GPS
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If the GPS receiver is a direct conversion type, then the biggest possible cause of interference is to the on board GPS. Not desirable. But if it's a superhet, then we have a potential problem. If it meets FCC (US) requirements on oscillator radiation, it could well have an Intermediate Frequency such that the local oscillator blocks a DME channel. If it meets EU standards, possibly not - but only possibly, depending upon which stanadrds the manufacturer has decided to declare it compliant to.
Paxing All Over The World
Contacttower
OK, what is it that you are doing then?
So: you will do what the CC tell you to do and never argue ... unless you decide not to do what they tell you and to argue because you think that there is no reason to obey them?
Over the years that this topic (transceiver devices in the cabin of commercial aircraft) has been discussed in PPRuNe, I have always put forward a cautious view. I have suggested that, since we do not know the possible outcomes AND that folks like radeng advise against it, AND that we hear reports of interrupted FD comms, that we should not rush to use them. For this, I am regularly castigated, which I find curious.
Yes, it is confusing when different carriers have different instructions about hand held devices. Well, the rules are the rules and if one carrier says they permit them on their A320s or B777s and another operator of the self same a/c does not - then that is the way it is.
Whether or not folks pilot their GA machine with two GPS units strapped to their goggles - I care not!! When aboard a commercial transport, you follow the rules of the company that you are paying to get you to the destination. That is the same if it is a taxi, a ship or an aircraft.
Do I think the risk of using a transceiver in the cabin is low? Yes. But the risk is unknown and I would like to see air travel continue with its high safety record.
Whipping out my 496 during the flight is not an 'unsupervised experiment' at all.
While of course one should always do as you are told by the cabin crew and never argue I think if you have an aviation GPS and want to use it during flight there is no real reason as such why you shouldn't.
Over the years that this topic (transceiver devices in the cabin of commercial aircraft) has been discussed in PPRuNe, I have always put forward a cautious view. I have suggested that, since we do not know the possible outcomes AND that folks like radeng advise against it, AND that we hear reports of interrupted FD comms, that we should not rush to use them. For this, I am regularly castigated, which I find curious.
Yes, it is confusing when different carriers have different instructions about hand held devices. Well, the rules are the rules and if one carrier says they permit them on their A320s or B777s and another operator of the self same a/c does not - then that is the way it is.
Whether or not folks pilot their GA machine with two GPS units strapped to their goggles - I care not!! When aboard a commercial transport, you follow the rules of the company that you are paying to get you to the destination. That is the same if it is a taxi, a ship or an aircraft.
Do I think the risk of using a transceiver in the cabin is low? Yes. But the risk is unknown and I would like to see air travel continue with its high safety record.
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OK, what is it that you are doing then?
So: you will do what the CC tell you to do and never argue ... unless you decide not to do what they tell you and to argue because you think that there is no reason to obey them?
Permitted in-flight but not during taxi, take-off, initial climb, approach and landing: Various devices listed, beginning with "Laptops with CD ROM or DVD drive" and including "GPS handheld receivers".
Whether or not folks pilot their GA machine with two GPS units strapped to their goggles - I care not!! When aboard a commercial transport, you follow the rules of the company that you are paying to get you to the destination. That is the same if it is a taxi, a ship or an aircraft.
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While of course one should always do as you are told by the cabin crew and never argue I think if you have an aviation GPS and want to use it during flight there is no real reason as such why you shouldn't.
So: you will do what the CC tell you to do and never argue ... unless you decide not to do what they tell you and to argue because you think that there is no reason to obey them?
My interest in this thread is not because I want to use a GPS system during an airline flight but because if there is an interference problem that would have very serious implications for a lot of GA types who use handheld GPS alongside radio nav avionics.
Paxing All Over The World
Fair enough Contact, I see your approach (if you will forgive the pun!). For the sake of debate then, you will see why these statements catch my attention (my italics):
Fine that you don't argue with CC but we know that others will, or will use transceivers clandestinely. The problem with commercial airline safety is that is taken as a given by many (not all). It is a well known bit of modern marketing history that flying was promoted as easy as boarding a train to fill all those lovely wide bodies and now ... people think that they are boarding a train.
It's late, I'd better get some
... they were designed for use in aircraft and as far as I know do not interfere with any of the other systems. The fact that I decide to use it on a plane that is just a bit bigger shouldn't make a difference.
