Is there a danger if I or anyone on board forgets to turn their cell phone off?

I know that alot of people throw the contraption into a purse or brief case and forget to turn off, is there a real danger?

I've forgotten to do it once or twice..The plane didn't crash. I don't think there is much of a danger, especially considering that at one point allowing cell phone use on aircraft was being considered if I recall correctly.

For most phones, no, but there are a thousand variables. If it happens to be in a place where it causes interference then yes, it could be a danger.

The phones get no signal at altitude but switch to maximum power searching for a signal. This causes A) the battery to die quickly and B) a powerful signal that is more likely to interfere with communications. Have you ever set your phone by a clock radio or a speaker and then received a call? I don't want my phone causing that static interference on the radio as the pilots receive critical instructions.

You've never flown in the middle east then. There are phones ringing all flight. I have gained a whole new respect for the electronics in a plane. I really don't think that cell phones are anything to be afraid of. They're annoying...but I don't think they're dangerous...

It´s forbidden, because no one never proved that cell phones don´t have influence to aircraft.

I've accidently left the thing on in my checked bag once or twice, I'm still here. I wouldn't want them allowed on flights though, the cabin is chatty enough without having to hear about what somebody wants their significant other to pick up at the store or how the kids' school play went.

Quoting B777Neuss (Reply 4):

Thats not true, I was in the back seat of a Piper propeller plane (yes its not commercial, but it must run on the same radio system right? ) And I had left my phone on, and about 20seconds after take off we all heard the dar-dit of a phone trying to get signal and couldn't hear ATC (the instructions weren't for us but none the less) so phones can interfere with radios on planes so now i always check 3 times before we go anywhere.

Rgds --James--

I've heard them ring as well. While in VFR using GPS, it probably isn't as much as an issue as trying to navigate to a station hundreds of miles away, or shooting an approach.

I've always thought the airlines should adopt the "If your phone rings during the flight, you will be required to buy every passenger on the airplane a round of drinks" -- it would probably put a quick stop to anyone forgetting to turn it off.

i know they dont work at 3000ft on a ryanair flight dub-edi
(left mine on by mistake and on landing got a bleep saying there was a message left while i was aloft)

Quoting BillReid (Thread starter): Is there a danger if I or anyone on board forgets to turn their cell phone off?

Yes, to the airline's plan to make money from IFE services.

Quoting Flypdx (Reply 1): I've forgotten to do it once or twice..The plane didn't crash. I don't think there is much of a danger, especially considering that at one point allowing cell phone use on aircraft was being considered if I recall correctly.

Quoting JoeCanuck (Reply 3): I really don't think that cell phones are anything to be afraid of. They're annoying...but I don't think they're dangerous...

Quoting Corsair1107 (Reply 5): I'm still here.

Here are some examples of cellphone interference for those who don't understand (or are unwilling to accept) that cellphones present a hazard:


....From http://www.rvs.uni-bielefeld.de/publications/Reports/EMI.html

Some Anecdotes and Discussion

Jim Irving is a colleague who flies B737 aircraft for a major US carrier. He has an anecdote:

One day departing Portland Oregon we noted that the FMC [Flight Management Computer] Map display showed a disagreement with the "raw data" VOR position. Our training is such that we would normally immediately switch over to "raw data" and assume the FMC was in error.

We would have done that except that it was a beautifully clear day and I looked out the window and was able to determine that the FMC seemed to be right on. I called back to the cabin and asked the flight attendants to check for someone using a cell phone or computer. A few minutes later they called back to say that a man had been using his cell phone and it was now off. Strangely (?) our VOR and FMC map now agreed.

Later in the flight the flight attendants called back and said that they had caught the man using his cell phone again but this time we had not noticed any problems, perhaps because we were in cruise far from the ground and not paying as much attention.


Another pilot's account:

In our company we recently had a Localizer deviation (out of tolerances) on a B737-200 related to a GSM (mobile phone) being operated by a passenger (who was disregarding our company regulations). When requested by the cabin crew to switch off his GSM, localizer indications became normal. Is this scientific proof? Certainly not, but good enough for me as a captain to insist that all the electronic toys, computers, mobile phones, etc., are OFF during critical phases of flight. [...]

