The Real Reasons Phones Are Kept Off Planes

jcatcw writes "Mike Elgan argues that the the real reason that cell phones calls are not allowed is fear of crowd control problems if calls are allowed during flight. Also, the airlines like keeping passengers ignorant about ground conditions. The two public reasons, interference with other systems, could easily be tested, but neither the FAA nor the FCC manage to do such testing."

funny

this is funny because he missed the obvious and actual reason. most planes ive flown on have had a phone on the arm rest with a little slot to swipe your credit card.

Re:funny

Actually, ask anyone that knows how cell towers work, and your real explanation would become evident. Cell phones try to communicate with as many towers at once as possible, this is required so that you can walk from one cell's coverage to another's without dropping your call... a typical phone sees anywhere from 3 to 6 towers at once depending on geography and density of cell towers. Throw that phone up a few thousand feet, and I've personally seen my blackberry connect to 40+ towers at once. This eats up valuable bandwidth at each cell tower, not to mention the fact that you come in and out of a cell's coverage area so fast that it's impossible for your calls to be handed off properly between the cells.

Oh, and good luck with the E911 crap... In the course of a minute, you've gone from the east end of a major city to the west end according to the cells.

Re:funny

Oh, and good luck with the E911 crap

I think that if you have to call 911 from a plane, them finding your location is the least of your problems.

Re:funny

I think that if you have to call 911 from a plane, them finding your location is the least of your problems.

Yeah, you better watch out for the snakes instead.

Re:9-11?

I think the plane crashed because they all used their cell phones.

Re:funny

Actually, ask anyone that knows how cell towers work, and your real explanation would become evident.

Exactly. Every other explanation and excuse is crap. Unfortunately, solid technical reasons are never enough for most folks.

Re:funny

Oh, and good luck with the E911 crap... In the course of a minute, you've gone from the east end of a major city to the west end according to the cells.

Hello operator, I need a fire truck with a REEEALLY long ladder.

Though if things are that big an emergency, when they need your location it'll be "that big smoking crater".

Re:funny

Yep. The coverage of even a small, low-powered VHF radio increases dramatically when operated from an aircraft.

In the U.S., Class A FM broadcasting stations are limited to a power of 6,000 watts at a maximum antenna height of 100m. Higher antennas are allowed if the power is reduced to compensate. [fcc.gov]At an antenna elevation of 600m, power must be reduced to only 150 watts (?!) to achieve the same distance coverage. Translate those figures to a cell phone with a rated power of no more than 3 watts, and you're talking about limiting power to 0.08 watt at 600m.

Of course, commercial aircraft fly a LOT higher than 600m!

The cellular network has far more subscribers than it has channels. To work, it depends on the ability to reuse a channel throughout the service area. If I place a phone call from my home 40km northwest of Nashville, the same channel can be reused in downtown Nashville, and on the city's west side, and in Donelson, and Brentwood, and Smyrna, etc., etc... My phone, about 1.2m off the ground, has a range of only about 6km.

If I place that call from an airplane flying 8,000m above my home, every base station in the greater Nashville area can receive my signals. Now, "my" channel cannot be reused at all.

If it were just me, that wouldn't be a problem. If it were, say, 10% of the passengers on each flight - well, I don't think it's hard to see how that could use up all available channels in a hurry. New channels aren't cheap. Nextel is paying to replace [2ghzrelocation.com]almost *all* the microwave remote broadcast equipment in use by U.S. TV stations, so they can free up some remote broadcast spectrum for use as cellular-telephone channels.

Here's an idea: allow calls from aircraft, but allow cellular providers to charge enough extra for airborne calls to cover their costs in adding more channels. I'll bet after the next billing cycle, the number of calls made from aircraft would plummet!

re; Are you *sure* this is still an issue?

