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Mobile Phones on Aircraft CAA Report

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Mobile Phones on Aircraft CAA Report

Old 2nd May 2003, 00:25
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Mobile Phones on Aircraft CAA Report

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:

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

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

[email protected]
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Old 2nd May 2003, 03:31
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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.

Old 2nd May 2003, 03:59
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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.
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Old 2nd May 2003, 04:56
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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
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Old 2nd May 2003, 05:47
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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)
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Old 2nd May 2003, 14:41
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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.

Last edited by arcniz; 2nd May 2003 at 14:51.
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Old 2nd May 2003, 15:26
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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.
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Old 2nd May 2003, 18:30
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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'?
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Old 2nd May 2003, 18:37
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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.
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Old 2nd May 2003, 18:53
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WLAN (802.11b) is much lower output power than a mobile phone, 50mW vs. 2W. About 40 times lower.
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Old 2nd May 2003, 20:38
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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 , 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...
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Old 2nd May 2003, 22:18
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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.
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Old 2nd May 2003, 22:52
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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.
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Old 2nd May 2003, 23:36
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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!
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Old 2nd May 2003, 23:37
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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.
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Old 3rd May 2003, 00:13
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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.
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Old 3rd May 2003, 01:52
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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.

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Old 3rd May 2003, 03:24
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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.
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