I had fuel indications on the FMC going crazy on board the B737, that returned to normal when all electronic stuff in the back was switched off. I suspect a "Gameboy" electronic game device to have interfered, but this is no more than a guess. No, I did not ask to switch the toy back on again and investigate more in depth as I was responsible for the safety of 140 passengers and this would have been extremely irresponsible! This is not a situation in which to do such testing! This [ever-present responsibility accounts for why] there is no "proof" of the relationship.

I also recall experiencing *impossible* mode annunciations on the FMA (flight mode annunciator) on B737. Having both the autothrottle AND the pitch channel of the autopilot trying to maintain speed (both in MCP SPD mode) for example, not programmed by the pilot (you cannot program that). After an expensive in-depth troubleshooting session by our maintenance department, the incompatible mode annunciations were traced to a ... faulty cockpit window heat wiring. This caused electronic interference with the auto flight system.

Here are some more incidents:

June 07, 1997. B737-300: *Verify position* was indicated on the CDU. Both IRS and radio position were correct, the FMC position was not. The difference rapidly increased to 8 nautical miles. After switching a GSM in the cabin from STBY to OFF, the FMC updated normally. FMC was correct for the remainder of the flight and on the return flight.

April 30, 1997. B737-400: During level cruise, the AP pitched up and down with ROC/ROD of 400 fpm indicated. Other AP was selected: no change. Cabin was checked for PC's and other electronic devices: nothing was found. Requested passengers to verify that their mobile phone (GSM) was switched OFF. Soon
after this request all pitch oscillations stopped.

[There was one incident reported with a] B737-200. During approach to MAN (Manchester International, UK), the LOC for landing runway 24 oscillated and centered with the aircraft not on track (but offset), confirmed visually. Ground equipment was monitored and working normally. When a GSM in the cabin was switched off, all indications became correct.

More examples, taken directly from NASA's ASRS:

In October of 1998, a Boeing 757, flying from Seattle to Covington/Cincinnati, experienced loss of all three of its autopilot systems. Flight attendants checked for a passenger using a portable electronic device and discovered a man wearing headphones, which were part of a hearing aid. The passenger was allowed to continue using the device, but was moved forward several rows. The autopilot system then regained full operational capabilities and was later checked by maintenance, with no problems being found.

In March of 1997, a Cessna 340/A pilot experienced erroneous readings when attempting to determine his location because of a passenger using a cellular phone. After the passenger turned off the phone, the pilot was able to locate his position and continue on with no problems.

In January of 1997, a regional jet was flying from Salt Lake City to Eugene. The flight crew received three separate warning messages stating that there were disagreements between the captain’s and the first officer’s instruments. The three warnings were for discrepancies in heading, airspeed, and altitude indicators. After flight attendants checked the cabin for passengers using portable electronic devices and had the devices turned off, all problems ceased.

In August 1995, an aircraft making its approach to George Bush Intercontinental Airport in Houston was advised that it was 4 miles off course. Because the course director indicators had been scalloping left and right of center, the captain ordered the flight attendant to check the cabin for any passengers using a portable electronic device. Within 15 seconds, problems with the course director indicators disappeared. The captain later learned that a passenger had been using a portable computer.

In May of 1995, the electric compass indicators of the first officer of a Boeing 737 gave erratic readings. After a sweep of the cabin was made for portable electronic devices, which resulted in flight attendants asking a passenger to turn off a compact disc player, the first officer’s instruments returned to normal working order.

Shortly after takeoff from Baltimore, in April 1994, an aircraft was advised by ground control that it was 10 miles off course, though the plane’s instruments indicated nothing abnormal. It was found that a passenger in first class was using a portable computer. After the computer was turned off, navigation instruments returned to normal.

In February 1994, a turboprop aircraft flying government officials from Lake Havasu, AZ to Yuma, AZ experienced trouble with its navigational radios. Ground control showed that the airplane was off course and gave corrections. However, the plane’s navigation system had been checked earlier in the month and was said to have zero error. After the flight, the pilot learned that at least one passenger was using a cellular phone while the plane was in the air.

