Research: Mobile Phones Disrupt Aircraft

threeturn writes "Another contribution to the ever-popular "mobiles on planes" topic. Every time this is discussed on /. lots of people say "there is no danger - its just the airlines trying to make a buck on their skyphones". Well, now the UK Civil Aviation Authority has done some research which shows mobiles on planes do disrupt safety systems and interfere with compass readings and other navigation equipment. Also reported by the BBC. So do us all a favour and switch your mobiles off next time you fly."

Comments

I think this is good

[xmda]

Well, when it comes to airplanes and flying I think the expression "better safe than sorry" fits the bill quite nice.

Re:I think this is good

[VCAGuy]

"better safe than sorry"

Yes, it's generally not an indicator of common sense to compromise the very safety systems that are keeping you alive whilst you are being propelled at mach ~0.78 at 30,000' MSL...but, that's why common sense isn't all that common!

Re:I think this is good

[anshil]

If airplanes are already sensitive to the not so dramatic electromagnetic impact of simple little mobil phones, what would that mean to somebody who in act of terrorism wants to make strong em. impact on purpose?

Re:I think this is good

[TopShelf]

Not only that, but have you ever sat next to some schmuck who feels he has make a call as soon as the wheels hit the ground? And we're not talking some urgent business communication - it's more like "yeah, we just landed... I think I'll grab a burger and be there in an hour... yada yada yada..."

I say, install automatic detection systems for wireless devices, identify the location of the phone and put it on the screen for all passengers to see. Let them then decide what to do about it - I think after a few blanket parties the message will get around!

Re:I think this is good

[xmda]

Err... That is like saying that the sefaty belt in my car cannot save me from a bomb planted in the car. I'll say it again, better safe than sorry.

Re:I think this is good

[_Swank]

no, i'm offended that my seatmate thinks that the 5 minutes he's saved by calling at touchdown is more important than respecting the people around him and not disturbing them.

i've heard a very large number of these touchdown calls (i fly at least twice a week) and not a single one has yet been urgent enough to warrant the abuse of everyone in the vicinity.

Re:I think this is good

[Drakonian]

Well, now you have a secret weapon when the terrorists have hijacked the plane. Just whip out your cell phone.

Re:I think this is good

[spakka]

"yeah, we just landed... I think I'll grab a burger and be there in an hour... yada yada yada..."

They make calls about free NY Times registration?

Re:I think this is good

[anthony_dipierro]

Except for the fact that bombs aren't allowed on planes, but electronic devices are. Maybe we should think about disallowing mobile phones as well. Better safe than sorry.

Re:I think this is good

[h4x0r-3l337]

If I am stuck next to random stranger X, then certain courtesy guidelines come into place. Among them are not picking my nose and eating it, screaming profanities, masturbating, and talking on a cell phone, listed in my own order of rudeness rating.

So next time the guy next to you makes a phonecall, show him you can do better and start masturbating. If he counters by screaming profanities at you, pick your nose.

Re:I think this is good

[rifter]

I have noticed that people tend to talk much louder on their phones than they normally talk. This is what ticks me off - when I am in a quiet setting like maybe a restauraunt and then someone uses their at-a-soccer-game voice.

This is because their phone/service sucks. On many phones if you do not yell no one can hear you (and even then it is sometimes problematic. This was the case with my previous Samsung/Sprint combination. With my nokia 3590 and at&t using gsm I can speak with a normal voice even with the phone slightly away from my face (like while taking down a number) and the other person and I have no problem hearing each other.

I think it is silly when cell phones do not have a higher range for their volume controls, since this is the cheapest thing to change and dramatically changes the customer experience w/r/t how the reception is perceived (if you can turn it way up and hear, then you will think you have ok service as long as you aren't cut off). Too bad everyone can't have phones designed by Spinal Tap! :)

As an occasional airline passenger

[Vengeance]

I'd REALLY REALLY REALLY like to see Boeing, Airbus et al. installing avionics and comms systems that can't be disrupted by ubiquitous and nearly free techno-gadgets.

