Travel Technology - Study on cell phones

This is NOT UA specific, but is brought up so often on this forum (the only 1 I read) so I will post here, and if the Mods move it to OMNI or wherever, so be it.

Seems Carnegie Mellon did a study and cell phones DO disrupt navigation equipment...


From USA Today..
http://www.usatoday.com/travel/flights/2006-02-28-cellphones-planes_x.htm

"Granger Morgan, head of Carnegie Mellon's Department of Engineering and Public Policy Department, said the activity recorded shows that the use of electronic devices should be limited on airplanes.

Morgan said the disruptions are enough to impact a plane's navigation or other systems."


No word on your Bose headphones though.

The article cited requires further inquiry, because it doesn't support itself.

What it refers to is the fact that they took a spectrum analyzer onboard and learned that people use their cellphones even when they are not supposed to do so. (I could have told them that without doing a study). One thing I can't tell from the "study" is whether it included use of email (i.e. - Blackberries, which I see even more than cellphone) or only voice devices.

But the article does not include *any* information to lead me to believe that they established an actual effect on flight instruments. That is, the only equipment it refers to is the spectrum analyzer. I am not a EE, so I would request that one of you speaks up. Just because they proved that people do sometimes use cellphones, do you see anything in the article which makes it seem like they correlated such usage to interference?

The article cited requires further inquiry, because it doesn't support itself.

What it refers to is the fact that they took a spectrum analyzer onboard and learned that people use their cellphones even when they are not supposed to do so. (I could have told them that without doing a study). One thing I can't tell from the "study" is whether it included use of email (i.e. - Blackberries, which I see even more than cellphone) or only voice devices.

But the article does not include *any* information to lead me to believe that they established an actual effect on flight instruments. That is, the only equipment it refers to is the spectrum analyzer. I am not a EE, so I would request that one of you speaks up. Just because they proved that people do sometimes use cellphones, do you see anything in the article which makes it seem like they correlated such usage to interference?

very informal survey with light plane drivers, but no one has ever seen any interference. We use the same radios and instruments as the "big boys" and the phone is much closer to our radios and antenna.

This article is interesting reading but useless in a scientific capacity. Furthermore, the study as described in the article differs from what the first paragraph implies:

"Talking on cellphones or using laptops on an airplane could disrupt cockpit operations, especially global positioning devices that are increasingly being used to help land planes safely, according to a new study."

To test this,

"Researchers monitored radio emissions from passengers on three airlines with the support of the Transportation Security Agency. The emissions were tracked using a broadband antenna that was attached to a portable spectrum analyzer in a piece of carryon luggage."

Seems to me they are measuring the quantity EM emissions but not whether these emissions interfere with aircraft operation!

Wait, here it is-- the conclusive evidence!:

"Morgan said the disruptions are enough to impact a plane's navigation or other systems."

Well, Morgan said so, so it must be true. Bad study, worse article. Nuff said.

very informal survey with light plane drivers, but no one has ever seen any interference. We use the same radios and instruments as the "big boys" and the phone is much closer to our radios and antenna.
Plus, the big iron has much better shielding on their avionics.

I'll certainly look at the report when my issue of IEEE Spectrum arrives, but according to the USA Today article, no attempt was made to see if RF emissions from cellphones had any effect on avionics or radionavigation. A study published in the IEEE Journal of Electromagnetic Compatibility a year or two ago specifically studied cellphone emissions from the passenger compartment on a commercial airliner (not in the air), and found that they were not on frequencies that could affect avionics or radionavigation.

Wait, here it is-- the conclusive evidence!:

"Morgan said the disruptions are enough to impact a plane's navigation or other systems."

Well, Morgan said so, so it must be true. Bad study, worse article. Nuff said.
As an old professor I had would say - "The proof is trivial" or "The proof is left as an exercise for the interested student."

Reminds me of the old Far Side cartoon with the proof on the blackboard and a box in the middle that says "and then a miracle occurs".

I would think the study tends to prove the opposite. Since it proves that cell phones are being used during a (statistically significant?) number of take off and landings, and planes are not falling out of the sky and landing on terminals, I would say that supports the "cell phones are safe" argument.

Thousands of flights, millions cell phones, they are NOT all off.

Is it a triple blind test if the experimentor doesn't have a clue?

How inconclusive... how can that get published in IEEE Spectrum :confused:

The USA today article is pretty bad. Mcpaper does it again.

I found the real study: http://www.spectrum.ieee.org/mar06/3069. It addresses many points brought up in this thread.

Basically it only proves that cell phones in various electromagnetic ranges are being used on planes. It needs supporting data from NASA studies such as this (http://techreports.larc.nasa.gov/ltrs/PDF/2003/tp/NASA-2003-tp212446.pdf) to show that it is dangerous to GPS systems.

