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Cell Phone Usage on Airplanes == Bad Idea
gclef writes "The New Scientist is reporting on a study done by the UK's Civil Aviation Authority that shows that older planes can't handle cell phone emissions. Hackernews has a little commentary on this as well. Good to hear that the newer planes can handle this, but why the heck were older planes *not* build with Faraday cages and shielded wires? Scary...." Look a ways down the page for the HNN piece - but at least now I know that this isn't simply one of the arbitrary rules that the airlines setup.
well, GPS approach is becoming more widespread (Truckee-Tahoe even has one, and they don't have a tower!) and ILS isn't used as much. only /slight/ problem with this is that GPS approaches tend to be locked into the flight computer and done automagically (well, this is how it's set up in our 414, anyways), which makes it even MORE of a problem if there's interference.
...) as well as the use of GPS approaches, I'd guess that they're shielded with this sort of thing in mind)
do you know if GPS is as suceptable to this sort of interference? (given the flight-charts-on-the-laptop (not to mention civ:ctp on the other laptop, or the TV, or the VCR,
Lea
There was an article in the WSJ a while back about the whole air cellular thing. It covered the FCC vs. FAA regulation, the lack of any evidence ever of a cell phone or computer interfering with a plane, etc.
One thing they mentioned is that those egregiously expensive AirFones are just cell phones with the base stations farther apart. For that we pay 10-20x higher fees.
However if there is some heretofore undiscovered interference found, then we logically should refuse to fly on airlines with AirFones, no?
Let's all stand by and watch while each airplane is grounded for re-testing. Until that happens I'll take this with a grain of salt.
---- "If we have to go on with these damned quantum jumps, then I'm sorry that I ever got involved" - Erwin Schrodinger
I'm reluctant to admit to such a flagrant act of nerdiness, but, here goes:
My last airline flight happened about a month ago. I thought it would be neat to take my new portable hand-held shortwave radio with me on the plane to see if I could pick up the transponder on the aircraft's black box(es), or maybe some of the cockpit/tower discussion. The flight was pretty much empty (I always take the red-eye) so for about an hour, I sat there with my earphones on and my antenna pitched up and scanned the whole damn plane from 1 Mhz all the way up to about 400 Mhz or so in short, medium, longwave and FM.
I didn't find anything recognizable. I was seated far enough away from the engines to rule out any interference, and the whole spectrum was peppered with odd little noises generated by the aircraft (This was a Boeing 767-300 if I remember correctly) but nothing resembling any sort of communications. Considering the fact I was seated in a giant metal tube, I can also rule out ambient interference. There was a guy with a laptop about 10 rows up, and I could pick up his machine pretty easilly. Anyway, no luck.
Most analog cell phone transmissions occur between 800 and 950 MHz. Youre going to have a hard time finding a scanner than will allow you to listen to that range. If I remember correctly, there was a law passed in '93 or so which made it illegal to sell scanners with capability in that range, in order to protect the privacy of analog cell phone users.
You wouldn't believe the stuff I heard. People's conversations get sorta...weird after 9PM. It's a sick world.
Bowie
PS.. No "You didn't hear anything in the cockpit because the crew was asleep" jokes, please.
Bowie J. Poag
Bowie J. Poag
Actually, most of the cost of aircraft-certified *anything* is in the form of "prepaid liability". Whether its commercial or private, the lawyers will go after every manufacturer of every component in an aircraft in search of deep pockets in the aftermath of an accident.
--
p = transmitter power
d = distance
s = power flux density
s = p / (4 * Pi * d^2)
Mea navis aericumbens anguillis abundat
an article from the Wall Street Journal at junkscience.com. I like the last paragraph of the article that says: "Car accidents resulting from using a cell phone while driving are 'much more of a problem at this point' than radio emissions".
Another good one from junkscience.com
"There is no shot you can take that I cannot simply deny." - Ertai, wizard goalie
Localizers use frequencies around 110 MHz. Consumer FM receivers use a first intermediate frequency (IF) of 10.7 MHz. What this means is that if you tune an FM radio to KOZY 101, the radio transmits noise at 101.1 + 10.7 = 111.8 - which is bang in the middle of the navigation band.
