If you're explaining, you're losing - JC Watt
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Your mobile device is a scapegoat for air travel scares
MOBILE PHONES' signals interfere with flight computers and can crash planes, the headlines read, and while that might seem like a great story it is nonsense.
So much so that some aircraft have, for some time now, been fitted with what are called pico cells, and in-flight phone services have been offered. Air France made such an offer on a domestic flight for a while as a trial.
Another example is the interest from airlines in wireless in-flight entertainment (IFE) systems. Cables snaking through aircraft add weight and for fuel savings weight is what you don't want. So aircraft manufacturers have been interested in building aircraft with wireless systems.
Boeing originally said that its now much delayed 787 airliner would have wireless but it has not come about. Not because wireless is dangerous but because it just didn't come up with a technical solution and that progam has had enough setbacks already.
Research in the US a few years ago found that on US domestic airlines there could be many devices switched on during flights. The researcher used a laptop, ironically enough, connected to a device that could detect mobile phone signals.
While that research warned of dangers, the industry and regulators have still gone ahead with pico cells and no new restrictions on the use of onboard devices have been introduced. This is because the earlier studies' concerns did not bear out under closer scrutiny.
Mobile phones regularly ping the cell network towers with signals when on the ground but at 38,000 feet, airliners' normal operational altitude, the handsets are too high to make the connection. It was these signals that the US researcher's device detected and what the pico cell picks up.
Yes, cautious engineers are going to qualify any statement about possible electromagnetic field interference, simply because there might be issues with future electronics, but for now there is no evidence that transmitting mobile electronic computing devices will bring down an airliner.
Otherwise why would the pico cells that are now appearing in aircraft be fitted at all? What these systems do is direct mobile phone signals up to a satellite, so the aircraft itself has to have a satellite communications, or satcom system.
Because satcom bandwidths aren't huge this means that only a handful of passengers can make calls at any one time, a good reason for why the service has not been hugely popular so far.
Yes, a crash investigation might cite a pilot's use of a mobile phone just before things went horribly wrong as a potental cause for the disaster, but it is more likely that the individual was not taking due care and attention while flying because they were texting.
Like any human being pilots do stupid things. One cause of crashes is Controlled Flight Into Terrain, CFIT, and that means that a pilot has literally flown the aircaft into the ground, or a hill or mountain.
So why do airlines tell us to switch off our devices? Because the most "dangerous" - remember here that flying is statistically safer than driving within a mile of your home - parts of a flight are take-off and landing. If you have 200 or 300 or even 400 people onboard an aircraft and you have to evacuate them quickly, you can't have people saying, "oh, just a minute I'm texting my pals" or "what was that about a fire I was just on a call?"
Anyone who has travelled in first class will know that cabin crew don't ask you to switch anything off, even during take-off or landing. The rich are going to be first off the aircraft and there are only a dozen or so of them so individuals with their toys are less of a problem. And if someone has paid £5,000 or more for a flight, airlines don't tell them what they can and can't do.
One wonders how much longer these nonsense stories will circulate about mobiles causing aircraft upsets. One guess is that as onboard satcoms get better bandwidth and pico cells can provide a better service for more passengers people will become more informed. The next generation airliners that are planned to fly circa 2020 will probably also have wireless IFE. But for now no one can rule out more silly stories. µ
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The mobile phone standards aren’t designed to cope with mobile phones doing 600mph. For example, GSM was designed to cope with the Doppler frequency shift from a phone on a TGV high speed train (186mph), and not much more. The transmissions from a phone on a plane are Doppler shifted up to three times more than from one in a train. Deliberately faking such a signal from a test transmitter on the ground would generally be considered very illegal, and anyone doing so could expect to hear directly from the FCC, OFCOM, the network operator’s lawyers, etc. You’re unlikely to be identified and caught doing so with a standard handset on a plane, but that doesn’t make it legal.
“But wait a minute”, I hear the nay-sayers cry. “Everyone knows that mobiles do work from planes”. Indeed, but the Doppler shift of a transmission is a function of the relative speed of the mobile towards the base station. The Doppler shift to a base station a long way off is high because the plane is approaching it at, say, 600mph. But the Doppler shift to a base station directly underneath is effectively zero, because the speed of the aircraft towards the base station is zero (the plane is not going straight down, we hope!).
So the transmissions from mobiles in planes are receivable by base stations underneath, but less so by base stations far away. A base station underneath the plane would see hundreds of mobiles connect to it, and then unexpectedly disappear as their transmissions pass beyond the Doppler shift specification in the radio standard (GSM, CDMA2000, etc). Then there are the effects that No,TheOtherGuy and W.- mentioned too. The network operators really, really hate that kind of thing happening. Also it would be possible for the network operators to log such activity and take legal action against you if they were ever to get really peeved.
