View Full Version : Mobile Phones on Aircraft CAA Report

no sig
2nd May 2003, 00:25
In case you've missed it...

CAA Paper 2003/03: Effects of Interference from Cellular Telephones on Aircraft Avionic Equipment

See at the attached link:


2nd May 2003, 01:44
Thanks for that link, no sig. Very important research. :ok:

Here's a small excerpt from the Executive Summary, which I will probably carry in my kitbag (to show to anyone who thinks the cell phone ban is unjustified) :

Compass froze or overshot actual magnetic bearing.
Instability of indicators.
Digital VOR navigation bearing display errors up to 5 degrees.
VOR navigation To/From indicator reversal.
VOR and ILS course deviation indicator errors with and without a failure flag.
Reduced sensitivity of the ILS Localiser receiver.
Background noise on audio outputs.

In the "Background" section, there was also a list of actual events which were reported and which prompted the research. These were:

Distraction of the flight crew from their normal duties;
Interrupted communications due to noise in the flight crew headphones;
Increased work load for the flight crew and the possibility of invoking emergency drills;
Reduced crew confidence in protection systems which may then be ignored during a genuine warning;
Malfunctioning of multiple systems essential to safe flight.

2nd May 2003, 03:06
Couldn't open it :(
Would someone be so kind as to send it to me under another form? Please? :sad:

[email protected]

2nd May 2003, 03:31
Come now. I would have thought pilots would be more logical than this.

I have literally hundreds of hours of flight testing where the plane is in "experimental" condition and we use cell phones to communicate with people on the ground and I have never seen any bad affects on instruments nor has any of the pilots complained.

There is no merit to the theory that these or any other common electrical devices do cause problems. Yes, get painted by tracking radar and you will see some pretty interesting things happening to your instruments, especially radar.

Modern Cell phones have a transmission range of several miles lateraly and about 10,000-12,000 ft in height. An elyptical bubble so to speak. When you are taking off and landing your aircraft is literally getting bombarded by hundreds if not thousands of cell phone signals depending on what airport you are at.

There are two reasons why they like to say that cell phone use can make an airplane crash....

1. There is no way for the airline to make money on the use of the cell phones and all those millions of dollars spent on air phones would go down the drain cept when you were out over the pond, but then satellite phones will work if you are by the window.
2. Airlines do not like things in peoples hands that can get exposed to excessive g force that fly down the cabin and kill the person whom it hits in the head. This is why they come by with garbage sacks for jewelry, etc if you may have to ditch.....less crap flying through the cabin as people's bodies come apart.


2nd May 2003, 03:59
So you get away with it, maybe dozens of times, but the point missed is that operation of a radio transmitter inside the fuselage from random positions is going to cause equally random inductive pickup in the aircraft wiring system.
Remember that this is a digital pulse signal which will produce equally random effects of the kind outlined in the CAA report.
All transmission equipment that form part of the aircraft installation have external antenna that are placed in positions that are only approved only after extensive testing and evaluation has proven that there is no interaction.

2nd May 2003, 04:56
747 focal

your comments show you do not understand certain physics principles which are essential to grasp if you wish to comment intelligently on the subject

have a nice day

2nd May 2003, 05:47
Its a shame that there are now multiple posts on the same subject within different sections of this forum.

AsI posted in yet anothe forum section,

What are the chances of a passenger being within 30 cms of the critical device wiring as stated in the report?

Yea, I know that wiring runs all over the aircraft, but what devices actually meet this 30 cms data or less, relative to the passenger?

My initial read suggests that the pilot better beware of using a cellphone at the same time he is relying on critical instruments (duh)

2nd May 2003, 14:41
747Focal I can appreciate your dislike for the "prissy" attitude that some folks take toward air safety. Certainly the quest to sanitize everything can be overdone.

On the other hand, your anecdotal experience, even a lot of it, doesn't count for much either. Who is to say that there might not be a problem under slightly different circumstances?

I've had the (anecdotal) experience of instrumentation and inflight computing systems shutting down or at least limping for awhile from TWX and sunspots and mil radar sweeps, microwave relays, AM and FM antenna towers and misbehaving onboard systems. Except for the focussed beams and galactic things, distance is the key, thanks to the 1/Rcube dissipation of power over distance from a source radiating in all directions, so a teensy cellphone in the forward lav really can hit you harder than a loosely aimed monster jammer ten miles away.

The long-term resolution of this issue is to require that individual air carrier aircraft and their systems be certified to a specific level of electromagnetic radiation tolerance, taking into account the various electonic toys that may be found in use in the main cabin. While this would cost some real money, it wouldn't have to be an extremely expensive or difficult procedure and would give a needed level of confidence in an area of growing "sensitivity". Wouldn't need to be done that often, either.

In the meantime, common sense does often work wonders.

Red Snake
2nd May 2003, 15:26
The mobile phone network operators don't want people using phones from planes either. On the ground, the handset can talk to only a few base stations which is normal operation & as the handset looses range of one base station, it is handed over to the next. In the air, the handset can talk & listen to literally hundreds of base stations. The network has no idea where the phone really is & the interference to & from all the base stations seriously reduces the capacity (i.e. revenue producing phone calls) the network can handle.