Inertial is not used for approaches, only for en-route navigation. The problem with inertial systems is that they drift, so the longer you've been airborne, the more inaccurate they are. An error of about a mile is no problem up in the stratosphere, but you can't be a mile off the runway when you touch down...Right now ILS is the only precision approach available in the vast majority of cases. Once the FAA puts up WAAS and LAAS augmentation for GPS, aircraft can use GPS for precision approaches.
Unlimited growth == Cancer.
There are all sorts of problems with radio receivers as well. ... The bigger problem comes from a powered heterodyne radio receiver. [nice intermodulation discussion snipped]
Heterodyne receivers aren't the only problem. The current-generation of power transistors are rather wideband and can up/down-convert signals. These transistors are found in DC-DC converters, notebook backlight power supplies, hard disk motor drivers, and so forth. Most gadgets larger than a Palm have some sort of switched power circuit in them. The transistors aren't as wideband as those in radio receivers, but they can still cause problems.
This isn't theoretical either. A while back, we had to diagnose an odd problem with a pager system. There were actually two paging transmitters, and two sets of pagers, on different frequencies about 60 kHz apart. Occasionally, one set of pagers would receive something that had been broadcast on *the other frequency*. It turned out to be a computer monitor: the RF from one transmitter was getting into the monitor, being mixed with the ~60 kHz horizontal frequency, and reradiated 60 kHz up and down from the carrier. You could tune the effect by going into the Windows settings and changing the refresh rate. We engineers all thought it was pretty funny. The users, of course, were less amused.
-- ;-)
Kuro5hin.org: where the good times never end.
Cell phones put out about 1 W of radio power. In typical circuits, that means about 5 volts of signal. That's more than enough to upset many circuits.
So why not just shield everything? Because shielding is expensive and unreliable. The New Scientist article referred to "Faraday cages", but that's *grossly* inaccurate, since a Faraday cage only provides electrostatic shielding (by surrounding the circuit with metal). Real shielding involves seamless metal enclosures. The important thing is *seamless*. Suppose you have a perfect seamless metal box. It's a perfect Faraday cage and a good radio shield -- cell phones will not interfere with anything inside it. If you cut a narrow 0.1mmX15cm slot in it, it will still be a very good Faraday cage, but it will be a *terrible* shield. Radio waves will "shine" right through, despite the narrowness of the slot.
And in the real world, seams and slots are hard to avoid. If a panel isn't properly screwed down or has the wrong type of gasket, radio waves will go right through. If someone yanks on a shielded cable, the shield can invisibly separate within the connector, and actually end up worse than no shield at all. So you just test the shielding, right?. Wrong! Shielding is almost impossible to test. Short of *laboriously* testing every single box and cable with a signal strength meter, you can't test shielding. I would guess that testing all the shielding in an airplane would take a few hundred hours of a radio engineer's time. Nobody could afford to do that on every plane every few years. Since shielding is *never* perfect after a few years of service, and you can't really test it, it's prudent to ban powerful transmitters in the plane.
Absolutely correct. The metal structures of the plane will guide the radio energy to surprising and unpredictable locations. The upshot is that a cell phone in the front of the passenger cabin might send much of its power to an electronics unit at the back of the plane. With radio waves, power doesn't necessarily drop off much with distance, especially in a reflective environment. If you allow a 1 watt transmitter anywhere in the plane, you have to design the plane to withstand 1 watt delievered anywhere.
-- ;-)
Kuro5hin.org: where the good times never end.
Egads. Didn't know that..I thought it was only for takeoffs and landings that such rules applied. So much for scanning for the transponder on my return flight.
