"Laser-operated devices are prohibited on this flight"

I was recently flying back from Dublin, and was most vexed to learn that CD & DVD players are prohibited on their flights. I know the rationale behind why radios & cell phones aren’t allowed, but why CD players? If they’re unsafe, then why aren’t they banned on domestic U.S. flights? And why are laptops allowed when most of them contain internal CD or DVD players?

Travelling with Aer Lingus ?


I’d like to know why also !

It’s an electronic device with substantial amounts of digital logic. That means that unless properly designed and shielded, which is extremely unlikely for a consumer electronics device, it will radiate large amounts of RF noise. This can interfere with the plane’s navigation and communications systems.

You can test this for yourself. Get an old portable AM radio. Turn it on and tune it to a space in between stations, and set it next to a portable CD player or other device.

I’m coming to this discussion late, but have there been documented instances of navigational systems being disrupted by personal electronics gear in-flight, or has it all been in the lab, or is it all just SWAG?

Er, nitpick coming:
Notice the CD/DVD player is categorized together with AM/FM radios and DAT/Minidisc players. So it may not even be a “laser” issue (yet another category is SEGA/Gameboy type personal game systems). As mentioned, the concern generally is about the devices containing unshielded processors and oscillators, and in late-model aircraft it’s not so much about interference with the actual flight management system as with mucking up communications with ground and with the Nav beacons.

Anyway, these are not statutes, they are rules that each airline adopts as they see fit. Barring an actual law or FAA (in the USA) or ICAO regulation, Aer Lingus can have a different set of restrictions than, say, JAL or Continental, for no better reason than being just paranoid about RFI, nevermind the evidence. In many cases, what you will have is a whole category of product flat-out banned because someone in the airline nay hear that some specific article in a related category may cause interference (or may have back in 1987 when the technology was first introduced, or may if made in the North Gobsmackistan plant, or may if the airplane is equipped with the Begorratronics CM76A Mk. V transponder, or whatever ) and he’s not about to either take any chances, or expend any effort to prove or disprove, or make the gate agent check it out.

This issue has come up before.

A point that doesn’t get enough attention is that announcing a ban on a certain type of device is not sufficient to prevent the use of such devices. Probably 95% of passengers will voluntarily comply, but some will remain ignorant a few will simply ignore the rule.

So if a CD player or a Gameboy can actually cause a problem for an aircraft, you’re going to have to do much more than announce a ban - you’ll need to inspect carry-on items, and reliably identify and confiscate problem devices. Doing this thoroughly will be difficult and expensive.

A far more reliable approach will be to take normal radiation from consumer electronic devices into account when designing, testing and certfying avionics.

While some people dismiss it as anecdotal, there are numerous reports of passenger electronics items, including CD players, interfering with aircraft systems in NASA’s Aviation Safety Reporting System database.

“Large” amounts of RF noise is probably overstating things. The FCC does regulate small appliances to limit RF noise, and any navigational instruments likely to be affected are many feet away behind a metal bulkhead. I guess I’m in the camp that says if the airplane instrumentation isn’t robust enough to handle small amounts of RF interference, then it should be redesigned or shielded.

Another possible reason is to ease enforcement for items which really are an issue. Suppose, for instance, it were found that an AM/FM radio caused dangerous levels of interference (plausible, since any antenna that can receive can also transmit). OK, so the airline bans radios. Now, the flight attendent notices someone on the plane wearing headphones leading down to a little box at his side. Is that OK, or not? The attendant will have a hard time telling. Maybe it’s a harmless CD player or iPod, or maybe it’s a dangerous radio. Easier to just ban all little boxes with headphones.

They might also be concerned about bombs, weapons, or other terrorist devices (perhaps something designed to interfere with nav systems?) being disguised as a standard personal appliance.

There’s an article about this in the current issue of Air & Space magazine. Unfortunately it’s not available on the website. Fortunately, all it takes is a trip to Barnes and Noble to find the issue in question. It gives a pretty good explanation. It boils down to interference with radio communications and navigation equipment. CD players, portable TV’s and cellphones seem to be the worst culprits.

I flew from Dublin to London last saturday with Aer Lingus. I was listening to some MP3s on my Palm PDA and the stewardess asked me if was an MP3 player. I thought she just curious and grunted a no at her (I say grunted because it was 6.30 in the morning and I hadnt quite woken up) and she walked away. I thought it was a bit strange at the time but now i know why.

Will you take my personal statement as evidence?

I have, on a few occassions, noted intereference in the airplane radio/nav system from a “personal electronic device” (usually a cellphone someone forgot to turn off). It’s not consistant. It’s also coming from a PED about 2 feet away from the control panel in a small plane as opposed to being 50 feet back from the cockpit in a 747.

So, yes, a PED could affect the equipment. And, as pointed out, there are numerous reports in the ASRS database. Some of them come from the big airplanes. Read one once where the pilots were having problems with some of their computers upfront and wound up having someone do a walk through the cabin. Found one guy with a running laptop. Asked him to turn it off. End of problem. Problem came back. Went back to Mr. Laptop - sure enough, he’d turned it back on. Laptop was turned off and removed from his hands for the rest of the flight. Seems his particular one was particularly “noisy”. Maybe the shielding had been damaged or something, I don’t know.

Now, this interference, in the instances I’ve seen, isn’t horrible - you can still talk and understand over the radio, for example. But avionics already have to cope with enough crap, including things like sunspots, which also cause interference, and nearby storms, and Og knows what else, which also cause interference and pops and squeals and stuff - why add to the problem? To top it off, when using sensitive navigational equipment to navigate in clouds, or night (or both) when you can’t see you really don’t want any more intereference than necessary.

99.99% of the time it won’t make a difference… but maybe your flight is in the remaining .01% where it does.

Yeah, that’s a great idea - except consumer electronics change faster than avionics do. What with the required testing and everything, by the time you design, test, and certify avionics to cope with the PED’s of one year, the PED’s have all changed (probably several times).

Also, given the cost of avionics it’s just not economically feasible to junk these systems every 6-18 months and buy all new - unlike consumer electronics, where that’s sort of expected.

Then there’s the problem that the whole point of com and nav antennas is to receive signals - if you shield them too much they become useless.