Use of handheld GPS on board
 

Hello all

I fly as a PAX fairly frequently, and also being a PPL I usually drop my hand held GPS into my hand luggage.

I have used this on board several times (although never during take-off or landing) just out of curiosity to see where we are, our altitude and cruising speed etc.

I normally check with the cabin crew, who on occasions have checked with the flight crew to make sure it is OK, so far without any problems.

However, I used it this weekend on a flight from Spain to the UK (although I have to admit I did not OK it with the cabin crew) and a member of CC spotted it and asked me what it was. I told her it was a GPS and she told me in no uncertain terms to switch it off and that devices like this should NOT be used in flight.

Naturally I accepted what she said and complied.

However, I am curious - is there any guideline given to CC on this?

I saw a similar thread relating to airband radios, and can understand this not being acceptable to use on board, but surely a handheld GPS can not cause any problems, especially whilst in the cruise?

Regards

OM

Irrespective of any guidelines from Inter/National bodies and manufacturers and aircraft manufaturers, each carrier will make their own policy. Ask and if they say no to you playing a game of tiddlywinks on a plastic board - then that's the way it is!

You may travel on a code share flight of your regular carrier and they will have different regulations. And No it isn't supposed to make sense! :p

Absolutely. Though it is likely that you will get a more favourable response if you ask first - the cabin crew will then probably refer it to the flight crew, who are likely to know that GPS is a pretty passive system.

[pedantic ON]
Not that passive. AFAIK all modern radio receivers are superheterodyne receivers, which means they have a built-in oscillator which resonates at the reception frequency.

So they do radiate some (small) amount of energy.
[pedantic OFF]

I do agree however that it is much less than a cell phone trying to connect to the network (especially when it "sees" a dozen cells)

[Edited for spelling]

UK CAA specifically gave handheld GPS receivers the no-no about two years ago. If you've been getting away without so far its because the crews in question aren't aware of the restriction.

In this day and age, anything that looks "Technical" is threatning to the industry.
Does anyone really believe a scanner/receiver or GPS is going to make a difference... We use them all the time while flying ourselves........
Im sure someone will post to the contrary.

Carnage Matey: can you tell me where you heard about the UK CAA giving handheld GPS receivers the no-no?

I'm not disputing what you are saying, but I never heard of anything like that.

Regards

OM

The other week I spotted a guy using a GPS, and I checked with the Capt, who said it must be switched off. The guy did so, however he produced a sheet of A4 which listed the airlines that allowed a GPS to be used. The list was quite extensive and it included the carrier I work for.

Bought a new laptop lately, it comes with "air" mode, i.e push a key and all emmisions turned off.

Just wondered though, CC can't be expected to decide whether X laptop can be used and Y can't, so "air" mode is effectively useless.

Why don't the a/c manufacturers (both of them) deal with this by shielding etc?

As professional radio engineer, what worries me slightly about this is that nobody knows if any particular GPS receiver is or is not radiating a signal that can cause interference. European limits are somewhat more exacting than US ones, but the possibility still exists. Screening of a/c systems is fine, provided that you can guarantee the integrity of the screening a few years down line, but there's been some published material showing that in fact, you just can't give that guarantee in practice. This is because cables chafe and move slightly, connections partially break, and cable screens get damaged.

Probably the worst possible case is the portable FM broadcast receiver on an aircraft: there has been a number of documented cases of interference from their local oscillators, which, in Europe, can run quite high levels and still meet the regulatory requirements under the EMC Directive (I haven't looked up the FCC limits). The problem here is that local oscillator radiation falls nicely into the band for the VOR.

When I was working on the systems design of GPS receivers (which was admittedly some 15 years ago), we certainly came across one design of architecture where the ability to radiate a signal in the VOR band from a local oscillator in a multiple conversion superhet receiver was there: it may well be that architectures have moved on since then, but I'm still somewhat dubious. You only need a clock radiating the allowed -57dBm in the VOR or comms band near a cable from the a/c antenna that has had some damage to the screening braid, and you could have problems.

After GPS, I was heavily involved with some Wireless LAN development: we had a problem in doing Type Approval because the brand new laptop PC from well known Far Eastern manufacturer radiated so much rubbish so far outside the limits allowed that it failed our WLAN! And the manufacturer of the PC didn't want to know......so I'm a bit dubious about presuming that just because it's a type approved, CE or FCC or whatever marked equipment, that it's OK.

Just because you've got away with it so far doesn't mean you can be sure of carrying on doing that - it's a bit like visiting a brothel and taking no precautions. You may not catch anything this time, but keep going back and sooner or later........

Here we go again...

radeng - There are millions of light aircraft movements every year, many with the pilot carrying a handheld aviation GPS right next to the avionics.

You're reasoning suggests that these pilots are heading for the inevitable. When should that have started happening? A year ago? Two years ago? When will these "sooner or later" accidents start happening?

If the boss says no GPS, no GPS it is. But don't extrapolate that into a safety argument that is patently without foundation.

paulo Can see where you are coming from but surely the elctronics on your average commerical airliner is a bit more complex and sensitive than you average spam can...