Re:As an occasional airline passenger

[bmongar]

My impression is that newer avionics are 'more imune' to the interference. It's all the electrinocs pre 1989 that are prone to interference. It's just that there are a lot of planes out there that pre-date 89 and there will be for a while.

Re:As an occasional airline passenger

[mhotas]

Seriously... the system as it stands couldn't be any more broken, as it depends for its safe operation on the active opting-out of every cell carrying passenger. I mean, phones ring in college lectures all the time -- I've seen it happen to professors who have very clear policies about turning them off.

Re:As an occasional airline passenger

[Anonymous Coward]

True, but you're forgetting that back in the 60's and 70's, GHz-based transmissions were pretty much unheard of at 30,000 feet so various electronic packages aren't shielded adequately. Lots of these planes have a range of systems onboard that may have been built at any point in the last 30 or so years, retrofitting all of them will take time and a lot of money, something the airline industry is not too keen on right now.

I'd expect to see newer planes kitted out in such a fashion though. What better way to ensure aircraft sales than to say "yup, business class passengers can still use WiFi and their mobiles... on our new jets..."

Re:As an occasional airline passenger

[scsirob]

You are right of course, but this is why the danger exists. Many aircraft have been certified with way-back technology, and it doesn't pay to re-certify these airliners with hot, new goodies that are designed to live in peace with mobile phones and other wireless toys.

Avionics system designs are very conservative, it's all designed to work forever. Latest-and-greatest simply doesn't fit their books. With the track record of modern software, I don't think we should be sorry for that..

Besides the danger to the aircraft, the mobile networks are also not designed to handle mobile phones moving between cells at 500mph and 'visible' to every cell in a 100 mile radius.

Re:As an occasional airline passenger

[Arker]

I'd REALLY REALLY REALLY like to see Boeing, Airbus et al. installing avionics and comms systems that can't be disrupted by ubiquitous and nearly free techno-gadgets.

I'll second that.

Having read the article, there are some interesting points. First off they aren't alleging that using your cellphone will make the plane crash, but rather that it might cause some sort of distracting noise in the crews headsets and at worst could conceivably cause a false alarm on one of their warning lights. Sounds a little iffy to me, but ok, better safe than sorry on a plane... then I read on.

Turns out it doesn't matter on new jets - only ones certified pre-'89. So why don't they let people use their mobiles on the newer planes where it's not an issue? Back to the old 'conspiracy theories' on that one. Controllers like control. And the high prices on the sky phones can't hurt either.

Plus, as you kind of hinted at, if a cellphone can really cause even minor systems disruption on a pre-'89 jet, just imagine what someone that was seriously trying to cause a problem could do. It's absurd. If those jets really do have systems that can be so easily disrupted, they should be grounded until they're fixed. So either way, something doesn't add up here, either they're lying (or maybe just stretching the truth very far and very consciously) or they're not even trying to do their job, take your pick.

In an age when we know there are people trying to bring jetliners down, it's absolutely absurd to be flying jetliners that are so poorly insulated against EM interference that a mobile phone is a threat to them. Period.

Re:As an occasional airline passenger

[PetiePooo]

But you don't have to worry about this while at 30,000 feet. Up there airplanes are separated by miles.

Not true. There can commonly be as little as1000' separation with a combined horizontal velocity of 1400mph or higher.

Flight levels above 18,000' alternate between easterly directions on the odd-thousands and westerly directions on the even-thousands. The altitudes are determined by pressure altitude and monitored carefully by radar. The altimeters are precision instruments and frequently calibrated.

So, a 767 flying at 250 degrees at flight level 280 (28,000 ft) can meet a 757 flying at 70 degrees at flight level 270 (1000 feet below) along a published airway, and it would not be unusual circumstances. ATC (and their onboard collision detection system) would keep them aware of each other.

