In turn: 1) Cell phones should not cause a problem on aircraft unless there are aircraft radios in-band. The prohibition against airborne cell phone usage protects the cell system, not the aircraft. Thus, United's policy is a rational response.
2) While the terminal area may well be the most severe electromagnetic environment in terms of spectral usage and density, that is not at all the same thing as the worst case environment for rfi - interference to radios. Rfi is a signal-to-noise ratio (SNR) issue, and with a strong signal from the tower, a high ambient can be tolerated. 3) See (1). 4) A PED-caused serious rfi problem requires the confluence of many factors. The PED has to be emitting an offending signal at the same frequency to which an aircraft COMM or NAV radio is tuned, and the function controlled by the reception has to be critical. The PED has to be located such that the very low-level emission efficiently exits the aircraft and couples to the external aircraft antenna at a level commensurate with that >from the ground-based station. Either the PED signal has to couple at a magnitude higher than the ground-based station if the emission is clock-related (unmodulated) or the emission has to have a modulation characteristic similar to that of the desired signal, and even then the coupled signal must be of the same order of magnitude as the ground-based station to cause a problem. When you put all this together, the probability of an individual PED causing an aircraft mishap is vanishingly small. When you multiply that small number by the large number of flights and PEDs on each flight, the probability of a problem somewhere at some time increases, but is still small. This is entirely commensurate with the FAA response - if there were even a 1% chance in any given year that PED use would drop an aircraft out of the sky all PEDs would be consigned to checked bags, and be checked for battery removal besides - consider that we now have to leave full-sized toothpaste tubes in checked luggage only. Ken Javor > From: "Hopkins, Michael J." <[email protected]> > Date: Fri, 16 Feb 2007 12:04:31 -0500 > To: "Ken Javor" <[email protected]>, <[email protected]> > Subject: RE: Noise canceling headsets > > Interesting thread --- couple of comments: > > 1. United now allows cell phone usage on the ground prior to closing the > door to leave the gate and allows cells phones to be used while taxiing > to the gate after landing. Not aware of any reported problems. > > 2. According to avionics manufacturers, the terminal area is considered > to be the most severe environment for an aircraft, with numerous > radiators all around --- other aircraft comms, ground personnel, radars, > weather and terminal radars, etc... > > 3. Numerous reports have been published regarding cell phones being used > in aircraft. (On a recent flight, a flight attendant announced "would > the person who left their cell phone in the lavatory please push the > call button". Don't know of any reports of adverse effects, although > there may have been some. > > 4. I fly frequently -- many people are using noise canceling headsets > during taxi and takeoff (including me), and I've seen many people > continue to use ipods and other electronic products (Blackberry's??) > during that time. > > > > Michael Hopkins > Manager, Customer Technical Center > Process Instruments Division > Thermo Fisher Scientific > One Lowell Research Center > Lowell, MA 01852 > Tel: +1 978 275 0800 ext. 334 > Fax: +1 978 275 0850 > [email protected] > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of Ken > Javor > Sent: Friday, February 16, 2007 11:29 AM > To: [email protected] > Subject: Re: Noise canceling headsets > > This is not a dissension from the group consensus that personal > electronic devices (PEDs) need to be turned off during critical phases > of flight, but it is a closer examination of what is really happening. > > The original event that triggered the action relative to PED operation > was the final approach of a commercial air transport under autopilot > control and reacting to a VOR or similar ground-based navigation signal. > The PED interfered with the ground-based signal, and that caused the > aircraft to "think" it was in the wrong place. The aircraft lurched in > response to the autopilot commands, and the pilot wrested control away > from the autopilot and landed safely. > > The important point is that the aircraft was some distance from the > airfield, therefore the level of the navigation signal received would > have been attenuated by the distance, as compared to voice commands from > the tower during taxi operations. The likelihood of PEDs interfering > with voice commands during taxi operations seems remote at best. > > The real reason for prohibiting PED operation during taxi operations > seems to be that it would be difficult to allow PED operation on the > ground and then require them to be turned off just prior to takeoff. > Compliance would be much lower. > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to [email protected] > > Instructions: http://listserv.ieee.org/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > > Scott Douglas [email protected] > Mike Cantwell [email protected] > > For policy questions, send mail to: > > Jim Bacher: [email protected] > David Heald: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc > - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