Bowie J. Poag
Bowie J. Poag
Okay, my only question is - who's so damn important that he/she/it has to be in constant communication during an airplane flight? Criminey - can't people just relax and have a $10 cocktail and enjoy an in-flight movie? Or (gasp) read a book? Who needs to be connected ALL the time? Probably the same self important twits who try and conduct business while whizzing down the freeway at 87 miles an hour.
- "That's a big no can do" - B. Banzai
In any case, if airplane safety is threatened by radio transmissions in the milliwatt (PDAs) and hundreds of milliwatt (cell phone) range, there is clearly something wrong with the design of those airplanes and navigational systems. Those planes need to get grounded and upgraded. That's both because passengers won't stick to the regulations, and since an adversary can trivially build tiny devices that emit lots of power and disrupt a large part of the spectrum.
That should be "the study is clearly NOT a double blind study by disinterested parties"...
My phone is seeing quite clearly three tower where I am right now, and I'm in a small town. In high density urban areas, you quite often have more than that.
Just immagine the cell tower selection algorithim with an input size of 4000 possible towers.
You are correct that using a cellular phone in a plane causes all kinds of trouble, but this isn't the reason. Remember that cellular systems rely on channel reuse to achieve high capacity. In other words, if channel x is used on tower A, it can't be used on any of the neighboring towers, but it can be used on towers that are further away. The assumption is that with the right power tuning etc, the two towers won't interfere with each other since they are not next to each other (of course sometimes if the network is too dense there are trouble spots where this isn't the case, hence crosstalk). This assumption is based on the fact that users are close to the ground. As you said, when you are in an airplane your cellular phone can see many towers, some of them using the same channels. I'm not sure how a network would respond if one of its channels was used from a phone in a plane, but I imagine that after all the users of the channel suffered from crosstalk for a while, they would either lose their calls or handed off to another channel, rendering one channel useless in a large area. Just a few people using their phones in a plane would have a devastating effect on the capacity of the system underneath, especially if flying over a large city. Not to mention that if your provider has any fraud detection system in place you would probably trigger an alarm by appearing to be in more than one place at the same time.
He's talking about the same studies you were.
Ask any experimental scientist or statician about the difference between establishing a correlation and establishing causation. please.
Critical thinking 101, people.
DNA just wants to be free...
Yeah, I knew that. I also know that the skin of the planes are designed to direct & disperse the energy from lightning strikes to element which are supposed to be able to handle the charge.
But I'm also thinking that the plane isn't a perfect Faraday cage (otherwise you wouldn't be able to hear radio signals from a walkman in the plane) and that the energy of the broadband EM radiation from a lightning strike is going to far exceed the puny 2 watt output of a typical cell phone.
Even if every single passenger on the plane was talking on their cell phones all at once, would it even come close to the electrical disturbance caused by a lightning strike?
While I recommend it to everyone who uses computers for anything of any significant importance, it is especially important to those who:
- Design computer systems, such as software and hardware engineers, and
- Make policy decisions involving computers, such as managers and government officials
This post to comp.risks ought to put the fear of God into most computer users and suggest that us programmers need to work hard to take responsibility for our work: I bring it up in this discussion of cell phones and aircraft because electromagnetic interference in safety-critical systems is a frequent topic on Risks. For example, If you're upset about the sorry state of software these days, there is in fact a lot that can be done about it. Get started by reading Risks.Mike
-- Could you use my software consulting serv
Yeah, this is one of those things that I wouldn't put too much stock in, that cell phones cause brain cancer.
It seems it's one of those things where people are trying to find something to blame.... and they'd do anything to believe in it. It's just like when people say that "living close to power lines" give you cancer.
I mean, think how many people have cell phones, almost everyone. Now, those people who have brain cancer, and use a cell phone, would like to blame the cell phone.
Hey, lets go..
SUE MOTOROLA...
...on an airplane. A cell phone on the ground has line of sight to maybe 2 cell towers at a time. Maybe 3 if you're downtown. From an airplane 30,000 feet up, you're phone's sphere of effect just got huge. Just immagine the cell tower selection algorithim with an input size of 4000 possible towers. Add to that the fact that you're going several hundred MPH and you'd be changing towers every couple seconds. You're looking at a distributed system nightmare. And there's FCC regulations that prohibit you from using your phone up there too.
