Ok … count me skeptical, but I refuse to believe that the little 3 volt battery in my cell phone generates enough of a signal to interfere with the jumbo jet I am flying on. Ditto with CD players, Gameboys, etc. all of which they prohibit you from using on your flight. I don’t see airplanes detouring to avoid the radio signal of MUCH more powerful communication towers (TV, Radio, Cell Phone towers) or powerlines. I think even given proximity, these produce a much greater likelihood of interfering with the airplane. I have read that there is no evidence that cell phones and the like do interfere with airplane electronics/avionics. So what gives with the FAA prohibiting these devices? Are the in cohoots with the people who make the 5 dollar a minute phones on the seatbacks? And how is it you can use THOSE phones but not your cell?
Actually it would be pretty easy to generate enough interference to screw up the radios on an airplane with a cellphone battery, if you designed a custom jamming transmitter.
Personally, I think the odds of a cell phone causing interference on a plane is extremely small, but still larger than a cell phone causing a gas explosion at a gas station, and probably larger than a cell phone causing problems in a hospital. In either interference case (plane or hospital), the most likely scenario is the phone in very close proximity to a sensitive piece of equipment. For example, you’ve got a window seat near the wing, and the cable connecting the antenna on the wing to the radio in the cockpit happens to run in the panel right next to your head, and your phone is right next to that, etc., etc.
The reason you can’t use cell phones on planes is because the phone and cell towers aren’t designed for it. On the ground, the phone is normally in range with only one or two towers, and everybody figures out who gets control. As you move from cell to cell, you’re handed off from one tower to another automatically. When you’re in the air, your cell phone can probably reach 20 or 30 towers, plus when you’re zipping along at 400 mph you’re moving between cells too fast. The cell system isn’t designed for these conditions.
The plane seatback phones are designed for this sort of thing.
Arjuna34
Computers can cause navigation malfunctions. The IEEE Spectrum reported an incident where it was determined that a passenger’s computer was interfering with navigation. They asked him to turn it off, and he complied. A little while later the interference happened again. Someone in the crew went back, found the man using the computer again, and told him to turn it off. A little while later, on final approach, the same thing happened. The Captain went back and took the computer away. The man was arrested when they landed.
The reason they ban all electronics is to prevent attendants from having to judge whether a device is OK or not. It is easier to ban everything.
As far as the power from your battery goes, try running a wire from one terminal to the other and see how warm your battery gets. If you can feel it getting warm, that is several watts of power, more than enough to screw up a sensitive receiver. To make it worse, these are usually pulsed waveforms which splatter frequencies all over the place.
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Even if Cell Phones arent designed for those conditions, they would work. In many cases your phone can reach multiple tower/recievers and it finds the strongest signal and makes use of it. Consider large cities for instance. And again, this has nothing to do with other electronic devices which are prohibited as well.
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If it were easy to create a 3volt jamming device, then no electronic device would be allowed on airplanes. You could make a jamming device to look like a gameboy or cd player and use it in flight, etc. Even asking you to shut such devices off is no guarantee, as you can just stuff it in your pocket, running, and no one would know. As terrorists everywhere arent bringing down airline communications, I don’t believe this is the easy task you are off-handedly saying it is.
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Most of an airplanes critical navigation and communication equipment is in the front of the plane, well away from any passengers. Again, considering signal strength and proximity, it would appear that communications towers are a more viable threat than phones or other electronic devices.
There must be someone with better information than this out there?
As I mentioned on a previous post, Last year a small commuter jet crashed just after take-off from an airfield in Switzerland. the initial accident investigation has concluded that the most likely cause of the crash was that one of the passengers was using a cell-phone and had interfered with the flight electronics.
Every flight I’ve been on has allowed me to use my CD player and my Gameboy during most of the flight. It was only during the take off and the landing that they ask for them to be turned off.
I think the risk of a disasterous problem with a cell phone, regardless of how small, just isn’t worth the risk. Nobody really needs to use their cell phone during a flight.
Here’s a lengthy article on portable electronic devices on airplanes –
http://md-l.amulation.com/archive/199708/msg00020.html
One minor note - the prohibition is not just a precaution against radiated EMI, it’s also because such devices are a distraction in safety announcements (all the plane-provided services can be interrupted).
Your point #2 – the reason people aren’t making jamming devices and bringing them on the plane is that there’s no guarantee that they can damage the plane (and if they did want to do it, they could bring more power than a 3V cell battery provides). All they can do is interfere with instruments, but probably not all the instruments. They almost certainly can’t mess with the controls (electronic controls are very heavily shielded). All pilots should be able to make a landing in the event of instrument failure. Such a terrorist doesn’t really have any leverage, only the ability to be a nuisance.
As to your third point in the second post :
Not only is there sensitive equipment on the wings, but the noise can be potentially transmitted from various spots on the plane through the airframe. Although the problems of interference are largely irreproducible, making it difficult to figure out exactly how it happened, there’s still strong evidence that it happened. See the examples given in other posts.
