Why no electronics during Take off

[randombeaner]

Now im curious, why cant you use electronics during take-off or any type of radio/reciever during flight.
They say it disturbs the instuments but which ones?

I know ADF uses AM but why no radios. Most people don't really listen to AM (ok Im generalizing but it works).

and whats the difference between "Airplane safe" and all other laptops (Probably just the price)

thanks in advance

[Craig.]

these days its about safety more than anything else. It would cost a bomb to certify every cell phone safe for use in flight so its easier and cheaper to ban them all same goes for most other receiving equiptment, it would also end up effecting the radios in flight, sort of like that annoying sound you get when two signals cross paths in your car. During take off, if you have something in your hands like a video camera or a gameboy and you crash, it could become a rather nasty missile

[SilverFox441]

All electrical equipment generates an electrical field when in operation. Obviously any device designed to transmit a signal provides a bigger field. Recievers also contain a radio frequency (RF) oscillator and this can be detected as a transmitted signal. The presence of this field can disturb a large cross section of the rather delicate sensors that operate on a plane...at least in theory.

They ask that all such devices are off during critical phases of flight so that no "minor" effects result in a major mishap.

"Airplane safe" devices are built to a more stringent RF standard...actually similar to the standard used in older secure computer systems. Secure systems were designed to prevent spies from reading a computer at a distance....same problem, different application.

[randombeaner]

makes sense
thanks for the responce

[Scottler]

The REAL reason (as most of you know, I would know) is because take off and landing are the most dangerous times of flight, and they want your full and undivided attention in case you need to get out of there in a hurry.

[PSW]

The law of physics  ;D. Any electronic device or material sends an electric impulse and as you know, there are electronic devices and materials onboard the aircraft, especially where the Cap & the First Officer is sitting. YOUR electronic impulses or interruptions could cause other fields to be altered and you know what that means, KA-BOOM !!!  :o


James

[Chris_F]

The REAL reason (as most of you know, I would know) is because take off and landing are the most dangerous times of flight, and they want your full and undivided attention in case you need to get out of there in a hurry.

I'm more inclined to believe this explaination.  If RF interference were the main reason for the rules I would expect that the requirement would be for such devices to remain off for the duration of the flight, not just takeoff and landing.

[SilverFox441]

If distraction was the problem wouldn't they be worried about books, magazines...etc?

The most RF rich environment that a plane operates in would be the 5 miles surrounding an airfield. Interactions of a hazardous nature are going to take place there...not when a plane is 40,000 feet in the air and there is nothing within a 5 mile bubble (excepting the odd plane on a reverse course at a different flight level).

I experimented with this in the CAF...you can do some weird things if you put unshielded devices in the wrong places.

[Scottler]

Speculation will continue to go back and forth for weeks, however I assure you that this was a question that was asked during one of my MANY extensive airline training courses.  

As for the "Why no books?" question...simple.  Books don't require a headset.  You can still HEAR what's going on around you, and chances are if you're reading, you're at least awake.

They can't very well say "Well you can use this one, but only if you'll skip the headphones, but you can't use this, and this is okay..."  It's a lot easier to just say, "Look.  No electronic devices."

[SilverFox441]

Scott, it's possible that the airlines simplify their explanations of the hazards.

As an aircraft instrument and electrical technician I can tell you of at least one aircraft type (a business class plane, the Falcon 20F) where I can change the fuel state or nav heading (gyro compass) from the cabin with just some cheap electronics. The fuel state can only be affected with the aircraft on the ground, the nav state can be affected anytime gear and flaps are down. It won't work with good quality electronics...only cheap stuff that bleeds RF like a stuck pig. Not really a big danger in most cases...but who needs distractions during critical flight phases?

Keeping the pax (who are mostly just cattle and have no idea what is going on in a plane) aware of their surroundings is vitaly important...and easier to explain than radiant RF fields and induced EMF.  

In truth, it shouldn't be possible to affect a commercial airliner...they are tested against this after all. The trouble is that no one can test against every combination of devices and their configuration.

[Scottler]

I, like you, have spent extensive time and received thorough training on aircraft, though mine were commercial airliners ranging in size from the EMB-120 through the B777.

Yeah, it's easier than explaining RF fields (a topic which I, too, get...primarily because of my years as a DJ).  

However, when teaching a class of airline employees, the likelihood of something being dummed down, specifically safety protocol, are very low.

Could it potentially be a problem?  Sure.  As we've seen over the last three years anything is possible.  But as has been mentioned, if there were an RF interference problem, said problem would occur throughout the flight, and not just on take off/landing.

[SilverFox441]

In flight the A/C is protected by the static-grounds (also sometimes called lightning disipators depending on manufacturer). These are the little fibreglass fork-like objects you see on the trailing edges of wings/ stabs. They have a metal core and two, or more, exposed needle-like projections. These work alongside the surface bonding to make sure that there is a common electrical potential across the entire skin surface (basically a ground-plane which is useful to many radio/nav systems). They can only do their job at a minimum airspeed.

This is the simplest, yet most vital, "electrical" system on a plane. You should see what happens if there is a major failure in this protection....wild.

[randombeaner]

In flight the A/C is protected by the static-grounds (also sometimes called lightning disipators depending on manufacturer).

now that got me wondering is it possible to get stuck by lighning in a small plane without one of these or would the aircraft not conduct the electricity due to the fact its not touching anything?

[SilverFox441]

I've been in a Falcon 20 that got hit by lightning...and it had 10 fully functional disipators in place.

Pretty wild occurence. Lots of blown fuses, some blown lights, the flourescent lights lit up (including ones we thought were broken) and all the disipators required replacing after we landed. We took around 5 strikes in less than two minutes!  :o

We had been trying to use the weather radar to find a way through a storm fron that ended up closing up behind us. I spent the whole trip wedged into the jump seat monitoring the weather radar and the electrical system.

[randombeaner]

ouch thats gotta hurt! When anyone says that chanses of getting hit by lightnignig are probably less then winning the lottery you can say you got stuck five times..... then play the lottery!

ps because the airplane is metal, is it a very small chance that you yourself can get hit?