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amair
6th Mar 2009, 03:55
Associated Press report:

Air safety investigators on Friday ruled out interference from a U.S. naval transmitter as the cause of a Qantas jetliner nose-diving twice off the Australian coast last year but failed to pinpoint what led the plane's computer to malfunction.
A second interim investigation report released Friday also failed to explain an explosion aboard another Qantas flight on July 25, 2008, that tore a gaping hole in the fuselage of a Boeing 747 over the South China Sea.
That jet - on its way from London to Melbourne - made an emergency landing in the Philippines without injury to any of the 365 people aboard.
The ongoing Australian Transport Safety Bureau investigation into the Oct. 7, 2008, flight from Singapore to Perth - in which 12 passengers and crew were seriously injured - had examined whether the computer malfunction on the Airbus A330 was triggered by electromagnetic interference from a low-frequency U.S.-Australian naval submarine communications transmitter on Australia's northwest coast.
The A330 had been 100 miles (170 kilometers) from the transmitting station when it nose-dived 650 feet (200 meters) in 20 seconds before the crew brought it back to the original cruising altitude of 37,000 feet (11,300 meters). The sharp drop was quickly followed by a second drop of about 400 feet (120 meters) in 16 seconds.
The aircrew detoured to an air strip near the station. In all, 44 passengers and crew were injured.
The Naval Communications Station, Harold E. Holt, was built by the U.S. Navy in the 1960s. It provides low frequency radio transmissions to the U.S. and Australian navies across the western Pacific and eastern Indian oceans.
Pilots have previously voiced suspicions that the transmissions interfered with aircraft instruments.
The report released Friday said the computer unit that caused the airliner to dive had been exposed under test conditions to an electromagnetic field 1,700 times stronger than it had experienced from the naval transmitter when it malfunctioned.
«None of the testing ... has produced any faults that were related to pitch-down events,» the report said.
But the report found that the same unit - which feeds data about the plane's flying angle to the main flight computers - had malfunctioned two years earlier.
That malfunction did not upset the flight and no fault could be identified.
In December, the same type of unit malfunctioned on another A330 flying from Perth to Singapore.
The air crew followed new procedures developed in response to the Oct. 7 emergency by switching off the unit and returned to Perth without mishap. That fault remains under investigation.
The investigation into the 747 emergency reported in August that an oxygen bottle had exploded below the passenger cabin floor, damaging flight instruments and rapidly decompressing the cabin.
The interim report on Friday said similar bottles had been tested but no design faults could be found.
Qantas welcomed the reports as supporting its own conclusions that the airline had not been at fault.
«These two incidents involved extremely rare, if not unique, circumstances that were beyond Qantas' control,» airline chief executive Alan Joyce said in a statement.

Finn47
6th Mar 2009, 05:15
ATSB press release:

MEDIA RELEASE : 06 March 2009 - ATSB Interim Factual Report into the Qantas Airbus A330-303 in-flight upset, 154 km west of Learmonth WA, 7 October 2008 (http://www.atsb.gov.au/newsroom/2009/release/2009_02.aspx)

denabol
6th Mar 2009, 05:49
I went to the ATSB report after picking this up in Plane Talking, and it correctly reports that it has ordered more tests on the possibility of EMI interference.

The A330 issues. More cases, some progress, and lingering doubts about electromagnetic interference - Plane Talking (http://blogs.crikey.com.au/planetalking/2009/03/06/the-a330-issues-more-cases-some-progress-and-lingering-doubts-about-electromagnetic-interference/)

UNCTUOUS
7th Mar 2009, 07:08
.
A suggested root cause for the ADIRU induced upsets has its exposition at this link (http://www.iasa-intl.com/folders/belfast/ADIRU_faults&Tolerances-2.htm)

Seems to address a possibility in terms of the factors and outcomes contained in the interim report (and claims to address an area of potential anomalies that the ATSB/FAA isn't looking at)

Also appears to not be an error addressed by the ADIRU's BITE and triple redundancy cross-checking.

.

Also accessible via: this link (http://tinyurl.com/bcgb88)

or tinyurl.com/bcgb88

.

Probably worth looking at - as they seem to otherwise have no real ideas as to cause (even for the Malaysian 777 incident)

Jofm5
7th Mar 2009, 07:11
Thats a nice big font amir :} does it at weight to what your saying ?

Graybeard
7th Mar 2009, 13:19
Nitpick: Those are radio altimeters, not radar altimeters. Otherwise, interesting.

ChristiaanJ
7th Mar 2009, 20:19
Nitpick: Those are radio altimeters, not radar altimeters. Otherwise, interesting.WTF? Totally irrelevant here. Both terms are used indiscriminately. A "radio" or "radar" altimeter uses FM CW radar technology to measure the distance to the ground, generally from 2500ft downwards.

