BA038 and EMC - a thought experiment

[Self Loading Freight]

It was a long flight. Most of the passengers had been in China on business. As the a/c came into land, they were very aware that half the UK working day had already passed and it would be some time before they were back in the office. Some had forgotten to turn off their mobile phones, others had turned them on in expectation of picking up important messages as soon as they were on the ground, still others had been playing games or writing emails without flight mode enabled and had just slipped their mobiles into their pockets when the seatbelt light came on.

Among the active devices, five or six were 3G/HSPA, the rest GSM/2.5G. On late finals, the a/c was finally low and slow enough for the mobiles to make contact with the base stations that clustered around LHR; the Faraday cage of the hull no longer providing enough shielding to keep them isolated. But there was enough attenuation to make the handsets push their power up to compensate. Simultaneously, all the active devices in the cabin started link negotiation across three bands and many tens of MHz.

Whether the aviation cable shielding was inadequate by design or by degradation over time, it wasn't up to the job of keeping the high energy pulses out of the electronics. Bad data appeared, which the engine control computers refused to accept - or perhaps it was any one of a number of other interesting fault conditions that happen when the analogue reality underlying digital systems stops behaving itself. Unable to distinguish the valid commands from the front of the a/c, the controllers stuck to their last setting and waited for the situation to resolve itself. Which, shortly afterwards, it did...

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Fictional and simplistic, to be sure, and there's no indication that anything like this actually occurred with BA038. I think it's highly improbable. But however unlikely it is, the chances of something like it can only increase. There have been plenty of anectodal and more-or-less technical discussions about these issues already, but precious few solid conclusions.

So if it did happen, how could we tell? As far as I know, the passengers weren't asked about their mobile usage after the event - and it's doubtful that much useful would be learned had they been. "Yes, sir, I had been disobeying the safety rules about using my mobile shortly before the plane fell out of the sky, putting hundreds of people in mortal danger and writing off umpteen million pounds-worth of tin, to say nothing of the cost of subsequent disruption. Why do you ask?"

There will be interesting data in the records of the mobile operators, who will know what terminals registered with which cells along the flightpath and when. The signature of an airborne terminal will be distinctive and easy to extract from ground-based users, just from hand-off records alone.

That sort of information will be useful in general, for characterising the extent of illicit mobile operation, and I _think_ it doesn't need a warrant to be collected. If the mobile operators anonymise it, I'm certain there are no data protection issues, and the decision can then be made if an incident has occurred that the full details should be provided to investigators. It would certainly be relatively cheap to acquire.

Also, monitoring band usage on the ground near to the approaches would collect examples of bursts of activity which could be correlated with events elsewhere.

Finally, on-board parametric spectrum monitoring may provide more evidence, but that would be expensive and intrusive.

R

[bflyer]

Hi

A very interresting possibility, very frightning to say the least..but what i would like to ask any accident investigators...would this possibility be taken seriously as a probable cause or one of many causes that might have led to this incident....?

[XPMorten]

FYI, survey's show that between 10-25% of all mobile phones brought on board acf are not switched off during flight.
That's a whole lot of phones and landings each day
worldwide without any sign of problems..

M

[24victor]

Following your thought experiment you might want to look at where McBroons cavalcade was when BA38 was at 2 miles for the left. :cool:

[787FOCAL]

The jammers Mr. Brown convoy us to jam wireless and cell phones is only good for several hundred feet not two miles. :hmm:

[24victor]

That would be "several hundred feet" in all directions, including upwards. BA38 was reported as having the problem onset at 600 feet and two miles. I reckon 600 feet fits your "several hundred feet" criteria, which is by no means an absolute value given the vagaries of RF jammers. I'd be surprised if this was the cause, but not astounded.:)

[Intruder]

Just think... The theory becomes even more plausible if the fuel was contaminated with LEAD, and the tanks were lined with it, further reducing the signal... ;)

[pasoundman]

XPMorten
FYI, survey's show that between 10-25% of all mobile phones brought on board acf are not switched off during flight.
That's a whole lot of phones and landings each day
worldwide without any sign of problems..


Well ..... there have been various reports of problems that might be attributed to cellphones actually.

