Mobile phones

[Mike Southern]

Not a pilot, but a frequent pax; Following on from the probs yesterday at LHR I was a) fortunate to get home at all from AMS, but b) stacked over London for over an hour and then trundled off to the @rse end of LHR while we waited 40 minutes for a gate to become free. This thread is not a whinge about the delays, but a question regardin mobs and aircraft 'systems'

During the majority of the time we were sitting waiting for a gate the engines were running and there were frequent announcements to try and stop some of the sh!theads (who think they know better than everyone else, or are simply far more important than the likes of me) from making calls on their mobs... I can understand the desire to let people know what is happening, but did they put anything at risk?

What is it about mobs that means they shouldn't be used once the aircraft is up'n'running? I cannot imagine that they transmit on a similar frequency to the aircraft comms systems otherwise you would have the problem anytime you were in range of ewither a mob or a TX station, so what is is?

[ModernDinosaur]

Have you ever placed your mobile phone next to, say, the speakers on your PC, or your bedside clock-radio? Ever heard the "yada-yada-yada" noise just before the phone rings? Well, I guarantee you that your computers speakers don't even have a specific "frequency", yet somehow the mobile phone interacts with them, doesn't it?

Now imagine the emergency exit slides on the aircraft, or the fire-detection system, or the generator control unit, or the fuel control unit, or the... Do you really want to be turfed out of your nice warm aeroplane onto the cold tarmac of the apron just because that phonecall was so very important that it caused an evacuation? I won't even consider the effect the phone might have in flight on the autopilot, the navigation system, the pressurisation system, ...

As to why the mobile is the guilty party not the ground station, well, it's all a matter of distance. Double the distance from the source of the interference and you've quartered (inverse square law) the effect. The mobile phone mast is at least a kilometre away. The mobile phone itself might be fifteen centimetres from the cable buried in the sidewall of the aircraft. Need I say more?

I only fly light aircraft, but I have forgotten to switch off my mobile once. It rang in the baggage compartment of the plane, and the GPS wandered off by about 15 miles. Fortunately I'm only a private pilot so I fly by looking out of the windows - but what if I'd been on an airliner relying on my navigation equipment while flying in cloud?

Fly safe - switch the mobile off, and keep it off until you're in the terminal building.

MD.

[Intruder]

Dino,

I certainly agree with your reasoning regarding airborne use, especially in smaller airplanes where the phone may be VERY close to nav and/or comm antennae.

However, I think the RF interference issue with escape slides, etc is a red herring. Most emergency systems use mechanical actuating devices (pull a pin from a CO2 cartridge) which are not affected in any way by RF. Also, the lower-level systems such as generator and fuel controls are certified to a high degree of RF protection -- well above what may be generated by a cell phone.

Also, I have been in similar "gate hold" situations where the Captain has specifically made announcements telling the SLF they could use their cell phones while in the holding pen, then asking them to turn off the phones when he began the taxi to the gate. I believe that is the best option, as long as the Captain is comfortable that the phones will not interfere with his ability to hear the ground controller...

[nitro rig driver]

lets be honest-WE JUST DON/T KNOW what a phone can do to our all singing and dancing fly-by-wire aircraft
you can/t just say
-well it might be alright but ???
always better tobe on the safe side and turn the bloody things off
its the only place we can get away from them anyway

[AntiCrash]

There have been cases where landing aircraft have had to go around because the ILS was jinxed by mobile phones. Not what you would call a good gamble when there are folks lives at stake.

A second issue is, in the U.S. our Customs Service takes a dim view of uncleared pax communicating with who knows who, telling them you know what, is you know where. If you know what I mean? :O

[Mad (Flt) Scientist]

I understand that a serious EIS issue with SAS for Q400 (nee dash8-400) was passenger phones in baggage hold ringing, causing spurious fire warnings (or similar) through EMI.

It's not a trivial issue.

[Elliot Moose]

The same problem did (does) exist with the CRJ family. More than one earlier model was evacuated due to somebody making calls too close to the baggage compartment. The problem has been fixed, but who knows whether a given aircraft will have such a reaction?