Pax Vobiscum
2nd May 2003, 18:30
I know I've said this before, but every commercial flight with more than a few dozen PAX is very likely to have an active mobile phone on board - most will have several. PAX can be silly, careless or forgetful and I'll happily lay a penny to a quid that sometimes flight deck and cabin crew can be too.

So, there are only two real possibilities:

(a) there isn't really a problem with handsets, it's just a scam to maximise the revenue from air phones; or

(b) active handsets pose a potential safety hazard on board an aircraft.

If (b) is true then we can never eliminate the possibility of an active phone on board by simply issuing instructions that all mobiles must be switched off (including those in the hold!). We either need a foolproof system of scanning for active phones (tricky because they can be 'quiet' for minutes at a time) or we need to 'harden' aircraft systems so this ceases to be a threat (with the obvious difficulty of retrofitting any required changes).

It's interesting that "Connexion by Boeing" offers Wireless LAN (802.11) operation inside aircraft, which has very similar power and frequency characteristics to mobile phones. Have these aircraft been suitably 'hardened'?

2nd May 2003, 18:37
It is not only the safety aspect from the aeroplane point of view. There is the legal stance from the telecommunications act (or whatever) in that it is illegal to use the mobile phone on the aircraft.

However, what I would like to really point out its that if you do insist (like 747FOCAL) on using the phone while in the air, don't be too surprised when your phone stops working. We all know that the VHF radio on the aircraft is line of sight, and the higher you get the more sight you get. The same for the mobile phone, except that it isn't designed to communicate with multiple base stations (which will occur), and the network may choose to shut down the channel, or the phone may be instructed to do opposing things by different base stations.

Ranting ends.

Red Snake
2nd May 2003, 18:53
WLAN (802.11b) is much lower output power than a mobile phone, 50mW vs. 2W. About 40 times lower.

CarltonBrowne the FO
2nd May 2003, 20:38
Occasionally during the taxi out, we overhear the characteristic rapid chirping of a mobile phone through our headsets. More often than not, it turns out to be a crew phone :O , we switch it off, then continue with no ill effects.
Sometimes, however, it becomes necessary to hold clear of the runway and make a PA reminding PAX to switch their phones off. At the very least, something back in the cabin is emitting enough of a signal to be picked up by the cockpit intercom. I think that once in a while I have observed deviations in some of the aircraft nav kit while the interference is going on, but it is possible I'm just being paranoid... :suspect:

2nd May 2003, 22:18
I have in the past, before the ban on mobiles in flight, used my phone to say goodbye to my girlfriend in climb after cleanup in the Classic 747. At no time did I observe any detrimental affects to flight instrumentation. Maybe its different in glass cockpits, I now comply with the rules as a pax but can not understand why one must not use mobiles untill disembarkation after engine shutdown? Far more powerful transmitters are being used every day by groundstaff which in fact used to run outflow valves shut in the classic. I was severly admonished once by a cabin purser for using my mobile after shutdown, waiting to disembark at the gate. His excuse was that refuelling had commenced and using my mobile presented an explosion hazard. What a load of c#ap. Little did he know that at the same time there were about three walkie talkies of ground personnel in full blast.:confused:

2nd May 2003, 22:52
747 FOCAL is right on target.
Have sat at the end of the runway with eight folks all using their cellphones at the same time...nothing unusual noticed.
'Course, this was with old Collins ARINC radios and steam gauges...glass 'might' be different. If so, then the aircraft manufacturers have a problem, which should have been solved at the factory, not by the airline operators.

In trim
2nd May 2003, 23:36
You only have to be standing in the flight deck on turnround to realise the effect......a second or so before a mobile starts ringing you get interference and crackling on the instruments / speakers.

747Focal - There is a big difference between the "thousands of signals" passing through the aircraft as you come in to land, compared with a cellphone in the forward lav....as indicated by another poster.

I've heard cellphones beeping/ringing as an aircraft is on final approach (and an embarrassed passenger who couldn't undo seatbelt to switch off said phone!). Could this have an impact if you were on a Cat IIIB approach? Probably not, but I'd rather not take the chance!

2nd May 2003, 23:37
Well I have been involved with an incident on a Dash 8 aircraft...the classic not the super Dash . During the cruise on a stormy night over water(I do not wish to elaborate on the route) we had an auto pilot disconnect (it may have been the yaw damper which caused this) and the detail is rather vague in my memory and also noted an OAT of -99C. I cannot now remember all the other items but checked with the cabin crew to see if any phones were on. The one crew members phone was on and once turned of all systems normal(coincidence). Ten minutes later approaching land failures returned. Cabin crew PA to pax and 7 phones in overhead lockers were turned off. Operations normal. A ferry flight to engineering base and no problems found on memory. Engineers agreed that the proximity of OAT prob to the overhead lockers and the times at which the problems arose(leaving the coast and then approaching) made phones the most likely cause. To the best of my knowledge this problem never returned.
Also mobil phones were responsible for false baggage fire warning causing numerous abandoned T/O and rapid relands. A different warning system is now in use and that A/C type now. :ok: :ok:

3rd May 2003, 00:13
HotDog: I now comply with the rules as a pax but can not understand why one must not use mobiles untill disembarkation after engine shutdown?Different airlines have different rules or levels of hysteria. BA for example lets you switch on at engine shutdown.

