Gps Connect When Airborne?

[+TetrAmigos]

Just a question of possibility..

 

Is it even possible, per se, to gain a satellite lock onboard a commercial aircraft before the aircraft departs (eg. Boeing 737, et al) and keep the lock during flight (assuming satellites are in a position to accept it)? I use a bluetooth GPSr, so the unit is rather small. If it was possible, I would think it would be via this type of GPSr.

 

(Sorry, I realized after I clicked post that I'd placed this thread in the wrong forum. Moderator: Please move this topic to the appropriate place--my apologies)

Edited February 20, 2006 by Trace Amigos

[+WeightMan]

Given a window seat, yes this is possible. However, FAA regulations require that the GPSr be turned off during take off and climb. Airlines normally ask for ten minutes after takeoff. That applies to any device with an on/off switch according to most PA announcements that I have heard. Airlines other than US lines may have other requirements. As I recall from an internal flight within Australia devices were asked to remain off until the aircraft had reached cruising altitude.

[+Quiggle]

The FAQ (pinned at the top of the Getting Started forum) addresses your question in this post.

 

I'll move this over to the GPS Units and Software forum, perhaps others can expand on this and provide more information.

 

Edited February 20, 2006 by Quiggle

[+TetrAmigos]

Thanks!

[peter]

As Weightman indicated, this is generally allowed during the "cruise" portion of the flight, i.e. while above 10 kft in altitude. However some airlines restrict passenger use of GPS devices at all times. There's a list of airlines and their policies with regard to GPS use at:

 

http://gpsinformation.net/airgps/airgps.htm

 

I've never had a problem getting and holding a lock when by a window with regular handheld GPS receivers.

[+StagsRoar]

I think if you do a little homework prior to going on a flight - it may be helpful in establishing GPS usage on a flight - but I have found myself , it can depend on who you get on the day as I have been told "no" by both WestJet and Air Canada. Air New Zealand tend to have an aversion to them as well - but as I said it can be quite dependant on who you ask on the day. That being said mind you, I have gotten a good lock on a window seat with a patch antenna in the past. I wonder how it'll go with the new SIRF recievers - as judging from comments from users of these GPS units they seem to work pretty well when wandering around a Walmart store so I imagine that from within the fuselage of an Aircraft should be able to get a lock OK and you could have your GPS in luggage switched on and nobody would be the wiser. I have actually yet to see any evidence whatsoever that GPS units affect the electronics of any aircraft, ship, radio telemetry or nuclear silo whatsoever. Maybe someone could point me to some evidence that it does - I would be interested to hear! But it all seems pretty hyped over really, as if there was a definitive risk then I am quite sure ALL airlines would have a blanket ban on the things - which clearly there isn't.

[+ghs]

I too can get a lock on an airplane but only if I'm sitting in a window seat with the receiver right next to the window. (But even though using it was allowed and one flight attendent was actually fascinated by it, another one looked at me like I was going to stand up and say, "If you don't take this plane to Cuba, I'm going to tell you where you are!")

[+JDandDD]

I too have had good luck in the Window seat but nowhere else. Air Canada officially lets you use them but yes I have also been told no. For the most part its been no problem.

 

I'd be more concerned about a Bluetooth receiver on board than a handheld. Unlike the handheld GPSr, bluetooth is designed to put out an RF signal to about 30m. You really don't want to be doing that and possibly interfering with the plane's systems without absolutely being sure it isn't potentially harmful.

 

Anybody ever looked into the Bluetooth issue?

 

JDandDD

[+ghs]

I suspect the Bluetooth issue would be similar to the one with cell phones. I doubt that either would really cause a problem, but if a problem's going to occur, as you point out, it would be much more likely to be caused by a device designed to radiate than a passive device. (Can the Bluetooth feature, or whatever it's called, be turned off? I know of at least one instance when a cell phone was allowed during flight to play games because the user was able to show that the "phone part" was turned off.)