I've seen that same explanation stated several times before when this discussion came up. But the last time I read about it, I believe it was a message thread on HowardForums.com - a site specifically made to discuss cellphone technology. Many users there work in the industry in one capacity or another. One of the guys who claimed he worked on engineering the cell tower infrastructure said that this is really not a true statement. Yes, the phones are designed to communicate with any towers within range. BUT - the cell towers have the ability to handle situations such as a phone suddenly "appearing" on 40 towers at the same time. They have software that knows such things aren't possible in normal cellphone operation at ground level - so it ignores the signals on all but a few towers at a time.

He claimed that in reality, this process doesn't "tax" the towers inordinately at all. The "bandwidth" tied up is no more than a regular call would tie up, since the towers are rejecting the extra instances of the connection to the phone. There's simply a small amount of overhead involved in the towers passing along the information to each other about the status of your connection.

(I believe this type of software also comes into play for handling problems of "cloned" cellphones. If a connection shows up simultaneously on towers that are spread far apart, they know they're dealing with not just 1 legitimate phone, but also a duplicate in service elsewhere.)

Re:re; Are you *sure* this is still an issue?

On any kind of cell phone, you're only connected to one cell at a time.

Let's say your phone is connected to Cell A and is talking on channel 375. You aren't using Cell B. But you are using channel 375. If Cell B tries to assign channel 375 for someone else's call, your phone is going to interfere with theirs. If you're flying at 15,000 feet, you're only going to tie up one cell at a time -- but you're going to tie up channel 375 for as far as 100km or more.

Re:funny, most inseatphones are not active.

With no players anymore in the US, Verizon out and aircell now offering Wifi instead of phone calls, this is not a reason.

Also the only phones still avaliable on planes are run by ARINC and SITA, which both now have a picocell replacements under testing for installation this year.

There is no technical nor marketing reason you can't have a cell phone on board, if cell phones were a real danger then they would not be in carry on allowance anymore.

FAA is very conservative, and the FCC is a political body.

That is all

Re:funny, most inseatphones are not active.

If cellphones were really really dangerous, we'd have aircraft graveyards everywhere, especially around airports.

What do cellphones talk to? Cell towers. Where are those towers? EVERYWHERE, and they all operate at much higher power levels than any handset.

If there was some sort of danger, cell tower signals from the ground -particularly towers near airports where they are always A LOT of such towers- would be knocking planes out of the sky on an hourly basis from miles away. Every airliner in the sky flies over hundreds of these towers on every flight. It would be like the worst anti-aircraft fire ever devised.

But it doesn't happen.

And cell towers are hardly the most powerful transmitters in the wild. A cell tower throws out a couple watts. A TV transmitter can throw out a million watts and there are thousands of those towers too.

Aircraft operate happily amid a sea of RF and generally nothing goes wrong. So the idea that a wimpy little cell handset are threats are just overblown assumptions, unproven and unrealistic.

Not quite

My father is a retired Pilot (Air Force, then the American Airlines). Since I used to work for Jeppesen, we have had some interesting conversations about this. He has said that he has seen nav equipment messed with that the FAA said was cell phones. Now it was early 90's, and likely to be one of the analog phone, but they were not certain. But some of his old co-pilots (now all senior captains for American), says that several instruments will be interfered with from time to time and they believe it to be cell phone. In general, they claim that most of the interference occurs on the ground (i.e. as soon as the phones are turned on). Now, I do not know why that is, but I would want to make certain before allowing them to be used. It is possible that it is just one frequency or type of phone that is causing the issue. My question is, why has the FAA not determined where the issue is? ALPA is actively pushing against allowing the phone usage until FAA or FCC can explain what is causing this.

Re:funny

I'm pretty sure I don't agree with the crowd control theory either.

In the six years I worked at an airline, I've never heard anyone speak of passengers as negatively as this article does.

Too true

They should ban kids from carryon luggage and make parents check them.

Re:funny

I would rather insert actual satellite phone rates. Iridium is a satellite network provider. Their phone airtime rates can be found here [infosat.com]

Looks like the cost is about $1.29 / minute. I don't know what kind of phones they might use, but a basic phone costs about $1500 according to here [telestial.com]

Re:funny

To certify every cell phone to be safe in flight would require a lot of study and creating new standards, restricting the design criteria of avionics and testing of every possible cell phone model. That could be pretty darn expensive.

