Wednesday, August 29, 2012

FYI: Portable Electronic Devices On Commercial Airplanes

Nice big old debate on the topic going on at Tam's -- and let me reiterate, this is not about celphones! (Trouble there is on the ground, not on the plane: your phone lights up too many cells, moving too fast. The system can freak out.) So: WiFi, Bluetooth, incidental radiated yeech: do they or do they not have significant potential to interfere with avionics during takeoff and landing?

Jury's still out, which is why FAA is revisiting the issue. What I'm not hearing from anyone is the other problem with having your toys out during those operations most likely to include some violent maneuvers: they can become projectiles. Me, I am not wanting to see what happens when your ultra-slim laptop slides across the aisle, catches air and hits my head; YMMV. (And willya please put away that fat hardback book, too?)


Stranger said...

The problem is all that nice unshielded cabling right there behind that plastic panel by your elbow.

Bluetooth pegs the needle on my field strength meter at about six feet. If the "devices" at the end of the cabling will rectify that, yes, it could probably cause problems. Especially if the resultant bias causes the "device" to go into clipping or to not function at all.

There are far too many variables to say "this, that, or the other." Length of cable, distance to the device, type of device, capacity to other cables and to the airframe, and so on, ad infinitum.

And yes, I would not care to become a victim of someone's nine pound laptop when the aeroplane encounters a sudden downdraft.


Roberta X said...

Y'know, they fly those planes within, h'mm, carry the three...500' of megawatt UHF transmitting antennas. (And through thunderstorms, though not by choice.)

"Shielding" is overrated; 100% is impossible in a flexible cable and design frequently makes it worse than useless (Shielded telephone wiring at an AM transmitter site just makes the RF problem on the phone lines worse!)

From what I have seen in the company helicopter, there's a lot of UTP cabling used; if the devices at the far end are properly designed, they've got good enough CMRR that a little more RF isn't going to be a problem -- and if they aren't, you're already dead, the ticking bomb just hasn't gone off yet.

Jim said...

I want to be reasonable about this, but please: Rob me of my paperback and I might be forced into conversing with the guy in the next seat.

Ed Skinner said...

... not to mention that 300 pound fat dude not wearing hs seatbelt.

Alan said...

Per the large hardback book: If they thought that was a problem they'd tell you to put it away. I don't buy the sudden projectile argument. You're all in the same refrence frame and what acts on the frame acts on everything together. A force strong enough to make that book (or gadget) a deadly projectile would do bad things to your neck too.

Able said...

This is why I visit, the conglomeration of all this knowledge, experience and qualifications dissecting the finest nuances of every topic (sometimes with quoted reference material and diagrams - Yey!).

It's almost like a real life Big Bang Theory (just for the record, whilst I do sometimes reluctantly admit to having way to much in common with all the characters of aforementioned programme I'm wondering how I fit in here. I fear I'm the Penny character, the dumb but extremely good looking one [stop laughing, I am if you squint and it's dark], or am I, as the 'token foreigner' Raj? I am NOT Howard as my chat up lines are works of art and Roberta will marry me when she comes to her senses ;-p )

Drang said...

Don't forget the people who insist that their 20 pound infant is safer in their arms than strapped into a seat.