Boeing 737 rudder issues
Encyclopedia
Starting in 1991, a number of accidents and incidents involving the Boeing 737
were the result of the airplanes' unexpected movement of their rudder
s. 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
.
, a 737-200, crashed in Colorado Springs, CO, killing 25 people.
On September 8, 1994, USAir Flight 427
, a 737-300, crashed near Pittsburgh, PA, killing 132 people.
During the course of the investigation of Flight 427, the National Transportation Safety Board
(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, due to thermal shock, caused when cold PCUs are injected with hot hydraulic fluid. As a result of this find, the Federal Aviation Administration
(FAA) ordered that the servo valves be replaced and that new training protocol for pilots to handle unexpected movement of flight controls be developed.
pilot Ray Miller reported his aircraft rolled violently to the right; it landed safely.
On June 9, 1996, Eastwind Airlines Flight 517
, a 737-200, experienced loss of rudder control while on approach to Richmond, VA.
On February 23, 1999, MetroJet Flight 2710
, a 737-200, experienced a slow deflection of the rudder to its blowdown limit while flying at 33,000 feet above Salisbury, Maryland
.
crashed in Indonesia
, killing 104 people. While the Indonesian National Transportation Safety Committee
, 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.
In 2004, a Los Angeles jury, which was not allowed to hear or consider the 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$43 million to the plaintiff families. Parker Hannifin subsequently appealed the verdict, which resulted in an out-of-court settlement for an undisclosed amount.
show Engineering Disasters 19 and on the National Geographic Channel
's Air Emergency episode, "Deadly Components", first aired on May 12, 2008.
The TV series Mayday
also profiled these crashes in the episode "Hidden Danger". The Mayday episode included details on Eastwind Airlines Flight 517
, which led to NTSB investigators issuing a finding in the earlier events.
Boeing 737
The Boeing 737 is a short- to medium-range, twin-engine narrow-body jet airliner. Originally developed as a shorter, lower-cost twin-engine airliner derived from Boeing's 707 and 727, the 737 has developed into a family of nine passenger models with a capacity of 85 to 215 passengers...
were the result of the airplanes' unexpected movement of their rudder
Rudder
A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...
s. The rudder is controlled by the Power Control Unit (PCU). Inside the PCU is a dual servo valve which helps direct hydraulic fluid
Hydraulic fluid
Hydraulic fluids, also called hydraulic liquids, are the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water...
in order to move the rudder. The PCU is manufactured by Parker Hannifin
Parker Hannifin
Parker Hannifin Corporation , originally Parker Appliance Company, usually referred to as just Parker, of Mayfield Heights, Ohio , is the global leader in motion and control technologies. The company was founded in 1918, and has been publicly traded on the NYSE since December 9, 1964...
.
Accidents
On March 3, 1991, United Airlines Flight 585United Airlines Flight 585
United Airlines Flight 585 was a scheduled domestic passenger airline flight from the now-decommissioned Stapleton International Airport in Denver to Colorado Springs Municipal Airport in Colorado Springs, Colorado....
, a 737-200, crashed in Colorado Springs, CO, killing 25 people.
On September 8, 1994, USAir Flight 427
USAir Flight 427
US Air Flight 427 was a scheduled flight from Chicago's O'Hare International Airport to Pittsburgh, with a final destination of West Palm Beach, Florida...
, a 737-300, crashed near Pittsburgh, PA, killing 132 people.
During the course of the investigation of Flight 427, the National Transportation Safety Board
National Transportation Safety Board
The National Transportation Safety Board is an independent U.S. government investigative agency responsible for civil transportation accident investigation. In this role, the NTSB investigates and reports on aviation accidents and incidents, certain types of highway crashes, ship and marine...
(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, due to thermal shock, caused when cold PCUs are injected with hot hydraulic fluid. As a result of this find, the Federal Aviation Administration
Federal Aviation Administration
The Federal Aviation Administration is the national aviation authority of the United States. An agency of the United States Department of Transportation, it has authority to regulate and oversee all aspects of civil aviation in the U.S...
(FAA) ordered that the servo valves be replaced and that new training protocol for pilots to handle unexpected movement of flight controls be developed.
