Electronic Use and Flying

Can cell phone, video game or laptop use really cause a problem during an airline flight? How?

(I comply with the regulations of course, but always believed that each item had it’s own frequency which differed from the frequency used by the plane)

I did a search and didn’t find this here - if it’s a repeat: Sorry, sorry.

There is a very faint possibility that a large number of malfunctioning wireless devices could interfere with certain wireless devices used to control the jet during takeoff and landing. The chances of this happening are vanishingly small, but the downside of it actually happening are so staggering that they’d rather make everybody live without their precious cell phones for a few minutes than risk killing all of them. Same idea with telling people to not use their cell phones while they’re filling their gas tanks: how important is that phone call to you, vs. the chance of going up like a torch?

Ever driven past a commercial broadcast station and had its signal whomp all over whatever you were listening to at the time? Same thing. filters and tuning circuits don’t only allow one single frequency to pass and totally block all others, there’s what’s called a rolloff, which is measured in decibels per octave. The greater the dB/octave rolloff, the tighter the filter and the higher the attentuation will be to frequencies outside its design parameters. But, no matter how good it is, a strong enough signal will always be able to penetrate it. Additionally, aircraft avionics aren’t designed like radio receivers; there might be some filtering on the inputs and power supplies, but those are mainly intended to attenuate electrical noise. This equipment may react unexpectedly to strong nearby signals, and there are hundreds of reports each year of incidents believed to have been caused by passenger electronics. In at least one case, the passenger was asked to turn his device on and off a few times to see if it reeally was the source of the EMI and the problem did appear to come and go in coincidence with the powering on of off of the device. See here for some reports from the ASRS.

Are there any documented cases of such? I thought it was an urban legend?

Thank you both. I read an article regarding Quantas attributing a few recent incidents to electronic devices. Dopers are the best!

Also keep in mind that according to a friend who flies for a large US carrier one reason they want you to turn everything off is so you will pay attention to the flight attendent just in case there is a “problem” during take-off or landing. If you were on the phone talking to your SO, or listening intently to music or watching a movie, you might not hear the instruction to “get out of the plane!”

For devices like video games, DVD players, iPods and so on, the rules have nothing to do with radio signals or interference. They just want you to be paying attention to what’s going on around you at takeoff and landing - theoretically the most dangerous parts of the flight. As such, you can use them for the bulk of the cruise.

ETA: dolphinboy beat me to it.

There is not a single one. There is a case where a fire chief ascribed a pump fire to a cell phone, but it’s anything but conclusive, and some evidence suggests static to be a more likely suspect.

There is a documented case of a cell phone triggering a flammable gas (I don’t recall if it was LPG, natural gas, propane or what. I vaguely recall it being propane, but I can’t say for sure) fire, but this was a material with a lower ignition temperature than gasoline in an environment neatly between the gas’ LEL and UEL, conditions which rarely exist in the outdoor environment at gas stations.

I was wondering if that prompted the question.

Complete info for those interested:

There was an incident earlier in the week where a Qantas Airbus A330, in flight from Singapore, I think it was heading to Perth. Suddenly and sharply climbed several thousand feet, before nosing down and descending very rapidly again.

36 passengers were injured, 11 of them seriously. Reported injuries were as you would expect, being fractures and spinal injuries from being flung around the cabin and into the ceiling. (Keep you seat belt fastened at all times right?)

Media reports in Australia indicated that intial investigations suggested it was caused by a flight software error, and that the air safety people were questioning all passengers about what laptops and other electronic devices they were using at the time of the incident.

I need to add to this that I now recall the proximate cause of the fire was not the use of the cell phone itself, per se, but rather, a spark which was most likely caused by either a momentary battery disconnect or by the switch in the flip cover that tells the phone’s brain that the phone has been opened.

I remember that Mythbusters did an episode on this. They didn’t manage doing it without huge concentrations of fumes, and making a big spark. I think they concluded that it was busted and wouldn’t be possible. Unless I recall wrong, they tested both phones and static.

And here is an update: cell phone was not the cause.

Which doesn’t mean laptops caused it. It probably means Qantas is covering its ass and trying to deflect attention away from its own electronics problems.

