Personal Electronics May Indeed Disrupt Avionics 505
mattrwilliams writes "There is a growing body of anecdotal evidence that points to personal electronics being a real issue on board planes. Dave Carson of Boeing, the co-chair of a federal advisory committee that investigated the problem of electronic interference from portable devices, says that PEDs radiate signals that can hit and disrupt highly sensitive electronic sensors hidden in the plane's passenger area, including those for an instrument landing system used in bad weather."
Re:...really? (Score:4, Informative)
Have you seen how heavily shielded the cables and connections for PDAs and other PEDs are in US military aircraft?
http://en.wikipedia.org/wiki/File:E-8_crewmembers.JPG [wikipedia.org]
Thats what you need to keep avionics from being disrupted and vice versa according to the DoD, they've done a lot of testing on that stuff over the last 30 years.
C'mon... (Score:5, Informative)
ILS receiver antennas aren't "hidden inside the passenger compartment".
They're "attached to the outside of the friggin airframe".
Any story that gets the details that wrong, that fast, receives no credence at all. And if airplanes are having this much trouble with my 2mw iPad, what the *hell* are they doing about getting hit by 2GW of lightning?
(And don't tell me "Faraday cage"; that protects the occupants, but not necessarily the things connected to antennas outside the cage.)
Re:C'mon... (Score:5, Informative)
I'm not impressed by the story itself, but do note that ILS testers are operated from INSIDE the aircraft. I've done plenty of ILS ops checks as a Comm/Nav weenie in the USAF.
The airframe doesn't block the signal enough to matter.
Since my being entertained in-flight is of no importance, I leave my electronic gear off when flying and sleep/nap through the trip.
Re:...really? (Score:5, Informative)
Because .. testing every possible consumer electronics device which might end up on an aircraft, against all the possible aircraft, and all of the possible variations of an aircraft is damned near impossible.
Some aircraft have been in production for a long time (I think over 40 years for the 747). It's got a whole boatload of variations, and has been tweaked, updated, and re-arranged by different carriers over the years. It's got different generations of avionics, in-flight systems, entertainment systems ... and who knows what else. I've seen the inside of a 747 when it was stripped down to an empty shell ... it's got literally miles of wiring.
Now, think about all of the different models of aircraft in the world. You would need to test 'em all.
I get the impression to be able to definitively say that no aircraft could ever be affected by this, you'd need to do testing of every possible emission from the device to coincide with every possible state of the aircraft ... and some of those interferences might be intermittent or not 100% repeatable, or might be compounded by other factors they can't anticipate.
I don't think anybody has the resources to rule it out ... so they've erred on the side of safety. The sheer cost of trying to test this extensively would be enormous.
And, really, unlike the pharma industry which waits until you can prove that something is causing harm before they pull it, the airline industry is waiting for proof that it doesn't cause harm before they allow it.
Re:...really? (Score:4, Informative)
Actually, that's more about meeting TEMPEST requirements so as to not emit a signal from which an enemy can derive useful information. Hardening of the avionics is a different thing, and not something one will readily find an image of.
William
Re:...really? (Score:4, Informative)
This is why you occasionally get stories like the FAA knocking on a guy's door because his TV is emitting noise on a distress beacon frequency.
Not the FAA. The Civil Air Patrol and the local police/sheriff.
I was there for one of these. A Toshiba TV/DVD player combo. For some reason unknown it was emitting a VERY STRONG unmodulated carrier on 121.5MHz. So strong that the SARSAT system was picking it up and it was blanketing any other potential ELT in the area.
It was an early Sunday morning. Half a dozen cops, half a dozen uniformed CAP cadets, and a couple of SAR volunteers. A hapless college student was watching Sesame Street in his underwear.
We couldn't pin it down until one of us noticed that the signal had stopped when he answered the door. We asked "did you just turn something off?" and the rest is history. His TV was two days out of warranty, but Toshiba swapped it out anyway so they could test the thing to find out why it was emitting. There was no visible sign of any problem with the TV, nothing looked wrong, everything was working. It wasn't until we showed up at his door that he found out there was a problem.
Anyone who says that personal electronic devices cannot interfere with aircraft systems is ignorant at best. Properly designed, properly maintained, properly functioning PED in a properly designed, properly maintained, properly functioning aircraft has minimal chance, but too many things break too often and the costs are very high, so why risk it? So you can text your BFF that "hey, lolz, I'm on an airplane?"
