Does electronic equipment actually interfere with aircraft systems?

[fizz57]

Uplinker's anecdote sounds remarkably like the third case study (1998, 747) reported in the "Aero 10" article linked earlier.

Interesting that while in some cases the flight crew actually managed to get the anomaly to return by turning the offending article on and off, Boeing has never managed to replicate even a single reported anomaly.

Probably requires a simultaneous fault both in the electronic device and in the aircraft shielding for anything to happen, hence the difficulty in tracking it down.

[Uplinker]

Thanks, Fizz. I've just looked at the one you refer to - I do remember that one too, but there was another earlier study in a science magazine longer ago which published a radar screen composite shot showing the sawtooth track variations. Sorry I can't remember the reference or the magazine but the old grey matter is not as reliable as it once was!

[aveng]

I have definately seen a mobile phone upset the nav equipment on a classic 737. I was called out to the flt deck years ago (when older style mobiles were around). When I got there the nav displays and ils info were going nuts. Even somewhat unrelated stuff was affected. I turned around and saw a guy speaking on his mobile in the forward galley (right above the main electronics compartment). When we asked for him to end his call and switch off the phone everything went back to normal.
It seems that newer generation aircraft are better shielded than older types. Especially if they are Fly By Wire. When I was at Airbus they said that they specifically test for these types of interferance during flight testing. Having said that, new eqipment is being designed every day that wasn't originally tested at a/c certification, that could have adverse effect.

As my old radio instructor used to say "weird sh*t happens with radio stuff".

[msbbarratt]

Passenger apathy and carelessness?

Flying back from FRA yesterday on LH, I couldn't help but notice that all the businessmen sat around me were quite happily browsing the web on their smartphones, including as we're coming into land.

Ok, so perhaps they were using LH's FlyNet, but that's WiFi only and these guys' mobiles were all showing 3G as being switched on too...

[Intruder]

Digital phones use less than half the power of the old analog phones, hence the much longer battery life for similar usage. My old phones would cause feedback through my computer speaker systems when I used the phone while sitting at the computer. I doubt there are many (if any) analog phones in use any more.

While I find it hard to believe a single modern cell phone could cause interference in an intact airplane, I often wonder if several hundred phones all vying for a signal could, in fact, put out enough power to induce signals in an antenna cable or other cable, especially if there is a shielding defect or loose coupling. I don't think it's beyond the realm of probability, and I wouldn't want to find out the hard way during a Cat III approach...

[andytug]

Inverse square law applies also, twice as far away from transmitter =1/4 power, 3x away = 1/9 and so on.
Probably nationally /internationally certified devices now problem, but some cheap foreign device putting out too much power, who knows? Aircraft manufacturers/operators would err on the side of caution I'm sure.
Presumably would be difficult to get an EMP device through customs, I hope!

[msbbarratt]

Originally Posted by andytug

Inverse square law applies also, twice as far away from transmitter =1/4 power, 3x away = 1/9 and so on.

That's true in free space, less so in an enclosed space such as a metal fuselage. All of the radiated power bounces around inside the airframe until it leaks out of the windows. For example, a phone at the dead centre of the fuselage is going to get quite a lot of its own signal reflected straight back at it. Every individual transmission or reflection still propagates according to the inverse sqaure law, but combined they can add back up to surprisingly high power densities...

[Purely as a matter of interest - tsunamis can happen a long way from the earthquake. A wave spreading out from an earthquake in, say, Chile gets refocused by the geometry of the planet (a sphere), and maybe you get constructive interference causing a big wave in Japan, thousands of miles away. Planets are spherical, aircraft fuselages are round-ish, you can see where I'm going with that]

Probably nationally /internationally certified devices now problem, but some cheap foreign device putting out too much power, who knows?

AFAIK standards compliance in mobile telephony is pretty tight, considering. For example, a 3G phone putting out more juice than it should will badly screw up the cell it's working in, and the network will cut off that phone to protect the operations of the network as a whole. There's precious little marketing advantage in "cheating", so they don't.

Besides, an unnecessarily more powerful power amplifier in the phone is more expensive and would ruin the battery life.

Aircraft manufacturers/operators would err on the side of caution I'm sure.

They do, though I'm concerned that their caution ("Flight mode now please") is not being shared by passengers. From what I've seen there's a developing mindset amongst passengers that "It'll be OK if it's just me doing it", which is great until they're all thinking like that and something really does go wrong. I admit this is limited, anecdotal evidence gleaned from glances between the seat backs, or at a neighbouring passenger's device, and noticing the signal strength bars/dots (iPhones make it particularly obvious).

Short of equipping an airliner with some fairly sophisticated comms intercept gear to detect and pinpoint phone transmissions, I've no idea how on earth anyone is supposed to deal with non-compliance of this sort. Bossy / nosey steward / stewardess demanding to examine someone's mobile? Unlikely, and they're confined to their seats during take-off and landing. On board jamming seems difficult (and it's currently illegal, on board and indeed anywhere else).

The danger in my view is that the level of passenger compliance will drop, and we'll never know it. Whether or not it ever becomes a problem or not I can't predict; as plenty of posters here have already pointed out, with radio weird stuff happens, and sometimes it's bad stuff, even if something (i.e. the aircraft) is designed to operate in a difficult RF environment.

The cell network operators themselves can determine whether a phone is on an aircraft or not. The networks already track handsets (it's a source of road traffic data, which they can sell). It's a simple matter to work out that the handset speed is implausible for surface travel. The operators could be compelled by law to deny service for 24hrs to phones that seem to be travelling at more than 250mph, actually make the handset owner suffer for ignoring aviation safety rules. That would ensure that passengers are motivated to comply.

Presumably would be difficult to get an EMP device through customs, I hope!

I sincerely hope so too!

However, there's already a problem with mobile jammers sold on the black market; people use them on trains to shut up noisey fellow passengers who are having a loud phone conversation. The thought of these becoming widespread on aircraft too is terrifying. Short of a detailed examination of all electronic devices being taken through security there'd be no realistic way of stopping people carrying them and using them.

As things stand there seems to be plenty of passengers who irrationally disregard all sorts of flight rules. The "It'll never happen to me" mindset simply doesn't get weeded out. How many passengers get badly hurt when an airliner encounters a bad patch of clear air turbulence? Yep, there's always a fair few who didn't keep their seatbelt buckled up.

In my opinion this is a solid reason to keep the ban on mobile use in place, even if the aircraft manufacturer deems mobile usage to be safe. People being allowed to speak on their mobiles in flight will result in other people carrying and using black market mobile jammers with potentially high emissions and unpredictable results for aircraft operations. That really could be a dangerous thing. Keep the ban in place and it'll simply never occur to anyone to use one.

[andytug]

Apart from anything else, a ban would stop us all having to listen to a whole load of people's loud inane conversations....