In August 1992, a turbojet aircraft was notified three times, by two different control towers, that it looked to be off course. All instruments in the cockpit were showing the plane’s position to be correct. Flight attendants searched for portable electronic devices and found a tape machine and a hand-held video game unit in use. The devices were turned off and there were no other navigational discrepancies during the flight.

In September of 1990, a plane travelling from Boston to Youngstown/Warren, OH was advised it was off course and was issued a new heading. The plane’s navigational instruments showed it to be on course. After checking the cabin for portable electronic devices, the lead flight attendant informed the captain that 23 passengers were using AM/FM cassette players and one passenger was using a personal computer. The passengers were asked to turn off the devices and the flight proceeded without further incident.

--------------------------------------------------------------------

The lesson? Follow the rules. They're there for a reason.   


2H4

Quoting ASAFA (Reply 2): Have you ever set your phone by a clock radio or a speaker and then received a call?

That happens me often when I sit in front of the computer and some seconds before the phones ring besides me the computers loudspeaker makes some strange sounds and the screen sometimes gets blurred.

OK, but these incidents are relatively old. Do newer cell phones or electronic devices have different/no influence?

(Oh no, it´s a german source, bad for me)  

Quoting B777Neuss (Reply 12): OK, but these incidents are relatively old. Do newer cell phones or electronic devices have different/no influence?

ALL FAR's are written in blood. I believe it is a FAR that cell phones may not be used inflight.

If you forget to do it, it happens, but just double check?

Topic being discussed in Tech Ops...
Electronic Interference? (by FrenchPilot Aug 30 2007 in Tech Ops)

And we have at least one trip report from an airline pilot where phones seem to have caused some trouble.
RE: For God's Sake, Switch Off Your Damn Cell Phones.. (by Pilotaydin Jan 12 2007 in Civil Aviation)?searchid=3196561&s=pilotaydin#3196561

Quoting B777Neuss (Reply 12): Do newer cell phones or electronic devices have different/no influence?

They may, but remember, the standards have to be held to the lowest common denominator.

99% of the phones out there may be totally compliant with FCC regs, and cause no interference whatsoever. The problem is, the remaining 1% presents an unacceptable (and, perhaps more importantly, unnecessary) risk.

It only takes one navigational glitch or avionics error to ruin everyone's day. Uncle Dave's sports scores, Francine's office gossip, and little Jennifer's texting can wait. They can catch up when they arrive safely on the ground.  


2H4

After talking with some flight crews, it really depends on the aircraft. Some pilots on Dash-8's forget (or not) to turn off their phones and they really don't care. For pilots on CRJ-200's they seem to only get a annoying buzzing or chirping sound in their headphones. They really didn't say it was a big issue but more of annoyance during flight.


I think it really has something to do with the electronics onboard and the type of phone.

Quoting 2H4 (Reply 10): The lesson? Follow the rules. They're there for a reason.

And during the time periods of the incidents you cite, that reason was not to jeopardize Airfone revenue.

Private jet pax use all kinds of electronic devices at all sorts of altitudes, this whole interference issue is absolute nonsense, particularly when you consider that cell phones operate mostly at 2 GHz, and NAV and ATC systems operate around 120 MHz.

Quoting DurangoMac (Reply 16): After talking with some flight crews, it really depends on the aircraft. Some pilots on Dash-8's forget (or not) to turn off their phones and they really don't care. For pilots on CRJ-200's they seem to only get a annoying buzzing or chirping sound in their headphones. They really didn't say it was a big issue but more of annoyance during flight. I think it really has something to do with the electronics onboard and the type of phone.

I've flown bot the CRJ and Dash 8, and had the same trouble with the same phone (becuase it was mine.. whops). It was pretty much exactly as described by Jamesbuk.

Quoting Iaddca (Reply 17): Private jet pax use all kinds of electronic devices at all sorts of altitudes, this whole interference issue is absolute nonsense, particularly when you consider that cell phones operate mostly at 2 GHz, and NAV and ATC systems operate around 120 MHz.

Thats fine and nice, and I can't argue the technical aspects as I have no training as an electrical engineer, but I have experienced first hand the interferance that cell phone causes on VHF. Its most easily detectable on the com radios, but these function just above the VOR and ILS freqs, so it is reasonable to assume that cell phones couls not only interfere with critical communication, but also navigation.