The thing is ...... whilst they may *generally* not present a problem all it needs is that 'one in a million' event and then you have a real problem. Unfortunately it's entirely unpredictable.

[dmussen]

From Australia (the Nanny Country)
Last thursday I was flying from Albany to Perth with Skywest in a little Fokker 50.
As we taxied for T/O the flight attendant piped up and asked that everyone carrying a mobile re-check that theirs was definitely switched off as the aircraft's avionics were being affected.
Not bad. Relativley low tech. piece of kit, the F50, but I would love to know why I have never heard of this before and I fly down the back a hell of a lot.:ok::ok:

[ACMS]

I've left my phone on in lighties before. You can here the noise as the mobile is "polling" ( at least that's what the Telstra Techs call it ) the network. It can be quite loud sometimes.
I have never seen it effect the Nav instruments whilst this was going on.

I've left in on more times than I should in the 777 too, nothing ever heard on the radios. I guess I'm a bit further from the aerial !!

[FairWeatherFlyer]

Just think... The theory becomes even more plausible if the fuel was contaminated with LEAD, and the tanks were lined with it, further reducing the signal...

You saying some 100/130 sneaked into those tanks? Interesting. I don't think that would protect it much... A couple of kids with an array of RFID zappers and pringle tubes could still take it out.

[rottenray]

" The jammers Mr. Brown convoy us to jam wireless and cell phones is only good for several hundred feet not two miles. "


Interesting thought: We've been assuming an avionics malfunction alone - what about a one-in-a-million coincidence of a loose shield ground somewhere on the a/c and a malfunctioning or mal-adjusted jammer nearby?

Some of the jammers are actually quite powerful and their antenna array is a reasonable facsimile of a regular cellular tower (although designed for much higher power levels), which means it's lobed for horizontal radiation rather than vertical radiation. Tipping it a few degrees could easily put the beam at 600 agl...

[Kiwiguy]

Self Loading freight your scenario is bang on.

I was itching to post this scenario immediately when the aircraft crashed, but the website was down and I've been away from home for a week.


So if it did happen, how could we tell? As far as I know, the passengers weren't asked about their mobile usage after the event - and it's doubtful that much useful would be learned had they been.


From 2000-2002 I was baggage handling for Air New Zealand which expressly forbids cellphone use in the air, in accordance with NZ CAA policy.

In my personal experience however in the baggage hall cell phones were constantly ringing inside luggage sitting on baggage trolleys awaiting loading on planes. As a pilot I was aware of the EMC issues and made attempts to locate ringing cell phones (without success), but more importantly my efforts drew derision from workmates and foremen who couldn't care less.

Air New Zealand itself didn't want to know and couldn't care less either. Incidentally Air NZ now operates the Boeing 777 too.

You may prevent passengers in the cabin using cell phones, but you can't prevent cell phones in baggage responding to incoming calls. I am almost certain this scenario is the only one which will fit the facts.

When a cell phone receives a call from a cell tower the cell phone calls the tower back whilst the phone is ringing and thus it is not necessary for someone to actively make a call. Cell phones operate passively too.

The BA 777 as I understood the news a week ago had sufficient fuel and both engines quit simultaneously which is an impossibility from fuel contamination from two different fuel tanks at the identical same moment.

Couple of points to ponder: Let us not forget the Martinair 757 several years ago which lost all it's electronics and went through an excursion before computers came back online.

Let us not forget the Egyptair 767 flight 990 out of JFK which off Maine disconnected autopilot and went on a wild roller coaster ride to a watery grave.

Let me throw another less well known CFIT crash into the mix. One which NZ Civil Aviation Authority and the NZ Police concealed from the wider aviation community:

In about June or July 1995 on IFR appraoch to PMR a Dash 8-100 of Ansett NZ was flown into terrain on approach with remarkably few casualties.

Notwithstanding that the radio altimeter aerials and their warning stencils were painted over some months earlier. Notwithstanding that the RHMG uplock latch was worn beyong tolerances and was not repaired according to service bulletins. Notwithstanding that NZCAA permitted in the airline's Ops manual an instrument approach to be conducted with the distraction of gear failure...

Notwithstanding all of the above...

Captain Gary Sotheran testified that the radio altimeter display flipped 1,000ft quite suddenly as he watched it. Nobody believed him.