Not to mention that we live in a global world; how do you certify that a Chinese passenger's Chinese cell phone doesn't interfere with a Russian plane's avionics flying into the US? Getting everyone on the planet to agree to these things is a pretty impressive challenge.

Re:funny

If a Russian plane flies into the US it has to be certified by the US. That usually means either Airbus, or Boeing or some other smaller plane manufacturer that has already been certified. If you want an interesting flight (my brother tells me this) fly in Russia using a domestic airline.

Cell phones are already tested for interference because otherwise they would interfere with other devices. Cell phones are certified to use regulated bandwidths. It's walkie-talkies and cordless phones that you need to be worried about since they use uncertified spectrum's.

The reality is that most of these things have already been verified as that is why you have little stickers on the back of the device indicating that they have been certified. And interestingly enough most countries have similar certifications because otherwise they would have wireless nightmares.

Re:funny

Cell phones do interfere with other devices - that the nature of all electronics - especially ones in which radio transmitters play a leading role. There is no getting around the fact that cell phones create radio 'noise'. Yes, they have been tested to make sure they are only creating radio emissions to some agreed upon level in the band/frequencies they are licensed to transmit on, and some (lower) agreed upon level outside of that band. However, certifying electronics for use on-board planes is a little more of a dicy issues - because the mere possibility that booting up your laptop during landing might generate enough noise to screw with the GPS, or the ILS systems that are helping the pilot guide the giant metal tube full of jet fuel and fragile humans to a concrate surface is a scary enough scenario that the FAA has decided its easier to just have a blanket ban on such things during take-off/landing. The ban on cell phones is a similar conservative (or paranoid if you prefer) move: its easier to say its not allowed than to test its enough to be reasonably certain its safe. In reality modern digital cell phones inside a modern jet could be perfectly safe - but there are a large number of models of airframes out there, and a much much larger number of cell phone models - many of which can operate in several different modes and corresponding frequencies. Certainly I'd prefer they spend the time to check it out some more so that in the future they can certify my cell phone is safe to use on the particular plane I'm stepping onto so I can talk during particularly long flights. In the meantime I have to wait until the plane taxis to a full stop by the gate before powering it up and making the call to say we've landed. An inconvenience, but I don't mind the fact that they're focusing more energy on the making the plane safe part and haven't devoting their full energy to making it easier to make phone calls during the flight part.

Mythbusters already did it.

Back in season 3:

"It was found that cell phone signals, specifically those in the 800-900 MHz range, did interfere with unshielded cockpit instrumentation. Because older aircraft with unshielded wiring can be affected, and because of the possible problems that may arise by having many airborne cell phones "seeing" multiple cell phone towers, the FCC (via enforcement through the FAA) still deems it best to stay on the safe side and prohibit the use of cell phones while airborne." -Wikipedia

You can read more about it here: http://kwc.org/mythbusters/2006/04/episode_49_cell phones_on_plane.html [kwc.org]

Re:funny

The truth is that:

1. Old airbus models had severe interference problems from old pre-GSM cellular network phones. That has been confirmed many times. I have seen that myself in the early 90-es.
2. No test has ever proven any GSM phone to interfere with plane equipment (do not care about the US ragtag of network spagetty).
3. A modern GSM base station (and EU style 3G node B) is small enough to be put on a plane. If there is a local BTS it can enforce power control criteria on any phone which it camps on. Further to this, there is at least one reject code which will shutdown and lock up a phone solid with its radio off (only really old Samsungs violate the spec and reboot, rest follows it). So having phone support and local kit on the planes is actually beneficial as it allows airlines to ensure that "interfering" mobiles are powered down to their lowest possible transmit power or are outright off.
4. The commercial reason for not having mobiles on planes is easily resolved once again by putting basestations and the airline entering into a special roaming agreement with an operator. Plenty of Timbuktu GSM operators to do so, some are actively looking into entering these partnerships. Once again - the US ragtag of cellular non-standard networks is the loser. The airline skims a portion of an outright exorbitant roaming fee and everyone is a happy camper. There is a number of airlines that already have the kit in place and/or are testing it. There are also more than one company producing these as well.

