GPS's on Aircraft

[Ben Pid]

Just a query really, mainly for all those GPS techies out there...

 

Was wondering as you cant use a mobile phone on an aeroplane because of it interferring what would happen to the satalite guidance systems on an aeroplane if you turned on your GPS mid-flight?

 

Was just thinking of doing this onthe way back from Germany...didnt for obvious reasons but what would happen? would the plane crash or would the GPS work?

 

Pid

 

Ben Piddington http://www.buckscaching.co.uk

[+Huga]

GPS receivers are exactly that - receivers. They are almost 100% passive (in that nothing has zero emissions). I heard a source saying they have similar emissions to a pocket calculator...

 

Switching one on will not do any harm at all to the aircraft. It won't interfere with any of their systems, and won't 'sap' any of the sateliite signal that the aircraft may be picking up. Mobile phones have strong emissions, which is why they are not allowed. They may also pick up the aircraft communication frequencies, which are illegal to listen to. Plus, when in weak signal areas, mobiles ramp up their output, which makes them even worse on planes.

 

HOWEVER. Most aircraft operators still don't allow GPSrs to be operated on their flights because they have paranoid fears that they will interfere with the nav system of the plane. On a recent flight from Aberdeen to Heathrow, I asked the cabin crew if I could use mine, and they said no. So I used it anyway Was interesting to see the path that the plane took over the UK to get from Aberdeen to London, I'll say.

 

I would suggest using it (discretely) until someonecomplains. I've heard reports that when the cabin crew have discovered people with GPSrs, they tell the pilot, who gets all excited and demands to see the receiver in operation

 

--

**Mother is the name of God on the lips of all children**

[+Nia]

I use my e-trex on planes and there have been no problems once i explain its a GPS and not a dreaded Mobile phone

 

Tech-no notice

[+dylanhayes]

I was told by somebody who worked in the aviation industry in southern africa that pilots often used to use mobiles on board aircraft as comms with the tower in some of the backwater parts of africa were bad to none existant as the airfields radio would frequently be broken, but oddly enough they had mobile coverage, as in many places mobiles have leapfrogged landlines.

He also mentioned the mobile operators didn't like mobiles on aircraft as the phone could be in many cells at once being in such an elevated position, and that in combination with the high speed which resulted in cells being picked up and dropped confused the network.

On the otherhand if the pilot decides to risk jamming their own avionics that is their choice, but they would prefer the passengers refrain from this. As yet there is no confirmed crash caused by mobiles after all...

 

*******************************************************

Don't mention the mushrooms

*******************************************************

[+The Hornet]

Funnily enough I e-mailed Virgin Atlantic about this subject only the other day as we're off to the West Indies on Friday. This is their reply...............

 

---------------------------------------------------------------------

 

Dear Peter

 

Thank you for your e-mail.

 

We do not have a list of permitted electronic items which can be carried as

most items will not present a problem. Please bear in mind the following if

carrying electrical items:

 

Brand new electrical items (still in boxes) such as hair dryers and travel irons etc. should be carried in hand baggage (on board the aircraft). Old electrical items can be carried either in the hold or the hand baggage. Any electrical items must belong to the passenger. Electrical items in checked in baggage must be declared to the check in agent. They will then be asked additional security questions and their baggage may need to be screened.

Laptops and GPS systems can be carried and used in the cabin but must be switched off during take off and landing.

I hope this information is helpful. If you have any further questions please contact us again.

Kind regards

 

Kathy

Customer Services

 

---------------------------------------------------------------------

 

It has also been discussed at length in the following thread http://opentopic.Groundspeak.com/0/OpenTopic?a=tpc&s=1750973553&f=3000917383&m=6140902584

_________________________________________________________

 

It is better to regret something you did, rather than to regret something you didn't do.

[+The Wombles]

Fear of the unknown (and lack of knowledge of transmitter power, frequency spread and Electromagnetic Susceptability of aircraft components) combine to result in the easy answer of "No".

 

In Fact, although all receivers also cause low level transmission (this is a function of the Oscillators used in the receiver circuitry), the emission power is so low that it's highly unlikely to cause a problem. This is recognised in EU legislation on Electromagnetic Compatability which has a lower limit on the "power" (field strength) which is a problem.

 

In practice, I used GPS on all flights before 9/11 but haven't used them at all since, because too many people are nervous.

 

I still have a max speed of 687mph recorded on a 747 coming back from the States (Gulf Stream tailwind). It also avoids Nicky asking about other max speeds which I may have inadvertently recorded on the motorway....

