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Why the FAA May Finally Relax In-Flight Device Rules
Nick Bilton at the New York Times has been writing skeptically for years about the FAA's ban on even the most benign electronic devices during takeoff and landing on commercial passenger flights. He writes in the NYT's Bits column about the gradual transformation that may (real soon now) result in slightly more sensible rules; a committee established to review some of those in-flight rules has recommended the FAA ease up, at least on devices with no plausible negative effect on navigation. From the article: "The New York Times employed EMT Labs, an independent testing facility in Mountain View, Calif., to see if a Kindle actually gave off enough electromagnetic emissions to affect a plane. The findings: An Amazon Kindle emitted less than 30 microvolts per meter when in use. That is only 0.00003 of a volt. A Boeing 747 must withstand 200 volts per square meter. That is millions of Kindles packed into each square meter of the plane. Still, the F.A.A. said “No.” ... But then something started to change: society." Of course, the rules that committees recommend aren't always the ones that prevail on the ground or in the sky.
Personal choice my ass. Cowbells can't give consent you filthy deviant.
Plus, you could catch the clapper.
rewriting history since 2109
Withstand 200V per square meter? If that's not just a typo, we are talking about a change in magnetic flow density. 30uV/m, in contrast, is an electric field strength. The electric field around any battery is much larger than that, but nobody wants to prohibit carrying batteries around. You don't get any magnetic flow from that, but you can get magnetic flow from a change in electric field change. In fact, depending on the frequency of the change, the change in magnetic flow density can get arbitrarily large even when we are talking about an amplitude of just 30uV/m.
There may well be solid technical arguments for reversing the current FAA policy, but Nick Bilton's articles certainly don't make them. Nor does the explanation attributed to the EMT Labs engineers, at least if it was described accurately. On the other hand, statements like "An Amazon Kindle emitted less than 30 microvolts per meter when in use. That is only 0.00003 of a volt" are clearly designed to make what sounds like a convincing argument to non-scientists, whether or not this argument actually has any technical merit.
As an illustration: the nominal signal strength of a GPS signal at the antenna of a receiver is specified to be -160 dBW (this is for a standard "reference" antenna, i.e. right-hand circularly polarized, under open sky conditions). That's one-ten-thousandth of one-one-millionth of one-one-millionth of a watt. In a standard 50-ohm RF system, this corresponds to a voltage of about 0.000000071, which is over four hundred times smaller (weaker) than the "only 0.00003 of a volt" signal measured off the Kindle. Viewed in that light, it's hardly clear that the Kindle's emissions are negligible. (Never mind the fact that no mention whatsoever is made of what frequency or frequencies they've measured in that setup, and that the anechoic chamber pictured in the article is typically configured to measure direct line-of-sight field strength, whereas inside an aircraft there are all sorts of complicated effects -- absorption by passengers and seats, reflection by metal surfaces, etc. So I'm not sure this is even a meaningful measurement to be making in the first place.) In any case, since GPS is considered a safety-of-life system in aircraft navigation, anything that can even come close to disrupting its ability to acquire and track signals is a potential problem.
The bottom line is that the kind of pseudo-scientific argumentation in this article isn't really helpful. As I said, there may well be sound technical reasons to relax the devices ban. But this doesn't really present any of them.
-CF
it would have happened by now. Everybody leaves them on.
I hate being bipolar; it's awesome!
"The findings: An Amazon Kindle emitted less than 30 microvolts per meter when in use. That is only 0.00003 of a volt. A Boeing 747 must withstand 200 volts per square meter. "
EMF fields are measured in V/m. He's got one side right, but the "200 volts per square meter," is nonsense. Additionally, the actual 200 V/m measure is from RTCA DO-160 Section 20, and refers to external fields, which are in large part shielded by an aircraft's metal skin. And, the criteria for success is not a lack of interference, but whether the aircraft will continue to operate after experiencing a brief event of that magnitude. Indeed, there is every expectation that normal communications will be lost when subject to that level of signal.
A better, and more honest, comparison for that 30 uV/m the Kindle put out would be to consider that a decent FM radio can get stereo reception with a signal of 2 uV/M. That's reasonable, as FM frequencies (88-108 MHz) have similar characteristics compared to those used for aircraft communications (108-137 MHz), which are immediately adjacent. RTCA DO-196 assumes a radio sensitivity of 20 uV. So, a Kindle can compete in signal strength with those normally received by an aircraft communications receiver.
This issue is not what level of emissions from a device will cause damage, but whether they can interfere with aircraft operations. Just as the author conflates uV/m with uV/m^2, he's also ignorant of what's really important.
Having said that, it's unlikely that a Kindle (the example given) emits enough in the aircraft radio band to cause problems. I'd be more concerned with a bunch of cell phones, each with a GPS receiver built in, interfering with the aircraft's GPS based systems. GPS operates at even lower levels. But, I'd trust someone who actually understands the issues to make a real study to determine the risks, rather than take the word of an obviously biased ("writing skeptically for years") writer who gets even the basics wrong, after years of writing about the subject (or is being deliberately disingenuous).
"National Security is the chief cause of national insecurity." - Celine's First Law
How foolish of me to have forgotten that epidemic of oafs bleeding out from self-inflicted pen-knife injuries in the dark decades before those seductive instruments of mayhem had yet ceased to imperil the skies.
how many pairs of boxer shorts should you own?