Speaking of Police States

[SciFi Chick]

I can't help noticing as I've wandered through airports this last week - there is a constant focus on telling on anyone for "suspicious" behavior.

We have to take our shoes off. We have to limit the amount of liquids we take on board. And all the while, the catch phrase is, "Your safety is our #1 priority." It's very chilling really.

And btw, if cell phones can really interfere with the electronics, why are they allowed on board and not forced to be checked? And why hasn't anyone used them to bring down a plane yet?

I don't know. Just not liking the whole security theater that doesn't make me anymore secure, just less free.

[Yosh]

Cell phones don't interfere with the vast majority of avionics out there. The ban has more to do with policy and the airlines not wanting to have to mediate the issue between passengers, when they get tired of listening to someone else's monologue, than any direct affect on cockpit instruments.

[Rommie]

Cell phones don't interfere with the vast majority of avionics out there. The ban has more to do with policy and the airlines not wanting to have to mediate the issue between passengers, when they get tired of listening to someone else's monologue, than any direct affect on cockpit instruments.

Oh for sure. Though I'm too lazy to look it up but apparently the FCC has all but accepted all electronic devices except cell phones to be approved during takeoff and landing since frankly any system that relies on the honor system isn't really needed, and a rule update is badly needed. Should come through by the end of the year which will be awesome as I never liked turning off my Kindle just so the plane can take off when I know nothing will happen.

Cell phones they're still going to ban for some claim that they might interfere with cell towers on the ground. Not true, of course- my dad was actually involved w a study some years ago that showed on average three people forget to turn off their cell phones per flight, but nothing happens- but no one wants to hear yakking!

Security in Europe is fondly known as "pre-9/11 security" btw and I like it- no shoes off, and depending on the airline they often never even ask to see your ID (no liquids though). But the funny thing about it is they do simple things like making the bins rainbow colored and it makes things so much nicer.

[cid]

Cell phones don't interfere with the vast majority of avionics out there. The ban has more to do with policy and the airlines not wanting to have to mediate the issue between passengers, when they get tired of listening to someone else's monologue, than any direct affect on cockpit instruments.

(snip)
Cell phones they're still going to ban for some claim that they might interfere with cell towers on the ground. Not true, of course- my dad was actually involved w a study some years ago that showed on average three people forget to turn off their cell phones per flight, but nothing happens- but no one wants to hear yakking!

The big thing with cell phones is not on takeoff/landing (although it used to be that some avionics systems like radar ran in the same frequency bands as cell phones) but in the air...up there, you could be in DOZENS of cell phone towers/coverage areas at the same time, and that really screws up the handoff from one area to another as you move along. Surprisingly enough, there is no ban IIRC on cell phone use en route...

I got a ride in a private plane once (first ride), and we went from Dayton to Indianapolis and back (ostensibly for a hamburger -- Ed just needed some flight time to stay current for something). I was havin' a ball, as I had my little IC2AT handheld 144MHz transceiver with me. I was into the Dayton autopatch making telephone calls to Mom'n'Dad'n'Grandma ("Guess where I am!!!"), not really comprehending the line-of-sight capabilities of a 100 mW signal when you're at 7000 feet up...I was bringin' up every 146.940 repeater system from Lima to Louisville...

It's the same thing with a cell phone in an airplane -- you'd be amazed at the coverage area from that high up.

[FZR1KG]

Quite simply, cell phones and avionics is a precautionary measure.
Cell phones are a transmitting device.
Transmitting devices can interfere with on board electronics. Admittedly the on board stuff has to be badly designed to do so.
The problem is that when you start transmitting in an enclosed space the coupling between the onboard electronics and the cell phone is complete.
The question becomes more a case of is the coupling compatible?

As an electronics design engineer there would be no hope in hell I would approve of a transmitting device in an aircraft without vigorous testing.
Take into account the rate that cell phones get released at and its impossible to ensure no interference due to new models constantly appearing.

