Gps Handheld On A Delta Flight

[+clubbuild]

the coolest thing i have done so far with my gps is flown round trip on delta to florida with the gps on. seeing all the cities your flying over while checking out the speed over the ground is great. i also marked waypoints and printed out a track on my computer. i asked the captain of the flight when i saw him in starbucks if i could use it and he said sure. really cool. i had one problem, the altitude was wrong but i guess that was due to cabin pressure.

[+ctgreybeard]

the coolest thing i have done so far with my gps is flown round trip on delta to florida with the gps on.

I did the same going out to CA and back from New York last month. We passed right over my brother's house in Steamboat Springs, CO. I downloaded the track and even though I turned it on and off a few times the track was pretty accurate as far as I could tell.

 

In another thread, though, I understand that some airlines forbid them. Even though they are not transmitters, there are rumors that they will somehow interfere with the regular avaiation instruments. I have some small amount of training in radio interference and I find that highly unlikely ... but be prepared to put it away immediately if requested by a crew member, their word is law, no matter how illogical.

 

And if you set the altimeter to use the GPS altitude (notoriously inaccurate) you should get closer to your actual altitude. The cabin pressurization messes up the barometric altimeter completely. It expects to be in the unpressurized Great Outdoors!

 

FWIW,

 

Bill

[+Chomper]

I recently Flew Alaska Airlines and they do not allow GPS (they even mentioned it over the speaker otherwise I would have turned it on). I have used it on other airlines however and it is very cool.

[+RickNY]

Take a look here for a fairly accurate list of which airlines permit or forbid GPS:

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

[+Team Cotati]

When the flight crew announces that you can now turn on portable electronic devices, turn on your GPSr. If later a member of the flight crew asks you to turn it off, turn it off.

[iNiq]

What I do is just hide it whenever a stewardess walks by. My 60CS antennae needed to be in the window to work. So for the first half of the flight, they never saw it. And the second half I stopped hiding it. I don’t think they cared at that point.

 

Since a gps is a receiver only. There is no way it could interfere with the plane, period. Logic dictates that. IMO, it’s a simplistic rule to prevent the flight crew from having to make judgment calls. Like, “Is it a gps?” “Does it have transmitting capability?” etc…

 

Anyway, I got caught with it on once, just b4 we pushed off from the terminal. All she did was give me a dirty look and told me to turn it off…. I turned it back on just b4 we got to the runway.. Hehehe I forget which airline I was on.

 

Haven’t taken my 60CSx up yet. I’m looking forward to it.

Edited July 6, 2006 by iNiq

[+JDandDD]

Cabin pressures are set to maintain the equivalent of about 8000ft. So that's as high as you'll get if you are doing this via pressure. Altitude taken from satellites is very likely going to be well off since all you are getting is the slice of sky through your window so the satellite geometry is almost sure to be poor for altitude.

 

I never turn mine on during takeoff or landing. Although the risk is really low the result of messing with the instruments just isn't worth it. The result can be a crash of course, but the pilots can also have you arrested for failing to follow safety directions. Turn it on when electronic equipment is allowed and off when it isn't.

 

JD

Edited July 6, 2006 by JDandDD

[+Puddlewalkers]

If I sit next to a window my 60csx works. I bought a serial cable that I hook up to my PC. I run MS Streets and Trips and track the flight realtime using the NMEA interface - works great! The altitude reported by the NMEA interface is the GPS elevation, not the barometric altimeter, so it is accurate.

 

Garmin needs to offer the option to report the GPS elevation on the altimeter page, not sure why it isn't an option. It can be accessed on the satellite page by pressing Menu.

 

Going close to 500 mph does pose some problems for MS Streets and Trips, you can only zoom in so far, but the granularity is more than acceptable for seeing what your flying above.

[iNiq]

I never turn mine on during takeoff or landing. Although the risk is really low the result of messing with the instruments just isn't worth it. The result can be a crash of course, but the pilots can also have you arrested for failing to follow safety directions. Turn it on when electronic equipment is allowed and off when it isn't.

 

JD

 

I’m serious. The question if gps receivers influence airline flight controls, fits in the same category as..... “Does the refrigerator light stay on when the door shuts?” No, of course not. And neither does the gps affects the planes nav instruments.

