Northwest Airlines Flight 85
N661US, the aircraft involved in the accident
|Date||October 9, 2002|
|Summary||Rudder hardover due to metal fatigue|
|Aircraft type||Boeing 747-451|
|Flight origin||Detroit Metropolitan Wayne County Airport|
|Destination||New Tokyo International Airport|
Northwest Airlines Flight 85 was a scheduled international passenger flight from Detroit Metropolitan Wayne County Airport in the United States to Narita International Airport in Japan. On October 9, 2002, the Boeing 747-400 carrying out the flight experienced a lower rudder hardover event, when the flight was in proximity to Anchorage, Alaska. A rudder hardover is when the aircraft's rudder deflects to its travel limit without crew input. The 747's hardover gave full left lower rudder, requiring the pilots to use full right upper rudder and right aileron to maintain attitude and course.
The flight diverted to Ted Stevens Anchorage International Airport. No passengers or crew were injured, but the incident resulted in an airworthiness directive to prevent the possibility of a future accident.
The aircraft involved was the first prototype Boeing 747-400 (Boeing 747-451, c/n 23719, reg N661US) and was built by Boeing for flight testing as N401PW, before subsequently being re-registered as N661US and delivered to Northwest Airlines (the launch customer for the 747-400) on December 8, 1989.
The flight departed Detroit Metropolitan Wayne County Airport at 2:30 PM Eastern Daylight Time. The incident occurred at 5:40 PM Alaska Daylight Time, around 7 hours into the flight. At the time of the incident, Junior Captain Frank Geib and First Officer Mike Fagan had just taken control of the aircraft, allowing Senior Captain John Hanson and First Officer David Smith to rest. Flight 85's captain said that the event occurred at flight level 350 (35,000 feet/11,000 meters).
The aircraft abruptly went into a 30 to 40 degree left bank. Geib initially believed that an engine failure had occurred. Hanson re-entered the cockpit, and continued to fly the aircraft by hand with Fagan. Geib declared an emergency and began a diversion to Anchorage. While trying to declare the emergency, the plane was in a communications dead zone between North America and Asia. Even with a weak signal, they contacted another Northwest Airlines flight, Flight 19, who helped Flight 85 declare the emergency since they were closer to Alaska. Flight 85's captain reported that none of the emergency procedures available could correct the problem. The pilots established a conference call with Northwest Airlines at the Minneapolis-St. Paul area, and the Northwest employees there were unable to find a solution to the sudden bank. The flight crew took back control of the aircraft and landed at Ted Stevens Anchorage International Airport. In order to steer the aircraft they had to use asymmetric engine thrust, or varying input into the engines; they were unable to use the ailerons at the time.
Hanson said that crew resource management (CRM) contributed to the flight's safe landing at Anchorage; he said "This was a classic application of CRM. We were blessed and lucky that we had full flight crew augmentation. We had four pilots to work together in the cockpit. We had an excellent group of flight attendants on board; that became important later because we briefed this as a ‘red’ emergency, which means there’s at least a solid chance you’re going to have to evacuate. We weren’t sure we were going to be able to keep the airplane on the runway." The incident did not initially receive media attention.
The National Transportation Safety Board (NTSB) and Boeing launched investigations into the incident. NTSB investigator Carolyn Deforge, who had overseen the investigation of NW85, recounted on the television program Mayday (Air Crash Investigation, Air Emergency) "it appeared to be a very dramatic event, and ... it definitively seemed like something we needed to follow up on, trying to understand what had happened."
The NTSB found that there was a fatigue crack in the power control module, and that it was not possible to visually inspect that type of failure. The lower rudder control module's cast metal housing had broken. The end portion of the control module housing which housed the yaw damper actuator had separated from the main portion of the housing. Deforge said in the Mayday episode that the NW85 failure was an unusual failure since most failures are of internal components rather than the housing itself.
The NTSB ruled that the probable cause was a "fatigue fracture of the lower rudder power control module manifold, which resulted in a lower rudder hardover." In a rudder hardover the rudder is driven to its full deflection and stays there.