Other suspected 737 rudder PCU malfunction incidents
On April 11, 1994, Continental AirlinesContinental Airlines
Continental Airlines was a major American airline now merged with United Airlines. On May 3, 2010, Continental Airlines, Inc. and UAL, Inc. announced a merger via a stock swap, and on October 1, 2010, the merger closed and UAL changed its name to United Continental Holdings, Inc...
pilot Ray Miller reported his aircraft rolled violently to the right; it landed safely.
On June 9, 1996, Eastwind Airlines Flight 517
Eastwind Airlines Flight 517
Eastwind Airlines Flight 517 was a scheduled flight from Trenton-Mercer Airport in Trenton, New Jersey to Richmond International Airport in Richmond, Virginia. The crew lost rudder control but successfully landed on June 9, 1996. No casualties occurred and one flight attendant suffered only minor...
, a 737-200, experienced loss of rudder control while on approach to Richmond, VA.
On February 23, 1999, MetroJet Flight 2710
MetroJet Flight 2710
MetroJet Flight 2710 was a regularly scheduled flight from Orlando International Airport in Orlando, Florida to Bradley International Airport near Hartford, Connecticut. On February 23, 1999 the flight experienced uncommanded rudder movement and rolled to the right while flying over Maryland at...
, a 737-200, experienced a slow deflection of the rudder to its blowdown limit while flying at 33,000 feet above Salisbury, Maryland
Salisbury, Maryland
-Demographics:Salisbury is the principal city of the Salisbury-Ocean Pines CSA, a Combined Statistical Area that includes the Salisbury metropolitan area and the Ocean Pines micropolitan area , which had a combined population of 176,657 at the 2010 census.As of the census of 2000, there were...
.
SilkAir controversy
On December 19, 1997, SilkAir Flight 185SilkAir Flight 185
SilkAir Flight 185, a Boeing 737-36N, registration 9V-TRF, was a scheduled passenger flight from Jakarta, Indonesia to Singapore, which crashed on 19 December 1997 into the Musi River after abruptly plunging from its 35,000-foot cruise altitude, killing all 97 passengers and 7 crew on board.The...
crashed in Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
, killing 104 people. While the Indonesian National Transportation Safety Committee
National Transportation Safety Committee
The National Transportation Safety Committee is an Indonesian government agency charged with the investigation of air, land, rail, and marine transportation safety deficiencies. It has its headquarters in Jakarta....
, 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.
In 2004, a Los Angeles jury, which was not allowed to hear or consider the 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$43 million to the plaintiff families. Parker Hannifin subsequently appealed the verdict, which resulted in an out-of-court settlement for an undisclosed amount.
Boeing 737 rudder upgrade directive
The FAA ordered an upgrade of all Boeing 737 rudder control systems by November 12, 2002.Cultural references
The Boeing 737 rudder control issue, and the two documented crashes associated with it, were profiled in The History ChannelThe History Channel
History, formerly known as The History Channel, is an American-based international satellite and cable TV channel that broadcasts a variety of reality shows and documentary programs including those of fictional and non-fictional historical content, together with speculation about the future.-...
show Engineering Disasters 19 and on the National Geographic Channel
National Geographic Channel
National Geographic Channel, also commercially abbreviated and trademarked as Nat Geo, is a subscription television channel that airs non-fiction television programs produced by the National Geographic Society. Like History and the Discovery Channel, the channel features documentaries with factual...
's Air Emergency episode, "Deadly Components", first aired on May 12, 2008.
The TV series Mayday
Mayday (TV series)
Mayday, also known as Air Crash Investigation in the United Kingdom, Australia and Asia and Air Emergency and Air Disasters in the United States, is a Canadian documentary television programme produced by Cineflix investigating air crashes, near-crashes and other disasters...
also profiled these crashes in the episode "Hidden Danger". The Mayday episode included details on Eastwind Airlines Flight 517
Eastwind Airlines Flight 517
Eastwind Airlines Flight 517 was a scheduled flight from Trenton-Mercer Airport in Trenton, New Jersey to Richmond International Airport in Richmond, Virginia. The crew lost rudder control but successfully landed on June 9, 1996. No casualties occurred and one flight attendant suffered only minor...
, which led to NTSB investigators issuing a finding in the earlier events.