So it all boils down to crowd control and to the airline ensuring that it does not end up on the receiving end of a lot of angry customers who have just received a 90$+ phone bill for a 10 minute call from the inlaw while on the plane.

This and the fear of "organised terrorists". Not that it is possible as the current generation of kit will run any voice channels all the way to the ground and back for an in-plane call. As a result anyone trying to organise a "terrorist attack" will simply fail as the plane will run out of channels to the ground right away. This is also the reason why the producers of this type of kit keep targeting the plane market and not the much more lucrative cruise ship and ferry market. A cruise ship is not subject to stupid FAA restrictions, but it has a disproportionately large proportion of local calls (where are you, I am in bar on level 7, ok, I am on level 3).

I don't buy the crowd control thing

There are already enough planes that have satellite television (including news channels) along with air phones (at a very high cost - yes but still a source of information.

The real reason? Its bad enough when people are yapping on their phones constantly on the ground. Getting stuck on a plane near someone who won't shut up on the phone is MUCH MUCH worse due to the duration and the captive audience. For that reason I hope cell phones are never allowed (and if they are it should be a cell phone only section kept reasonable sound proof from the rest of the plane).

Re:I don't buy the crowd control thing

Reception is very weak at best in mid-flight anyway. The only decent way to prevent people from using the phone on ascent or descent is to take them away, or better, turn the passenger cabin into a faraday cage.

I think it was Jet Blue that had the situation where passengers could see the news about their flight through satellite TV, something about damaged landing gear. I don't remember anything about a crew or passenger mutiny in the news reports.

Re:I don't buy the crowd control thing

You are indeed correct. JetBlue landing gear mishap [msn.com].

Re:I don't buy the crowd control thing

I believe this hits the real point. I travel a fair amount on business and spend enough time in airports to know that there are a significant number of people who would probably talk on their phones as continuously in flight as they do on the ground if given the chance, and these aren't just businesspeople. Either way you handle this in flight will be a problem. If cells can be used anywhere on the plane, there will be a big backlash of annoyed passengers; if they are confined to a few rows, they will annoy and interfere with each other which will encourage many of them to ignore the row designations and still cause problems for others; plus even if they don't, it will still be a problem for several "normal" rows adjacent to the cell phone section.

Wifi on planes will be MUCH less of a problem in terms of annoyance to other passengers.

Unfortunately, the best solution is the one that is already in place on some planes - a public pay phone in the seat. It costs money to use, so people won't use it idly, but important business and personal calls that justify the cost can still be made.

Re:I don't buy the crowd control thing

People tend to talk louder on cell phones than regular phones. [npr.org] There is no feedback of their own voice.

Re:I don't buy the crowd control thing

People tend to talk louder on cell phones than regular phones. [npr.org] There is no feedback of their own voice.

Indeed. On regular landlines it's called "sidetone". It's an artifact of the single shared copper loop heritage of the POTS system that dates back to the 1870's. Cell phones lack sidetone because they use two separate circuits for transmit and receive. The problem arises from people not being self-aware enough to realize that the lack of sidetone is causing them to unconsciously raise their voices. I strongly urge all people to be mindful of their voice volume on cell phones. Seriously, consciously will yourself to use a low conversational volume level. You might be surprised to find people can understand you better.

Easily Tested?

It might be easy in theory, but you need to think of scale. Take all of the cellphone manufacturers, during the course of a year a lot of cellphones are released. So each year you have a lot of cellphones to test. Then, the test itself isn't so clear-cut. Sure, that 1-year-old 737 might run fine, but what about the 7-year-old 737? It might have less around the electronics, or casual wear-and-tear might have left an opening. Put both factors together, and testing isn't so easy. Sure, it's possible but is it really worth the effort?

