5 ms·

MythBusters covered this awhile back, and busted the myth: "The final explanation is that, even though the airplanes appear to be well-shielded against cellphon

by gchucky 15y ago

MythBusters covered this awhile back, and busted the myth: "The final explanation is that, even though the airplanes appear to be well-shielded against cellphone interference, there are so many different electronics in a cockpit, as well as so many different cellphones constantly coming out, the FAA doesn't want to do the necessary testing."[1] [1] http://kwc.org/mythbusters/2006/04/episode_49_cellphones_on_plane.html http://kwc.org/mythbusters/2006/04/episode_49_cellphones_on_...

FaceKicker 15y ago
If they actually aren't willing to test whether cell phones interfere with their equipment, they shouldn't be allowing cell phones on the plane at all. Relying on people's compliance (or even just their attention) to ensure the plane doesn't explode is absurd.
- bdonlan 15y ago
  There are other options than "allow free cell phone use" and "frisk all passengers to ensure they're not smuggling in an active cell phone". Asking passengers not to use them is a decent compromise between safety and inconvenience. Naturally, if a crash were to actually occur due to mobile phone use, the FAA would need to revisit this guideline. Note that GSM phones in particular _do_ interfere with radio systems - that irritating buzz you hear when a GSM phone is near a speaker amplifier can affect airplane systems as well (although it depends on where the phone is on the plane, of course). There can also be interference with _ground_ systems - cell networks aren't designed to deal with the rapid tower transfers caused by ultra-high-altitude phones moving at Mach 0.85.
  - pyre 15y ago
    > cell networks aren't designed to deal with the rapid > tower transfers I always see this argument brought up (on HN), but what does the FAA care about cell carriers' networks? Why don't they ever use this justification when asked to justify their policy?
    - dfox 15y ago
      They don't use this justification exactly because they mostly don't care about that. It's interesting that there probably is no regulation that forbids usage of cell phones at high speeds and high altitudes (as opposed to "on board of a plane"). At least ETSI specifications seems to imply that it's perfectly legal to operate whole GSM network on board of plane, while hinting at fact that direct communication with basestation on ground from plane is not intended mode of operation and probably will not work. On the other hand there seems to be an large amount of anecdotal evidence, that it really does work, although with marginal call quality. So conclusion might be something along the lines of "it's not designed to do that", which seems like pretty good justification when you are talking about airplane safety.
      - pyre 15y ago
        > So conclusion might be something along the lines of > "it's not designed to do that", which seems like > pretty good justification when you are talking about > airplane safety. I'm not sure the reasoning follows: 1. "it's not designed to do that" refers to cell-to-ground communication, nothing to do with the safety of the plane. 2. cell-to-ground communications issues only apply to cellphones, but the FAA policy applies to all electronics.
        dfox 15y ago
        I intended the second paragraph as my though on why telecommunications related organizations don't exactly discuss whether cellphones works on board of a plane and this intention was then probably lost by inserting that paragraph break :) FAA's and related regulations are probably motivated by fact that it's essentially impossible to test that aircraft's systems work as intended even in presence of random consumer devices on board. EMC issues can be caused by almost any electronic device not only devices containing radio transmitters (eg. EU regulations require EMC certification for anything that, possibly internally, produces or uses signals >=1kHz).
  - dfox 15y ago
    That characteristic GSM interference is actually quite harmless to most well designed systems. In some sense, the GSM buzz is more caused by bad design of the audio amplifier than anything else. Also it's mostly caused by nearfield magnetic effects in contrast to RF emissions. I think it's safe to say that this is completely irrelevant to most avionics systems (but nobody is going to guarantee that).
  - brk 15y ago
    Have you ever had your phone switched on while on a plane? I have, more than once. Above about 8,000 feet it tends to be almost impossible to get a signal anyway. Most cell towers have a lot of RF engineering put into them to direct the signals DOWN, not UP.
- jser 15y ago
  Tests are performed when inflight connectivity is added to a plane -- and it has resulted in finding interference issues, such as WiFi blanking avionics screens (http://www.flightglobal.com/news/articles/wi-fi-interference-with-honeywell-avionics-prompts-boeing-354179/ http://www.flightglobal.com/news/articles/wi-fi-interference...). For cellphones, there have been many reported incidents of interference when pilots had them on (search Google). I'd assume testing on cell phones would officially commence with installs of pico cells on US airliners.
  - CamperBob 15y ago
    Tests are performed when inflight connectivity is added to a plane -- and it has resulted in finding interference issues, such as WiFi blanking avionics screens (http://www.flightglobal.com/news/articles/wi-fi-interference... http://www.flightglobal.com/news/articles/wi-fi-interference...). The degree of engineering incompetence that would be required to make that happen is nothing short of jaw-dropping.
  - pavel_lishin 15y ago
    And yet, we can use our laptops during flight. So, should I be skeptical of you, or terrified in two weeks when I fly to Dallas?
ArchD 15y ago
I thought preventing unwanted interference between devices was what FCC rules were for. Couldn't they design aircraft equipment to tolerate radio waves from devices meeting certain FCC standards?
- pyre 15y ago
  That costs money though. There's a reason that a good number of the planes in use are decades old.
  - artursapek 15y ago
    I've heard the level of cut-throat competition between airlines causes prices to be so low that it stunts the development of the industry. They are barely scraping by. Seems like a terrible business to be in.
- dfox 15y ago
  Standards for airborne electronics are actually even more stringent - FCC rules say in essence that your device may not produce interference and don't exactly care about whether you device works when exposed to interference. This is not exactly what you want in safety critical system. On the other hand, it's not about designing interference resilient system, but about testing that such system really works as intended, which would probably involve impractical number of tested combinations of devices (ie. consumer phones and whatever else). It's mostly about manufacturer's liability than anything else - it's cheaper to say "not supported and not tested".
Derbasti 15y ago
Wait, what? Don't all radio devices always get tested by the FCC before they are approved for sale? I'm sure they could test airplanes to never be influenced by, say, a sub 2 Watt signal and certify cellphones of never exceeding 2 Watts of signal power.

