B777 problems
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B777 problems
Glitch blamed for out-of-control jet
By Steve Creedy
September 17, 2005
PILOTS on a Boeing 777 from Perth to Kuala Lumpur battled to gain control of the plane last month after an unknown computer error caused the aircraft to pitch violently and brought it close to stalling.
A flight attendant dropped a tray of drinks and another began praying as the Malaysian Airlines pilots fought to counter false information being fed into the aircraft's autopilot system and primary flight display.
The glitch prompted plane manufacturer Boeing to issue a global notice to all 777 operators alerting them to the problem.
Flight MH124 was about an hour out of Perth when the aircraft began behaving erratically. The incorrect data from a supposedly fail-safe device caused the plane to pitch up and climb 3000ft (914m), cutting its indicated airspeed from 500km/h to 292km/h and activating a stall warning and a "stickshaker".
A stickshaker vibrates the aircraft's controls to warn the pilot he is approaching a speed at which the plane will have insufficient lift to keep flying.
An Australian Transport Safety Bureau report released yesterday reveals the pilot in command disconnected the autopilot and lowered the plane's nose to prevent the stall but the aircraft's automatic throttle responded by increasing the power.
The pilot countered by pushing the thrust levers to the idle position but the aircraft pitched up again and climbed 2000ft.
He notified air traffic control that the plane, carrying 177 passengers, could not maintain altitude and requested a descent and radar assistance for a return to Perth.
As the plane descended through 20,000ft, the pilot reported the primary flight display appeared normal and separately tested the aircraft's two autopilot systems.
But he was forced to keep flying manually when the plane banked to the right and the nose pitched down during both tests.
The pilot reported no difficulties flying the plane but noted that the automatic throttles remained armed.
As the aircraft was positioned to approach Perth, however, the flight display again gave a low airspeed warning and the auto-throttle responded by increasing thrust.
The aircraft's warning system also indicated a dangerous windshear but the crew continued the approach and landed safely.
Shaken passengers remained in Perth overnight and were offered alternative flights the next day.
Investigations are focusing on faulty acceleration figures supplied by a device called the air data inertial reference unit.
The device, which was sent to manufacturer Honeywell and to US investigators for examination, collates aircraft navigation and performance data from other systems and passes the information to the primary flight computer.
Boeing spokesman Ken Morton said yesterday the incident had not occurred before or since. Operators have since been told to load a previous software version.
"There is a very simple test to do before you take off and that will tell you if your system has that problem or not," he said.
"To this point we haven't had any people coming back saying they've had faults."
Mr Morton said there were 525 777s in service and they had accumulated more than 10 million flight hours and 2million landings.
"All incidents are thoroughly investigated and appropriate steps are taken to ensure the continuing safety of the in-service fleet," he said.
"Nothing is more important than that."
By Steve Creedy
September 17, 2005
PILOTS on a Boeing 777 from Perth to Kuala Lumpur battled to gain control of the plane last month after an unknown computer error caused the aircraft to pitch violently and brought it close to stalling.
A flight attendant dropped a tray of drinks and another began praying as the Malaysian Airlines pilots fought to counter false information being fed into the aircraft's autopilot system and primary flight display.
The glitch prompted plane manufacturer Boeing to issue a global notice to all 777 operators alerting them to the problem.
Flight MH124 was about an hour out of Perth when the aircraft began behaving erratically. The incorrect data from a supposedly fail-safe device caused the plane to pitch up and climb 3000ft (914m), cutting its indicated airspeed from 500km/h to 292km/h and activating a stall warning and a "stickshaker".
A stickshaker vibrates the aircraft's controls to warn the pilot he is approaching a speed at which the plane will have insufficient lift to keep flying.
An Australian Transport Safety Bureau report released yesterday reveals the pilot in command disconnected the autopilot and lowered the plane's nose to prevent the stall but the aircraft's automatic throttle responded by increasing the power.
The pilot countered by pushing the thrust levers to the idle position but the aircraft pitched up again and climbed 2000ft.
He notified air traffic control that the plane, carrying 177 passengers, could not maintain altitude and requested a descent and radar assistance for a return to Perth.
As the plane descended through 20,000ft, the pilot reported the primary flight display appeared normal and separately tested the aircraft's two autopilot systems.
But he was forced to keep flying manually when the plane banked to the right and the nose pitched down during both tests.
The pilot reported no difficulties flying the plane but noted that the automatic throttles remained armed.
As the aircraft was positioned to approach Perth, however, the flight display again gave a low airspeed warning and the auto-throttle responded by increasing thrust.
The aircraft's warning system also indicated a dangerous windshear but the crew continued the approach and landed safely.
Shaken passengers remained in Perth overnight and were offered alternative flights the next day.
Investigations are focusing on faulty acceleration figures supplied by a device called the air data inertial reference unit.
The device, which was sent to manufacturer Honeywell and to US investigators for examination, collates aircraft navigation and performance data from other systems and passes the information to the primary flight computer.
Boeing spokesman Ken Morton said yesterday the incident had not occurred before or since. Operators have since been told to load a previous software version.
"There is a very simple test to do before you take off and that will tell you if your system has that problem or not," he said.
"To this point we haven't had any people coming back saying they've had faults."
Mr Morton said there were 525 777s in service and they had accumulated more than 10 million flight hours and 2million landings.
"All incidents are thoroughly investigated and appropriate steps are taken to ensure the continuing safety of the in-service fleet," he said.
"Nothing is more important than that."
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ATSB Preliminary Report found here: http://www.atsb.gov.au/aviation/occu...ail.cfm?ID=767
The flying conditions that arvo in Perth when they landed suggests the windshear alert was probably real and not false.
Although the computers did go "balls up" the pilots dealt with he situation calmly and professionally.
Dont believe everything in newspaper investigations as gospel.
Although the computers did go "balls up" the pilots dealt with he situation calmly and professionally.
Dont believe everything in newspaper investigations as gospel.
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This event perfectly illustrates an important point about airplanes and computers and the need for all the big stuff to have an off switch for ENIAC when it goes maniac.
Wouldn't you prefer to fly with a seasoned pilot having a manual override on the
computer brain available as opposed to any pilot, well trained or not, flying a HAL-brained beast with no disconnect.
Glad the guys at Malaysian were able to force their intentions and carry out the actions required for a recovery after that little joy ride. Aren't there AT disconnects right on the throttle levers on this aircraft and were they used ? We'll have to see what the FDR's have to say......meanwhile, someone get the book on which CB's to pull, just in case.
......
Wouldn't you prefer to fly with a seasoned pilot having a manual override on the
computer brain available as opposed to any pilot, well trained or not, flying a HAL-brained beast with no disconnect.Glad the guys at Malaysian were able to force their intentions and carry out the actions required for a recovery after that little joy ride. Aren't there AT disconnects right on the throttle levers on this aircraft and were they used ? We'll have to see what the FDR's have to say......meanwhile, someone get the book on which CB's to pull, just in case.
......
Last edited by vapilot2004; 2nd Oct 2005 at 10:52.