The funniest was QF's stance for a period. They used to be a particularly hysterical "switch off before boarding, switch on after disembarkation" airline. When they introduced their CityFlyer super-duper business service they allowed use of phones until doors closed, while maintaining the previous rule for all other flights. Crazy. They've brought the others into line with CityFlyer now.

I. M. Esperto
3rd May 2003, 01:52
This brings up a question I have had in my mind.

In the 9/11 aircraft that crashed in PA a Hostess made a cell phone call to someone, I think it was her mother, and described in detail what went on in the cabin during the hijacking. The conversation eventually became knows as "Lets Roll".

This was done at cruising altitude. The conspiracy buffs are having a time with this. According to many, the conversation would have been impossible, therefor fabricated.


Gertrude the Wombat
3rd May 2003, 03:24
I'm retraining to regain my PPL, and the one thing I've so far scrawled on the club checklist is "phone off", having forgotten to switch it off once and been spotted by the instructor when it started interfering with the radio.

DC Meatloaf
3rd May 2003, 03:31
Slightly OT, but the Beamer call in which he said "Let's roll" was actually to a GTE airphone operator, I believe.

There were other cell phone calls from highjacked planes that day, including Barbara Olson, wife of Solicitor General Ted Olson, who was on board Flight 77 which was crashed into the Pentagon.

CNN.com (http://www.cnn.com/2001/US/09/11/pentagon.olson/)

Faire d'income
3rd May 2003, 04:33
How many people have to tell you that they have seen errors, discrepancies, map shifts, comms interference etc before it clicks! The fact that most of us have been on board when an active mobile didn't cause an 'apparent' problem is irrelevant.

It's like smoking in the toilet. 999 times out of a 1000 it doesn't cause a problem but would you let passengers do it. There are millions of flights a year. Use your heads. The above posters who mentioned unexplained 'events' were either vigilant or lucky or both. It's the problem that isn't picked up that is the serious one. I have seen an FMCG go sufficiently crazy to initiate a thorough search of the cabin, while aborting an Atlantic
crossing was being seriously considered. A cd-rom was found in use, within seconds of it being shut down everything returned to normal.

Most investigations into this sort of event end with " unable to re-produce on the ground" type conclusions.( I.E. The manufacturer, airline and phone company don't want it on the record so conclude the pilots were dreaming and therefore safety was not compromised ). Any pilot who has had that feeling of " what the f*** is it doing now " and identified a source in the cabin will never be amused at the thought of such equipment on board.

The question should not be " Why can't we use them if there is no concrete evidence to say they are unsafe ".

Good aviation dictates that " They should not be used until we know they are safe! " :ok:

3rd May 2003, 06:15
IF, (and a very big IF) there is a problem with some designs, where are the certification authorities...I don't see any one of 'em standing up and saying...we goofed.

ANY design should be PROPERLY shielded against minimal RF interference from cellphones, CD-Roms etc...

WHO in the regulatory environment will take the heat?

Short answer...they all hide under rocks when the subject is discussed.

Have to ask, is this typically an Airboos 'problem' or are Boeing products implicated as well?:eek:

3rd May 2003, 08:18
A couple of points here:

1) The "New Kid" always gets blame for unexplained things that go wrong. So skepticism is appropriate, alongside caution. It may well be true that aircraft systems that can be tweaked by cellphones have more general defects, such as shielding and power and grounding problems, that also make them succeptible to other EMF radiation hazards found in the aerial environment.

2) 411A - I'm on the slow end of a long wire & thus hardput to check it, but suspect there's ample authority already in the FAR's, etc., and the many included standards to make a case for more comprehensive and recurrent EMI testing of critical systems. Can someone confirm or refute?

This class of problems doesn't yet seem to have a very organized constituency of support in government ...or outside. The fence sitters wait for a public atrocity/catastrophe to catalyze action. It might well be an area where pilots can accelerate a constructive result.

3rd May 2003, 11:21
quote From Hot Dog "same time there were about three walkie talkies of ground personnel in full blast"

Working in a ramp enviroment a few years ago all our hand helds had to be INTRINSICALLY SAFE.
This also was the case at our ESSO bulk plant. We were not supposed to use normal cell phones for reasons that were all to obvious, especially during tanker offloading operations.

I would hope that all operators of "walkie talkies" in such sensitive enviroments insure that they are INTRINSICALLY SAFE !!!

Can not say the same thing about cell phones.

stormin norman
3rd May 2003, 15:15
'Fact' 747 climbing out could not engage any of the 3
autopilots. Cabin crew made a PA to check and switch
off all mobiles.1 found on switched off ,all Auto pilots Ok.
Need any more proof 747 !

3rd May 2003, 17:39
No arguments about having phones switched off in flight.

QF, however, are still rabid about phones being switched on after shutdown. Recently, whilst Port Health and Immigration were on board due a cabin crew member thinking she had SARS, the rest of the crew were shouting at pax "turn that off" as they were delayed an hour on board (ground staff using phones at the time).
Fortunately the cabin crew member did not have SARS (Suspected Allergy, probably to Pax)!

