Rebone Sesoko asked:
Fact of fiction: do cell phones affect the operations of aeroplanes and why is it that some airlines allow the use of cell phones while airborne?
Dominic - There are essentially three reasons which are cited for why people havenít been allowed to use phones on aircrafts up until now. The first one is that there have been suggestions that the radio waves from the mobile phones can interfere with the operation of the aircraft. Secondly, it actually causes problems for the cell phone networks because phones work by finding out which transmitter mast is closest to the phone and then linking to that mast. Now if you're up in the air, you can see an awful lot of masts and the network can't actually decide which mast to attach to. And the third problem is the social aspect of it being rather anti-social to be shouting into your phone when you're in the air, on an aeroplane.
Chris - People do that in my train all the time, It doesnít seem to bother them!
Dominic - Yes, but of course, with the noise of the engines, you going to have to shout quite loud to speak to somebody in an aeroplane. Now in fact, the evidence that phones interfere with aircrafts is very weak. There have been studies done, certainly by Boeing, to look at flying aircrafts with and without phones on-board and there was some very weak evidence that the planes with phones on-board may have had slightly more incidents, but it was so weak, it was probably just down to chance. So I think most airlines now donít believe that phones do interfere with aircrafts and you can get around the problem of having to decide which mast to attach to by having a transmitter on-board the aeroplane which uses the aeroplaneís own communication systems to route your call to whatever network you're using.
Chris - Brilliant! Thank you, Dominic. I shall use my phone with impunity on the aeroplane and refer them to you if they tell me off.
There are numerous systems on an aeroplane that can be affected by electromagnetic radiation. Mobile phones emit very high levels in specific frequency bands and these certainly could affect some of these systems. Basically it is a cautious response to maintain safety. It takes a lot of effort to thoroughly rule out any possible problems from multiple use of mobile phones being operated on a plane. The aircraft's equipment is probably designed with a certain amount of shielding and will have some specification regarding interference levels. This may well be being exceeded in some cases but is also necessarily cautious in specification. It is up to individual airlines whether they choose to perform practical tests to satisfy themselves that the radiation from mobiles is safe but the consequence of being wrong may be very high.
At cruising altitude, there is time to recover in the unlikely event of interference; on takeoff and landing, there is no time to react. Another reason for turning off electronic devices during takeoff and landing (even non-transmitting ones) is so that people will hear safety announcements.
It would seem like the hardware to wire up an airplane with a cell phone repeater would be relatively inexpensive.
You may be right Clifford. It comes down to marketing I think. The systems are based on the Iridium satellite system and they have, so far, laid out their stall for a relatively small market with high charges per kbyte of data. It seems they have sufficient capacity to handle more but they maybe concerned about how to offer cheaper rates without damaging their existing lucrative income. It is, to some extent, a chicken and egg situation. There is an upgrade coming in 2014 so we will see what happens then. graham.d, Mon, 13th Aug 2012
With respect to Dominic, as far as I know Boeing reached no such conclusion that use of mobiles on an aircraft was completely benign or that interference with systems has been exaggerated...