It has ISBN 020155805X and you can purchase it online from:
- http://www.fatbrain.com
- http://www.barnesandnoble.com
- http://www.amazon.com
- http://www.chapters.ca (Canadian bookseller)
If you teach a course in programming at any school, I suggest you put this on your "recommended reading" list, and if you teach a course in embedded or fault-tolerant computing, I suggest you include it in the required reading.Mike
-- Could you use my software consulting serv
Kind of makes you wonder what could be done with a much more powerful transmitter easily disguised as a small am/fm radio, or even a land-based directional transmitter...
-p.
Assuming that there is no safety issue with using cell phones on airplanes, and forgetting for the moment the legal issues, what about the technical issues?
Sure, lots of people would love to use cell phones when the plane is on the ground waiting to take off or heading to the terminal, and that should work fine, but what about at 30+ thousand feet at 600mph? You would be changing cells every minute or two. I doubt coverage is adequate, even if there's no problem with the range.
Why has nobody run such a test until now?
The regulation was originally put into place because of the strain that airborne cell phones put on the cell phone infrastructure.
:)
When you're on the ground, your cell phone transmissions are being received most likely by anywhere from 1 to 6 cells or so. When you're airborne, that number jumps dramatically...into the thousands maybe?
The original regulation was put into place because, at least at the time, it was quite a strain on the cell phone infrastructure to sort out which cell would handle that call. Arbitrating this access between 5 or 6 cells isn't too terribly difficult...arbitrating it between thousands, well, that gets computationally expensive.
I don't know what the current state of cell infrastructure is, perhaps the systems could more easily sort this out now, I'm not savvy in that area, but anyway, that's the original idea.
Jeff
If you MUST make a call, there are phones you can use on the backs of the seats. So they cost a little more. boo hoo.
--
grappler
Vidi, Vici, Veni
Well, in 1989 (equipment built before then has the problems, according to the article), a 'mobile' was about the size of a housebrick, was incredibly expensive to operate and didn't roam awfully well - so taking it abroad, or operating it on a plane, was something that was never envisaged.
It's easy to ask such questions with hindsight, but what would you have said in the mid-80s if someone had told you that mobiles in 2000 would be smaller than a cigarette packet, and would work practically anywhere in the world?
It's a violation of FCC -- not FAA -- regulations to use cell phones aboard aircraft because of the transmitting range at altitude. Your signal covers more ground, giving greater potential for interference and confusing the multiple cells you're overlapping. FCC couldn't give a rats behind if it happens to screw up navigation equipment too. (Well, except where that nav equipment is also based on radio signals.)
Now, the FAA and airlines may also have a legitimate beef, and maybe even some regulations, but it's the FCC who will slap you with a heavy fine if they catch you doing it.
-- Alastair
Not really. There are tens of millions of wireless subscubers in America, how many are going to be in the air 'sucking up bandwidth'?
Cell phones only tune to one control channel at a time. When you are leaving the coverage of one cell, the network tells your phone which channel to switch to to get the next radio.
Don't think it would cause the collapse of the cell phone network, mmm k?
There is much cruelty in the universe, John.
Yeah, we seem to have the tour map.
Most analog cell phone transmissions occur between 800 and 950 MHz. Youre going to have a hard time finding a scanner than will allow you to listen to that range. If I remember correctly, there was a law passed in '93 or so which made it illegal to sell scanners with capability in that range, in order to protect the privacy of analog cell phone users.
;-)
The next time you are in Europe, stop by a local ham radio shop. Most European countries do not block the 900MHz band for general purpose recievers. That's where I bought mine! It even has the FCC ID, even though it is not supposed to because it is not to be sold in the States. I guess the company did not want to deal with the hassle of domestic and international labels. The one label has all of the testing marks ( FCC, CE, etc ). The FCC id makes it a hell of a lot easier to get through customs.