Quoting 2H4 (Reply 15): They may, but remember, the standards have to be held to the lowest common denominator. 99% of the phones out there may be totally compliant with FCC regs, and cause no interference whatsoever. The problem is, the remaining 1% presents an unacceptable (and, perhaps more importantly, unnecessary) risk.

And could you imagine how hard it would be for the FAA to compile a list of which cell phones are ok and which aren't, not to mention how hard it would make FA's jobs if they had to explain that this gentleman's cell phone is ok to use in flight, but this other passenger can't use his? It's a heck of a lot easier to say "no cell phones" and be done with it.

Quoting Iaddca (Reply 17): Private jet pax use all kinds of electronic devices at all sorts of altitudes,

The rule for cellphones applies to any aircraft, and it's an FCC law. If they're using 'all kinds' of devices, they're not using cellphones legally. They're also using broadband connections specifically designed for aircraft use.

Jimbo

Quoting Bond007 (Reply 20): and it's an FCC law

the rule applies only on commercial planes, and was the result of lobbying by GTE and the airlines in the 90s when Airfone was released

to his credit, FCC chief Martin has sought to overturn this nonsensical rule since he took office

Quoting Bond007 (Reply 20): The rule for cellphones applies to any aircraft

wrong, look it up

Quoting 2H4 (Reply 15): It only takes one navigational glitch or avionics error to ruin everyone's day

Please explain how a cell phone interferes with the nav system or avionics.

Quoting B777Neuss (Reply 12): Do newer cell phones or electronic devices have different/no influence?

newer cell phones operate at higher frequencies, so theoretically less chance for interference, but really there was never an issue with older, 800 MHz phones

Quoting Iaddca (Reply 22): Please explain how a cell phone interferes with the nav system or avionics.

A cell phone is an unshielded radio transmitter.

Every radio transmitter influences every radio receiver within range - even those on different frequencies and different bands. This influence or interference is usually so miniscule that we do not notice.

The radios, FMS and other navigation receivers on aircraft operate on very low power so are more easily influenced than stronger devices receiving more powerful signals such as in your home.

Will every cell phone interfere with the navigation equipment on an aircraft? Yes in every case.

Will it be enough to be noticed, or dangerous? Almost always the answer is no.

But the crew has no way to tell what will happen today and what will happen tomorrow.

Brand new cell phones are sold everyday which do not work correctly because their frequencies, their power, their transmission as incorrect. You never know when/ if your cell phone will be the one to cause problems. You never know if your aircraft will be the one where a critical error/ failure will occur.

Quoting Doug_Or (Reply 18): I have experienced first hand the interferance that cell phone causes on VHF

With VDL2 replacing ACARS, there's greater risk of interference from other aircraft while you're on the ground than from cell phone users on your own plane.

Quoting ASAFA (Reply 2): The phones get no signal at altitude

That is not true. If a cellphone is within range of a tower, even 6 miles up, it gets reception.

People use their cellphones in the lavatories all the time.

I can't remember exactly on what flight but I do remember hearing someone's cell phone go off in the middle. I want to say it was on a CO Express flight back around Christmas. Anyway, nothing happened but the FA did give a stern look down the aisle.

Wasn't there an episode of Mythbusters where they tested this? I seem to remember them testing it with a 737 and a Cessna or something close to that. The conclusion was that the cell phone caused problems for the Cessna but not for the 737 because the instrument panel and wires on a 737 are shielded but they arent on a Cessna. Now I know its not absolutely conclusive but it proved something.

Also what happened to EK allowing cell phones in flight. Did that ever come to fruition?

A lot of more modern phones are worse as they offer GPS signals too and the GPS on the aircraft can get false readings due to echo which give a slight off set for the reading and since the AP is following the GPS settings it can send you off track without you knowing unless you are referring to conventional instruments as well

Quoting RFields5421 (Reply 24): You never know when/ if your cell phone will be the one to cause problems. You never know if your aircraft will be the one where a critical error/ failure will occur.

LOL do you write copy for Dateline for one of those tv news shows where they try to scare people about everything?