As to other surrounding signals that’s why we have the FCC divvying up the electromagnetic spectrum. Radio, TV, etc. towers don’t interfere with each other because they’re strictly regulated. The noise from a portable electronic device, on the other hand, is not so closely controlled. Well, it is, sort of – I’m not denying there’s some controversy about this matter and what the regulations should be. In fact, devices do have some standard as to the amount of noise they produce. Airlines would like to have as little likelihood of failure as possible, and so request higher standards.
By noise above I’m referring to whatever is radiated by the device, especially at an interference frequency, even if it’s not necessarily noise from an engineering viewpoint. In a cellphone, this means that the stuff that comes out of its power supply can be more of a factor than the phone signal (which is, of course, in a spectrum regulated by the FCC).
Indeed chances are VERY slim for an electronic device to interfere with the communication/navigation systems of modern airplanes, since these are tested and re-tested, and designed in such a way that the probabilities of malfunction are extremely low.
You will hear many stories about airplanes loosing control, and computers interfering with the aircraft’s systems, but, so far it hasn’t been conclusively proven that this has happened. Not a single accident investigation authority has yet claimed to be a 100% certain that a PED (portable electronic device) is responsible for any aviation accident.
However… it is always better to play safe until we know for sure that our safety is not threatened by these devices.
Now, regarding cellular phones, here’s a bit of info, contained in the FAA’s Advisory Circular 91.21-1:
However, as I said before, we like to play on the safe side. Would it be too much to ask our passengers to refrain from using certain devices for a limited time and read a book, or talk to the next-seat passenger, or take a nap, and restrain themselves for a short time from the pleasures and wonders of playing with their technologically hyper-advanced toys?
Regulations have already been changing, and now you CAN use devices that were previously forbidden. I’m pretty sure that in a not very long time we will be allowed to use almost any kind of SAFE device. But we have to run some tests before we can get there. I don’t want to see technology screwing my life just because we were impatient. Remember DDT, and CFC’s? We started using them before we knew the consecuences, and see the results. Let’s wait and be patient.
Saludos.
I agree with Alphagene.
Now, the accident mentioned by David Cronan involved a Saab SF340 of Crossair. So far the official report goes like this: “The aircraft crashed shortly after takeoff from ZUR. Cause unknown.”
CAUSE UNKNOWN.
Newspapers and TV shows are not qualyfied (I’m guessing here that that’s where that info was obtained) as Accident Investigation Agencies.
And also, “intial accident investigation(s)” do NOT conclude.
I wonder how the investigators found out that someone onboard was using a cell phone (maybe the person on the other side of the line -if any- testified to the effect, granted), and if that was the case, HOW did they “concluded” that this was the cause of the accident. So far I haven’t been able to find any information that points to any culprit. But, as has proven many a time in the past, I could very well be wrong.
Have a link for me?
Thanks.
Saludos.
Have you actually tried this? I’ve never got a cell phone to operate long after takeoff- if a call is in progress on the ground, it’s dropped quickly after takeoff. I have gotten a wireless Palm VII to work (once) at 20,000 feet, though 
All this fun was done on our corporate, private jet, not a commerical flight.
There’s a big difference between a cell phone seeing 4 towers in a city, moving at 70 mph, and seeing 20-50 moving at 400 mph. The negotiations among towers and the phone (especially between different carriers on the edges of their territories) takes a little time, and at 400 mph ground speed you’d be zooming by cells every second or two!
Cell tower radiation patterns are carefully plotted to avoid big overlaps on the ground. Another reason in-flight cellphone usage isn’t too successful is that these radiation patterns are directly mostly at the ground, not up in the air. Radiating RF up would be a waste of power for a cell tower, given that the network can’t handle airborne phones anyway.
That said, I’ve heard of a system for airline use that is supposed to take advantage of existing cell tower infrastructure, but I don’t know any details about it (a FOAF story …)
Again, it is very easy to design a 3V device to interfere with airline navigation equipment. Heck, you can buy handheld transceivers that run on AA or AAA batteries that transmit on airline frequencies- no design required! If you want, though, just build a crystal oscillator tuned to one of the nav frequencies of your local airport. You can get several watts out of a couple of AAA batteries for at least 30 minutes. Total cost could be under $10, and could probably be stuffed inside a working Gameboy.
Note that I didn’t say you’d be “bringing down airline communications”, just that you’d interfere. At worst, they’d probably switch frequencies. Commercial airlines have multiple radios working on multiple frequencies, along with GPS, LORAN, etc. - it would take a significant effort to block everything. On top of that, they can still land the plane without radios.
Yes, the receivers are up front, but the antennas aren’t- many are on the wings, or under the plane. Coax cable connects the antennas to the radios up front, and this cable could be routed relatively close to passengers (I actually don’t know much about how it’s routed). Of course, this should be shielded coax, but if your transmitter is very close you can still radiate into it. In any case, passengers near a antenna (for example, window seats at the wings) are in a good position to intefere, if they have some radiating device (not that they would intefere, just that they’re in a good position to).
