[ghjm]

It may well be that cellphones present no danger to airliners, but I have had two occasions when forgetting to turn off a cellphone produced interference noise in my headset while flying a C172SP. Of course it was my own cellphone so I just turned it off.

Maybe it's not a problem on airliners because they are better shielded, or just bigger, than a Skyhawk. But I can say first-hand that it is at least possible for a cellphone to interfere with an aviation radio.

[nitrogen]

I've experienced noise from old phones on cheap computer speakers, alarm clock radios, and installed sound systems in churches. It's annoying, but if the interference is in the audible frequency range, I doubt it's harmful.

[xtdx]

How do you know there isn't interference in the inaudible frequency range? Because you can't hear it?

[nitrogen]

It's an inference from the fact that the phones pass FCC regulations. Maybe that's an invalid inference.

[justin66]

There are some incidents recorded at http://www.37000feet.com/

Incidents involving interference from GPS, cell phones, etc. are recorded. The way people react when reading those reports is more interesting to me than the reports themselves. It's interesting how strong opinions are on this subject.

[beagle3]

I don't have time to read it, but .. GPS?

GPS devices are completely passive; how can they interfere?

(Unless you are talking about incoming GPS satellite signal. In which case -- dah, they've been out there for the last 40 years, the planes farrady cage structure should have accommodated this long ago, and it can be solved with strategically placed tin foil on the offending openings)

[CamperBob2]

(Unless you are talking about incoming GPS satellite signal. In which case -- dah, they've been out there for the last 40 years, the planes farrady cage structure should have accommodated this long ago, and it can be solved with strategically placed tin foil on the offending openings)

Interesting bit of trivia: the energy received from a GPS satellite is said to be roughly equivalent to a 40-watt light bulb on the other side of the continental US.

[tesseract]

In fact the GPS signal at a typical receiver is actually 100x (or more) quieter than the noise floor in its band.

[nitrogen]

Radio receivers are not completely passive; they can act as transmitters at the frequency used to generate their intermediate frequency[0][1][2].

[0] https://en.wikipedia.org/wiki/Unintentional_radiator

[1] https://en.wikipedia.org/wiki/Superheterodyne_receiver#Inter...

[2] https://en.wikipedia.org/wiki/Radar_detector_detector

[beagle3]

That's neat, and I was aware of the theory, not of the practice.

Is there any reason to believe that a GPS unintentionally radiates more than (say) a walkman that has a radio? or a wristwatch that has a built in radio? Or that it should interfere with plane instruments more than the latter?

I'm not automatically discarding any report of interference, but I suspect a placebo effect is in play here, with people paying 10 times more attention to everything when they expect something should go wrong.

[nitrogen]

I switched from EE to CS quite early (and then from CS to solo bootstrapped startup), so I can only speculate beyond what I've already posted. I'm inclined to agree with you, though; if TV fiction is the infallible source of knowledge it purports itself to be, then pilots would seem to be among the most suspicious of professions (gremlins?).

I'd like to know what makes avionics so special if it turns out that they are indeed very sensitive. Consumer, automotive, and industrial equipment has to shield against, filter out, and isolate all kinds of noise.

[nitrogen]

then pilots would seem to be among the most suspicious of professions (gremlins?).

That should be "superstitious," not "suspicious." That post was made from a phone.

[dhimes]

Even passive devices can have noisy internal circuits.

[rjsw]

The first Bluetooth development kits from Ericsson came with a lot of documentation including papers on how passenger's electronic equipment on planes affected the navigation equipment. The summary was that there was enough redundancy across the different systems that pilots could cope with any problems during level flight but stuff really needed to be turned off during takeoff and landing.

Maybe laptops (and planes) are much better than they were then, but I am amazed by the number of people who have persuaded themselves that there couldn't possibly be a problem so it is ok to ignore instructions to turn off their toys.

[Symmetry]

That link is down for me right now, but if they really do claim that they're getting interference from GPS then that site is sufficiently unhinged that I can't trust their analysis.

I figure that the way this works is something like this

* Flight instruments will have problems occasionally.

* People on planes always use electronic devices, but the flight crew here about it unless they specifically ask the stewardesses to look for people using electronic devices.

* The flight crew will ask the stewardesses to look if and only if there is interference.

Which means that if the flight crew are normal humans who have heard rumors that these devices cause interference, they will quickly be able to assemble what they regard as evidence for that view.

[justin66]

No offense, but this is what I meant when I mentioned that it fascinates me the way people react. You had a pretty extensive reaction and you didn't even GET to the site, you simply heard about its existence and formed an extensive opinion. FYI: it's run by NASA and collects safety incident reports from pilots and flight crew, air traffic controllers, mechanics, and so on.

Reports have at times been as detailed as reporting that crew determined that a passenger's device caused interference with navigation equipment by observing the effect of repeatedly powering the device on and off. This isn't what the site is for, it's more generally about safety incidents.

The interesting thing about this to me is that it's not exactly inexplicable for devices to emit RF radiation when they shouldn't, or for equipment to not be shielded as well as it should, but engineering-minded people are often inclined to treat this like someone sighted a flying saucer.

edit: if that seems too much like an attack, I can tell you that I thought the whole thing was idiotic until I started digging into the reports and occasionally talking to people about the issue.

[CamperBob2]

Incidents involving interference from GPS, cell phones, etc. are recorded.... by people whose pilot education did not qualify them to diagnose RF communications issues.

[akldfgj]

radio or speaker wire ? Lots of things cause interference with signals in speaker wire, at short distances (<10 feet, which is only relevant to aviation in the cockpit)