this said, i never power off my devices...just put them in airplane mode if they have them, or to sleep. i fly a lot, both domestically and internationally.
If you broadcast on the radio frequency the pilot is speaking on, you can jam their transmission.
If you broadcast on, say, the instrument landing frequency (ILS) frequency, the ILS needle the pilot is looking at will stay centered, no matter how much he deviates from the approach path.
The pilot would undoubtedly realize something was amiss, switch comm frequencies, use GPS etc. But it could cause some distraction and wreak some havoc.
Back in the 90s, there were cheap CD players and whatnot that would generate all kinds of crazy RF.
The FAA said, this is all unapproved electronics, we can't test it, it has to go off during takeoff and landing, unless the pilot OKs it. Of course, the corporate pilot will OK it for his CEO/passenger.
But some of the electronics are not in the cockpit.
Did you come across anything like that?
If it was possible, I can't imagine that the TSA would let us carry as much as a 9-volt battery on board. Even if it were possible, couldn't you just put shielding between the passenger cabin and the cockpit? EM radiation is line-of-sight, after all.
It seems like a giant non-issue that exists mostly due to rulemakers' ignorance.
For an ILS approach to minimums in hard instrument conditions, it could be problematic - especially if you are off course and don't realize it. There are minimum safe altitudes on approach plates that could be violated if you are way off course (putting you into a TV tower, for example).
I'm not an airline pilot but I am pilot. I'm not aware of anything better than ILS for those types of conditions (very low ceilings and visibility). VOR/NDB approaches are non-precision approaches. The GPS I have access to does not permit a precision approach - maybe the airliners have something better.
But the checklist should check that the ILS is alive... and if it's centered horizontally and vertically the pilots should notice.
OTOH a crafty terrorist could wait for a bad weather day, unplug the airport ILS, and set up an alternate one in a nearby building. Still, the tower would probably notice something was amiss and just say 'go around'.
Don't forget PAR, which generally has mins comperable to, if not lower than, ILS.
Anywhoo, different airports, different frequencies, and differernt ways they might interfere. Since that time laptops have gotten better (and faster, they are all generally over a gigahertz on their various busses), and radios have gotten better too.
A AT&T friend actually mentioned that AT&T had asked the airlines to ban cellphone use (back in the 900Mhz analog days) because the towers couldn't deal with a cell phone that went by a 500 MPH. However I've never been able to confirm that with any public record so I consider it hearsay at best.
[1] http://www.allstar.fiu.edu/aero/adf.htm
[2] http://www.ntia.doc.gov/legacy/osmhome/redbook/4d.pdf Redbook see pages 4-172 thru 4-174
The cell phone ban is an FCC ban, not FAA like devices during takeoff and landing - http://www.fcc.gov/guides/wireless-devices-airplanes
In the old days of analog cell phones, a single cell phone would talk to all the towers in range and hog bandwidth on every one. On the ground not many towers were in range, once you got to 20,000 feet, there were a lot. If cell phones were on on all the planes over LA, it would be like a DDOS attack.
Possibly still an issue with digital phones, but they can do a lot of smart things, modulate power, drop calls to not overload the network LOL.
Not inside a metal tube, they're not.
This is not to say that I'm a "believer" one way or the other, but you should also think about it in comparison to the signals that the navigation equipment is trying to receive with its omnidirectional antenna. I.e., a strong CB radio 26,000 miles away. It wouldn't take any power at all to interfere with it, if the interfering signal were on the magic frequencies (which are continually changing due to doppler effects).
Doppler effects will be extremely small, since the greatest speed differential you'll see will be twice the speed of an airplane (when two planes are moving directly towards or away each other), which is not a substantial fraction of the speed of light. There will be some shift, but not nearly enough to bump a device from non-interference to interference. Or did I misunderstand something?
In any case, I don't think any airliner flying today is relying on VOR.
Whether this is 'friend of a friend' type tale that pilots like to say (and co-opt as their own story) or not is difficult to say.
The same pilot also told me the main reason they don't want you using cellphones on a flight was because the base stations couldn't triangulate properly and identify who was making the call - which is clearly BS. Same pilot also freely admitted to using his own phone during flights.
I guess my point is that the pilots at the same time kind-of believe the official excuses, yet at the same time flout them and make up ridiculous reasons why they are official.
He turned on his cell phone and showed that it wouldn't pick up a signal anyway.
This was about 10 years ago, so things have likely changed.
From the author's submission history he has only ever submitted his own stories to Hacker News.
Regardless of what the FAA says, my reason is still valid. It is also not really in conflict with what you're saying...you're right that it's not really consistent since folks are still allowed to read books, but that doesn't invalidate my point either.
I would point out that people are not really as likely to take a crossword with them in an emergency as they would be a computer.
Also, you're frankly wrong in asserting that electronic devices are not more distracting than a paper book; think of anything involving headphones, for instance.
There are a reasonable set of restrictions for safety (i.e. headphones). There are others that are not. For a point of reference, JetBlue provides satellite radio and TV both in-flight and during landing (as well as sometimes during take-off). They've clearly chosen to prioritize passenger comfort in lieu of relaxed FAA regulations, and aren't concerned about the impact of distractions.