Yes, I have heard some very interesting phone conversations on that thing. Also, don't be chattering away too freely on your digital phone either. I know a guy who was a tech at the local wireless utility, and he had access to a nice little device which he could use to track CDMA calls. I am very careful about what I say on ANY phone network after that. It's too damn spookey listening to people converse like nobody is around. I feel like a ghost! BOO!
Remember, You are unique...just like everyone else.
What about the social aspects of cell phones?
I was on a train from Boston to New York (the new Amtrak Acela service), and for half the trip, the person in the seat behind me was chatting on her cell phone. That was not fun. At least at $3/minute, most people will make the airphone calls short.
I've heard that some commuter trains now have phone-free cars. Will airplanes need separate cell phone sections? Or perhaps just a noisy section (no cell phones or babies outside that section).
You know, I'd been using my cellphone in airplaces for quite sometime now, my provider hasn't said anything about it...and I pay them $30/mo for the service! Now I'm gonna have to find a fscking vacuum to talk in? Man, the nearest one is like 15 miles from here...but I hear it's expensive to get to, and you need a pretty important patron...but I hear the reception sucks :). Fix that headline Cmdr Taco.
So there I was. Naked. In a refrigerator. With a potroast on my knees. Smokin a cigar. That's when it got REALLY weird.
Can you provide a reference to your "recent studies"?
Yes, I can.
-- You see, there would be these conclusions that you could jump to
At the link below (which goes to TELECOM Digest V19 #457) is information which directly contradicts this newer (and apparently much smaller) study.
s /archives/back.issues/1999.volume.19/V19_% 23457
I believe that the tower-switching issue is genuine, but I find it hard to believe that personal electronics actually have an effect on jets (mainly because I've been on plenty of flights surrounded by people ignoring those rules -- and I've yet to be involved in a crash).
http://hyperarchive.lcs.mit.edu/telecom-archive
And they don't want any competition.
Notice that phone in the seat back in front of you
on the 737? The one you can swipe your card through? Even if cellular phones did work on
an in-flight aircraft, they would not want you
using them.
Somebody commented that "it would be nice" if you could use your phone while waiting to take off.
I often make a call from the plane while it's still on the ground. They don't tell you to turn them off until they "secure the cabin for takeoff."
-fb Everything not expressly forbidden is now mandatory.
Some years ago I was involved in a project looking at this kind of set up.
The problems are huge, and EMI is actually one of the more minor problems. You mostly solve it by using fibre or good co-ax for the cable runs and faraday cages for the electronics.
The big danger is fire. Every piece of equipment has to be certified to ensure that it won't start a fire, and if one does start that the equipment won't make things worse. Cabling is the big headache here: a cable conduit full of PTFE makes a wonderful channel for fire to spread and also creates lots of poisonous smoke. Cables need to be specially rated, as do the connectors.
Then the equipment must be safe in a crash. No broken glass, even when a passenger's head hits it. It also must not be able to fly out of the seat and hit the person in front.
It has to be cooled, even though the seatback component is surrounded by a good insulator. But at the same time it has to withstand Junior pouring his orange juice over it, and curious passengers with pocket toolkits (hello, you know who you are...)
It has to withstand vibration, pressure changes and temperature extremes (aircraft may be left parked in the hot sun or freezing cold). Components are rated for this sort of thing of course, but aircraft operation tends to put you in a corner of the envelope, and failures are therefore much more likely.
Finally you are on a strict power and weight budget.
Overall, a challenging collection of issues.
Paul.
You are lost in a twisty maze of little standards, all different.
Well... they are totally different.
Consumer RFI is not going to throw a 747 into a spin. The danger is that it will interfere with navigation sufficiently to cause an accident. For instance, missing the runway on an ILS approach.
A lighting strike is going to produce enough RFI, and even EMP, to interfere with pretty much anything electronic unless it is very well shielded. But its over quickly. Consumer RFI can last the entire flight.
Paul.
You are lost in a twisty maze of little standards, all different.