by gchucky 15y ago

FaceKicker 15y ago

If they actually aren't willing to test whether cell phones interfere with their equipment, they shouldn't be allowing cell phones on the plane at all. Relying on people's compliance (or even just their attention) to ensure the plane doesn't explode is absurd.

bdonlan 15y ago
There are other options than "allow free cell phone use" and "frisk all passengers to ensure they're not smuggling in an active cell phone". Asking passengers not to use them is a decent compromise between safety and inconvenience. Naturally, if a crash were to actually occur due to mobile phone use, the FAA would need to revisit this guideline. Note that GSM phones in particular _do_ interfere with radio systems - that irritating buzz you hear when a GSM phone is near a speaker amplifier can affect airplane systems as well (although it depends on where the phone is on the plane, of course). There can also be interference with _ground_ systems - cell networks aren't designed to deal with the rapid tower transfers caused by ultra-high-altitude phones moving at Mach 0.85.
- pyre 15y ago
  > cell networks aren't designed to deal with the rapid > tower transfers I always see this argument brought up (on HN), but what does the FAA care about cell carriers' networks? Why don't they ever use this justification when asked to justify their policy?
  - dfox 15y ago
    They don't use this justification exactly because they mostly don't care about that. It's interesting that there probably is no regulation that forbids usage of cell phones at high speeds and high altitudes (as opposed to "on board of a plane"). At least ETSI specifications seems to imply that it's perfectly legal to operate whole GSM network on board of plane, while hinting at fact that direct communication with basestation on ground from plane is not intended mode of operation and probably will not work. On the other hand there seems to be an large amount of anecdotal evidence, that it really does work, although with marginal call quality. So conclusion might be something along the lines of "it's not designed to do that", which seems like pretty good justification when you are talking about airplane safety.
    - pyre 15y ago
      > So conclusion might be something along the lines of > "it's not designed to do that", which seems like > pretty good justification when you are talking about > airplane safety. I'm not sure the reasoning follows: 1. "it's not designed to do that" refers to cell-to-ground communication, nothing to do with the safety of the plane. 2. cell-to-ground communications issues only apply to cellphones, but the FAA policy applies to all electronics.
      - dfox 15y ago
        I intended the second paragraph as my though on why telecommunications related organizations don't exactly discuss whether cellphones works on board of a plane and this intention was then probably lost by inserting that paragraph break :) FAA's and related regulations are probably motivated by fact that it's essentially impossible to test that aircraft's systems work as intended even in presence of random consumer devices on board. EMC issues can be caused by almost any electronic device not only devices containing radio transmitters (eg. EU regulations require EMC certification for anything that, possibly internally, produces or uses signals >=1kHz).
- dfox 15y ago
  That characteristic GSM interference is actually quite harmless to most well designed systems. In some sense, the GSM buzz is more caused by bad design of the audio amplifier than anything else. Also it's mostly caused by nearfield magnetic effects in contrast to RF emissions. I think it's safe to say that this is completely irrelevant to most avionics systems (but nobody is going to guarantee that).
- brk 15y ago
  Have you ever had your phone switched on while on a plane? I have, more than once. Above about 8,000 feet it tends to be almost impossible to get a signal anyway. Most cell towers have a lot of RF engineering put into them to direct the signals DOWN, not UP.
jser 15y ago
Tests are performed when inflight connectivity is added to a plane -- and it has resulted in finding interference issues, such as WiFi blanking avionics screens (http://www.flightglobal.com/news/articles/wi-fi-interference-with-honeywell-avionics-prompts-boeing-354179/ http://www.flightglobal.com/news/articles/wi-fi-interference...). For cellphones, there have been many reported incidents of interference when pilots had them on (search Google). I'd assume testing on cell phones would officially commence with installs of pico cells on US airliners.
- CamperBob 15y ago
  Tests are performed when inflight connectivity is added to a plane -- and it has resulted in finding interference issues, such as WiFi blanking avionics screens (http://www.flightglobal.com/news/articles/wi-fi-interference... http://www.flightglobal.com/news/articles/wi-fi-interference...). The degree of engineering incompetence that would be required to make that happen is nothing short of jaw-dropping.
- pavel_lishin 15y ago
  And yet, we can use our laptops during flight. So, should I be skeptical of you, or terrified in two weeks when I fly to Dallas?

ArchD 15y ago

I thought preventing unwanted interference between devices was what FCC rules were for. Couldn't they design aircraft equipment to tolerate radio waves from devices meeting certain FCC standards?

pyre 15y ago
That costs money though. There's a reason that a good number of the planes in use are decades old.
- artursapek 15y ago
  I've heard the level of cut-throat competition between airlines causes prices to be so low that it stunts the development of the industry. They are barely scraping by. Seems like a terrible business to be in.
dfox 15y ago
Standards for airborne electronics are actually even more stringent - FCC rules say in essence that your device may not produce interference and don't exactly care about whether you device works when exposed to interference. This is not exactly what you want in safety critical system. On the other hand, it's not about designing interference resilient system, but about testing that such system really works as intended, which would probably involve impractical number of tested combinations of devices (ie. consumer phones and whatever else). It's mostly about manufacturer's liability than anything else - it's cheaper to say "not supported and not tested".

Derbasti 15y ago

Wait, what? Don't all radio devices always get tested by the FCC before they are approved for sale? I'm sure they could test airplanes to never be influenced by, say, a sub 2 Watt signal and certify cellphones of never exceeding 2 Watts of signal power.