Author Topic: Please switch off all electronic equipment....  (Read 8885 times)

Wonky

  • Not exactly straight or narrow
Please switch off all electronic equipment....
« Reply #50 on: December 15, 2011, 06:30:44 pm »


Well, we come back to the fact that planes do not often fall out of the sky (without identifiable causes) and when you take that fact into account along with what I said earlier, that it cannot be a problem.

Passenger gadgets are not going to make a plane fall out of the sky.
But, if you study accident and incident investigations, you will see that it is very rarely a single failure that leads to the incident. In the vast majority of accidents it is a combination of failures, including physical failure, hidden system issues, training, unfamiliarity etc.

As stated by myself and one other "in the trade" on this thread, we have experienced interference from electronic devices on aircraft. This interference will not bring down an aircraft, but, in an emergency situation, it could be the final "slice of the swiss cheese" (google "swiss cheese model") that makes the difference between life and death.

In the aircraft industry, we are devoted to ensuring the safety of our aircraft, passengers and crew. We have identified a safety issue, and take steps to eliminate the risk.

An accident permanently scars the victims, their families and the airline employees. For people to disregard safety instructions based on uneducated arrogance, for short term satisfaction is abhorrent.

Re: Please switch off all electronic equipment....
« Reply #51 on: December 15, 2011, 06:39:21 pm »
EMC (Electromagnetic Compatibility) is a black art at best.  They put a shitload of effort into ensuring that the electronics systems on board aircraft don't cause mutual interference, but even then, you can't test every single possible combination.

Whilst it's extremely unlikely that someone's Gameboy or iPhone is going to cause problems, it could happen if just the wrong set of circumstances occured, so they err on the side of paranoia, and as others have said, take of and landing are the riskiest parts of flights (most incidents happen at these points) and you don't need any additional risks or complications that can be minimised by requesting that people turn all this kit off.  Theoretically a digital watch could cause problems, but (i) it's very extremely unlikely & (ii) almost impossible for most people to turn their watches off.  There has to be a reasonable compromise between safety and realistic operations, so the odd phone not being turned off is unlikely to cause problems, which is why they don't go around the cabin checking every single device (and if nothing else it would take an hour or two to do that!)

Transmitters are far more likely to cause EMC issues than conventional non-RF devices, because they intentionally radiate the sort of thing that causes EMC problems otherwise.  Now, it's generally in a very limited bandwidth, but at a much high power, so it's hard to predict whether it will cause problems, but it's best avoided.  As has been noted, it's relatively easy to hear the GSM handshaking when people have mobile phones near audio cabling.  I've heard it several times on the TV when someone has a phone in their pocket when being interviewed, and it couples onto the microphone.

Another issue with mobile phones, is that at moderate altitudes over build up areas, they can "see" many more base stations than they can when there on the ground, so there is the potential that when a phone beacons, searching for a base station, many will respond, and this could interfere with the mobile phone system, if people routinely left phone transmitters powered on during flights.

Getting up and walking around before the engines have actually stopped on the ground, is a bad idea, because as has been said, you can get sudden movements (some unintentional, caused by the engines in effect surging), and you can easily injure yourself in those circumstances.  Probably not fatally, but badly enugh that you won't be walking around unaided for a while.  For the sake of at best a few seconds extra delay (and probably none), it's a very good idea to stay seated when told to.

(Note, I'm an engineer who has worked in areas of EMC and the aerospace industry for most of the last twenty years, so I have a vague idea what I'm talking about!)
Actually, it is rocket science.
 

Re: Please switch off all electronic equipment....
« Reply #52 on: December 15, 2011, 07:07:38 pm »
Slightly OT, but bear with me. How likely is the following to be true?

A few years ago I went to China, one of the bods I was travelling with had inadvertently left his mobile switched on during the two flights it took us to reach our destination.
On arrival, and ritual switching on of phones, he claimed his phone (which hadn't been turned off) was offering him a 'choice' of 67 (or something like that - a opposed to the usual 2 or 3) networks whose areas (presumably) we'd overflown.
I've deliberately put the word 'choice' in inverted commas as I don't for one minute think he would've been able to select say, a Turkish network when we were in China.

