View Full Version : CD players etc

Aerial Jock
6th Feb 2002, 23:56
There's been much discussion about the risks - theoretical and practical - posed by mobile phones aboard aircraft. Can anyone tell me about the widespread prohibition on the use of personal CD/Minidisc players and laptop pcs during t/o and landing?

I'm intrigued to know if this is adopted because of a known interference potential, or does it have more to do with thoughts of pax not hearing emergency PA calls and/or having evac impeded by clutter?

7th Feb 2002, 09:52
In 1992 the FAA asked the RTCA to investigate potential interference effects of portable electronic devices (PEDs) upon aircraft electronic systems. The terms of reference included developing appropriate methods of testing and to make recommendations on acceptable operating restrictions to apply to the use of PEDs aboard aircraft. The RTCA set up Special Committee SC-177 which developed tests, carried out testing of various electronic devices and published its recommendations in 1996. The reference document is "Portable Electronic Devices Carried On Board Aircraft" Document No. RTCA/DO-233 dated 20 August 1996 - a hefty document consisting of 160 pages of discussion, scientific appendixes and tables.

The report recommended that the FAA should modify FAR 91.21, Portable Electronic Devices so that . .(a) The use of any PED is prohibited in aircraft during any critical phase of flight.. .(b) The use of any PED which has the capability to intentionally transmit electromagnetic energy is prohibited in aircraft at all times unless testing has been conducted to ascertain its safe use.

The FAA accepted the recommendations and revised FARs accordingly. The JAA also included similar but more stringent requirements into the appropriate section of JARs.

So, the answer to the question is that the ruling is based upon empirical data collected by scientific investigation of the interference radiated from various PEDs - including CD Players. A mobile phone obviously falls within the definition of being capable of intentionally emitting electromagnetic radiation and is banned at all times. Portable CD Players have been demonstrated to radiate unintentionally and are therefore prohibited during critical phases of flight.

Airlines interpret the ruling in different ways because there is no set definition of a "critical phase of flight" The best definition would seem to be that a critical phase of flight occurs whenever the commander of the aircraft considers that the aircraft is in a critical phase of flight. In practice, individual Flight Operations Departments set a policy to be follwed by all its crews which is usually transmitted to the passengers by a policy statement in the In Flight Magazine or other convenient document.

**********************************. .Through difficulties to the cinema

Aerial Jock
7th Feb 2002, 13:38
Very helpful - thank you!

7th Feb 2002, 16:17
Jock, your last point in the original post is a very good one.

Even assuming that such devices don't interfere with aircraft systems, with the volume at which some people have their machines they'll never hear evacuation commands. If they're seated on an aisle they will then hinder other passengers. Further, having extra clutter on their laps will, even if they hear the commands, delay their evacuation at a time when seconds count.

On the basis of security alone, I am opposed to people having electronic devices in their carry-on baggage or on their person.

9th Feb 2002, 20:01

Just a thought, but assuming that an incident involving evacuation is unlikely to occur in cruise, I trust that you'd declare the incident as a critical phase of flight and have the cabin crew go around pulling peoples' headsets off in preparation for the landing?

As an avionics specialist I think that the issue is well overdone. The aircraft systems are far more likely to cause interference than a PED. In fact I believe that a lot of the unreproducable avionics defects that we suffer are caused by cross-interference between systems. Many avionics systems leak as much or more than the levels measured during the PED testing documented in RTCA/DO-233

**********************************. .Through difficulties to the cinema

10th Feb 2002, 06:47
"As an avionics specialist I think that the issue is well overdone"

(Rumour has it that) an Australian aircraft, very recently, started to porpoise _in cruise_. A different autopilot was tried, with no improvement. The third autopilot was tried, also with no improvement. The crew discovered 3 kids all using Gameboys (or something of that nature) in the rear of the aircraft. They were asked to turn them off... No problems occurred thereafter.

I'm no avionics "expert", but my money's on the Gameboys causing the problem <img src="tongue.gif" border="0"> Odds or no odds, electronic devices shouldn't be ignored.

Rgds.. .Q.