Re:An engineer's reaction CORRECTED (Score:4, Informative)
Somewhere there is an engineer that argued quite vehemently that there is no way the air speed sensors on an Airbus A330 could possibly all fail
There is/was no engineer that argued this. Instead the argument was, "if this happens, what can we do to improve safety in that event?" That failure mode was thought of, I have absolutely no doubt. Engineers thought it was covered, they may have been wrong about that but I'll discuss that later.
leading the engines to stall in mid-flight
An aircraft stalling does not involve the engines, it involves airflow over the wings. Do you have any knowledge of the topic at all? Nothing I've read indicates there was an engine failure on that flight.
The aircraft crashed because when readings became invalid, the computer automatically disconnected the autopilot / autothrottle (as it should have). The pilots then made control inputs that were inappropriate for the situation. They were probably confused by the relative lack of data they had, and the multitude of warnings a complete air data failure causes. The pilots then held a nose up attitude through multiple stall warnings, eventually entering a period of extremely high sink rate. The aircraft had pitched up in excess of 35 degrees through this period, and the pilots held full nose up control inputs through almost all of it. It was the exact opposite of what they should have been doing. The pilots held the stall all the way into the ocean, impacting the water while still in a nose up attitude of more than 16 degrees.
I know people like to get up in arms whenever a crash is blamed on pilot error, but it's pretty clear in this case that the pilot's actions were inappropriate and their inability to recover from the stall despite ample opportunity will almost certainly be listed as the main cause of the accident. There were many contributing factors, but the data suggests that the aircraft would have flown just fine if given proper stall recovery inputs.
What could the engineers have done better? Indicate in a more useful way what was going on and which instruments were reliable. The pilots should have been able to tell at a glance what they should pay attention to and what they should ignore. The avionics display design may not have been good enough for them to do that. The stall warning may have deactivated inappropriately based on the invalid speed, because the computer thought the aircraft was traveling too slow for the angle of attack indicators to function correctly. This failure mode should not exist in my opinion. Either the angle of attack indicator should function at lower speeds, or an alternate stall indication should be used instead. Or just keep the warning on, since the aircraft is quite obviously not in landing configuration. From what I read, they were probably assaulted with a whole host of failure warnings that were confusing and may have contributed to a panic reaction.
Also, pilot training needs to be improved in some areas, especially involving loss of pitot static data. There is no reason an airplane of any type should crash because of a clogged pitot tube. This should be drilled into pilots starting with the most basic beginning flight training. I know from experience the topic is not covered at that level, besides a couple questions that may appear on the knowledge test. In fact, if I had not actually had a pitot tube get clogged during my training, I would have never encountered the situation at all.
There's some fairly good discussion about the events of the flight here [flightglobal.com].
Re:...really? (Score:2, Informative)
No, it's pretty clear what happened. For your convenience:
- The pitot tubes froze over
- Airbus computer response to a loss of airspeed data is to disable stall warning from AoA vane (which is unreliable at low speeds)
- Plane got into stall, pilots probably felt it warning or no
- Airbus procedure response to a stall is to set full power and nose up, the computer is supposed to figure out what angle is best to fly at to recover from the stall
- This obviously doesn't work so well without airspeed or AoA data. The computer went into alternate law, taking pilot control as gospel
- Pilots probably didn't spot the notification amongst the slew of other alerts they had to go through
- Given full nose up, the plane obviously stalled even harder, full power wasn't nearly enough to recover. It rapidly loses forward airspeed and begins dropping like a stone, still pitched up
- While the descent is accelerating the pilots know there's a stall, but once it hits terminal velocity (this is not something that happens very often and would not be at the front of their minds) they no longer feel a drop and assume that they've recovered from the stall and are climbing
- Obviously once you're climbing you're pretty much in the clear. They settle down to go through all their checklists, all the while the plane is dropping at 11,000 fpm towards the ocean. They may have got a terrain warning from the radar altimeter a moment before the crash. But then again, a cellphone may have been interfering with it! So perhaps if everybody had turned their phones off the pilots would've had 2,500 feet to recover from a 11,000 fpm deep stalled descent, rather than hitting the ocean unaware of it.
AF447 was a tragic combination of bad luck, awful circumstances, procedural problems, pilot error, design flaws and very bad luck. It had absolutely nothing to do with personal electronics.