Quoting RFields5421 (Reply 24): The radios, FMS and other navigation receivers on aircraft operate on very low power so are more easily influenced than stronger devices receiving more powerful signals such as in your home.

yet they have no problem with all the in-cabin wi-fi antennas currently installed on biz jets for ARINC or Inmarsat broadband service

If you watch Mythbusters, you'll see it can effect unprotected Navigation devices, but they cannot test it in the air, and the Feds are too cheap to see if there is a problem with Commercial a/c.

As they said in the episode, better safe than sorry.

I don't personally see a problem with it, modern Avionics are shielded, but hey, its still against the law, and for me, that is enough to remember to turn my cell phone to aircraft mode.

khelm

Quoting Iaddca (Reply 30): yet they have no problem with all the in-cabin wi-fi antennas currently installed on biz jets for ARINC or Inmarsat broadband service

Something tells me you work for a cell phone company, because your insistence that there is no possibility of any interference is laughable.

First, we are talking mostly OUT OF SPEC cell phones, in other words, cell phones that aren't working correctly. They exist, they are within "tolerances" for a manufacturer but might be dangerous to a plane.

Second, you cite examples like the one above, which are systems designed and tested not to interfere, and that operate at far lower power, and use that as proof that nothing can interfere with anything.

Wifi is a short range, low power technology that relies on relatively large antennas to perform. And by installing it within a plane, you decrease the power used by the computers trying to access it (vs. a computer that accidentally has wifi turned on and is "seeking" a signal).

This is why some companies want to allow cell phones in planes but want to do so by installing a retransmission system. This system will be tested and controlled, and it will cause all the cell phones in the plane to operate at a much lower power, decreasing the risk of any problems.

But right now, if you use your phone in flight, you are holding a high power transmitter that is actively bursting signal omni-direcitonally and has not been tested for signal and frequency leaks. Your claim it can't cause interference is based on nothing but your own word.

Quoting Ikramerica (Reply 32): Second, you cite examples like the one above, which are systems designed and tested not to interfere, and that operate at far lower power, and use that as proof that nothing can interfere with anything.

the proof I've offered a million times is biz jets, where every electronic device gets used at every imaginable altitude

and if you actually read what's been posted, rather than rush to a conclusion, my point all along is that it's not just cell phones, it's computers, PSPs, laptops etc - which is why the switch on at 10,000 foot rule is the biggest joke ever - its got everything with airlines not wanting to be sued because people weren't listening to the safety demo than interference suddenly dropping once the plane climbs above 10,000 feet

The only way that cell phones can be dangerous are if a person were to throw them at someone. Any electronics for that matter. It's that simple.

My friend's flight instructor told him, that cell phone bands are even on the same band of radio as Air traffic frequencies. The cell phone rule is there to get your attention, since many of us are just so addicted to our phones, do you really think everyone has put their phones off, I dont think so. Many people at church forget to put their phones off, even when reminded to do so.

Quoting Iaddca (Reply 30): LOL do you write copy for Dateline for one of those tv news shows where they try to scare people about everything?

Sarcasm like this can turn a thread into garbage. When we try to make this an educated discussion, comments like this really ruin it for everyone. However, RFields5421 is unarguably correct -- you never know when or if your cell phone will be the one to cause a problem. It's not intended to scare anyone, but rather to keep that point in mind next time you consider answering that call from your boss during flight.

Regardless of whether or not cell phones truly have an effect during flight, there is clearly an uncertainty about the possible hazard they propose. The degree of risk is evidently pretty low when using a cell phone in-flight, but safety in aviation (and other professions) involves eliminating every caliber of potential danger imaginable.

