# Why don't all commercial aircraft transmit GPS data in real time?

It seems strange that trucks and taxis can be set up to transmit GPS data in real time but aircraft cannot. Wouldn't this be a useful function and feasible to implement?

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Isn't this pretty much what ADS-B is? –  Fred Larson Mar 12 at 16:00
Wouldn't it be easier to just have an iridium satellite phone on each airplane that could fire up a distress call in case of an emergency? I'm am not an aviation expert, but that seems like a easy solution. –  Marcello Mar 12 at 23:15
This is obviously related to the recent downing of MH370. The limitation with something that will transmit data in real time is that it won't work if the antennae are destroyed. Most of the time it will work fine, but the times when you need it are the times it would be at most risk from destruction. –  Hugh Mar 13 at 2:37
@Marcello Some aircraft do have satellite phones. However, the last thing a pilot is going to do in an emergency is fiddle with a bulky inconvenient phone. –  Greg Hewgill Mar 13 at 3:39
@james - how do you disconnect all the wiring taking power and data to the black box when you eject it? You can either have very flimsy connectors which might be broken in the very event you are trying to record. Or you could have explosive blades to sever all the cables - but this might not be a major contribution to safety –  NobodySpecial Mar 29 at 3:21

Most commercial aircraft transmit their (GPS based) position real time, it's called ADS-B. The problem is not on the transmission site, but on the receiver side. The signal travels line of sight so beyond the horizon you won't receive it. Over large bodies of water there is no coverage.

It would require a network of many buoys to cover all seas, this is far too expensive.

Another possibility is to put ADS-B receivers on satellites. This concept is being developed by Thales Alenia Space and Iridium (Aireon) at the moment. The first satellites will launch next year, the system is expected to be operational in 2018.

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For one example of how ADS-B is being used, check out this FAA video -- they've made this work in the Gulf of Mexico because there are oil rigs to host receivers. Making it work over large bodies of water (like the oceans) is obviously more difficult as DeltaLima mentioned. –  voretaq7 Mar 12 at 19:06
I don't think that the first sentence is really accurate. There are a lot of commercial aircraft that don't have ADS-B.... The FAA isn't even requiring it on aircraft until 2020, and there are lots of areas where there is no ADS-B coverage. –  Lnafziger Mar 12 at 19:11
@Lnafziger the first sentence is accurate, most (>50%) commercial aircraft have ADS-B (at least in my part of the world). It might not have been certified to the latest standards, but they transmit position. –  DeltaLima Mar 12 at 22:42
@DeltaLima Maybe "in your part of the world", but that is only a portion of the commercial aircraft. Also, if it is close to 50%, then "more than/around half" would be more accurate even if "most" is technically correct. :-) –  Lnafziger Mar 12 at 22:46
So according to FlightRadar24, 60% of passenger aircraft are equipped with ADS-B (70% in Europe and 30% in the US). I'm not sure that I would call those "official" numbers but I think that it gives us a good idea. (And we are both right, lol.) –  Lnafziger Mar 13 at 4:43

The main problem with this is that it is somewhat easy to know where the device is, it's a lot harder for the device to tell someone else where it is. Satellites are really the only option for this sort of thing, and a lot of the polar routes have pretty poor satellite coverage anyways. Also, satellite bandwidth is quite expensive.

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Iridium has coverage even in polar region. –  osgx Mar 12 at 17:48

there is already something like that, the primary and secondary radars allows for positional data to be received by the controller, so adding this is superfluous from FAA's standpoint. To do this voluntarily is expensive.

To roll out a transmission of gps position data you need someone to be listening to it. Cars use the existing mobile network. Planes would likely use the transponder frequencies.

You also still need to be compatible to existing transponders while the global rollout happens.

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What if they are out of radar range? –  JoelFan Mar 12 at 15:33
@JoelFan then you won't be able to receive gps data either unless you use satellites but that isn't cheep either –  ratchet freak Mar 12 at 15:35

No, it wouldn't be useful. And no, it would be exceedingly hard to implement, not to mention exceedingly expensive.
Cars and trucks are rarely out of range of cellphone towers, which is the system they use to transmit that data to their company headquarters. Mind that that's only used for some trucking and taxi companies, and a few car rental and lease companies, not generally (though there are some governments that are pushing for it, which has very strong privacy considerations as essentially your location would be known to the government within a short radius at any time, Big Brother is watching you...).
It's used mainly for fleet management purposes, like a rental agency can use it to pinpoint you to being where that speeding ticket was written so they can tell police who to send the fine to (and the points on your license).

