Do cell phones work on commercial jets in flight ?

If your flying across the U.S.A. in a jet at cruising altitude - will your cell phone work ?

How would it know which cell tower to lock on to .....and wouldn't it be too far away from the tower ......(in miles)... to get a signal anyway ?

The attendants tell you not to use em during take-off and landing so they don't interfere with flight instrumentation- but that's at ground level.

I don't fly - so I wouldn't know . Who can tell us? Do they work up there ?



( I'll tell you my reason for asking later )

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Yes, usually they work just fine.

That's how they called their loved ones on 9/11 on the flight that crashed in Pennsylvania.

There is an (unwarranted in my opinion) fear that your phone will interfere with the airplane's navigation and/or communication system.

www.jetcareers.com

multiple disccusions on this between real airline pilots. I havent heard of a case where it actually interferred with navigation, but I have heard pilots talk of clearly hearing cell phone conversations in their headsets.

Years ago I used to teach at an agricultural college out in the middle of nowhere. The husband of a mature-age student who was attending a short course was an airline pilot. His flight path took him pretty much straight over the college, by the time he reached us the plane was at cruising altitude and all we could see on a clear day was a tiny spot moving across the sky.

A few times he called his wife from the plane using a normal mobile/cell phone, basically to say hi and "I'm waving at you..." etc...

According to her the risk of the phones interfering with the aircraft's electronics is pretty much non-existant, but the mobile phone companies get pretty ticked off with handsets travelling so quickly between cells and therefore causing some sort of confusion or extra use of resources.

One solution that has been proposed is for each plane to have it's own "local cell" which passenger handsets would work via, and then just a single link from the plane to the phone newtork.

Andrew

magic79 said:

Yes, usually they work just fine.

That's how they called their loved ones on 9/11 on the flight that crashed in Pennsylvania.

There is an (unwarranted in my opinion) fear that your phone will interfere with the airplane's navigation and/or communication system.

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Well.....magic79......that was my exact reason for asking.

Do you know this 1st hand....have you used your phone in flight ?

When flying across the top of so many towers at high speed....seems like it would spend all its time re-acquiring a new signal and logging in and out of cell sites.

And cruising altitude of 35,000 ft is a few miles up....so I just don't see how it would work. Can you actually explain why and how it works ,I am very currious .

I just wanted to make sure it wasn't something the Govt. was just telling us. So if you've used a normal cell phone up there --- I guess it's true . ... thanks


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@ premium rates of course.. :huh2: :thumbsdow

Your cell phone is capable of transmitting quite a ways when it's line of sight between you and the cell towers. The problem is that the cell system is designed so that you only see a few towers at a time. When you are 7 miles high you may be in range of hundreds of cell towers.

This is a problem for the cell companies since part of the cell design is to have your phone talk to the towers, relating information such as your phone ID and signal strength for the towers it can hear. The cell system uses this info to figure out which tower (and which channels) you will use.

As you drive along your phone tells it's assigned tower about it's signal strength readings, and at some point the call is transferred to a cell that you are entering. IIRC, in 1994 the PCS phones we investigated were barely able to handle the call transfer at 65 MPH. As you can imagine, this causes problems as you come in for a landing at 250 MPH, flying low over the city.

If I recall correctly, the old analog cell service had only about 200 channels per cell site. Directional antennas allowed them to handle 3 to 6 times that many calls. If you had 5 planes circling the airport with 1000 passengers, you can see that it could overwhelm the cell sites for 20 or more miles.

One thing that might be a rude awakening for folks who leave their cell on during a cross country flight; Roming charges as their phone registers with dozens of cell companies across the country.

Daniel
P.S. The early PCS phones had very, very small cells. The design specs called for them to be used when the caller was stationary. There was no assurance that you could walk a block without being dropped. Call transfers were not expected to be sucessful if you exceeded 15 mph. This was 1994-1995, mind you.