Re:As an occasional airline passenger

[DonGar]

What about the cumulative effect of a hundred phones at once? If you don't ban them, then almost all passengers will leave them on.

I'm not sure if this really matters or not.... I'm asking.

Cell phone towers are the problem

[ShwAsasin]

The biggest problem when flying and using mobile phones is the phones themselves. When you are flying, the phone may try to communicate (roam) with many towers which causes cell network problems. Imagine the area of towers you could hit at 30,000ft in the sky.

Re:Cell phone towers are the problem

[trapdoor]

> Imagine the area of towers you could hit at 30,000ft in the sky

Quite a few, if the signal was strong enough to travel 30,000 feet. That's 10,000 yards. Which in (British at least - don't know about US) miles, is about 5.5 miles. This might work along the ground, but straight up in the air???

I worked for a while almost at the top of the new HSBC building in London's Docklands. It's only a little shorter than Canada Tower (Britain's tallest building), but above about the 40th floor, you lose your phone signal and can only intermittently make calls.

Therefore, I think that the danger comes not from communicating with cells, but the phones continually searching for cells (which does involve transmission I believe). They do this every few seconds. An unscientific way of showing this is when you are out of range, the battery life of phones left on standby reduces dramatically, due to all the extra transmissions.

Re:Cell phone towers are the problem

[doctor_oktagon]

Eh Hullo?

I'm sure the Airlines couldn't care less that their passengers are screwing up the Telco systems - they are far more concerned about the effect on their planes!

Hence the biggest problem is the interference with the avionics, NOT the telco problems it creates!

Re:Cell phone towers are the problem

[Lumpy]

Imagine the area of towers you could hit at 30,000ft in the sky.

not many at all.

First Cell site antenna array's are high gain and therefore squeeze the signal to the horizon, second they tilt the antennas downward to limit the cell sites coverage in regards to adjacent cell sites.

It amazes me how many times this comes up on cellphone doscussions and how suprising it is to find how many people have no clue as to the basics of how a cellsite operates.

Re:Cell phone towers are the problem

[cruppel]

You're right, cell phones were never designed to work at that altitude with so many towers in sight. Three towers is basically the magic number (the least number of points to make a cell). Also, the cell phones were designed for day-to-day activity, such as walking or driving around. The sheer number of cells within the phone's sight in a plane coupled with the speed at which you are traveling makes it pretty difficult for the phone to behave.

This has no bearing on whether or not it's OK for a phone to operate on a plane. Shit, the old planes may not have shielding for transmissions of that frequency (old ones at least), but I've been asked to put a four-function calculator away during the middle of the flight at cruising altitude... they just don't want to worry about technical problems like that I guess.

Re:Cell phone towers are the problem

[wowbagger]

True, a cell site puts most of its signal out horizontally, and receives horizontally.

That only makes the problem worse.

Consider: You are at 30000 feet, and your phone is on. Its listening for a control channel, and finds one. It does a registration.

Now, several factors are reducing the signal strength of the control channel to the phone: distance, the gain pattern of the site's antenna, and the fact the phone is in a big metal box with small holes in it. So the phone will have a very low RSSI (received signal strength indicator), and will put out maximum power to reach the site.

Now, because the altitude, the angle the signal comes in at and the distance are not going to be very much different for many cellsites - each is going to receive the phone about equally well. This actually tends to EXPAND the range of sites affected - the sites under the plane suffer from the gain pattern of the signal and the emission pattern from the plane (most of your signal is going out horizontally from the windows, modulo knife edge scattering), but get a boost from proximity. The sites far from the plane lose signal due to distance, but now the signal is coming from a lower angle and is in the higher gain portion of the antenna pattern.

Now, cell sites are laid out in a pattern - usually in most urban areas it is a hexagonal pattern, with adjacent cells using different frequencies and DCC (digital color code - basically a number that helps the phone tell the difference between sites). So there WILL be several sites that will match the frequency and DCC the phone is using.

