No, I don't think you understand what "empirical evidence" means.

If cell phones do interfere with controls and navigation systems, they do not do so consistently or frequently. The sporadic nature of the suspected incidents strongly suggests that it is the type of problem which you are unlikely to be able to repeat just "by calling the phone again". That doesn't mean that it might (I stress the word "might") not be a real problem posing a real risk.

As to frequency, I do not pretend to be an expert on this - I can only draw attention to what I've learned from reading other sources. So I can't put this forward on the basis that these are THE three or four incidents which prove the case. (I don't think it is proven, by the way, in case anyone's forgotten.) I have personally also heard oral anecdotes from flight crew about suspected incidents they have been involved in, although I do not know whether they reported them formally or whether there were any formal investigations or reports. I do believe, though, that the haphazard way that these things come to light and the absence of any systematic recording of these incidents mean that there are likely to be rather more than these three or four of which I do know.

These incidents are cases which have been investigated. This means that other potential causes will also have been looked at, and discounted for one reason or another. Much air accident investigation consists of examining possibilities and sequentially eliminating the ones which do not fit the evidence. So obviously the investigators have not eliminated a cell phone as the cause of these incidents, but they seem to have eliminated other potential causes.

So what does all this show? There are incidents which suggest that there is a real possibility that cell phones may interfere with aircraft controls and navigation. It is obviously possible that an interference with controls may cause an accident, if it occurs at a critical phase of flight and the crew cannot maintain control. It also demonstrates that the risk of this occurring is low. The combination of low risk but potentially catastrophic consequences means that there's no cause for hysteria, but at the same time the airlines are wise to adopt a policy that cell phones must be off during flight - and to enforce it as far as they can. Particularly as there's very seldom any NECESSITY for cell phones to be used during flight.

I don't know why anyone should think that "proof" should be necessary before any action is taken to deal with the safety hazard. I personally would rather that this straightforward action was done unless and until the link can be DISproved, than run the risk of the link finally being proved by a bent aircraft and dead bodies. Too many safety lessons have had to be learnt that way in the past. We've got a chance to avoid it on this one.

Because we only have so much time, money, and effort in this world and it is wrong to waste it on things that lots of people want to believe cause problems, but don't actually.

I really hate these kinds of arguments, as there is just no getting through. Many people instinctively believe that cell phones cause a problem and so they are quick to point to a cell phone if a random problem occurs. It is the very fact that the fallacy sounds reasonable that makes it so inisidious. Combine that with the fact that you can wrap yourself in images of dead bodies (like a jury can be swayed by how severe a crime was even though it has nothing to do with who committed it), and common sense and the truth just can't win.

I can come up with amusing reasons all day long as to why the kind of "empirical evidence" you cite doesn't demonstrate anything (and I thought the dog barking example was a great one!), but you won't listen, so I'm going to move on now.

Fortunately, the argument is moot as the FCC has been able to prove that airborne cell phones disrupt the cellular network, so they should be banned, and there's no point in arguing over the specific reasons.

Well, everyone else can read and judge for themselves.

[edited to add:]

Robb's approach, though, would lead to conclusions like there being no need for Boeing to redesign the B737's rudder PCU system completely. After all, there's no proof that it's caused any accidents - only the elimination of all other possible causes.

[This message has been edited by Globaliser (edited 09-12-2002).]

Couldn't agree with you more, robb.
But on whom does the burden of proof lie?

Is there proof that there are no safety issues from using cellphones on civil aircraft? If so, fine - I'd be very interested to learn of it.

If there isn't such proof, then on this issue I think it's guilty until proven innocent... http://www.flyertalk.com/travel/fttr...orum/smile.gif

[This message has been edited by Wingnut (edited 09-12-2002).]

That's an easy one. The burden of proof always lies on the positive, never the negative (since you can't prove a negative).

I could also ask you to prove that women aren't the cause of all crashes or that mailmen don't leave because of dogs and it would be impossible to prove.

I always thought that this rule was a mandate primarily driven by the cellphone lobby. In flight, at that altitude, the signal can hop between cells more quickly than the carriers equipment can track, effectively allowing free phone calls. Maybe this is urban legend, but that was what I was told by a wireless industry person a while back, though maybe the technologies have also changed to track and bill for signal.

As well as being rather facile... http://www.flyertalk.com/travel/fttr...orum/smile.gif

[This message has been edited by Wingnut (edited 09-14-2002).]

The system can track airborne cell calls just fine. Billing is not a problem.