I guess my question is would a mobile that had been left on during flight, actually store the signatures (if that's what they're called) of the networks we'd overflown?

Or was Stuart just a lying b@st@rd?

Adam

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Re: Please switch off all electronic equipment....
« Reply #53 on: December 15, 2011, 07:09:43 pm »
Another issue with mobile phones, is that at moderate altitudes over build up areas, they can "see" many more base stations than they can when there on the ground, so there is the potential that when a phone beacons, searching for a base station, many will respond, and this could interfere with the mobile phone system, if people routinely left phone transmitters powered on during flights.

That was always the argument the CAA used to give against the use of mobile phones in flight.

I can remember about 20 years ago in a Kingair we were flying across to Antwerp, the captain making the comment that his work phone, when simply left switched on, interfered with the VOR navigation, offsetting the signal slightly.  However his personal phone didn't do this.  It was probably pre digital network stuff.
“Life is like riding a bicycle. To keep your balance you must keep moving.” -Albert Einstein

Adam

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Re: Please switch off all electronic equipment....
« Reply #54 on: December 15, 2011, 07:11:49 pm »
Slightly OT, but bear with me. How likely is the following to be true?

A few years ago I went to China, one of the bods I was travelling with had inadvertently left his mobile switched on during the two flights it took us to reach our destination.
On arrival, and ritual switching on of phones, he claimed his phone (which hadn't been turned off) was offering him a 'choice' of 67 (or something like that - a opposed to the usual 2 or 3) networks whose areas (presumably) we'd overflown.
I've deliberately put the word 'choice' in inverted commas as I don't for one minute think he would've been able to select say, a Turkish network when we were in China.

I guess my question is would a mobile that had been left on during flight, actually store the signatures (if that's what they're called) of the networks we'd overflown?

Or was Stuart a lying b@st@rd?

Dunno - I guess it would depend on the phone as to whether or not it stores the names of the networks it's recently come across.

I know when I've gone across to France on the ferry, part way across the Channel, all of a sudden the French networks pop up as being available (about 4 from memory).
“Life is like riding a bicycle. To keep your balance you must keep moving.” -Albert Einstein

Re: Please switch off all electronic equipment....
« Reply #55 on: December 15, 2011, 07:19:07 pm »
I don't really care when individual actions are a risk only to the individual. However, I get really pissed off when somebody is arrogant and selfish enough to think that they know best and thus to potentially put my life at risk.

For people to disregard safety instructions based on uneducated arrogance, for short term satisfaction is abhorrent.

What they said!

Re: Please switch off all electronic equipment....
« Reply #56 on: December 15, 2011, 08:32:09 pm »
The first time I had two phones with me when travelling, I forgot about the second and didn't switch it off.  Thankfully nothing happened, but I do normally do as I'm told.

What I haven't managed to figure out is why they make me switch my poor little ipod off-it has no sending or receiving capacity.  I'm mildly phobic about flying but due to family commitments have to board an airplane at least 4 times a year.  My biggest problem is take-off and landing, so having my meditation on my ipod would be really helpful.  They didn't make us turn our Walkmans off when we lived in the USA, it's much more recent than that...

It's not a huge deal, but I wish I didn't have to.



Wonky

  • Not exactly straight or narrow
Please switch off all electronic equipment....
« Reply #57 on: December 15, 2011, 09:03:11 pm »
Watch <a href="http://www.youtube.com/v/XIaovi1JWyY&rel=1" target="_blank">http://www.youtube.com/v/XIaovi1JWyY&rel=1</a>

Now imagine that you didn't know that it was happening, the aircraft is on fire, and at a funny angle. Everyone on board will be in headless chicken mode, not pre-primed volunteers.

Having not heard the emergency announcements because you were listening to your diepod, you are now trying to escape with a dangly chord attached to your head and pocket.

Note now one person broke their leg in the test, and that was a success.

My training has involved handling objects covered in human soot, and listening to the relatives of those who died in trying to escape a burning aircraft.