It's late, I'd better get some
None but a blockhead
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It's always possible that electronic gadgets can interfere with aircraft systems, even if everything's well designed - there are an infinite number of fault conditions on both sides that can mess things up (I had an audio amp that oscillated wildly at VHF if the speaker cables were too close to some of the inputs - that blocked out my local FM reception for a while).
The question is - what are the probabilities? A well-designed GPS receiver, even if it is direct conversion (didn't they used to be called regenerative receivers, RadEng, back in the day when the BBC used to broadcast requests for the listener in Ealing causing complaints to back off the reaction knob?
) will have LO radiation figures well down, and all of the antennas for the various RF avionics will be on the other side of the skin to the pax. And broken shielding or other cabling or connection faults within the a/c will presumably increase the probabilities of interference from various sources, including other avionics, so should be fixed.
Any radio system that is mission critical has to be defensively designed, and that includes coping with rogue carriers and other non-desired energy at the input. Fortunately, especially these days, there are lots of techniques to help with this, and any regulatory regime for approval should reflect environmental reality.
Another way of looking at it is that if vital systems are vulnerable to interference from normal consumer electronic devices, then they'll be exceptionally vulnerable to deliberate attempts to attack them from modified equipment. A naughty person skilled in the art could pack a lot of unpleasantness into an iPod case...
R
The question is - what are the probabilities? A well-designed GPS receiver, even if it is direct conversion (didn't they used to be called regenerative receivers, RadEng, back in the day when the BBC used to broadcast requests for the listener in Ealing causing complaints to back off the reaction knob?
) will have LO radiation figures well down, and all of the antennas for the various RF avionics will be on the other side of the skin to the pax. And broken shielding or other cabling or connection faults within the a/c will presumably increase the probabilities of interference from various sources, including other avionics, so should be fixed.Any radio system that is mission critical has to be defensively designed, and that includes coping with rogue carriers and other non-desired energy at the input. Fortunately, especially these days, there are lots of techniques to help with this, and any regulatory regime for approval should reflect environmental reality.
Another way of looking at it is that if vital systems are vulnerable to interference from normal consumer electronic devices, then they'll be exceptionally vulnerable to deliberate attempts to attack them from modified equipment. A naughty person skilled in the art could pack a lot of unpleasantness into an iPod case...
R
Difficulty number 1:
One type of GPS may be direct conversion (that's not regenerative, by the way - it's sometimes called 'zero IF') and not radiate and another may. especially if we start talking about cheap imports from the far east, where despite all the so called rules, compliance with EU and other standards may well be imaginary. So you DON'T know, except by experiment, and when you add up all the possibilities in a modern airliner, with all the variations of stuff pax are carrying, the possibilities of interference multiply very quickly. In fact, if you have N signals, the simplest combination (3rd order distortion for the techies) gives 2N(N-1) possible interfering signals.
Difficulty number 2:
Aircraft cabling does degrade over the years, and it's a well known phenomena. It's not always possible to determine by visual inspection if the shielding is complete, or that there's no corrosion, and complete rewiring every year just would be too expensive.I seem to remember an article in IEEE Spectrum a few years ago in which they said something like a 767 has over 70 antennas, and I can well believe it. So there is a fair amount of careful; design goes in in the first place in frequency planning in aircraft installations and so on to minimise the problems, and the introduction of just one extra emission can cause problems.
By the law of Arkwright Sod, it won't happen in every situation. It won't happen every time in the same aircraft. The trouble is that it may only need to happen once. Just as back in the early '60s, some guys in Norway misread the Morse ID of an NDB and flew into the side of a mountain.
Radio systems are always liable to interference. I can readily conceive of easy to make things that could cause chaos around airports and for obvious reasons, I'm not going to say what or how here. A radio link required to be out for no more than 10 seconds a year has a dedicated frequency and hot stand by equipment. But at the end of the day, you can't guarantee a radio link - you can just do your best. It's because of the interference that major UK airports have specialist interference trackers available all the time. But that doesn't mean that you can throw another parameter into the mix and get away with it.
And to re-iterate, cheap imports from the far east frequently do not meet any of the compliance standards even though they are supposed to do so. Some companies just ignore the rules, including one major UK telecomms firm! All too often, CE on a product just means 'chinese export'.