The story in Amateur radio circles is that back in the days of the high roaming fees, customers complained when the phone was picked up by many cells and the roaming charges were racking up like the national debt. The easy out was to have the cover story of the interference causing electronic problems in the plane. This could be part true and part urban legend.

Now that congress wants to allow cell phone use while in flight the interference is all those self important types yelling on the phone in multiple animated conversations annoying the rest of us.

But I feel those types and their oversized bags should ride in the cargo hold of the plane. That's just my opinion.

BTW mine works just fine and receives email without any troubles. Even on a little turboprop where the distance from the flight controls to the phone are closer.

There are plenty of stories and what if's and the like, but I have yet to read about documented cases. There have been some news reports of planes having to go around due to loosing their radio at a crucial moment, but I dont know if it was ever really proven to be because of a cellphone. I think that most of the blanket denial of their use has to do with the industry being completely unable to actually test your specific handset and find out if it's bad or not. Even a regular radio receiver can transmit a lot of noise from it's internal oscillator to mess up their receiving of radio beacons. So with something that can actually put out a couple of watts of power it has the potential to put out tons of garbage. this is wasteful though and so a properly designed and operating phone wont do much of that. But cellphones are a commodity product and nobody will be willing to pay for a properly shielded internal oscillator when it makes no difference in the day to day use of the thing.

So do they then publish a list of approved phone models in the magazine in your seat back? Do they walk around and make sure that the phone you're talking on is on that list? It's just not practical so they just make everyone turn them off.

I was on a flight once where someones phone in front of me actually rang and they were able to receive the call, and then quickly toldd the person that they forgot to turn their phone off and hung up BUt we were all surprised to hear the cell ring while in flight! So they will work sometimes.

The roaming problem is interesting. I think the ultimate solution for this problem will be in putting a repeater in the plane itself. Just like some airlines are now doing with 802.11 networking. The situation with that is funny to me, some airlines are offering in flight high speed internet access, and others are still claiming that the plane will fall from the sky if you open your laptop. So obviously somebody knows something the rest dont... A repeater in the plane that used a slightly different protocol to hit the ground would solve that problem, probably fairly easily. There are repeater/amps you can buy for your own home now priced under $300 retail! I would guess that the investment in hardware to put something similar in a plane would be less than $500 for equipment and probably significantly more for the hours necessary to install the device. I will expect airlines to partner with cellphone providers to offer service and roaming charges to the rest of us. Be sure that it will be expensive to do, but cheaper than those stupid airphones they currently have (and WAY cheaper to retrofit into existing planes than that system!)

In some ways the airline industry is like the Church Once they have been telling you something for years as solid truth, even if they then discover it's not it takes a virtual act of government before they will alter their stance officially. Much more likely is the tacit switching of gears by offering a service themselves and endorsing it without much explanation...

The original "please turn off your electronics" was prompted by a false annunciator signal in a cockpit during takeoff. The cause was never determined, but it was felt that they should eliminate any possible airborne tranmissions to reduce it from ever happening again. The rest, I believe, just comes from an extension of this policy. Thus "approved devices" that are allowed to be turned on in flight are those that do not normally transmit - laptop, CD players, etc. However, most folks do not know enough to turn off their built-in wireless devices in their laptops.

My moms cell has an airplane mode on it any ideas what this does?

My guess is that airplane mode turns off the transmitter, thereby letting you use the other functions like memo pad, address book, games, etc. while in flight.

-Bill

Whatever the technical aspects, it is downright anti-social to use your phone in-flight.

It's bad enough on not too noisy trains, to hear person saying "can you hear me", to which we reply, "yes we all can", now shut up, but in the extra confined close proximity of an aircraft, louder by the way, I can see air-phone rage.

Especially as quite a lot of people try to sleep on planes.

My noise reducing headphones work a treat, it is amazing just how noisy an aircraft cabin actually is.

Have fun trying to hear the conversation by either person on the phones, and we don't all want to hear your business either, interesting as it may be.

There are stories in the UK papers about just how intimate and financially important some chats are.