Quote: Carnegie Mellon Researchers Find Cell Phones Pose Greater Risk to Airplane Navigation Than Previously Believed "A study by Carnegie Mellon University researchers in the Department of Engineering and Public Policy (EPP) has found that cell phones and other portable electronic devices, like laptops and game-playing devices, can pose dangers to the normal operation of critical electronics on airplanes." ""We found that the risk posed by these portable devices is higher than previously believed," said Bill Strauss, who recently completed his Ph.D. in EPP at Carnegie Mellon. "These devices can disrupt normal operation of key cockpit instruments, especially Global Positioning System (GPS) receivers, which are increasingly vital for safe landings." Strauss is an expert in aircraft electromagnetic compatibility at the Naval Air Warfare Center in Patuxent River, Md." "The researchers found that on average one to four cell phone calls are typically made from every commercial flight in the northeast United States. Some of these calls are made during critical flight stages such as climb-out, or on final approach. This could cause accidents, the investigators report."

http://www.cmu.edu/PR/releases06/060228_cellphone.html

I look at this way: tubes of toothpaste are banned but cell phones are a-ok. If cell phones were such a danger, they'd be banned. The fact that they aren't seems to indicate that they aren't the risk that the airlines make them out to be.

I have a suspicion that the real reason is that the fast speed of an airplane messes up the cell towers and the phone companies don't know how to charge their customers.

Quoting Phoenixflyer (Reply 28): Wasn't there an episode of Mythbusters where they tested this? I seem to remember them testing it with a 737 and a Cessna or something close to that. The conclusion was that the cell phone caused problems for the Cessna but not for the 737 because the instrument panel and wires on a 737 are shielded but they arent on a Cessna. Now I know its not absolutely conclusive but it proved something.

I believe I saw that and they tested it on a gulfstream on the ground.

My opinion is that since my cell phone has the power to affect my computer speakers (which aren't transmitting any frequency) then they have the ability to affect computers in general.... I believe the stories of phones affecting Nav systems etc but I could see how It might be hit and miss sometimes depending on avionics and the type of aircraftl

Quoting Iaddca (Reply 22): Please explain how a cell phone interferes with the nav system or avionics.

It doesn't (in any meaningful way). It interferes with the signals the nav system and avioincs are trying to pick up. Since the avionics can't tell the difference, they can give bad data to the airplane.

Quoting Iaddca (Reply 33): which is why the switch on at 10,000 foot rule is the biggest joke ever - its got everything with airlines not wanting to be sued because people weren't listening to the safety demo than interference suddenly dropping once the plane climbs above 10,000 feet

This completely misses the point. Radio interference with nav signals happens, but it's minor. At cruise altitudes it's irrelevant. However, a commercial aircraft below 10,000 feet is either in takeoff or landing, when ILS/VOR/GPS accuracy is a huge deal.

Tom.

Quoting Iaddca (Reply 22): Please explain how a cell phone interferes with the nav system or avionics.

A better question would be how does a Gameboy interfere with an FMC?

Quoting 2H4 (Reply 10): I had fuel indications on the FMC going crazy on board the B737, that returned to normal when all electronic stuff in the back was switched off. I suspect a "Gameboy" electronic game device to have interfered, but this is no more than a guess.

Now I have never seen the wiring, etc. for an FMC, but how would even the signal from a cell phone interfere with fuel indications? Something doesn't seem right there. I could possibly understand lines across the screen, but changing the numbers sounds fishy.

On my X-Cntry's for my PPL, I used my cell phone to keep track of the time. No problems, although I didn't need to use the radio because I was flying in Class E airspace over some very boring areas of Arizona (no traffic, airports, etc.).

[Edited 2007-09-01 08:50:23]

Quoting Iaddca (Reply 22): Please explain how a cell phone interferes with the nav system or avionics.

What does it matter? If they distract and confuse the pilots in any way, shape, or form (which, clearly, they do), they present an unacceptable and unnecessary risk to the safety of flight.

Period.

2H4

Quoting Iaddca (Reply 21): the rule applies only on commercial planes, and was the result of lobbying by GTE and the airlines in the 90s when Airfone was released

In understand it's any use on "airborne aircraft", and had little or nothing to do wirh Airfone, but disruption to ground services.

Quoting Iaddca (Reply 21): to his credit, FCC chief Martin has sought to overturn this nonsensical rule since he took office

Actualy, just for commericial aircraft. The ban would still apply to any other.

Quoting Iaddca (Reply 21): wrong, look it up

I did, and could find nothing specific to "commercial aircraft".

If the reasoning behind the FCC ban is ground service disruption, it makes no difference whether it's a corporate jet or commercial.


