SWA GPS Policy Change (a couple of years ago)

[3WE]

A few years ago, I think SWA allowed you to use a hand-held GPS.

But, now, they are forbidden as are any other typical thing that sends or receives radio signals.

Any big stories behind the change?

I recall Nav saying on AD.com that he and copilots had more than once flown with cell phones on, so the whole radio interference angle was awfully moot. I'd also bet that every day, all sorts of flights take place with cell phones inadvertently left on....

Plus, you'd think that a passive receiver would be more innocent, although I do recall being able to blank out my roomates stereo FM radio reciever with a portable radio accross the room....just had to get the tuner in the right spot....and they you have to figure that the aircraft radio and VOR/LOC navigation freq's are just past the FM radio dial.....

Anyway, any reason that SWA allowed gps and then stopped allowing it?

[Crunk415balla]

What I always wonder is, if it is so "dangerous" to use a phone onboard an aircraft, how do some airlines allow the use of cellphones inflight now?

[ATrude777]

What I always wonder is, if it is so "dangerous" to use a phone onboard an aircraft, how do some airlines allow the use of cellphones inflight now?

By a type of signal that "blocks" the sending of signals from the cellphone to the cockpit and such.

It's a bit more technical to go into but basically the system the airlines use to allow your cell phone on board doesn't disrupt the cockpit systems and such.

As for the Handheld GPS question this is new to me. Because even looking at the Jan Issue, it claims handheld PDA's may be used in flight above 10K feet, but bans GPS receivers, (is the same system as a hand held GPS?) either way it doesnt literally state a ban of hand held GPS.

Alex

[Dmmoore]

What I always wonder is, if it is so "dangerous" to use a phone onboard an aircraft, how do some airlines allow the use of cellphones inflight now?

If the aircraft was manufactured around 2000, there is very little danger from a cell phone. However air craft manufactured prior to that time do not have the same level of shielding as aircraft produced after.

The danger is from the RF emanating from the antenna. If the RF from the antenna were to enter a circuit susceptible to the frequency, un-command things could occur. The chances are very remote but there have been several unexplained occurrences where it's possible a cell phone was involved. At no time was it ever proven.

It's entirely possible that more than one device may have been involved. Combined RF signals may cause interference that a single signal will not.

When there is a chance that a device "MAY" cause interference, the use of such devices should be restricted to phases of flight where interference is not critical.

ElectroMotive interference (EMI) is a long and frustrating subject. Science can show it's possible, they can't prove that it does. Proving a negative is almost impossible.

[Brad1711]

If I have my cell phone near my computer's (external) speakers, my clock radio, or my car stereo, and I send OR receive a text message, I get very audible interference on the speakers.

I was flying the other night as safety pilot for my friend who was doing some instrument proficiency stuff. While we were taxiing, I sent a text message to somebody. For the 5 or 10 seconds it was sending, our radios were blacked out and we had the noise interference over our headsets. I never believed cell phones could interfere with aircraft electronics until that moment. Now I turn my phone off for all instrument flight.

[Crunk415balla]

Thanks, guys. Learned all I wanted to know.

[3WE]

Ok, I want to get a little back on topic.

I'm talking about stuff that receives signals, but does not broadcast signals.

GPS units in particular!.

[Coyote]

Prolly some department of homeland over-reaction BS prompted it.

I mean, come on - lord knows what terrorists could do if they knew what altitude you were flying - not to mention course and heading info. You might be hiding it in your shoe too BTW.

Wait till some peanut butter for brains tries to smuggle a bottle of water on in a hair-doo - and we have to shave bald and put the hair in our shoes as they get x rayed...

I fly a lot, i use my GPS a lot because im curious. If your subtle about it, no one ever knows anyway. If you pace up and down the isle with it in your hand trying to get a sat lock, then I have no sympathy.

[Brad1711]

Prolly some department of homeland over-reaction BS prompted it.

I mean, come on - lord knows what terrorists could do if they knew what altitude you were flying - not to mention course and heading info. You might be hiding it in your shoe too BTW.

