Could a handheld GPS interfere with the INS system?
Fly Conventional Gear
Thread Starter
Join Date: May 2007
Location: Winchester
Posts: 1,600
Likes: 0
Received 0 Likes
on
0 Posts
Could a handheld GPS interfere with the INS system?
Someone on the SLF forum asked about GPS use during an airline flight...and I was wondering:
Could a GPS system like a Garmin 496 (or similar) interfere with any of the equipment in the cockpit? I would have thought that since they are usually used in aircraft anyway there wouldn't be a problem.
I take it airliners still use GPS updated INS rather than just straight GPS?
Could a GPS system like a Garmin 496 (or similar) interfere with any of the equipment in the cockpit? I would have thought that since they are usually used in aircraft anyway there wouldn't be a problem.
I take it airliners still use GPS updated INS rather than just straight GPS?
Join Date: Jan 2007
Location: UK
Posts: 103
Likes: 0
Received 0 Likes
on
0 Posts
I hope the answer is 'no' ! I use my Garmin on most flights and it is very rare to find explicit advice in the inflight mag or elsewhere on whether or not it is prohibited. They all go on about mobile phones and now also anything with earphones, but rarely mention GPS.
On a recent BA flight the announcement was to 'check in the Highlife Mag for more details' ...but there were none.
So until I hear otherwise I will still be the pillock who taps on the cockpit door and whispers, "psst, turn left at Belgium, mate".
On a recent BA flight the announcement was to 'check in the Highlife Mag for more details' ...but there were none.
So until I hear otherwise I will still be the pillock who taps on the cockpit door and whispers, "psst, turn left at Belgium, mate".
Join Date: Mar 2006
Location: USA
Posts: 2,515
Likes: 0
Received 0 Likes
on
0 Posts
As a rule, devices that transmit or receive data on the electromagnetic spectrum may cause interference. Portable radio, TV, Bluetooth, Wi-Fi, and GPS are all potential sources of interference. The other day I was flying and the DME readings were all over the place. I remembered that my cell phone was left on. I turned it off and the DME eventually settled down. Please, unless you're flying a glider or light sport aircraft, keep your GPS off. If you really want to know your speed, ask before or after the flight. The crew will gladly entertain such questions.
Fly Conventional Gear
Thread Starter
Join Date: May 2007
Location: Winchester
Posts: 1,600
Likes: 0
Received 0 Likes
on
0 Posts
unless you're flying a glider or light sport aircraft, keep your GPS off.
I asked the question not because I want to use GPS during a commercial flight but because if it has the potential to interfere with airliner systems it has the potential to interfere with the avionics in my plane as well...which is very worrying.
Join Date: Oct 2002
Location: aaa
Posts: 266
Likes: 0
Received 0 Likes
on
0 Posts
Im probably wrong but I was under the impression the a GPS unit only received the signal from the satelite and did not transmit anything! And as such the only risk of interference would be from the electromagnetic field generated by electronics. i.e. very small
Join Date: Mar 2007
Location: USofA
Posts: 1,235
Likes: 0
Received 0 Likes
on
0 Posts
Small point of order here but GPS nor any ground based nav aids actually update INS. The INS, IRS ADIRU etc. only interface with the respective FMS and do not receive any updates directly from any ouside sources. If your really brave you can do an INS update by flying over a navaid and do a manual update, but that's not the same as you had implied. For all of you who that anyway, forgive me for being redundant.
Fly Conventional Gear
Thread Starter
Join Date: May 2007
Location: Winchester
Posts: 1,600
Likes: 0
Received 0 Likes
on
0 Posts
Small point of order here but GPS nor any ground based nav aids actually update INS. The INS, IRS ADIRU etc. only interface with the respective FMS and do not receive any updates directly from any ouside sources. If your really brave you can do an INS update by flying over a navaid and do a manual update, but that's not the same as you had implied. For all of you who that anyway, forgive me for being redundant.
Join Date: Sep 1998
Location: wherever
Age: 55
Posts: 1,616
Likes: 0
Received 0 Likes
on
0 Posts
While your GPS is not an active transmitter it is classified as a passive transmitter. I read some guidance from one manufacturer that said they should not be allowed. Basically anything with an antenna is a risk. Of course how much of a risk is questionable but if it hasn't been specifically approved then you are adding risk by using it.
