physics

Northwest Airlines Flight 85

Northwest Airlines Flight 85 is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Northwest Airlines Flight 85 rather than just read about it. In short: 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, while over the Bering Sea, the Boeing 747-400 experienced a lower rudder hardover event, which occurs when an aircraft's rudder deflects to its travel limit without crew input.

Key takeaways

Northwest Airlines Flight 85 belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Northwest Airlines Flight 85 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Northwest Airlines Flight 85 from memory before moving on to harder problems.

Reference excerpt

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, while over the Bering Sea, the Boeing 747-400 experienced a lower rudder hardover event, which occurs when an 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.

Aircraft

The aircraft involved was the prototype Boeing 747-400 (Boeing 747-451, c/n 23719, reg N661US) and was built by Boeing, and started the flight testing program for the new model, registered as N401PW, in April 1988. It was subsequently reregistered as N661US and delivered to Northwest Airlines (the launch customer for the 747-400) on December 8, 1989. The aircraft was reregistered to Delta Air Lines on October 29, 2008, after Delta and Northwest merged. After a further seven years in service with Delta, N661US was retired in 2015, and was then sent to the Delta Flight Museum for preservation on April 30, 2016.

Incident flight

The flight departed Detroit Metropolitan Wayne County Airport at 2:30 p.m. Eastern Daylight Time. The incident occurred at 5:40 p.m. Alaska Daylight Time, around seven 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 FL350 (35,000 feet/11,000 meters). The aircraft abruptly entered a 30- to 40-degree left bank. Geib initially believed that an engine failure had occurred. Hanson reentered the cockpit and continued to fly the aircraft by hand with Fagan. Geib declared an emergency and began a diversion to Anchorage. While the crew tried to declare the emergency, the plane was in a communications dead zone between North America and Asia. Even with a weak signal, the crew contacted another Northwest Airlines flight, Flight 19, which helped Flight 85 declare the emergency as it was 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 in the Minneapolis-St. Paul area, but the 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. To steer the aircraft, they had to use the ailerons and asymmetric engine thrust, applying more engine power to one side than the other. Hanson said that crew resource management (CRM) contributed to the flight's safe landing at Anchorage:

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.

Investigation The National Transportation Safety Board (NTSB) and Boeing launched investigations into the incident. NTSB investigator Carolyn Deforge, who oversaw the investigation, recounted in an interview on the television program Mayday: "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 that 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 unusual because most failures are of internal components rather than of 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.

Legacy

Boeing 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.

FAA The Federal Aviation Administration published a Notice of Proposed Rule Making for an airworthiness directive that would make ultrasonic inspections 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.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Northwest Airlines Flight 85

Start with the simplest possible case. Write down what Northwest Airlines Flight 85 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Northwest Airlines Flight 85 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Northwest Airlines Flight 85 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Northwest Airlines Flight 85

In research: Northwest Airlines Flight 85 appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Northwest Airlines Flight 85 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Northwest Airlines Flight 85 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 2002 in Alaska, Airliner accidents and incidents caused by mechanical failure, Airliner accidents and incidents in Alaska, so understanding it makes those chapters shorter.
In everyday life: Look for Northwest Airlines Flight 85 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Northwest Airlines Flight 85 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Northwest Airlines Flight 85 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Northwest Airlines Flight 85 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Northwest Airlines Flight 85 in simple terms?

Why does Northwest Airlines Flight 85 matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Northwest Airlines Flight 85?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Northwest Airlines Flight 85.