One type of GPS may be direct conversion (that's not regenerative, by the way - it's sometimes called 'zero IF') and not radiate and another may. especially if we start talking about cheap imports from the far east, where despite all the so called rules, compliance with EU and other standards may well be imaginary. So you DON'T know, except by experiment, and when you add up all the possibilities in a modern airliner, with all the variations of stuff pax are carrying, the possibilities of interference multiply very quickly. In fact, if you have N signals, the simplest combination (3rd order distortion for the techies) gives 2N(N-1) possible interfering signals.
Difficulty number 2:
Aircraft cabling does degrade over the years, and it's a well known phenomena. It's not always possible to determine by visual inspection if the shielding is complete, or that there's no corrosion, and complete rewiring every year just would be too expensive.I seem to remember an article in IEEE Spectrum a few years ago in which they said something like a 767 has over 70 antennas, and I can well believe it. So there is a fair amount of careful; design goes in in the first place in frequency planning in aircraft installations and so on to minimise the problems, and the introduction of just one extra emission can cause problems.
By the law of Arkwright Sod, it won't happen in every situation. It won't happen every time in the same aircraft. The trouble is that it may only need to happen once. Just as back in the early '60s, some guys in Norway misread the Morse ID of an NDB and flew into the side of a mountain.
Radio systems are always liable to interference. I can readily conceive of easy to make things that could cause chaos around airports and for obvious reasons, I'm not going to say what or how here. A radio link required to be out for no more than 10 seconds a year has a dedicated frequency and hot stand by equipment. But at the end of the day, you can't guarantee a radio link - you can just do your best. It's because of the interference that major UK airports have specialist interference trackers available all the time. But that doesn't mean that you can throw another parameter into the mix and get away with it.
And to re-iterate, cheap imports from the far east frequently do not meet any of the compliance standards even though they are supposed to do so. Some companies just ignore the rules, including one major UK telecomms firm! All too often, CE on a product just means 'chinese export'.
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... they were designed for use in aircraft and as far as I know do not interfere with any of the other systems. The fact that I decide to use it on a plane that is just a bit bigger shouldn't make a difference.
Paxing All Over The World
I took a long break before replying Contact and am trying to avoid making this too personal but ...
Did you read radeng's post? Here is a professional RADIO ENGINEER, taking time to explain (again) why the use of untested electronic equipment on commercial aircraft is undesirable and your reply?
So you don't have any problem when a radio engineer does have?
To show more confused thinking, you then state that mobile phones are a completely different matter and should be banned (to try and exclude your little toy from the ban) and complete your grand sweep by saying:
If a device generates and receives radio frequencies, it is a transceiver. That means that your GPS unit is a transceiver, which is why I used the term. (some devices are transmitter-receivers and some are transceivers but they both generate and received RF)
Did you read radeng's post? Here is a professional RADIO ENGINEER, taking time to explain (again) why the use of untested electronic equipment on commercial aircraft is undesirable and your reply?
I'm never going to say they are 100% safe because you can never be 100% sure with anything. But personally I don't have a problem with people using them.
To show more confused thinking, you then state that mobile phones are a completely different matter and should be banned (to try and exclude your little toy from the ban) and complete your grand sweep by saying:
And as for transceivers in the cabin one is probably breaking the law.
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If a device generates and receives radio frequencies, it is a transceiver. That means that your GPS unit is a transceiver, which is why I used the term. (some devices are transmitter-receivers and some are transceivers but they both generate and received RF)
Paxboy, I think you need to look carefully at what you are writing...you're begining to confuse yourself. What is your definition of the difference between a transmitter-receiver and a transceiver?
A Garmin portable GPS, certainly for aviation purposes, is a receiver. From his note, that appears to be what the guy had on board. It is also tested for emmission safety by Federal and US and other authorities. I know this because I can read it in the documentation supplied with my Garmin GPS.
And it's no good getting all huffy about people posting their opinions on here..for all we know Radeng is a 75 yr old googlespert granny with time on her hands....
Paxboy, I think you need to look carefully at what you are writing...you're begining to confuse yourself. What is your definition of the difference between a transmitter-receiver and a transceiver?
