CD Players and Electronics on Planes

Factual Questions
1

There is an article in the archives, “Why aren’t you supposed to use a radio receiver on an airliner?” (http://www.straightdope.com/classics/a2_355.html) which brought up some similar questions that have always puzzled me:

Question 1:

Sure, I can understand that Radios and Mobile Phones send out and receive signals, but what is wrong with CD Players and Minidisc Players that causes certain airlines to ban their use? It says so in the pre-flight videos, the card in the seat pocket, and I’ve been told by staff to turn a CD Player off. I’ve asked a few staff members, but nobody has known why. Here are a few facts I’ve organized to help you in solving my mystery:

1: The airlines that I have found practising it are Swissair and Thai Air. The other airlines I have flown on since becoming aware of this, British Airways and Easyjet don’t.

2: It’s CD Players and Minidisc Players. Tape Players, DAT Players, MP3 Players, etc, are ignored. Therefore, they’re not trying to force you into listening to the ‘radio’ on the plane. I presume that portable DVD players will be banned once they get popular enough.

3: Hard drives, another device that works in a similar fashion are not banned. However, CD Players on laptops are forbidden.

4: I have never even seen a portable CD Player with a radio built in, and Tape Players are allowed, which commonly have this feature.

Perhaps Swissair banning it has something to do with the crash they had recently, which I think might have been blamed on the ‘in-flight entertainment system’ at one point. Could someone please try and answer this! Is there something simple I’ve overlooked? Thanks.

Question 2:

When planes take off and land, it is common practise with pretty much every airline to tell everyone to switch off electronic devices. Some even go as far as making you switch them off in turbulence too. Reluctantly, I switch off whatever electronic device I was enjoying and pull a book, or the flight magazine. Once again, I have found no explanation for this. Everyone must be turned off - no exceptions. However, there are hundreds of watch batteries and data back-up batteries that remain on, and god knows what else. Why is it that they make you do this? It’s hardly like you’re stealing power from the plane. Or does it create a electronic field of bad karma, or something equally complicated? Answers will be greatly appreciated. I want to know why I have to resort back to… ugh… non-digital entertainment :wink:

Thanks.

2

you might want to try out this article. It’s long, but pretty comprehensive. The general conclusion is that while there is no hard evidence of interference, the jury is undecided. Better safe than sorry I guess

3

The reason receivers are banned is that the old style of radios have tuners that emit radio interference on harmonics of the station you’re tuned to. Modern radios don’t have this problem, but the flight attendants can’t go around making sure everyone has a modern radio, so they are all banned. I don’t know about the mixed devices and bans, that sounds like a stupid interpretation of flight rules, they’re just banning them on a whim.
The reason why you can’t use electronics during takeoff, landing, or turbulence has nothing to do with radio interference. You might have noticed that they asked you to securely stow your device, not just turn it off. Flight rules require your carryon devices to be stowed during takeoff and landing. Now you wouldn’t want to survive a plane crash, just to be killed by someone’s laptop computer flying around the cabin, would you?