NZ Police used cockpit voice recordings to prosecute him for manslaughter, but what they concealed was that Police investigations uncovered evidence of a cell phone call being made by a passenger inside the cabin during the instrument approach.

The case was abandoned for other unrelated reasons.

It was a television news programme which leaked information which ought to have been relevant to the international aviation community. An Ansett NZ call centre operator at Christchurch by the name Cauldwell reported to Police that she had a call from an irate passenger before the time of impact complaining about being delayed by problems with the undercarriage.

Captain Sotheran was in all likelihood telling the truth that his radio altimeter flipped 1,000 ft. He was made a scapegoat for an issue the authorities and airplane manufacturers would probably rather the public not discover.

This I believe was proof positive that cell phone use interferes with flight instruments and does cause disasters.

We do need a debate on this issue, but I assure you Boeing and Airbus don't want that debate. Nor do the airlines.

What really stands out from this is the potential for terrorists to plant cell phones on flights and use this as an EMP weapon to down aircraft on finals.

[Self Loading Freight]

ECM isn't the only source of unexpected high power RF. As a radio ham, I'm allowed to run a few hundred watts on a wide selection of bands from shortwave to microwave, and to do it in a large number of interesting ways - including mobile. There are health and safety rules about RF exposure which rule out being too antisocial, but I - and I guess most hams - are a bit hazy about those and wouldn't know how to apply them properly. They're certainly not part of the licence requirements, nor are we expected to demonstrate knowledge or practical abilities in that area. (The implications of this are probably best left for another forum!).

The upshot of this is that equipment designers and regulators should not - as far as I'm aware, do not - assume that the RF environment outside an aircraft is uniformly benign. Even if they don't think it likely that a bunch of radio nuts will be setting up a moonbounce experiment beneath the approach at LHR, it's worth thinking about the security implications of having stuff vulnerable to attacks from hostile elements with the nous to knock up some form of directed energy weapon. Fortunately, the physics of airframes provides a very good first line of defence. I doubt any Prime Ministerial ECM that wasn't going around knocking out car electronics on the road around the convoy would trouble a 777 - and in any case, that sort of ECM isn't there to make ordinary electronics malfunction.

I'm more interested in finding ways to work out whether consumer electronics does cause problems, as gathering evidence for this ahead of a serious accident will be the only way to influence the industry to work towards a solution - which, as I've said, will probably be some sort of self-certifying regulatory regime.

R

[threemiles]

From Australia (the Nanny Country)
Last thursday I was flying from Albany to Perth with Skywest in a little Fokker 50.
As we taxied for T/O the flight attendant piped up and asked that everyone carrying a mobile re-check that theirs was definitely switched off as the aircraft's avionics were being affected.
Not bad. Relativley low tech. piece of kit, the F50, but I would love to know why I have never heard of this before and I fly down the back a hell of a lot

The pilots of the low tech VHF receivers of this kit were bothered by the papappapapap in their headsets. So they thought it is good time to let paxes switch the mobiles off.

[A330AV8R]

its a 777 :}

[ianwood]

I am not a RF engineer and only an amateur pilot but I feel fairly confident in saying:

RF interference on internal inter-system aircraft communications would require power output well beyond your average mobile phone to make any impact (especially on digital systems which generally cope better with background noise and random signalling errors than analog systems).

In order to influence signals on digital circuits, the RF signal would have to be powerful enough to significantly alter the voltage on a wire at specific intervals.

As a very crude ad hoc experiment, you can open up your home computer and place your mobile in there and then call it and text it repeatedly. See if anything odd happens on your computer. You may get the characteristic GSM warble on your computer speakers and even on the screen (if its analog) but the computer will happily keep working. With nearly direct contact inside the computer, the phone is posing much more RF to the computer's unprotected internal bits than a passenger's phone several feet and surfaces away from aircraft systems and wiring. That and hopefully the 777 uses more resilient hardware and software than your average Windows XP computer!

If RF issues did occur on BA038 and assuming the proper instrumentation in the logging systems, there would be something similar to erroneous CRC errors and other such "bad value" errors.

More of a concern would be RF from outside the aircraft, a concentrated EM pulse for example.