Quote Spooky: "Small point of order here but GPS nor any ground based nav aids actually update INS. The INS, IRS ADIRU etc. only interface with the respective FMS and do not receive any updates directly from any ouside sources."
Depends on the system. On the three large aircraft types I have flown which had GPS updating, the IRSs all used very different methods of updating position. My current type uses the FMC to produce a blended position which is weighted depending on the quality of the information fro a Multi Mode Receiver which has an inbuilt GPS along with a VOR, DME and ILS. The FMC tells you on the progress page which position it is using, it's nearly always 'GPS Primary'. The type before that used an IRS position which was updated by GPS and the type before that had an IRS with a GPS embedded in it, so the IRS position itself was a blended position.
From my experience, I would doubt a GPS set would disrupt the aircraft electronics at any stage of the flight. But of course you should pay regard to the current airline policy. Mine tells the passengers, 'No electronic items are to be used until the seat belt signs are turned off after take off - and they must be turned off again when the seat belt signs are back on for landing".
But also, I haven't found a GPS set which works in a cabin. Not that I've tried very often!
Depends on the system. On the three large aircraft types I have flown which had GPS updating, the IRSs all used very different methods of updating position. My current type uses the FMC to produce a blended position which is weighted depending on the quality of the information fro a Multi Mode Receiver which has an inbuilt GPS along with a VOR, DME and ILS. The FMC tells you on the progress page which position it is using, it's nearly always 'GPS Primary'. The type before that used an IRS position which was updated by GPS and the type before that had an IRS with a GPS embedded in it, so the IRS position itself was a blended position.
From my experience, I would doubt a GPS set would disrupt the aircraft electronics at any stage of the flight. But of course you should pay regard to the current airline policy. Mine tells the passengers, 'No electronic items are to be used until the seat belt signs are turned off after take off - and they must be turned off again when the seat belt signs are back on for landing".
But also, I haven't found a GPS set which works in a cabin. Not that I've tried very often!
Nemo Me Impune Lacessit
Join Date: Jun 2004
Location: Derbyshire, England.
Posts: 4,091
Received 0 Likes
on
0 Posts
Surely the following post by radeng in the Pax & SLF Forum answers the question: (Including you, Doors to Manual 
)
radeng
Over 250 posts so far. Perhaps I should click here and order a Personal Title
Join Date: May 2001
Posts: 414
If the GPS receiver is a direct conversion type, then the biggest possible cause of interference is to the on board GPS. Not desirable. But if it's a superhet, then we have a potential problem. If it meets FCC (US) requirements on oscillator radiation, it could well have an Intermediate Frequency such that the local oscillator blocks a DME channel. If it meets EU standards, possibly not - but only possibly, depending upon which stanadrds the manufacturer has decided to declare it compliant to.
As far as cell phones are concerned, any LO radiation if the receiver uses high side injection could kill a DME channel. A complication arises in that the immunity of cabling on a nice new aircraft is quite likely to be different to that on a 10 or 20 year old aircraft where corrosion, movement etc have happened.
The problem is that as far as aircraft systems are concerned, you KNOW what frequencies are involved. Bringing in unknowns (because you DON'T know the frequency plan of every possible bit of equipment) is another matter. Add to that the fact that there isn't just the fundamental radiation to worry about, but the presence of intermodulation products when authorised transmissions are made from the aircraft, there is a VERY good reason for banning the use of these things.
If you wonder about my qualifications, 'radeng' is a reduction of 'radio engineer'.
)radeng
Over 250 posts so far. Perhaps I should click here and order a Personal Title
Join Date: May 2001
Posts: 414
If the GPS receiver is a direct conversion type, then the biggest possible cause of interference is to the on board GPS. Not desirable. But if it's a superhet, then we have a potential problem. If it meets FCC (US) requirements on oscillator radiation, it could well have an Intermediate Frequency such that the local oscillator blocks a DME channel. If it meets EU standards, possibly not - but only possibly, depending upon which stanadrds the manufacturer has decided to declare it compliant to.