Wait till some peanut butter for brains tries to smuggle a bottle of water on in a hair-doo - and we have to shave bald and put the hair in our shoes as they get x rayed...

I fly a lot, i use my GPS a lot because im curious. If your subtle about it, no one ever knows anyway. If you pace up and down the isle with it in your hand trying to get a sat lock, then I have no sympathy.

I'd take my scanner with me in my carry-on but I'm always worried it will get confiscated at the x-ray.

[Airbus_A320]

I don't see what trouble a GPS reciever would cause. I mean, you use them for flying.

Anything that transmits, as stated before has potential for causing issues, but a reciever, especially one used for aviation. What could that possibly do?

[aardvark2zz]

All electronics emit interference. Some more than others.

To guestimate the chance of interference use the following points:

- if high frequency clocks are used.
- amount of AC/DC power used.
- if RF circuits used; RX and/or TX.

Now if your using the latest high performance laptop running MSFS at full resolution, your emitting a lot of RF signals due to 3 GHz clock and sub-clocks, high power consumption, minimal EMI shielding, and some wires that may act as antennas.

As for a GPS receiver (or portable radio) it may use a high frequency clock, some models may consume a lot of power, and especially these receivers use an LO (local oscillator) very near the antenna port to bring the GPS RF frequencies down to more manageable frequencies for further processing.

Although filters are used to prevent the LO from leaking back to the antenna, some will leak at approx 1 GHz (and other tones).

All receivers including portable radios, GPS, cell phones (also has a TX) can leak out interfering tones back out of the antenna.

The leaked signals may not be strong but there could be MANY signals and it just takes a few to be inband to the aircraft's radio receivers, to cause problems.

In other words RXers can interfere with aircraft radios.

TXers can do more damage as they can actually overload some sensitive opamps (operational amplifier chips) on avionic circuit boards.

One case I heard of when i worked in the avionics engineering dept at Air Can...., was that when they were TXing on their HF radios, the cabin pressure would go down. It was diagnosed to a faulty ground shield on the HF coax cable leaking a strong signal that got picked up by various wires which flooded the inputs to the very sensitive opamps of the cabin pressure controller.

To find some quality info read the following

http://64.233.167.104/search?q=cache:oymzNfNGoPEJ:www.airdisaster.com/forums/archive/index.php/t-61784.html+site:airdisaster.com+cell-phone+aardvark2zz&hl=en&ct=clnk&cd=1

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[musicman476]

I'd take my scanner with me in my carry-on but I'm always worried it will get confiscated at the x-ray.

I used to worry like that about carrying on my scanner, esp. post 9-11, but I take mine in my carry-on all the time. TSA has never hassled me once about it in 100+ legs. Now, I don't ever take it out and use it once I'm on board an aircraft, but at least I know it's safe in my pack.

[3WE]

I'd take my scanner with me in my carry-on but I'm always worried it will get confiscated at the x-ray.

Paraphrased: I take mine all the time...

Yes, I take mine too over the last 10 years and have never been questioned. I have occasionally thought I got some "evil eyes" from security when listening on it in the gate area, but never a question.

It makes for good enterainment during those nasty layovers, and once in a while you catch a little ATC-pilot debate that is priceless!

[FlyingPhotog]

This may sound odd, but...

My buddy is an Air Force Academy graduate, and he said that a reason cell phones are banned is also because they "steal the airwaves." He says the signal they receive is much stronger at cruising altitude, so it makes the cell waves weaker at ground level. I dunno, but since he studied it I tend to believe him.

[aardvark2zz]

This may sound odd, but...

My buddy is an Air Force Academy graduate, and he said that a reason cell phones are banned is also because they "steal the airwaves." He says the signal they receive is much stronger at cruising altitude, so it makes the cell waves weaker at ground level. I dunno, but since he studied it I tend to believe him.

I think he/u means that the cell phone "could" flood the local very large volume with one phone call. In the old analog networks, other calls on the same frequency could be "jammed" over a large area of several networks. In brief.

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