10th Feb 2002, 16:07
I used to fly an aeroplane that porpoised when the rear observer used their HF. A bit disconcerting at first.

10th Feb 2002, 16:29
Being a nuts and bolts engineer, my technical knowledge of avionics is limited to finding the big knob labelled ON-OFF and suchlike ... however, I found a useful article from Avionics Magazine, "Feedback over PEDs", April 2000, pp49. I have it scanned to archive if you don't have access to a copy elsewhere conveniently and can send it via email.... hopefully that isn't a dreadful contravention of copyright ...

10th Feb 2002, 17:34
Blacksheep, you're right, in that an announcement regarding evacuation is unlikely to occur in the cruise.

However, it is quite possible that an urgent safety announcement needs to be made. In that event, I would want to know that everyone has heard and understood it.

Since the aircraft's PA overrides the sound on all IFE systems, you may conclude there is a reason for it. Furthermore, given the range of choice on most IFE's nowadays, I see no reason why people need to listen to their own PED's, at least while on board.

Or does safety no longer come first?

As for "leakage" from aircraft avionics systems, granted that you can't make them all leak-proof. However, the manufacturers go a long way towards trying. The manufacturers of PED's don't even try. Another reason for banning them on board.

There is less reason for banning use of laptops in the cruise. Business travellers (and others) will often need the time to work during the flight, they don't block off the hearing, and their use is very much more obvious to the cabin crew than a PED, so they are more likely to know who to approach to have it turned off if the aircraft's systems start keeling over sideways. I do, however, feel that the cabin crew should be notified before pax use them - gives one a fighting chance!

10th Feb 2002, 21:12
The manufacturers of PEDs have to meet FCC radio interference regulations. You may find this hard to believe but they are much tighter than the regulations governing avionics. The RTCA document provides figures that were obtained from PEDs during testing. The measured EMI figures were, without exception, less than those specified in the TSO specifications for non-transmitting airborne equipment. The RTCA document also includes tables covering reports of in-flight occurences of suspected interference caused by PEDs. Not one of the reports was substantiated in post flight testing of the suspected PED. These are the grounds upon which I state my personal opinion. The report issued by the RTCA errs on the safe side, and although you may find my postion odd, I also believe this leads to the proper outcome - a revision of FARs. Safety isn't a matter of opinion, it is a matter of life and death.

Aerial Jock asked simply what were the grounds for the ban on PEDs. The answer is that the ban was based upon thorough scientific testing of various PEDs. That the results are the source of disagreement among specialists is hardly surprising but until more specific and detailed data is available, the FAA acted upon the best advice available.

. .That in turn leaves me in the incongruous situation where I do not use my portable CD Player on the aircraft even though I am personally convinced that it poses no risk. Rules are rules and I too would rather err on the side of caution, but without getting too excited about it.

For those who are privileged to fly around in aircraft with the latest IFE equipment then there is no need to "BYO" but as for the rest of us, well we must suffer in silence - in our neck of the woods they think that having replaced the pneumatic headsets with electric ones and attached television monitors to the ceiling they are running on the ragged edge of technology. <img src="rolleyes.gif" border="0">

**********************************. .Through difficulties to the cinema

13th Feb 2002, 09:08
Just after Sept 11 when all airports went completely mad about security. Women passengers weren't even allowed to take their handbags onboard. All cameras, cd players, walkmans and phones were conficated at the gate and checked into the hold. (This was at LGW).

When I asked a senior security person why all personal electronics were being considered as suspicious, he told me about something that had happened in Israel a few years ago:

A hitman had managed to secrete a tiny amount of semtex into his targets' mobile phone. The low energy microwave radiation emitted during the call would be enough to fire the detonator....then..Boom!

You can now take your phone with you on the aircraft, they just ask you to switch it off!

14th Feb 2002, 05:25
I recall flying back to the US just after Pan Am 103 went down over Lockerbie.

My batteries were taken from me by the security chaps - long before we reached the baggage check in at LHR.

Was that a knee jerk reaction, or do the x ray machine, scanners etc detect anything out of the ordinary with a battery, or number thereof?

Perhaps that is best left an unanswered question - for securities sake.