Jimbo

But why would Ryanair and others plan to allow mobile conversation on board if it was that unsafe?

when i fly with my dad, and he has a new phone he turns on both of his phones and starts transferring the data, yet i believe he is in flight mode, but i dont know, i will try to remind him next time.

Quoting Iaddca (Reply 30): LOL do you write copy for Dateline for one of those tv news shows where they try to scare people about everything?

Nope - I was part of an EMI testing team in the US Navy for a while - both shipboard and on aircraft. It was before cellphones - but any transmister will cause stray EMI inside an aircraft.

Quoting Iaddca (Reply 30): yet they have no problem with all the in-cabin wi-fi antennas currently installed on biz jets for ARINC or Inmarsat broadband service

The key is the cell phone antenna is not part of the aircraft wiring system - nor is the laptop with it's wireless card enabled.

Anything with a speaker generates stray EMI radiation - but cell phones are quite powerful transmitters compared to most of the other electronic devices pax carry on aircraft.

Cell phones, laptop computers and such do interfere with bizjet equipment all the time in the US.

The company I work for now ordered that the CEO's Blackberry be replaced twice because of it's impact upon the navigation systems. During one trip from Australia to Majuro to Hawaii to the US, the pilot of the Bombardier Challenger ask the CEO to have the Blackberry to be locked away with no batteries after landing at Majuro.

When the CEO had powered it on the MAJ NDB swung 40 degrees off course about 50 miles out. Not a good result in that location.

We've had to replace IBM, Dell and Sony laptops whose wireless NICs caused issues. We've had to have cell phones replaced.

At the last NBAA gathering our chief pilot attended, there was a special seminar on how to detect issues from such devices. They are an issue in bizjets - but much easier to diagnose due to the knowledge of what the few passengers are using. In most cases the executive or pax is required to notify the crew/FA before powering up such a device. So they know to watch for possible issues.

Manufacturers cannot put enough shielding on aircraft to avoid all EMI from unplanned transmitters on board - the weight penalty would be severe. It would also greatly increase the complexity and expense of maintenance if every single wire on the aircraft had to be sheathed in a metal mesh to trap stray EMI.

Yes the navigation devices do have shielding - but they are still connected by wires to their antennas.

Every device with speakers generates EMI.

Every transmitter not part of the aircraft systems generates significant EMI

Every piece of wire is a receiving antenna.

Every EMI signal which contacts a receiving antenna wire interferes with the signals being carried on the wire.

The question is not do the devices interfere, but how much do they interfere?

With very rigid control of the specifications of transmitters in known locations the impact can be filtered and canceled.

If It was such a real issue then how is the below possible, even Airbus have run tests and they have never caused problems.

http://news.bbc.co.uk/1/hi/business/5298332.stm

http://www.pocket-lint.co.uk/news/ne...s-approval-for-mobile-phones.phtml

If they were that dangerous, they wouldn't let them in the cabin.

Quoting LAXspotter (Reply 35): The cell phone rule is there to get your attention, since many of us are just so addicted to our phones, do you really think everyone has put their phones off, I don't think so. Many people at church forget to put their phones off, even when reminded to do so.

I think an average of 10 to 20% of the people on board do not switch of their phone, some people forget to turn it of in the cabin, or have phones that are in their checked luggage.
I for one never switch of my phone because I think it is nonsense to do so. And no, it never works at 33.000ft, it will simply not pick up any signal.
For all the ones claiming it is unsafe to do so; would you honestly believe we are investing all this money in aviation safety and ridiculous liquid bans and security measures if you could simply turn on your phone and do harm?
As I am typing this message there are hundreds of cellphones flying around the world that are not switched off, but still nothing happens.

Quoting AirTranTUS (Reply 40): Now I have never seen the wiring, etc. for an FMC, but how would even the signal from a cell phone interfere with fuel indications?

Capacitance fuel gaging systems (all aircraft except the 777) are phenomenally sensitive...a change of 1 pF will change the fuel indication in the cockpit. For safety they're also very low power. As a result, the only way to avoid interference is to shield everything...the fuel quantity system would pick up radio signals all over the place if it wasn't shielded. It's not all unusual for those shields to be iffy at some spot...there are probably 6-8 connectors between the tank probes and the flight deck.

Tom.