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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..."
Of course. Remember the cell phone calls from the Pennsylvania flight on Sept. 11, 2001?
It was a joke! When you give me that look it was a joke.
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 :)
> cell phones are different than mobile phones.
No. They are the same thing. In Britain, what you call a cell phone, is called a mobile phone. The CAA mean cell-phones not walk-around-the-house style things.
Because of the high dopplar shifts. They are only meant to work when the base station and mobile are moving less than 100 KPH relative to each other. (I think it is higher for GSM, it is meant to operate on high speeed european trains) I was amazed that people on one of the Sept. 11th hijacked planes were able to even use their phones. Your call would also be handing off from one base station to another and a very high rate.
My rights don't need management.
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."
In a Discovery Wings program (self described Discovery geek with a VFR rating), they showed the build and testing cycle for new aircraft. Even their engineers said (while standing in front of a electronics emissions testing array) that at least on their aircraft, that nothing within the 'consumer bandwidth' can affect the installed electronics.
But to put an argument to those that say that the airlines are prohibiting cellphones to promote skyphones... 'Most' cellular services utilize directional antenna that completely terminates at the ground within 3 - 5 miles. Just ask anyone who works in a building above the 4th floor and can see the cell tower in the distance. Plus, even for those companies that still use large arrays of omni-directional antenna, skipping from tower to tower at 400mph (3 - 6 miles over them) would be difficult for the MTA to keep the call terminated at the handset.
Light travels faster than sound. This is why some people appear to be bright. Until you hear them speak.
You're right, cell phones were never designed to work at that altitude with so many towers in sight. Three towers is basically the magic number (the least number of points to make a cell). Also, the cell phones were designed for day-to-day activity, such as walking or driving around. The sheer number of cells within the phone's sight in a plane coupled with the speed at which you are traveling makes it pretty difficult for the phone to behave.
This has no bearing on whether or not it's OK for a phone to operate on a plane. Shit, the old planes may not have shielding for transmissions of that frequency (old ones at least), but I've been asked to put a four-function calculator away during the middle of the flight at cruising altitude... they just don't want to worry about technical problems like that I guess.
Well really, even receiving signals causes you to generate a signal. The VFO, or whatever kind of fixed-oscillator that is being used to tune and receive the frequencies that the GPS satellites use causes a sort of EM leakage that is detectable.
Is this a problem? Probably not, but just so you know... receiving does generate an electromagnetic field that could theoretically interfere with the most poorly designed electronics on the planet.
It would be interesting if one of the mitigating factors how passangers on UAL 77 overpowered their hijackers was because of the cell phones used to call loved ones, hence interfering with the instrumentation and/or guidance controls, enough to distract the highjackers.
Hmmmmmm.....
Mod Karma -1: I sed bad wurds. If I cep my mouf shut, I wud be at riyses.
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.
I question this tests accuracy. They used a field strength of 50V/meter and then put the test equipment at 30cm. As a passenger I get no where close to the navigational equipment. They mentioned wiring harness in the report but they did not give any test results from the wiring harness. 50V is WAY more interference than any cell phone would ever give off. Again they did not actually use cell phones to conduct this experiment. They used high power interference generators. If a 2 watt device can bring down a plane does anyone really want to be on that plane?
An aeroplane carries many electrical signals around its wiring harness. These can act as antennas and pick up interference from RF sources. Many were designed when there was less requirement to be immune to RF, because no-one could have envisaged at the time that people would be carrying portable radio transmitters.
Aircraft engines are supposed to be stripped down and rebuilt every so often. I'm not sure whether the requirement applies to wiring harnesses. If so, it would be possible to stipulate that shielded cables be employed. But don't be tempted to think that would be an end to it.
The real problem is one of testability. Automotive electronics are tested by placing the vehicle in a Faraday chamber and bombarding it with RF from a signal generator, amplifier and antenna, and seeing what goes wrong. Obviously, parts can be tested this way too
Getting a Faraday chamber big enough for an aircraft is a surmountable logistical problem. Actually doing the testing will take a long time.
But the worst is that it takes only the tiniest alteration in a single parameter to completely alter the sensitivity of the whole system. You can do the test in the chamber, and it will pass; but out in the wild, things are different. Aw, what the hell
Je fume. Tu fumes. Nous fûmes!
Bollocks.
They are immune as well.
At least to a phone you can get on the plane (one that fits in your pocket).
The British Civil Aviation authority tested with a transmitter that was constantly transmitting at 5 watts. That is the maximum allowed power of a car phone (anyone seen a GSM car phone?). And they barely got some interference in some parts of the aircraft. If they would have tested with real mobile power and with real transmission (which is not contiguous) they would have been unable to show interference even with pre-1989 avionics.
Baker's Law: Misery no longer loves company. Nowadays it insists on it
http://www.sigsegv.cx/
[Wrero wrote..] For what it's worth, here is the relivant FAR: 125.204 Portable electronic devices. (yada yada) [end snip]
However, the US majors and national airlines operate under FAR 121, not part 125, which is for charters, and the like.