You can listen to your music in normal flight. For high risk portions of the flight, we want you to know whats going on, and to be able to get out quickly.


edited about a million times until the link & post worked in tapatalk

Re: Please switch off all electronic equipment....
« Reply #58 on: December 15, 2011, 09:45:41 pm »
Now that actually makes sense!  Thanks!   :thumbsup:

Amazing how you don't see things from another perspective until it's pointed out to you!



David Martin

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Re: Please switch off all electronic equipment....
« Reply #59 on: December 15, 2011, 10:36:20 pm »
I am surprised that no-one has posted this link yet
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Jaded

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Re: Please switch off all electronic equipment....
« Reply #60 on: December 15, 2011, 10:50:58 pm »
Now imagine that you didn't know that it was happening, the aircraft is on fire, and at a funny angle. Everyone on board will be in headless chicken mode, not pre-primed volunteers.

Post Manchester my sister was involved in evacuation experiments at Cranfield. They ended up giving the first 10 students out a bonus to simulate the desire to save ones life. The findings included some very counter intuitive stuff. Some people way back survived by climbing over seats and some right by the exits died by being too polite. If you want to survive a plane incident forget everyone except yourself. Leave your partner and kids and get the fuck out.

I've been in a transport incident that involved fire, funny angles and no pre-primed volunteers. There was no headless chicken mode. Just a lovely human reaction to the extraordinary.

My earlier point was that people will leave phones on, for whatever reason, and that planes are not falling out of the sky willy nilly due to these left-on phones. I'm sure that most of these phones left on are not based on 'uneducated arrogance for short term satisfaction'.

There is stuff that the airlines do that positively encourages phone use. Hell, you can use the fuckers until the cabin doors close! What kind of messed up message is that giving to passengers?

Put a gate at the gate that detects switched on phones and if you set it off, you don't fly. If it is as dangerous as stated. If not, well, we probably will carry on as we are, with many live phones per flight. To stay safe, just don't catch a plane in Russia.
If you don't like your democracy, vote against it.

Wonky

  • Not exactly straight or narrow
Please switch off all electronic equipment....
« Reply #61 on: December 16, 2011, 07:14:08 am »
Whilst safety is the key priority, Airlines are run by marketeers and money men. Lack of passenger convenience (telling people to turn off phones etc) adds to the general stress level and increases the possibility of passengers going into rant mode and choosing someone else to fly with next time.
The questions about phones and gadgets are regularly asked within the business. "do we really have to inconveniece our passengers in this way?". Once the issues are explained, a deal is brokered to keep the inconvenience to a minimum. Hence, anything goes until engine start, no gadgets on takeoff and landing, and non-transmitting devices are used in 'normal' flight.

Re: Please switch off all electronic equipment....
« Reply #62 on: December 16, 2011, 07:57:53 am »
I personally believe that you completely miss the point Jakob.   

When nobody knew what danger the volcanic ash clouds really represented, some airlines were clamouring to get planes in the air simply because they want to make money.   It is quite obvious that certain people in the industry put money before anything else, and that independent regulation prevents them having their way, sometimes.

Imagine what that rather vocal airline ceo would have said had a plane dropped out of the air:   He certainly wouldn't be contrite and humble IMO.       

Just because a worst case scenario hasn't yet happened doesn't mean that it cannot.

Oh, has anybody yet found the cause of that Air France passenger jet that mysteriously downed in the Atlantic?   

Re: Please switch off all electronic equipment....
« Reply #63 on: December 16, 2011, 08:50:25 am »
The first time I had two phones with me when travelling, I forgot about the second and didn't switch it off.  Thankfully nothing happened, but I do normally do as I'm told.

What I haven't managed to figure out is why they make me switch my poor little ipod off-it has no sending or receiving capacity.
Well, you say that, and you might be right. But it's near impossible to tell at a glance if the iPod/shinyElectronicThing is one that has 3G, WiFi or just really sh!t shielding. So the only sensible thing is to have a blanket "turn it off" policy.
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TimC

  • Bike pilot
Re: Please switch off all electronic equipment....
« Reply #64 on: December 16, 2011, 09:01:02 am »
My earlier point was that people will leave phones on, for whatever reason, and that planes are not falling out of the sky willy nilly due to these left-on phones. I'm sure that most of these phones left on are not based on 'uneducated arrogance for short term satisfaction'.