[+DavidMac]

I use mine all the time. I've only been able to get signal right up against the window, but there's only been one time that I couldn't see enough sattelites in the sky to get a lock (while flying somewhere over Canada, facing west or north, if I remember). Ironically, the only place in the plane where I've never been able to get a signal throug a window was in the cockpit- we speculated that it had something to do with a shielding layer on the glass designed to protect either the instruments from interference or the pilots from UV radiation.

 

There's only been one time I've been asked to put the GPS away by a stewardess who approached me with "is that one of those things that tracks the plane?" I began to explain that it was, and that their policy allowed me to use it at cruising altitude, but she insisted and I didn't want to push it.

 

The funny thing was, I had only turned it on to get a phone number off of the City Select map, and didn't even have the receiver portion on.

[+StagsRoar]

I'd be more concerned about a Bluetooth receiver on board than a handheld. Unlike the handheld GPSr, bluetooth is designed to put out an RF signal to about 30m. You really don't want to be doing that and possibly interfering with the plane's systems without absolutely being sure it isn't potentially harmful.

 

JDandDD

 

Good point - I can't say I had thought about Blue tooth but it certainly begs the question........!!

[djhobby]

On the last 2 trips Ive been on I've never gotten a lock, regardless of where I was sitting with my eTrex Legend. And that was on a total of 8 different planes. As far as airline regulations or what not, Ive never asked for permission, but on one AirTran flight I know a stewardess saw my GPSr but she never said anything to me about it.

[+JDandDD]

I suspect the Bluetooth issue would be similar to the one with cell phones. I doubt that either would really cause a problem, but if a problem's going to occur, as you point out, it would be much more likely to be caused by a device designed to radiate than a passive device. (Can the Bluetooth feature, or whatever it's called, be turned off? I know of at least one instance when a cell phone was allowed during flight to play games because the user was able to show that the "phone part" was turned off.)

Most flights I've been on in recent years make an announcement allowing PDAs, cells, and Treos, etc. 'as long as the transmit feature' is turned off. So you can make notes, compose email (not send), etc. as long as the device doesn't radiate.

 

Bluetooth GPS cannot be turned off and still have GPS function. The unit is either on or off.

 

I'm not technical enough about cell phones etc. to know for sure whether the issues are the same. Cell phones generally use 800-900Mhz and 1.85-199Ghz bands while bluetooth use the ISM band centred around 2.4Ghz. That's the same as some home phones. I don't know whether that has a different impact on plane equipment or not but it would sure be important to know before turning a bluetooth device on in a plane.

 

JDandDD

[+kgag]

Not to take this post in a completely different direction, but I have used mine on a plane (near the window) but it never seems to give accurate elevation information? Is there a reason for this? Anyone else have the same experience?

 

Thanks,

kgag.

[peter]

I'm not technical enough about cell phones etc. to know for sure whether the issues are the same. Cell phones generally use 800-900Mhz and 1.85-199Ghz bands while bluetooth use the ISM band centred around 2.4Ghz.

 

Cellular phones have always been somewhat of a separate issue. There is an FCC ban on use of the older 900 MHz phones when airborne because of concerns of interference with operation of the cellular networks. A single phone in the air could be heard by many separate cell towers and tie up lots of network capacity. Also the speed of travel is greater than these systems were designed to handle resulting in missed handoffs and further network congestion. The corresponding FCC regulations on the PCS band (1.9 GHz) do not include this prohibition, but many phones are dual-band capable and the user may not even know which frequency is being utilized.

 

I'd also note that several airlines are interested in allowing cellular use on board their planes and some tests have already been conducted involving the FAA, the FCC, PCS carriers, and the airlines. The idea is to have a mini-base station on the plane so your phone would communicate with it (and therefore set its output power to the minimum level) and then your call would be connected to the ground-based network over a separate high-speed wireless link.