A non-destructive inspection process for the module was developed. As a result, Boeing issued Alert Service Bulletin 747-27A2397. The bulletin, dated July 24, 2003, recommended that Boeing 747 operators conduct ultrasonic inspections of pertinent high-time lower and upper rudder power control modules.
The Federal Aviation Administration (FAA) published a Notice of Proposed Rule Making (NPRM) for an airworthiness directive that would make this inspection mandatory on Boeing 747-400, 400D, and 400F aircraft. The "Airworthiness Directive; Boeing Model 747-400, -400D, and -400F Series Airplanes" was published in the federal register on August 28, 2003. The directive, labeled Directive 2003-23-01, was issued on November 3, 2003 and became effective December 18, 2003. It has since been superseded by directive 2006-18-17, issued August 30, 2006 and effective October 13, 2006. In 2008 a proposed replacement to this directive was published.
On February 24, 2009 the aircraft involved in the incident, along with the other 747-400s in Northwest Airlines' fleet, joined the Delta Air Lines fleet as part of the Northwest-Delta Air Lines merger. On September 8, 2015, it left Honolulu, Hawaii for its final flight and was retired on arrival at Atlanta, Georgia's Hartsfield–Jackson Atlanta International Airport. It was transferred to the adjacent Delta Flight Museum for public display at the end of April 2016.
- "2002-10-09-US.pdf." (Archive) National Transportation Safety Board. Retrieved on December 23, 2012.
- "ANC03IA001." (Archive) National Transportation Safety Board. Retrieved on December 23, 2012. "the captain said the airplane was at a cruise altitude of 35,000 feet with the autopilot engaged, when it abruptly rolled into a 30 to 40 degree left bank."
- Wallace, James. "Aerospace Notebook: Boeing, NTSB investigating 747 rudder incident." Seattle Post-Intelligencer. Tuesday November 5, 2002. Retrieved on December 25, 2012.
- Steenblik, Jan W. "ALPA's Annual Air Safety Awards." (Archive) Air Line Pilot. Air Line Pilots Association. January 2004, p.19. Retrieved on December 25, 2012.
- "Turning Point." Mayday (Air Crash Investigation, Air Emergency). The investigation information is in the second half of the program, after the end of the incident.
- "NTSB Identification: ANC03IA001." (Archive) National Transportation Safety Board. Retrieved on December 25, 2012.
- "'747 Experience' opens at Delta Flight Museum". Delta News Hub. Retrieved March 28, 2017.
- "Docket No. 2003-NM-173-AD; Amendment 39-13364; AD 2003-23-01." (Archive) Federal Aviation Administration. Retrieved on December 23, 2012.
- "Docket No. 2003-NM-173-AD; Amendment 39-13364; AD 2003-23-01 RIN 2120-AA64." (Archive) Federal Aviation Administration. Retrieved on December 23, 2012.
- "Docket No. FAA-2006-23873; Directorate Identifier 2005-NM-110-AD; Amendment 39-14756; AD 2006-18-17." (Archive) Federal Aviation Administration. Retrieved on December 23, 2012.
- "Docket No. FAA-2006-23873; Directorate Identifier 2005-NM-110-AD; Amendment 39-14756; AD 2006-18-17 RIN 2120-AA64." (Archive) Federal Aviation Administration. Retrieved on December 23, 2012.
- "Federal Register | Airworthiness Directives; Boeing Model 747-400, 747-400D, and 747-400F Series Airplanes". Federalregister.gov. Retrieved December 25, 2012.
- "Federal Register, Volume 68 Issue 167 (Thursday, August 28, 2003)". Gpo.gov. Retrieved December 25, 2012.
- "First Boeing 747-400 takes historic final flight". Delta News Hub. Retrieved September 9, 2015.
- "デルタ航空のボーイング747-400型1号機が引退、来年本社の博物館に展示予定". Delta Airlines Japan Branch News Release. Retrieved September 10, 2015.(in Japanese)
- "Historic Boeing 747-400 moved to the Delta Museum". CNN. Retrieved May 2, 2016.
- "Retired 747-400 takes road trip home to Flight Museum". Delta News Hub. Retrieved May 2, 2016.
- "Turning Point". Mayday. Season 11. 2011. Discovery Channel Canada / National Geographic Channel.
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