The equipment for cars and trucks is also small, weighing in at maybe a pound (including mounting brackets, cables, etc.) and drawing little power.
For aircraft, it would need to be larger as instead of a small cellphone transceiver it would need a satellite radio link and antenna. It would also as a result draw a lot more power, which means higher fuel use on top of the extra fuel use from the higher weight of the aircraft (ignoring the possible extra drag from the antenna which makes it even worse).
And it's not real time, obviously, the cost would get to be far too high. Most cars and trucks would send an update only once every few minutes at most (selectable).

And aircraft already have something like it anyway, with systems that can send location and status data to the airline. But it's triggered manually, usually, and not in universal use.

Such a system would have virtually no purpose, and a high cost of operating it. You'd need not just a small box in every aircraft, you'd need a network of communications satellites, ground stations around the world with 24/7 staff on hand, etc. etc.
And I seriously doubt you're going to want to add a few hundred dollars to the price of every ticket just in the off chance that when your flight goes down someone can find the wreck a bit sooner.

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you could use an existing satellite-phone network for the data, –  ratchet freak Mar 12 at 15:55
I kinda have to disagree with "no, it wouldn't be useful" -- It's VERY useful when you can make it work... –  voretaq7 Mar 12 at 19:03
So let me see if I understand your answer correctly: You say that it isn't useful, it would be too expensive, has no purpose, and yet aircraft already have it?? I think I'm missing something.... –  Lnafziger Mar 12 at 19:21
A few hundred dollars on the price of every ticket? You're suggesting that no GPS tracking system could be built for a cost of less than tens of thousands of dollars per flight? –  David Richerby Mar 12 at 22:55
"your location would be known to the government within a short radius at any time" that's right, as if we were all carrying a cellular phone. hey wait.. –  magma Mar 13 at 15:07

From a documentary on the 2009 Air France crash: I remember an aviation expert answering the same question. He said that it is expensive (About extra $300 million for a typical national carrier per year) and Airliners are reluctant to take on any additional expenses even if such an undertaking improves safety (The Air France jet crashed because the Pitot tubes froze thus disengaging the auto pilot. The Airline was aware that the Pitot tubes needed to be replaced way before the accident but did nothing because it was expensive). - Actually I don't think it's terribly difficult to implement technically. Of course getting regulators and airlines on board - and dealing with security and privacy issues are other matters entirely. As others have pointed out there are existing satellite data networks (e.g. Iridium and Inmarsat) that can be used to transmit location information "back to base". The field terminal equipment for these networks isn't particularly power hungry either. Infact a company I did a bit of work with in the past (on another project) sells a system exactly like that right now, which is designed for helicopters and small aircraft. They're not a big company, so I'd lay odds that they have competitors in this field too. https://www.indigosat.com has details of their particular system. - For commercial aircraft, I don't see any privacy issues. – David Richerby Mar 13 at 15:28 I haven't read through all of these responses, but most focus on locating the plane going down in the middle of the ocean, as well as major new equipment and transmitters. First, the location wouldn't have to be a separate GPS transmitter. It only needs to be voice or text transmitting the location data which the plane already has. Whatever the communication of the location data, it doesn't have to be relayed at the point of impact or damage. Obviously, that would be most helpful, but in the case of MH370 - and especially if it was flying in a straight line, then having 2 points would be helpful. That is, if the plane is detected over Malaysia, then over the Indian Ocean, they would have a path and relative search area based on fuel, etc. It's not perfect, but simply a transponder that can't be turned off would probably have been sufficient enough to detect the general area of the aircraft in the first week. There needs to be satellite tracking in real-time, but I think there are sufficient systems in place already that would have made this much easier. As an example, and in response to the earlier post about \$300M system, if a person sat on a plane and texted lat/long every 15 seconds, they would find this plane much quicker even if it went beyond text towers. I'm not suggesting having a person do that, but you can create a device that does that for a relatively small amount of \\$. It's not the perfect system, but is better than nothing.

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This is a good answer, but it doesn't actually address the question of why this doesn't already exist. –  Danny Beckett Mar 26 at 14:30
As far as why pilots can turn off the transponder, see this question. As far as texting your position, cell service doesn't work at altitude or over the ocean/other places where there are no cell towers. It's the communication of the data, everywhere in the world, that is the main issue here. If an airplane crashes in the middle of the US or Europe, you won't need anything on the airplane to find it.... –  Lnafziger Mar 26 at 15:39