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Research: Mobile Phones Disrupt Aircraft
threeturn writes "Another contribution to the ever-popular "mobiles on planes" topic. Every time this is discussed on /. lots of people say "there is no danger - its just the airlines trying to make a buck on their skyphones". Well, now the UK Civil Aviation Authority has done some research which shows mobiles on planes do disrupt safety systems and interfere with compass readings and other navigation equipment. Also reported by the BBC. So do us all a favour and switch your mobiles off next time you fly."
A text message sent to a passenger is one theory for a crash that happened last Friday.
News link
I'm sure I read somewhere though that an airline was going to use wireless for flight attentents.
My impression is that newer avionics are 'more imune' to the interference. It's all the electrinocs pre 1989 that are prone to interference. It's just that there are a lot of planes out there that pre-date 89 and there will be for a while.
As x approaches total apathy I couldn't care less.
As a frequent flyer I'm more than happy to comply with requests to turn off my phone on planes, but recently air-crew have not been tech savvy enough to recognise a P800 'smartphone' in 'flight' (phone bits off) mode. In these cases I offer an explanation and then comply if they insist it goes off, but as all kinds of wireless tech gets built into PDAs, laptops and watches how will they know? Just because it doesn't look like a phone doesn't mean it isn't...
My guess is aircraft will need better shielded systems.
True, but you're forgetting that back in the 60's and 70's, GHz-based transmissions were pretty much unheard of at 30,000 feet so various electronic packages aren't shielded adequately. Lots of these planes have a range of systems onboard that may have been built at any point in the last 30 or so years, retrofitting all of them will take time and a lot of money, something the airline industry is not too keen on right now.
I'd expect to see newer planes kitted out in such a fashion though. What better way to ensure aircraft sales than to say "yup, business class passengers can still use WiFi and their mobiles... on our new jets..."
From the executive summary:
In October 2002, a set of avionic equipment was tested under controlled conditions in a test chamber for susceptibility to cellphone interference. General aviation avionic equipment, representative of earlier analogue and digital technologies, was used. The equipment, comprising a VHF communication transceiver, a VOR/ILS navigation receiver and associated indicators, together with a gyro-stabilised remote reading compass system, was assembled to create an integrated system.
The tests covered the cellphone transmission frequencies of 412 (Tetra), 940 (GSM) and 1719MHz, including simultaneous exposure to 940 and 1719MHz. The applied interference field strengths were up to 50 volts/metre for a single frequency, and 35 volts/metre for dual frequencies.
The following anomalies were seen at interference levels above 30 volts/metre, a level that can be produced by a cellphone operating at maximum power and located 30cms from the victim equipment or its wiring harness.
snip
I am wondering: how realistic is a test which assumes that the phone will be 30cm from the equipment?
> Imagine the area of towers you could hit at 30,000ft in the sky
Quite a few, if the signal was strong enough to travel 30,000 feet. That's 10,000 yards. Which in (British at least - don't know about US) miles, is about 5.5 miles. This might work along the ground, but straight up in the air???
I worked for a while almost at the top of the new HSBC building in London's Docklands. It's only a little shorter than Canada Tower (Britain's tallest building), but above about the 40th floor, you lose your phone signal and can only intermittently make calls.
Therefore, I think that the danger comes not from communicating with cells, but the phones continually searching for cells (which does involve transmission I believe). They do this every few seconds. An unscientific way of showing this is when you are out of range, the battery life of phones left on standby reduces dramatically, due to all the extra transmissions.
Frequency and power - GSM units utilise 900, 1800 and 1900 MHz (depending where you are) 802.11a/b/g uses 2.4 and 5 GHz. In terms of power - just look at the distances involved WLAN tops out at 300 feet without obstructions, phones can manage a bit more :)
I think it's because the only other thing in the 2.4GHz spectrum for aircraft is the WX radar. And since it points forward through the aircraft's nose, anything behind it won't affect it. Also, those transmissions are all within the Faraday cage that is the aircraft's skin--none of those transmissions have to leave the plane (and won't anyway, because of the frequency). Aircraft have onboard microwaves, so I don't think that 802.11b|g poses a problem (don't know about .11a, though).
Q: "Why do sound techs say 'check 1, 2'?"
A: "Cause if they could count any higher they'd be lighting techs."
True, a cell site puts most of its signal out horizontally, and receives horizontally.
That only makes the problem worse.
Consider: You are at 30000 feet, and your phone is on. Its listening for a control channel, and finds one. It does a registration.
