Why should we turn off mobile phones when we travel in an airplane, Part 2

With discussion in previous post, we now know the mobile phone’s GSM TDMA signal pattern would generate buzzing sound on audio speakers. Now, how this is buzzing sound related to the safety of air planes?

After watching many videos of “Mayday, Air Crash Investigation” TV programs, I start to understand that today’s plane communications are still running analog technologies. Pilots would hear the buzzing sound generated by your mobile phone.

Fresh tomatos.
Photo taken in Hsinchu County, Taiwan.

Suppose pilots are busy communicating with Air Traffic Controller (ATC) people and this buzzing sound takes place, they might not hear important details such as which runway to land or which terminal to park the plane. And this would endanger the whole flight.

For digital radio systems, most of them are designed with auto-correction mechanism. The buzzing sounds are just low frequency interference to these radio technologies. The digital radio system can endure such neglectable interference.

Now we can answer all the challenges raised in this video.

"90-Million -dollar aircraft can't ignore the signals from my 40-dollar iPod Shuffle?"

In fact the electronics of an air plane can ignore all such interferences. Only the conversation among pilots and Air Traffic Controllers would be seriously disrupted.


"Can I hold this plane hostage with my (Nintendo) 3DS?"

No.


"How come the plane is not interfering with my phone?"
"Why don't other phones interfere my phone?"

Your mobile phones are using GSM (2nd Generation) or even better (3G, 4G LTE) technologies. They are all digital system so they can endure interferences from each other transmitting devices such as mobile phone.


"I just always leave my phone on and nothing happened?"

Only the pilots would hear the buzzing sound. Pilots do need more time to check whether they understand what ATR’s commands or not. This would increase the danger but luckily most of the time no dangerous results happen. However, we should never risk our lives by leaving mobile phone running on the plane.


What about WiFi?

WiFi is not TDMA at all. WiFi will never create buzzing sound on any audio speakers. That’s why many air liners even provide WiFi services on their air planes.

Because we do not have easy way to make sure all mobile phone would never fall back to GSM mode, the only way we can do is we just have to stop radio transmission of all our mobile phones.

As long as our mobile phones are running in Air Plane Mode, it is absolutely OK to leave powered on because no transmission at all in Air Plane Mode.


One more thing…

I know some people are so eager to call their families and friends so they start to dial their mobile phones right after the plane has touched down and taxiing on the runway.

I think this is a very bad idea because the pilots are still busy communicating with ATRs. Also because of the long distance from runway to the nearest mobile base stations, it would possibly fall back to GSM mode. GSM mode can work in longer distances. So this action would make pilots very uncomfortable.

Because so many people could start their mobile phones at once together inside the plane when the plane is safely parked, the phones can hardly register successfully because the surge of registration requests rushing into the base stations. My personal habit and suggestion to all is: never start your mobile phone inside the air plane. Start the mobile phones only when we are walking inside the terminal buildings. This saves us a lot of time waiting for the mobile phone to register and also saves the battery power of our phones.