[+Masher]

Hey! How comes you lot all managed to get a signal?

 

When I tried mine on a recent flight, I couldn't acquire even one satellite. Not even by putting it up against the window! Were you all in Sopworth Camels, or summat?

 

Mark

----------------------

I was technical once

[+Huga]

Getting a signal is the hardest bit. Luckily on the only flight I've been on (technically two, to Aberdeen and back) since getting my GPSr, I've been next to the window. Managed to prop the eTrex on the armrest so it had maybe 4 to 6 satellite locks.

In the middle of the plane you have no hope I guess. Too much metal.

 

Was vaguely shocked yesterday to switch my eTrex on inside our garage, to get 3 satellite locks and a position accuracy of 186ft. Not bad considering that room has no windows. Just a very thin roof I guess.

 

--

**Mother is the name of God on the lips of all children**

[+jeremyp]

I've read lots of discussions about this but I am not an electronics engineer.

 

Firstly, all electrical items emit some radio frequency noise when switched on. Obviously, mobile phones emit a lot of RF noise because they have to. So there is a small theoretical risk to aircraft systems from any electrical items. However, in practice under normal circumstances it is effectively zero, even from a mobile phone. I left mine in my handbaggage once and forgot to switch it off - the plane didn't crash. I also did an experiment by placing it right next to my PC and ringing it. The monitor had some intereference but the PC didn't crash.

 

Secondly, there is a problem with a mobile in the air that it has line of sight to so many transmitters that there is potential to saturate the system. I guess that this is because the phone is continually switching between transmitters. I don't think a single phone could bring down a phone network, but if they weren't banned, each plane would be carrying between 100 and 500 mobile phones all trying to saturate the system. This may also apply to the interference argument. One phone may not bring down a plane, but perhaps 200 can.

 

Passive electrical items are obviously not dangerous because planes fly all the time with 100s of laptops, Walkmans, in flight videos etc switched on. I don't see why they should be banned during take off and landing either except that they are usually heavyish objects in hard plastic cases which could do a lot of physical damage if rattling around loose in a violent manouevre.

 

With respect to GPS receivers, some airlines ban them and some don't. You should ask the aircrew what their policy is. No matter what the airline says, the captain has ultimate authority on his/her plane.

 

Personnally, I never bother as I almost always go for an aisle seat. With an eTrex I'm sure there's no chance of getting a signal away from a window and the altimeter on mine is worse than useless since the cabin is pressurised to an effective height of about 2000 metres.

 

-------

jeremyp

The second ten million caches were the worst too.

http://www.jeremyp.net/geocaching

[Ben Pid]

Hmmmmm intersting stuff this.

 

I wonder what would happen if the satalite navigation systems on a plane actually did for another reason break down and the captain calls over the microphone.....anyone with a GPS please help me. Crikey we would all be classed as Heros!

 

LoL. I am going to try this next time I fly.

 

Ben Piddington http://www.buckscaching.co.uk

[+The Wombles]

quote:

---

Originally posted by jeremyp:

Secondly, there is a problem with a mobile in the air that it has line of sight to so many transmitters that there is potential to saturate the system. I guess that this is because the phone is continually switching between transmitters. I don't think a single phone could bring down a phone network, but if they weren't banned, each plane would be carrying between 100 and 500 mobile phones all trying to saturate the system. This may also apply to the interference argument. One phone may not bring down a plane, but perhaps 200 can.

---

 

The limitations on phones are a result of the potential for interference between the phone's high radiated power (4W) and the aircraft's electronics. Many aircraft fly-by-wire (rely entirely on electronics rather than a mechanical connection between pilot and control surface eg wing). These signals run along the body of the aircraft, acting as an aerial in their own right, and potentially receiving your mobile phone signal. Result: very confused aircraft.

 

(Incidentally, a single mobile phone can't bring down a network and nor can multiple phones - there are built in lock-out functions).

 

quote:

---

Originally posted by jeremyp:

Passive electrical items are obviously not dangerous because planes fly all the time with 100s of laptops, Walkmans, in flight videos etc switched on. I don't see why they should be banned during take off and landing either except that they are usually heavyish objects in hard plastic cases which could do a lot of physical damage if rattling around loose in a violent manouevre.

jeremyp

---

 

Jeremy mentioned that all electronic equipment emits electrical noise. This noise varies depending on the device, some are badly designed and emit a great deal of noise.

 

At take off and landing, the aircraft is often reliant on electronic systems such as automatic landing. If a problem occurs then there may not be any time for pilot intervention because you're so close to the ground. Nobody can test every device in the world with every variant of aircraft.

