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Cell Phone Usage In Flight:

Tue Jul 18, 2000 1:01 pm

Perhaps I should have checked the archives, but I'll ask anyway.

Is there really any adverse effect on the navigational systems or accidental triggering of warning mechanisms if some one were to use their phone?

(I once heard someone say that airlines tell passengers that to merely get them to use the air phones but I have to really know.)

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RE: Cell Phone Usage In Flight:

Tue Jul 18, 2000 1:27 pm

I believe that recent tests suggest that certain mobile phone frequencies can have an effect on specific instruments on an aircraft. Especially those aircraft that have older digital instrumentation. I recall that more modern avionics have incorporated shielding against the effect of the very low Electromagnetic Radiation emmissions from the most up to date cellphones.
In one visit to the cockpit ( I wont mention the country but it was a developed country) I had this very same conversation with the capt and FO and they switched on a phone and waved it about the dials and screens to see if there were any visible fluctuations!! All this at 29,000 feet!  
The capt and FO were quite comfortable with doing this as they believed that whatever interference was so remotely tiny that there was no issue. Fortunately, on this occasion they were right and there was no deviation from any on the instruments with the phone switched on. However there COULD be longer term damage to the image quality of display screens etc and as I am not an expert, only the storyteller I hope we can get more clarification on this from other postings. The tech/ops forum may be appropriate too for qualified responses.
Better to relax when you get in the door of the aircraft, switch the phone off and forget about making calls except via the satellite phone provided in the 'plane  
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RE: Cell Phone Usage In Flight:

Tue Jul 18, 2000 1:31 pm

Most decidedly... YES!

Recently flying southbound out of SJC on a VOR course when the aircraft started a 10 degree right turn (would have been more but I turned off autopilot at 10 degree heading change). Seems someone couldn't get a dial tone on the aircraft's telephones so they decided to use their own. FA's told the gentleman to look outside (close up view of Santa Cruz mountains) and never to use a cell phone in flight again. He readily agreed it was not a good idea.

Thankfully the excellent CA weather made this a rather mild incident.
*NO CARRIER* -- A Naval Aviator's worst nightmare!
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RE: Cell Phone Usage In Flight:

Tue Jul 18, 2000 1:34 pm

My cellular is on my desk beside my computer right now. If it rings, the monitor will flicker and I will hear static thru the speakers for a brief moment.

I think they do cause some problems....but nothing that would cause an aircraft to go down.
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RE: Cell Phone Usage In Flight:

Tue Jul 18, 2000 2:53 pm

Somewhere I read that problem was also that you are constantly switching cells, so reception is bad, if at all.
The airfones use a different system as I understand it.
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RE: Cell Phone Usage In Flight:

Tue Jul 18, 2000 3:14 pm

Factoid - when they were testing the A320 way back in the mid-late 80s one of the tests Airbus did was to get the most powerful radar that Thomson-CSF produced and fire it at the nosecone/avionics bay/cockpit of the A320 for an extended period.

Nothing abnormal happened.

RE: Cell Phone Usage In Flight:

Tue Jul 18, 2000 5:06 pm

My guess would be yes because when my car stereo was stolen and I had a "boom box" type stereo temporarily in there, there was a funky noise/buzz through the speakers when my wife was using her cell phone. It was a digital one, if that makes any difference. I once actually yelled at some guy who was checking his messages via cell phone on approach!! Well, I didn't yell, but told him firmly to turn that off, NOW. He'd have been off the plane in 10 minutes and couldn't wait?!? Sheesh!
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RE: Cell Phone Usage In Flight:

Tue Jul 18, 2000 8:44 pm


Under the heading of "Mobile Phone Interference," you can download an interesting document on research into this matter at

Also, if you are to type "cell phones" in the Search function, this will give you a number of threads in which this has been discussed.