3rd May 2003, 17:41
The problem is in several parts, really:

1. One cellphone may not cause a problem - but the effects of several of them can add

2. The immunity of aircraft systems is a variable, because the effectiveness of cable screening changes over time, depending on the flexure, abrasion and so on that the cables get with ordinary aircraft activities. There was an article in the IEEE Sectrum magazine a couple of years ago on this.

3. Aircraft immunities to radio frequency fields are surprisingly low, especially for older designs - the RAF Tornado is well known as being remarkably poor.

A French friend of mine who flies for fun and is a professional radio engineer (although he has CPL and IR) once flew a small two engine A/C across the Atlantic for a holiday in Canada. HF was fitted but not tested because of lack of time, and when an attempt was made to use it, the autopilot went mad on him. Since when he shares my total distrust of radio - although it's been my profession for nearly 40 years!

There was an interesting paper at an IERE conference some years back on the energy needed to set off a fuel explosion. There's also info in DEF STAN 74, and the energy requirements are rather more than you would think.

As a professional radio engineer, I go along with the 'mobile phone OFF' school of thought. Not that you can turn all passengers personal electronics off - pacemakers, for example!

3rd May 2003, 19:27
With regard to the questions about which licensing authority and manufacturers are taking a close look at this? I doubt that anyone will until there are dead people and it can be proved that they are dead due to a phone.

Since few are looking to trap and record details of phone interference, it will be more difficult to prove and so the loop will continue.

I really think that it is that dead simple. Present some dead people and a 'smoking' phone and there will be an investigation and much "we told you so".

One thought, does the FDR record the headphones? I appreciate that CVR is there for spoken and ambient sound but that would miss the highly distinctive sound of a mobile phone on the intercom.

Incidentally, I can confirm that the problem of trying to reproduce the problem on the ground is because - you are on the ground! See the point about mobiles communicating with dozens of base stations, as you ascend.

For my part - I always remonstrate with any fellow pax that I see with a phone on before permission is given. The fact that I have been in telecommunications for 23 years only increases my belief that interference is not just a noise on the intercom but that it affects instrumentation and control equipment in a random manner.

I urge all f/c that if you hear that sound - make a P/A as soon as you safely can. Obvious difficulties of pax then releasing belt to look in locker.

Perhaps carriers need to develop a procedure, that the f/c advise c/c of the prob and c/c make the p/a when appropriate. The p/a to be STERN, not just the usual pretty please.

3rd May 2003, 19:40
I left my mobile phone on during a flight once, This was due to a stupd error on my part.

The flight had no ill effects, In fact it was a beautiful day and a lovely smooth flight.

However, When I was walking through the arrivals hall and found out that I had left my phone on I felt very stupid and make sure that it is turned OFF whenever flying.

Now, Nothing happend during that flight (or nothing that I am aware of) but my mind went through a few 'what-if' scenarios.

Quite simply, We don't know what effect mobiles will have, I don't want to be responsibile for any problems on a flight because of my phone therefore I triple-check that it is OFF.


3rd May 2003, 22:17

<<ANY design should be PROPERLY shielded against minimal RF interference from cellphones, CD-Roms etc...>>
With your experience you should know that you cannot protect / test / certify against the unknown.

If there were only, say, 3 mobile types, then of course systems could be tested against them... But of course, there are new models, indeed types (e.g. 3G), coming onto the market each day.. and that's before we start on CD-ROMs etc., and all the accessories that go with them....

And of course most of today's airliners were designed, built and certified prior to the widespread use of mobiles.

Flying Spaniard
3rd May 2003, 22:40

i just read that
i think it is bullshit

3rd May 2003, 23:30
stormin norman

The incident you relate might be evidence but it's not proof.
Did you report it?

4th May 2003, 01:55
<<One cellphone may not cause a problem - but the effects of several of
them can add>>

True, but the problem is even more contrary than that. The use of only one
laptop can cause anomalies, but in a test flight Boeing had over 200 laptops
and an electronics store worth of hand-held electronic games and CD-players
all in simultaneous use. No anomalies.

<<ANY design should be PROPERLY shielded against minimal RF interference from
cellphones, CD-Roms etc...>>

The difficulty with intentional emitters is that whatever their operating
frequencies they can still emit in an aircraft's comm/nav bands. Antenna-based
systems are going to be susceptible to wayward signals. How do you shield
them against frequencies they are designed to receive?

<<WHO in the regulatory environment will take the heat?>>

FCC regs make one part of it very simple:
"When any aircraft leaves the ground, all cellular telephones on board
that aircraft must be turned off.''

As for non-intentionally emitting PEDs, FAR 91.21 makes it the responsibility
of operators to determine which PEDs cause interference and to prohibit
their use. Given the ever-changing supply of PEDs this seems sensible.

<<today's airliners were designed, built and certified prior to the
widespread use of mobiles.>>

Granted that human reliance on batteries is accelerating, the
problems were noticed with the first widespread PEDs, the mini
transistor radios that became available in the late 1950s.