The view is that intermodulation (mixing of PED signals) is the real problem here. These "spurious emissions" have been show to cause interference on navigational frequencies, which are separate from the various cell phone frequencies.

mahasamatman, if the GPS navigation system on a plane shielded out all of the electromagnetic signals, wouldn't it be useless? The spurious emissions are the hazard here it seems.

hawkxp: very informal survey with light plane drivers, but no one has ever seen any interference. We use the same radios and instruments as the "big boys" and the phone is much closer to our radios and antenna.One phone would not operate on the frequencies for the instruments. However, multiple phones may cause intermodulation. I think they definitely need more research before rushing to approve cell phones for airplane use.

if the GPS navigation system on a plane shielded out all of the electromagnetic signals, wouldn't it be useless?
No. It's the antenna that needs to receive the satellite signal, not the actual avionics box. And the antenna should be shielded from everything below it and only receive signals from above as well. As long as the signal from the antenna can make it to the box (the cable is shielded as well), you're good to go.

It's pretty much the same for the communications equipment - shield the box and cables as well as possible, and make sure the antenna is shielded from spurious transmissions.

Since not UA-specific, I am moving to Travel Technology.

And for the op -- or anyone else -- even if there is a forum you don't read regularly, it's easy enough to subscribe to this or any other thread.

cblaisd
Moderator, United

Since not UA-specific, I am moving to Travel Technology.It looks like TravelBuzz has most of the cell phone in flight threads, e.g.:

Cell phone use in flight - inevitable? (http://www.flyertalk.com/forum/showthread.php?t=528764)
Will Cell Phones be eventually allowed on flights- your guess? (http://www.flyertalk.com/forum/showthread.php?t=444362)
Cell Phones In-Flight ? (http://www.flyertalk.com/forum/showthread.php?t=426927)
FCC considering cell phone use in flight (http://www.flyertalk.com/forum/showthread.php?t=378809)

A couple of other possibly relevant journal articles:


Electromagnetic Interference Assessment of CDMA and GSM Wireless Phones to Aircraft Navigation Radios
http://library-dspace.larc.nasa.gov/dspace/jsp/bitstream/2002/11689/1/NASA-2002-21dasc-jje.pdf

Investigation of spurious emissions from cellular phones and the possible effect on aircraft navigation equipment
Kuriger, G.; Grant, H.; Cartwright, A.; Heirman, D.;Electromagnetic Compatibility, IEEE Transactions on Volume 45, Issue 2, May 2003 Page(s):281 - 292
http://ieeexplore.ieee.org/iel5/15/27034/01200875.pdf?tp=&arnumber=1200875&isnumber=27034

One of the nightly snooze shows (NBC I think) had this absurd story the other day. What a load of crap. They CM folks were shocked (shocked!) to learn that people were using unauthorised electronic devices like cellphones in flight. Nobody bothered to mention how many of the devices were simply left on by accident. The big fear they tried to promote is that GPS data would be mangled and cause a crash.

Aha -- I found it. NBC Nightly News story here (http://www.msnbc.msn.com/id/11627970/). The absurd headline? "Don’t risk it: Turn off your cell phone on planes." It comes complete with video.
According to scientists and government officials, there is plenty of anecdotal evidence that suggests battery-operated devices, including cell phones, computers and handheld games — especially those with wireless signals — might disrupt critical aircraft navigation systems.And from the CM guy:We also found quite a lot of interference in the GPS band — that’s the global positioning satellite band — and that’s really troubling because increasingly airlines are using this for precision approach.”

...

Here (http://asrs.arc.nasa.gov/report_sets/ped.pdf) is a sample of 50 reports to NASA's Aviation Safety Reporting System that involve or could have involved PEDs. While many of the cases are just pax not turning off cell phones when told to, there are several that suggest strongly that PEDs did interfere with navigational equipment.

Here (http://asrs.arc.nasa.gov/report_sets/ped.pdf) is a sample of 50 reports to NASA's Aviation Safety Reporting System that involve or could have involved PEDs. While many of the cases are just pax not turning off cell phones when told to, there are several that suggest strongly that PEDs did interfere with navigational equipment.
Of those that report navigation equipment anomalies, many seem to be related to the localizer (abbreviated as "loc" in the reports). Each localizer is associated with a runway, is used to assist landings, and transmits a highly directional beam on a frequency between 108.10 and 111.95 MHz. Cellphones transmit on frequencies around 850 MHz or 1800 MHz. It's hard to see how a cellphone could interfere with a localizer. On the other hand, FM broadcast radios receive signals in the 88-108 MHz range, and local oscillator leakage could conceivably interfere with localizers.