And I thought the airlines were just making all this up so people have to pay $5/minute to use the airfone in the headrest in front of you.
Paul.
You are lost in a twisty maze of little standards, all different.
--
Is it that easy?
Funnily enough, until recently I had laughed at the idea that mobiles would cause problems. Then, one day I put my Nokia 7110 down on my desk as it wandered off to some WAP site. I put it right beside my mouse and to my suprise the pointer started wandering across the screen. I've turned off my mobile in the terminal every time since..
We live in a confusing mess of EM signals all the time nowadays, plus of course all the natural sources of EM radiation add a considerable background level. So I'm surprised that there isn't shielding on the critical circuitry in a plane already.
On the other hand, the power of EM emissions from a mobile phone are orders of magnitude greater than the background levels. I also suspect that the superstructure of the planes act to channel the signal along the length of the plane rather than merely radiating uniformly out from the plane itself. This has implications for the positioning of critical circuitry in the plane itself - having such mechanisms at resonance points within the plane is going to make shielding either cumbersome or ineffective.
But this also must have implications for the future of mobile transmissions while flying. If people wish to remain connected to the internet or phone people on the ground, it's clear that the current technology quickly runs into difficulties both in routing the wireless mobile phone packets to the mobile phone towers and in keeping a strong EM emission from interfering with systems on the plane. So will we see an internal intranet made available inside the plane with some transmission system suitable for moving data between the ground and an airliner, possibly in the middle of an ocean? I could see a system arising using satellite uplinks and maybe adding Voice-over-IP to the mix to allow incoming/outgoing calls. We're already seeing a lot of Wireless LAN technologies arriving in offices, so I wonder whether we'll see some offshoot of that technology on our flights in the next five years.
Cheers,
Toby Haynes
Anything I post is strictly my own thoughts and doesn't necessarily have anything to do with the opinions of IBM.
Agreed. The one car accident I've ever been in was when I was trying to dial a cell phone and I rear-ended some mexican lady. She proceeded to sue me, but I never found out what happened with that lawsuit since I left for college before it was sorted out. That was 2 years ago :-)
--
The simplest problem, and also probably least likely to affect the plane, is passive non-linear antenna radiation. Basically, an antenna connected to a non-linear passive device can re-transmit the incoming RF at sum/difference frequencies (IM distortion anyone?). Although these re-transmissions are far below the incoming RF signal strenth (and most likely the noise floor) and not likely to interfere with the aircraft.
The bigger problem comes from a powered heterodyne radio receiver. Ie, a receiver (like a standard FM radio) that down-converts the incoming RF to an IF. The mixer on board the receiver doesn't have perfect isolation, so some of the produced IF (which is heartily amplified) will leak back through to the antenna, which can re-transmit. (FYI, a mixer multiplies the incoming RF with a synthesized LO (local oscillator) to produce output at the sum/difference of those two frequencies. Work out the trigonometry if you're bored, it's pretty cool.) Once again, the re-transmitted IF power is pretty small, but it is produced, and may interfere with the aircraft's receivers. And seeing that most IF's are in the range of 10 MHz or so, there is much opportunity for interference, almost independent of device RF frequency. This is why many radios are not allowed during flights, even if they're receive only.
That's why the aircraft-certified electronics are so expensive. (example - compare prices of a marine GPS unit versus an aircraft GPS unit). The aircraft units have had many resources spent to properly shield them not only from incoming RF (other than the GPS signals, of course), but also for outgoing IF re-transmission.
This IF effect has it's beneficial uses, too. For instance, one of my coworkers lost his RC model airplane when some wind gusts picked up while he was flying it. One of his friends grabbed his multi-element yagi antenna, tuned his receiver (non-heterodyning) to the IF frequency, and by scanning around (and using variable attenuators) they were able to track down the plane. Even though it wasn't actively transmitting any RF signals!
make world, not war
Okay, now I'm a little concerned. Smuggling a bomb on an airplane is a very difficult thing to do. What ISN'T hard it shipping a crate of electronics equipment designed to give off a wide spectrum of high energy radio waves.