Best regards,

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RE: Cell Phone Usage In Flight:

Wed Jul 19, 2000 3:35 am

My guess is that you are right, because once I forgot to turn off my cell phone (it was in my pocket) and it rang as we were climging to altitude from SAC to SLC. I don't think anything happened. I did not answer it. I noticed though that my signal quickly diminished as we continued to climb, so it was no good any way. I turned it off.
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RE: Cell Phone Usage In Flight:

Wed Jul 19, 2000 12:39 pm

Speaking of using cellphones on flight.....

Far sooner than anyone anticipated, the cell-phone call has breached a technological wall and invaded what was literally the last place beyond its reach: the passenger compartment of an in-flight airliner.

OK, now that the alarm has been sounded, let's calm down and assess this startling news for its potentially beneficial portent. After all, many business travelers depend on cell phones. And maybe the small percentage of cell-phone users who drive the rest of us crazy will learn some manners as the strong reaction builds against cellular rudeness.

Virgin Atlantic Airways is the innovator (or perpetrator) of this development. Virgin says that it has become "the first airline to allow passengers to receive calls via their mobile phone number while in flight," using a new technology that routes incoming cellular calls to handsets at passengers' seats.

But this doesn't mean that cabins suddenly are going to be inundated with bellowing cell-phoners adding a new ring of torture to those cramped aircraft spaces. In fact, Virgin's new service, named Earth Calling, currently is available on only one airplane, a Boeing 747 that inaugurated the carrier's new direct service between London and New Delhi last week. And the service works only on cell phones using advanced GSM-type wireless service that is standard in Europe but not yet common in the United States.

"We launched it on just the one aircraft, but we have an aggressive retrofit plan" to modify the entire fleet to accommodate the technology, said David Tharp, director of in-flight entertainment for Virgin.

"It won't be disruptive to other passengers," said Sharon Pomerantz, a spokeswoman for Virgin. "There won't be phones ringing all over the plane."

Use existing handset
Instead, incoming calls ring quietly on passenger earphones or are announced in a text on in-seat video screens. To take a call, "you actually use the existing handset built into each seat," Tharp said. The cell phone itself remains off.

The system was developed by British Telecommunications under the brand name Mobile Connect. Basically, it takes a ground call and sends it to a satellite, where it then is beamed to an individual's cell-phone number on the plane, where "the handset acts as your mobile phone," Tharp said.

To receive calls, a passenger first must obtain a user card from his or her GSM service provider. The card is swiped through an armrest scanner that programs the system to retrieve calls coming in on the passenger's usual cell-phone number. Per-call costs "will not greatly exceed" those now in place for international GSM roaming, said British Telecommunications, which added that about 80 percent of European business travelers carry GSM phones. In the United States, only a fraction of cellular customers have GSM service. The new system circumvents worldwide prohibitions against using standard cell phones on in-flight aircraft because of some concerns that they could interfere with aircraft navigation systems. The prohibition, which is enforced on aircraft by the Federal Aviation Administration, was instituted by the Federal Communications Commission in landmark 1981 regulations that reallocated certain radio frequencies to encourage growth and competition in the fledgling cellular industry.

Concerns about the potential for interference were important factors in the cell-phone prohibition, said William Adler, a former chief of the FCC mobile services division who helped to draft the regulations. But the main thrust of the regulations was to divide the cellular broadcast band in a way that let competing cellular providers in nonadjacent areas across the country use the same frequencies without overlapping signals, said Adler, who now is general counsel at Globalstar, a provider of mobile and satellite telephone services based in San Jose, Calif.

The same frequencies can be used simultaneously in different areas because a cell-phone signal from the ground does not wander much beyond its intended receiving station. But from an airplane 6 miles high, cell-phone signals reach the Earth in a wide cone that covers a big chunk of geography.

"The radio traffic-management system gets completely undermined," Adler said. "Potentially, with cellular calls from airplanes, you'd have dozens and dozens of base stations receiving your signal and getting confused." Among other things, billing for calls would become chaotic.

Other airlines considered
On-board cellular-call service, which British Telecommunications is marketing to other airlines besides Virgin, is just the most recent technological leap in a rapidly changing new era in which airline passengers ultimately will have not only personal cell-phone service but also e-mail and broadband Internet access.

