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Author Topic: Interfering With Flight?  (Read 6401 times)

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Offline M Philippe

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Interfering With Flight?
« on: January 18, 2011, 09:42:17 AM »
Interesting read.

http://www.nytimes.com/2011/01/18/business/18devices.html?_r=1

Exert from the article.  The rest of the article can be found at the above url

"The announcement over the plane’s speaker seems as much a part of the routine before takeoff as the demonstration of how to buckle a seat belt: Please turn off all electronic devices.

But some passengers invariably ignore the request, perhaps thinking that their iPods or e-books do not count. And really, does it matter if the devices are left on?

The answer, it turns out, is that sometimes it may.

“It’s a good news-bad news thing,” said David Carson, an engineer with Boeing. Electronic devices do not cause problems in every case, he said. “And that’s good,” he said. “It’s bad in that people assume it never will.”

Passengers are taking an increasing array of devices on board planes — cellphones, tablets, GPS units and more. Many of these devices transmit a signal, and all of them emit electromagnetic waves, which, in theory, could interfere with the plane’s electronics. At the same time, older planes might not have the best shielding against the latest generation of devices, some engineers said. "

Marc Philippe
PPL-SEL

Offline Nicolas

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Re: Interfering With Flight?
« Reply #1 on: January 18, 2011, 02:29:20 PM »
I hope its just the way this is written... cause this is hillarious!

"The pilot had called home, and the call remained connected for the last three minutes of the flight. In the final report, the New Zealand Transport Accident Investigation Commission stated, “The pilot’s own cellphone might have caused erroneous indications” on a navigational aid."

Cause this sounds like the pilot was yapping on his cellphone while landing a plane, crashed, and they blamed the cellphone's interference with his navaids??  Certainly it had nothing to do with the fact the pilot wasnt operating in a sterile cockpit environment during a cruicial phase of flight.

On topic though, I've often wondered as to the ... authenticity, for lack of a better word, of the statement that electronic devices interfere with cockpit operations.  I can understand radio signals from cellphones and GPS units... But an iPod, laptop (assume wireless off), or cellphone.. how?  And why is it those devices "can" interfere with the plane but something like a digital watch, or pacemaker "cant"?
Nicolas Roome
C-FBVQ 1970 American Aviation Yankee

Offline jfdoyon

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Re: Interfering With Flight?
« Reply #2 on: January 19, 2011, 09:32:48 AM »
Like they said, anything electromagnetic has the *potential* to cause problems.

The likelihood is quite low that anything not incorporating a receiver/transmitter will cause issues mind you.

On commercial airliners, I think it's just the understandable laziness of not trying to differentiate between what kind of device emits what kind of radiation.  So for safety, you just say everything has to be off, notably for T/O and landing.

In cruise flight, so long as the "radios" are off in your device, you're generally OK.  Most modern phones now have an "Airplane mode" for instance.

I can easily believe that there might be occasions where such interference can happen an cause issues.  Maybe as time goes on modern a/c will be better equipped to be more resistant to that kind of stuff, but fleets can get quite old, so that's a long life cycle to keep in mind here.

In the end, I think passengers that can't stay off their phones for a little while, and are willing to compromise the safety of everyone on board in the process, are jerks.

Offline jfdoyon

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pcarscallen

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Re: Interfering With Flight?
« Reply #4 on: January 20, 2011, 06:31:51 PM »
First post for me in the new year...

I believe when the FAA started testing interference issues they actually only were able to produce a situation where a "cell phone" caused problems once during the testing.  If memory serves me right it was in an anechoic chamber and not on any of the test flights.

I occasionally leave my cell phone on (and it has blue tooth, wifi and gps) while flying the B1900 and have never had any issues with interference. 

As jfdoyon says all electronic devices have the "potential"to interfere so this is more then likely the main reason air carriers and Transportation authorities play it safe.
Although now lots of airlines are allowing people to not only use Wi-fi but cell phones for phone calls and texting. Personally I can think of nothing worse then a flight from Auckland to Vancouver and having to listen to 300 people chatting away on there phones.

