"... and please switch off all electronic devices."

[kovidgoyal]

Originally Posted by cmdahler

Why would only having power to one wheel cause a car to swerve out of control, much less topple? Lots of cars have been designed for decades with powertrains that only applied power to one wheel out of all four, and I don't think any of those toppled as a result.

This is a silly argument. An engine stall hardly qualifies as a major emergency in a car; it's more of a major hassle.

Have you ever actually driven on a busy freeway? I for one would not look forward to the prospect of changing multiple lanes in a car whose velocity is not in my control.

As for why a wheel losing power will cause a car to swerve, its because the car is then pushed unequally one its two sides, creating a torque, a turning force. Think of rowing a boat and how rowboats turn by stopping the oar on one side.

And claiming that safety oriented agencies should outlaw something simply because it *might* cause problems is wrong. By that argument flying itself should be outlawed, since it poses a risk. Certainly, when a suspicion that something is dangerous arises, they should outlaw that thing temporarily. But then they should conduct investigations to determine whether there is an actual risk and how great the risk is.

I refuse to buy the argument that it is impossible to determine this risk or that it is impossible to reduce it to tolerable levels.

[DawnFalcon]

Originally Posted by HarryT

Your mobile phone, on its own, would certainly not cause any problem. 400 of them, all transmitting at maximum power, might, however, very well do so. Hence the regulation.

When they're not actively making a call? Yea...many modern watches /do/ radiate to the same degree.

Also, by running a mobile phone cell on the aircraft, you can actually block calls from being received or made during takeoff and landing. Technically I mean, not currently legally, but I believe aircraft companies have asked for that power.

[HarryT]

Originally Posted by DawnFalcon

When they're not actively making a call?

I was thinking of the scenario where a plane was out of range of the nearest cellular base station. When that happens, the handset will progressively boost its power in an attempt to "check in" with a base station (that's why, if you go off into the wilds, the mobile will run down its battery in no time flat). A plane-load of mobile phones, all doing that, may cause a significant amount of electrical interference.

[DawnFalcon]

Yep, another reason to allow cell phone operators to install a cell on aircraft which reassures phones as is well while allowing them to block calls during the sensitive time period.

[BongoBong]

Originally Posted by kovidgoyal

Have you ever actually driven on a busy freeway? I for one would not look forward to the prospect of changing multiple lanes in a car whose velocity is not in my control.

You could probably liken it to running out of gas on the freeway. Which does happen and I don't think is that terrible a thing to happen.

As for why a wheel losing power will cause a car to swerve, its because the car is then pushed unequally one its two sides, creating a torque, a turning force. Think of rowing a boat and how rowboats turn by stopping the oar on one side.

I dont think a rowing boat stopping an oar on one side is that great of a comparison. First off the wheel isnt stopping or providing resistance on one side, it should still be rolling with minimal resistance. But also with a row boat turning is only determined by the forces exerted on whichever side. With a car, steering is done directly with the wheel, not by adjusting forces exerted per side. I would imagine that losing power to one wheel would likely push you to one side, but so long as you have your hands on the wheel i would think it would be easily compensated for (thats just a guess though)

And claiming that safety oriented agencies should outlaw something simply because it *might* cause problems is wrong. By that argument flying itself should be outlawed, since it poses a risk. Certainly, when a suspicion that something is dangerous arises, they should outlaw that thing temporarily. But then they should conduct investigations to determine whether there is an actual risk and how great the risk is.

The banning of something goes beyond is it safe or not though, the pro's and cons have to be weighed and see if the pro's outweigh the cons. Sure flying has minimal risk but the con of banning flying outweighs the minimal risks. Electronics may cause potential problems, but if banning them potentially saves one crash it likely outweighs the minimal con of people having to turn off devices for 10-15 minutes during takeoff and landing (or so I presume goes there thinking)

I refuse to buy the argument that it is impossible to determine this risk or that it is impossible to reduce it to tolerable levels.

I guess the question becomes what is a "tolerable" level when its potential human lives at stake compared to the inconvenience of turning off your electronics for a short period during takeoff/landing. Personally I would hope that tolerable level would be very very close to 0 when the only benifit is people get to use their electronics for a little while longer.

[cmdahler]

Originally Posted by kovidgoyal

Have you ever actually driven on a busy freeway? I for one would not look forward to the prospect of changing multiple lanes in a car whose velocity is not in my control.

Don't be absurd. Of course I wouldn't look forward to it; but it wouldn't be a catastrophe, either.

As for why a wheel losing power will cause a car to swerve, its because the car is then pushed unequally one its two sides, creating a torque, a turning force. Think of rowing a boat and how rowboats turn by stopping the oar on one side.

