National Transportation Safety Board
Office of Public Affairs
National Transportation Safety Board Chairman Jim Hall today issued the following statement on the investigation of the crash of Alaska Airlines flight 261:
The Safety Board's investigation of the January 31 crash of Alaska Airlines flight 261 is continuing. The field investigation phase was completed on March 16. The NTSB Command Post at Port Hueneme, California, was closed this week.
Wreckage recovery was completed on March 15. Here is a summary of that effort:
Following sonar and video mapping of the wreckage debris field (approximately the dimensions of a football field, about 700 feet below the surface of the ocean), U.S. Navy Supervisor of Salvage and Diving personnel and assets began the recovery of wreckage and human remains using a remotely operated vehicle (ROV) on February 2. This water is too deep for divers.
After these recovery operations were completed on March 8, the trawler Sea Clipper (home port San Francisco) began trawling for additional wreckage. Sea Clipper used sole nuts with 5-inch grid for initial trawling for four days and then trawled the same areas with shrimp nets with a grid of 1 1/2 inches for the final four days of the recovery.
As a result of all of these operations, approximately 90 percent of the wreckage has been recovered. When the initial recovery plan was drawn up, we anticipated recovering about 65 percent. All of the major components of the tail section are among the recovered pieces. A portion of the top of the fairing that is located just above the horizontal stabilizer has not been located.
You will recall that the Navy searched for a week in an area about 4 miles from the main wreckage site for any pieces that might have come off the aircraft in flight. Radar had shown primary hits that might indicate such as in-flight separation. Nothing was found during the search.
As I've previously reported, the jackscrew/gimbal nut assemblies - which control the movement of the horizontal stabilizer - from the accident aircraft and eight other aircraft from various operators were received by our laboratory in Washington for metallurgical examination.
The thread on the accident gimbal nut is missing, and remnant strips of the thread were wrapped around the jackscrew. No determination has been made as to whether this damage occurred before or after the aircraft's impact with the ocean's surface. No grease was found on the portion of the jackscrew where the gimbal nut would normally be expected to operate.
The eight other assemblies had been removed from airlines during FAA mandated post-accident inspections because of excessive end play or the presence of metal shavings. They have various amounts of end play as a result of wear of the nuts. Grease samples have been delivered to a Navy lab for analysis and testing.
We also received for comparative purposes five additional Alaska Airlines gimbal nuts that had been rejected because of excessive wear during overhauls conducted prior to the accident.
Laboratory work will continue for at least several more weeks.
The Medical Examiner of Ventura County reports that the remains of 58 of the 88 victims on the aircraft have been identified. The families of all 58 persons have been notified, according to the Medical Examiner. DNA testing is on-going to identify the remaining victims.
Although the field phase of the investigation has been completed, the Safety Board has many on-going investigative activities. Beyond the metallurgical examinations, teardown examinations of other airplane system components that have been recovered from the ocean are scheduled for April. These include primary and alternate trim motors, the gear box the both of these motors were mounted on, trim power relays and trim control switches.
The investigation's Maintenance Records Group will travel to Oakland, California to conduct additional interviews with Alaska Airlines maintenance personnel. At the same time, the Aircraft Performance Group will be continuing to gather data for its analysis of accident dynamics.
Because I have been asked this question more than once, the current strike at Boeing Aircraft Company has not impacted the progress of this investigation because the former McDonnell Douglas engineers who now work for Boeing are not involved in the strike.
I will keep you apprised of further developments as events warrant.
NTSB Media Contact:
Terry N. Williams
The National Transportation Safety Board (NTSB) is an independent federal agency charged with determining the probable cause
of transportation accidents, promoting transportation safety, and assisting victims of transportation accidents and their families.