5th May 2003, 08:32
In at least 2 developing countries, I have seen a high proportion of passengers making calls on their GSMs during descent. This appears to be a routine event and no attempt is made by CC to stop this behaviour.


5th May 2003, 17:17
Just to add complications......

Some years ago, I was involved in WLAN development. When we went for Type Approval in the US, we failed - because the brand new laptop we were using did not meet the FCC Part 15 requirements on emissions. The (Japanese) laptop manufacturer didn't want to know either.

The moral? Even a so called 'Type Approved' equipment may fail dismally on emissions if you look at a production model.

In EMC (Electro Magnetic Compatability) work, you look at two things: Emissions and Immunity. Lack of immunity cannot be safely ignored by adopting the attitude of "I'm not going to repair my roof, so you have to stop it raining": similarly, emissions must be minimised, and in many cases, that can only be done by switching off. Especially when the manufacturers of such things as portable broadcast radios insist on minimal requirements so that they can keep the price down - and FM broadcast radios are well able to cause trouble to VHF Nav and comms.

5th May 2003, 18:28
Flying Spaniard

Good to see such reasoned opinion.

5th May 2003, 20:23
Well put Radeng.

I've had some experience with designing and testing equipment to meet various EMC standards. It can be a bitch to sort out problems. I've even seen test equipment designed to be used by EMC test engineers fail to meet the standards claimed.

We would take our equipment down a salt mine so that we could be sure of a reasonably quiet background in which to carry out tests. I wonder where the airline industry take an aircraft for such tests?

5th May 2003, 20:46
One problem that airport "Security" increasingly create for pax is, instead of passing mobile phones through the x-ray in those little open containers, they sometimes without warning stuff them into any side pocket they find in your hand baggage, even if you have already put them into a container. Result: The phone then gets forgotten about, compared to being on your person, and can spend the flight up in the bins switched on.

Why do security do this?

CarltonBrowne the FO
5th May 2003, 21:24
Flying Spaniard: why is a serious attempt by a regulatory agency to investigate a potential problem "bullshit"? At least they're trying to carry out a proper scientific study, instead of relying on "probably ok" or an equally inappropriate "it's a problem because we say so."

5th May 2003, 22:22
I arrange and observe EMC/EMI tests on flightdecks as part of the supply of our Electronic Techlogs (which use GSM technology to leave TechLog, etc on ground).

Our systems will not be allowed to even trial if the basic flightdeck test is not successfully completed - and these tests cannot happen without our DDP (Data & Design Performance test) being in place.

Flightdeck tests involve doing transmissions with flightdeck fired-up with engines off, then repeated with all engines on idle.

Results are tested visually (by two engineers) and electronically by a PCMCIA card in the avionics bay. This is then removed and analysed.

Each new aircraft (and variant) that is added to the fleet needs to be tested.

Finally, to emphasise radeng's post, these tests are only valid for that build of computer/phone card combination. It is our responsibility to verify each build of all equipment used. The DDP only covers one type of build; new build = new DDP = new EMI/EMC test.

All tests on all a/c covered (typically 737s and A320s) have been completely clear of any interference - but that's only because of the effort that goes into making sure that's the case!

Many of the electronic equipment allowed on f/decks at the moment don't need to undergo these tests as 'flightbag'solutions are not considered to be an integral part of the operation of a commercial a/c. The TechLog is a vital part of operating procedures, hence different standards of test.


6th May 2003, 01:53
411A misses one vital point; a lot of systems and even aircraft still in regular daily use were developed BEFORE mobile phones, CDROMS, Laptops or other modern gizmos were even thought of. So it is fairly pointless to say it is a problem for the design authority or manufacturer as they had no knowledge of potentially disruptive technology at the time the unit was signed off! They did the best with available information at the time, and considering the amount of RF emissions in the ether these days, did a good job IMHO. I for one perfer to err on the side of caution, having seen some interesting AP effects on a Saratoga which seemed to be related to a powered-up PCS phone in the R/H pax bag. And yes I do normally ask that pax turn off any electronics as part of the pre-flight safety briefing.

6th May 2003, 08:30
I have personally had two cases of RF interference with the A/C systems. The first many moons ago approaching TOD for Man in a 737-200 and the A/P pitch channel dropped out. It was re-engaged, and a few seconds later dropped out again, with a momentary stickshake (It is supposed to disconnect on stickshake activation). Continued uneventfully to MAN. Sitting scratchiing heads as to how to write it up---enter the Engineer, whio takes one look at the beginning of the entry (A/P Problem) and says "What's that, a stickshake and pitch channel dropout? Third one this morning fellas, we reckon it's the military in North Wales testing radars or somesuch!" All were on 737-200's and would look like signal injection into the stall warning system.

The second was on a 744, Short Finals Singapore. I heard a very distinct series of dialing tones on my headset-(the F/O didn't) and all the #2 ILS & Nav. info blanked with associated flags and warnings. I happened to be on the PA at the time securing the cabin, so added a request for whoever was using the phone to desist. Nav info came back after about 30 sec. The Cabin Crew confirmed that a passenger was using a phone at the time, but they were secured, so unable to stop her.
These two incidents are enough to make me a believer!:ok:

6th May 2003, 16:09
There is a simple way of avoiding 99% of these occurences.
A good PA, either fromt the CC or the pilots.