Not easily tested at all

It's worse than just the combinations of phones and planes. An aircraft makes a nice enclosed resonant space for cell signals to bounce around inside. Anyone who has looked at simulating or measuring RF fields would know that the field strength can vary by orders of magnitude depending on the exact location, orientation, and frequencies of the emitter and the exact orientation and location of the susceptible wiring or instrument. A tall person sitting in seat 6B with a CDMA phone may cause no problems, but a short person with a GSM phone in seat 32F could interfere with the automatic landing system. The field strength won't necessarily drop with distance inside the plane and may be focused to high levels anywhere inside the aluminum tube.

And testing individual phones isn't sufficient. What happens when 100 people all use their phones at the same time.

Has been tested

The effect has been idependently tested and confirmed:

http://www.post-gazette.com/pg/06060/662669.stm [post-gazette.com]

I think I'll trust real research from CMU over a vapid so-called journalist who probably just can't stand not yapping on his cell-phone.

BTW, it doesn't matter if some or even nearly all cell phones don't cause interference with flight controls. All it takes is one person using one that does and things get ugly. Likewise, most airplanes have a mix of avionic equipment. Some of it is new where the cost/benefit makes it worth it for the airline to upgrade and some of it is old. Rather than test each airplane independently, it makes more sense to just say "no" until someone comes up with a way that is known to be absolutely safe regardless of the equipment on the airplane.

Cheers,
Dave

And on Page 2, the real real reason

Crowd Control? People getting annoyed at other people using cellphones? Perhaps historically, but look at page 2:

 

"However, the airlines know that some kind of plane-to-ground communication is coming, and they want to profit from it ... Airlines would prefer that phones be banned while they come up with new ways to charge for communication, such as the coming wave of Wi-Fi access"

Bingo!

however:
 

"So the ban remains in place because the government can't seem to come up with definitive answers."

you know, I'd rather the government (of whichever country) err on the side of caution, actually: "Well, we can't tell whether cellphones might cause crashes, so we'll just allow them and see what happens"?

Bottom line for me: people are annoying with cellphones. Now imagine sitting next to the guy talking shite for all 12 hours of a long haul flight. I'd hijack the plane just to shut him up. Keep the ban, people can surely live without cellphones for the duration of a flight... surely?

Billions and billions

If gadgets can't crash planes, then the ban is costing billions of hours per year of lost productivity by business people who want to work in flight.

What the author completely fails to address is the noise that ensues if you have ten businesspeople in first class all "doing business" on a cell phone at the same time. Are they supposed to wander the aisles and pace as they talk? Or merely talk over one another in increasingly loud voices?

There's something about a long tube that seems to suggest to people that maybe conversation should be kept to a minimum. Not only planes, but buses and subways and trains too. In my experience riding public transit, most people do not chatter on their phones endlessly. In part, I think, because there's an unconscious realization that the guy standing 6 inches away (that you can't move away from) does not want or need to hear your prattle.

Re:Billions and billions

It's not an unconscious realization, it's common freakin' curtesy. But out of the thousands of people who fly each day, there's still going to be hundreds of ignorant assholes who are either too self-absorbed to realize, or to selfish to care. Flying is already an intense and intimidating experience for many people, long flights are generally uncomfortable and borderline miserable. Ever ride on a plane with a baby in a nearby seat? That can be annoying as all hell, but babies cry, they can't know any better, and so I deal with it. But if someone was talking loudly on their cell phone for a half hour, subjecting everyone around them to half of their conversation, I just don't know if I could take it.

As for billions in lost productivity (that number sounds rather high to me) because of people flying, big freakin' deal. Businesses have existed for thousands of years without cell phones, a few hours disconnected here and there won't put our economy into a recession.

Cell hopping?

I was always under the impression that a mobile phone travelling at 500+ mph on a plane would be hopping from network cell to cell fairly regularly (once every few seconds?). This sort of frequent handover would then a) make it difficult to make, receive and conduct a call and b) cause issues for the phone networks if you've got num_people_per_plane * num_planes_in_sky_over_country people's phones all doing the same hops fairly regularly. Meh.