Now, for CDMA systems ALL those sites have to swap data about the signal they are receiving (this is to implement "soft handoff" where the phone gradually changes which site it uses - for a time the phone is actually using 2 sites at once.) This GREATLY increases the data bandwidth used between sites.

For GSM it's a little different - but the upshot is you are STILL confusing the sites and forcing them to talk to each other over the landline connections.

Meanwhile, here is your phone blasting out bursts of RF at maximum power to try to register to the cell site it hears - only to have to register AGAIN a few seconds later because it has moved out of range.

So, your battery will go flat very quickly (the way these new phones keep battery life up is by not being on all the time - they only listen during their assigned time slot, normally. However, when the phone detects that is has changed sites, it must re-register and listen to ALL time slots until it gets one assigned.)

Also, you are tying up resources in the cell system.

Lastly, you are pumping out a fair amount of RF power inside this big metal box full of wires. What is another term for "wire" - ANTENNA. Each of the wires in that plane is detecting some of your radio's signal, and any non-linear element (corrosion, a semiconductor, etc.) can act as a detector to convert the RF into DC. (Think about the old style crystal radios, or the foxhole razor blade radio).

When you do EMI complience checks, you will be amazed at what can act as a receiver and make things go screwy. All sorts of things that you might think "this cannot interfere - it's gigahertz away!" start interfering.

Even worse...

[Mostly Monkey]

Better not play a flight sim on a 802.11 equipped laptop or the plane will REALLY be in trouble.

A little too late here

[Ores]

A text message sent to a passenger is one theory for a crash that happened last Friday.

News link

I'm sure I read somewhere though that an airline was going to use wireless for flight attentents.

802.11[a|b|g]?

[kipsate]

Can anyone explain why apparantly 802.11b wireless connections do *not* pose a problem in planes?

Re:802.11[a|b|g]?

[monkey_tennis]

Frequency and power - GSM units utilise 900, 1800 and 1900 MHz (depending where you are) 802.11a/b/g uses 2.4 and 5 GHz. In terms of power - just look at the distances involved WLAN tops out at 300 feet without obstructions, phones can manage a bit more :)

Re:802.11[a|b|g]?

[VCAGuy]

I think it's because the only other thing in the 2.4GHz spectrum for aircraft is the WX radar. And since it points forward through the aircraft's nose, anything behind it won't affect it. Also, those transmissions are all within the Faraday cage that is the aircraft's skin--none of those transmissions have to leave the plane (and won't anyway, because of the frequency). Aircraft have onboard microwaves, so I don't think that 802.11b|g poses a problem (don't know about .11a, though).

do you even get reception?

[mydigitalself]

um, on the point of it being a plot to make you use their expensive sky phones...

would one even get reception up there? not only up there - but in there (metal cylinder)?

Re:do you even get reception?

[Vengeance]

Of course. Remember the cell phone calls from the Pennsylvania flight on Sept. 11, 2001?

Longer term solution

[monkey_tennis]

As a frequent flyer I'm more than happy to comply with requests to turn off my phone on planes, but recently air-crew have not been tech savvy enough to recognise a P800 'smartphone' in 'flight' (phone bits off) mode. In these cases I offer an explanation and then comply if they insist it goes off, but as all kinds of wireless tech gets built into PDAs, laptops and watches how will they know? Just because it doesn't look like a phone doesn't mean it isn't...

My guess is aircraft will need better shielded systems.

Full report here

[Quixote]

The full report can be viewed here .

From the executive summary:

In October 2002, a set of avionic equipment was tested under controlled conditions in a test chamber for susceptibility to cellphone interference. General aviation avionic equipment, representative of earlier analogue and digital technologies, was used. The equipment, comprising a VHF communication transceiver, a VOR/ILS navigation receiver and associated indicators, together with a gyro-stabilised remote reading compass system, was assembled to create an integrated system.

The tests covered the cellphone transmission frequencies of 412 (Tetra), 940 (GSM) and 1719MHz, including simultaneous exposure to 940 and 1719MHz. The applied interference field strengths were up to 50 volts/metre for a single frequency, and 35 volts/metre for dual frequencies.

