"... and please switch off all electronic devices."

[kovidgoyal]

I don't see how you could shield an antenna against passenger generated signals but still have it receptive to GPS signals, other than by putting a lot of distance between the antenna and the passenger cabin.

Wiring should definitely be shielded, but I'd have assumed it is already.

[Jellby]

But some phones have GPS receivers, so just being close does not seem a real problem.

[kovidgoyal]

Originally Posted by Jellby

But some phones have GPS receivers, so just being close does not seem a real problem.

A good point, I wonder why cell phones don't affect their own GPS receivers, or for that matter GPS receivers in car navigation systems.

[Elfwreck]

EL AL Flight Mid December 2005 Landing in Tel Aviv:

As the EL AL plane touched down at Ben Gurion Airport the voice of the captain came on: “Please remain seated with your seat belts fastened until the plane has come to a complete stop and the seat belt signs have been turned off. We also wish to remind you that using cell phones is strictly prohibited.”

Pause

He continues: “To those of you who are seated we wish you a Merry Christmas and hope you enjoy your stay…and to those of you standing the aisles and talking on your cell phones we wish you a Happy Hanukah and welcome home.”

[pricecw]

Originally Posted by kovidgoyal

A good point, I wonder why cell phones don't affect their own GPS receivers, or for that matter GPS receivers in car navigation systems.

They might, not really a big deal though, if you look at a track of most GPSs you can buy, you will see points where there is a straight line jump from one position to the next, generally this is an area where the GPS isn't tracking, and doesn't get a point or so. Not a big deal on your cell phone, car navigation, hiking, etc, and generally within the specs for a consumer GPS, take the Magellan Maestro 4700, it's specs for resolution "GPS Accuracy 3-5 meters", which is much better than used to be available with SA enabled.

Also, the most a car or cell phone is good for is as a navigational aid, not as vehicle control, get a glitch, lost signal, etc, no big deal.

Now, wrt trying to harden a plane to consumer devices, it is almost an impossible task. You would have to get every conceivable device, and test those in all combinations with all combinations of planes to prove there can't be a problem (probably add in the mix every possible location in the plane for each device on each plane). Everytime a product is introduced or update, or a new plane is introduced, or something is changed on a plane, you would need to re-do these. Worst scenario is a new consumer device introduced or a device changed, since all combinations would need to be tried. All devices would need to be tested until the last one fell out of use.

That would be the only way to prove your device can't cause problems.

The other issue, planes should be designed for this type of thing. I agree, they should be, but currently they aren't, and the fleet is very unlikely to undergo an immediate upgrade to fully shielded vehicles. Devices should also be designed to emit only those radiations meant to be emitted (ie on an e-reader, light and the specific radio waves when 3G or WiFi is on), but they won't, manufacturers will do the least required by law to save money.

I have seen a lot of things on circuit boards that become antenna to a number of different frequencies (do you know how many different frequencies your e-reader is emitting), and to control those to the point of no chance of a problem is a daunting task, and an expensive one, are you willing to pay 25% or more the cost of a device so you might be able to use it during take off and landings of an airplane? Is everyone willing to bear that cost?

--Carl

[wodin]

Originally Posted by DJHARKAVY

According to Mythbusters, handheld electronics, including cell phones, do not affect the instrumentation in the least.

Think about it... Do you really think that the airplane navigation systems will be affected by the small power output of even a hundred cell phones?

Do you really want to trust the lives of several hundred passengers and crew of an airliner to Adam and Jamie?

[wodin]

Originally Posted by HarryT

Your mobile phone, on its own, would certainly not cause any problem. 400 of them, all transmitting at maximum power, might, however, very well do so. Hence the regulation.

Like when the plane is in the approach pattern and everyone is calling their spouse for a ride home?

[kovidgoyal]

@pricew: Actually, you don't have to shield planes from all devices or even test each plane with every device. What you need is to establish a set of standards about the electromagnetic radiation permissible from electronic devices. In the US, the FCC already does this. The problem is that the FCC standards are incompatible with similar (though more rigorous) standards setup by the FAA.

Basically, what's really needed is for the FCC and FAA to co-operate.