I’ve heard that another reason is that, even though most electronic devices won’t cause radio interference, it’s easier to just ban all of them than to be specific as to which ones are and are not allowed. An ipod is not a walkman, but when you see someone wearing a pair of headphones connected to a little plastic box on their belt, you can’t necessarily tell the difference.

For cellphones at least there are also effects on the ground to consider. A jumbo jet with several hundred mobile devices on board would play havoc with local phone networks as it whisked all those devices from cell to cell at several hundred MPH. The phones themselves don’t really cause any trouble to the plane. It’s likely that on average, every single airliner in the western world takes off and lands with at least a handful of active devices onboard that people have forgotten to switch off, and no crashes have been blamed on this in several million flights.

Media release here.

It climbed 200 feet and descended 600 feet. That’s not to say it wasn’t a serious incident, but initial news reports normally come from passengers and frankly, passengers generally have no idea what the aeroplane they’re flying in is doing.

If you download the computer graphic based on the flight data recorder you will see that the initial pitch down event is brief and that a lot of the 20 second 600 foot descent is in a very gentle dive.

They’re asking about portable electronic devices to be thorough, not because they have any expectation that they caused the incident.

Unfortunately, the media just say the ATSB is questioning passengers about portable electronics and the public draw their own erroneous conclusions.

Some lessons from this event:

  1. Media reports are often inaccurate and misleading.
  2. Passenger reports of aircraft incidents tend to be exaggerated (understandably.)

Here’s a fairly lengthy articleon how use of electronic devices can affect navigation systems on aircraft. There does appear to be real interference with navigation systems. I recall a story on an aviation message board about an instance where a pilot (the one who posted) had to abort a landing because of problems with the instrument landing system (ILS). The crew found someone talking on their cell phone, had them turn it off, and then made a safe landing. Unfortunately I can’t find the link again. But to answer the OP’s question, there are indeed problems with interference from personal electronic devices. The article above even suggests some fairly drastic actions - systems that would let the flight crew disable cell phones remotely, for instance.

[url=http://www.reghardware.co.uk/2008/10/10/laptops_could_bear_brunt_qantas_jet_plunge/] Here [/ur] is an article from the Register on this. An interesting quote:

IEEE Spectrum ran an article about experiments showing that cell phone use might cause interference, not that it ever has.

It’s a real problem. Just because a device is not labeled as a transmitter, does not mean that it doesn’t transmit, and just because it it is only supposed to transmit on a specific frequency, does not mean that it doesn’t transmit on other frequencies. You have to make a distinction between ideal behavior, only found in text books, and the real world. Almost anything that uses electricity is a potential source of interference.

Radio and television receivers can produce interference via local oscillator radiation. FM broadcast band receivers are well known for being a potential source of interference to systems that use the VHF aeronautical band, like navigation beacon receivers and voice communications receivers.

Almost all transmitters have spurious outputs, which can be suppressed (attenuated), but not eliminated. They also produce broadband noise. These can interfere with systems that handle weak signals, like GPS.

Anything with digital circuits, which includes almost everything these days, is a potential source of interference. Digital circuits can generate large amounts of RF noise over a wide range of frequencies.

Even things like simple amplifiers and poor electrical connections can produce interference via intermodulation distortion. If you have several nearby transmitters with strong signals, any non-linear device can behave like an RF mixer, producing new signals that are related to the sum and difference of the input signals.

Audio amplifiers can detect and amplify the AM components of signals like those produced by GSM cell phones. That’s why you often hear funny noises when a GSM cell phone is near an audio amplifier. The amplifier is behaving like an AM radio receiver. The unshielded speaker wires are a great antenna.

The final issue is the inverse square law. A weak transmitter that is a few meters away from an aircraft system can easily jam a strong transmitter that is 20 km away.

Under the right conditions, almost any electronic/electrical device can be a source of interference. This can be greatly reduced by proper design, filtering, and shielding, but that costs money, and many manufacturers cut corners in these areas.

I’ve been told that this is now mostly handled by the software that controls the ground cells - a phone that “hits” too many cells and/or appears to be moving too rapidly is simply denied service. My experience using a mobile phone in small aircraft matches this: you can reliably make calls when low (say, below 3000’) but at some altitude (say, above 7000’) there’s little chance.