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Comment by FaceKicker | Hacker News Reader

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.

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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.

  > 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?

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.

  > 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.

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).

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).

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.

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...).

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.

The degree of engineering incompetence that would be required to make that happen is nothing short of jaw-dropping.

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?

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