive wear and eventual failure of a critical flight control system during flight. The probable cause was stated to be "a loss of airplane pitch control resulting from the in-flight failure of the horizontal stabilizer trim system jackscrew assembly's Acme nut threads." For their efforts to save the plane, both pilots were posthumously awarded the Air Line Pilots Association Gold Medal for Heroism.
Background
Aircraft
The aircraft involved in the accident was a McDonnell Douglas MD-83, serial number 53077, and registered with the tail number N963AS. The MD-83 is a longer-range version of the original MD-80 (an improved version of the DC-9), with higher weight allowances, increased fuel capacity, and more powerful Pratt & Whitney JT8D-219 engines. The aircraft had logged 26,584 flight hours and 14,315 cycles since it was delivered in 1992.
Crew
The pilots of Flight 261 were both highly experienced pilots. Captain Ted Thompson, 53, had accrued 17,750 flight hours, and had more than 4,000 hours experience as pilot-in-command in MD-80s. First Officer William "Bill" Tansky, 57, had accumulated 8,060 hours as first officer on the MD-80. Thompson had flown for Alaska Airlines for eighteen years (since 1981) and Tansky for fifteen (since 1984); neither pilot had been involved in an accident or incident prior to the crash. Both pilots lived in the Greater Los Angeles area and had previous military experience – Thompson in the U.S. Air Force and Tansky in the U.S. Navy. Three Seattle-based flight attendants: Kristin Mills (26), Craig Pulanco (30), and Allison Shanks (33), were also on board, completing the five-person crew.
Passengers
The five crew members and 47 of the passengers on board the plane were bound for Seattle. Of the remaining passengers, 30 were traveling to San Francisco; three were bound for Eugene, Oregon; and three passengers were headed for Fairbanks, Alaska. Of the passengers, one was Mexican and one was British, with all others being U.S. citizens.
At least 35 occupants of Flight 261 were connected in some manner with Alaska Airlines or its sister carrier, Horizon Air, including 12 people directly employed by the company, travelling on free or employee discounted tickets. As is common practice among airlines, off duty employees can sit in seats that would otherwise have been left empty. Employees can also grant the same privilege to their family members or friends. Bouquets of flowers started arriving at the company's headquarters in SeaTac, Washington, the day after the crash.
Notable passengers
- Jean Gandesbery, author of the book Seven Mile Lake: Scenes from a Minnesota Life, died alongside her husband, Robert.
- Cynthia Oti, an investment broker and financial talk show host at San Francisco's KSFO-AM, was killed.
- Tom Stockley, wine columnist for The Seattle Times, died alongside his wife, Margaret.
- Morris Thompson, commissioner of the Bureau of Indian Affairs in Alaska from 1973 to 1976, died alongside his wife, Thelma, and daughter, Sheryl.
Accident flight
Alaska Airlines Flight 261 departed from Puerto Vallarta's Licenciado Gustavo Díaz Ordaz International Airport at 13:37 PST (21:37 UTC), and climbed to its intended cruising altitude of flight level 310 (31,000 feet or 9,400 m). The plane was scheduled to land at San Francisco International Airport (SFO) less than 4 hours later. Sometime before 15:49 (23:49 UTC), the flight crew contacted the airline's dispatch and maintenance-control facilities in SeaTac, Washington, on a company radio frequency shared with operations and maintenance facilities at Los Angeles International Airport (LAX), to discuss a jammed horizontal stabilizer and a possible diversion to LAX. The jammed stabilizer prevented the operation of the trim system, which would normally make slight adjustments to the flight control surfaces to keep the plane stable in flight. At their cruising altitude and speed, the position of the jammed stabilizer required the pilots to pull on their yokes with about 10 lbf (44 N) of force to keep level. Neither the flight crew nor company maintenance could determine the cause of the jam. Repeated attempts to overcome the jam with the primary and alternate trim systems were unsuccessful.
During this time, the flight crew had several discussions with the company dispatcher about whether to divert to LAX or continue on as planned to SFO. Ultimately, the pilots chose to divert. Later, the NTSB found that while "the flight crew's decision to divert the flight to Los Angeles ... was prudent and appropriate," "Alaska Airlines dispatch personnel appear to have attempted to influence the flight crew to continue to San Francisco ... instead of diverting to Los Angeles." Cockpit voice recorder (CVR) transcripts indicate that the dispatcher was concerned about the effect on the schedule ("flow"), should the flight divert.
At 16:09 (00:09 UTC), the flight crew successfully used the primary trim system to unjam the stuck horizontal stabilizer. Upon being freed, however, it quickly moved to an extreme "nose-down" position, forcing the aircraft into a nosedive. The plane dropped from about 31,050 ft (9,460 m) to between 23,000 and 24,000 ft (7,000 and 7,300 m) in around 80 seconds. Both pilots struggled together to regain control of the aircraft, and only by pulling with 130 to 140 lbf (580 to 620 N) on the controls did the flight crew stop the 6,000 ft/min (1,800 m/min) descent of the aircraft and stabilize the MD-83 at roughly 24,400 ft (7,400 m).
