Episode 49: Cell Phones on a Plane

Air Date: March 15, 2006

You can fly with a life raft if you fill it with helium.

busted

The amount of helium required to lift a person off the ground (let alone the raft itself) is prohibitively immense, and such a raft of adequate size would be quite flimsy. In fact, the final test of the raft had to be aborted because of an unbalanced release of the ties, causing Adam to become entangled and destroying the raft in the process.

The ban on cell phones on aircraft is designed to force passengers to use the expensive in-flight phones.

busted

It was found that cell phone signals, specifically those in the 800-900 MHz range, did intefere 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 err on the safe side and prohibit the use of cell phones while airborne.

53 Comments

  1. jamoecw says:

    gps units receive radio signals, they don’t transmit them. it is transmiters that can potentially interfer with the instroments, that guy is just a wannabe geek, otherwise he’d know that.

    • Ed says:

      Almost all electronics emit radio signals whether they are designed that way or not. That is what electronic interference is all about. Well designed, properly functioning devices have shielding and other mechanisms to limit the interference they generate. However older and/or defective devices could easily generate interference. You are a wannabe geek, otherwise you’d know that.

      • LOL says:

        Replying to a post 4 years later? =P

        Incidentally, you’re right… All devices cause interference, but radios intentionally emit “interference”.

        That said, if the plane’s electronics is unshielded, I think you have a much bigger problem then cell phones.

        • Scott says:

          Wouldn’t terrorists be trying to “bring down” planes with their cell phones if it were the least bit possible?

  2. alexandre says:

    is possible cloning a phone cellular?

  3. Chris says:

    They didn’t do the cell phone myth justice? They should have gone up in the plane to test it. It is not illegal under part 91 in visual meteorological conditions. It needs retested.

  4. 3den says:

    how old is the aircraft the show mentioning?

    what kind of instructment are effected?

  5. Harry Stevens says:

    I work in the petro chemical business and we have been told that Cell phones will set off an explosion I was wondering if you have done any testing like this if so please send me the results. Thanks Harry

  6. da man says:

    there transmiiter was way to powerful, they should have used a proper phone.

  7. Lonny Anthony Wedell says:

    I am glad to know the cell phone myth was busted. However, would someone tell the FAA and the airline industry. Last fight I took from Washington DC to Rome they feaked out over using your cell phone.

    • Marcus says:

      Came here becaue of the news this week about celebrity using cell phone, and recalled Mythbusters had done this. So, there IS a eason not to use them… then get to Lonny’s post here- did you even READ the thing, Lonny?

  8. Chris says:

    What about Satellite Radio receivers, like the XM Helix, on which you can listen to live XM Radio on the go?

    Of course, it’s a given that you can’t listen during takeoff or landing, but still, just a thought…

  9. LT Pat says:

    Check out the website above for a quick discussion of the technical aspects of the cellphone/plane myth as well as a critical thinking exercise.

  10. Ethan says:

    I am retired now, but was formerly a corporate banking officer and flew frequently with customers on their private aircraft, both multiengined reciprocating, turboprops, and jets. On numerous occasions, the customer and others would be on their cell phones, talking at the same time long before we landed. It may be illegal and play hell with phone cells, but it is done constantly, frequently, and all the time. I have NEVER heard of or experienced any adverse effects to any of the aircraft involved.

  11. Allen says:

    I work on the electrical and avionic systems on commercial airplanes. The airplane that they tested this myth on is a late model airplane that has digital avionics with shielded data bus wiring, and I agree, should not have a problem. However, the FAA regulation is an umbrella so that analog airplanes such as the DC-9, DC-10, 737 Classics, and 747 Classics are covered. These are the airplane types that the show should have tested their signal generator on. I have been on a flight on a 737-300 where the pilot, after two PA warning announcements, stormed out of the flight deck to let the passenger see him up close and personal.

  12. Matt says:

    This really needs to be retested. This doesn’t make any sense. Not to mention, don’t cell phones have a fairly limited range. 1 to 2 miles. At altitude they can’t even get a signal.

  13. Jason says:

    The first comment left is RETARDED! GPS does not use a conventional radio signal, it uses a signal broadcasted by satellite. In the case of aircraft, 5 sats are used to track the aircraft. As for not transmitting, wrong again! A GPS unit must transmit a signal TO the sat for the sat to locate the unit. This is know as the UP/DOWN transmission process.

    Next time you choose to open your mouth (per say), think first. Thanks.

    • Splxq2000 says:

      Do you have any idea what sort of power and antenna it would take to send a signal UP from a cell phone to a GPS satellite? Check out an Iridium phone sometime.

      GPS receivers are just that- receivers. They listen- there are no transmissions (barring EMI/RFI interference etc) from a handheld device going up to the GPS satellites in order to locate your position. That’s just not how it works.