There is stuff that the airlines do that positively encourages phone use. Hell, you can use the fuckers until the cabin doors close! What kind of messed up message is that giving to passengers?


If the measure of the sense of keeping phones non-transmitting in flight is simply 'do they fall out of the sky?', then patently we should all be encouraged to keep our phones on. However, and as you've spotted, aeroplanes rarely fall out of the sky for any reason, let alone because a passenger is trying to ring aunty Nell on their Nokia.

However, there have been several occasions where large passenger aeroplanes have suffered 'navigational anomalies' (ie for a short period of time, the kit didn't know where it was), or 'instrument anomalies' (where the indications on engine or other instrumentation is varying randomly). These events have, after much testing and investigation, been put down to the probability that mobile phones in 'search' mode, amplified by the characteristics of the structure of the aeroplane and the juxtaposition of the phone to the structure and the sensors involved, have generated a signal that could interfere with the aircraft's systems.

The consequences of this have not been, and are unlikely to be, the destruction of the aircraft. However, 'navigational anomalies' in the final phase of flight, in bad weather, when the kit is absolutely essential for a safe landing in the right place, are highly undesirable and could be contributing factors to, say, a diversion to somewhere else with better weather, or, at worst, a botched automatic landing - with all that that implies. Equally, in the cruise, navigational or other instrument anomalies are likely to persuade me that a diversion to a suitable nearby airport is preferable to continuing, with all the cost, inconvenience and delay to you the passenger - and far greater inconvenience to the airline in investigating the 'fault' - that would be incurred.   

More modern and larger aircraft are less likely to suffer these anomalies than older or smaller ones, but for consistency the same procedures are applied to all public transport aircraft, and are mandated by the various aviation authorities acting in concert. That mandate has the law behind it in the form of the Air Navigation Act.

Aircraft and IFE systems are currently being rolled out which allow the safe use of mobile phones in the air. Whether that's a good thing or not depends on your perspective, but it will be quite soon that your ears will be assaulted by the person next to you calling Aunty Nell and exclaiming, in a voice that needs no electronic aid to transmission, "Guess wot, I'm on A PLANE!!". Relish the silence while you still have it.

Incidentally, and apropos MV's  tale about electro-magnetic testing of military aircraft, in the late '70s or very early '80s, I was piloting an RAF Hercules and about to take off from RAF Marham back to base at Lyneham. Next to us was a formation of two brand-new Tornado GR1s which had automatic wing sweep (not at that time fitted to the F2 version). We got a message from the tower to call 'Ascot Ops' (our bosses at RAF Upavon in Wiltshire), so we fired up one of the 1000w HF radios. As we began transmitting, I was aware of some consternated chat on the UHF ATC frequency.  Turns out our transmissions were interfering with the Tornados' wing-sweep electronic gubbins and the wings were moving of their own accord! I later discovered that the EM assessment of the Tornado had been curtailed for whatever reason - though it was quickly resumed; not long afterwards I took a number of BAe and RAF engineers to the USAF EM testing establishment at Albuquerque to complete the job!

ETA: 3G phones most certainly do create the familiar 'handshake' interference, particularly when they are struggling for a signal. We hear them very frequently on the aircraft's intercom while we're in the pre-flight preparation. Usually it's our own phones...

Also, in the old days of analogue phones, it was certainly possible to use them in the air. I did, frequently! But only in good weather, and when I could see the ground.

Re: Please switch off all electronic equipment....
« Reply #65 on: December 16, 2011, 09:21:15 am »
ETA: 3G phones most certainly do create the familiar 'handshake' interference, particularly when they are struggling for a signal. We hear them very frequently on the aircraft's intercom while we're in the pre-flight preparation. Usually it's our own phones...