What's stopping a terrorist from cargo shipping an electronics system designed to take down one of the older planes? How would the airlines respond with a threat to turn on such a device? Would they even believe it?
Many of the "older aircraft" have been retrofitted with newer avionics and "glass cockpits," essentially computers which ease many of the navigational and aeronotical chores pilots have to do in various phases of flight.
;-)
When the planes were originally designed, sans faraday cages and the like, they didn't need them, because the old, standard navigational equipment (VOR receivers, DME, ADF) didn't require them. For that matter, neither did the flight instrumentation: most of it was (and, in the smaller planes those of us who fly for fun use, still are) mechanical, using vacuum driven gryroscopes, static air inlets, a pitot tube to measure air movement (and thus airspeed). My standby vacuum system is electronic (as are the lights on the panel), but the primary vac system uses induction and works even with the electronics shut off. The plane flies just fine, and one can still navigate using pilotage (their naked eyeball).
The newer aircraft are designed to require the fancy electronics, but even they still have the old, familiar instruments most of you know from PC flight simulators.
There was an aircraft in Canada (I forget the model) which was landed safely after it ran out of fuel midflight and lost all flight systems, except the basic, gyroscopic instruments just about every aircraft since the 30's comes equipped with.
Loss of navigation is only a life-threatening concern in situations of low or no-visibility, such as the middle of the ocean (which way are we supposed to fly?) or in IMC (bad, foggy, rainy weather, now we can't fly the published approach, how the f*ck do we find the damn runway?). Even then, a quick call on the cell phone to the tower can probably get you the guidance you need (which is what I would do if I lost comm while in the soup, the FCC be damned).
The Future of Human Evolution: Autonomy
... and *NOT* a legal one.
A number of people have pointed out that it's illegal to use cellphones on aircraft anyway. And then there're the similar restrictions about discmans, gameboys, laptops, etc.
"RF frequency can disrupt navigation / autoland / whatever, so let's ban electronics either completely or just during takeoff / landing." Yeah... Grrreat idea!!!
What people who say "it's illegal anyway" overlook, is the fact that there is just about always some yahoo who thinks that the rules don't apply to him.
They'll use those tiny headphones and keep the discman in their pocket. Or they'll use a headset with their cellphone (till the plane climbs out of cell tower range). Or they'll hide the game boy whenever a stewardess gets near. Or they'll say they're using a Palm III when it's really a Palm VII. Or mabye even, they don't mean to break the rules at all, but they just leave the cellphone ON during the flight (those suckers *DO* transmit even when you're not in a call, ya know).
You know it'll happen, no matter what laws or rules or regulations you impose, and whatever safety guidelines you publish, and no matter how many times you tell someone. It WILL happen.
And that's why the FAA needs to dump those "RF on an airplane" rules, and mandate a technological solution.
john
Imagine all the people...
Let's take an example. I'm not saying this is how it is, or anything like that, but it's a possibility. An example of how studies can appear to show cause even when they don't. There are certain groups of people who tend to use cellphones more than other groups. Figuring highly in the group of phone-users are business people, the ones who are always on their phone so they can keep in touch with the home office and stay informed of any changes. These people tend to lead more stressful lives than average. High stress has been shown to lead to heart trouble. It's not entirely farfetched to say that maybe high stress can cause or at least influence brain cancer as well. And there we have a situation where there is a high correlation of cell-phone use with brain cancer, and no causal effect at all. If these people stopped using their phones but otherwise continued on with their lifestyle before (assuming all I said above was true, and I claim no such thing, remember!) then they would still be at the same risk for cancer. Now, I am not saying that the causal relationship is false. However, you need to look beyond the obvious silliness of tumors causing cell-phone use before you can dismiss any causal relationship beyond the one you seek.
Mod down posts with a "Free Mac Mini/iPod" sig, they're spam!