Author is an idiot; the carrier reason is valid

Mike Elgan, the article's author brushes off the problem of an airborne cell phone seeing a large number of cell towers at once. He claims it could be easy to fix with a software upgrade to the towers. Nonsense. The fundamental problem is that there is only a finite range of frequencies for cell phone calls. The more towers a given phone's signal is visible to, the more towers whose frequencies you're chewing up. Redesigning the system to support cell calls would be massively expensive. Is the value of being able to make cell calls from a plane really that valuable? Who is going to pay for the overhaul? Elgan is just whining.

Elgan points out that Europe is working on making this work. Tellingly, they're not just letting the phones connect to towers normally; they're shielding the cabin and routing connections through dedicated on-plane hardware. This is reasonable as it means you have a single source (the plane's hardware) that can far more efficiently utilize tower frequency space. Furthermore, the cost of making the changes falls on the airlines, who will pass it on to the logical people: the fliers who want to use this service.

Response from a Pilot

I posted this to the original article as well, but I felt the slashdot community might derive some value from it as well. The interference issue is a VERY real one. I can't emphasize this enough. It's easy to debate this issue on the ground, but try debating it 2 miles above the ground when your only lifeline is a thin needle on a panel that is controlled by a radio transmitter on the ground. I have a personal experience with cellphone nav interaction. I've also watched the mythbusters episode. Everyone here knows that mythbusters, while entertaining, is not entirely scientific. I certainly am not willing to stake my life on the thoroughness of their conclusions.

Without further prefacing, here is my original post:

You mention in your article that "Many headsets used by private pilots come with jacks for using them with cell phones. The manufacturers say they're for use on the ground only. But many private pilots use them in the air without incident."

I fall into this category. However, I've also seen the dangers of airborne cell phone use. I carry a Nextel branded Blackberry. From my experience, it's not a very good phone to use on board an aircraft. About every 20 minutes or so, the phone goes into a signal frenzy. It's as if it finds multiple strong towers to connect to and is unable to choose. This results in a barrage of beeps and lights while it tries to figure out what's going on.

Furthermore, the risks of interference are very real. When I'm using the phone, I never notice the interference. I recently let someone else use my phone and was very surprised. My headset (flight radio headset) emitted a horrible scratching noise. I was totally unable to hear anything on the radio. I quickly looked at my VOR (radio navigation, NOT a gps) , and noticed that it was off coarse as well. Now, had I not been certain that I was on the right course, I might have well thought I was off course and corrected in an ultimately wrong direction.

I'm not sure if you're familiar with VOR technology, but it's the primary aviation navigational aid. GPS is wonderful, but it's still not the primary navigation mechanism. GPS is considered a "non-precision" navigation tool. VOR and ILS are still the primary mechanisms and they are dependent upon terrestrial radio transmissions. This is where the cellphone interference comes into play. Most cell phones operate in the 800mhz range. I'll save you a lesson in radio technology by simply stating that they can often have harmonic emissions in the same bands as used for aircraft navigation.

While you state that countless numbers of phones are left on during flights, this is not particularly dangerous. A phone ranging a tower is only actively transmitting for a very short period of time every 20 minutes or so at regular speeds. A phone that is in active use is a source of radio emissions that is in VERY close proximity to the aircraft communications and navigation antennas and is operating on a frequency that can have interfering harmonics. I have personal experience with the reactions a nav needle can have to a cellphone.

Imagine if the weather was bad (instrument meteorological conditions or IMC) and you were trying to land a large passenger airliner using nothing but a small needle on the panel to align with the runway. Then, a passenger starts talking to their uncle Bill about his bypass surgery and that needle jumps even 10 degrees off position. Now, instead of aligning with a runway, you're aligning with a corn field.

To answer your thoughts about shielding, that's not a viable solution. You would either have to shield the passenger cabin from radio emissions or shield the comm/nav antennas from it. In either case, the shielding to protect them from each other would seriously impair their usefulness. A passenger cabin shielded from RF emissions wouldn't allow your cell signal to get out, thereby negating the purpose. Shielding the comm/nav antennas sounds like a good idea until you realize that oftentimes nav aids and aircraft controllers a

For an article with *real* research done...