 

So concerns about interference with aircraft systems seem to have been answered to the satisfaction of the airlines. I'd think the same is likely true of Bluetooth. Given the large numbers of laptops, PDAs, etc. that now include Bluetooth and with a mix of users who may not even be aware of when those ports are activated, the airlines had better be sure that those emissions won't interfere.

 

Of course this all applies to use while at cruising altitude (> 10 kft) where the airplane crew has more time to respond in the very unlikely event that there is some type of interference. Restricting use of passenger electronics during the more critical landing and take-off phases seems like a reasonable precaution even if the risk is low.

[peter]

Not to take this post in a completely different direction, but I have used mine on a plane (near the window) but it never seems to give accurate elevation information? Is there a reason for this?

 

Actually it's likely to be giving you more accurate elevation information than you're getting any other way. When flying above the 'transition altitude' (18000' in the US), airplane pilots all set their pressure-based altimeters to an assumed standard sea-level pressure of 29.92"Hg and the elevation indicated is then based on an assumed standard model of the earth's atmosphere. Now the real atmospheric conditions may be quite different from the standard model resulting in the indicated elevation being hundreds or even over a thousand feet different from reality. But as long as all pilots use this same system the vertical separation of aircraft is assured.

 

Note that at lower altitude, such as when preparing to land, the pilot gets an update from the ground as to the current barometric pressure at the airport and can recalibrate his altimeter so it'll be accurate in the vicinity of the airport.

[Neo_Geo]

Not to take this post in a completely different direction, but I have used mine on a plane (near the window) but it never seems to give accurate elevation information? Is there a reason for this? Anyone else have the same experience?

 

Thanks,

kgag.

 

If you have a model with a barometric altimeter, it is basing its elevation on the plane's cabin pressure. As you go higher and higher, the air gets thinner and thinner. The barometer senses the difference in the air pressure and that's how it knows what altitude you're at. Commercial airliner cabins are pressurized to around 5,000 feet so that passengers can all breathe in comfort without the aid of oxygen masks. The barometric altimeter is giving your altitude based on the plane's cabin pressure. Even though the plane is really at 41,000 feet, the GPSr thinks it's only at 5,000 feet. This is one of the reasons why I like the models that DON'T have sensors.

Edited February 21, 2006 by Neo_Geo

[+kgag]

Not to take this post in a completely different direction, but I have used mine on a plane (near the window) but it never seems to give accurate elevation information? Is there a reason for this? Anyone else have the same experience?

 

Thanks,

kgag.

 

If you have a model with a barometric altimeter, it is basing its elevation on the plane's cabin pressure. As you go higher and higher, the air gets thinner and thinner. The barometer senses the difference in the air pressure and that's how it knows what altitude you're at. Commercial airliner cabins are pressurized to around 5,000 feet so that passengers can all breathe in comfort without the aid of oxygen masks. The barometric altimeter is giving your altitude based on the plane's cabin pressure. Even though the plane is really at 41,000 feet, the GPSr thinks it's only at 5,000 feet. This is one of the reasons why I like the models that DON'T have sensors.

 

Cool thanks for the response, I kind of like it actually because it doesn't screw up my max elevation. Like to reserve that honor for mountain peaks, etc.

 

Thanks,

kg.

[peter]

If you have a model with a barometric altimeter, it is basing its elevation on the plane's cabin pressure. As you go higher and higher, the air gets thinner and thinner. The barometer senses the difference in the air pressure and that's how it knows what altitude you're at. Commercial airliner cabins are pressurized to around 5,000 feet so that passengers can all breathe in comfort without the aid of oxygen masks. The barometric altimeter is giving your altitude based on the plane's cabin pressure. Even though the plane is really at 41,000 feet, the GPSr thinks it's only at 5,000 feet. This is one of the reasons why I like the models that DON'T have sensors.

 

Yes, that's certainly a possibility that I hadn't considered in my response above. But most units with the barometric altimeter do at least allow you to see the current GPS-based altitude in some way - either on the satellite page or by doing an altimeter recalibration (although it won't stay recalibrated). Unfortunately many don't have any way to incorporate just the GPS readings in the tracklog.