But technology does not address the problem of bad cell-phone manners. Adler speculated that Americans in general are less accustomed than Europeans to ambient public noise and therefore more likely to speak unnecessarily loudly into a cell phone. He said the cellular industry should consider mounting a publicity campaign to promote the simple idea that it is not necessary to bellow into a cell phone.

Pomerantz at Virgin, meanwhile, has faith that on-board cellular calls will not become just one more annoyance in air travel. "Hopefully, people won't be shouting on the phones," she said. "You have to assume that your passengers are polite."

Copyright 2000 Star Tribune. All Rights Reserved
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RE: Cell Phone Usage In Flight:

Wed Jul 19, 2000 2:04 pm

doesn't virgin also give connecting passengers palm pilots when they are on the ground in lhr/lgw?
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RE: Cell Phone Usage In Flight:

Thu Jul 20, 2000 12:35 am

Some people are so irritating to me, I was flying from IAH-JAX and some stupid as* behind me called his friend in JAX to have him pick him up at the airport, Im like ok couldnt you have done that in the airport. Anyhow when we got to JAX he called his friend and was like "were at the gate now, do you see my plane" Im just like ok are you special now cause you have a cellphone, everyone was kinda laughing at how stupid this guy was.
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RE: Cell Phone Usage In Flight:

Thu Jul 20, 2000 1:14 am

Yes, it is quite possible for the electromagnetic radiation from cellphones (which are transmitters after all) to affect aeroplane navigation systems. The same also applies for certain electronic toys, radios and televisions. It is for the same reason hospital Intensive Care Units prohibit cellphone use - the transmissions can affect these monitors too.

Yes, the chance of a mishap is small but would one like to experience the effects of that small probability? Better switch off that phone before you enter the airport!

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Thu Jul 20, 2000 3:40 am

The relative problem relates to the frequency with which your carrier is using. There are six major frequencies:
Analog 800 MHz (most major analog carriers)
AMPS -digital- 800 MHz (SMS service)
TDMA -digital- 800 MHz (Time Division Multiple Access)
US Cellular, Bell South, Nextel
CDMA -digital- 800 MHz (Ameritech)
CDMA -digital- 1900 MHZ (Patent-Qualcomm (Sprint))
GSM most of europe except Israel freq. unknown
CDMA = Code Division Multiple Access

Analog 800 was the original frequency opened up by the FCC for cellular communications in 1959. Analog 800 is the most likely suspect in aircraft interference, and autopilot anomalies. The low frequency of this band, coupled with its lack of divided sound packets allow it to do the most damage to magnetic navigational devices.

TDMA, since it divides its vocal packets into digitally encoded time-based segments (it fractionalizes your voice into milliseconds, is digitally encoded, broadcast, digital transponders broadcast to your handset, is decoded, reassembled, and you hear a voice), is also more prone to interference, though its digital capabilities are less intrusive to magnetic devices, CRTs, and comm. devices. This was the first digital PCS frequency, and the quickest to expand simply because it did not require the construction of any new 'towers'. TDMA towers also can still broadcast analog signals, thus seamless transitions between TDMA 800 and analog 800 are possible.

CDMA 800/1900 have been proven NOT to cause interference. By coding voice into data packets, instead of time segments, it's an all-digital network, more like a satellite broadcast of data at a low altitude. CDMA, especially 1900 is secure, nearly "uncrackable", and is an excellent vehicle for wireless data, thus Sprint's Wireless web WAP.

GSM, and Virgin's service of GSM call-routing is available through the use of a GSM receptor aboard the aircraft. GSM coverage is hardly existential in the US, and probably never will be, as CDMA is faster, clearer, and has a much larger network that expands exponentially on a daily basis.

Those of you who experience 'flicker' when your monitor is on and you receive an incoming call, it has more to do with handset strength than it does frequency, although only TDMA/Analog 800 will cause it. Especially Nextel users, since it's a 3-watt handset (watch your brains, Nextellers), it would cause interference on just about any electonic device.

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