[QUOTE=PoorYorick]
Sorry for the high jack but . . . Huh?! I’m a frequent flier and I’ve never heard of this. Take-offs make me a bit nervous and I *always * have my nose in a book then. Nary a comment.
[/QUOTE]
As I pointed out, what is and isn’t allowed isn’t consistent and apparently changes from time to time. Hasn’t happened to me too often, but I did get it once or twice.
[QUOTE=Broomstick]
As I pointed out, what is and isn’t allowed isn’t consistent and apparently changes from time to time. Hasn’t happened to me too often, but I did get it once or twice.
[/QUOTE]
Thanks. I didn’t mean to sound snarky, it just took me by surprise.
Any electronic device is a potential source of interference, even if it is not an “intentional transmitter”. Consumer-grade electronics hardware is often poorly designed and poorly shielded. Radio receivers and anything with digital circuits are possible sources of interference. In radio and television receivers, the local oscillators used in super-heterodyne receiver designs often behave like transmitters. Digital circuits run at high frequencies and often produce substantial amounts of radio-frequency noise.
I’ve read the reports in NASA’s Aviation Safety Reporting System database, and while they may be anecdotal and not meet some people’s standards for evidence, I think there is enough information in the incident reports to make a strong case that passenger electronics devices are a potential source of interference to aircraft navigation and communication systems.
[QUOTE=Broomstick]
Well, sir (or madam) that is YOU, and bravo to you if you keep your personal stuff under such control during the flight. Other people, however, are not you. I will also point out that computers, drinks, and food are also not supposed to be out and about during take off and landing, and I have been reprimanded at times for having my nose in a book while a commercial passenger. So my second point holds: during take off and landing, which is when you are most likely to get abrupt movements, they don’t want loose objects in the cabin. This may or may not be enforced consistently, and while your iPod may be safely strapped to your arm the one belonging to the guy ten rows away may not. We’ve covered this before in other threads, that the flight attendants don’t really have the time to inspect what each passenger is doing so they ask everyone to do a certain thing for consistency.
[/QUOTE]
So if what they’re really saying is “put your stuff away,” then they should say it. My iPod is already away, and I take out one of the earpieces during announcements.
[QUOTE=LurkMeister]
On the subject of keeping potential projectiles under control, I’ve noticed the last few times that I’ve flown that passengers are being told not to put their laptops in the magazine holders. It seems to me that the magazine holder would be a safer place for them than on your lap. Does anyone know why we’re being told this? It doesn’t really matter to me, because even when I am traveling with my laptop I don’t use it during the flight.
[/QUOTE]
I’ve never heard that, but I couldn’t put it there anyway. I have to remove the in-flight magazines because there isn’t room for my knees. I’m certainly not going to be sticking my computer in there.
[QUOTE=mks57]
I think there is enough information in the incident reports to make a strong case that passenger electronics devices are a potential source of interference to aircraft navigation and communication systems.
[/QUOTE]
As noted above, if this were so, you’d have to be nuts to deal with this by saying, in effect, “Welcome to our flight ladies and gentlemen - we’d like to respectfully request that anyone who plans to operate a device capable of causing our aircraft to crash consider not doing so.”
So why was I sternly warned not to turn on a GPS receiver when I was last on a plane?
AFAIK, GPS units (at least at the consumer level), don’t send signals, they receive them.
[QUOTE=HeyHomie]
So why was I sternly warned not to turn on a GPS receiver when I was last on a plane?
[/Quote]
Probably because the person who told you this neither knows nor cares about the distinction between receive and transmit.
With respect to the satellites, all GPS units are receive-only.
Are radios really that much of a safety issue? I often take a small FM radio onto aircraft with me (my MP3 player has one in it) and it’s a really interesting experience being able to listen to a variety of radio stations from hundreds (or even thousands) or kilometres away.
I don’t have it going during take-off or landing (as per crew instructions), but I’d be more than a little concerned if modern avionics were so delicate that the FM radio component of an MP3 player would be enough to cause havoc during level flight.
I think anyone should be able to do anything they want on an airplane that is not 100% proven to cause crashes. it is their right. The airlines are there for their convenience. :: shrug ::: They should not even be able to make a profit because that is unfair to the poor folks. Flying is like driving, it is a right of all Americans… Just ask them… Last guy that said it was his right to do it his way, (his airplane he was trying to learn to fly in ) well I let him. He broke his airplane real bad. I walked away laughing my ass off. Bawahahaha
[QUOTE=Martini Enfield]
Are radios really that much of a safety issue? I often take a small FM radio onto aircraft with me (my MP3 player has one in it) and it’s a really interesting experience being able to listen to a variety of radio stations from hundreds (or even thousands) or kilometres away.