  14. Nick says:

    Jason:

    Wrong. Check your facts again. Its called a GPS Receiver for a reason, as it only receives information. Please do some research before you call someone retarded. (Try wikipedia, or google perhaps?)

  15. HEIDI says:

    I’m glad that this myth was busted. As an airline employee,I can attest to the fact that cell-phones do interfere with flight-deck/ATC comunications. The newer planes have more advanced technology and cell-phones IN AIRPLANE MODE can be used,however, in critcal phases of flight, I.E. takeoff and landing, when ATC communication is crtical, ALL electronic devices with a possible tramsmitter signal CANNOT be used. This is not a pathetic attempt to collect more revenue, contrary to popular belief.

    • Rick says:

      You know that 90% of people with a cellphone do NOT turn it off during take off and landing?

      I have regular arguments with people of both sexes and all ages about turning off their mobile phones during take off and landing. Their argument is that airplane mode is on.

  16. ryan says:

    i’m a student pilot and even i agree with Heidi that is the real reason cell phones are turned off. I used to be the guy who was annoyed to be told to turn his cell off at takeoff/landing. Now i’m the pilot whose annoyed that he cant hear ATC or flight deck comm due to cellular interferance from my passengers(friends). It will make a overpowering squeltching noise over all communications and it makes communcation with ATC next to impossible.

  17. Damo says:

    Thanks Heidi and Ryan for clearing it up. So i guess it’s not a death sentence if someone uses a cell phone but it’s still bad for the pilots and a good precaution to take. Cheers

  18. Lonnie says:

    Hello all. I have some experience with this. I have worked on many different types of aircraft. Some believe that the signal must match a certain frequency. I am here to tell you that the only thing that needs to happen is that an aircraft internal signal be ‘disturbed’. This could affect numerous signals; autopilot or navigation. Some believe that it has something to do with communications. I know that has had some affect, but it is only a confusing matter, not a direct flight effect. Look up a Saab 340 crash in the 1999-2000 range in Europe. The pilots were on course and then suddenly off course. A cell call was made shortly after take-off and then crashed. The pilots were blamed, but they, during conversations, had no idea that their instumentation was being affected and the autopilot was just following the distorded signal that was being transmitted to the computer.

    Anyhow, I wish everyone would please cut the crap about cell phone usage monopoly. I have worked for airlines and that is a hassle more than a profit. Does anyone have any idea how much it costs to approve an onboard phone system? It is very expensive. They only want to capture the installation and approval costs.

  19. Bertie the Bunyip says:

    Here’s the problem. they do interfere with aircraft radios. For starters, you can hear that charactrsitc clicking in your headset, like you do when you have the cellphone active near a TV or radio, and they tend to mess with the transponders, causing them to respond to a non-existent interrrogation from a ground station.
    Not an avionics engineer, but this is what thye tell me the prob is.

  20. Skeptic says:

    I don’t have any evidence either way, but I must admit that I find it very very very odd that the FAA would think there is a risk with cell phone use and then only “suggest” that we don’t use them on a flight.
    I can’t get on board with toothpaste and toenail clippers, yet my cell phone affects the plane navigation system and they politely ask me not to use it?????
    I’m pretty sure if there was empirical evidence, then cell phones would be clearly prohibited.

  21. Greenman says:

    I forgot to turn my phone off once & it rang in the middle of a cross country flight. Where the phone would usually display my carrier’s name or roam, it said “Emergency”. I decided not to answer it.

  22. Captbilly says:

    Jason: I am afraid that you are incorrect about your assertion that GPS units transmit to the satellite. I have been flying commercial and military aircraft for 30 years. I am also a physicist and electrical and mechanical engineer, and I have been dealing with GPS since the 1980s. The GPS units that people carry in their cars, cell phones, etc. have no capability to transmit. The receivers receive very weak signals from many satellites and calculate their position by timing how long the signal takes to arrive from each satellite. Very accurate clocks are required, and very high speed timers, to get accuracy down to as low a under a meter for unassisted GPS.

    Some very specialized GPS units used for surveying actually do transmit, however not to the satellites. These units use a known position of one or more ground station (often set up by the surveyor) to correct the errors in the GPS signal from the satellite. Even WAAS receivers use this technique, but the typical WAAS receiver is still only a receiver. The WAAS GPS system uses permanent stations that transmit an additional signal to your receiver to provide corrections to the GPS satellite signal.

    I think the bottom line here is pretty obvious; If it was actually possible for a cell phone to interfere with important comm or nav information on an airplane the FAA would not allow you to carry one on the plane. I don’t think that most people even know how to actually turn their phone off (many people think it is off when the screen is blank), and even I have forgotten to turn mine off more often than not. If this was a real problem then we would have incidents all the time, and we don’t.

