Emissions from a laptop are naturally (without suppression) on the order of 10 uV/m to 100s of uV/m. 1000 uV/m would represent at least a 20 dB outage at frequencies that could possibly interfere with sensor electronics. The coupling is lossy: 1 mV/m will generate far less than 1 mV signal in the electronics, and this at rf. Does anyone really see this as a remotely possible mechanism? I don't.
---------- >From: "Robert Macy" <[email protected]> >To: "Pettit, Ghery" <[email protected]>, "'James Collum'" <[email protected]>, <[email protected]> >Subject: Re: EMC-related safety issues >Date: Thu, Jan 3, 2002, 3:25 PM > > > Perhaps, it merely interfered with the "sensor" electronics, not the true > magnetic field that was being sensed. > > - Robert - > > Robert A. Macy, PE [email protected] > 408 286 3985 fx 408 297 9121 > AJM International Electronics Consultants > 619 North First St, San Jose, CA 95112 > > -----Original Message----- > From: Pettit, Ghery <[email protected]> > To: 'James Collum' <[email protected]>; > [email protected] <[email protected]> > Date: Thursday, January 03, 2002 11:46 AM > Subject: RE: EMC-related safety issues > > > I still have a hard time believing it was a compass that was affected by > a laptop computer. ADF indication, could be. VOR, maybe. Magnetic > compass? I wouldn't want a magnetic source that strong in my lap! My belt > buckle would be stuck to it. There is quite a distance between a magnetic > compass in the cockpit of an airliner and anything a passenger is carrying. > Not so in a Cessna 172, but in a DC-10? > > Ghery Pettit > > -----Original Message----- > From: James Collum [mailto:[email protected]] > Sent: Thursday, January 03, 2002 10:47 AM > To: [email protected] > Subject: Re: EMC-related safety issues > > > > > ********* > A routine flight over Dallas-Fort Worth was disrupted when one of > the compasses suddenly shifted 10 degrees to the right. The pilot asked if > any passenger was operating an electronic device, and finding that a laptop > computer had just been turned on requested that it be turned off, whereupon > the compass returned to normal. Following RTCA guidelines the pilot > requested that the laptop be turned on again 10 minutes later, when the > compass error returned. > Ref: Compliance Engineering (European edition) Nov/Dec 1996 p12 > ********* > > I am fascinated by this amazing story (which must surely be an urban > myth) and went in search of more info on the internet. > I had never heard of the RTCA ( a private corporation) before, but > noticed via their web site that you have to be a member company (i.e. pay) > to receive the wisdom that it contains. Aviation is merely a hobby of mine > but I'm interested in reading a copy of the RTCA's DO-233/214 and 196 > documents without shelling out hundreds for the privilege, can anyone > advise? Also does anyone know what recommendations have they made to > modifying FAR 91.21 (as per their web site). > In reading this again, I'm curious as to how the pilot would have known > about a private companies convoluted guideline for fault finding on errant > radio direction equipment involving locating industrious passengers and > commandeering their computers at 10 minute intervals. > Surely he would have done what any professional engineer would do, beat > or kick the 10 degree error out of the RDF equipment? > Or maybe just wonder to him/herself about how strange things happen in > the Dallas Fort Worth area? > > Tounge in cheek, my comments and not those of my employer etc. > > Jim > > > > ------------------------------------------- > 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: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson: [email protected] > Dave Heald [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > No longer online until our new server is brought online and the old > messages are imported into the new server. > ------------------------------------------- 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: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