As far as cell phones are concerned, any LO radiation if the receiver uses high side injection could kill a DME channel. A complication arises in that the immunity of cabling on a nice new aircraft is quite likely to be different to that on a 10 or 20 year old aircraft where corrosion, movement etc have happened.
The problem is that as far as aircraft systems are concerned, you KNOW what frequencies are involved. Bringing in unknowns (because you DON'T know the frequency plan of every possible bit of equipment) is another matter. Add to that the fact that there isn't just the fundamental radiation to worry about, but the presence of intermodulation products when authorised transmissions are made from the aircraft, there is a VERY good reason for banning the use of these things.
If you wonder about my qualifications, 'radeng' is a reduction of 'radio engineer'.
Join Date: Aug 2005
Location: Birchington, Kent, England
Age: 82
Posts: 176
Likes: 0
Received 0 Likes
on
0 Posts
Contacttower
"I would have thought that since they are usually used in aircraft anyway there wouldn't be a problem."
To be blunt, but I hope not unkind, what you think is not relevant. Aviation legislation prohibits the use of any electronic/electrical equipment on aircraft for which that aircraft is not approved. The approval may be a general one, as in mobile phones, or may be more specific.
On a technical note, there are many aircraft systems that are susceptible to interference from electromagnetic interference "EMC", FADECs are a particular case. In the modern world, most electronic devices are digital such as laptops, GPS, mobiles, calculators, etc., and clearly an aircraft and its systems cannot be tested for interference from all specific devices.
You can imagine the case where "Doors to Manuel" is sat in the back of a nice modern twin donk and decides to switch on his GPS. Immediate effect, both FADECs cough and splutter and the wicks go out. As far as I can see, the only good thing that will come out of the scenario is that he will know precisely where the crash is.
Bottom line, any equipment to be used on an aircraft must have been tested and proven not to interfere with aircraft and its systems. That is an expensive business but cheaper than finding out the hard way.
"I would have thought that since they are usually used in aircraft anyway there wouldn't be a problem."
To be blunt, but I hope not unkind, what you think is not relevant. Aviation legislation prohibits the use of any electronic/electrical equipment on aircraft for which that aircraft is not approved. The approval may be a general one, as in mobile phones, or may be more specific.
On a technical note, there are many aircraft systems that are susceptible to interference from electromagnetic interference "EMC", FADECs are a particular case. In the modern world, most electronic devices are digital such as laptops, GPS, mobiles, calculators, etc., and clearly an aircraft and its systems cannot be tested for interference from all specific devices.
You can imagine the case where "Doors to Manuel" is sat in the back of a nice modern twin donk and decides to switch on his GPS. Immediate effect, both FADECs cough and splutter and the wicks go out. As far as I can see, the only good thing that will come out of the scenario is that he will know precisely where the crash is.
Bottom line, any equipment to be used on an aircraft must have been tested and proven not to interfere with aircraft and its systems. That is an expensive business but cheaper than finding out the hard way.
Join Date: Oct 2003
Location: Shropshire, UK
Posts: 10
Likes: 0
Received 0 Likes
on
0 Posts
Off at a tangent here, but I once had a girlfriend who had a cochlear implant (effectively bionic hearing). A magnet and electrodes are implanted within the head - the purpose of the electrodes are to stimulate the cochlear thus allowing the deaf to hear (supposing the auditory nerve is OK), and the magnet is there to hold a transmitter firmly in situ outside the skull.
The advice given by the cochlear implant centres is that this device should be turned off for TO and landing however when asked, neither Boeing or Airbus provided a conclusive answer. To me this seemed to be a problem as here was a SLF who needed to be transmitting in order to hear the safety briefing.
So
Not quite the same, but we did about 2.5 hours of testing with her in a Cherokee - try as we might, it was impossible to get her to interefere (well, interefere with the avionics - she was a natural pilot when interefering with the controls, and incidentally the deaf who have hearing corrected with a cochlear implant are NOT precluded from a class 2 medical).
The next step was on an A320. I was also SLF on this occasion, and pre departure talked through my tests with the P1. The result was that he was happy to contine our test on this flight. We put her "down the back", as far away from the e-bay as possible. All was fine.
Its just a thought should anyone encounter a cochlear implant PAX in the future.
And one other point - I have no idea what frequency range these contraptions work within, but the various cochlear implant centres are always willing to field intelligent questions.
