Saturday, April 01, 2006

Fear of Flying

I'm a skeptic when the flight attendants ask passengers to turn off their electronic devices. Years ago, I saw a reference to an IEEE Spectrum article that apparently provided the justification for the airlines' paranoia on the subject, and so I tracked down and read the article. My recollection of the article is that it contained only a hypothetical mechanism by which electronic devices inside the airplane could radiate through the skin, and resonate depending on the specific surface geometry of the airframe. In some cases, the signal might be picked up by external antennas serving the plane's navigation systems. The article (as I remember it) didn't mention any concrete cases, so I discounted it.

For many years, my practice has been to turn on my iPod (previously the CD Player) once I was settled in my seat, and not turn it off unless an attendant noticed that I had it on and directly told me to turn it off. If the pilot noticed interference, I reasoned, she could ask the passengers to turn stuff off, and I'd happily comply. (I can see why cell phones and wireless devices would be a problem, but why would a CD Player be radiating significant amounts of RF interference?) If they couldn't tell that anything was happening, I believed, it must have been all superstition on the part of the airline industry. After all, they've given us plenty of reason to believe that if they can blame the rules on someone else, they are completely unconcerned about inconveniencing us, and little reason to believe that the safety rules are updated when conditions change. (Have you noticed that they're still explaining how seat belts work? How long has it been since you could assume that 99.99% of potential passengers were familiar with seat belts?)

The Mercury News had an article a few days ago saying that there was a new study showing that Cell Phones are causing interference. As usual, there's not enough information in the article to tell what the study looked at or how significant the results were, so I googled for the new article. The authors are mostly worried about the proposals that cell phone use be allowed in flight, but they also mentioned a telling incident involving a DVD player. The most alarming fact in the article, though is that the Aviation Safety Reporting System database that used to track anonymous reports of safety problems reported by crew members or the public has discontinued some services due to budget cuts.

I'm not particularly a fan off more government reporting and regulation, but when they've crowded out private alternatives, it can be dangerous to drop the government funded programs.

Back to the errant DVD player. The new article reported:

In one telling incident, a flight crew stated that a 30-degree navigation error was immediately corrected after a passenger turned off a DVD player and that the error re-occurred when the curious crew asked the passenger to switch the player on again. Game electronics and laptops were the culprits in other reports in which the crew verified in the same way that a particular PED caused erratic navigation indications.

This was the kind of specific detail that I've been claiming for a while was missing in the previous article, and which would have been convincing. So I went back to look at the older article. This looks like the article I found back then, but it does report specific incidents quite similar to this one:

A report selected from the ASRS database illustrates this type of incident. In March 1993, a large passenger aircraft was at cruise altitude just outside the Dallas-Fort Worth International Airport when the No. 1 compass suddenly precessed IO degrees to the right. The first flight attendant was asked to check whether any passengers were operating electronic devices. She said that a passenger in seat X had just turned on his laptop computer.
The report continues: "I asked that the passenger turn off his laptop computer for a period of 10 minutes, which he did. I then slaved the No. 1 compass, and it returned to normal operation for the 10 minute period. I then asked that the passenger tum on his computer once again. The No. 1 compass immediately precessed 8 degrees to the right. The computer was then turned off for a 30-minute period during which the No. 1 compass operation was verified as normal.

Whoops. Well, nowadays, I use an iPod, and it's hard for me to imagine that they radiate as much RF as a PC or even a DVD player. But I may start turning it off for landings, which is what the experts seem most concerned about.

Here are some more excerpts from Spectrum:

All in all, we found 125 entries in the ASRS database that reported PED interference. Of these, 77 were considered highly correlated, based on the description of observed PED use and interference occurrence. The reports included cases of critical aircraft systems such as navigation and throttle settings being affected. Based on the random sample entries from 1995 to 2001, we estimate that the average number of reported interference events might be as high as 23 per year. There is considerable uncertainty about how many incidents actually occur in a year; a number of factors could make the number higher-or even lower-than the estimate of 23. Some reported incidents have not been entered into the database, and some of the reported incidents may not be interference events (that is, they might be false positives). But the data certainly suggest that PED interference events occur a few times each month.
At present, we believe that passenger use of electronics on board commercial aircraft should continue to be limited and that passengers should not be allowed to operate intentionally radiating devices such as cellphones and wireless computer equipment during critical stages of flight.
The practice of including an identifiable random sample of incidents was dropped (because of budget cuts), the ASRS can no longer be used to do statistically valid studies of all types of incidents, including those involving PED interference. Congress should provide budgetary support to reinstate the random sample entries or, better yet, to enter all the received reports.

Isn't this something the airline industry should fund privately if the government is letting the ball drop?

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