I don’t have it going during take-off or landing (as per crew instructions), but I’d be more than a little concerned if modern avionics were so delicate that the FM radio component of an MP3 player would be enough to cause havoc during level flight.
[/QUOTE]
Your MP3 only receives FM signals, it does not transmit anything (don’t nit pick me here). The radio waves are coming from the ground antennas, and your MP3 player being on or off doesn’t change anything.
[QUOTE=treis]
Your MP3 only receives FM signals, it does not transmit anything (don’t nit pick me here). The radio waves are coming from the ground antennas, and your MP3 player being on or off doesn’t change anything.
[/QUOTE]
That was my understanding as well, so I’m leaning towards the “Aircrew want to make sure you’re paying attention if something goes pear-shaped and not listening to Jack FM…” as the reason for the “No radios or electronics on take-off/landing”.
[QUOTE=Martini Enfield]
That was my understanding as well, so I’m leaning towards the “Aircrew want to make sure you’re paying attention if something goes pear-shaped and not listening to Jack FM…” as the reason for the “No radios or electronics on take-off/landing”.
[/QUOTE]
Personally, I have no doubt that this is the reason. There are other aspects of takeoff/landing that suggest the same, particularly the dimming of lights for night operations and so on. Basically, it’s a good idea to be aware of your surroundings, and it is certainly a good idea to listen to announcements and safety briefings rather than listen to George Michael on your iPod.
[QUOTE=Martini Enfield]
I’m leaning towards the “Aircrew want to make sure you’re paying attention if something goes pear-shaped …”.
[/QUOTE]
FWIW, this is the explanation given by all the airline pilots I know (about a half-dozen).
One of them did some experiments (on the ground) to see what a cellphone would do when operated in the cockpit. He reported that the biggest apparent effect was some minor distortion of the display on one of the video screens when a ringing cellphone was placed right next to it. (This is, of course, very far from a thorough evaluation of the potential effects.)
[QUOTE=Xema]
Probably because the person who told you this neither knows nor cares about the distinction between receive and transmit.
With respect to the satellites, all GPS units are receive-only.
[/QUOTE]
Radio receivers, including GPS receivers, are unintentional transmitters. They may not be designed to transmit, but they often do, due to leakage from circuits like the local oscillators used to down-convert incoming signals.
This has been known for over 50 years and has been exploited by the police, intelligence agencies, tax inspectors and market researchers.
[QUOTE=mks57]
This has been known for over 50 years and has been exploited by the police, intelligence agencies, tax inspectors and market researchers.
[/QUOTE]
Yes, among other things, it’s a natural consequence of the superheterodyne circuitry (which mixes the signal from a local oscillator with the incoming signal to produce a beat frequency which, in turn, is what is actually tuned) that radio receiver devices use to accurately tune a desired signal while rejecting harmonics. Radar detectors use such a circuit,and police in states, like Virginia, where they are illegal have sensitive receivers which can detect the weak signal produced by the local oscillator.
[QUOTE=Santo Rugger]
Mind quoting the relevant text, so I don’t have to wade through 28 pages to find out which part of the aforementioned statement is dead wrong?
[/QUOTE]
Here is an article from IEEE Spectrum on a similar study which is easier to read. I read it when I got the magazine.
In addition, a significant number of people don’t want to fly next to someone yakking on a cellphone through an entire flight, so there is a lot of non-technical resistance also. The old seatrest phones were way too expensive for long conversations.
[QUOTE=treis]
Your MP3 only receives FM signals, it does not transmit anything (don’t nit pick me here). The radio waves are coming from the ground antennas, and your MP3 player being on or off doesn’t change anything.
[/QUOTE]
As I’ve said before, radio receivers are often unintentional transmitters, and that is a fact, not a nit. FM broadcast band receivers are a wonderful example. The typical receiver has a 10.7 MHz first IF. The local oscillator frequency for the mixer that converts an incoming signal to the 10.7 MHz IF is typically set to the sum of the input frequency and the first IF. So if you are listening to a station at 100 MHz, the local oscillator is set to 110.7 MHz. If you look at a frequency allocation chart, what is immediately above the FM broadcast band? The aeronautical band (108-136 MHz), which is used for aircraft communications, navigation beacons and landing aids. So if your FM radio is set to the right frequency, leakage from the local oscillator may be jamming navigation or communication systems on the aircraft. This was discovered back in the early days of portable FM radios. That’s why radio receivers should be turned off during the entire flight.
Another interesting article from IEEE Spectrum is “Do Portable Electronics Endanger Flight?” from the September 1996 issue. But it’s a little dated. One incident is from 1993 when a passenger’s notebook computer caused a noticeable effect on the airliner’s compass. Now, of course, people operate notebook computers on flights all the time. In another incident, also from 1993, about 25 passengers were listening to a football game on portable radios, causing the directional gyros to stop working entirely.