Quote:
Originally posted by lifesaver
So why cant we use cell phones and radios in flight? I know it has something to do with the frequency of radio waves. Why does a radio emit waves, but not a Discman? Will my plane fall out of the sky if Joe Traveler forgets his phone is on? How about if my walkman in my bag gets jostled and accidentally gets switched on? How many cell phones and radios are too many? I know it has something to do with the transponder (the thing that tells the tower where the plane is) and radio wave frequencies.
Can maybe an engineer on here (calling AlphaSigOU) help with an explanation - and incluse soem scientific soundin stuff? I am flying on Friday and I’ll be wondering the whole flight. Thanks.
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Part of the reason behind the ban on cell phones in flight is that earlier cell phones operated on frequencies close to UHF navigation and could cause interference with aircraft navigation equipment. The other reason is to try to make you use those obscenely-expensive seatback air phones. Your airplane may not fall outta the sky, but a seasoned pilot can tell if RF (radio frequency) interference is messing with his instruments.
Another thing is the method of communication of cellular phones. Basically, a cell phone is a radio that relies on its transmission coverage through cells within the line of sight of the cell antenna. Using a cell phone in flight is obviously a not very good idea; at the normal cruising altitude of passenger airliners you have a MUCH greater line of sight; your cell phone might try to access several cell towers within its line of sight (at 35,000 feet your line of sight could be hundreds of miles); that's where overload-prevention features on cell networks might kick in. It's a well known fact that some of the passengers on the doomed aircraft on 9/11 used their cell phones to relay their plight to authorities on the ground.
Most airlines have relaxed cell phone usage to include the taxi out to the runway and the taxi in to the terminal; you hafta turn it off before takeoff.
The transponder (a contraction of 'transmitter-responder', and usually abbreviated "XPDR") emits a discrete four-digit code that identifies an aircraft to air traffic control. Certain transponder codes are expressly reserved for the following situations:
0000 = reserved for military interceptor jets
1200 = aircraft operating on visual flight rules (VFR)
7500 = hijack
7600 = radio failure
7700 = EMERGENCY
If you're flying on United Airlines, most aircraft will carry the radio conversations between your aircraft and ATC. However, this is a feature turned on only at the discretion of the captain. (If you ask nicely, he might relent). It's on Channel 9 of the audio programs. None of the other airlines have this feature.
BTW, I'm flying down to Fort Lauderdale tomorrow!
Cell phones/radios in flight...
) - so the plane was parked out of the way somewhere. The captain announced that we'd be delayed about 2 hours. So everyone went for the "obscenely-expensive seatback air phones" to tell friends, family, and colleagues about the delay. About ten minutes later, AFTER everyone had paid $5/min or whatever it's up to now, the captain announced, "Oh, by the way, you can use your cell phones." 
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