In my opinion, people are stupid. People forced into large groups very quickly become lemmings, and will follow the lead of one mindlessly. I think it's just plain safer and easier for all if everybody says "no phones once the doors are closed" for all aircraft and leave it at that. Yes it may not hurt some aircraft on the ground, and the Capt may say "go ahead" during a long gate hold with no danger. The problem is when he has to say "eveybody stop", or when the next Capt determines that an entirely different aircraft shouldn't allow phones even on the ramp. The inevitable response from the pax will be "But last week I was told okay on the ground by Capt'n Bob on Air fifty five and seven eigths, so obviously you're just being an ignorant meanie!" Then the inevitable fight develops and all the other pax say "Yeah, I don't believe the phone can hurt anything because I read Physics for Dummies while drinking beer last year and I'm an expert". :rolleyes:

Can you see where this is going? Let's just leave the phones off and the seatbelts on now shall we?

[CI300]

Its only a nav issue. There is no technical reason for not useing a cell phone in an aircraft, on the ground, in the situation described. End of story.

[bookworm]

A CAA report (http://www.caa.co.uk/docs/50/Gsm_intf.pdf) gives the results of some experimental tests on interference from mobile phones.

The conclusion seems to be that GSM phones can interfere with some older equipment, but are very unlikely to interfere with more modern equipment with vastly better immunity standards.

[Intruder]

CI300:

Why is it that the nav systems (VOR is just under 118 MHz) are "technical[ly]" affected, and the comm systems just over 118 MHz, sometimes using the same receivers, are "technical[ly]" immune?

[jungly]

During pre-flight prep the captains mobile rang...causing a spurious ECAM caution and his ND (Nav display) to flash erratically...........

[Dragon Knight]

"Its only a nav issue. There is no technical reason for not useing a cell phone in an aircraft, on the ground, in the situation described. End of story."

What about a Engine fire Warning, or Cargo hold Fire Warning on the ground caused by mobil phone ? ? ? ?

If there is risk of fire, a evacuation will be performed resulting in a fine ride on the avac. slides ! ! ! , and someone allways get hurt.

Besides, if passengers have been told not to, it is a breach of existing law, you are as a passenger supposed to do what you are told to do, and told not to do ! ! ! ! ! ! ! ! !

So do what you are told to do, or I will handcuff you, and deliver you to the local police. ( just kidding ! ! ):O , but it is an option.

[QAVION]

"Its only a nav issue. There is no technical reason for not useing a cell phone in an aircraft, on the ground, in the situation described. End of story."

I have to agree with the previous four posters...

Even faulty aircraft inflight entertainment systems can cause flap warning messages on some aircraft (and they are designed to cause minimal interference). I've also seen my (company approved) walkie talkie opening and closing the pressurization outflow valves.

With aircraft departing.... If the mobile phone-using, Gameboy-playing, laptop-using pax want to wait even longer on the ground whilst the engineers perform maintenance tests on systems affected by mobiles, fine, but otherwise...

In the case of an aircraft taxying to the gate, the mobile phone users may not be inconvenienced, but the airline staff and the pax going out on the next flight may be.

Rgds.
Q.

P.S. I suspect the phones would be transmitting at their highest power levels in an aircraft, due to the metal fuselage shielding the signals. The pax may be frying their brains as well as inconveniencing themselves and others (but that's another contentious issue :p ).

[Self Loading Freight]

We keep having this discussion...

In the end, it will be impracticable to ban the use of mobile phones on aircraft, if it's not so already.

First, it doesn't happen. Lufthansa has said that there is at least one phone left on during every flight they make, and I doubt this is true for just that one carrier. I'm meticulous about turning my phone off in the departure lounge before boarding, but sometimes there's a rush or a last minute gate change or... well, twice I've got off at the other end and gone to turn my mobile on, and it had been on all the time.

Second, what's a mobile phone? I play with a lot of gadgets and see a whole lot more (tough job, etc), and recently I've seen personal organisers with GPRS, GPS, Bluetooth, 802.11b or any combination of the above. All are banned in flight, all are integrated with the main device and can be disabled with more or less fiddling with the software... but not everyone's going to know how to do this, or be fully aware of what's going on in their latest toy. Can cabin crew be expected to ensure that a device is in a safe state?

Third, the carriers themselves are moving away from the 'no transmitters' rule. Lufthansa (again!) is testing a passenger wireless network linked to the Internet, Britannia has wireless laptops for the cabin crew, and Virgin (at least) is looking at having an in-cabin mobile phone base station that will let passengers make calls via their mobiles and the satellite network.

Fourth, the future is going to be more wireless. I know of at least four new standards coming into use over the next couple of years, each with its own raison d'etre and each going into a new sort of gadget as well as the current sorts.