The advice given by the cochlear implant centres is that this device should be turned off for TO and landing however when asked, neither Boeing or Airbus provided a conclusive answer. To me this seemed to be a problem as here was a SLF who needed to be transmitting in order to hear the safety briefing.
So
Not quite the same, but we did about 2.5 hours of testing with her in a Cherokee - try as we might, it was impossible to get her to interefere (well, interefere with the avionics - she was a natural pilot when interefering with the controls, and incidentally the deaf who have hearing corrected with a cochlear implant are NOT precluded from a class 2 medical).
The next step was on an A320. I was also SLF on this occasion, and pre departure talked through my tests with the P1. The result was that he was happy to contine our test on this flight. We put her "down the back", as far away from the e-bay as possible. All was fine.
Its just a thought should anyone encounter a cochlear implant PAX in the future.
And one other point - I have no idea what frequency range these contraptions work within, but the various cochlear implant centres are always willing to field intelligent questions.
Join Date: Aug 2001
Location: Newcastle upon Tyne UK
Age: 67
Posts: 132
Likes: 0
Received 0 Likes
on
0 Posts
The thing that worries me is that if there is a real possibility of mobile phones interfering with critical A/C systems, then I do not believe that the present procedures, which simply involve an announcement that all mobiles should be switched off whilst engines running to be sufficiently robust. I regularly travel as SLF on Airbuses, and it is a regular occurrence for PAX to remember to switch off phones during flight, or for phones to go off. This probably represents the tip of the iceberg. I have to confess that on one occassion I have also found after the flight that I had inadvertently forgotten to turn my mobile off. So even where there is no intention to deliberately keep one's mobile on, there will be a significant failure rate in compliance.
From my own experience on smaller A/C, I usually keep my mobile on as the last line of defence backup for Radio failure. (Being over cautious on all trips other than local instructing details I also have a hand held battery operated transceiver and GPS - Call me paranoid!). I only turn the mobile off if I'm doing a "critical" instrument approach in IMC conditions. The only interference that I have experienced is the pip pip in the headset, presumably the Mobile interacting to find the relevant cell transmitter. I accept however that an A/C like the PA31 has much less critical electronic dependancy than an Airbus which is completely fly by wire.
Perhaps cabin crew should check all mobile phones when they check the boarding passes? The difficulty with this would undoubtedly be delays to boarding, and arguments with owners of "multifunctional" devices which have a flight safe mode.
One further thought, it has been announced that certain carriers will be running services which are enabled to handle mobile phones in flight. How is this consistent with the previously stated interferences to DME/FADEC? Will there be better electronic isolation of the A/C systems to facilitate this?
From my own experience on smaller A/C, I usually keep my mobile on as the last line of defence backup for Radio failure. (Being over cautious on all trips other than local instructing details I also have a hand held battery operated transceiver and GPS - Call me paranoid!). I only turn the mobile off if I'm doing a "critical" instrument approach in IMC conditions. The only interference that I have experienced is the pip pip in the headset, presumably the Mobile interacting to find the relevant cell transmitter. I accept however that an A/C like the PA31 has much less critical electronic dependancy than an Airbus which is completely fly by wire.
Perhaps cabin crew should check all mobile phones when they check the boarding passes? The difficulty with this would undoubtedly be delays to boarding, and arguments with owners of "multifunctional" devices which have a flight safe mode.
One further thought, it has been announced that certain carriers will be running services which are enabled to handle mobile phones in flight. How is this consistent with the previously stated interferences to DME/FADEC? Will there be better electronic isolation of the A/C systems to facilitate this?
PPRuNeaholic
Join Date: Jun 2000
Location: Cairns FNQ
Posts: 3,255
Likes: 0
Received 0 Likes
on
0 Posts
I suspect that the really simple answer is that nobody wants to find out for sure because it MIGHT end the airline monopoly on telephone call charges. I think that, if anyone had ever wanted to run a properly constructed scientific trial on any PED (Portable Electronic Device), the first problem they'd encounter outside of the airline itself, is the myriad frequencies and potential interactions between the various types of PED.