 

No disrespect JD. We’ll have to agree to disagree on this one…

[+Team Cotati]

Cabin pressures are set to maintain the equivalent of about 8000ft. So that's as high as you'll get if you are doing this via pressure. Altitude taken from satellites is very likely going to be well off since all you are getting is the slice of sky through your window so the satellite geometry is almost sure to be poor for altitude.

 

I never turn mine on during takeoff or landing. Although the risk is really low the result of messing with the instruments just isn't worth it. The result can be a crash of course, but the pilots can also have you arrested for failing to follow safety directions. Turn it on when electronic equipment is allowed and off when it isn't.

 

JD

 

What type of "satellite geometry" do you need for good altitude information?

[+GPSlug]

What type of "satellite geometry" do you need for good altitude information?

For the purposes of a passenger on an airplane? How accurate do you need in that case, a few hundred feet?

 

A VDOP of less than 25 or so. As long as the visible satellites have any elevation separation at all, it should be fine.

[iNiq]

I never turn mine on during takeoff or landing. Although the risk is really low the result of messing with the instruments just isn't worth it. The result can be a crash of course, but the pilots can also have you arrested for failing to follow safety directions. Turn it on when electronic equipment is allowed and off when it isn't.

 

JD

 

I’m serious. The question if gps receivers influence airline flight controls, fits in the same category as..... “Does the refrigerator light stay on when the door shuts?” No, of course not. And neither does the gps affects the planes nav instruments.

 

No disrespect JD. We’ll have to agree to disagree on this one…

[peter]

I never turn mine on during takeoff or landing. Although the risk is really low the result of messing with the instruments just isn't worth it. The result can be a crash of course, but the pilots can also have you arrested for failing to follow safety directions. Turn it on when electronic equipment is allowed and off when it isn't.

The question if gps receivers influence airline flight controls, fits in the same category as..... “Does the refrigerator light stay on when the door shuts?” No, of course not. And neither does the gps affects the planes nav instruments.

Your answers to both questions are correct *if* everything is working the way it should be. But if the switch on the refrigerator door is broken then the light may not turn off when it shuts. And if some of the plane's instrumentation is particularly susceptible to interference and/or there's something defective in your GPS/laptop/palm/etc. resulting in increased emissions then there could be a problem. During the cruise portion of the flight the crew would have time to deal with any erratic indications from the instruments, but during takeoff and landing the results could be more serious which is why use of passenger electronics is restricted at those times.

 

Yes, such a situation is very unlikely and, AFAIK, there has never been a documented case of a passenger GPS receiver causing interference on a commercial airliner. But there have been a few such incidents with other electronic devices and the rule against use of electronics when below 10 kft seems like a reasonable safety precaution without being unduly restrictive.

[+JDandDD]

I never turn mine on during takeoff or landing. Although the risk is really low the result of messing with the instruments just isn't worth it. The result can be a crash of course, but the pilots can also have you arrested for failing to follow safety directions. Turn it on when electronic equipment is allowed and off when it isn't.

 

JD

 

I’m serious. The question if gps receivers influence airline flight controls, fits in the same category as..... “Does the refrigerator light stay on when the door shuts?” No, of course not. And neither does the gps affects the planes nav instruments.

 

No disrespect JD. We’ll have to agree to disagree on this one…

I think peter put it very well but I think I'll expand a bit.

 

No I don't personally believe that GPSr's would have a major effect. But, this is one of those low probablility and high impact situations. If in the extremely unlikely event that the equipment was malfuncitoning and radiating emi or another extremely unlikely event that some frayed exposed wire wasa picking it up from your location the high impact is a potential crash. If that seems as unlikely as that remember TWA 800, frayed wire, allowed a high voltage line to short out and pass the high voltage through a low voltage line to the centre fuel tank that then exploded. The fuel in the tank also had to be heated to vapor first though since JetA is not volatile in a liquid form (you can actually throw a match into it and the match will go out, unlike gasoline that will light). So now second low probablity event. The fuel was vaporized because the flight was delayed 30 minutes because they thought they had baggage on board but not the passenger and thus a security issue. Acutally there was a mistake and the passenger was there. However, on a hot day, the air conditioning systems were running, are situated under the tank passed their residual heat to the fuel tank vaporizing the fuel.