My point is that, at the time they were built, there was no idea that EMF could be a problem. I mean, even the radio navigation system we have in place today (and the reason you can't use electronic devices during takeoff and landing) wasn't conceived until long after many of these planes were built. At the time, most of your navigation would be by maps or, at most, very non-sensitive navigation devices (ADF, etc.). Instrument landing and the percise navigation devices required to work around JFK in the states, or even Person International in Toronto couldn't have been taken into consideration with the building of the plane.
Hmph... additionally, cellphones are bad for use on airplanes for another reason too. At higher altitudes, you can get direct line-of-sight contact with many towers at the same time, which messes with the system emmensly (which is why it is outlawed, afaik, by both Canadian and American (FCC) authorities.
Just my $0.02 CDN worth from experience.
-legolas
i've looked at love from both sides now. from win and lose, and still somehow...
The use of personal electronic devices on aircraft has been debated a lot in the literature. The issue is resonance. An aircraft cabin is basically a long metal tube. So if your laptop hard disk puts out the right frequency, the signal may be amplified and interfere with the electronics. One result I've seen (I think this was IEEE Spectrum) is that a laptop hard disk put out the same frequency used by navaids. There is no consensus on this, so the FAA takes a conservative stance.
As for Hemos' suggestion of Faraday cages, the issue is really cost. How much more are you willing to pay in ticket prices to haul around a cage so that a few passengers can play Doom? Also, remember that the flight instruments are housed in the same metal tube, so you'd have to put a second cage around that section of the aircraft. And I suspect it is far easier to say, "put a cage around it" than it is to actually do so. For one thing, people kind of like those pesky windows...
Weight is such a big factor that aircraft manufacturers went to Kapton wiring because the insulation weighed less. And yes, all the wiring is sheilded. But I can tell you from firsthand experience that even twisted, sheilded pairs driven by differential transceivers are affected by impressed noise.
Have you ever seen an RC plane take a 'radio hit' from some else's transmitter? Same deal with PED's; you'll never know what frequencies are being emitted, so why take chances?
This is a boring sig
It involved a passenger listening to an FM radio while a plane was on an instrument approach in the 1950s. The local oscillator leakage caused a false indication on one of the ILS (Instrument Landing System) instruments (I think it was called the localizer). The VHF aeronatutical band is just below the commercial FM band, by the way.
Anyway, the plane crashed, the NTSB figured it out, and then made the rule about electronic devices.
Fortunately, all commercial jetliners now use inertial navigation systems, so this particular failure mode is much less likely. A terrorist would not be able to crash a plane in this way. ILS systems are still in use, however -- and nobody wants to find out about another electromagnetic compatibility problem via an accident investigation.
Cell phone interference to airliners has been discussed there extensively.
For those of you who work where they're considering replacing a real OS installation with Windows NT, consider this post I contributed:
USS Yorktown dead in water after divide by zero
The Yorktown has to be towed back into port after a sailor entered "0" into a data entry field and it crashed the ship's entire NT network.
Mike
-- Could you use my software consulting serv
Let's get this straight, folks. Photons from cell phones (or power lines as well, for that matter) do not have even a fraction of the energy needed to generate free radicals such as singlet oxygen (responsible for most carcinogenic genetic damage), let alone to break peptide bonds directly. In short, cell phones are incapable of damaging DNA or creating chemicals which can damage DNA. They might cook your flesh if operating at sufficiently high power levels (which they don't), but they won't cause cancer. For that, you need ionizing radiation (UV and up...). Saying that cell phones can cause cancer is like saying that the wake from a surfboard can capsize a supertanker.
If you are really worried about cancer, stay out of the sun, watch what you eat, and don't smoke. And try not to worry about the fact that there will still be a one-in-a-bazillion chance that one of the numerous stray cosmic ray gamma photons constantly bombarding your body will happen to nail the telemerase inhibitor in one of your cells and turn it cancerous...
I want to know how the electronics on a plane can get affected by the output of a cell phone, and not get totally roasted by flying through a lightning storm!