    • H. Chiu says:

      Jason, if you are really a professional, I don’t think you should say such things. Fifty years ago, who knew that smoking could cause lung cancer? Even doctors smoked at that time. Many aircraft crash and accident investigations are being made based on some higher priority possible causes but it does not mean that some invisible causes could be unrelated. Why take risk or encourage people to take risk? There is no such incidents all the time does not mean nothing will happen. Once in trouble is aleady good enough to ruin everything from a person! News also reported that someone fell down from 10 storey building still survived, will you try?

    • Justathought says:

      I’m with captbilly on this, if there was even the remotest possibility of causing a potentially fatal outcome due to interference on modern planes the airlines would not allow you to carry them in flight. They would force you to check them at security, where they would be collected and put in an electronically shielded location on the plane for the duration of the flight. The answer my friends is most likely multifaceted. But the most obvious to me is control over human behavior.
      1.Like the one guy said. Nobody wants to be disturbed by the guy next to them during take off and landing expressing his nervousness over his fate to someone familiar via phone call and spreading hysteria when he would otherwise shut up next to a stranger.
      2. Sheer volume of electronic interference via radio noise from so many devices being used at once in a confined space. Not likely to bring a modern plane down but also not likely to make it any easier for the pilot running the aircraft.
      3. This policy works on everyone’s fear and turns every passenger into security for the aircraft. Everybody is nervous and looking at everybody else. Scrutinizing them. This has become more important in recent years because, and I can’t believe nobody military has mentioned this yet, but popular popular modern IEDs are remotely triggered via cellphone. A call is placed from one device to another activating it. This could only be achieved if a person can place the call successfully. (Yes they X-ray luggage but sealed batteries in laptops and other devices are a chemically based technology just like explosives and knowing what is inside one for sure via X-ray would be very difficult for the person doing the screening. This is why they ask you to pull out your laptop at security and they wipe it with that swab while they wear rubber gloves, this like litmas paper in science class is a chemical test, only for the presence of an explosive substance. They can’t check all luggage in this way because it would take far too long for all the checked baggage and so many devices use cellular radios now. Besides these are the only electronic devices you will be able to access during flight. Also it would be a serious invasion of privacy and very embarrassing to physically handle every persons belongings in line while every one else watches and waits in this manner.) But back to the point a successful call is dependent on your connection to the cell tower. And like the other gentleman pointed out an in-flight call is difficult to make and can only occur under the right conditions given your distance from the towers at cruising altitude. The only time during flight that a terrorist can reliably make this call is during take-off and landing while plane is close enough to the towers to establish a connection. The rest of the time he has no bars. Many flight staff are aware the reason for this rule and if not they are starting to catch on. This occurred to me as I was traveling alone once on a return flight from dropping off my son to his mother. A single man in his late 20s to early 30s traveling alone and handling his cellphone while the plane was taxiing. (I was checking the time and shutting it off before flight) you can guess at how I was treated. But they completely left alone the three girls 2 rows ahead of me making active cell calls all the way into take-off. This gave me the truth.
      THE ISSUE IS NOT ABOUT ELECTRONIC INTERFERENCE
      THE ISSUE IS ABOUT TERRORISM
      They just don’t want to be in your face about it and have you thinking and worrying about it during your flight. Being miles up in a metal tube that depends on so many variables to stay aloft is tense enough without worrying that the ahole next to you playing Tetris on his cellphone is really trying to kill you.

  23. Layla says:

    Don’t care. Big giant pile of don’t care. I do care about the fact that if I have to sit next to you for eleven hours on a transatlantic, I do NOT want to be subject to all of your phone conversations. Even using a headset, you still have to make those annoying mouth noises while I am quietly saying my prayers that the pressurized aluminium tube we are hurdling through the sky in doesn’t drop out of the sky. (Which I do regardless of the presence or absence of cell phones.) Your iPhone has an Airplane mode. Use it, take a break from the world. Watch a movie, and fall asleep.

    Seriously, I always attributed that rule a matter of enforced politeness. Not anything technical.

  24. kay says:

    I accidentally left my mobile on on a flight to USA and when I arrived it had no signal and wouldn’t work. It was not blocked so I think that the aircraft or satellite transmitters had actually knocked it out.It no longer works…

  25. Zack says:

    My biggest question is why do we rely on navigation technologies that can be so easily interrupted? Why not use something else that you can’t screw up with consumer electronics?

    • David says:

      Good point. We should require all navigation to be done with a sextant, pocket watch, and paper charts.

      • Adam says:

        Why do you think there’s that third and fourth seat in older planes? One was the engineer, the other was the navigator, who sat there with a map, charts, and all that good stuff.

        The electronics were devised to put everyone out of work…THEY TOOK OUR JOBS!!!