When I first made Purser, I realised after 2 weeks/35 stretches that the standard company text about moblie phones was useless, since no pasengers ever checked their phones.
So I modified it to the following:
Ladies and gentlemen, your mobile phone on stand-by, even if you are NOT talking into it, WILL search for contact with a ground station. This continuing search CAN interfere with the navigational equipment in the cockpit. That is potentially dangerous. We don't want that, you don't want it, so please make sure that your moblie phone is switched off COMPLETELY!

For the benefit of the non-English speakers I hold up my own mobile,wave it around a bit and at the end of the sentence make the universal throat-slashing movement. :) And each & every stretch at least 2 or 3 pax get up and take out their phones from the overhead luggage bin to check/switch it off! :suspect:

I've proposed to change the standard non-funtional text, but comp not interested. Claiming that it is too much text and will bore the pax. Since I leave out most of the obfuscating commercial blah-blah, my text is actually much shorter than most Pursers', and the whole safety spiel always has people's attention, even the safety demo is watched with wry amusement and or alacrity.
I am satisfied that on "my" flights at least, the danger of this particular phone sh!t happening is well reduced. Added benefit is passengers who appreciate understanding why they have to do certain things.
They don't like being talked down to, the way we often do on-board. They are not kindergarten inmates, but will behave as such if we treat them condescendingly.
Passengers are just like humans, treat them with respect, appeal to their understanding and they actually enjoy playing an active role in the safety effort.

<end of ride on hobby horse>

6th May 2003, 16:28
FlapsForty - Good for you. As a passenger I'd be very happy to hear you say that.

BBC reports a Siemens airborne trial of 3G mobile equipment - sounds like they are so worried by the absence of demand for 3G on the ground that they want to use it in the sky instead.


6th May 2003, 17:10
I would like to support radeng’s comments about EMC. For products placed on the market in Europe there is a New Approach Directive numbered 89/336/EEC. This pertains to the limiting of emissions from and immunity of every, well almost every (with small exceptions), piece of electrical equipment, which is “Placed on the market” or “Taken into use” within the European Union.

Sounds OK in principle, BUT a couple of points to consider…….

The EMC Directive (89/336EEC) and the statutory instruments that enshrine this into law in member states DO NOT prescribe that the manufacturer makes ANY measurements; it just states that the product must comply with what are called the ‘Essential Protection Requirements’ of the said Directive. Now most manufacturers will make measurements in order to gain evidence that they have satisfied the principles of due diligence in their application of this Directive. But remember all the manufacturer has to do, as a minimum, is make a declaration that their product complies. These declarations are normally supplied with the product when sold and are the pieces of paper we all throw away when we open the box!

This principle is called manufacturer "Self - Declaration" and it does not have to be confirmed by any body independant of the manufacturer prior to the goods being available for sale and (ab)use in aircraft.

The second problem is that although the Directive does state that ALL products must comply i.e. each and every product that comes of the line; in manufacturing, however, there are always tolerances. Commercialism being what it is means that the design of the product is such that the measurements are made and results accepted right up to the limit without any thought of measurement uncertainty. This ensures that the bill of materials and component count remains as low as possible and the profits as high as possible. The reason this is important is that if you want to reduce the ‘level of emission’ this might mean the inclusion of an extra component (capacitor, choke, screen, bonding, can etc) not a problem in small production run, but if you make a million products week as some mobile phone manufacturers do, then this extra component is going to cost you maybe $100K a week (assuming the extra component costs only 10 cents).

The reason I thought was worthwhile posting is because there almost certainly WILL be some samples of the product run that FAIL these protection requirements. The police(ing) of the EMC directive is in Europe at best patchy, in some areas even relying on competitors measuring each other’s products in order to gain commercial advantage by forcing withdrawal of sale.

In my view this means two things

a) There most definitely ARE samples of products out there that fail to meet limits prescribed in the technical standards supporting the statutory legal instruments. I have quoted the example of the EMC directive but the principles apply equally to CFR 47 – FCC Rules parts 15, 18, 22, 24, Industry Canada regulations, JATE/TELEC, AUS/NZ, 3GPP specifications or whatever region of the world or technology sector you care to mention.

b) Be aware that when using the term ‘regulation’ in the context of commercial products the reasons for regulation are different i.e. in the world of aviation the primary drive for EMC regulation may be that of safety, in the commercial world the primary drive for EMC regulation may NOT be. There are two reasons why the EMC Directive, 89/336/EEC was brought in Europe in 1996. Firstly, to provide free passage of goods throughout Europe and ONLY secondly to try to minimize ElectroMagnetic pollution. Furthermore, equipment is said to be fit for purpose IN IT’S INTENDED ENVIRONMENT. The intended environment for mobile phones for example is not in an aircraft and therefore the limits in the standards are not designed with aircraft operations is mind.

