Mr. Hopkins did NOT disagree with me at all on a technical basis, but he did misunderstand the meaning of immunity in an EMI frame of reference, and so did the other gentleman, Mr. Birmingham.
In general, EMI requirements are divided into emissions and immunity, and these are further subdivided each into conducted and radiated, thus generating the familiar CE, RE, CI, and RI requirements and test methods. CE requirements protect radio receivers from interference on their input power leads. RE requirements protect radios from interference coupling into their antennas. CI (swept frequency) and RI requirements protect non-antenna-connected electronics from the effects of intentionally transmitting radio antennas in their immediate vicinity. Immunity in the sense used in the EMI world excludes the mechanism by which an unintentional emission causes rfi. That eventuality must be controlled by levying RE limits. If this is unclear to anyone, I will expand upon it but I think it is an obvious point (with one important exception - requirements on receiver out-of-band responses). The final issue that Mr. Hopkins raises about non-rf signal wires being upset by stray emissions from personal electronics is the one I labeled impossible or a case of extremely poor systems engineering. Coupling to wires from RE even orders of magnitude above RE limits couples sub-millivolt levels to wiring, not to mention that any sensitive wires are shielded. I have worked in aerospace for over twenty years (not continuous) and have never seen a flight critical system depend on microvolt-level signal reception - except at an antenna terminal. ---------- >From: "Michael Hopkins" <michael.hopk...@thermo.com> >To: "Ken Javor" <ken.ja...@emccompliance.com>, "John Woodgate" <j...@jmwa.demon.co.uk>, <emc-p...@majordomo.ieee.org> >Subject: Re: New EU regulations - civil aviation >Date: Sat, Sep 14, 2002, 3:29 PM > > I disagree -- it certainly IS an immunity concern. > > First of all, radio navigation receivers ARE flight-critical avionics since > they are directly coupled to aircraft controls. Most commercial airliners > are flown a large part of the time on auto-pilot, which gets its input > directly from the nav receivers (and now frequently GPS receivers). > > One might argue that it isn't dangerous if the airplane just goes in a > different direction -- unless of course there is another airplane scheduled > to be in that airspace -- but landings also are frequently automated via the > use of ILS receivers which in turn control glideslope -- descent rates, > engine speed, direction, etc.... > > As a pilot, I can tell you that a lap top computer, scanners, AM/FM > receivers can all cause nav and comm receivers to be upset. > > Also, keep in mind autopilot controls are simply electronic boxes connected > by lots of wires -- these may not be antennas, but I would hope someone is > concerned about the immunity of this system to rf -- hate to be on a low > (zero) visibility approach and has someones laptop suddenly emit the signal > that upsets any electronics in any way.... > > My opinion. > > Michael Hopkins > michael.hopk...@thermo.com > > > > > ----- Original Message ----- > From: "Ken Javor" <ken.ja...@emccompliance.com> > To: "John Woodgate" <j...@jmwa.demon.co.uk>; <emc-p...@majordomo.ieee.org> > Sent: Saturday, September 14, 2002 1:58 PM > Subject: Re: New EU regulations - civil aviation > > >> >> To the best of my knowledge, personal electronics interacts with aircraft >> operation by interfering with radio navigation receivers. That is not an >> immunity concern. Does any one on this forum know of a proven case of >> personal electronics interfering with non-antenna-connected > flight-critical >> avionics? I don't, and further I would say it was either impossible, or > the >> result of extremely poor systems engineering. >> >> ---------- >> >From: John Woodgate <j...@jmwa.demon.co.uk> >> >To: emc-p...@majordomo.ieee.org >> >Subject: Re: New EU regulations - civil aviation >> >Date: Sat, Sep 14, 2002, 1:50 AM >> > >> >> > >> > I read in !emc-pstc that Raymond Garner <raymond.gar...@casa.eads.net> >> > wrote (in <sr-511...@ieeepstc.mindcruiser.com>) about 'New EU >> > regulations - civil aviation' on Wed, 11 Sep 2002: >> > >> >>Equipments/systems/aircraft are designed, tested and certified way > beyond the >> >>current EMC legislation >> > >> > They why all the hysteria about passengers' low-power portable equipment >> > causing disastrous interference with the aircraft systems? My impression >> > is that there is something seriously lacking in the immunity >> > requirements for some aircraft systems. >> > -- >> > Regards, John Woodgate, OOO - Own Opinions Only. > http://www.jmwa.demon.co.uk >> > Interested in professional sound reinforcement and distribution? Then go > to >> > http://www.isce.org.uk >> > PLEASE do NOT copy news posts to me by E-MAIL! >> > >> > ------------------------------------------- >> > This message is from the IEEE EMC Society Product Safety >> > Technical Committee emc-pstc discussion list. >> > >> > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ >> > >> > To cancel your subscription, send mail to: >> > majord...@ieee.org >> > with the single line: >> > unsubscribe emc-pstc >> > >> > For help, send mail to the list administrators: >> > Ron Pickard: emc-p...@hypercom.com >> > Dave Heald: davehe...@attbi.com >> > >> > For policy questions, send mail to: >> > Richard Nute: ri...@ieee.org >> > Jim Bacher: j.bac...@ieee.org >> > >> > All emc-pstc postings are archived and searchable on the web at: >> > http://ieeepstc.mindcruiser.com/ >> > Click on "browse" and then "emc-pstc mailing list" >> > >> >> ------------------------------------------- >> This message is from the IEEE EMC Society Product Safety >> Technical Committee emc-pstc discussion list. >> >> Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ >> >> To cancel your subscription, send mail to: >> majord...@ieee.org >> with the single line: >> unsubscribe emc-pstc >> >> For help, send mail to the list administrators: >> Ron Pickard: emc-p...@hypercom.com >> Dave Heald: davehe...@attbi.com >> >> For policy questions, send mail to: >> Richard Nute: ri...@ieee.org >> Jim Bacher: j.bac...@ieee.org >> >> All emc-pstc postings are archived and searchable on the web at: >> http://ieeepstc.mindcruiser.com/ >> Click on "browse" and then "emc-pstc mailing list" >> > > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