 

[And you've been lucky if your flights have kept the equivalent cabin altitude at only 5000'. The rules allow them to operate at a cabin pressure equivalent to 8000' and most of the flights I've been on have kept it up to at least 6500'. A higher eq. altitude benefits the airline in two ways - it's slightly more fuel efficient and it leads to sleepier and less demanding passengers.]

[+JDandDD]

 

So concerns about interference with aircraft systems seem to have been answered to the satisfaction of the airlines. I'd think the same is likely true of Bluetooth. Given the large numbers of laptops, PDAs, etc. that now include Bluetooth and with a mix of users who may not even be aware of when those ports are activated, the airlines had better be sure that those emissions won't interfere.

Good point. Forgot about that angle with the notebooks. I hope that the airlines have looked at that and they likely have. Surprising then that they would be so concerned about non-transmitting GPSrs.

Of course this all applies to use while at cruising altitude (> 10 kft) where the airplane crew has more time to respond in the very unlikely event that there is some type of interference. Restricting use of passenger electronics during the more critical landing and take-off phases seems like a reasonable precaution even if the risk is low.

Quite right, and unfortunately I've seen passengers ignore that. My basic advice to people on the issue is to check your airline's regulations and also ask on board be fore use.

 

JDandDD

[+joe gremlin]

Actually it's likely to be giving you more accurate elevation information than you're getting any other way. When flying above the 'transition altitude' (18000' in the US), airplane pilots all set their pressure-based altimeters to an assumed standard sea-level pressure of 29.92"Hg

I don't really understand how the pilot setting the altimeter to 29.92 would make your gps altitude more accurate. Assuming you're seeing GPS derived altitude, it would be as accurate as it always is which is to say, not very accurate. I would imagine WAAS improves things quite a bit (since that was one of the design intentions) but straight GPS based altitude simply isn't very accurate nor was it ever intended to be.

[+Big Sky Explorers]

I usually fly Northwest Airlines and as long I am sitting next to a window I can get my Magellan Platinum to lock up on a fix. I have a had a " Flight Attndant" ask me if it was a GPS. I told yes and then she asked if it had an antenna. I told her NO since there is no visable antenna and she went on her way. The last flight I was on, I has a guy in the military ask if my GPS was working since he saw it in my window. I then told him where we were, altitude and speed. He then said he wished his would work in the plane. I am not sure what model or make he was trying to use, but mine was working.

 

Sometimes it takes a LONG time for it to "sync" up and indicate the satellites it is tracking, but it works.....

 

PS. I have the barometer in mine and I get all kinds of weird readings in a plane, but the elevation is correct since it is derived from the satellite info.

Edited February 22, 2006 by Big Sky Explorers

[peter]

Actually it's likely to be giving you more accurate elevation information than you're getting any other way. When flying above the 'transition altitude' (18000' in the US), airplane pilots all set their pressure-based altimeters to an assumed standard sea-level pressure of 29.92"Hg

I don't really understand how the pilot setting the altimeter to 29.92 would make your gps altitude more accurate. Assuming you're seeing GPS derived altitude, it would be as accurate as it always is which is to say, not very accurate. I would imagine WAAS improves things quite a bit (since that was one of the design intentions) but straight GPS based altitude simply isn't very accurate nor was it ever intended to be.

 

Using the standard setting of 29.92"Hg will of course have no effect on the accuracy of a passenger's GPS. But it makes the pilot's altimeter give an inaccurate altitude reading unless the atmosphere happens to correspond closely to the standard model With reasonable satellite reception the GPS reading should be within about 50' (I've actually been getting about 95% of readings within 40' of surveyed even without WAAS). But the pilot's altimeter could well be off by quite a few hundred feet, although as stated before it'll be consistent with other planes and therefore still safe.

