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drofgnal · 10-20-2010, 10:50 AM

This type of thread pops up every now and then. I've responded to this same issue months before. I'm an aerospace engineer, although this is not my specific area, I know a little about this.

The potential problem is real. To know this all you have to do is put a blackberry or smartphone beside a speaker phone and listen to noise coming over the air. Now if 200 people pull out wi-fi or even worse 3G devices in a confined space the EM noise could be significant. The problem is radiated emissions of the device (and susceptibility of the circuit) causing noise in an adjacent circuit. (manufacturers also test for conducted emissions and susceptibility.) An awful lot of testing goes into certification for electromagnetic enviromental effects.

Turning all electronic devices off during the first few and last few minutes even those without transmission capability seems stringent, (and on this point I'm not real sure) but remember it is during these times that planes are following routes to/from the landing strip based on signals (electromagnetic) from ground beacons as well as talking to the tower (radio) and being under the influence of the airport radar. Some caution is called for given the dense traffic that can be in the vicinity of the airport and the dire consequence of a mishap. Also note that you don't have to have a transmitting device for a device to have radiated emissions. Any time varying electric current produces a subsequent magnetic field in the vicinity of the circuit and as such is a source of radiated emissions.

As far as some planes allowing wi-fi in the future, that will imply a rigid certification of the planes devices in operation with multiple devices that passengers could carry. The planes side will be wired into the planes avionics and will undergo a rigid certification to assure it does not interfere in operation with navigation or communication systems of the aircraft. I suspect not many will do this as this will be a huge expense for many.

As far as myself, I can read with my ipad in airplane mode or my kindle with 3g off for the few hours of a domestic flight. For longer flights (international) a movie and a nap are usually in order!

10-20-2010, 10:50 AM	#256
drofgnal Wizard Posts: 1,409 Karma: 10519918 Join Date: Dec 2009 Device: Ipad Pro/Kindle Oasis 3/iPhone 13 Pro Max	This type of thread pops up every now and then. I've responded to this same issue months before. I'm an aerospace engineer, although this is not my specific area, I know a little about this. The potential problem is real. To know this all you have to do is put a blackberry or smartphone beside a speaker phone and listen to noise coming over the air. Now if 200 people pull out wi-fi or even worse 3G devices in a confined space the EM noise could be significant. The problem is radiated emissions of the device (and susceptibility of the circuit) causing noise in an adjacent circuit. (manufacturers also test for conducted emissions and susceptibility.) An awful lot of testing goes into certification for electromagnetic enviromental effects. Turning all electronic devices off during the first few and last few minutes even those without transmission capability seems stringent, (and on this point I'm not real sure) but remember it is during these times that planes are following routes to/from the landing strip based on signals (electromagnetic) from ground beacons as well as talking to the tower (radio) and being under the influence of the airport radar. Some caution is called for given the dense traffic that can be in the vicinity of the airport and the dire consequence of a mishap. Also note that you don't have to have a transmitting device for a device to have radiated emissions. Any time varying electric current produces a subsequent magnetic field in the vicinity of the circuit and as such is a source of radiated emissions. As far as some planes allowing wi-fi in the future, that will imply a rigid certification of the planes devices in operation with multiple devices that passengers could carry. The planes side will be wired into the planes avionics and will undergo a rigid certification to assure it does not interfere in operation with navigation or communication systems of the aircraft. I suspect not many will do this as this will be a huge expense for many. As far as myself, I can read with my ipad in airplane mode or my kindle with 3g off for the few hours of a domestic flight. For longer flights (international) a movie and a nap are usually in order! Last edited by drofgnal; 10-20-2010 at 10:56 AM.