 

That was a series very low probability high impact events. Unfortunately, low probability events do occur in the real world. That is the daily business of the NTSB. So, all I was saying is that the potentially high impact isn't worth a few minutes of GPS tracking and isn't worth me risking other people, regardless of how minimal the probability.

 

JD

Edited July 7, 2006 by JDandDD

[+Team Cotati]

What type of "satellite geometry" do you need for good altitude information?

For the purposes of a passenger on an airplane? How accurate do you need in that case, a few hundred feet?

 

A VDOP of less than 25 or so. As long as the visible satellites have any elevation separation at all, it should be fine.

 

That's interesting. I had always understood that you only needed 4 sats to get altitude calculations. If you have 6 sats, is the altitude reading more accurate?

[The Bouncers]

the coolest thing i have done so far with my gps is flown round trip on delta to florida with the gps on. seeing all the cities your flying over while checking out the speed over the ground is great. i also marked waypoints and printed out a track on my computer. i asked the captain of the flight when i saw him in starbucks if i could use it and he said sure. really cool. i had one problem, the altitude was wrong but i guess that was due to cabin pressure.

I did the same thing on a United flight across the country. I had to hold my GPS right next to the window, though, to get satellite coverage. VERY COOL to see on the map what we were flying over. Not sure you can get away with it nowadays, though. I did it several years ago.

[+Team Cotati]

the coolest thing i have done so far with my gps is flown round trip on delta to florida with the gps on. seeing all the cities your flying over while checking out the speed over the ground is great. i also marked waypoints and printed out a track on my computer. i asked the captain of the flight when i saw him in starbucks if i could use it and he said sure. really cool. i had one problem, the altitude was wrong but i guess that was due to cabin pressure.

I did the same thing on a United flight across the country. I had to hold my GPS right next to the window, though, to get satellite coverage. VERY COOL to see on the map what we were flying over. Not sure you can get away with it nowadays, though. I did it several years ago.

 

Let's not, OK?

[+GPSlug]

What type of "satellite geometry" do you need for good altitude information?

For the purposes of a passenger on an airplane? How accurate do you need in that case, a few hundred feet?

 

A VDOP of less than 25 or so. As long as the visible satellites have any elevation separation at all, it should be fine.

 

That's interesting. I had always understood that you only needed 4 sats to get altitude calculations. If you have 6 sats, is the altitude reading more accurate?

Altitude isn't really much different from latitude and longitude to a GPS receiver. It's just calculating a 3d position and rotating to that coordinate frame.* So, more satellites are better for altitude, just like any other direction.

 

*The minor differences are (1) there's a huge, pesky, L-Band-opaque mass (the Earth) blocking your signals in half of the up/down direction, so you don't get as good of a DOP (thus accuracy) in that direction, and (2) if you make an assumption that you have no vertical velocity component (on level ground), you can constrain the height in the equations to your last known height and get a 2d solution with only 3 satellites. Unfortunately, if you are in fact moving up and down, big errors will creep into your 2d solution. It could constrain, say, latitude in the same way if it had some reason to believe you weren't moving north/south at all, it's just a lot more likely you aren't moving up/down very much (at least in Kansas).

[+phreakmonkey]

 

I’m serious. The question if gps receivers influence airline flight controls, fits in the same category as..... “Does the refrigerator light stay on when the door shuts?” No, of course not. And neither does the gps affects the planes nav instruments.

 

No disrespect JD. We’ll have to agree to disagree on this one…

 

I just want to add some information - years ago I held the exact same opinion as iNiq of various radio receivers until a couple of things happened.

 

First:

 

I got my amateur radio license and started building and tinkering with radio circuits. What I learned in this process is that most all digital receiver tuners work by running an oscillator at an offset of the intended frequency to be received and then tuning a circuit to the offset by means of a crystal. Well, oscillators are transmitters too, and since the whole setup is wired to an antenna some receivers can output a fairly strong carrier wave signal on the offset frequency from the one you're receiving.