One problem I can see, you can actually throw the phone out of a train window, try doing that on an aircraft.

Then I suppose there's always the loo.

Technical point: The further you are away from a base station, the higher the transmitted power radiated from the phone, and not just during conversations, as the phone checks in with base stations regularly, imagine that amount of microwave type radiation buzzing around the cabin.

Does my head in, literally.



Imagine 500 phone conversations (me not included)

"Can you hear me, I'm really important" ."Can you hear me, I'm really important" ."Can you hear me, I'm really important" ."Can you hear me, I'm really important" ."Can you hear me, I'm really important" ."Can you hear me, I'm really important" ."Can you hear me, I'm really important" ."Can you hear me, I'm really important" ."Can you hear me, I'm really important" ."Can you hear me, I'm really important" ."Can you hear me, I'm really important" ."Can you hear me, I'm really important" ."Can you hear me, I'm really important" ."Can you hear me, I'm really important" .

I think you get the point.

Sorry for going on a bit, one of my pet hates.(Train calls)

gadget_lover said:

This is a problem for the cell companies since part of the cell design is to have your phone talk to the towers, relating information such as your phone ID and signal strength for the towers it can hear. The cell system uses this info to figure out which tower (and which channels) you will use.

Click to expand...

One other point. The terrestrial network is designed with the expectation of "frequency reuse". This means, basically, that if frequency "A" is being used on a particular cell site, it can be reused two (or more) cell sites away. Adjacent cell sites use different frequencies.
This is a key design critera for cell systems. If the number of users increases dramatically in an area, the provider can increase the number of cells in that area and decrease their power, allowing them to serve more customers without needing more bandwidth.
The problem that arises when you use a cell phone from a high altitude is that you can be "seen" by multiple cell sites, some of which will be using the same frequencies. Your signal can then intefere with whoever is using the same frequeny on the other sites. If you were on the ground, this wouldn't be a problem, since those distant sites wouldn't be able to hear your signal.

This is the reason the FCC (not FAA) officially prohibts the use of cell phones from aircraft. As to why you can easily buy adapters that plug your aviation headset into both your aircraft radio and a cell phone, well :huh2:
I've not read anything about this from a practical standpoint. The issue may be entirely theoretical, or it may happen all the time and people are just used to getting disconnected and pushing "send" again. :shrug:

This would be pretty easy to fix if somebody wanted to do it. Just dedicate a few frequenices to "aviation only" use which are dispersed over a MUCH wider footprint and have the phones switch to that mode when in the air (there's a lot of ways the phone could figure that out). Of course that would reduce terrestrial capacity, and that wouldn't make a lot of business sense.

Re: "Airplane mode" - as you suspected, it switches off the radio in the phone so you can still use whatever else it does (MP3 player, games, calendar, etc.)

Re: Pico cells on airplanes. This would reduce the power output of the individual cell phones to their minimum power (about a milliwatt) which, besides avoiding ground interference, would also reduce potential EMI with the aircraft's electronics.
There's a lot of concern about the amount of yakking this will cause in the airplane, but I always fly with either -20dB in-ear stereo phones or foam ear plugs in place, so talk all you want

Cheers,
Bob

I've traveled by train (BART in the SF bay area) quite a bit and was never bothered by others using cell phones. As a seasoned traveler I usually listed to MP3s with ear buds that seal well. External noise is Waaaay down.

Sad story; I bought a new cell phone. On my trip home I manually copied every one of my 50 or so phonebook entries to the new one. I'd been doing it for about 40 minutes when the MP3 player paused long enough when the train was stopped for me to hear the 'BEEP' of the keys being pressed on the new cell phone. I spent the next several minutes apologizing to the patient lady who'd been riding in the seat next to me for all that time.

beep beep beep beep beep beep beep beep beep beep is much worse than "can you hear me".


Back on subject; I have 5 laptops (don't ask) and all of them emit enough broadband RF to hear on my AM radio. They are all stock (more or less) and FCC type accepted. One of them is so bad that I turn it off if I want to listen to talk shows. And they allow them on planes?