The following anomalies were seen at interference levels above 30 volts/metre, a level that can be produced by a cellphone operating at maximum power and located 30cms from the victim equipment or its wiring harness.
snip

I am wondering: how realistic is a test which assumes that the phone will be 30cm from the equipment?

Re:Full report here

[Lumpy]

The applied interference field strengths were up to 50 volts/metre for a single frequency, and 35 volts/metre for dual frequencies.

ok now how about running the same test with REALISTIC amplitudes... no cellphone on this planet can generate 50V per Meter.

Cripes, my ham gear transmitting at 25 watts is only at 11 volts per meter as measured by a field strength meter...

Sheesh I might as well report that cellphones make cars unsafe because when I put the car's computer in my microwave oven and set it for 10 minutes the electronics fry out..

Call me when they perform a real test.

Damn! It doesn't say 'Ashcroft'

[Surak]

For a second there, I thought it said "Mobile Phones Disrupt Ashcroft." And I was ALL SET take my cell phone down to the White House! :-P

Foil Hat

[dfn5]

We could build a really big aluminum foil hat to put on the cabin and block those signals.

Upgrades do need to happen, although...

[Vengeance]

Granted, it takes the airlines forever to agree to small safety changes like, oh, I don't know... Installing non-flammable seat cushions?!? I guess we can't really expect too much in the way of retrofits, particularly in today's economic climate.

We bail 'em out, they waste it, we'll just bail 'em out again.

my own experiment...

[Anonymous Coward]

I used to be firmly against the interference argument - until one day at work I heard my hardline phone making all kinds of weird buzzings and beepings. Oddly enough, they sounded identical to the noise I occasionally get on my cell phone. The cell phone, not surprisingly, was sitting right next to my hardline phone. After moving my cell to various positions, I discovered that it does indeed interfere with my hardline phone. When I moved the cell away the periodic noises stopped, and when I placed it next to the phone the noises began again.

Now, I seriously doubt my phone operates anywhere near the band that my cell uses, but for some reason the cell manages to interfere. Based on the outcome of this little experiment, I would definitely believe that cells could interfere with other systems - including aircraft systems - even though it may seem counterintuitive.

Re:why?

[feepcreature]

And for those of you who need to play nibbles or whatever... you need to unplug and get more fresh air or something.

On a plane????

Have you ever tried winding down the windows?

Re:No, just like always

[halftrack]

as we all know, Linux developers are all high flyers in the world of business and are always on the move, meeting new people.

That's if they can decide how to put the plane together.

Bah!

[Greyfox]

They're probably just saying that to give the air marshalls an excuse to rough up those self-important assholes who can't shut the fuck up for four goddamn hours. Face it, if you're riding in someone else's plane, your life just isn't important enough to warrant you jabbering on a cellphone to anyone, anyway.

Talking on a cellphone while any vehicle is moving should be a crime punishable by a severe power stapling. Or caning, as they do in Singapore. Yeah... I've had 3 suvtards in the last month nearly take me out while driving their Maibatsu Mostrosities with cellphones glued to their ears. You may as well just down a fifth of Jack Daniels before getting behind the wheel of that thing. Shut up and drive!

They proved nothing ...

[binaryDigit]

at least according to the bbc article.

It found evidence that calls produced interference levels which could disrupt aircraft systems. Faults that could be attributed to mobile phones use include ...

I see a lot of "coulds" and not a single "did". So what they found was that they have no better information now than they did before. Did they observe a single instance where there was interference? It's seems highly dubious that they couldn't construct a scenerio where they could conclusively show this "error".

And it's been stated before but I think it's worth mentioning again. By god, if cell phones are really capable of such chaos, why on earth do they allow them on the planes to begin with? Just what I need is to have someone bring down my plane because they forgot their phone was on in their briefcase, or 6 members of some terrorist org only need to start sms'ing each other to take down a 747 full of people. There is a severe disconnect between what the FAA is claiming and their actions taken. What, I have 5 people make sure I don't bring finger nail clippers onto the plane, but no one cares that I can bring the entire thing down with my Nokia?