And you really don't need to worry about random circuit boards becoming antennae. It's very simple to shield circuitry from EM radiation. Just put it behind metal. The problem is antennae, which cannot be put behind metal for the obvious reason that they need to receive EM radiation to work.

And if I understand the problem, as described in the reports with the GPS systems correctly, the problem isn't that a cell phone signal can cause a momentary loss in GPS tracking. This would be harmless, since software can easily compensate for it. The problem is that the cell phone signals have been shown to actually cause the GPS system to lose satellite lock, which then takes a significant amount of time to re-establish. I've never seen that happen with car/hand held GPS systems.

And finally, you don't need to upgrade the whole fleet all at once. You need to upgrade it a few planes at a time and remove the restrictions only on the upgraded planes.

@HarryT: Actually if you read the reports TimS linked to, even a single cell phone can cause problems. Undoubtedly more phones will make it more likely that a problem occurs.

[DawnFalcon]

Originally Posted by pricecw

Now, wrt trying to harden a plane to consumer devices, it is almost an impossible task. You would have to get every conceivable device, and test those in all combinations with all combinations of planes to prove there can't be a problem

Or you can take the sensible approach, mandate a regular shielding test on aircraft, and make sure that the customer electronics requirements mean that they can't breach the shield. And ban, very publically, offending devices.

And once more, the problem of cell phones can be solved by an onboard cell which simply blocks calls during critical flight phases.

[Sweetpea]

Originally Posted by DawnFalcon

And once more, the problem of cell phones can be solved by an onboard cell which simply blocks calls during critical flight phases.

But it's not only phones that have to be shut off. I was asked to turn of my digital camera! How would you block that?

[lene1949]

Last time I went to Denmark, I had no idea, how to turn my mobile off... I'd only just got it.

I'm wondering, if the switch on/off could interfer, but the permanent off/on would be OK??

Anyway.. I always turn off my phone.. ipod.. kindle, when I'm asked.

[jbjb]

Originally Posted by kovidgoyal

@pricew: Actually, you don't have to shield planes from all devices or even test each plane with every device. What you need is to establish a set of standards about the electromagnetic radiation permissible from electronic devices. In the US, the FCC already does this. The problem is that the FCC standards are incompatible with similar (though more rigorous) standards setup by the FAA.

One problem with this is that FCC testing is far from perfect. For example, emissions from electronic equipment are very dependent on what that equipment is doing at the time. For example, the radiation from a laptop, or electronic reader, or anything that involves a processor executing code (which is pretty much everything these days), depends on the software being run. Manufacturers tend not to repeat EMC tests on their kit every time they release a new version of firmware. (Perhaps that's paranoid, but over-caution seems a sensible starting point where planes are concerned).

And you really don't need to worry about random circuit boards becoming antennae. It's very simple to shield circuitry from EM radiation. Just put it behind metal.

The trouble is, any useful piece of equipment needs to interact with its surroundings - it needs inputs and outputs. These necessitate holes in any metal shield. If you look at the radiated emissions from typical equipment, most of it will be leaking out through network connections, keyboard cables, mains power connections etc. The same is true of sensitivity to EMI - each of these interfaces allows an entry point for incoming emissions.

/JB

[jbjb]

Originally Posted by DawnFalcon

And once more, the problem of cell phones can be solved by an onboard cell which simply blocks calls during critical flight phases.

Cellphones don't only radiate when on a call. I agree that a local picocell which blocks calls will dramatically reduce the emissions, but it won't eliminate them.

/JB

[DawnFalcon]

No, but you realise that it takes the levels below that which you get from simply flying over a city on approach or takeoff, which is far from uncommon. I'm not kidding about testing aircraft on a regular basis or how infrequently shielding is checked or replaced currently.

[jbjb]

Originally Posted by DawnFalcon

No, but you realise that it takes the levels below that which you get from simply flying over a city on approach or takeoff, which is far from uncommon.

That's over-generalised. How far away from a single phone do you think you have to get before the field strength it generates is less than the background from a city beneath the plane?

My cellphone, even when not on a call, frequently causes audible interference with nearby thinks that have speakers, such as my PC or my desk phone. The cellphones in the rest of the city don't seem to have as significant effect.

/JB