Arjuna34
Quote: (Arjuna34)
quote:
Originally posted by Gone The Sun
- Even if Cell Phones arent designed for those conditions, they would work. In many cases your phone can reach multiple tower/recievers and it finds the strongest signal and makes use of it. Consider large cities for instance.
(Arjuna’s reply)
Have you actually tried this? I’ve never got a cell phone to operate long after takeoff- if a call is in progress on the ground, it’s dropped quickly after takeoff. I have gotten a wireless Palm VII to work (once) at 20,000 feet, though All this fun was done on our corporate, private jet, not a commerical flight.
Just because it’s a “private jet” doesn’t make this OK, Arjuna - the FCC regulation applies to all aircraft. And it is an FCC regulation that forbids cellphones (with a few, very expensive exceptions). The Federal Aviation Regluations (FARs) state that electronic devices can be operated if the pilot in command determines it is safe. (If folks really want to know the reg I can look this up and quote it verbatim). On the airlines, rather than ask a couple hundred passengers “can I see your gameboy, please - I want to see if turning it on screws up the
instruments” they just tell everyone to turn everything off for take off and landing.
quote: (Arjuna again)
Note that I didn’t say you’d be “bringing down airline communications”, just that you’d interfere. At worst, they’d probably switch frequencies. Commercial airlines have multiple radios working on multiple frequencies, along with GPS, LORAN, etc. - it would take a significant effort to block everything. On top of that, they can still land the plane without radios.
Well, it’s like this - commercial airlines fly on intrument (IFR) flight plans. When flying IFR a plane is assigned a frequency and is not allowed to change it without permission. If the signal is jammed, they can’t ask permission. Of course, if there’s an emergency that’s different but the way the system is set up you can’t just decide “I don’t like 123.60, I’m going to switch to 119.25”
Also, some of the “mulitple frequences” are not voice frequencies - they’re nav frequencies. Sure you can broadcast on them, but no one will be listening on the other end. And, oh yeah, that might screw up the nav signal for someone else.
Yes, you most certainly can land an airplane without radios - but the system designed to accomodate a plane with no working radio can’t possibly handle the normal volume of traffic at, say, Atlanta Hartsfield, Dallas, Los Angeles, or Chicago O’Hare. This will cause serious delays for everyone else. Actually, in such a circumstance they would probably divert the plane to a less busy airport, thereby seriously inconveniencing the yuppie businessdweeb who wouldn’t hang up the cellphone/turn off the laptop/whatever and everyone else on the plane.
So while the use of an “electronic device” is not likely to cause a crash it certainly has the potential to be a real pain in the ass for everyone involved.
quote:
quote:
- Most of an airplanes critical navigation and communication equipment is in the front of the plane, well away from any passengers. Again, considering signal strength and proximity, it would appear that communications towers are a more viable threat than phones or other electronic devices.
Yes, the receivers are up front, but the antennas aren’t- many are on the wings, or under the plane. Coax cable connects the antennas to the radios up front, and this cable could be routed relatively close to passengers (I actually don’t know much about how it’s routed). Of course, this should be shielded coax, but if your transmitter is very close you can still radiate into it. In any case, passengers near a antenna (for example, window seats at the wings) are in a good position to intefere, if they have some radiating device (not that they would intefere, just that they’re in a good position to).
Aircraft wiring is routed between the outer skin of the plane and the inner wall of the passenger/cargo/cockpit areas. So a fair bit of it is on the other side of a bulkhead a snoozing passenger is leaning against.
Antennas aren’t mounted on the wings, by the way - any antennae-like objects are actually something else. (Radar units are sometimes mounted on wings, but they aren’t antenna-shaped) Antennas are stuck on the fuselage where convenient, which may be near the cockpit, on top, on the botton, on the vertical stabilizer…
The problem with antennas is that they need to be sensitive enough to pick up signals… meaning they will also pick up interference. If you happen to be seated near one you could cause problems even if on another flight you didin’t.
As for shielding - shielding can become damaged or worn, causing problems where they weren’t before.
To stroll farther out into the weeds, the FAR is 91.21 and specifically targets air carriers and aircraft under IFR flight plans and exempts voice recorders, electric shavers, pacemakers, hearing aids, and anything else the Pilot deems safe.
The bottom line is that you never know what may mess with the nav or comm equipment… if I want to jam your favorite FM station, all I need to do is find a transmitter that broadcasts on that freq and will overpower it when I sit it down next to your radio (receiver). Having a TACAN or GPS freq messed with while in flight is serious, although with multiple navigation sources, any interference will manifest itself as a split, or drift, in whichever source is affected and should be noticed by the computer or crew. Of course, you don’t want it happening to begin with. It’s the voice comms that are the most dangerous, IMHO, because you don’t want to be missing that one ATC call telling you to check for traffic near you or to climb or dive in order to avoid it.