Daniel

When a friend of mine an I flew a year ago here in Sweden, we didn't have to climb very high until our cell phones reported no service. It seems reasonable to me that they don't want to waste all power from their base stations straight up in the air, just like you often have no service right under a base station.

Flying a small plane yourself is just about as fun as it gets with your pants on and calling from an airplane i Sweden does not work very well where the two things I learned that night.

I have used my phone on a small plane with no problems. The plethora of issues about being received in multiple cells has been (correctly) covered in other posts.

I've also had my phone ring inflight and there was no problem taking the call and telling them I had to hang up. In fact, there is much discussion going on right now, and I would bet that you will be allowed to use cell phones by the end of this year.

The "airplane" mode on cell phones simply disables the radio so you can play games, take pictures, or whatever other non-radio capabilities your cell phone might have.

As an aside, when I owned an airplane back in the '80s, I installed a 25W VHF ham radio transceiver. Hams usually use repeaters on VHF. You transmit on one frequency and receive on another. Another radio (the repeater) usually sits high on a hill so it "sees" a longer distance, allowing you to talk greater distances than just radio-to-radio.

The first time I tried to use my radio at 6,000 feet, I was tying up about 7 or 8 repeaters from as far away as 200 miles! Antenna height is everything at VHF frequencies and above (cell phones are much higher frequency).

So, your cell phone will be "heard" and registered on many, many cells from high altitude.

I used to consult with a company that made the basestation radios for cell sites. Their system scans among 16 antennas and can switch between them thousands of times per second to ensure it is receiving the strongest from your phone (it's called 'voting'). Then, the computers from nearby cells compare signal strenghts, predict which cell you are approaching/leaving and coodinate the handoff. Pretty complex!

As for interfering with the airplane avionics, I strongly doubt it. My first job out of college was designing avionics for the F-16 fighter. We had to design to withstand an EMP...which is beyond commercial requirements, but there are so many radio signals in the air of considerably higher signal strength than a cell phone, that I am pretty confident you cannot interfear with the airplane's systems unless there is a failure in cable shielding or the like.

The idea that you could ignite a gas pump by talking on a cell phone is beyond ludicrous.

magic79 said:

The idea that you could ignite a gas pump by talking on a cell phone is beyond ludicrous.

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Is it not to do with the wavelength of the mobile transmission, and the distance between the petrol tank hole and the dispenser as the dispenser is withdrawn, for that brief moment, both would match, (mm's or less) hence spark created, as in original Marconi wireless transmission.

A major issue is power. I can tell you as an Amateur Radio Operator that cell phones, or any device transmitting with enough power can cause real problems. Cell phones are only about .25w so there is very very small chance of interference. They are just playing it safe. Now, with the same 800 mhz freq. if you increase power then bad things can happen. I can use my hand held HAM radio in my office and play hell with my computer monitor and even comes through the speakers. Of course high power on cell phones next to your head not good for brain tissue.

abvidledUK said:

Is it not to do with the wavelength of the mobile transmission, and the distance between the petrol tank hole and the dispenser as the dispenser is withdrawn, for that brief moment, both would match, (mm's or less) hence spark created, as in original Marconi wireless transmission.

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WHOA!

Marconi was using between 2,000 and 25,000 volts at the spark, and the spark was drawn across a gap of a perhaps a millimeter. The spark resulted from the voltage across the spark capacitor breaking down the dielectric of the air.

A cell phone uses less than 1000 times less energy and the only thing exposed is the antenna. Regardless of the distance to the gas filler neck, it is not going to spark because there just isn't anywhere near enough voltage to breakdown the dielectric properties of the air. Further, there's no relationship between the gap and the wavelength of the transmission; the size of the gap is adjusted to fire at the voltage you want.

You might want to check here: http://www.snopes.com/autos/hazards/gasvapor.asp

They also debunked this on Discover Channel's Myth Busters (Aug 18, 2004).