Dear Colleagues

Something which is sure to drive you crazy is having someone sitting next to you in an aircraft yammering away into their mobile phone. At this stage, as we all know, mobile phones are banned from use on a plane but there is a strong move to unban them for aircraft usage.

One myth that is prevalent is that mobile phones are banned because they disrupt an aircraft’s sensitive avionic systems because of their electromagnetic radiation. Not so at all. The ban on mobile phones really exists to prevent the phones disrupting the phone companies receiving equipment on the ground (and causing problems with billing).

There is a Huge Amount of Interference at Present
Theoretically, it is possible for any item of electrical equipment to interfere with the aircraft’s navigation equipment and delicate instrumentation. Specifically, cables and power supplies to recharge your computers, tablets and iPhones are probably the worst offenders. Transmitters such as mobile phones have unpredictable emissions which theoretically could impact on an aircraft’s avionic systems. And we have all heard about the reports (admittedly all anecdotal) of aircraft instruments being affected by these mobile electronic devices causing aircraft to suddenly lose or gain altitude with the possibility of a crash.

However, extensive research by manufacturers such as Boeing and Airbus who have bombarded their test aircraft with electromagnetic radiation with ranges of intensity equivalent to that of a mobile phone show no demonstrated impact whatsoever.

We also know that there are thousands of passengers using their phones surreptitiously during take-off or landing or leaving their computers, phones and other devices powered on. But there is still no concrete evidence that any of these have caused a problem with an aircraft (although admittedly lots of anecdotal commentary about how hazardous for an aircraft it is).

The Big Challenge Remains
The real challenge with a mobile phone is that in an aircraft flying overhead, it could be in reach of a number of mobile phone masts using the same channels. This could result in unreliable calls (as calls will be dropped) and would also confuse the overall system’s network management software (trying to identify exactly where a phone was located). The other problem is that phones could be travelling in an aircraft close to the speed of sound – thus not registering on a network and not allowing calls to be made.

Other Worrying Problems in the Air
Two other reasons why mobile phones may not be desirable on a plane are sometimes mentioned:

During take-off and landing or indeed turbulence in an aircraft the mobile phone can be a missile travelling at a high speed that can seriously hurt a passenger if flying around the cabin. So not recommended for this one reason.

Mobile phones can create excessive electromagnetic radiation. Aircrafts are essentially Faraday cages. With a number of mobile phones active in an aircraft cabin, there is a ferocious amount of energy radiated (and reflected about) in a confined space. Surely not a good thing for humans (and their living tissues). Children and infants are probably even more vulnerable to this level of radiation.

At this Stage - No Decisions
Although there has been a drive to relax the standards; nothing has been agreed upon as yet. The only thing that has been allowed is the creation of pico-cells onboard aircraft thus allowing passengers to use the Internet. These pico cells connect to a satellite and thus to a ground station. These services are still extraordinarily expensive. So likely to deter any passenger from yammering away too long on their phone and waking you up from your fitful slumber. Also these pico nets (based around Wifi) would result in less radiation (as per an earlier comment above).

Harold Geneen is quite right when he remarks: We must not be hampered by yesterday's myths in concentrating on today's needs.

Thanks to the Economist for an interesting article on the topic: Phones up in the air.

Yours in engineering learning


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