Now, several factors are reducing the signal strength of the control channel to the phone: distance, the gain pattern of the site's antenna, and the fact the phone is in a big metal box with small holes in it. So the phone will have a very low RSSI (received signal strength indicator), and will put out maximum power to reach the site.
Now, because the altitude, the angle the signal comes in at and the distance are not going to be very much different for many cellsites - each is going to receive the phone about equally well. This actually tends to EXPAND the range of sites affected - the sites under the plane suffer from the gain pattern of the signal and the emission pattern from the plane (most of your signal is going out horizontally from the windows, modulo knife edge scattering), but get a boost from proximity. The sites far from the plane lose signal due to distance, but now the signal is coming from a lower angle and is in the higher gain portion of the antenna pattern.
Now, cell sites are laid out in a pattern - usually in most urban areas it is a hexagonal pattern, with adjacent cells using different frequencies and DCC (digital color code - basically a number that helps the phone tell the difference between sites). So there WILL be several sites that will match the frequency and DCC the phone is using.
Now, for CDMA systems ALL those sites have to swap data about the signal they are receiving (this is to implement "soft handoff" where the phone gradually changes which site it uses - for a time the phone is actually using 2 sites at once.) This GREATLY increases the data bandwidth used between sites.
For GSM it's a little different - but the upshot is you are STILL confusing the sites and forcing them to talk to each other over the landline connections.
Meanwhile, here is your phone blasting out bursts of RF at maximum power to try to register to the cell site it hears - only to have to register AGAIN a few seconds later because it has moved out of range.
So, your battery will go flat very quickly (the way these new phones keep battery life up is by not being on all the time - they only listen during their assigned time slot, normally. However, when the phone detects that is has changed sites, it must re-register and listen to ALL time slots until it gets one assigned.)
Also, you are tying up resources in the cell system.
Lastly, you are pumping out a fair amount of RF power inside this big metal box full of wires. What is another term for "wire" - ANTENNA. Each of the wires in that plane is detecting some of your radio's signal, and any non-linear element (corrosion, a semiconductor, etc.) can act as a detector to convert the RF into DC. (Think about the old style crystal radios, or the foxhole razor blade radio).
When you do EMI complience checks, you will be amazed at what can act as a receiver and make things go screwy. All sorts of things that you might think "this cannot interfere - it's gigahertz away!" start interfering.
www.eFax.com are spammers
The rules regarding portable electronic devices predate cell phones and the air-phones in aircraft. While I don't disagree that perhaps part of the reason they haven't been approved is because the airlines don't want them approved for use, perhaps part of the problem is that the airlines actually DO want to make things as safe as possible without dramatically over-inconveniencing people. If there is any chance at all that cell phones MIGHT screw up something once out of every 10,000,000 flights, what's wrong with them being that tiny tiny bit safer? Or even having the perception of being slightly safer?
It *is* up to the airlines to decide if a particular device is or is not to be used. What I mean by that is that although rumor has it that cell towers get screwed up if a phone "sees" too many of them, it's under the FAA's and the airline's discretion. Although I could be wrong, I am unaware of any FCC rule that says that cellular telephones are not to be used on planes.
For what it's worth, here is the relivant FAR:
125.204 Portable electronic devices.
(a) Except as provided in paragraph (b) of this section, no person may operate, nor may any operator or pilot in command of an aircraft allow the operation of, any portable electronic device on any U.S.-registered civil aircraft operating under this part.
(b) Paragraph (a) of this section does not apply to --
(1) Portable voice recorders;
(2) Hearing aids;
(3) Heart pacemakers;
(4) Electric shavers; or
(5) Any other portable electronic device that the Part 125 certificate holder has determined will not cause interference with the navigation or communication system of the aircraft on which it is to be used.
(c) The determination required by paragraph (b)(5) of this section shall be made by that Part 125 certificate holder operating the particular device to be used.
At any rate, and I know I will be slammed for this one: Why can't people play by the rules, ever? It seems that quite a few people don't turn off their cell phones on aircraft. It seems that these are the same people that get up before the airplane gets to the gate; the same people that don't turn off their cell phones when going to the theater. How much, really, does it harm your personal liberties to play by the rules occasionally, and turn off the damn things when on an airplane? This society seems to always be "me me me me", and this just seems to be a symptom.
So make the guy sitting next to you feel better. Put your seatback in the upright position when they tell you to, turn off the laptop when you should, and leave the cell phone off.