Being pedantic, that'll be your 3G phone trying to do a fallback to GSM because it can't get a 3G signal. 3G is spread spectrum and doesn't do the 217Hz time division switching of the transmitter on and off that gives the well known GSM noise. If you had a pure 3G phone (or set your handset to 3G only) it wouldn't do that!

ISTR years ago that mobile phone contracts had a clause in them that allowed the network to disconnect you if you left your phone turned on when on an aircraft - but that was to do with causing problems in the network rather than falling-from-the-sky-fiery-death.

TimC

  • Bike pilot
Re: Please switch off all electronic equipment....
« Reply #66 on: December 16, 2011, 09:31:21 am »
I'm sure you're right about the 3G thing, but my i4S is certainly doing the handshake thang right now and I'm getting it at malingi watts through my computer speakers while trying to relax to a bit of gentle Nickelback!!

As for the disconnection, yes - there was certainly an automatic disconnection from the network if your phone could be seen on too many cells. But at a couple of thousand feet or less (often much less!), it wasn't a problem.

border-rider

Re: Please switch off all electronic equipment....
« Reply #67 on: December 16, 2011, 09:48:37 am »
Being pedantic, that'll be your 3G phone trying to do a fallback to GSM because it can't get a 3G signal. 3G is spread spectrum and doesn't do the 217Hz time division switching of the transmitter on and off that gives the well known GSM noise. If you had a pure 3G phone (or set your handset to 3G only) it wouldn't do that!

One argument for allowing phone use on planes is that they can install a local 3G base station so that the phones will be running on very low output power in 3G mode; the 2G pulsing is a far more potent interference source than the rather gentle spread-spectrum 3G signal, especially when it's shouting at a base station on the ground.

Jaded

  • The Codfather
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Re: Please switch off all electronic equipment....
« Reply #68 on: December 16, 2011, 09:50:52 am »
Quote from: TimC
Aircraft and IFE systems are currently being rolled out which allow the safe use of mobile phones in the air. Whether that's a good thing or not depends on your perspective, but it will be quite soon that your ears will be assaulted by the person next to you calling Aunty Nell and exclaiming, in a voice that needs no electronic aid to transmission, "Guess wot, I'm on A PLANE!!". Relish the silence while you still have it.

Well, I think it will be a bad idea, since it will be another area for confusion, until all planes have the technology (which is unlikely to be for several decades). Mixed messages are not good for getting passengers to follow basic rules.
If you don't like your democracy, vote against it.

Re: Please switch off all electronic equipment....
« Reply #69 on: December 16, 2011, 10:03:21 am »
One argument for allowing phone use on planes is that they can install a local 3G base station so that the phones will be running on very low output power in 3G mode; the 2G pulsing is a far more potent interference source than the rather gentle spread-spectrum 3G signal, especially when it's shouting at a base station on the ground.
This has been on the cards for many years now.  A good thing about that is that the airline could probably charge a nicely inflated rate to use the service just as they did when seat back phones were introduced in the 90s, $6 a minute.  A nice charge like that would reduce the inane (insane too) telephone chatter.

It would also be good to ban phones until the baggage collection hall.  This would reduce the logjam of people who just have to switch on the phone and check messages etc just as soon as they can i.e a few paces from the airplane door.   Hack their ankles I say!

Re: Please switch off all electronic equipment....
« Reply #70 on: December 16, 2011, 11:01:46 am »
What I haven't managed to figure out is why they make me switch my poor little ipod off-it has no sending or receiving capacity. ...

Modern electronic devices are progressively running at higher and higher frequencies, which can exacerbate EMC issues.  Put very simply, the ability to screen out a frequency depends on it's wavelength, and very high frequencies have very short wavelengths.  As these frequencies go up, and hence the wavelength decreases, so even a hole in a devices screening which is only a few mm across can let a significant amount of signal through.

This screening applies to both the device potentially causing the interfernce (eg your iPod) and the one being interfered with (some aircraft subsystem).