Offline jfdoyon

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Re: Interfering With Flight?
« Reply #5 on: January 21, 2011, 09:47:25 AM »
It looks like the phenomenon is understood as where specific bands start bleeding into other bands in ways that normally shouldn't happen.

the problem seems to be that it's not entirely well understood what circumstances can cause this to happen.  Thunderstorms are probably a good bet, but there may be others (like sun activity).

Mythbusters also did a test, went for a few flights, noted no problems, and called it busted.

I dunno, that seems like a rather crude and superficial test.

And indeed, who wants to be stuck in a tube with 200 people yapping away on phones?

Maybe if the on-board phones were made more affordable, people would actually use them, and reduce the risk that way (and the chatter).

Offline ckiff

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Re: Interfering With Flight?
« Reply #6 on: February 01, 2011, 01:16:57 PM »
I'm chiming in a bit late here, but I took a bit of a hiatus from the board for a couple of weeks. Now I'm back!

As for cell phones being on, in the DASH-7 if anyone in the front two rows of the cabin have their phones on, we can often hear the interference in our headsets similar to if you put a phone next to a speaker and someone calls. I've never noticed any problem with the instruments, but it is damn annoying.

When I used to survey, we ran cell phones and sat phones in the aircraft and it wouldn't show up on sensitive magnetometers.
Chris Kiff
ATPL / Class 1 Instructor / Ex-RFC Instructor / Current Airline Pilot

Offline Tony Hunt

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Re: Interfering With Flight?
« Reply #7 on: February 01, 2011, 01:49:48 PM »
I've noticed audio interference through the headset like Chris mentions - I hear it in the Husky and in the Club Cessnas if my iPhone is on or a student has a smartphone.  It gets picked up by the intercom or the headset wiring, the Garmin intercom seems pretty sensitive to it.  It isn't continuous, it's either the phone checking in or picking up a text message.  Cell phone techies can probably explain what I'm hearing, to me it sounds like the old Lone Ranger theme song played on a tiny broken speaker.

I've never noticed any cellphone interference on the Nav or Comm radios, nor on the GPS.  Watching the GPS reception signal strength, and/or the OBS, there seems to be no effect.  Of course, with the Zulu headset I can also make the occasional phone call too, using bluetooth and the cellphone, audio reception is crystal clear, I spoke to someone recently and he didn't even realise I was using a cellphone, let alone from 2,500 AGL.
Tony Hunt
Ex Cardinal CF-TDN
Ex Baron C-GXOY
Ex Husky C-GTHY (my favourite)
Ex Trinidad C-GTLX
Next Aeroplane? - I'm looking!
Instructor - PPL, CPL, Multi-IFR and Tailwheel

Offline pigpen

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Re: Interfering With Flight?
« Reply #8 on: February 01, 2011, 03:42:25 PM »
GSM phones by the nature of their RF time domain multiplexing can induce a 200 hz signal into unshielded (ie cheap) audio equipment.  I have a cheap pair of speakers connected to one of my PCs and they go bananas when my cellphone does anything.

The signal obeys the inverse square law - ie a little distance helps a lot - and if you get desperate, wrap the phone in a couple layers of aluminum foil as a kind of Faraday cage.  Not sure it's going to help the cellphone reception, tho.

Offline M Philippe

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Re: Interfering With Flight?
« Reply #9 on: February 02, 2011, 08:43:47 AM »
Actually, the guy that gave the night flying seminar at RFC (sorry, I don’t remember his name) was saying that something wicked happen with his GPSs one evening.  He had a fix, a hand held & is iPhone GPS & all three failed at the same time. 

He took off from Rockcliffe & was in route to Kingston.  It happened after approx 15 minutes.  All three went blank saying they lost sat signal.  When he got closer to Kingston everything came back to normal.
 
The same happen on its way back to Ottawa. 

After some reflection on what just happen to him he came to the conclusion that once the phones (they were two in the plane) lost their ranged they went on booster mode which he thought that interfere with the GPS units.
Marc Philippe
PPL-SEL

Offline ckiff

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Re: Interfering With Flight?
« Reply #10 on: February 07, 2011, 06:57:48 PM »
With regards to GPS, if all the GPS devices in the plane loose signal, it's probably a satellite issue.

