View Full Version : Airline greed or ignorance?

15th Apr 2002, 15:29
Is there really ANY justification for the continued ban on use of mobile 'phones on aircraft? Various studies have shown no interference with aircraft systems (see ZDnet report (http://news.zdnet.co.uk/story/0,,t269-s2074198,00.html) from 1999), even under deliberately intense conditions, so why the ongoing ban?

Airline revenue from "air-phone" use?

Justified fears of interference with aircraft systems?

Plain ignorance?


15th Apr 2002, 16:08
At the risk of having this thread moved to Tech Log (first time a post has ever been moved out of JetBlast - they usually get moved in here from other forums!):

I don't know about airliners, but I know that mobile phones do interfere with the radios on general aviation aircraft. If I (or one of my passengers) forgets to turn a mobile phone off, it doesn't usually take long before the tell-tale "beep ba-ba-beep ba-ba-beep" noise comes over the headset. Hardly life-threatening, but definitely noticeable.

Also, I believe that using a mobile phone in the air screws up the phone network, because it's within range of a whole load more receivers than you'd normally expect.

Ok, can we get back to the usual inane JetBlast posts now please :D :D :D


15th Apr 2002, 17:04
Quite apart from the matter of interference, and there is substantial circumstantial evidence that they DO interfere with some aircraft systems, particularly older ones, mobile phones are designed for ground-level use (except satcom phones), and the higher levels of attenuation you get.

Put simply, you are normally being served by only one (or occasionally two) repeater stations. The click/beep sound you hear on the car radio as you drive along is usually the interference from the phone as it signs off from one station and pick up with the next, or loses one, finds it again and signs on.

In the air, all the repeater stations for miles around can "see" your phone, and all try to provide a service. Since one repeater station can only provide a service for a limited number of phones, you are therefore tying up rather more than your fair share. Just a few airborne phones would completely seize the network for everyone else.

From the flight deck, I have often heard that click/beep sound on the intercom from mobile phones in the cabin which have been left switched on. If it interferes with the intercom, I do not like to take a risk on them not interfering with other systems, and ask the owners to switch them off.

Does that answer the question?

Tin Kicker
15th Apr 2002, 20:04
Saw this on ATI, might answer your question Kilted.

Phone interference exceeds safety limits: UK CAA
David Morrow, London (17May00, 14:46 GMT, 729 words)

UK Civil Aviation Authority researchers are claiming that an investigation into mobile telephone interference has proven conclusively that telephones have the potential to disrupt aircraft systems.

Ground tests were conducted on two aircraft - a Virgin Atlantic Airways Boeing 747-200 and a British Airways Boeing 737-200 - at London Gatwick Airport in February.

CAA Safety Regulation Group avionics section head Dan Hawkes says: "The tests show that a mobile telephone used near an aircraft's flight deck or avionics equipment bay will produce interference that exceeds the certification levels for some equipment."

In a second phase of the research, which is expected to be conducted later this year, various types of avionics equipment will be exposed to increasing levels of interference to determine the point at which the equipment fails to operate correctly.

Prohibition on the use of mobile telephones in flight is standard practice among airlines. But there has been little direct evidence about the effects of telephones on aircraft systems.

In its report on the first stage of the investigation, the CAA states: "Although reports of suspected interference effects are regularly received by the regulatory authorities, proof that a portable telephone was the actual cause of an incident has proved elusive."

This is partly due to the operating characteristics of mobile telephones, which tend to switch frequencies and adjust transmitting power levels automatically.

Reports from pilots have blamed telephones, pagers and similar electronic devices for false readings from direction indicators, radio altimeters, instrument landing system avionics, and collision-avoidance systems. Pilot have also suspected radio interference of causing a number of uncommanded aircraft manoeuvres, as well as generating problems with air-ground communication.

Dan Hawkes was among witnesses called to testify in an unprecedented UK court case last year, in which a passenger was found guilty of endangering a British Airways Boeing 737 after refusing to turn off his mobile telephone.

While the CAA admits that the evidence given was purely anecdotal, a spokesman for the authority denies that the need for firm evidence in such legal proceedings prompted the research programme, stating: "We've warranted our ban on telephones because we could not rule out a threat. But we've always acknowledged that we need to prove the link scientifically."

International standards are in place to approve aircraft equipment under conditions of interference - the European Organisation for Civil Aviation Equipment's ED-14 and its US equivalent, the Radio Technical Commission on Aeronautics' DO-160.

Although the standards have been updated four times - most recently in 1997 - equipment certified as meeting earlier criteria is still being fitted in new aircraft.

Aircraft systems approved before December 1989, for example, did not need to undergo resistance tests for high-frequency interference - specifically the 1,782MHz frequency used by mobile telephones.

