jkhuggins

My understanding is the concept of lap babies is actually a wonderful example of the overall risk/reward analysis that folks here in TS/S wish that the FAA/TSA/etc. would engage in more frequently.

Short version: many parents with small infants, if forced to buy a seat for them, would choose to drive to their destinations instead of flying. The chance of an infant dying in an automobile crash is much higher than that of an infant dying in an airplane crash, even if held as a lap baby, simply because automobile crashes are far more frequent than airplane crashes. Allowing infants to travel as lap babies encourages, on the whole, the safer mode of transportation.

But this is getting away from the original thread ...

RichardKenner

Before the Space Shuttle Challenger accident, there were mutiple flights in which the o-rings in the seals were breached by hot gasses. This wasn't supposed to happen, but rather than dealing with it as a failure that had to be fixed, NASA took a view like yours: "since we've flown in this condition and the vehicle hasn't blow up, it must be OK after all". I think we all know where that led. The Fenyman Appendix to the Challenger report is strongly recommended reading for anybody who wants to understand safety issues. It contains the famous quote "nature cannot be fooled".

As was said, all electronic devices emit EMI, some more than others. With pilot iPads, they can certify with a particular model (that's my understanding in this case, actually) and require they be kept in proper repair. One owned by a passenger may well have damage that increases the EMI by an order of magnitude.

The reason why commercial aviation has been so safe is that the standard for anything in that field has been "you can't do this unless you can prove it's safe" and never "you must allow this unless you can prove it's dangerous". Electronic devices are no exception.

Travelsonic

Um... as an analogy, how is this really relevant?

bamin

"Out of an abundance of caution" why don't you drive instead of flying? or as your id indicates go amtrak..

OldGoat

Your analogy to Challenger is puzzling. I fail to see how an electronic device can cause an explosion. Moreover, the limited shuttle flights don't equate to the hundreds of daily flights that must take place with transmitting phones, laptops, tablets, etc.*

Moreover, you missed my last line. I wasn't saying "you must use this unless you can prove it isn't dangerous". I said "...the FAA should reconsider their rules".

I'm surprised you missed that. You seem to be a careful reader.

* taking a SWAG of 99.9% compliance means a few percentage of flights a day depart with an electronic device on the "on" position. If you have real data, please provide it.

RichardKenner

The issue isn't an explosion per se, but something bad and the analogy is accurate. We're talking about "safety margin". During Space Shuttle development, the goal was that no hot gas was supposed to go past the o-ring. But there was a belief that even if it did, that would not neccesarily be catastrophic. So when a number of flights had blowby and the vehicle was still safe, the view was "well that shows that the safety margin was enough". No, it didn't.

This has been discussed before. Because devices hetrodyne with each other, the amount of EMI potentially increases in a non-linear fashion with the number of devices if you look at the number of different frequencies. What your example shows is that the safety margin of EMI rejection in avionics is may well be sufficient with some small number of devices turned on (and mostly in standby). If there were no limitations on electronics, there would be dozens of times more devices turned on. The experience you site cannot be extrapolated to that very different circumstance.

WillCAD

If modern aviation electronics are not shielded form external EMI, then instead of saying, "Prove to me that those tablets and phones are safe to use on a plane," we really should be saying, "Prove to me that those planes are safe to use in a world that is saturated with electromagnetic radiation from both natural and artificial sources."

The Challenger disaster was caused by equipment that was allowed to fly despite known defects.

Having planes that might fall out of the sky if a passenger fires up a wi-fi or 4G device in the cabin is also defective equipment. If a plane isn't equipped to fly in sub-zero temps, it's not permitted to fly to Barrow or McMurdo. If a plane is not capable of flying safely in a world full of EM radiation, then it's a flawed design that should be upgraded with better shielding and hardnened electronics.

OldGoat

First, the analogy still fails because the linkage between adverse EMI and any adverse outcome is not direct. In the Space Shuttle, the linkage was direct.

Second, your last paragraph supports my position; the FAA should reconsider their rule. On any given flight the rate of compliance may fall to near zero; the likelihood is that it already has for some flights, yet no planes have fallen from the sky. Given the likelyhoods, the FAA needs to better understand why the adverse outcomes have not occurred. They should reconsider, and either ban devices entirely, or permit them.

The facade of compliance is simply that, a facade.

GoAmtrak

Gee, thank you for that insightful gem of wisdom. TSA would probably vigorously agree with that kind of outlook. "No one is forcing you to fly, so never question the status quo procedures."

Darkumbra

I'll bet dollars to doughnuts that a large majority of iPhone and iPad users do NOT know how to power off their device. I'll bet you that they think that just pressing the upper right hand button does the trick. To really turn it off? They need to press and hold that button.

Any takers?

Loren Pechtel

They're not going to cause an explosion. The primary risk a controlled flight into terrain accident.

RichardKenner

"Shielding" is not binary! You don't either "shield" or "not shield" a device, but rather you have a certain level of shielding for a device. Airplanes have numerous cables all around that also require shielding. The more shielding you have, the heavier the airplane is. It's completely impractical to shield every cable in an airplane and all of it's avionics against any possible level of EMI at every possible frequency.

It's no different from any other design decision in an airplane: you can't make the wings infinitely strong. At some level of force, they'll come off. The goal in designing the airplane is making them strong enough with an adequate safety margin, and no stronger (because more strength means more weight). It's the same with shielding. You install enough shielding to give you an adequate margin, and no more.

So now you have to ask what an "adequate" margin is in the presence of an arbitary number of types of electronic devices. And that's far from a trivial question.