Boeing 737 rudder issues

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Starting in 1991, a number of accidents/incidents involving the Boeing 737 was the result of the airplanes' unexpected movement of its rudder. The rudder is controlled by the Power Control Unit (PCU). Inside the PCU is a dual servo valve which help directs hydraulic fluid in order to move the rudder. The PCU is manufactured by Parker Hannifin.

1 Accidents
2 Other 737 Rudder related/suspected accidents/incidents
3 SilkAir controversy
4 Boeing 737 rudder upgrade directive
5 See also
6 References
7 External links

[edit] Accidents

March 3, 1991: United Airlines Flight 585 crashed in Colorado Springs, CO killing 25 people.

Sept 8, 1994: USAir Flight 427 crashed in Pittsburgh, PA killing 132 people.

During the course of the investigation of Flight 427 the NTSB discovered that the PCU's dual servo valve could jam as well as deflect the rudder in the opposite direction of the pilots input. As a result of this find, the FAA ordered that the servo valves be replaced and that new training protocol for pilots to handle unexpected movement of flight controls be developed.^[1]

[edit] Other 737 Rudder related/suspected accidents/incidents

March 8, 1994 a Sahara Airlines plane crashed in India while on a training flight due to misuse of rudder, killing 9 people.

April 11, 1994 a Continental Airlines pilot reported his plane rolled violently to the right, landed safely.

June 9, 1996: Eastwind Airlines Flight 517 experienced loss of rudder control while on approach to Richmond, VA.

[edit] SilkAir controversy

On December 19, 1997 SilkAir Flight 185 crashed in Indonesia killing 104 people. While the Indonesian NTSC, the lead investigating agency, could not determine the cause, the U.S. NTSB, which also participated in the investigation, concluded in a report issued in 2000 that there was no mechanical failure, and that accident was caused by a pilot, most likely the captain, intentionally crashing the aircraft by applying sustained nose-down control pressure.^[2]^[3]

In 2004, a Los Angeles jury, which was not allowed to hear or consider the U.S. NTSB's conclusions about the accident, ruled that the 737's rudder was the cause of the crash, and ordered Parker Hannifin, a rudder component manufacturer, to pay US$43M to the plaintiff families. Parker Hannifin subsequently appealed the verdict, which resulted in an out of court settlement for an undisclosed amount.^[4]^[5]^[6]