Why do pilots ask you to turn off all electronics on planes?

Question

During takeoff, they always ask you that question. I know electronics must interfere with the plane, but how?

Answer 1

I am a pilot. There may be no proof written in a scientific journal somewhere that says that cellphones interfere with radio navigation, & communication on aircraft, but I can tell you from my own personal experience that they do.

Cellphones typically use three channels simultaneaously during the time that a call is in progress. Two for what we call "Full Duplex" communication (that is where each person at each end of the line can talk at the same time, & hear each other as well without having to "key a mic" like you would on a walkie talkie. That would be "Half Duplex") The other channel is what is known as "The Control channel" . The control channel helps the cellular network track where your cellphone is on the network, so it knows where to direct an in-comming call. As long as the phone is on, it communicates on the control channel almost constantly with the network.
Now each time a cellphone travels from one zone that is covered by a single cell communications tower to another, a series of beeps & blips are exchanged between the phone & the network. I have personally heard these beeps & blips comming from an active cellphone over my radio in the cockpit of my aircraft. I have also heard the same tones over my car radio when I am travelling between cell sites in my car with the cellphone turned on. You may have heard these sounds yourself, & not been able to figure out where they are comming from.

Even if the radio is not tuned to the same frequency as the cellphone network, these signals will burst through as interference called "cross channel" because the tiny transmitter in the cellphone is so close to the radio receivers in the cockpit, or the wiring to the radio antennae.

Now try to imagine what would happen if only 10% of the passengers on a commercial airliner had their cellphones on at the same time, not talking, just on. If the passengers numbered 100 - 200 then that would mean about 10 - 20 cellphones would all start injecting interference into the communications systems in the cockpit everytime the aircraft traveled over a new cell site. With all of that beeping, & blipping going on at the same time it would be very likely that it would jam out the vital communications between the pilots in the cockpit, & the air traffic controllers, & put the safety of the fight in severe jeopardy.

Knowing that, I have little doubt that other systems in the aircraft can be affected by RFI (radio frequency interference) as well.

So PLEASE for your own sake. Keep all of your personal electronics turned off while riding in an aircraft.

BTW. I watched that Mythbusters episode with interest, & they were using a VOR navigation system in a car riding around a parking lot at a community airport, as well as in an actual aircraft parked stationary on the ground. They didn't even come close to a real life test because they would have violated FAA regulations in the process, so anyone who drew the conclusion that active cellphones on aircraft are NOT dangerous from that are sadly mistaken.

Answer 2

pilots ask you to turn off all electronics on planes as they are found to interfere with electronic gadgets they use. Their communication antenna are found to just outside the plane ie; near the wings.Thus any gadget used inside a plane might interfere.Technical details of how these gadgets interfere is explained below :

There are two GSM telephony bands reasonably close to GPS. Transmissions on them can cause front-end overload on GPS recievers. Your phone will transmit on one or the other depending where you are. They listen first, and don't transmit without hearing a beacon from the cellular base station.


Also, there is the local oscillator and IF issue mentioned elsewhere. Generally a superhetrodyne receiver will transmit at low power whenever it's on, at a whole list of frequencies. These include the frequencies of all intermediate-frequency oscillators, the mixing products of each IF with each other, and the mixing products of the first IF with the frequency you are listening to. Since cell phones scan for beacons, this can be even more frequencies. Mixing products would be F1 + F2, F1 - F2, and then you have harmonics, mixing products of harmonics, etc.

Another common source of interference with aircraft navigation are the local oscillators of broadcast band receivers. Back in the bad old days when NDB ruled the navigation world, these could be insidious little buggers. These days, the LF NDB band is about to evaporate in a puff of smoke.

But the worst of the bunch is the FM broadcast band LO. It's not often that one will radiate, but when it does, it is right on top of the navigation band signals you're trying to use. This makes VOR or ILS signals very suceptable. The VOR signal problems aren't that big a deal, provided it isn't being used for an instrument approach. The ILS signals are another issue entirely. Those are precision signals used by airliner and private pilot alike. Airliners are aiming at a window in the sky of only 10 feet high and 20 feet wide. This window is only 200 feet above the ground and they're screaming toward it at typical speeds of 150 MPH. The plane has to be at the 10,000 foot mark before you can turn on electronic things.

Would you like to listen to your FM radio while the airliner is doing an autopilot coupled approach in 0-0 conditions? I didn't think so... :)

Answer 3

Some electronics generate electromagnetic waves that can interfere with the electronics of some equipment in the cockpit. If you were taking off or landing in bad weather the pilots use all instruments, and suppose some of your instruments were reading incorrect or glitched? Could be very dangerous. There are little antennas on the outside of the plane that pick up aviation signals that can be interferred with by waves generated by your electronics.

Answer 4

Because some wireless electronics like laptops interfere with the radio which the pilot and co-pilot use to communicate to the airport and to other planes.

Answer 5

Because there is now way to prove that cell phones interfere with the electronics on aircraft - so rather than spending a fortune to prove that they do or dont - it is cheaper to tell the flying public to turn it off. Also, airlines want you to use there inflight $.95 in flight phones if you need to talk to someone ,..

Answer 6

planes no longer have levers,rods and wires connecting the control equipment to the cockpit, its all done now by electronic transmission. even though there are safeguards place to prevent interferance from affecting them it is dangerous to have other types of personal electronics switched on just in case

Answer 7

They are supposed to interfere with the instruments and radio contact with the ground, but Mythbusters tested this myth and it was busted. So I think they do it just to make you pay $10 per minute to use the Airphone

Answer 8

Cuz people with cellphones are irritating, mindless jabberjaws and the flight attendants just love walking around making sure you cell phone bullies are unplugged for a short time in your adult lives.

Answer 9

the instruments on the plane, are radio signal operated.
so are cell fones, computers and other items

Answer 10

interference