 

Therefore if the pilot makes an announcement that we're cruising at 34000' and my GPS reads only 33,400' I'll be inclined to believe that the GPS reading is the one that's closer to reality

[+Team Cotati]

Yes, it is absolutely possible. And yes, it is also in violation of FAA Regs. to operate the unit during departure and landing, so don't do it. I have used my GPSr quite often when flying commercially and it provided me with much entertainment and makes the time just FLY by. ;-) A nice thing about the Gold is that it will even maintain a lock when resting on the folddown seatback tray so long as I place it very near the edge nearest to the window and rest it so that the antenna it pointing toward the window. A great conversation starter and really interesting if you bring along a road map of the USA or wherever you happen to be flying over. Your seat mates will no doubt have many questions as you navigate along your flight path. Great fun....try it, you'll like it.

Edited February 22, 2006 by Team Cotati

[+Team Cotati]

"A higher eq. altitude benefits the airline in two ways - it's slightly more fuel efficient and it leads to sleepier and less demanding passengers.]" I'd sure like to know exactly how you came by that little tidbit of information?

[+joe gremlin]

Yes, it is absolutely possible. And yes, it is also in violation of FAA Regs. to operate the unit during departure and landing, so don't do it.

Has this changed? It's been a while since I've had to read any regs. The last time I checked though, the use of GPS or any other electronic device on board an airplane was strictly at the discretion of the PIC (pilot in command). I don't remember any wording in the FARs singling out takeoff/landing (but like I said, it's been a while). Of course each airline writes their own ops manual and most include provisions for things like GPS use by pax. So far as I remember though, the FAA doesn't give a rats anus about it or any other electronic device so long as it doesn't interfere with the safe operation of the flight as determined by the PIC.

[peter]

Yes, it is absolutely possible. And yes, it is also in violation of FAA Regs. to operate the unit during departure and landing, so don't do it.

Has this changed? It's been a while since I've had to read any regs. The last time I checked though, the use of GPS or any other electronic device on board an airplane was strictly at the discretion of the PIC (pilot in command). I don't remember any wording in the FARs singling out takeoff/landing (but like I said, it's been a while). Of course each airline writes their own ops manual and most include provisions for things like GPS use by pax. So far as I remember though, the FAA doesn't give a rats anus about it or any other electronic device so long as it doesn't interfere with the safe operation of the flight as determined by the PIC.

 

The actual FAR (91.21) leaves the decision up to the aircraft operator, which is the airline in the case of a commercial carrier. However, the FAA's Advisory Circular 91.21-1 includes the following as item 6 under *recommended* minimum procedures:

"Prohibiting the operation of any portable

electronic devices during the takeoff and landing phases of

flight. It must be recognized that the potential for personal

injury to passengers is a paramount consideration as well as the

possibility of missing important safety announcements during

these important phases of flight. This is in addition to

lessening the possible interference that may arise during sterile

cockpit operations (below 10,000 feet)."

 

So technically it doesn't appear to be an absolute requirement, but airlines generally jump into line pretty quick when the FAA issues a "recommendation."

[+Team Cotati]

No, it hasn't changed, it is still a violation. Don't do it unless you are flying on Mythical Airlines, they do, at last check allow any type of electronic device to be used without restriction during any flight phase either in the air or on the ground.

Edited February 23, 2006 by Team Cotati

[+GeoForse]

Not to take this post in a completely different direction, but I have used mine on a plane (near the window) but it never seems to give accurate elevation information? Is there a reason for this? Anyone else have the same experience?

 

Thanks,

kgag.

 

I have used my gps many times in commercial aircraft. The airline's flight magazine will generally tell you what devices are permitted. I'd say about half the airlines allow gps use above 10,000 feet. Because satellite reception IS an issue in any airplane, even next to the window, often times, my gps would only lock onto three signals, thus giving only 2D information with no accurate elevation information. It is also my impression that with WAAS reception, elevation information is better than barametric altimeter. Additionally, WAAS information idoes not rely on setting the air pressure necessary on a barametric altimeter.

 

GeoForse