It gets worse. Base stations antenna patterns are targeted at mobiles on the ground so as to give the maximum possible coverage. For instance, in metropolitan areas no-one’s mobile ever gets anywhere near it’s 2W maximum power output because there are so many base stations everywhere. Mobile phones outside that antenna pattern are very significantly disadvantaged, and have to transmit a lot more power in order get the base station to hear them.
So a mobile in a plane is in the wrong place and would have to transmit a lot of power in order for the base station below to hear it (never mind the fact that the fuselage is mostly metal which makes it a lot worse). Two Watts is quite a large amount of RF power. The thought of hundreds of mobile phones on a plane all transmitting at 2W is terrifying! To expand on what BB highlighted in their second post, say two hundred people were on the phone in the plane – that could be up to 400Watts of RF power. A microwave oven is 800W. Whilst a plane is much larger than a microwave (so the power density will be much lower), making the aircraft’s electronics work perfectly in the face of all that is a difficult thing to guarantee.
After a crash it would be impossible to establish that mobile phone interference had occurred and was responsible for a plane crash just by looking through the debris on the ground. So it is highly unlikely that a crash could ever be conclusively attributed to mobile phone usage. I wouldn’t be surprised if it has caused some of the numerous in flight anomalies that occur which result in only in annoyed pilots blaming crappy Boeing/Airbus software.
In order to get radio transmitters fitted to an aircraft (and I have done, so I know), you have to go through a whole pile of EMC testing and analysis in order to establish that the equipment is properly designed, built, fitted and maintained and not causing the rest of the aircraft any problems. And they are normally on the outside pointing away from the plane. Contrary to what Joe said there are tight controls over frequency allocations for radar, communications, mobiles, etc, and sticking to them is what helps all this equipment operate at the same time. Putting hundreds of cheaply made mobiles in arbitrary positions operating in un-planned ways on the inside of a plane is a recipe for disaster. Putting a pico cell in the plane isn’t too bad an idea because, as BB said, it allows pretty good control over what the mobiles are doing, making everything a lot safer. What worries me is what happens if the pico cell stops working mid flight?
@ pfromg; Yep, it can happen. Because it mostly doesn’t happen, people tend to assume that it never does, especially not to them. Ever spotted someone on a mobile in a petrol/gas station? They’re just asking for trouble. It is difficult to get the conditions just right for a mobile's radio transmission to cause problems. But if the conditions are right then the problem is guaranteed to occur.
READING COMPREHENSION. I never said phones could boost their power to unlimited levels; I said they'll be blasting out lots of transmission power because they're so far away from towers. Two (2) Watts per phone is a huge amount of power--4x the average transmit power used by a cell phone. The whole purpose of cells to prevent the need for that much power usage on mobile devices. Now factor in that you have 100 or more people using these phones at the same time in an enclosed space the size of a plane. That's more power than a cell tower puts out, with most of that energy not even exiting the plane through the port windows.
I recently had access to a Qantas manual and listed as 'group 1 - safe to use during takeoff and landing' are a GPS unit, an electric shaver, digital cameras and video cameras. I am debating using all four on my next flight to see what happens :)
I don't know if the risk exists, but the argumentation of the article is seriously flawed: One study that didn't find a danger is used to justify allowing something that may potentially endanger aircraft security. "Honest, the engines of the A380 are OK. We flew it several times without accident". That the aircraft itself may use wireless communication is not proof that any such signal is harmless. On the contrary, it introduces a vulnerability to such signals (which may be why the described development was abandoned).
This Bill Strauss character keeps coming up - the one that the FAA approved using a laptop and spectrum analyzer during takeoffs and landings because they didn't pose any threat... This guy makes his living consulting on this sort of regulation. If there isn't any risk, he doesn't make a living. Gee, you don't suppose that influences his opinion, do you?
I always held this sort of thing for rubbish. Its very much like not being allowed to use a phone in a hospital.
However, I was recently proved very wrong, twice.
My wife was in hospital , on a drip machine. I took a photo with my camera (a700) the drip machine cut out and triggered an alarm. The nurse came rushing in and I was a bit confused.I had no idea what just happened. When she left , I took another photo and the same thing happened.They swapped the drip machine.And I was quite embarrassed.later,I then made a phone call.Again,the drip machine cut out.At this point I was somewhere between excited at this revelation and knocked out that this could happen.