 

Therefore they played safe and banned everything. As an Electronics Engineer who once designed radar for a living, I'm pleased about that.

 

BTW, Huga is right about the problems of getting a signal in flight. I've only ever managed to get a signal by holding the GPS to the window; not very subtle.

[+John Stead]

I recently had no problem on a Czech flight to Prague and produced a good track from Manchester (and back) with few dropouts. A window seat is essential and holding to the glass to get the first fix but after that it worked quite happily on the armrest next to the window. This was with a Vista on a 737.

 

The next one will be better!

[+dancalvert]

I flew RyanAir to Graz (Austria) a couple of weekends ago, and they were cool about me using my Vista on the aircraft (737-800). I was on top the wing by the window (Left Side), and managed to get a good enough lock for showing off purposes.

 

Let's all fly RyanAir

 

Dan C

[+Travers]

I know that RyanAir is a low cost airline, but making you side on top of the wing seems a bit much!

 

Still, a good idea for ensuring a signal I guess.

[+jeremyp]

He got one of the best seats though - by the window - the flight attendants could at least pass food and drinks out to him.

 

-------

jeremyp

The second ten million caches were the worst too.

http://www.jeremyp.net/geocaching

[timnerla]

Two things on this:

 

Firstly, I've done it many times now without causing any planes to crash.

 

Secondly, aircraft systems are relatively well shielded from the type and levels of RFI that are produced by a gps. Mobiles are fundamentally different in that they are transmitters.

 

Also, the pilots are trained (and regularly practice for) total manual reversion situations and anomalies in the a/c electronics, so any problems will either be worked around, the offending piece of avionics ignored or other action will be taken.

 

Now this is not to mention the specific cases of fly-by-wire systems, including flight controls and FADEC-type remote engine control systems. If they run by fibre optics (as many do), then the issue is irrelevent. However, if they're wires they are still well sheilded, as the engine nacelle still generates a lot of potential RFI: there are alternators in there that may well kick out 415 volts, and the engine starting system uses electrical discharge at potentially 20kv. Again, worst case from the engine pov would be undemanded inputs, in which case the crew would shut it down and divert.

 

Oh, and don't forget that to control the ailerons, flaps, speedbrakes et al, the flight controls also have to pass the engine nacelle, so will be well sheilded.

 

[This message was edited by Tim_n_Erla on November 07, 2002 at 02:28 AM.]

[el10t]

The general concensus from the highly knowledgeable people here seems to be that use of a GPS could not possibly bring down an aircraft due to electrical shielding, the devices passive nature etc. I agree with all this but there are also two points to consider above this when deciding whether or not to use your GPS in a plane:

 

the Captain has the final say in whether you can use it or not. He/she is in charge of the plane in flight. If he/she would prefer you not to use it then you should not use it, despite all the arguments that it can't possibly do any harm;

there may well be some very nervous passengers on the flight who do not understand electronics as well as others, and the sight of someone playing with an electrical device would make them very uncomfortable. You are unlikely to convince a very nervous person that it is perfectly safe to use and so it would be polite to refrain from using it in this instance.

 

Given both of these, its probably best to ask the cabin crew whether or not you can use it before you do so.

 

Rich

mobilis in mobili

[philgn]

I have used my streetpilot on aircraft many times and it is very informative, I think all you would be short of is the windspeed,to fly and navigate the aircraft. I used to do it descreetly but thats difficult, as it has to be held at the window, I now ask the steward to ask the captain if its ok with him, all have allowed it, some with caution, saying that if there is any abnormality I will be asked to turn it off, on the last flight the cabin crew were fascinated by it.If you put in the destination airport, you would get an accurate time of destination, if the pilot went as the crow flies, you also see rotation speed,ground speed, landing speed, true altitude,and direction, I highly recommend it.

[+The Wombles]

I came across this is it safe?

 

which covers all the relevant dsicussion of this thread - also check out which aircraft to use your GPS on

 

Dave

[+The Merman]

I ask the cabin staff to:

A. Ask the pilot if it is ok

B. Ask for a lat long of the destination airport.

 

The pilot on my last flight across the Atlantic even sent back a steward with a waypoint for me as he was diverting over Greenland for strong winds and thought I would like to recalculate.

As it happens I always put route markers in so that I can see the great circle when I plot it on a chart later.

 

The airline in question is US Airline and they are very helpful.

 

I woke this morning and my boat was not rocking...for one horrid moment I thought I lived in a house!