If you're going to use GPS, it's a good idea to do a bit of reading in how it works. It's all based on time and where the satellites are supposed to be at a given time, and the time it takes for the signal to go from the satellite to your antenna. To get a two dimensional position (latitude and longitude), you need 3 satellites. To get a 3D position (ie altitude), you need 4 satellites... minimum. But in reality, this only works if the satellites are well spread out. If you have 3 satellites all close together in the sky, your GPS receiver won't be able to get an accurate enough position to tell you anything. The best position you can get with the minimum satellites, is to have them as spread out as possible, and closer to the horizon. But your antenna has a limit to how far over to the horizon it can see, and banking the aircraft can block the view to some satellites as well. All in all, the more satellites the better.

So although GPS is fairly reliable, there are times when there are not enough satellites, or they are not positioned properly in the sky, to give you an accurate position, sometimes so bad that your GPS won't even give you a position. The best way to check this is to go to the satellites page in your GPS and see how many satellites should be visible, and the health of that signal.

This is why when using a GPS for IFR, and doing an approach, you have to check that the integrity of the GPS signal at your destination, at the time of your arrival, is acceptable. This is called RAIM prediction, and any IFR GPS has this function. If you do not have acceptable integrity, or RAIM, then you cannot conduct the approach.

Anyways, all this to say, just because all your GPS receivers seem to loose signal, it doesn't mean this is caused by something like a cell phone. If each receiver has its own antenna, and each has a clear view to the sky, and you still can't get a position, then it's most likely a satellite issue. In a few minutes the more satellites might be in view, or they might become more spread out.
Chris Kiff
ATPL / Class 1 Instructor / Ex-RFC Instructor / Current Airline Pilot

pcarscallen

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Re: Interfering With Flight?
« Reply #11 on: February 11, 2011, 03:47:48 PM »
M Phillipe, I agree with Chris regarding the issues your friend had with his GPS.  Most likely a satellite issue.  I find that quite a few people using GPS systems do not read the manuals and so are sometimes caught out by errors or issues that can occur, also there may have been a NOTAM regarding GPS outages which he did not read; I am assuming he was flying VFR and therefore would have had a chart to back himself up.

On the other issue of phones causing interference, I have just read some articles which are reporting (unconfirmed at this point) that the new 4G cell towers are causing GPS units to black out, apparently this is due the the 4G system using part of the spectrum which sits nexts to the GPS spectrum.  Further testing has to be done in order to confirm these incidents but the few that have occured have been out to 5 miles from a 4G tower, obviously if this is confirmed it is going to mean some serious issues for both aircraft operators (airlines, private owners, etc) and cell phone companies.

Offline M Philippe

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Re: Interfering With Flight?
« Reply #12 on: February 11, 2011, 05:45:31 PM »
M Phillipe, I agree with Chris regarding the issues your friend had with his GPS.  Most likely a satellite issue.  I find that quite a few people using GPS systems do not read the manuals and so are sometimes caught out by errors or issues that can occur, also there may have been a NOTAM regarding GPS outages which he did not read; I am assuming he was flying VFR and therefore would have had a chart to back himself up.

On the other issue of phones causing interference, I have just read some articles which are reporting (unconfirmed at this point) that the new 4G cell towers are causing GPS units to black out, apparently this is due the the 4G system using part of the spectrum which sits nexts to the GPS spectrum.  Further testing has to be done in order to confirm these incidents but the few that have occured have been out to 5 miles from a 4G tower, obviously if this is confirmed it is going to mean some serious issues for both aircraft operators (airlines, private owners, etc) and cell phone companies.


I don't know the system enough to argue on the issue.  Make sence for sure.

On the other hand G4 is already around the Ottawa area & that might have played in the instructor incident.  I have no idea.  I was just relating what was said on that evening siminar.  Here's one article on the G4 subject.  Sorry, stoled it from another aviation forum. :-)


http://www.gpsworld.com/gnss-system/news/data-shows-disastrous-gps-jamming-fcc-approved-broadcaster-11029?utm_source=GPS&utm_medium=email&utm_campaign=Navigate_01_31_2011&utm_content=data-shows-disastrous-gps-jamming-fcc-approved-broadcaster-11029
Marc Philippe
PPL-SEL

 

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