Does electronic equipment actually interfere with aircraft systems?

[scanman24]

Hi all,

I was recently reminded by a safety video that "electronic devices fitted with a transmitting function may not be used unless in flight mode, and must be switched of for take-off and landing" (or something to that effect). This got me thinking - why? It seems plenty of people use their electronic devices at all stages of flight, and with some airlines introducing wi-fi onboard I'm wondering to what extent - if any - safety is compromised through their use.

I'm not trying to endorse their use in complete disregard of air law, but I'm intrigued nonetheless.

Cheers.

[WhyByFlier]

In 'flight mode' I'd be extremely surprised if it has any effect. In my airline we're even flying with iPads cradled into the flightdeck with plates and manuals on the ipad.

Devices would need to be handed in if there was a real threat.

All this talk of electromagnetic interference! The plane can take a lightning strike for crying out loud.

[ShyTorque]

Some do, some don't. Rather than hold up the flight try to identify which are which on a passenger flight (and sort out the ensuing arguments from disgruntled pax), a blanket ban does the job.

For one example of interference caused by an electronic device, I used to fly a helicopter type where a live mobile phone being "polled" in flight would bring on the aft baggage bay smoke warning. Because there was no fire extinguisher in that bay, the warning coming on in flight meant an immediate landing. Not easy or safe over hostile terrain, in bad weather, or at night.

The anomaly was that the manufacturers said it shouldn't / didn't happen. That was probably because they hadn't carried out trials using the European phone frequencies, only those used in USA. Descending towards the sea at night, thinking the aircraft tail is going on fire, is no time to find these things out.

[Brian Abraham]

ShyTorque, one of our guys had exactly the same thing happen in Australia (S-76).

[FlyingStone]

One of the reasons for the restrictions on use of electronic devices during take-off and landing is that they could start flying all around the cabin during abnormal manuevers (such as rejected takeoff). And I don't think anybody wants to be hit in the head by an iPad, weighing more than 500g doing couple of m/s.

[QJB]

There is a pretty good Boeing article on this in their Aero magazine.

Aero 10 - Interference from Electronic Devices (http://www.boeing.com/commercial/aeromagazine/aero_10/interfere_textonly.html)

[Bergerie1]

There have also been cases where electronic devices (mobile phones, etc.) have caused under-floor freight bay fire warnings on B747s - not proven but highly probable. As with the helicopter example in a previous post, a fire warning at a critical phase of flight or when way out over the ocean is not pleasant and is a significant cause for concern.

[roulishollandais]

And what with Lithium batteries overheating of these devices...? :eek:

[ShyTorque]

ShyTorque, one of our guys had exactly the same thing happen in Australia (S-76).

Yes, same type. ;)

[compressor stall]

I've had the phone ring on a turnaround (A320 family) and simultaneously watched "GPS primary lost" appear, and the airport and SID slew over to the side of the ND. (20 mile arc IIRC).

All came good once I answered!

[bubbers44]

I have been guilty of as a captain leaving my cellphone on and it going off at 3,000 ft on approach telling me I had a missed call. I don't know if cell phones cause any interference but have had a couple of flights when all long range navigation failed in a Boeing 727 but worked when all passengers and baggage was removed at destination. Something in checked bags or carry on must have caused it.

[pukua]

If it can't be certain NOT to interfere with the flight it will be banned as no organisation will stick their neck out to say it is safe in ALL circumstances! Certain electronic devices that are tested for flight deck use only or other restricted use will be approved as testing and liability is established.

[scanman24]

Thanks everyone for the input - question more than answered!:ok:

[John Farley]

Does electronic equipment actually interfere with aircraft systems?

I think that might rather depend on the (portable?) electronic equipement concerned and the aircraft it was being used in as well as its position in the aircraft. I really can't imagine an question that is likely to have more variables.

As has been suggested testing a specific bit of kit under specific circumstances in the aircraft might allow clearance of that kit - but a blanket 'go ahead' seems unlikely.

[fizz57]

I remember reading an article in some journal or other a few years ago about a researcher who carried a spectrum analyser in his tote bag on a number of flights to record cellphone activity (probably with authorization - he was quite an anti-electronic-devices activist).

His results showed a surprising amount of activity on each and every flight. Of course, he interpreted this as being indicative of the magnitude of the problem. But if that is the case, why aren't planes falling out of the sky like flies?

[darkroomsource]

Not like flies, but there have been a few cases where planes ended up hundreds of feet away from the end of runway, and if the weather had been worse they might have been hitting buildings.
We've been lucky so far.

[WhyByFlier]

From Airbus A320 FCOM FCB-FCB8 P 1/2


‐ Airlines often wonder whether they should allow passengers to operate electronic devices in the cabin without any limit. Federal Aviation Regulation (FAR) section 91.19 allows passengers to operate: • Portable voice recorders • Hearing aids • Heart pacemakers • Electric shavers • Any other portable electronic device that the operator of the aircraft has determined will not cause interference with the navigation or communication system of the aircraft on which it is to be used. It is obvious that the myriad portable devices that now exists or that may be available in the future cannot be tested. ‐ As far as aircraft specific electrical flight controls and engine control computers on Airbus aircraft are concerned, there is no chance of their operation being affected by passenger-operated electronic devices, due to the high level of protection applied to these systems. ‐ Nevertheless, this question arises for navigation and communication receivers and is applicable to any aircraft. A study has been conducted by an RTCA (Radio Technical Commission for Aeronautics) special commitee. ‐ The conclusion is that the probability of a passenger-operated device interfering with the ILS localizer during a typical flight is about one in a million. Airbus Industrie recommendations is that no portable device should be used during take-off and landing. ‐ Concerning radio phones Airbus Industrie recommends to prohibit the use of those devices.

[NSEU]

and with some airlines introducing wi-fi onboard I'm wondering to what extent - if any - safety is compromised through their use.

Standard tests are carried out to try to ensure that they don't affect aircraft systems, but like any electronic devices, they can develop faults which are unexpected. Even thoroughly tested Inflight Entertainment Systems (on and off-wing) have interfered with airplane systems. Even though, in many cases, the system problems are only minor, they may cause distractions at critical times.

[grounded27]

99.99%, hell no. .01% mabe. Liability 100% for .01%.

[Uplinker]

Airbus, and probably all modern aircraft, use heavily screened cables to reduce interference from external sources, but that is not a 100% guarantee. As others have said, you don't want to find out at the DH that your CatIIIB autoland is 50m off laterally. At best; a go-around and a delay, at worst...........

I remember a study in the ?80's that showed radar tracks of aircraft - and one was flying an airway in a series of 'sawtooth' steps instead of a straight line. Radio interference from a laptop, I think, was the culprit.

[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".:ok:

[msbbarratt]

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]

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....