Boeing 737 rudder issues

Starting in 1991, a number of accidents and incidents involving the Boeing 737 were 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 helps direct hydraulic fluid in order to move the rudder. The PCU is manufactured by Parker Hannifin.

Accidents

On March 3, 1991 United Airlines Flight 585, a 737-200 crashed in Colorado Springs, CO killing 25 people.

On September 8, 1994 USAir Flight 427, a 737-300 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. [ [http://www.ntsb.gov/publictn/1999/AAR9901.htm NTSB summary] ]

Other 737 Rudder related/suspected accidents/incidents

On March 8, 1994 a Sahara Airlines 737 crashed in India while on a training flight due to misuse of rudder, killing 9 people.Fact|date=June 2008

On April 11, 1994 a Continental Airlines pilot reported his plane rolled violently to the right, landed safely.Fact|date=June 2008

On June 9, 1996 Eastwind Airlines Flight 517, a 737-300 experienced loss of rudder control while on approach to Richmond, VA.

ilkAir 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. [http://www.casa.gov.au/fsa/2008/feb/18-28.pdf SilkAir 185 - Flight Safety Australia Feb 2008] ] [http://aviation-safety.net/database/record.php?id=19971219-0 ASN Accident description of SilkAir Flight 185] ]

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. [ [http://www.airmech.co.uk/forums/showthread.php?t=2599 Jury blames rudder, not pilot] ] "SilkAir crash families finally receive answers with court verdict", "Channel NewsAsia", July 15, 2004.] [ [http://www.legal500.com/index.php?option=com_content&task=view&id=1136&l5country_code=usv3_pr&l5directory=us500&Itemid=640#51704 Jones Day Parker Hannifin settlement] ]

Boeing 737 rudder upgrade directive

The FAA has ordered an upgrade of all Boeing 737 rudder control systems by November 12, 2002. [ [http://www1.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/WebNewAD/2A37F5FABA444A8086256C4B005A2884?OpenDocument B-737 rudder design defect upgrade,] , November 12, 2002.]

Cultural references

The Boeing 737 rudder control issue, and the two documented crashes associated with it, were profiled in The History Channel show Engineering Disasters 19.

References

External links

* [http://www.pulitzer.org/year/1997/beat-reporting/works/737-2/power_800.gifHow the 737 rudder works]
* [http://www.airlinesafety.com/faq/B-737Rudder.htm Boeing 737 Rudder Design Study]