From the IEEE's Spectrum magazine last year, they actually measured RF signals on flights and reported on the results. No smoking gun where an accident was caused by a cell phone, but still interesting nonetheless (and no ads!). http://www.spectrum.ieee.org/mar06/3069 [ieee.org]

Crowd control argument makes no sense

I just flew on a bunch of different planes in the past week, and a couple of them had the control tower chatter actually broadcast on one of the channels of the in-flight entertainment system.

It was actually pretty cool to hear the various airplanes yak with the tower. O'hare is a busy airport (to say the least), and it was astounding to listen to them juggle all the incoming planes. What was particularly funny was listening to them berate our pilot - the guy mumbled a bit, so the flight number kept getting cut off. The tower had to repeatedly ask him to repeat, and eventually they started making fun of him. Things like "well, this particular pilot doesn't feel he's important enough to respond to us". Tres droll.

Also cool was listening to the tower give directions (turn left, etc) and feel the plane immediately respond. All in all, it sounded pretty much exactly like it does on TV/movies. I'm sure if there were any actual flight emergencies, it would have been broadcast for the passengers to hear - unless there's some protocol to shut that channel down when things go amiss - which would just alert passengers to a problem anyway.

Interference is not an urban legend

TFA says:

Also: If real testing were done, and the nature of the problem fully understood, it would become obvious that airplanes could be designed or retrofitted with shielding and communications systems that would enable safe calling through all phases of flight. But that would cost money.

Real testing has been done. Unintended emissions from the phone have been identified as the culprit, not a deficiency in the navigation equipment. The aircraft's receivers are doing exactly what they are supposed to, responding to signals of certain frequencies arriving at the antenna. Once the phone pollutes the spectrum with spurious signals, nothing can protect the receiver. The shielding and filtering must be applied at the problem, which is the phone. Since the competitive consumer phone market demands the lowest possible cost, once a phone meets the minimum legal requirements they won't add another dime of product cost for further interference control.

Intereference does not occur every time, but when it does occur there has been a demonstrable cause and effect relationship. Start with this NASA case study [nasa.gov](long pdf warning).

In July 2003, it was reported to the Federal Aviation Administration (FAA) that a cellular phone when turned on simultaneously interfered with three different aircraft GPS receivers, causing complete signal loss. The three GPS receivers were using three separate antennas, and were installed on a small aircraft. The phone was on, however, calls were not made during the incidents and subsequent tests. [emphasis added]

In an email message to the FAA, the company who owned the airplane reported the subsequent tests taken to prove a clear and convincing direct relationship between the phone being in ON-mode, and interference with the three onboard GPS systems. The company verified several times, in multiple flights over different days, that the interference problem could be recreated reliably in the air by having the phone turned on. The interference disappeared when the phone was turned off or covered behind a metal object, and re-appeared when turned on or brought into the open again. In addition, the company conducted tests at two different places to ensure that it was not dependent on location, and were able to reproduce the interference effects at both. The interference occurred when the plane was in the air, but not on the ground. Tests using other phones did not create interference problems on the same aircraft and systems.

Then consider this article from Spectrum [ieee.org]. On page 3:

Our data and the NASA studies suggest to us that there is a clear and present danger: cellphones can render GPS instrument useless for landings. Clearly, the cause of the problem is that the FCC issues RF emission standards for consumer electronics, conferring only minimally with the FAA and with no formal consideration of the implications of those standards for the aircraft environment. For its part, the FAA relies on the airlines to initiate safety plans and, like other government agencies, defers to the FCC on questions of electromagnetic radiation.

And from page 4:

All in all, we found 125 entries in the ASRS [Aviation Safety Reporting System] database that reported PED interference. Of these, 77 were considered highly correlated, based on the description of observed PED use and interference occurrence.[emphasis added] The reports included cases of critical aircraft systems such as navigation and throttle settings being affected. Based on the random sample entries from 1995 to 2001, we estimate that the average number of reported interference events might be as high as 23 per year.