Sorry if this is a boring post but there is a good reason. The reason is that someone once said to me that there is a perception amongst PPLs that there is an ATCO out there clearing the skies for me. I know this is not true. Commanders and F/Os don’t think there is a heavy weight regulatory body out there with the primary objective of making sure that all products are compatible and that they will not interfere with your aircraft systems……..there is no such beast. Assume all products fail and all possibilities of interference exist in your aircraft.




P.S. Just as an after thought the above only applies to unintentional radiation and does not cover intentional radiation e.g. Code Division/Frequency Modulation/Gaussian Minimum Shift Keying type intentional signals mentioned above that are used in cell phones. The fact that a particular phone does not interfere can be because the type of modulation involved does not interfere, the frequency is not related/inter-related with aircraft systems, positioning in the cabin, power output of the transmitter etc etc etc. All these factors are not controlled by either of the pilots. Permitting this at perhaps 300ft AGL at 200 kts is a sailing a little close to the wind I would say :eek: :uhoh:

6th May 2003, 23:37
Perhaps there is another safety aspect: that of the passenger making the call.

Despite all the publicity and griping large numbers of people are still incapable of speaking into a mobile phone at a normal volume: they have to shout.

Aircraft are noisy inside: maybe not as loud as a train but more or less constant background white noise. At least on a train you can get up and walk around or lean out of the way. Being stacked for 40 minutes over London and having someone blathering away about what he did/will do in Amsterdam with whom will drive even the calmest person insane.

And then there's the ring tones. Can you imagine trying to sleep on a long haul flight, say LHR <-> HKG, and having that ghastly Nokia tune going every few minutes? At the Nokia default volume of too-bloody-loud? Bad enough down the front - imagine what it's like in cattle class where your head is sandwiched between up to 10 people.

Now add a few beers into the mix....

Incidentally, anybody know how much you could be stung for in roaming charges on a flight from UK to Australia? That's a lot of networks to connect to.....

7th May 2003, 05:21
From the ATC point of view if I may.......

Was the witness first hand a couple of years ago Down Under. A certain ATC Assistant who was flying during the many hours he was working outside Air Services Australia, used to walk about the old Brisbane AACC with his phone on. On walking past a radar screen once (it was the old IRDS RAS/RIS screen on the Approach Team...) it went all "Scooby Doo" in front of everybody. At the time, it was kind of a laugh. But a few day later, the signs went up around about the centre, instructing people to turn phones off.

IMHO, nobody is that important they need to be "contactable"!. And if you think you do.....well, let it not be up to me to judge.


7th May 2003, 15:48
Having just had a brief read of the report, I think that this represents an excellent start to a full investigation. The boundaries of this particular report are narrow for practical measurement reasons and I feel that they have only really scratched the surface insofar as.......

1. Only a single frequency per band was used for each measurement. In reality many frequencies are used in each band in mobile communications and the affect of changing the frequency can be marked and dependant on the unintentional "Q" of the reception mechanism within the avionics. This means how easy the system will respond to an interfering frequency and how accurate the accidental tuning has to be. The higher the "Q" the lower the "chances" of interferences, but when the tuning is on target the worse the interference possibilities.

2. Only single frequency simplex has been simulated and in real life half or full duplex possibilities are involved.

3. Only circuit switching on single timeslot transmission has been simulated. Present and future communications protocols are/will be using multi-slot and packet switching techniques.

4. The field strengths do represent that which would be expected at 30cm from the source, but this level of field strength increases remarkably as the source is brought closer to the victim (i.e. the phone is brought closer to the avionics). This can be as a square or cube law relationship depending on the distance and the interfering frequency and the interfering mechanism either low impedance current flowing through the cable or high impedance voltage presented across two points in the control circuits presenting an interfering potential difference

3. Lastly and probably most importantly is that the measurements have been necessarily restricted to Gaussian Min Shift Keying (i.e. GSM). There are other widely used schemes in different areas of the world.

Code Division Multiple Access (CDMA) - US
Wide Band Code Division Multiple Access (WCDMA/3G/UTRA/CDMA2000)
TDMA - Time Division Multiple Access - US
TACS - South America/China/Middle East etc
PDC - Japan

Again probably boring and techy BUT my point is that even with the sub-set of possible interferences mechanisms that this report has focused on the measurements and the report still give supporting evidence of interference effects.......I wonder what happens in the real world!

In summary, IMHO we should keep mobile phones switched off during all phases of flight as there are currently too many unknowns and variables to make a proper scientific judgement

Cheers Andy


Captain Stable
7th May 2003, 17:35
Some excellent points being made here. In particular, Flaps' on-board PA is excellent. The PA system should be used for safety briefings and only safety briefings. There is no place for "If you would like to book a hire car, we suggest you go to Fred's in the arrivals hall - or if you need a hotel we've arranged special rates with the XYZ Hotel..." which just tend to persuade the passengers to blank it all out. I want to be sure that pax sit up and listen when it comes on.

Those of the pro-phone lobby who rest their claims on "Well, I've flown x thousands of hours with my mobile phone on and I haven't had a problem" do not assist the argument, in that it does not establish that other people haven't had problems.

What does anyone think of the suggestion that I've seen elsewhere that mobile phones should be switched off before boarding? It is quite possible to install archway detectors that will scan a passenger as he goes through.