There are only two ways to proceed, given you can't expect passengers or cabin crew to be able to comply or enforce a 'no transmitters' rule. Either you accept it as part of the aviation environment, design and test systems and train accordingly, or you start fitting wide-band radio transmission detectors to each seat, much like smoke detectors in the lavs.

At the moment, it may be statistically sensible to keep the ban and assume that enough people will follow it to substantially reduce the chances of some nasty interaction, but I don't think it's sustainable.

R

[Blacksheep]

All these arguments go on forever, and the 'experts' have had their say, but at the end of the day its forbidden by law, written into the regulations in black and white - "...no person shall use or permit to be used, any portable electronic device that..." Blah, blah, blah...

End of story - bring out the handcuffs.

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Through difficulties to the cinema

[aardvark2zz]

There seems to be a lot of good points posted earlier and many not so good as usual; most likely old wives tales. Having worked for a major airline in field of interference I do believe I have some knowledge. The problems with cell phones are (note: I am not going to cover ALL different types of radios such as GSM, CDMA, TDMA, 900, 1800, 2400 MHz, 0.6W, 0.01W, altitude, plane type, etc., just TYPICAL situations), (IN BRIEF !!!):
- The almost perfect metal tube for keeping the RF signal within the cabin. This means that the cell phone radiation of 0.6 Watts will mostly bounce around the cabin until it is absorbed or radiated outside. One way to unintentionally guide the radiation is through cabin wiring, especially unshielded, but even shielded wiring can "guide" EMI into the electronics bay along the outer shield !!
- Also the cell phones would transmit at almost full power to overcome getting the signal through the small windows.
- On a 400 passenger plane if 25% are using their cell phones that'll make 60 Watts of total power bouncing around the cabin. Human flesh does absorb EMI but not enough. In the "tube"/cabin you have this power bouncing back and forth until it finally gets absorbed. The power keeps adding up UNTIL it is absorbed (leaked) somewhere by something. The choices are: windows, people, seats, wiring, etc... So in a cabin you could conceivably have, in an extreme case, an effective power level of almost 500 watts (albiet not sustainable). The solution would be to add absorber material all over the cabin or use very few phones.
- At the airline I was at, the cabin pressure would decrease every time they would transmit on the high power HF over the oceans. It was latter found to be a leaking coaxial cable leaking some of the high wattage HF which was absorbed by the newest fine electronics pressure regulator that was not properly designed for a high EMI radiation environment.
- The problem with using a cell phone at high altitude is that the atmospheric losses are sooo low that a cell phone can be used for many miles (approx. less than 50 miles). If the plane is flying near a city like New York you could theoretically interfere with many many cell sites on that frequency, especially during peak periods. Try this out. Go to the top of a mountain or building near a city but away from nearby cell antennae and see how long your phone call lasts during peak period before it gets dropped. Where I live near the top of a mountain the nearby cell tower is designed to limit the power on the mountain. I have better call reliability at sea level than on the mountain near the city.
- I have used a cell phone on a C172 and the cell operator came on line and from the background noise guessed that I was using a cell phone from high above and killed my phone call even though I was calling for aviation purposes. The operator had the kindness of telling me just beforehand.
As for electronic low power devices like games the power levels are much lower. Laptops emit more power. The problem is that if most people use laptops, especially on distant final approach, the TOTAL interference can be a challenge to shield from the weak navigation signals. Future airplanes are being designed accordingly but it will take a ling time before the old ones are replaced or retrofitted in the far future. If a pilot keeps complaining about the interference I would strongly suspect the problem is no longer with the computer users but rather the airline maintenance cost cutting.

Enough for now
Keep the blue side up (wherever up is )

[Blacksheep]

An excellent explanation of why FAR 91.21 prohibits the use of any device that intentionally radiates electromagnetic energy (e.g. moblile telephones etc.) in aircraft, at all times, unless testing has been conducted to ascertain its safe use. JARs include a similar prohibition. Note that for anyone wishing to use such a device, the onus is on them to prove that it is safe to do so, not the other way round.

So far, all available test results indicate that transmitting RF energy inside a metal tube, causes localised concentrations of energy that have adverse effects on other electronic equipment located within the same metal tube. Despite these findings, we will no doubt continue to be plagued by smart alecs who know better than the research scientists - as a group, mobile phone users aren't noted for their interest in anyone else's welfare.

The only answer to those who claim that the ban is senseless and insist on using their phones anyway, is to enforce the regulations and prosecute those who refuse to respect the safety of others. There are plenty of Aircraft Commanders lurking around here, lets hope they will do their duty in future.

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Through difficulties to the cinema