  26. Dover says:

    Bottom line… there is a risk, in most cases extremely low probability (older avionics, goofy frequency, whatever)… There are also many who either on purpose or accidentally fail to turn off their phones. By outright banning use, esp during critical phases, the probability of an incident essentially becomes near zero. Wholesale use would significantly increase the risk (esp with foreign phones with different freq/power requirements). You can’t restrict single individuals and certain types would be impractical. So the FAA ban is very broad. Everyone, just turn them off and enjoy the hour or four of freedom from that little leash!

  27. Jonathan says:

    There are two problems using cell phones aboard aircraft. One is the metal hull will inhibit signal reception – but the worse problem is that it’s not possible to establish a connection with a tower over a height of about 1000 ft. Cell towers propagate signals horizontally and downward – so it partly depends on your distance from the tower… but generally unless there’s a transmitter unit on board the aircraft (like a mobile cell tower) it’s just not possible…

  28. Ken says:

    You can indeed make cell phone calls aboard planes, for instance all those calls during 9/11. It’s not uncommon at all for cell phone calls to be placed during flight in fact. However there are challenges involved and the success of being able to place one is intermittant.

    • Justathought says:

      Those planes were flying at low enough altitudes that they could reach the cell towers, the terrorists needed easy private communication to whomever they were working with and were possibly in contact with the other planes in this way to co-ordinate their attack. It also assisted them in that they were more visible from the ground as a statement and provided an easier glide path to their targets. But the point is they were a lot closer to the ground than other aircraft at cruising altitude.

  29. Steve says:

    I am surprised that no one has mentioned harmonics as it pertains to Radio Frequency (RF). This is a big part of it.
    Have you ever been in your car and heard a strange noise like a quite buzz or click on the radio just before receiving a text message or phone call? That is interference. If you have not heard this you probably have Verizon or Sprint which used CDMA technology. I have not heard it with these phones, but I hear it all the time with my AT&T phone which used GSM and UMTS technology. Bottom line is that it is a precaution. plus if you think about over 100 phones in a plane all searching for service and transmitting…that is a lot of RF bouncing around in the plane, which increases the chance of interference. If you are interested to find out more, pick up a book on RF Theory.

    • Krystle says:

      I heard that sound before. I agree you are absolutely right. I even heard that same interference on my child’s keyboard before receiving a phone call or text on my cell phone. The keyboard has no wire connections and no am/fm radio.

  30. Brad says:

    Interesting…. So what happens to the planes when most people utilize LTE or WiMax Phones? The radios are using 700-900 MHZ Depending on the carriers.

  31. Matt says:

    Because it’s SO HARD to turn off your electronics for 10 minutes during the climb.. Good grief.

  32. DT says:

    Simple, Don’t fly if you can’t keep out of touch for a few hours. Electronic interference can be disastrous and also nuisance value of using a mobile phone when a) Fellow passengers are sleeping b) Evacuation is ordered c) PA announcements regarding safety d) Food is being served. It’s not that you are going into space forever , just a few hours. I hope they keep the ban in place. Fly safe !!!
    P.S I am not saying using mobile phones during a flight is the only risk , there may be other safety factors but mobile phone contributes in some way

  33. floyd says:

    I prefer the mobile phone ban; less noise in the airplane.

  34. Kevin says:

    Just don’t use them. No one wants to listen to a one sided conversation for hours during a plane trip. And besides the RF energy will interfere with the avionics on the plane.

  35. Tommy says:

    I flew China Southern Airline this week in China. The flight attendant told me to turn off my phone with Flight Mode while I was reading Kindle ebook App. They said the use of Flight Mode phone during flight was banned for the whole China. I mean the cruise phase, not take off and landing phase when all electronics must be off. I heard that once from other Airlines in China but I did not believe it at first and thought they misunderstood something. They cannot tell why but the rule is the rule. I guess they may have a hard time to check every phone the passenger use so they just ban it for all. That is fine as long as I have iPAD on board.

    • Justathought says:

      They may fly low enough to establish independent cellular connection there due to the volume of air traffic in that country, it’s a very busy place with a lot of people and a lot of business. More people traveling means more planes and having to keep all those planes safely away from each other they fly different altitudes to keep their distance placing some closer to cell towers than others. The point is they don’t want you placing a call on board.

  36. Biggee says:

    Of course when landing and taking off the plane is within the range of the cell towers themselves. The towers which transmit at much higher power than the the phones (even though they are more distant). Do they shut off the towers or prevent them from being built near airports? No. So why the hell should your phone be an issue?

  37. longhornhockey says:

    I bet anyone the FAA does a 180 on this matter (at least for quiet things such as email or texting) ..the MBs-episode claims the myth to be busted, but the bust is more of the “in-theory” verbiage then experimentation. Otherwise, the military would definitely have a weapon to disrupt a planes ability to function properly. I have over two decades experience in military avionics (both manned and unmanned aircraft) and suggest the rule original intention is no longer necessary.

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