EMI question
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EMI question
"Qantas probe laptop link after 300 foot plunge...
Passenger laptop computers are now being investigated as a possible cause of the Qantas mid-air emergency off Western Australia on Tuesday."
Passenger laptop computers are now being investigated as a possible cause of the Qantas mid-air emergency off Western Australia on Tuesday."
"In July, a passenger clicking on a wireless mouse mid-flight was blamed for causing a Qantas jet to be thrown off course, according to the Australian Transport Safety Bureau's monthly report."
In my days (and that dates me) it was 1800 Hz three-wire synchro, and the EMI was from the 400 Hz, not from 800 MHz
I suppose we're now talking multiple digital data buses? If so where and how are the data put on the bus and where are they taken off?
What baffles me is that a laptop or other RFI-producing device in the cabin could even be thought to
a) interfere with a shielded bus,
b) introduce enough similar interference on all four buses (I presume there are four) for it to be interpreted as a valid command.
Interference with radio aids by electronic devices has been observed often enough for it to be more than anecdotal, but that's not my question.
Elevator commands from a laptop?
CJ
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In my days (and that dates me) it was 1800 Hz three-wire synchro, and the EMI was from the 400 Hz, not from 800 MHz
I suppose we're now talking multiple digital data buses? If so where and how are the data put on the bus and where are they taken off?...What baffles me is that a laptop or other RFI-producing device in the cabin could even be thought to
a) interfere with a shielded bus,
b) introduce enough similar interference on all four buses (I presume there are four) for it to be interpreted as a valid command.
a) interfere with a shielded bus,
b) introduce enough similar interference on all four buses (I presume there are four) for it to be interpreted as a valid command.
There are tons of ways for EMI to interfere with the FBW system. In the world of RF (Radio Frrequency), energy can creep in where terminations occur on data lines. I've seen it! There could be an issue with your data lines termination which may cause mismatching, there could also be a noise immunity issue on the front end of the computer (transceiver). I could go on and on...But, I leave the speculations to the investigators and researchers.
Last edited by Bradda G; 9th Oct 2008 at 23:28.
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Bragga,
Apologies, I didn't make myself clear enough.
I'm perfectly familiar with EMI, EMC, etc.
I'm also familiar with automatic flight control systems architecture,fly-by-wire and suchlike.
My question was specifically aimed at the electronic implementation in current FBW systems of the link between flight control computers and elevator controls: bus type, interfaces, etc.
John,
I only quoted those snippets because they were what triggered my realising, that my "knowledge base" was getting thin on the ground since ARINC 429 (and things like Wx radar and DFDR buses).
CJ
Apologies, I didn't make myself clear enough.
I'm perfectly familiar with EMI, EMC, etc.
I'm also familiar with automatic flight control systems architecture,fly-by-wire and suchlike.
My question was specifically aimed at the electronic implementation in current FBW systems of the link between flight control computers and elevator controls: bus type, interfaces, etc.
John,
I only quoted those snippets because they were what triggered my realising, that my "knowledge base" was getting thin on the ground since ARINC 429 (and things like Wx radar and DFDR buses).
CJ