This may be a silly question, and may have ben answered may times before, but why do the airlines and the FAA tell us to turn off all electronic devices during takeoff and landing? Is it a precaution or real problem? And what is it specifically? I would prefer the real reason, and not the "Canned" airline/FAA response. Is it the transmitting frequency of some of them? Devices not compliant to the IEEE802.11 2.4Ghz standard? What is the real beef??

Airlines believe that ANY device that transmits COULD pose a hazard to inflight systems.

I have been told lotsa times I can't use my CD player.

My biz partner and I were playing a game of a wireless lan (802mghz?) once...that sent them for a tailspin.

Now I have my Creative mp3 Jukebox confusing them...

I am not an electronics engineer by any means...I just find that if they don't know what is possible they would rather be safe than sorry...as would I.

Dorian

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Not being an RF guy, I can't comment beyond the "canned" response, but Dorian - how do you like your jukebox? I'm planning on asking my wife for one for X-mas.

Greg

I have heard good things. Was looking for one for my spouse last night...the guy at CompUSA said that they can't keep them in stock. I was hoping NOT to wait for a mail order house, but they've become impossible to find in NYC. Oh the stupidity of not buying when we first saw it!

There are sort of, what we might call, urban legends about such devices interfeering with the aircraft navigation systems. For example, people setting up a lan in flight causing the instruments to go haywire, pax turning off the computers, and instruments return to normal. Not sure how ture these urban legends really are. However, we do know that it is a hit or miss kind of thing, if it exists at all. E.g. such problems are difficult to impossible to replicate. Another reason is probably that the carriers would rather have you use the expensive phones they have, rather than your own cell phone. Only somewhat recently did carriers routinely start letting pax use cell phones while the aircraft was at the gate. If there is any real safety concern about using these devices, it is very striking that the airline industry has no real mechanism to enforce these rules, or ddetect the devices. After all, how do they know if all the pax have turned off cell phones, etc? If the equipment is as sensitive as it is said to be, then how far fetched is the movie Die Hard II? Or parts of it? As you might recall from the movie, terrorists basically took over the IAD tower frequency, transmitted on it, and gave an inbound aircraft incorrect landing instructions. They also interfeered with the radio frequency used by various navigational aids like VOR, ILS, etc. All these nav aids are basically radio frequency based.

For those who are engineering geeks, IEEE Spectrum had a great article on this subject a couple of years ago. It turns on that the far and away worst device for interfering with airplane instruments is a laptop PC...if the shielding has been damaged. If your laptop is opened for repair, the factory-installed shielding may not get put back in place properly. If so, your PC is over 100 times worse than a cell-phone (in the U.S.)

In 900 MhZ GSM countries (most of the civilized world), everyone knows that when the phones transmit they interfere with radios and TV's. So that's why phones are not allowed. Another reason is that it plays havoc with the cellular phone system when your phone is passing from cell to cell to cell at 500 mph.

But it's crazy that PC's are allowed during normal operation even though maybe only 1% have faulty shielding. It goes to show you that the FAA isn't willing to piss off the public too much.

There was an interesting thread on subject of phones on the PPRUNE board a while back, I don't have time to look for it now, leaving for Chile in a few hours.

Phones accidently left on in crew luggage have had an effect on instruments!

http://www.pprune.org/cgibin/Ultimate.cgi

I always figured that some planes have a device that warns pilots of cel. phones or they see it in the instrument error...because:

I was on a flight once where the FA's were running around trying to find a person making a call....somehow they knew....and they found him.

OT: Jukebox rocks. Just downloaded the newest upgrade direct to it...adding more features. Only things is battery life...

Dorian

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