Re:DILDOS: "portable electronic devices" ???

[Havokmon]

My electric razor causes enough interference to screw up the television set, so dildos could theoretically do the same.

You idiot, the tv doesn't get screwed up, that's the razor making your face vibrate.

Just turn them off....

[wrero]

The rules regarding portable electronic devices predate cell phones and the air-phones in aircraft. While I don't disagree that perhaps part of the reason they haven't been approved is because the airlines don't want them approved for use, perhaps part of the problem is that the airlines actually DO want to make things as safe as possible without dramatically over-inconveniencing people. If there is any chance at all that cell phones MIGHT screw up something once out of every 10,000,000 flights, what's wrong with them being that tiny tiny bit safer? Or even having the perception of being slightly safer?

It *is* up to the airlines to decide if a particular device is or is not to be used. What I mean by that is that although rumor has it that cell towers get screwed up if a phone "sees" too many of them, it's under the FAA's and the airline's discretion. Although I could be wrong, I am unaware of any FCC rule that says that cellular telephones are not to be used on planes.

For what it's worth, here is the relivant FAR:

125.204 Portable electronic devices.
(a) Except as provided in paragraph (b) of this section, no person may operate, nor may any operator or pilot in command of an aircraft allow the operation of, any portable electronic device on any U.S.-registered civil aircraft operating under this part.
(b) Paragraph (a) of this section does not apply to --
(1) Portable voice recorders;
(2) Hearing aids;
(3) Heart pacemakers;
(4) Electric shavers; or
(5) Any other portable electronic device that the Part 125 certificate holder has determined will not cause interference with the navigation or communication system of the aircraft on which it is to be used.
(c) The determination required by paragraph (b)(5) of this section shall be made by that Part 125 certificate holder operating the particular device to be used.


At any rate, and I know I will be slammed for this one: Why can't people play by the rules, ever? It seems that quite a few people don't turn off their cell phones on aircraft. It seems that these are the same people that get up before the airplane gets to the gate; the same people that don't turn off their cell phones when going to the theater. How much, really, does it harm your personal liberties to play by the rules occasionally, and turn off the damn things when on an airplane? This society seems to always be "me me me me", and this just seems to be a symptom.

So make the guy sitting next to you feel better. Put your seatback in the upright position when they tell you to, turn off the laptop when you should, and leave the cell phone off.

Mobile networks

[Gordonjcp]

I got a letter from Orange once, complaining about my phone jamming six adjacent cells (two cells that normally can't see each other suddenly both get the same phone at the same time). This was from having my phone switched on in an aircraft at around 3,500 feet.

Re:Mobile networks

[mduell]

I was on a 2 mile final for San Luis Obispo airport in Cessna 172 and my pax phone went off, causing a lot of static on the radios (just ringing, he didnt actually answer) and causing the magnetic compass to oscilate a bit.

good, fix it

[Trailer Trash]

Fine, so cell phones really do disrupt airplanes. I still don't believe it, but, if it's true then we've identified an exploit that needs to be fixed. "Please turn off your cellphone" is not a fix.

"Software company X has identified a buffer overflow in our popular Y software, which can lead to a remote root exploit. Rather than fixing it, we're asking that you please don't connect to port yz and send a string that is 5000 characters long and ends with the binary sequence..."

Moronic. Fix the bug and quit boring us with the details.

Michael

Re:Opting out

[squiggleslash]

You're required to continue your conversation outside...

Re:People will leave phones on

[mesocyclone]

Clearly they need to install shielding

Much easier said than done! There are miles of wire. Any break in the shielding can be enough to cause problems. Any corrosion can too.