During the Gatwick tests, researchers measured interference levels on the flight deck and in the avionics bay of each aircraft, caused by telephone transmissions in the forward and rear passenger cabins, and - in the case of the Boeing 747 - the upper deck.

All three of the common mobile telephone transmitting frequencies - 381MHz, 881MHz and 1,782MHz - were used in the tests.

Researchers discovered that standing-wave effects generated by signal reflections inside the aircraft caused interference levels to vary by up to a factor of three. Similarly, the level of interference varied when the transmitter was moved around the passenger cabin, even across short distances.

If people stood in the path of the transmissions, the strength of the transmitted signal was found to fall. The CAA says: "This indicates that the number of passengers on an aircraft would affect interference levels."

Internal cabin doors built from composite materials, however, did not block the telephone transmissions.

While transmissions from the rear cabin of the Boeing 747 were found to be almost undetectable in the flight deck, the CAA points out that such transmissions still had the potential to affect equipment installed in the rear of the aircraft.

The CAA concludes that interference from a telephone used near the flight deck or avionics bay "will exceed demonstrated susceptibility levels" for equipment approved before the July 1984 standards revision.

It adds: "Since equipment qualified to these standards is installed in older aircraft, and can be installed - and is known to be installed - in newly-built aircraft, current policy for restricting the use of portable telephones on all aircraft will need to remain in force."

Source: Air Transport Intelligence news

Kalium Chloride
15th Apr 2002, 20:11
Just an observation, but what are those pretty pictures on the ZD Net website? They look like mobile phone company adverts to me :D

Tin Kicker
15th Apr 2002, 22:29
If you're still not convinced Kilted you should look at the number of commercial aircraft incidents being reported to NASA's ASRS database (under Passenger Electronic Devices reports).

15th Apr 2002, 22:43
Many thanks all for the replies, I will follow up the references before commenting further, but, just to expose my dearth of technical knowledge even further :rolleyes: why do similar regulations prohibit the use of CD players?

I can understand the potential interference of transmitting devices, but those that are not intended to transmit? Perhaps some of you techies can enlighten me :)

15th Apr 2002, 23:13
Personal Electronic Devices (PED's), not being linked in to the aircraft's PA system block out external sound, and don't, for example, provide you with important safety announcements. The law requires that all passengers have various announcements made to them. The airline therefore prohibit the use of devices which would prevent that.

You want to block out an evacuation announcement? I don't.

Tin Kicker
15th Apr 2002, 23:26
Not every airline bans CD-players.

Germany changed its laws on electronic devices two years ago, saying that CD and DVD players were not a threat to aircraft systems. Lufthansa and LTU both allow CD players to be used in flight.

Hand Solo
15th Apr 2002, 23:51
But do they allow them to be used during take off and landing? Personally I'm all in favour of a ban on mobile phones in flight. Its bad enough having to put up with them on the train and in restaurants without having your flight disturbed by someone yelling hello? hello? hello.....you're breaking up...hello? every five minutes.

16th Apr 2002, 00:01
CD players do contain a frequency generator. And as such give off electromagnetic energy.

16th Apr 2002, 04:00
Didnt a passenger on the recent Air China flight that crashed used a mobile phone to inform authorities they were crashing?

16th Apr 2002, 09:11
One of the major keys to this is that mentioned earlier....the transmission footprint of the phone.

From ground level the phone can transmit only a short distance and will be picked up by several local receiver bases, each of which is an independent transmitter/receiver cell, hence the term "cellphone". The system then allocates a connection to the system to that phone from the strongest cell connection.

As you drive in your car you will often hear the "dum dee dum deedum" sound of your phone logging on to a new cell as you move around.

Imagine doing this with no line of site clutter to absorb/scatter signals and a ground speed in excess of 500mph. Your phone could try to log on to half the cells in the country in a one hour flight. It causes lots of hassle for the system operators and that is before it starts anoying the hell out of everyone on the plane by playing the "dum dee dumdee" tune through their cd player :D

Send Clowns
16th Apr 2002, 13:57
If anyone is really thinking that a mobile phone can't interfere, just think about the car stereo. They not only make that distinctive sound when the radio is on, but also when a tape or CD is being played. Therefore the signal is sufficiently powerful to interfere with an audio-frequency amplifier. Surely it must also be capable of disturbing the sensitive radio-frequency amplifiers in various aircraft r.f. receiver systems.

All electronic goods give out electro-magnetic waves. Damaged products can give out unexpected level, well above design tolerances. R.f. receivers designed to make sense of weak signals (some aircraft systems look for signals so weak they are below background noise levels) can be disturbd by e.-m. radiation, therefore electronic goods should not be used at critical stages of fight, powerful r.f. transmitters (mobile phones) should not be used in flight at all.