It's no conspiracy, and no urban lege

What I want...

So this is like.. tangentially OT.

But, how much money could I make if I started a business that installed Faraday cages into movie theaters? Could I completely block all cell traffic with one? And could I install the cages relatively cheap and keep them invisible? See, I know there's been talk amongst movie theaters of using jammers to stop cell phone use. But the FCC is against that and it doesn't look like it's going to happen. But can the FCC stop me from constructing a faraday cage around my theater to 'ensure the highest degree of fidelity of the digital projection equipment, thereby ensuring the best viewing experience'?

I'll tell you what, if I know one theater in town has faraday cages and the others don't.. I'm goin to the one with the cages.

A lot of people argue that they need their cell phones during a movie in case of emergency situations. I think that's bullshit. For decades people managed to go to movie theaters without cell phones. They accepted there might be emergencies happening that they weren't aware of until after they left the theater. They accepted this because whenever an emergency happens and you are twenty minutes from the scene you are 99% of the time too late anyway.

Someone enlighten me here, what kind of emergency can you really expect to respond to fast enough to make a difference by racing out of a theater to the scene of the emergency? By the time you get there either the emergency is over or people who are supposed to handle that sort of thing (you know, EMT, Firefighters, professionals...) have already done so. But please, give me an example of how I could be wrong. I'm curious. There has to be something.

TLF

probably ineffective anyway...

IIRC a cell tower covers a geographic area of 36 sq mi, and assuming that's a circle (I know they effectively chart them as hexagons, but...) if that's true, the radius, given pi r ^2 for area, sqrt(36/pi) = 3.64 miles. That's only 19,000 ft. Sure, straight line would be better than terrestrial terrain, but above 19,000 you're heading out of range anyway, not to mention rapidly switching cells (400 mph = 6+ mi/sec)

If that were the case, it'd be torches and pitchforks for the cellcos if they allow it and then it sucks.

Testing Isn't Easy

Speaking as someone who's tried to get gear flight certified, I can tell you that testing is never easy. Granted, it's definitely easier to get something approved that isn't going to be part of the plane but rather just another carry-on, but there's still a lot of work involved.

I think it probably boils down to cost and caution. The testing is expensive, and nobody wants to be the one that approved cell phones if they end up causing a plane crash.

What about TVs and GPSs?

I fully believe that cell-phones can interfere with aircraft nav systems (the fact that they interfere with PC speakers and conference-call microphones is plenty of evidence for me).

However, there's also a restriction on hand-held TVs/radios and GPSs, and I've always wondered why, since they're all receive-only. I don't see how it's possible for them to cause any interference (or at least no more interference than a laptop computer) since they're only picking up on signals that are already passing through the plane from an external source.

So, does anyone have any info on why those are banned as well?

TSA should therefore confiscate cell phones.

If cell phones and two-way pagers indeed had the ability to interfere with aircraft to a point where it compromises safety then the TSA should be confiscating them rather than bottled water and toothpaste. At least it's a more plausible threat than "liquid explosives". Perhaps the fact they are *not* confiscating them is telling.

Actually I'd like to see that. Confiscating a bunch of inexpensive water bottles in the name of security is a relatively benign way of maintaining the appearance of security. Being willing to risk massive public fallout by confiscating expensive cell phones would show they are actually serious.

Phones *can* cause interference with VHF radios

I can verify from personal experience that MY cell phone does cause interference with radios. I'm a Private Pilot and I have a two year old Sony Ericsson. If I forget to turn the phone off, I can hear a cycling beep sound in my headset every time the phone is transmitting (i.e. ranging to a new cell tower or checking my email etc.) The VHF set also shows that it's receiving, so its actually picking something up through the antenna.

It's not particularly loud, and I haven't had any trouble hearing ATC over it. On a commercial jet... with several hundred cell phones, and the much higher importance of ATC calls under IFR... I can see where it could be a major problem.

Are there ways to solve the problem? Sure. Is it really worth spending the resources to test and resolve in light of the social fact