Furthermore, the phone can cause interference by other processes, for example:

Your phone starts transmitting. It is at high power because it is hearing a weak signal. It's signal gets into your walkman via the headphone cable. Another signal, perhaps from a radio on the aircraft or another cell phone or whatever, also gets into that same cable. The two mix because the walkman is non-linear at those frequencies. The result is on the radio communications frequency, the ILS (Instrument Landing System) frequency, or GPS band.

In general, this whole thing is about incrementally improving safety. The odds of a single cell phone on a single flight causing a crash are very low. But the odds get much larger when you are talking millions of cell phones on hundreds of thousands of flights.

Even then, the cell phone may just *contribute* to an accident. Most commercial air crashes are a result of a cascade of individually recoverable failures or events. The cell phone may simply take out a backup system at a critical time, or it may interfere with a primary system (say, glideslope) while the pilot is distracted by another urgency.

For those who comment about how the presumably more susceptible legacy systems on the aircraft should be replaced... the systems mentioned include such minor systems as the only air-to-ground communications mechanism used for air traffic control, and the only instrument landing system available for many airports. Replacing this "legacy" infrastructure would require replacing every aircraft radio in every aircraft, control tower, air traffic center, etc in the world, and replacing all of the Instrument Landing Systems.

This is not trivial. Furthermore, in aircraft, it is not a good idea to rapidly replace systems that have been working and safe!

Re:Opting out

[rifter]

It would be interesting to find out. In the US, with the advent of Air Marshals, even the smallest infractions are now enforced (a man was tackled and arrested by the Air Marshals for *wanting* to go to the bathroom while the seat belt sign was on. He had asked the flight attendant repeatedly to let him go, but never actually went...) The Article, which no one reads, talks about a man being sentenced to 12 months in prison in the UK for having his cell phone on (and not using it) during a flight.

I am annoyed to find out, however, that the whole thing is bogus. Once again "journalists" (what passes for them these days) misreport findings in an uncited study that was flawed in the first place. The study *did not* find that cell phones disrupt flights. They did not even use cell phones for their tests. So the science behind this simply is not there.

Experience (as a pilot) with GSM

[Alioth]

This is my experience with (accidentally!) left on mobile phones (GSM variety) in aircraft.

I fly light aircraft. On a dark, rainy night, a friend and I was approaching Ronaldsway. My friend was the 'handling pilot' (i.e. the guy who's waggling the stick), and I was in charge of the radios - setting up frequencies, identing navaids, talking to ATC etc. Although our aircraft (a Grumman Cheetah) only requires one aircraft, we fly together reasonably often and find this arrangement works very well.

My friend was at the time a very new instrument pilot. Ceilings (the bases of the clouds) were about 800 feet, winds were light, and it was pelting with rain. It was about an hour after sunset.

We were just intercepting the localiser (the horizontal guidance part of the ILS - instrument landing system), and we had been cleared for the ILS approach.

Suddenly, the radio was blotted out with:

'Bip-b b b bip b b bip b b bip b b bip' - the highly recognisable radio interference from a GSM phone. My friend had forgotten to switch it off when we had taken off an hour and a half earlier. His wife was phoning him.

It completely blotted out the COM radio with the extremely loud 'Bip-b b bip b b bip bzzzzzzzzzzzz' noise as the phone went off. However, it did not intefere with the nav radios nor the compass - the localiser needle continued to behave how it should have, as did the other instruments (the direction indicator, for example, is gyroscopic) and it did not affect the compass. However, the noise was extremely distracting, and if ATC had any further instructions, we had no chance of hearing them until we got the phone shut off or my friend's wife hung up.

Fortunately, with two of us on board, it was a non-event (I could fly whilst my friend turned the phone off).

An important point to remember: aircraft fly on the rules of Bernoulli and Newton, not the rules of Marconi! It's perfectly possible to fly without radios. The problem is in instrument conditions (i.e. in the clouds) where you can't navigate by looking out the windows. Even so, a prudent pilot always plans an 'out' in case of radio failure, and does not bet their lives on the continued operation of the com and nav radios!