A Garmin portable GPS, certainly for aviation purposes, is a receiver. From his note, that appears to be what the guy had on board. It is also tested for emmission safety by Federal and US and other authorities. I know this because I can read it in the documentation supplied with my Garmin GPS.
And it's no good getting all huffy about people posting their opinions on here..for all we know Radeng is a 75 yr old googlespert granny with time on her hands....
Last edited by strake; 11th Dec 2007 at 12:45. Reason: Edited to say sorry to radeng if he's not a 75 year old granny....
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Did you read radeng's post? Here is a professional RADIO ENGINEER, taking time to explain (again) why the use of untested electronic equipment on commercial aircraft is undesirable and your reply?
It is also tested for emmission safety by Federal and US and other authorities. I know this because I can read it in the documentation supplied with my Garmin GPS.
To show more confused thinking, you then state that mobile phones are a completely different matter and should be banned (to try and exclude your little toy from the ban) and complete your grand sweep by saying:
GPS systems are considered something completely different. If you read the sticky at the top of the ATC forum you will see why use of a VHF transceiver to listen to ATC may be illegal with the exception of airshows for example. The reason I wouldn't recommend using them on the aircraft is that they have the potential if the PTT gets stuck to block the frequency being used without the user knowing...which would have very serious implications.
Mobile phones are again something completely different, as well as radio interference there have also been reports of interference with the ILS and autopilot (among other things) and someone else mentioned DME in the 'Tech Log' forum. But GPS hasn't been known to cause anything like that in GA aircraft and I have no reason to believe it would on an airliner.
Back to the original point....I have no interest in using a GPS system or as you call it 'my little toy' on an airline flight...but the orginal poster asked a fair question and I number of people have answered that it shouldn't be a problem.
PEDs are a pain for CC and I would completely understand a blanket ban.
Paxing All Over The World
With regards to Transmitter/Receiver and Transceiver, I was going on a fairly pedantic definition which I shall not bore you with.
strake
Sorry if I sounded thus, I was trying to find the dividing line at which the correspondent decided what was, and what was not, permissible (and by who's judgement) and found it.
Having enjoyed PPRuNe for 6.5 yrs, I am well used to opinions being expressed and relish such. Indeed, I suspect that I am thought of as being opinionated myself ...
Reading Radeng's posts (who signed at the same times as I did but I am more verbose than he!) across that time leads me to trust what he says. I, of course, could just be an awkward teenager who enjoys winding everyone up and watching them fulminate.
strake
And it's no good getting all huffy about people posting their opinions on here.. for all we know Radeng is a 75 yr old googlespert granny with time on her hands....
Having enjoyed PPRuNe for 6.5 yrs, I am well used to opinions being expressed and relish such. Indeed, I suspect that I am thought of as being opinionated myself ...
Reading Radeng's posts (who signed at the same times as I did but I am more verbose than he!) across that time leads me to trust what he says. I, of course, could just be an awkward teenager who enjoys winding everyone up and watching them fulminate.
radeng is 60 years old. His father was a radio ham, who spent 3 years teaching radio at Cranwell during WW2. radeng took the radio amateurs examination on his 14 th birthday, and entered the profession in 1964. He has some 23 patent applications to his credit, 28 published articles/papers and is chairman of an international standards committee - happens to be on medical implanted wireless systems - but that doesn't alter matters. He has chaired 2 international conferences, and served on the papers committees of 4 more. radeng is also a Senior Member of the IEEE, and a reviewer for articles for the IET Electronics Letters and IET Transactions. Not quite a 75 year old granny! Mind you, the current medical problems are such that I'm not quite sure.......
Heathrow Director knows who radeng is....
Yes, a Garmin may well be no problem. But CC are not going to have a comprehensive list of which equipment is acceptable and which isn't. And in these days of clones, even such a list is a problem.
I must admit I haven't studied in detail which standards apply, but I suspect that under the regime of the Radio and Telecommunications Terminals Equipment Directive, I can legally put on the market a GPS equipment meeting the requirements of EN55013. That allows a local oscillator radiation of -13dBm or 50 microwatts. To put this in perspective, the typical sensitivity of the VHF comms is around -100dBm or 10 to the minus 13 microwatts - i.e 0.1 pico watts. And as the regime in Europe for determining compliance is pretty well non existent except partially in Germany - and even there a bit spotty- who is going to enforce things?
