Detailed Investigation Report: Alaska Airlines Flight 261 Accident

The report analyzes the tragic crash of Alaska Airlines Flight 261, a McDonnell Douglas MD-83, which occurred on January 31, 2000. The flight, AS261, experienced a catastrophic failure of the horizontal stabilizer trim system due to worn-out threads on the jackscrew, caused by inadequate lubrication. The report details the flight's final moments, including the crew's attempts to regain control, and the subsequent crash into the Pacific Ocean. It examines causal factors, including maintenance failures related to lubrication intervals and discrepancies between maintenance manuals and practices. Personnel information, including details about the captain and first officer, is provided. The report also includes recommendations for pilots, management, and engineers to prevent similar accidents in the future, such as improved maintenance procedures, fail-safe mechanisms, and enhanced pilot training. The report references several sources including NTSB reports and cockpit voice recordings. The report concludes with professional recommendations for pilots, management, and engineers to prevent similar accidents.

N963AS Alaska
Airlines Flight 261

Airline Specifications
Status: Final
Date: 31st January, 2000 (Monday)
Time: 16:20
Flight Type: McDonnell Douglas DC-9-83 (MD-83)
Flight Number: AS261
First Flight: 1992
Crew: 5 Fatalities: 5
Passengers: 88 Fatalities: 88
Aircraft Damage: Destroyed beyond repair
Departure Airport: Puerto Vallarta-Gustavo D. Ordaz Airport, Mexico
Destination Airport: San Francisco International Airport, California

Last Minutes of Flight 261
Crew reports a
problem with
horizontal stabiliser
Request diversion
to Los Angeles
airport
Stabiliser trim
worsens, and plane
makes its first
nosedive
Pilots regain
control, jet
stabilises again
Aircraft experiences
sudden loss of
control
Aircraft inverted,
radar contact is lost
Witnesses see the
plane spinning nose
down, in
continuous roll

Details of accident
The McDonnell Douglas MD-83 N963AS crashed into the Pacific Ocean an estimate of a 2.7 miles from the
coast of Anacapa Island in California. In the flight there were 2 pilots, 3 cabin crewmembers along with 83 passengers
who were all killed in the crash and the airplane was destroyed on impact.
On the way to San Francisco, the crew had radioed to the air traffic control tower in Los Angeles saying that
they were having issues with controlling the plane, and that they were descending. After a few minutes, the crew
reported another problem with the jammed stabilizer for which they were granted a FL200-FL250 block altitude
clearance.
The crew was still reporting problems with maintaining correct altitude and made the decision to land in
LAX. While trying to troubleshoot the problem during the descend, the situation got worse and the caused the plane
to pitch nose-down and was seen spinning and tumbling out of control while inverted before they crashed into 650
feet deep water.

Causal Factors
The loss of the pitch of the airplane occurred due to the
failure of the in-flight horizontal stabilizer trim system
jackscrew’s acme nut threads.
Details of accident
Failure of Maintenance Practices
The worn out threads on the jackscrew is caused by excessive
wear, resulting from inappropriate level of lubrications of the
assembly of the jackscrew.

Details of accident
Causal Factors
A period of extended interval for lubrication that was approved by the Federal Aviation Administrations (FAA), which
caused the increase in chances of wear in the threads of the jackscrew.
Failure of Maintenance Practices
General Maintenance Manual does not reflect the same procedures as the one that Alaskan Airlines has in place to
perform maintenance on its airplanes, which increases the probability of errors to occur.

Details of accident
Lead mechanic and inspector signed off
on the planned action which states,
“Replace nut and perform E.O. 8-55-10-
01.”
But the replacement was not done.

Personnel Information
The Captain
The captain was 53 years old and he was first hired by JetAmerica in 1982. Before flying the Alaskan Airline, he had
already achieved almost 18,000 hours of flying hours. He had his last proficiency check only three months before the
accident. He has a clean driving and flying record with no past dealings with accidents or disciplinary actions.
Ted Thompson
The First Officer
The first officer was 57 years old who started working with Alaska Airlines in 1985. He had recorded more than 8000
total flight hours. His last proficiency test was last done 9 months before the accident. He also has no record of
misdemeanour in his record.
William (Bill) Tansky

Air Traffic Control Recording

Black Box Recording of Cockpit
Pilots realise that there could possibly be
a malfunction in the horizontal stabilizer
along with a possible diversion to LAX.

Black Box Recording of Cockpit
The airplane lost control of its stabilizer and went for its first nosedive that the
pilots were able to manage.
The pilots make their first announcement on the PA system in the airplane to
let the passengers know what had just happened, and what they were
planning to do.
The plane went in a nosedive again and the pilots tried to get control of the situation, but
ended up being suspended inverted in the sky.

Professional Recommendation
For pilots in the case of an airplane malfunction:
• Only complete checklist procedures and not attempt to correct any actions beyond the ones that is
specified.
• Both primary and alternate trim system should not be activated.
• Land at the nearest suitable airport.
For management offices and inspectors:
• Be able to provide appropriate support to the pilots who are experiencing systems malfunction that is
threatening the safety of the flight.

Professional Recommendation
For all operators of Douglas DC-9, McDonnell Douglas MD-80/90, and Boeing 717 series airplanes:
• Remove degraded grease from the jackscrews and flush the grease before applying fresh grease.
• Increase the size of access panels which are required to accomplish the assembly of the jackscrew
lubrication process.
Review and Evaluation:
• All existing maintenance intervals which could affect the components of the aircrafts
• Focus on the ones that were extended without a justified engineering reasoning for the extension

Professional Recommendation
For engineers:
• Identify means by which damage can be managed if there is a acme nut thread failure in the stabilizer
system.
• Install fail-safe mechanisms for the future

References:
•Woltjer, R., & Hollnagel, E. (2007). The Alaska Airlines flight 261 accident: a systemic analysis of
functional resonance. In International Symposium on Aviation Psychology (p. 763).
•Aviation Accident Report AAR-02-01. (2002). Retrieved from https://
www.ntsb.gov/investigations/accidentreports/pages/aar0201.aspx
•Alaska Airlines 261 CVR Transcript. (2000). Retrieved from https://www.tailstrike.com/310100.htm
•Zotova, I. (2017). Post-crash airline pricing: A case study of Alaska Airlines Flight 261. Economics of
transportation, 10, 18-22.
•Garcia, C. R., Gomes, G. G., Costa, L. Z. D., & Almeida, V. C. V. D. (2018). Just culture: a study on how to
improve risk mitigation by applying a just culture in an airline line-maintenance enviornment.
•Pardede, A. (2015). An Analysis of Speech Act Based on the Recorded Conversation Transcription of the
Black Box before the Air Plane Crashes.

Thank
you!