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Can using a cellphone affect instruments on airplanes on MYTHBUSTERS

Midnight Flyer

Stay Thirsty My Friends
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Mar 6, 2005
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1,104
I know this topic has been discussed on here before, but I was flipping through the channels and saw that the MythBuster guys are trying to bust it.

Looks like the vor needle was jumping all over the place when they blasted it with cellphone rf waves...
 

viper548

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Dec 30, 2004
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I know they sure mess with my headset and makes it hard to hear a radio call
 

Spoolingbyu

On the can with WSIBS
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Dec 23, 2005
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I know they sure mess with my headset and makes it hard to hear a radio call

This is normally due to 2nd generation phones that employ TDMA, such as GSM and iDEN. In plain english, phones such as AT&T/Cingular, T-Mobile, or Nextel, can create a 217 Hz "buzz" in speakers, headphones, and other audio equipment. For instance, power on your home theatre sound system, or powered PC speakers, and place a call. Then, hold the phone near the speaker and you should hear "tick-tick-tick bzzzzzzzzz tick-tick-tick" or something like a ticking or buzzing.

Because the 217 Hz pulse repetition rate and its harmonics of the TDMA scheme are in the audio frequency range of human hearing, this may be "interference," to us, but I don't think it is harmful to navigation radios.

I haven't seen the Mythbusters episode so I would interested to hear their results.
 

Princedietrich

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Enough
Just be careful not to confuse it with the MDF and the 4-course.
 

Basil

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I've often heard that sound in my headsets when I've forgotten to turn my phone off.

I always believed that the big concern was the voltage that a transmitting phone could impart into the wiring between the flux gate and AHRS, etc. I saw this explanation on PBS. Some airline captain was telling the host that he has seen headings greater than 30 degrees off while a passenger's phone was on.

There are also a few ASRS reports (all from the CRJs) about sudden TCAS RAs at with red intruder blocks displayed over the aircraft symbol at the same altitude, even as the pilots climbed. Evidently, the FAs all reported pax with cellphones on during the events.

I've personally never experienced anything worse than a loud hum on a specific comm freq that went away after a passenger turned off his video game.
 

cjdriver

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May 3, 2005
Posts
736
Had a pax bag in the nose of my twin with a cell phone in it which caused my autopilot to command pitch changes inadvertently. In fact, transmitting on VHF in the 130 and up freqs also does it. Must be something in the STEC autopilot that is sensitive to this RFI.
 

svcta

"Kids these days"-AAflyer
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Nov 14, 2004
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SOLO!
I can't find it, but a few years ago I saw an Avweb article that indiecated that a long study by some university revealed that not only were they surprised at how much interference they witnessed from cell phones, but that they were recommending that even laptop computers be restricted, too. Actually, I just found it. It's pasted below:


March 2, 2006
"Researchers at Carnegie Mellon University say the FAA and FCC should maintain their bans on cellphone use on airliners and consider broadening the ban to computers and other non-broadcasting electronic devices. Airlines should also be compelled to install monitoring equipment so pilots can detect signals that might disrupt their instruments. The researchers found that the interference with aircraft systems caused by all electronic devices was greater than previously thought, according to the Pittsburgh Post-Gazette. The team concluded that the in-flight use of electronic devices "will, in all likelihood, someday cause an accident by interfering with critical cockpit instruments such as GPS receivers." And, surprise, surprise, they discovered that not everyone obeys the current rules against cellphone use. The researchers gathered their data by putting monitoring equipment on aircraft during flight. The equipment picked up signals (including up to four cellphone calls per flight) from all the sources and the researchers said they were surprised at just how much the signals interfered with the aircraft's electronics. Previous FAA studies indicated that non-broadcast devices didn't pose any threat but the CMU study suggests otherwise. "We found that the risk posed by these portable devices is higher than previously believed," researcher Bill Strauss said in a release that announced the findings. "
 
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