Part 125 details are here.
Note that in paragraph (a) under 125.1 reads "..when common carriage is not involved". This excludes the type of ticketed travel most people make use of.
Nevertheless, the parts about portable electronic devices are the same in both, IIRC.
-- Experience is a wonderful thing. It enables you to recognize a mistake when you make it again.
But you don't have to worry about this while at 30,000 feet. Up there airplanes are separated by miles.
Not true. There can commonly be as little as1000' separation with a combined horizontal velocity of 1400mph or higher.
Flight levels above 18,000' alternate between easterly directions on the odd-thousands and westerly directions on the even-thousands. The altitudes are determined by pressure altitude and monitored carefully by radar. The altimeters are precision instruments and frequently calibrated.
So, a 767 flying at 250 degrees at flight level 280 (28,000 ft) can meet a 757 flying at 70 degrees at flight level 270 (1000 feet below) along a published airway, and it would not be unusual circumstances. ATC (and their onboard collision detection system) would keep them aware of each other.
There are two aspects to this observation - one sort of reasonable, one not.
First of all, the phone signal is easily strong enough to reach hundreds of kilometers from high altitude. Cell phones transmit several hundred milliwatts of power. I once used a 100 mW ham radio mountaintop-to-mountaintop at a distance of 175 miles. Since 30,000 feet is onloy 6 miles, signal strength per se is not going to keep your cell phone from working.
Then there is the issue of antennae. The cell system antennas are oriented to maximize signal towards or below the horizon. Thus a signal from a high angle will be somewhat attenuated. Also, the shielding of the aircraft body will also attenuate the signal.
Overall, if you operate a cell phone in an aircraft, it is likely to interfere with a number of cell sites.
Then there is the problem of cities with hills or mountains in them. I live about 500 feet above average terrain in the Phoenix, AZ area. I have had a number of weird cell phone effects as a result. Cell service at my house is sporadic. I can start a call from down on the flat and it will carry most of the way home and then be lost. If I start a call at home it will be lost very quickly!
The reason appears to be that as I drive to my home, my signal is first strongest towards cell towers far to my southeast, and then I go around a corner and they are suddenly only good to the southwest. I don't think the system can handle a switch from a cell to one several cells away.
The only good weather is bad weather.
uhh, no, no i don't. do you have a source for that? keep in mind that:
a) fit people can hit speeds faster than that relatively easily. ~11.25s in the 100m dash is ~20mph.
b) people have been riding horses that can go faster than that for a long time. Kentucky Derby winners in the 1870's were running at about 35mph.
so basically i think you're full of it. =)
Flight levels below 18000 also alternate altitudes. Even thousands for westbound IFR trafffic, even thousands plus 500 ft for westbount VFR traffic, odd thousands for eastbound IFR traffic, and odd thousands plus 500 for eastbount VFR traffic. But above 18000, you dont have to worry about the pesky VFR traffic.
Additionally, once you get up really high (~32000, maybe 36000), they start seprating by 2000 or 3000 ft.
There was excellent empirical evidence to dispute this idea in 1900, since many trains traveled near 100 miles per hour at the time, and on most trips the passengers were just fine. On the other hand, the trains did have more of a tendency to explode, and they had fairly frequent nasty derailments.
The IEEE had a very interesting article in Spectrum magazine on the issue of portable electronics and flight safety.
The conclusion was that there is little doubt about the interference and it is not just cell phones. The article relates an incident when too many people listening to the radio (there was some "important" sports match going on) did cause noticeable interference. It seems that in most cases the pilot can notice that some instruments are providing inaccurate readings (thanks to having redundant information around, different instruments would be affected differently) and it doesn't become a big problem.
So, by using your high-frequency electronic devices inside the plane you're making the pilot's job more difficult. During cruise flight it may be less risky and during takeoff and landing it is definitely not recommended. Personally I wouldn't even trust that much those skyphones. I'd rather err on the safe side. Read a book!
Take your cell-phone, put it next to your (CRT) computer monitor, and call yourself. ... :)
Watch the flicker.
Profit.
The chances of the plane being influenced by a call may be very small, but very small is still non-zero. Would you like to crash in a plane due to someone else's fault?
Want to see what your cell phone is doing? Here's something every one of you can do with your cell phone to witness the interference it creates:::
Place it upright, next to your computer monitor speakers. This will probably work best if you use the speaker with the amplifier built in (the speaker with the volume control on it).
Now wait to get a call -- or better, if you've got one of those fancy phone that updates the clock every hour or so. Before the screen lights up and it rings or before it updates the time, you'll hear an odd sound coming out of speakers. That's an example of the interference a cell phone can create.
Try it right now, and you'll see I'm not kidding.
If telephones are outlawed, then only outlaws will have telephones.
An antenna aimed at the metal skin of an airplane will have zero effect inside the tin can. (that's basic physics) The best (or worst) one could do is damage the radar and radio equipment that has exterior antenna.