The problem is that the cell system was designed for ground based phones and is based on the line-of-sight distances of a ground based phone. Each cell site uses a set of channels that is not used by any other cell sites within line-of-sight range of that cell. Those channels are used again on cell sites that are sufficiently distant so as not to cause interference. When you elevate a phone you dramtically increase it's line-of-sight distance so now the phone can reach dozens, or even hundreds if over a large city, cells that use the same channels. Those other cells will hear the elevated cell phone and will not be able to use that channel do to the interference so instead of your call using one channel at one cell site it's block that channel at dozens, or possible hundreds, of cell sites. The system just doesn't have the capacity to serve all of the users if there were very many airborne phones. We already get enough dropped called due to cells running out of capacity (ever have a call drop when the signal strength is good?), we don't need more.

That's the reason for the FCC ban. The cell system simply wasn't designed for airborne use. The FAA's prohibition is for a different reason. The FAA prohibits the use of any electronic device which hasn't been determined to not cause interference. Since cell phones are intentional transmitters they can cause interference, and occasionally do, so they can't be used in flight. Here is the FAA regulation which applies:

14CFR121.306 Portable electronic devices.

(a) Except as provided in paragraph (b) of this section, no person may operate, nor may any operator or pilot in command of an aircraft allow the operation of, any portable electronic device on any U.S.-registered civil aircraft operating under this part.

(b) Paragraph (a) of this section does not apply to --
(1) Portable voice recorders;
(2) Hearing aids;
(3) Heart pacemakers;
(4) Electric shavers; or
(5) Any other portable electronic device that the part 119 certificate holder has determined will not cause interference with the navigation or communication system of the aircraft on which it is to be used.

(c) The determination required by paragraph (b)(5) of this section shall be made by that part 119 certificate holder operating the particular device to be used.

Here's some non-anecdotal first hand evidence that will hopefully answer the non-believers.

I took a passenger up in my light aircraft who accidentally left his mobile phone on. When it rang (we couldn't actually hear it over the engine) all comms with the tower were drowned out. The distortion sounded like a phone ringing so I asked him, he dug it out, found it was ringing and switched it off.

Away from controlled airspace, we conducted a brief test with our two phones, including ringing one from the other (different networks so different transmitters). There was serious VHF radio interference when we first switched a phone on while it hunted for a transmitter, and when it rang. The interference started about 2-3 seconds before the phone actually rang. Undoubtedly the worst was the WAP phone, which caused interference every time it was transmitting data.

So there. Don't use phones in planes! And do double-check your phone is off before boarding. I always do now.

Oh-so-Thanx for the info. I conclude from everything above that the risk is enough to forbid gambling with 100s of lives. However, I respect the decision of some doomed 9-11 PXX to call, as they had little to lose. http://www.flyertalk.com/travel/fttr...orum/frown.gif (God rest their souls!) Also, we all know more about the final minutes because of it.

BIG ?: How do Sprint & AT&T Airfones avoid such interference?

------------------
Play the travel game 3 vacations into the future! :)

In an emergency you do what you have to do. Still, the majority of those "cell phone" calls from the hijacked airplanes were actually calls using the airplane's air phones. It is rather difficult to get, or keep, a call from inside of a metal airliner in flight. Not impossible, but difficult.

Two types of interference.

They avoid interference with aircraft systems because they are installed in the airplane. The installation is designed and tested to ensure that it doesn't interfere with other aircraft systems. This process is the same that any new peice of avionics goes through to get certified.

They avoid interference with the ground cell network because those phones don't use the ground cell network. The airborne phones rely on a completely separate network of ground stations and operate on different frequencies. The air phone network is a network designed specifically to serve airliners in flight so there isn't a problem.

The real problem with the air phones is that they are so rarely used. I say recently that they average only two or three calls per day PER AIRPLANE!

>>>The real problem with the air phones is that they are so rarely used. I say recently that they average only two or three calls per day PER AIRPLANE!

That is because they are so expensive to use. At ten cents per minute with no initial or operator assist fee, those airphones would be in use all flight long.

Travel tips:
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[This message has been edited by AllanJ (edited 09-15-2002).]

But Brendan, surely you realize that "I" am soooooo important that the off chance that "I" may interfere w/the operations of the plane is of no matter to me, excuse me while I take this call http://www.flyertalk.com/travel/fttravel_forum/wink.gif

But Sweet Willie, surely "you" are sooooo important that you have someone to take your calls for you? http://www.flyertalk.com/travel/fttr...um/biggrin.gif

It's a truism, but the more important a person is, the more difficult they are to get hold of... http://www.flyertalk.com/travel/fttravel_forum/wink.gif