The difficulty is that with a wide range of possible different equipments, who knows what frequencies and levels are involved? Even with cellular, there are several different architectures and thus frequency plans.
The problem at the end of the day is that you DON'T know. And if there is a problem, it may be too late to find out......
Interestingly, at the standards meetings where they discuss mobile 'phones on aircraft, you must remember that a lot of the people there spend a lot of time flying. And they are all against it!!! Their employers may want it, but the guys who are going to have to put up with it don't want it at all......
There is an expressive French term for it. "C'est un bordel".
Heathrow Director knows who radeng is....
Yes, a Garmin may well be no problem. But CC are not going to have a comprehensive list of which equipment is acceptable and which isn't. And in these days of clones, even such a list is a problem.
I must admit I haven't studied in detail which standards apply, but I suspect that under the regime of the Radio and Telecommunications Terminals Equipment Directive, I can legally put on the market a GPS equipment meeting the requirements of EN55013. That allows a local oscillator radiation of -13dBm or 50 microwatts. To put this in perspective, the typical sensitivity of the VHF comms is around -100dBm or 10 to the minus 13 microwatts - i.e 0.1 pico watts. And as the regime in Europe for determining compliance is pretty well non existent except partially in Germany - and even there a bit spotty- who is going to enforce things?
The difficulty is that with a wide range of possible different equipments, who knows what frequencies and levels are involved? Even with cellular, there are several different architectures and thus frequency plans.
The problem at the end of the day is that you DON'T know. And if there is a problem, it may be too late to find out......
Interestingly, at the standards meetings where they discuss mobile 'phones on aircraft, you must remember that a lot of the people there spend a lot of time flying. And they are all against it!!! Their employers may want it, but the guys who are going to have to put up with it don't want it at all......
There is an expressive French term for it. "C'est un bordel".
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Hmmm, radeng...I'm not sure you've covered that as comprehensively as you possibly could. Still suspicious...these Granny's are clever. Maybe you and Heathrow Director are part of the same Darby & Joan club?
Now, please explain how electricity works
Now, please explain how electricity works
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Just for fun, here's a link on how the sun can interfere with GPS...
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I sometimes enjoy following an interesting thread, particularly within the SLF section, because someone somewhere will produce an informative and professional viewpoint. However, I do despair when good info is provided by an expert in his field and yet those answers never seem to appease those who simply can't accept NO for an answer.
Good reply radeng...
Good reply radeng...
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Hmmm, radeng...I'm not sure you've covered that as comprehensively as you possibly could. Still suspicious...these Granny's are clever. Maybe you and Heathrow Director are part of the same Darby & Joan club?
Now, please explain how electricity works
Now, please explain how electricity works
Best to keep that gps switched off then.
Technically, the smoke is in the components. When they fail, it may cause the wiring to smoke as well.
At the age of 63, I've only been making a living out of radio engineering since 1964, and I built my first radio 57 years ago......I chair a European Standards committee on radio equipment, published some 37 different papers and articles, generated 23 patent applications, have consulted for UK DTI as it then was, referee papers for the IET (used to be the IEE), and represent another organisation at the International Telecommunications Union, so I claim some knowledge.....
I still say it's better to keep the damn thing off.
At the age of 63, I've only been making a living out of radio engineering since 1964, and I built my first radio 57 years ago......I chair a European Standards committee on radio equipment, published some 37 different papers and articles, generated 23 patent applications, have consulted for UK DTI as it then was, referee papers for the IET (used to be the IEE), and represent another organisation at the International Telecommunications Union, so I claim some knowledge.....
I still say it's better to keep the damn thing off.
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Built mine in 1965 and not progressed much since then but of course I'm only a G7
I did have a play with my GPS once on a trip to the US but not much to look at on a Garmin E Trex! As far as portable radios are concerned there is so much electrical noise in a modern airliner it's a bit of a waste of time.
Just sit back and enjoy the movie and food. (Especially if someone else is paying)
I did have a play with my GPS once on a trip to the US but not much to look at on a Garmin E Trex! As far as portable radios are concerned there is so much electrical noise in a modern airliner it's a bit of a waste of time.
Just sit back and enjoy the movie and food. (Especially if someone else is paying)
