Glitch blamed for out-of-control jet

The Courier-Mail (Australia) ^ | 17sep05 | Steve Creedy

[Paleo Conservative]

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."

[cynicom]

Not familiar with nr 2...Johnson also rolled the B-47, much to everyones consternation. That was a long time ago.... He did it at Renton with thousands in attendance.

[elbucko]

In Boeing's philosophy though, they went the conservative root and still left it up to the pilot in the end , the control and judgment up to the pilot.

As well Boeing should. After all, the pilot is the one that's going to die first.

[zipper]

Who knows what really happened-- maybe not even the Captain.

Sometimes FBW does override pilot inputs-- and for good reason. Some fighters such as the F-16 will prevent the pilot from over-g'ing the aircraft throught software attenuation of control inputs.

[WildTurkey]

Fly by wire = die by wire?

There was no indication that the "fly by wire" system had any problems.

[WildTurkey]

you have the electric current that moves through the wires to the hydraulic actuators.

[Prophet in the wilderness]

sorry about the typos and misspelling.

[Prophet in the wilderness]

I think, " Fly by wire " is a more of a " iconic " name for it.

In reality, it's basically the same as the cable and pulley system ,

except?

The actuators in a " Fly by wire " are controlled by electric currents, but the actual movement of the actuator to the control surface is still hydraulic ( correct me if I am wrong on that ).

From what I have seen on science shows, or tech shows, and from reading, the cable and pulley system moves some kind of lever or switch on the actuator.

When the lever or switch is moved on the actuator, it opens a valve inside the actuator , and that allows the hydraulic fluid to more in one direction.

Then when the lever is move in the other direction, the valve inside the actuator moves in the other direction which allows the hydraulic fluid to move in the other direction : in which ? we get the back and forth movement of the control surfaces.

The difference in the " Fly by wire " is ?

Instead of having the cables and pulleys, you have electric currents controlled by the planes multiple computers ( for redundancy and safety ) that is run by the software ( that went out of control ) .... and those electric current signal travel through the multiple wires ( once again, for redundancy and safety.

Still ? the wires are lighter ( less weight ) than the cable & pulley system, and take less maintenance to maintain than the old cable and pulley system ).

In the " Fly by wire " system , with the actuators, instead of the mechanical lever, you have some kind of electric solenoid ( a solenoid like in your cars started ) to move the valves inside the actuator's.





( correct me if I am wrong ) from the actuator valves movement, to the control surfaces, it's still the same as the old cable & pulley system.

I hope I have helped in explaining the difference is between the old cable & pulley system in the new Jetliners, to the old way they used to do it, that's the best I know how I understand it ( if i am wrong in any facts or description, please correct me if I am wrong ).

[Prophet in the wilderness]

That was a prototype before they made the 707 , the actual plane that Tex Johnson did that barrel roll in is down at the AIR & SPACE MUSUSEM near Dulles Airport in Washington DC.
The plane that Tex John Flew was the DASH - 80.

[Prophet in the wilderness]

Yes,, your right, thank you for correcting that sentence.

[operation clinton cleanup]

I was only joking about the terminology.... I fully understand the difference between fly by wire (F-16) and stick and rudder (A-10)... it's always nice to have a mechanical backup no matter what you are driving!

[Prophet in the wilderness]

You got that right. lol.
I sure hope Boeing decides to allow the pilot to disengage the auto throttle in a situation like this.... still ? the pilot should always have the last say and control ( at least in a civilian plane ).

[ncfool]

Could this be the situation with the Missing 777? Look where this happened in 2005.

[ncfool]

is this the same aircraft as in this 2005 situaiton?

Malaysia Airlines Flight MH370

[ncfool]

http://www.atsb.gov.au/publications/investigation_reports/2005/aair/aair200503722.aspx

At approximately 1703 Western Standard Time, on 1 August 2005, a Boeing Company 777-200 aircraft, (B777) registered 9M-MRG, was being operated on a scheduled international passenger service from Perth to Kuala Lumpur, Malaysia. The crew reported that, during climb out, they observed a LOW AIRSPEED advisory on the aircraft’s Engine Indication and Crew Alerting System (EICAS), when climbing through flight level (FL) 380. At the same time, the aircraft’s slip/skid indication deflected to the full right position on the Primary Flight Display (PFD). The PFD airspeed display then indicated that the aircraft was approaching the overspeed limit and the stall speed limit simultaneously. The aircraft pitched up and climbed to approximately FL410 and the indicated airspeed decreased from 270 kts to 158 kts. The stall warning and stick shaker devices also activated. The aircraft returned to Perth where an uneventful landing was completed.

The aircraft’s flight data recorder (FDR), cockpit voice recorder and the air data inertial reference unit (ADIRU) were removed for examination. The FDR data indicated that, at the time of the occurrence, unusual acceleration values were recorded in all three planes of movement. The acceleration values were provided by the aircraft’s ADIRU to the aircraft’s primary flight computer, autopilot and other aircraft systems during manual and automatic flight.

Subsequent examination of the ADIRU revealed that one of several accelerometers had failed at the time of the occurrence, and that another accelerometer had failed in June 2001.

Graphical and animated representation of flight data

Various representations of key parameters were prepared from the 9M-MRG downloaded flight data to assist in the analysis.

Graphical representation of relevant recorded data

General parameters over a 60-minute period containing the entire incident flight are displayed, see figure 6. Other relevant parameters are displayed over a 5-minute period incorporating the upset event, see figures 7-10.

Animated representation of relevant recorded data

An animation of the incident was prepared using Insight Animation™ software and is part of this report. A file containing the animation in Insight View™ format (.isv) is available for download from the ATSB website. This file requires the installation of an Insight Viewer that can be downloaded from www.flightscape.com at no charge. A still screen capture of the animation is shown at figure 11.

Download animated representation of flight data [4.4Mb.zip] please see the information above regarding the playing of this file.

[the OlLine Rebel]

Wow, that goes along with the 14th-street bridge ticket!