pattern_is_full

"The original UK radar trials were conducted at Orfordness ....The early tests showed echoes from Europe over 2,000 miles away."

Suffolk having been transplanted for the tests to the east coast of Canada?

I heard this RFI story from an editor friend who ran the newspaper outside the Bremerton Navy Base in the NW US. When the Associated Press began sending photographs via digital satellite instead of land-line fax around 1990, pictures that arrived around 6 a.m. each day were scambled. As an afternoon paper that printed at 10 a.m., this meant some of the best newsy news pictures from the Gulf War I were getting toasted right on deadline.

After a little investigating he discovered that all the big aircraft carriers in port tested their search radars at 6 ack-emma, and that all of them pointed directly at the newspaper's satellite reception dishes (ships lined up in parallel berths facing the town.) The beams were turning the incoming AP signals into guacamole.

That was at a range of about 1 mile or less, though.

That Crikey story at first listen sounds a bit like finding a false bottom in your wastebasket and blaming it for all your mistyped pages - but maybe it will go somewhere.

TWT

I don't think radar interference with APTN's satellite downlink is relevant here.It's not difficult to swamp a satellite LNB operating at C Band ( 4Ghz) or Ku Band (12Ghz).Even wireless broadband transmitters will do that at C Band.I could always tell when the US Navy had arrived in Singapore.We got the same interference on several of our satellite downlinks at C-Band.The Harold Holt station in Learmonth is VLF,19kHz,much much lower in frequency.And the ADIRU is not a piece of equipment specifically designed to receive RF signals so would be far less susceptible given the extra shielding requirements.

Rob W

See new interim report here: aair200806143.aspx

Key new points:
1. Testing discounts Leamonth VLF interference.
2. No fault found with ADIRUs so far; testing continues.
3. PRIMS usually filter spikes from ADIRUs, but fail to filter rare combinations of spikes. Only applies to A330/340.
4. ADIRU 1 generated many spikes. Two sets appear not to have been rejected by PRIMS and resulted in nose-down events. Subsequent events explained by as-designed fall back response.
4. Three other similar incidents (all having no ill effects) uncovered (4 total, all QANTAS or Jetstar)
5. Reproducible situation identified where loosely fastened seatbelts can disconnect if passenger propelled upward.

Curiouser and curiouser...

bsieker

I think everyone is missing the point.

The problem is not that the ADIRU 1 sent "erroneous and spike" values. ADIRUs are known to fail occasionally, that's one of the reasons why there are several of them.

This is evidence of a serious flaw in the Airbus FBW control software in the A330/A340 PRIMs (Flight Control Primary Computers).

Spike filtering is essential, and "the manufacturer advised" that there was "an issue" with the software, in which AoA spike values could be passed on to the control algorithms in certain conditions.

It is not unexpected to people involved with high-reliability software for safety-critical systems that it appears to be a requirements/specification problem.

There is a temporal sequence of AoA spike values (I will call it "Critical Spike Value Sequence", CSVS) from the ADIRUs that will get past the spike filtering and be interpreted by the flight control/envelope protection algorithms as real values.

It appears that the software develeopment process at Airbus is not quite what it should be.

Either the algorithms were specified incorrectly and the emergence of CSVS is inherent in the algorithm, or the algorithm was implemented incorrectly, and the emergence of CSVS is an artifact of implementation issues (coding/compiler/linker/hardware). According to the report, Airbus identified a problem with the algorithm, so that points to the first alternative.

Either way it is a strong case for the need to use formal methods for both requirements elicitation, ensuring their completeness
and adequacy, and for implementation, using state-of-the-technology "Correct-by-Construction"-methods.


Bernd

M100S2

"The original UK radar trials were conducted at Orfordness ....The early tests showed echoes from Europe over 2,000 miles away.

Suffolk having been transplanted for the tests to the east coast of Canada? "

No need to move Suffolk. Orfordness to Mount Elbrus is circa 2000 miles