I was wondering why the electronics inside aircraft would be such insanely sensitive devices seeing how almost nothing else on earth even notices the RF from a pager/cellphone. But after considering the RF cage all that equipment lives in and the age of the entire system design... I'm really not surprised it's so easy to screw it up.
(fwiw, there's a Lucent notice hanging on our 5ESS phone switch(es) warning about RF problems from cellphones within 5ft of the equipment. I think I'm the only one who's bothered to read it in years.)
Actually, I was mostly joking. I have read the actual research (well, I am reading through it now) and it seems that this is another example of bad science turning out an irresponsible academic paper with skewed results which are then sensationalized by "journalists" who don't even read the paper they are reporting on (but write at length out of their ass). Pretty much SOP.
What *should* have been the headline was "Researchers find it is impossible to affect airplanes with cell phones" though even that is kind of innacurate. They found that if you could get a device to transmit continuously on cell phone frequencies at the maximum power that a cell phone might be known to operate at and then put that device 30cm from the equipment in a cockpit there could be minor disruptions in instrumentation. Maybe someone who is more of a radio geek than I am could come up with a much more nefarious and effective device (effective from a longer range, for instance), but a cell phone does not fit the criteria of the device they used to disrupt service.
Er, you may be a pilot, but I'm an A&P of over 22 years experience. :)
Only a few large commercial aircraft have full-hydraulic controls anymore. That's one of the reasons for multiple generators and APU systems.
This is ridiculous. It's not an airline regulation that bans the use of mobile phones; it's an FAA regulation. This applies to general aviation as well as airline flights, too.
Whether the effect is very significant I wouldn't be able to guess (past what the article says) but many instruments are extremely sensetive to electromagnetic fields and thus tuned to precision in the exact field at the spot on the plain in which they are mounted.
For example, the actual compass (as opposed to the directional gyro, a high-speed gyroscope which allows easier reading and does not have turning-errors and the like) is mounted by a trained professional who then parks the plane in a compass rose painted on the ground and computes the deviation on the compass due to metal, electrical currents, and so forth throughout the plane. Adding to those currents and fields could be a minor issue, at the least. Even "E6B" circular slide-rule flight computers are typically made out of plastic or aluminum to avoid throwing off the compass of placed on the dash next to it.
For that matter, its entirely possible that radio navigation aids like VOR or ADF would be sensetive to certain electromagnetic fields.
Even if there were no significant need for this, I highly doubt that an accross-the-board ban would result from the airlines' desire to charge more for phone use. The FAA is incompetent, but not that incompetent. And they seem to err most often on the side of lax regulation, so its not really that bad to see them being strict about something.
I was once told by a gas station attendant who had come back from a safety course (it was EXXON. Ride the Tiger baby!) the cell phone fire scenario is also due to static electricity. The claim is that static from the antenna might cause a problem. There is the additional possibility of the electronics inside the phone igniting gasoline fumes which permeate the case, but I would think this is something that could be tested for. Gasoline fumes are volatile but I have to wonder if they are really volatile enough to be ignited by the amount of current running through a cell phone.
good link here
Nokia couldn't make gas fumes explode with their phones...but they concede that, though extremely unlikely, it is *possible*. Of course, I tell people that it's *possible* I'll become the world's richest yet most beloved benevolent tyrant, but that doesn't mean it's *likely*.
http://xkcd.com/386/
It's the tuned intermediate frequency amplifiers that create the EM waves - and they are effectively small radio transmitters.
But if you were building a military or avionics grade receiver, you would not only shield the case against those IF signals, you would filter them from being back-emitted via the antenna connection. The signals come out of the home radio because it's designed to be cheap and light, and proper shielding is expensive. In exactly the same way, well designed PCs have cases with spring connection fingers so as to shield them effectively, and ferrite beads on some of the ports to prevent the emission of radiation, while cheap ones or case mods with windows have large shielding holes and emit all kinds of crap.
Now, do you want to fly in an aircraft with cheap leaky avionics or well designed shielded wiring systems and boxes? I know which I'd prefer.
Panurge has posted for the last time. Thanks for the positive moderations.
I fly a Cherokee 235, and have received calls, and made calls. I never hear any unusual static, or see my compass swing. I read in a report that they took a cell phone, and had to hold it against the outside antenna of the airplane before the cell phone caused any problem. Same with a notebook! The FAA says in FAR/AIM, that we must follow the FCC, and what they say about electronics in the airplane. The FCC says dont use them. This is of course VFR operaions. IFR operations says that the PIC (pilot in command) can say what can be used and not used in the airplane. I belive it boils down to this: The cell phone people lobbied the FCC to ban cell phones because it was messing with the towers. period!
For those interested in information about actual incidents where Electromagnetic Interference (EMI) has caused failure or degradation in performance to aircraft systems, refer to the following paper:
Electronic Systems Failures and Anomalies Attributed to Electromagnetic Interference
Section 2.3 - Aircraft passenger carry on devices - is relevant to the current discussion and can be found on page 11.