CJ

tonytech2
9th Mar 2009, 20:05
EMI interference with various units certainly not unknown - L-1011 early on had a problem with the N2 limiting computer and HF interference - #2 engine would run down to flight idle when using the HF on certain North Atlantic frequencies - Another strange one too also on L-1011 - the L2 door lock solenoid would cycle when the electric hydraulic pumps were turned on.\

Very early on when solid state devices were coming in heavily we had things like stab motion sensor bleeping when pumps were switched on (some DC-8), Also erroneus outputs from transponder altitude reporting (DC-8 reporting itself at 42,000 feet).

Of course all the above and others I encountered were because of EMI sources being in close proximity to the units affected. still, with the sophistication now, no surprise if something like a very powerful VLF source could affect some computers.

ChristiaanJ
9th Mar 2009, 20:47
EMI interference with various units certainly not unknown ... You probably already read my post as well, about a prototype Concorde wagging its tail when talking on the HF... the yaw rate gyros were sitting just under the HF aerials... two slots in the vertical fin... not all that efficient, so a lot of HF currents in the surrounding structure. Solved with a few ferrite cores in the right place.
Of course all the above and others I encountered were because of EMI sources being in close proximity to the units affected. still, with the sophistication now, no surprise if something like a very powerful VLF source could affect some computers.Check back to my earlier post about the field strength. To me it simply made no sense... even the 400Hz field strength in the aircraft is probably higher.

CJ

Graybeard
9th Mar 2009, 23:09
CJ: "WTF? Totally irrelevant here. Both terms are used indiscriminately. A "radio" or "radar" altimeter uses FM CW radar technology to measure the distance to the ground, generally from 2500ft downwards."

Maybe you use both terms indiscriminately, CJ, but that doesn't make it right, especially when the topic is related to EMI. As you know, the radio altimeter is FMCW, and radar altimeter transmissions are pulsed. Those are quite different in terms of potential for EMI. Military techies and others just may get confused. In fact, there were radar altimeters used on 737s many years back.

Reminds me of the moderator on another technical forum who used to use electrical "shorts" to mean both short circuits and open circuits...

GB

bsieker
10th Mar 2009, 10:26
I will not duplicate here.

There is an older thread about QF72, and I have posted a comment (http://www.pprune.org/rumours-news/348803-qantas-emergency-landing-21.html#post4778319) there.


Bernd

ionagh
10th Mar 2009, 10:40
"The report released Friday said the computer unit that caused the airliner to dive had been exposed under test conditions to an electromagnetic field 1,700 times stronger than it had experienced from the naval transmitter when it malfunctioned."

The field strength may have been 1700 times stronger BUT the frequencies involved are totally different.

The submarine comms uses LF, way below the medium wave band.
I thought that DO-160 RF susceptability tested started at 100MHz, so it would not have been tested for a radiated field at that frequency....

ChristiaanJ
10th Mar 2009, 17:49
Maybe you use both terms indiscriminately, CJ, but that doesn't make it right, especially when the topic is related to EMI. As you know, the radio altimeter is FMCW, and radar altimeter transmissions are pulsed. Those are quite different in terms of potential for EMI. Military techies and others just may get confused. In fact, there were radar altimeters used on 737s many years back.It's more a matter of definition and terminology than anything else....

Your definition is as good as anything, and "radio" altimeter seems to be more widely used than "radar" altimeter (flipped through a few manuals, and checked Trubshaw's book, who also calls them "radio" altimeters, although on the first flight of 002 he probably called them something else... The French also use "radio-altimètre".)

Just the same, FMCW is a form of radar, and the Bible ("Radar System Engineering" by Ridenour, Rad Lab) calls the grand-daddy of them all, the AN-APN1, a radar altimeter.

Reminds me of the endless confusion with the term FBW.....

As to EMI, I totally agree, FMCW and pulse altimeters would present quite different issues.

Cheers,
CJ

AerocatS2A
12th Mar 2009, 15:26
Given that radar is RAdio Detecting And Ranging, doesn't it follow that a radio altimeter and a radar altimeter are the same?

ChristiaanJ
12th Mar 2009, 16:00
Given that radar is RAdio Detecting And Ranging, doesn't it follow that a radio altimeter and a radar altimeter are the same?
Well, yes, it does... :) , my point too.
It was Graybeard, who suggested that professional "usage" tends to refer to FMCW type radar altimeters as "radio altimeters" and pulse type radar altimeters as "radar altimeters". If that's so, I have no issue with that. Just a matter of accepted terminology, nothing more.

Both shorten to "rad alt" anyway.... to distinguish them from "baro alt".

CJ