 

An interesting (and unfortunate) example of this: Lots of digital PLL tuners use a +10 MHz offset frequency. So if you're tuned to 99.7 MHz with a digital FM tuner, the PLL circuit is sending out a "ghost" signal at 109.7 MHz. (You can often find the offset frequency with a handheld scanner, and then deduce what frequency the other receiver is tuned to.) What makes this example so unfortunate is that the aircraft navigation band is 108.0 MHz - 117.987 MHz. Simple FM walkmen can interefere pretty severely with VOR receivers in aircraft cockpits.

 

Sure, one stray signal in the back of a jet airliner might or might not cause noticable interference, but if you allow them and, say, 25 or 30 passengers turn these devices on then it can really wreak havock on the instruments.

 

Second:

 

I became a private pilot and eventually bought a Cessna 172. The darndest thing happened - sometimes my handheld Magellan 315 GPS didn't work worth a darn in the cockpit, no matter where I placed it. I fussed and fussed with this problem until one day during a flight I noticed that my second VOR Navigation receiver on my Narco MK-12D radio was acting weird too. I turned the Magellan off, and the VOR reaquired the signal from the ground station I was navigating towards. On the return flight, I turned off the Narco and the GPS signal came back. The two were interfering with each other - and only when the Narco was set to a particular VOR frequency. Another case of I.F./Offset frequency tuners causing malfunctions - and in this case the malfunction was actually between a handheld GPS receiver and a piece of aircraft navigation equipment. I was quite surprised, even though I knew it was possible.

 

So yes, it can happen. More easily than you think. In fact, now that I've isolated the exact frequencies it occurs with I've demonstrated it in my cockpit for a number of people as an eye-opener.

 

Pretty interesting stuff.

 

Cheers!

-pm

[+GPSlug]

Similar interference the US Coast Guard had to deal with. GPS being jammed 2000 feet away by a Radio Shack TV antenna. They tracked it down to a batch of bad amplifiers from one manufacturer which had very unpredictable interference. In one harbor had a heck of a time finding the source of the interference because it was only in the GPS band when the boat with the antenna had both its TV and lights on (or some combination like that, don't remember exactly). Anything else and the interference went away, it was that flaky.

 

A similar antenna at someone's house was affecting test results where I work from over 2 miles away. Not enough to block us completely, but enough to see in some high-precision tests. We had to loan the CRTC (like a Canadian FCC) an antenna to track it down, because at the time they didn't have anything for > 1GHz.

 

So a poorly designed or manufactured receiver can do a lot of transmitting when it malfunctions.

 

That being said, it's extremely unlikely a low power handheld GPSr is going to do anything, but turning it off for takeoff and landing is easy to do.

[+doveroftke]

As I understand it, all electronic devices create a bit of low-powered radio interference that affects a very small area; I don't think a GPSr is any more dangerous than a CD player. In the event that the interference reaches the VOR antenna (which is extrmemly unlikely in a large commercial jet) AND happens to be affecting the particular frequency the pilot is using, it's not going to cause the plane to fall out of the sky. The instuments will read as if the plane was right over the VOR transmitter, which the pilot will know is clearly not the case. Even if the incorrect reading leads the pilot to turn towards the VOR location, the reading would remain consistent no matter how much manuvering is done, clearly indicating a bad reading. Besides, aren't airlines mostly using GPS for navigation now?

[+Lighteye]

Cabin pressures are set to maintain the equivalent of about 8000ft. So that's as high as you'll get if you are doing this via pressure. Altitude taken from satellites is very likely going to be well off since all you are getting is the slice of sky through your window so the satellite geometry is almost sure to be poor for altitude.

 

I never turn mine on during takeoff or landing. Although the risk is really low the result of messing with the instruments just isn't worth it. The result can be a crash of course, but the pilots can also have you arrested for failing to follow safety directions. Turn it on when electronic equipment is allowed and off when it isn't.

 

JD

 

I recently had mine on and hooked up to my laptop while flying roundtrip from Florida/ Chicago/Florida, and yes it was a fun way to pass the time. My shown speed was within 12MPH, and altitude within 100' of what the pilot gave out over the intercom. That's with the 60CSX in the window. Beautiful.