Alaska 261 informed air traffic control (ATC) of their control problems. After the flight crew stated their intention to land at LAX, ATC asked whether they wanted to proceed to a lower altitude in preparation for the approach. The captain replied: "I need to get down to about ten, change my configuration, make sure I can control the jet, and I'd like to do that out here over the bay, if I may." Later, during the public hearings into the accident, the request by the pilot not to fly over populated areas was mentioned. During this time, the flight crew considered, and rejected, any further attempts to correct the runaway trim. They descended to a lower altitude, and started to configure the aircraft for landing at LAX.
Beginning at 16:19 (00:19 UTC), the CVR recorded the sounds of at least four distinct "thumps," followed 17 seconds later by an "extremely loud noise," as the overstrained jackscrew assembly failed completely, and the jackscrew separated from the Acme nut holding it in place. As a result, the horizontal stabilizer failed at 17,800 feet (5,400 m), and the aircraft rapidly pitched over into a dive while rolling to the left. The crippled plane had been given a block altitude, and several aircraft in the vicinity had been alerted by ATC to maintain visual contact with the stricken jet. These aircraft immediately contacted the controller. One pilot radioed, "That plane has just started to do a big huge plunge." Another reported, "Yes sir, ah, I concur. He is, uh, definitely in a nose down, uh, position, descending quite rapidly." ATC then tried to contact the plane. The crew of a SkyWest airliner reported, "He's, uh, definitely out of control." Although the CVR captured the co-pilot saying "mayday," no radio communications were received from the flight crew during the final event.
The CVR transcript reveals the pilots' constant attempts for the duration of the dive to regain control of the aircraft. After the jackscrew failed, the plane pitched –70° and was rolling over to the left. Performing an upset recovery maneuver, the captain commanded to "push and roll, push and roll," managing to increase the pitch to –28°, he stated, "ok, we are inverted...and now we gotta get it." Over the next minute, completely inverted and still diving at a –9° pitch, the crew struggled to roll the plane, with the captain calling to "push push push...push the blue side [of the attitude indicator] up," "ok now let's kick rudder...left rudder left rudder," to which the copilot responded, "I can't reach it." The captain then replied, "ok right rudder...right rudder," followed 18 seconds later by: "gotta get it over again...at least upside down we're flying."
Despite the attempt to fly the plane inverted, which almost entirely arrested its descent, the aircraft had lost too much altitude in the dive, and was far beyond recovery. A few seconds before 16:21 (00:21 UTC), Flight 261 hit the Pacific Ocean at high speed between the coastal city of Port Hueneme, California, and Anacapa Island. At this time, pilots from aircraft flying in the vicinity reported in, with one pilot saying, "and he's just hit the water." Another reported, "Ah, yes sir, he, ah, he, ah, hit the water. He's, ah, down." The aircraft was destroyed by the impact forces, and all occupants were killed by blunt-force impact trauma.
Investigation
Wreckage recovery and analysis
The Austin-class amphibious transport dock USS Cleveland (LPD-7) assisted in recovery operations.
Using side-scan sonar, remotely operated vehicles, and a commercial fishing trawler, workers recovered about 85% of the fuselage (including the tail section) and a majority of the wing components. In addition, both engines, as well as the flight data recorder and Cockpit Voice Recorder, were retrieved. All wreckage recovered from the crash site was unloaded at the Seabees' Naval Construction Battalion Center Port Hueneme, California, for examination and documentation by NTSB investigators. Both the horizontal stabilizer trim system jackscrew (also referred to as "acme screw") and the corresponding acme nut, through which the jackscrew turns, were found. The jackscrew was constructed from case-hardened steel and is 22 in (56 cm) long and 1.5 in (3.8 cm) in diameter. The acme nut was constructed from a softer copper alloy containing aluminum, nickel, and bronze. As the jackscrew rotates, it moves up or down through the (fixed) acme nut, and this linear motion moves the horizontal stabilizer for the trim system. Upon subsequent examination, the jackscrew was found to have metallic filaments wrapped around it, which were later determined to be the remains of the acme nut thread.
Later analysis determined that approximately 90% of the thread in the acme nut had already worn away before the flight, and that it ultimately stripped while the aircraft was en route to San Francisco. Once the threads failed, the horizontal stabilizer assembly was exposed to aerodynamic forces beyond its design limits, resulting in its complete failure. Based on the interval since the last inspection of the jackscrew assembly, the NTSB concluded that the acme nut threads had worn at a rate of 0.012 inches (0.30 mm) per 1,000 flight hours – significantly higher than the expected rate of 0.001 inches (0.025 mm) per 1,000 flight hours. During the investigation, the NTSB examined several possible causes for this excessive wear, including Alaska Airlines’ substitution – approved by the manufacturer, McDonnell Douglas – of AeroShell 33 grease in place of the previously specified Mobilgrease 28. However, the use of AeroShell 33 was ultimately determined not to have contributed to the accident. Insufficient lubrication of the components was also considered as a reason for the wear. Examination of the jackscrew and acme nut revealed that no effective lubrication was present on these components at the time of the accident. Ultimately, the lack of lubrication of the acme-nut thread and the resultant excessive wear were determined to be the direct causes of the accident. Both of these circumstances resulted from Alaska Airlines' attempts to cut costs.
Identification of passengers
Due to the extreme impact forces, only a few bodies were found intact, and none were visually identifiable. All passengers were identified using fingerprints, dental records, tattoos, personal items, and anthropological examination.