One way out is the use of standards. Since there is no one that offers a standard cell phone transmission output/frequency response/bandwidth/power, standard, for aircraft manufacturers to adhere to it is always questionable to run a cell phone in an aircraft. This is also pretty hard to do since phone technology changes daily but aviation electronics needs to run decades with the same design.

And yes, there have been studies that confirm people leave their cell phones on. A few phones per flight. A far cry from 500 or so possible transmissions trying to connect to a tower if the restrictions are removed.

I hate to use the argument from authority but seriously, designing electronics is one hell of a task if its to be made near bullet proof. There is no way to guarantee safe conformance without knowing all the input stimuli and that is impossible to get data on. Net result, no engineer that is involved in the design phase will allow it. Not when the lives of 500 people or more depend on it. If they do, they are quite simply not looking at the facts or are ignorant in the problems of practical design with RF immune devices.

Having researched this issue previously I can say that there have been cases where cell phones have interfered with avionics. Usually on smaller aircraft.
Smaller aircraft magnify the effects of a single cell causing issues.

The problem is real. The reason that its not so frequent a problem is because there are restrictions and the over design/redundancy that is generally built into such systems. Change the rules however and we go from one 500mW transmitter every 75 feet left accidentally on, to five transmitters every 5 feet continuously on. Big difference. One with NO studies to investigate it I might add.

[SciFi Chick]

Oddly, on my flight to L.A., they refused to take off until everyone had their cell phones off. It wasn't anyone in my cabin, so I don't know if it was first class, or if they had some way of telling they were on, but they made several announcements about how these people were delaying us due to not turning off their cell phones.

It's the one thing I always 'narc' people out on if they're sitting next to me.

[Sigma_Orionis]

Quite simply, cell phones and avionics is a precautionary measure...... blah blah blah blah blah

Here's the "electronics engineer" pretending to justify a dumb measure caused by his flaky designs

I'll keep my phone on and tell everyone to do it too, if the plane falls IT'S YOUR FAULT

JAY FREEDOM!

[FZR1KG]

I don't design flaky avionics systems, I design other flaky electronics systems.
Get it right!

[Rommie]

Oddly, on my flight to L.A., they refused to take off until everyone had their cell phones off. It wasn't anyone in my cabin, so I don't know if it was first class, or if they had some way of telling they were on, but they made several announcements about how these people were delaying us due to not turning off their cell phones.

It's the one thing I always 'narc' people out on if they're sitting next to me.

Must've been someone in first class. While lots of stuff FZ said is correct it's actually very hard to tell if a phone happens to be on if you're in the back of the plane- but if in first class you sometimes get that buzzing one can hear in computer speakers from a cell phone, except in that case you hear it over the headphones. Which is needless to say bad, but frankly a cell phone range will probably only do that from the first class range.

To be clear guys I don't advocate allowing cell phones during flight, nor do I think that's going to happen. I know enough about electronics however to know an iPad or a Kindle is not going to down an aircraft, as that's never even potentially happened- only a few issues with transmitting devices on small aircraft as FZ said.

[FZR1KG]

You're pretty much spot on there Rommie.
Normal devices are no issue, transmitting devices are.

One way to tell, admittedly prone to lots of exceptions is the battery life of the device while fully activated.
Needless to say this falls apart with high energy density batteries and low duty cycle transmission protocols but otherwise its pretty valid.
The longer the device can run on batteries and the lower the energy density of those devices is a really good indicator of EMF compatibility.

e.g. a digital watch has a low energy density battery and lasts years and is not a transmitting device.
No effect on electronic systems as a result.

Cell phone, high energy density batteries and short battery life.
Possibly problems with external devices. The fact that it is also designed to be an efficient transmitter compounds the issue.

Laptops are in the middle ground. Depends on what they have as wireless devices built in.

Basically if its not designed to transmit RF, has a long battery life and low energy density batteries, you're pretty safe.

[Rommie]

Man, it's like we both have backgrounds in engineering and RF problem-solving!