It may apply a differential torque which will naturally cause a turning moment, but to say it will make the car swerve violently out of control is hardly likely. In an airplane or a boat, that's what a rudder is for. The rudder on an airplane, for example, easily overcomes the yaw from one failed engine and the other at maximum thrust. In a car, the tendency to steer would be even easier to overcome because of the friction of the steerable wheels on the road. Unless you were rapidly accelerating at the time, you probably wouldn't notice much pull just going down the road with the pedal lightly pressed to maintain speed. At the worst, it would probably be less of a problem than a blown tire. Regardless, not even a half-wit engineer would design a car with completely independent power sources to the wheels if the failure of one motor would immediately cause the car to be uncontrollable.

And claiming that safety oriented agencies should outlaw something simply because it *might* cause problems is wrong.

Depends on where your definition of "might" is, doesn't it?

[Jellby]

As for the phones, I wouldn't like to be in a plane full of people shouting at their phones, it's already bad enough in buses and trains, thank you

[jbjb]

Originally Posted by DawnFalcon

Right. And you know what the identified issue is? That the shielding systems on aircraft, which are important (indeed, critical) for protecting their electronics against thunderstorms, are not maintained or replaced nearly enough in current aviation maintenance schedules.

I've never claimed that things couldn't be arranged such that they are safe for cellphones etc., but they currently are not. Hence it makes sense to follow the rules.

Incidentally, the type of protection mechanisms required for resilience to lightning strikes etc. are not all the same as those required for EM immunity.

It's an important safety issue, and just incidentally it would also eliminate the issues with devices. A mobile phone in active use is VERY active in the EM spectrum, banning /calls/ might still be necessary during takeoff but just electrical devices from being on? Um...

(And you know that most pilot headsets have mobile phone adaptors, right? Really claiming pilots never make calls in the air? Ha!)

There's a big difference (in terms of radiated power) between a pilot or two making a call and 400 passengers making calls. Again, it's all a judgement about "acceptable risks".

/JB

[jbjb]

Originally Posted by DawnFalcon

Yep, another reason to allow cell phone operators to install a cell on aircraft which reassures phones as is well while allowing them to block calls during the sensitive time period.

Another big reason for installing picocells on planes is that calls have a better chance of actually working. A plane transitions between cells sufficiently frequently and quickly that the cellphone networks often struggle to cope.

/JB

[Kevin2960]

But surely this all misses the point, Safety isn't the issue,

The issue is that the airline has asked you to switch off,

The aircraft is thier property,

Therefore for whatever reason they have the right,

And surely we, on thier property should comply,

Without Question !

Or leave thier property !

[DawnFalcon]

Originally Posted by jbjb

Incidentally, the type of protection mechanisms required for resilience to lightning strikes etc. are not all the same as those required for EM immunity.

Mm hum (sigh).

There's a big difference (in terms of radiated power) between a pilot or two making a call and 400 passengers making calls.

Yep, inverse-square, the pilot's subjecting the equipment to a lot more!


Kevin2960 - That's only legally true to a VERY limited degree.

[jbjb]

Originally Posted by DawnFalcon

Mm hum (sigh).

What do you mean by that? Do you think they *are* the same?

Yep, inverse-square, the pilot's subjecting the equipment to a lot more!

That's an over-simplification in many ways:
- Power is inverse-square, field strength is inverse-linear.
- Inverse square applies to fee space - a plane is a metal tube with all sorts of different impedances. Assuming that radio waves will propagate as per free space is not justified.
- You're assuming all the EM sensitive areas are near the pilot!

/JB

[DawnFalcon]

Originally Posted by jbjb

What do you mean by that? Do you think they *are* the same?

Me? What do I have to do with it? I'm not the experts writing the safety reports.

[kovidgoyal]

Originally Posted by cmdahler

Don't be absurd. Of course I wouldn't look forward to it; but it wouldn't be a catastrophe, either.

So you're confident you can change lanes safely on a crowded freeway without being able to match speeds with the lane you're changing into? Wow you either think you're the worlds best driver or you're a ghost.

It may apply a differential torque which will naturally cause a turning moment, but to say it will make the car swerve violently out of control is hardly likely.

Really and you know this how?

Regardless, not even a half-wit engineer would design a car with completely independent power sources to the wheels if the failure of one motor would immediately cause the car to be uncontrollable.

As opposed to the half wit engineers who design planes that fall out of the sky because you turn a cell phone on?

Depends on where your definition of "might" is, doesn't it?

Huh? I was pointing out that regulatory agencies need to quantify the risk. In simpler words, to define "might". What has my definition, or your definition of might got to do with anything.

[jbjb]

Originally Posted by DawnFalcon

Me? What do I have to do with it? I'm not the experts writing the safety reports.

Sorry - I still don't understand what you're getting at.

I said "Incidentally, the type of protection mechanisms required for resilience to lightning strikes etc. are not all the same as those required for EM immunity", to which you replied "Mm hum (sigh)." What was that meant to mean?

/JB