No talking on the plane

November 30, 2005 - Reading time: 5 minutes

I stay in hotels a lot these days, and most hotels that I stay at plop a free copy of USA Today at my door every morning.  So I read a lot of USA Today as well.

In today's USA Today there was an article by Kevin Maney in which he discussed the pummeling of people who carry on loud phone or VOIP conversations on airplanes.  This is something I approve of, but he also made some flippant remarks about how cell phones really aren't the safety hazards that the FAA makes them out to be.  I disagree on that, and wrote him an e-mail saying so.  Then I decided that since I haven't posted anything here in a while, I could use that e-mail to waste some more bandwidth.  So here it is:

I've just been reading your article in Wednesday's USA Today: "In-flight cell calls can't annoy fliers, but over-the-Net calls can."  I'd like to disagree with you on a peripheral comment you make in a couple of places.

I agree wholeheartedly with the main point of your article, that people yammering on cell phones in airplanes should be pummeled.  There should be a special kind of abuse reserved for people whose cell phones turn on the second the plane's wheels touch the ground, so they can make the call "Hi! Yeah, we just landed.  No, still on the plane.  Taxiing to the gate.  OK!  See you soon." I mean really ... couldn't that call wait 5 minutes? Cripe.

But that's not my issue.  You also ask "Who really believes a cellphone signal is going to scramble cockpit controls and bring down a jet?"  And later, "...Ryanair's concept says a lot about the dangers of cellphone use on planes, no?"

This is where I disagree.  I'm an electronics engineer; I worked as a contractor for the FAA dealing with navigation and landing aids for two years, and during that time I got to see what the reasons behind the FAA's rules are. 
You've probably seen a label on the back of electronic devices saying that it complies with Part 15 of the FCC Rules, and that it may not cause harmful interference.  Part 15 also stipulates that "An intentional or unintentional radiator shall be constructed in accordance with good engineering design and manufacturing practice."  Fair enough, but the fact is that with the recent boom in cheap 802.11 and other wireless devices, this is not always the case.

Ideally, your cell phone or laptop won't cause interference that would scramble cockpit controls.  However, if the device is poorly designed, or a 1-2 cent component in the RF section of the device is defective, there is no telling what sort of interference it could cause.  Aviation navigation equipment is designed to be robust and fault tolerant, but it is also high-performance equipment, very sensitive and very precise, which makes it more susceptible to interference.  There is a documented case of a 1 Megawatt mountaintop radar facility being knocked off line by a wireless 802.11b video security camera, purchased for under $50, that was over 7 miles away.  The interference was caused by a harmonic over 1GHz outside of the frequency range of 802.11b; the camera was just defective.  There are plenty of similar incidents documented, demonstrating that strict rules are justified.

Will an errant cellular phone cause an airplane to fall out of the sky?  Not likely.  But recent reductions in the minimum separation requirements for commercial air traffic can only be construed as safe if all of the RF-based navigation, collision avoidance, and location-notifying systems are operating correctly.  Once the plane is on the ground, different RF-based systems kick in to help prevent ground collisions on increasingly crowded airports.

The FAA, like other government agencies charged with protecting citizens from themselves (CDC, FDA, FCC, etc), are often hampered by public opinion: people are willing to take risks because they don't understand them, and people react violently when things they regard as convenient are taken away in the name of safety.  How do you explain the fact that when the boarding door closes and the aircraft begins to taxi, you have to turn your cell phone off, but as soon as the plane is on the ground, well before the boarding door opens, you're allowed to turn the phone back on?  Try telling the person sitting next to you that he or she has to wait another 2 minutes before turning their phone back on: then you'll be the one getting the beating.  The same goes for your laptop: you're supposed to turn off anything with an antenna, yet as soon as your laptop boots, its wireless Ethernet device is activated and starts scanning the area for access points.  Think of the $.05 worth of low-bid electronic components that are supposed to keep your laptop's emissions in check next time you fire it up mid-flight to finish an article.  Will you think twice?  Or will you dismiss safety concerns as overly cautious?  After all, you've used your laptop on the plane before, and there were no consequences.  Why should this time be any different?