I also had amazing situation In a very large electronics store, where by making a phone call in the hifi enclosure caused about 50 deviced to turn off !! I have no idea what triggered that. But it happened and it was repeatable.
so people , dont be so sure if yourselves. phones and even cameras can and do cause real, unexpected and unpredictable reactions and although it may be fun being able to turn off a load of devices in a store , I would sooner not have something unpredictable happen at 30000ft.
BB was right I think, and he never said it would increase forever but obviously the phone is adapting to some degree and those things can spike.
Another thing I heard someone say on a forum in relation to the phones is that at lower altitude the phones can reach towers but since they are in the air they reach more towers at the same time than the system is designed for, so the phone companies don't like that people have the phone on when at landing altitudes since the whole setup gets confused, although I'm not sure that is true though, but who knows?
I'm sorry but this is not BS. With the amount of radar and communication equipment on a plane there is a lot of room for interference. What frequency does the aircraft radar operate? How about the different communication channels? I guarantee you there is some overlap with cellular frequencies and we're not even talking harmonics and mixing products created by normal or malfunctioning radios. There is no factual information in this article, just blubbering nonsense. I agree the chances of an actual problem are extremely small, but if you work on a plane for a living I'm sure you would appreciate any and every opportunity for failure being eliminated. Stop bitching and be glad the airlines get you where you are going safely. Also, you have no background in the subject you're writing about, reference no technical papers, yet talk like you have some sort of all encompassing knowledge. If an airline wants to implement a controlled and properly maintained wireless system on their plane they should be allowed to do so as long as it doesn't affect the safety of employees and passengers. They should not however be FORCED to allow wireless anarchy on their planes.
Wow. You complain about the standard of journalism, and fail to do the most elementary research yourself.
Mobile phones cannot arbitrarily keep boosting their output until they get a usable signal. I dont think they even work like that *in movies*.
From Wackypedia:
"The radio waves emitted by a GSM handset can have a peak power of 2 watts, and a US analogue phone had a maximum transmit power of 3.6 watts. Other digital mobile technologies, such as CDMA2000 and D-AMPS, use lower output power, typically below 1 watt. The maximum power output from a mobile phone is regulated by the mobile phone standard and by the regulatory agencies in each country."
Finding a report whereby an air crash was ascribed by the investigating authorities to the use of a mobile phone or other electronic gewgaw is, of course, left as an exercise.
Good luck with that.
This article is disinformation.
The author obviously doesn't understand how cell networks works. The weaker the signal a cell phone receives, the more power it outputs in order to be able to communicate with the far-away cell towers. If a jet is flying far away from cell towers, the cell phones will be blasting out lots of juice to reach those towers which are far away.
A picocell mitigates this problem by providing a signal source close to the phones themselves, so they don't need to output lots of power to communicate with the cell network. The jet can then communicate with the rest of the cell network in a manner that isn't as problematic as 200 passengers with separate antennas.
They prolly do it because people on a plane don't want to listen to other peoples' innane chatter. It would be like a train, except you can't get up and shift to a quiet carriage, I'd end up dropping someone's phone into their in-flight complementary drink within 10 minutes.
Games can be played through headphones but to make a phonecall you have to talk, and people invariably talk louder on the phone than they would to their family/ friends in the seat next to them,
No, that doesnt make any sense either.
Jets typically fly at ~30,000 feet, which is ~6 miles, or 10km. Why do phones on the ground not kill mobile towers up to 10km away? Why are phones not banned from (for example) the top of a skyscraper, for the exact same reason?
The whole thing is - and always was - BS, and the article is absolutely right to call it as such.
The (claimed) reason for not allowing cell phones on planes [in the US, at least] is not an FAA directive, it's an FCC directive. It's not that a phone is going to bring down a plane, it's that a cell phone at 10Km can see a very large number of cell towers, and can interfere with spectrum re-use across a wide area. This causes problems with cell phone coverage on the ground.
So phones on planes may crash things, but it's far more likely to be an AT&T tower than a Boeing jet.
If a mobile phone could bring down an airliner, then why would terrorists screw around with risky, easily-detectable explosives and complex, multi-person conspiracies? All theyd need is one jihadi with a Nokia.
Likewise, if these things really were so dangerous, then they wouldnt be allowed anywhere near a plane. I cant take on board 100 ml of bottled mineral water, but I can take on my instant-override-all-systems-boom phone? Yeah, right.
So the question is: what is the *real* reason why personal electronic gadgets are not allowed to be used on planes (or in hospitals etc)?
Could it, perhaps, be something to do with having a captive audience for hugely expensive in-house offerings?
No! Surely not!