A device doesn't need a deliberate transmitter to produce RF emissions, every electronic (or for that matter electrical) device produces some emissions.  The trick is to design this stuff so that it doesn't produce too much, and isn't affected by low levels.  Generally this isn't a problem, and most people can live with their PC speakers picking up their mobile phone attempting to communicate with a base station, or mild temporary interference to their TV picture from some dodgy Taxi company driving past.  This may not be the case for safety critical aircraft systems.

An alternative effect, is that because a laptop (or whatever) runs it's CPU so much faster, for energy conservation reasons (ie to make the battery last as long as possible) it'll often turn off, or switch to a lower frequency for significant amounts of time.  Likewise, digital electronics is using lower and lower voltages to both increase the slew rates (and hence improve performance) and decrease energy use (again to improve battery life and similar), which will tend to decrease RF emissions.

Either way, it's making the behaviour of the devices much more complex, and even harder to predict if a given device will or will not cause problems, hence the turning it off and times when any possible problems could exacerbate the situation.

That's all probably a mite technical for those who don't understand the technology (and who'll probably be offended at the over simplication!), but essentially modern technology can be both worse and better from an EMC (ie interference) point of view, but it would hard to say which one wins out, so it's best not to experiment!
Actually, it is rocket science.
 

Biggsy

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Re: Please switch off all electronic equipment....
« Reply #71 on: December 16, 2011, 11:08:56 am »
Whilst safety is the key priority, Airlines are run by marketeers and money men. Lack of passenger convenience (telling people to turn off phones etc) adds to the general stress level and increases the possibility of passengers going into rant mode and choosing someone else to fly with next time.
The questions about phones and gadgets are regularly asked within the business. "do we really have to inconveniece our passengers in this way?". Once the issues are explained, a deal is brokered to keep the inconvenience to a minimum. Hence, anything goes until engine start, no gadgets on takeoff and landing, and non-transmitting devices are used in 'normal' flight.


This strikes me as a very reasonable compromise.  I'm happy to go along with the request despite having some technical doubts.
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TimC

  • Bike pilot
Re: Please switch off all electronic equipment....
« Reply #72 on: December 16, 2011, 11:30:18 am »
One argument for allowing phone use on planes is that they can install a local 3G base station so that the phones will be running on very low output power in 3G mode; the 2G pulsing is a far more potent interference source than the rather gentle spread-spectrum 3G signal, especially when it's shouting at a base station on the ground.
This has been on the cards for many years now.  A good thing about that is that the airline could probably charge a nicely inflated rate to use the service just as they did when seat back phones were introduced in the 90s, $6 a minute.  A nice charge like that would reduce the inane (insane too) telephone chatter.

It would also be good to ban phones until the baggage collection hall.  This would reduce the logjam of people who just have to switch on the phone and check messages etc just as soon as they can i.e a few paces from the airplane door.   Hack their ankles I say!
In my airline, the facility to use a mobile when airborne will be rolled out next year across the new A330 and Gatwick-based B747 fleets. There will be no charge for using the system, other than your mobile operator's standard international roaming charges.

In the USA, mobiles may not be used in any customs or immigration area, including baggage halls. Failure to comply can result in embarrassing consequences!

Re: Please switch off all electronic equipment....
« Reply #73 on: December 16, 2011, 04:11:22 pm »

Oh, has anybody yet found the cause of that Air France passenger jet that mysteriously downed in the Atlantic?

Yes, one of those sequence of events things....but the initial cause was an instrument anomaly, not one caused by EMC though. 

As for the volcanic ash, no one knew it was dangerous until some years ago an aircraft flew through such a cloud and promptly lost power to all 4 engines.  Thereafter a precautionary principle was applied, until such time as there was sufficient evidence that some ash types and densities were not dangerous.   As that evidence built up, some airlines were clamouring to get back in the air before the rules were changed.  Far from doing so to make money they were just desperate to put a stop to a catastrophic haemorrhaging of cash while they were not flying.


Re: Please switch off all electronic equipment....
« Reply #74 on: December 16, 2011, 04:43:15 pm »
As well as the advantage of keeping the power levels sensible, a base station on the plane could presumably be rigged to phone you and ask you to switch off when necessary. Doesn't solve the problem of being unable to avoid the phone conversation of the person in the next seat though.