Check your car handbook and look for the dire warnings about installing CBs, using mobiles etc and the risks to the electronics... covering their ar$es probably but then isn't that what the CAA is doing?

I trained as a radio officer in the merchant navy and my theory is a little rusty now but can remember the most unlikely things causing total S9 noise across incredible bandwidths.... I used to have a calculator with an LED type display which wiped out everything in the MF band!

I tried to use my Magellan GPS on a trans atlantic flight a couple of years back - it was new toy and I wanted to play - but it refused to lock onto any satellites.. those days pax were welcome on the flight deck and during the chat with the crew we came to the conclusion that the aircraft was a very effective Farday cage and that prevented the signal reaching the receiver. GPS signals are frightenly weak compared with other radio transmissions.

So I guess it's risk outweighs your fun!

pilotwolf - I think you are following an argument out of instinct rather than rational analysis. e.g. assuming that the previous claim of CAA involvement is true, that commercial airliners avionics is more susceptible to RF interference than light aircraft, etc.

Think it through. The industry nor the regulators feel that powerful, transmitting, mobile phones are a sufficient threat to be worth scanning for (the equipment to do that is available).

The industry and the regulators are happy for less powerful, transmitting, WiFi to be used on aircraft. (ref: Connexion by Boeing).

So, given that, do you really believe that non transmitting electronic devices are a safety factor? If you do, then I can guarantee you that you have compromised that view every time you have flown in the last 20 years.

As pilotwolf says, there's a lot of difference between the light aircraft avionics and the airliner. If you have interference from something local to the light aircraft on a VOR or a DME channel and you're not using VOR or DME, you don't have a problem. If someone in the back of an airliner has a machine that's causing a problem, how do you know when you're up front what is causing it?

Controlling multi system EMC is a difficulty, and adding factors that are unknown, even if unlikely to cause problems, isn't a good idea.

So, sorry, paulo, as someone who has been making a living out of radio engineering for over 40 years and doing EMC work for 15, I'm in favour of maintaining the ban.

The use of WLANs on board could be interesting if for some reason the clear channel assessment didn't function correctly and a 5GHz one transmitted in the middle of the MLS band. Although I believe that MLS is effectively dead in the US and isn't that widely used in Europe as yet - if it ever will be, since differential GPS or Galileo will do a cheaper job as far as the airport authorities are concerned.

radeng:

The ban you refer to: FAR or JAR?

paulo,

the current one on not allowing radio equipment in flight in passenger cabins.

Radiation from receivers has been a problem for many years. In 1939/40, the only receivers the Royal Navy had with adequate performance (B34) were removed from ships as quickly as they could be replaced by B28 receivers because of radiation.

During WW2, the Germans were misled about Coastal Command radar for some time by some RAF PoW's who told them that submarines were being detected by radiation from their radar detection receivers - which, of course, wasn't the case. As some radiation was detected when they looked for it, a whole new radar detection receiver got designed.

And as far as avionics EMC is concerned, one of the interesting ones these days is the Tornado, which is notoriously subject to EMC probelmm - don't fly one too near a broadcast station!

I'm not sure which European EMC standard a GPS receiver has to meet - if it's EN55013, then there's a definite potential problem. EN55022 isn't, I think, applicable. I'll have to ask a friend who does a lot of testing.

So an aviation GPS is not dangerous so long as you use it in the cockpit next to the avionics? :rolleyes:

I think you are presenting your own personal views as the views of the industry. They aren't. There are plenty of commanders who will be quite happy, if asked, for GPS units to be used in the passenger cabin.

There are also a small but growing number of operators who actively promote passengers bringing their own WiFi transmitting equipment on board, to use with their WiFi service.

In a few years from now, low power transmitting devices will be commonplace. A few people will be left grumbling that "it wouldn't have been allowed in my day" and the rest of the world will move on.

paulo ... as stated above its the not knowing there maybe a risk of interference - if you ve asked or there is equipment fitted the commander will be aware of the potential problem... And I guess any installed equipment would have to be tested and proved to be immune from causing interference.

Also consider this: A GPS causing nav aids/compass to be a degree or two out in your light aircraft probably won't cause any noticable problems over the ususal distances flown especially VFR, but compare than to one or two degrees over 1000s of miles..... 1 in 60 rule?

Just as an example... in a strong signal area where you mobile is operating at low power make a landline call with the mobile in your other hand and see what happens. Then imagine whats happening to comms, etc in the air when the mobile is operating at high power trying to lock onto a cell site.

We've been conducting unplanned experiments on the effect of in-flight electromagnetic interference for many years. Every commercial flight with more than a few dozen pax is almost certain to have one or more active mobile phones on board. Since we don't observe any ill effects, I'd judge that it's perfectly safe.

If any aviation authority thought that there was a serious risk, a requirement to scan for active mobiles (a quick and inexpensive operation these days) would have been introduced. I expect that, for a suitably large amount of $$$, the necessary work could be done to certify the safety of these devices, but it's in no-one's interest to spend the money!

except the airtime providers.... why aren't they pushing for a change in the regulations? Risk of being sued for an incident caused by cell phone EMC?