Since in LVP's, aircraft rely quite considerably on the avionics to navigate successfully to the end of the (hopefully) correct runway, how would people feel about having mobile phone use permitted before takeoff?

I feel that the CAA paper is a very welcome starting point. I suggest that ICAO should be involved in this, so that a set of rules that is coherent across airlines and national boundaries should be encoded.

7th May 2003, 17:53
Fortunately, immunity is being recognised as being important, although it has been said that it will be several years before all civil aircraft reach an immunity level of 20Volts/metre. The International Electrotechnical Committee recommend an immunity level of 3V/m for domestic and light industrial environments: 10V/m is used for maritime electronics. Domestic radio and TV sets only need to meet 1.8V/m, while normal telephone manufacturers have been pressing for no limits at all on telephones! Tough for anyone living near a broadcast station. many years ago now, the microphones in the telephones at Manchester airport were replaced by the then new 'electret' ones: the result was that everyone telephoning had a strong background of Manchester ATC! So much for the telephone manufacturers arguments!

Radiation is another matter: even without cell phones, the current proposals on Power Line Telecommunications, connecting your computer via the power network are likely to mean that a lot of HF radio becomes unuseable. Because of the number of radiators involved, that's quite likely to mean that HF from mid Atlantic won't make it - hopefully, all aircraft will be using (more expensive) satellite comms by then........

Pax Vobiscum
8th May 2003, 21:27
Interesting radeng. The first major trial (http://www.theregister.co.uk/content/22/30567.html) in the UK of broadband over power lines is taking place in Winchester - handy for Swanwick!

Iron City
8th May 2003, 22:21
radeng: I though the ITU spectrum rules (as well as regional and national ones) stated tha tcertain services, for example aeronautical mobile communications, were allocated certain frequencies and anyone who did things (like communications over power lines) that resulted in emissions that interfered with the service had to change their way of doing things so as to not interfere or knock it off.

In the real world I know it is never this clean or simple, but even ITU should recognize that this kind of interference is a problem. Then again, maybe they want to push everybody to satcom and cell phones so "service providers" can charge by the minute, bit or whatever.

engineless john
8th May 2003, 23:26
While I've no experience of avionics, I do work for a major mobile phone manufacturer as an RF design engineer, working on handsets.

The reason I'm posting is to second Radeng, and Andy. To the anecdotal tales of "well I've used my phone in an airliner and never had a problem", I'd say "Yet!".

Part of the problem is that with a metal box the signal from the phone or CDrom or whatever gets reflected around creating peaks and troughs of signal. If you get constructive interference at the wrong point energy will get conducted onto wiring looms etc. So a small change in the position of the radiating object can create large changes to effect on other equipment. And as such it is going to be difficult to test in a lab/EMC house environment.

In addition because basestations tend to beam the signals they produce horizontally rather than vertically, a phone in an aeroplane will spend a lot of time trying to camp onto a network. As a phone tries to camp on it broadcasts to the basestation to try and register. Therefore lots of potential for interference...

I've seen phones interfere with other phones, PCs, televisions, and radios, and spent months of my life trying to shield and screen things. To my mind it's just not worth the risk of switching a phone on in a plane. It is as simple as that.


Max Continuous
9th May 2003, 01:15
Well said SSC. Use of the mobile phone is a highly anti-social behaviour in close proximity to strangers and can be banned on those grounds alone without reference to the safety arguments.
As far as risk management goes, someone mentioned the dangers of smoking in aircraft toilets as being equivalent to using a mobile. Surely it can't be beyond the wonders of modern technology to provide "safe booths" on larger aircraft where passengers can make calls and smoke to their hearts content under the watchful eye of the cabin staff. This would satisfy consumer demand and stop the problems being driven underground.
I readily admit to leaving my mobile accidentally switched on in the flight deck "da da da...da da da...da da da" so there must be dozens of passengers doing the same thing. I always permit passengers to use mobiles on the ground in cases of delay or unusual circumstances etc.

9th May 2003, 22:24
Iron City,

The ITU are unfortunately always way behind in these matters. In fact, ITU workings are a bit like elephants mating - a lot of trumpeting and noise and then nothing happens for a couple of years. (Radeng goes to some ITU meetings, for his sins).
Currently, the FCC is investigating PLC (Power Line Communications) with a view to its interference potentials. The matter was brought up in the UK some time ago: Tony Blair's desire for 'Broadband Britain' meant that when there was a Cabinet committee meeting, the civil servants who realised that opposing the proposals would be bad for promotion rolled over with their feet in the air. NATO and the armed forces are worried about it - they are big users of HF, even in these days of military satellites: people from the UK Radiocommunications Agency, bless them, are fighting as hard as they can to keep the radio spectrum clean, but I understand that most other UK government departments would rather not rock the boat.

The European Commission also want PLC, and have various specious arguments about the users of HF being a minority. There have been mutterings about a Human Rights case, in that ethnic minorities in the EU wishing to receive broadcasts from their native countries that aren't available by satellite would have their Human Rights infringed. Whether that will get anywhere I don't know - I doubt it.

But using satellite is a good way to improve the satellite comms people's profits!