View Full Version : Use of GPS recievers by passengers

19th Apr 2003, 10:10
A friend who has a PPL was recently on a commercial flight and used a hand-held GPS receiver to monitor the progress of the flight. A member of the cabin crew asked him to switch it off as "it could interfere with the aircraft systems".

As he uses this in his own aircraft, he wondered what interference it could cause, as it is a receiver only and does not transmit any signal. He wonders how it can be safe to use in a Cessna 172 but not in a 737?

Over-zealous cabin crew? or am I missing something?

19th Apr 2003, 21:21
I'm certainly no expert in these matters but I can't see what possible 'damage' or interference this could have caused.

Bit of a knee-jerk reeacion by the crew I think.

Any experts out there?

Notso Fantastic
19th Apr 2003, 21:33
Cabin Crew are just taught that any little electronic devices held in your hand are 'bad' and must be stopped. There is no education about what is and is not acceptable. I have been stopped from using my little Pocket PC. Not a transmitter, but they do have Bluetooth and WiFi now which ARE! A little GPS looks like a mobile phone and could make someone else decide they will pull out theirs! So the only positive solution is to stop all use of such devices, which is sensible in your friend's case as handheld GPS doesn't work in aircraft cabins anyway- the antenna is shielded! (well mine didn't)

19th Apr 2003, 22:26
Agree with comments above regarding cabin crew not understanding what a GPS is or how it works.

I've had a pax tell the cabin crew to tell the flight deck how impressed he was at my 'route so far PA' as he had been monitoring our progress on his GPS. I always make sure that my 'current position PA' is correct but have heard some guys 'wing & a prayer it' & give a standard PA even though we've been flight planned a different route. Won't seem so professional if a pax has a GPS on them.

Let that be a lesson to us all, the punters are getting wise!

Hand Solo
20th Apr 2003, 02:39
I'm fairly sure the CAA issued a notice a couple of years ago banning the use of handheld GPS receivers in the cabin. It was also mentioned in a copy of the Balpa Log. A search of the Pprune archives should reveal the truth.

20th Apr 2003, 05:12
Thanks for the replies - pretty much as I thought, neither myself nor the guy who sits on my left with all the answers could think of a reason for switching off a GPS.

As far as reception goes, my mate had to hold it up to the cabin window to get any signal at all, which is probably what attracted the CC in the first place.

I can understand the principle of "if in doubt ask for it to be switched off", but I can't recall anything from balpa regarding GPS used by pax. The only stipulation in our pax safety brief is "the use of electronic devices during take off and landing", but that's more because we don't want laptops flying around the cabin when I smack it a bit too hard onto the runway.

20th Apr 2003, 05:30
From my Operating manual (revision date 1 MAR 03):

GPS receivers utilizing external wires (i.e. suction cups) may be operated while the boarding door is open. At times, during extended taxi delay, the Captain may authorize this type of GPS system to be operated. [In this event someone asks if PEDs can be used, the F/As ask us, and we make a PA authorizing their use until we get near the runway].

GPS receivers that do not utilize external wires may be operated at all times.

The cabin crew is responsible for explaining and ensuring compliance with the policies/regulations concerning the use of PEDs. Their guidance may come from government regulations or company policy. If it is thought the F/A is incorrect, most companies have a list of approved devices in their inflight magazines. That should clear up any misunderstandings. Perhaps there is also a web site that lists these approved PEDs.

I would be happy to see such a passenger in the cockpit early in the boarding process. Then I could brief the lead F/A that you will be using your approved GPS. We could also review our proposed route of flight/ North Atlantic Track together.

20th Apr 2003, 06:17
I think that any receiver that uses the 'Superhet' principle has a 'Local Oscilator' built in to it. This generates a signal, abeit very weak, which could be detected posible by the on board unit. It is, or was, in my day as an electronics guy, the signal indeed that the TV licence van used to check not just the fact you had a TV, but even which channel you where watching at the time of monitoring. :rolleyes:


20th Apr 2003, 08:05
I think Terry has a point. Another one is that a 737 (as old as it is) has somewhat more sophisticated systems than a C172. Since it's commercial with the 737s, I can understand that they don't like alien gadgets, that are similar to the onboard systems, used onboard. I also understand the argument that a GPS like this makes no more interference than a laptop but perhaps we're better off safe than sorry.
We've all forgoten to turn of our own cell phones more than one time so perhaps it's not that big a deal.

Captain Stable
20th Apr 2003, 17:49
I would be rather concerned about a GPS being used in the cabin - are you entirely sure it's entirely innocent, and the guy is not checking when to make his hijack move, or trying to ensure the bomb goes off at the right moment?

20th Apr 2003, 20:54
Captain Stable,

Come on, You could say that about any device.

Laptops could hold aircraft layout details to help the hijacker plan how the operation will work.

The same can be said for palm PC's, Some have infra-red which hijackers could use to send messages to each other.

Airband scanners could be used to monitor the progress of the flight to enable the hijacker to make their move.

At the end of the day if a highjacker wants to bring a flight down he or she (Yes, there have been female hijackers) will do it.
A hijacker strapped with explosives will simply blown themselves up and not worry too much where the plane is, They will not be fiddling around with GPS receivers.

Genghis the Engineer
20th Apr 2003, 22:24
By which logic a notebook, atlas, or two yoghurt cartons with a piece of string between them would be equally dangerous :confused:


21st Apr 2003, 05:34
Fine bit of paranoia, Capt. Stable, it seems to be the up-and- coming competitive sport.

Anything with the least bit of electricity in it has the potential (yes, that IS a pun) to interfere with avionics, but the likelihood of effect grows smaller in proportion to the power used. Recently manufactured commercial electronic devices which are not transmitters by nature are tested and engineered to be laregely non-interfering. Any device designed to transmit - whatever the frequency - has a greater potential. Computing devices with external cables have relatively great potential because they can randomly synthesize virtually any frequency in the range of interest, and the cables increase the ability to project those signals at powerful levels.

Assuming any small modicum of skill, your basic MK II electronic terrorist is going to ignore the cabin advisories and will use concealment anyway, so the announcements are mostly useful for ordinary folks who get a little carried away with their toys.

My experience is that your basic handheld GPS works quite well when plastered against a window in nearly all commercial aircraft, with the accurate groundspeed info especially handy.

25th Apr 2003, 00:13
Fuctifino but that's more because we don't want laptops flying around the cabin when I smack it a bit too hard onto the runway. Hey Fucto? Yeah, I'm talkin' to you. You smacka da wheels hard? I smacka ya face hard. :E

25th Apr 2003, 01:05
Just to confuse matters further, SAS is going to allow passengers with "air safe" mobile phones to use the various built-in functions (diary, games, etc) while in flight.

No phone calls, of course, but I can see FAs having to do a whole lot of explaining to passengers wanting to use their phones because other people are "using" theirs.