Now, as one who designs instrument procedures, I know that the tolerances can (on occasion
) be right on the limit. Think about that for your next take-off and landing - then ask yourself... do I really want to jeopardise any of those OCCASIONALLY tight tolerances?
On a personal note, I don't think that anyone really knows the answer to this so it's undoubtedly safer to err on the side of caution. I'm not yet convinced, one way or the other on the issue of PEDs, but I sure don't want to find out the HARD way.
Now, as one who designs instrument procedures, I know that the tolerances can (on occasion
) be right on the limit. Think about that for your next take-off and landing - then ask yourself... do I really want to jeopardise any of those OCCASIONALLY tight tolerances?On a personal note, I don't think that anyone really knows the answer to this so it's undoubtedly safer to err on the side of caution. I'm not yet convinced, one way or the other on the issue of PEDs, but I sure don't want to find out the HARD way.
Join Date: Mar 2007
Location: USofA
Posts: 1,235
Likes: 0
Received 0 Likes
on
0 Posts
I have to call you on that one. There is no IRS/IRU/ADIRU that updates from any external source...in any civil aircraft, be it Honeywell, Litton, etc. The FMC (FMS) will up date from GPS/DME/LOC/VOR.
Can you expand on your aircraft type and specific model? I suspect it is either a 777 or 747 as both of these use the MMR. The question as I understood it was, can the IRS/IRU/ADIRS be updated by the GPS. To my knowledge the answer is No. The blended positions from the FMC (FMS) are not a result of any IRU, GPS updating, but rather a blened position as a result of all the information gathered. On the 777 you can see these individual values on the POS REF page along with the MAP Display.
Can you expand on your aircraft type and specific model? I suspect it is either a 777 or 747 as both of these use the MMR. The question as I understood it was, can the IRS/IRU/ADIRS be updated by the GPS. To my knowledge the answer is No. The blended positions from the FMC (FMS) are not a result of any IRU, GPS updating, but rather a blened position as a result of all the information gathered. On the 777 you can see these individual values on the POS REF page along with the MAP Display.
Last edited by Spooky 2; 11th Dec 2007 at 21:19. Reason: more info
Fly Conventional Gear
Thread Starter
Join Date: May 2007
Location: Winchester
Posts: 1,600
Likes: 0
Received 0 Likes
on
0 Posts
To be blunt, but I hope not unkind, what you think is not relevant. Aviation legislation prohibits the use of any electronic/electrical equipment on aircraft for which that aircraft is not approved. The approval may be a general one, as in mobile phones, or may be more specific.
Join Date: Apr 2004
Location: England
Posts: 29
Likes: 0
Received 0 Likes
on
0 Posts
Spooky,
Not sure that all civil aircraft do the GPS / inertial integration in the FMS. Check out the Nothrop Grumman LTN-101E, both in terms of what it does and what aircraft it's on.
Not sure that all civil aircraft do the GPS / inertial integration in the FMS. Check out the Nothrop Grumman LTN-101E, both in terms of what it does and what aircraft it's on.
Join Date: Mar 2007
Location: USofA
Posts: 1,235
Likes: 0
Received 0 Likes
on
0 Posts
Well after looking up as much as possible regarding the LTN-101E I can only see reference to "sole means of navigation with GPS accuracy". Typical double speak so just what is happening here that is unique to this design has escaped me? I suspect that the GPS is an integral part of the IRU technology and unlike the Honeywell product line which typically uses a data port, the Litton system has it integrated into the IRS???
Thanks for the reference!
Thanks for the reference!
Join Date: Jul 2000
Location: West
Posts: 399
Likes: 0
Received 0 Likes
on
0 Posts
Here is one airline's web site remarks concerning GPS.
You can use these while the plane is at the gate with the doors open, after the plane has taken off and reached its cruising altitude and before it begins to descend for landing, and after the plane has landed and is taxiing to the gate.
Personal digital assistants
Personal computer games
GPS (global positioning satellite) systems
Your flight attendant will announce when it is safe to use these devices.
You can use these while the plane is at the gate with the doors open, after the plane has taken off and reached its cruising altitude and before it begins to descend for landing, and after the plane has landed and is taxiing to the gate.
Personal digital assistants
Personal computer games
GPS (global positioning satellite) systems
Your flight attendant will announce when it is safe to use these devices.