15th Feb 2002, 00:52
Just for info (I'm not entirely sure how relevant this is):

Amercian Eagle on their ERJ/135s have Pioneer CD players (same as in-car units) to play the announcement for the safety demo (only 1 CCM.). .As far as I could see, the unit remained switched on throughout the flight.

15th Feb 2002, 01:37
HuMonster, I assume you dont take any part in the commercial parts of running an airline. Otherwise, I think you will find that banning Laptops would be very unpopular. The people at the front of the bus pay your wages, not the oiks in the back. If we cant use our laptops then thats 8 hours on the company payroll wasted. We arent paid to sit on our arse looking out of the window all day - you are. As to the poster, thre removal of batterys appears to be a sdandard component of any operation kneejerk, most recently post 911, both LHR T1 and 3, were removing battteries from phones, laptops et al and placing in checked baggage. They took my battery from my notebook, nut thankfully the monkey screener, did not realise what the empower cable in my bag was for and let that through

Jon (V50) Gar

Pilot Pete
15th Feb 2002, 02:27

I think you'll find if you re-read HM's post that he was not calling for the banning of laptops.

Your posting comes accross as being quite arrogant and showing a distinct lack of knowledge of the pilots' role; seems strange that you are prepared to put your life in the hands of someone who is 'paid to sit on their arse looking out the window all day'.

I certainly wouldn't put my life in your hands.................


15th Feb 2002, 02:43
i wasnt offering you sex pete <img src="smile.gif" border="0"> Most laptops containg a CD system, many carriers have seen this as an issue, namley Lufthansa and on occasians SAS.

I have a great deal of respect for you guys, as a pax I have to. I should have said ' sitting on your arse all day looking of of the window pushing and pulling on a big stick between your legs all day'

I hope that makes ammends


16th Feb 2002, 09:15
V50, some of them only have a small stick to pull on but thats off-thread. <img src="tongue.gif" border="0">

Laptops contain CD Drives but there are relatively few models. Most models have been tested and found to be free of RF radiation. As you pointed out, the folks in the premium cabins pay more for their seats. So much so, that we now have seats with built in power outlets for PCs. Some may think that's a little odd in a situation where CD Players are banned, but the mighty dollar is King and rules are made to be bent.

As I pointed out earlier, I personally suspect there's more danger of RF Interference from on-board equipment than from carry on devices. The original RTCA investigation was commissioned in 1992 and the terms of reference were limited to carry on items only. Its time the RTCA or some other respected research group reviewed RTCA/DO-233 using terms of reference expanded to investigate ALL sources of EMI in aircraft cabins and recommend solutions. The outcome may then be used to address the current hypocritical situation concerning the use of carry on equipment aboard aircraft.


16th Feb 2002, 12:21
Certainly it would seem that newer generations of airline aircraft are more susceptible to RFI and EMC effects than valve-era things like the ancient old beasts which I fly!

What happened to that idea of building a properly certificated 'local' GSM base station into aeroplanes which would cause any switched on phones to radiate at their minimum power levels, reducing RFI risk and providing cellular facilities to the revenue earners?

Most 'interesting' self-made IFE system I ever saw was something which I caught my ground crew using on board the ac in flight. It consisted of a domestic TV set balanced on a table wired to the shaver socket via a mains cable running along the floor, a domestic VCR similarly rigged connected to the TV and external speakers on the overhead racks. On this dangerous lash-up they were watching illegal pornographic movies. Fun detector me had the whole thing dismantled and stowed away - and they were told to 'lose' the tapes........

16th Feb 2002, 15:28
V50, Pilot Pete is quite correct. Reread my post. I was explaining why there is very little reason for banning laptops, and several reasons for not doing so.

You then post several insults and repeat all the reasons I quoted.

You also display a very patronising attitude to the staff who serve you and keep you safe - not only the pilots but also the airport security staff.

What worries me is that whatever security measures are introduced, there will always be some smart-aleck passenger who thinks he knows better, or that the rules don't apply to him and that therefore he is entitled to endanger everyone around him... <img src="frown.gif" border="0">