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What would happen if all of the the navigation systems (such as GPS & INS) in a commercial aircraft completely failed?

Could the aircraft land safely without all the navigation aids?

Notts90
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L.Halfpenny
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    Aircraft have multiple navigation systems available, based on different technologies, power sources etc. It might be good if you can give a more specific scenario. – Pondlife Jan 23 '17 at 17:12
  • I wasn't sure if you're asking a technical question or as a concerned airline passenger. Either way, you could look out the window and look around. – user6035379 Jan 23 '17 at 18:28
  • There are multiple navigation systems on a commercial aircraft the full scenario is covered here What will happen if satellite navigation fails? – Dave Jan 23 '17 at 18:41
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    The plane might land safely in a totally different airport than expected. Turkish Airlines Flight 1123, Aug 14th 2008 – Jordy Jan 23 '17 at 19:08
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    Hi. Welcome to Aviation.SE. Sorry for the downvotes, personally, I can't see why. As to the close votes, I don't agree and think it's a perfectly reasonable question from someone (and I do make an assumption here) who does not necessarily understand modern aircraft systems. – Simon Jan 23 '17 at 20:02
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    @Simon: The problem I see is the lack of definition of "navigation system", e.g. does that include the failure of the compass? So not off-topic, but unclear for the moment. – mins Jan 23 '17 at 20:04
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    If we want this site to be accessible to non-experts, we cannot expect people to come in and detail every individual navigation component - surely just saying "the navigation system" is enough to understand what he is asking... regardless though I feel this is enough of a duplicate to the linked question to be closed. – Ben Jan 23 '17 at 22:11
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    @mins If we edit the title to say all electric navigation systems would that help? – Notts90 Jan 24 '17 at 08:59
  • @Notts90: What is the OP after? They want to know if an airliner is able to land safely at an appropriate airport if automated navigation fails, perhaps including approach systems (VOR, ILS), and indeed it could, with vectors and PAR from ATC, even without knowing where the north is. But the radio needs to work. If not it could be helped be a side military aircraft and visual gestures. So I don't really know which case is to be explained, and whether this is at night or at day. Do you? – mins Jan 24 '17 at 10:07
  • @mins I think it's basically what you just said, if all electric navigation aids failed (therefore also any automation would not work) would the plane land safely? As you say, the answer is probably. The idea of a military aircraft assisting is good too. – Notts90 Jan 24 '17 at 10:15
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    There was a film about a similar scenario in a private aircraft over the ocean. They came up with some interesting (though soundly biased) ideas for working out current location. http://m.imdb.com/title/tt0107556/plotsummary?ref_=m_tt_ov_pl – Notts90 Jan 24 '17 at 10:17
  • @Notts90: Perhaps. I'd wait a few hours to give the possibility for the OP to edit the question, and after would assume something and put it in the post. Just, it must be very clear, so that answers are using the same scenario. Or maybe it could be answered by describing solutions from the most basic (follow me aircraft) to ones that need some means aboard the plane. – mins Jan 24 '17 at 10:20
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    I'm nominating this question for reopening. As of its current state, it is clear, on topic, and totally reasonable for everybody outside the aviation community to ask. – kevin Feb 13 '17 at 15:23
  • I would assume that commercial airlines would be able to get directions from Air Traffic Control. – user6035379 Feb 13 '17 at 17:25
  • Option 1: Use VFR to fly after contacting ATC, Option 2: Mayday - – Old_Fossil Aug 18 '18 at 22:01

2 Answers2

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The possible answers to your question are for all practical purposes infinite depending on the details of the system failure, the weather, where you are, and crew experience, to name a few. However, as a thought exercise extremely unlikely to ever happen in reality, let's play with it a bit.

First, let's define the navigational systems failure to be such that we cannot determine our position by reference to instruments in the cockpit. What have we got left? If we can still communicate, others can work with us to determine our position and develop a course of action.

The simplest case would be if we were talking to ATC, were in an area of secondary radar coverage, and our transponder was still working. If that were the case, it would be a matter of getting radar vectors to wherever we wanted to go. If I were the captain, I would want to go to the nearest suitable airport since if I had had a failure of everything that could tell me in-cockpit where I was, I would be worried about possible further failures.

If talking to ATC and in an area of primary radar coverage only or you also had transponder failure, they could give us a series of turns to identify us (used to do that back in the 1960s occasionally).

If you were out of range of VHF communications with ATC, you could try getting a relay via another aircraft that was in VHF range of ATC. Two aircraft at altitude can talk to each other at far greater distances than an aircraft to a ground station. A simple call to any listening station or aircraft on 121.5 requesting assistance will almost always get a response.

If VHF communication is not possible, you could try getting a patch through to ATC on HF radio. My favorite back in the 1990s was Stockholm radio. These days, however, SATCOM is available. I don't know anything about it, but I imagine it provides the ability of an aircraft anyplace in the world to be patched through to an appropriate ATC facility.

So, if you're talking to ATC (by whatever means) but you're out of radar coverage, what then? Every captain would remember generally where he was prior to the failure. It could be as simple as someplace in the North Atlantic and eastbound. He could simply tell ATC that and that he will fly a westerly heading. ATC would clear the altitude he was at and look for him along the westerly limits of their radar coverage for when he inevitably would show up. Actually if it was the North Atlantic and it was nighttime, he could just follow any airplane in front of him. They're easy to see stacked out into the distance.

The general idea would be to get to where you could be seen by ATC, and go from there. Anymore, there aren't a lot of areas along regularly traveled airline routes over land in North America and Europe where above 30,000 ft an airline flight won't be seen. That was true back in the 1990s, more true now I am sure, and increasingly true through the world, especially if military radar can be utilized..

The more interesting problem becomes that there is a loss of communication as well as a loss of navigational ability. The possibilities here are limitless. A simplification would be to say that what you would do would be to take up a heading that you believe will get you to where you could visibly see a land mass with airports, and land at the first suitable airport you see. Most airline flights are along routes that the crew is very familiar with; they know what they've been flying over many times, and that would be a help.

Terry
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  • SATCOM is available almost everywhere -- the geostationary Inmarsat birds can't be reached from the geographic poles. (You should still be able to raise someone on HF from there, though.) – UnrecognizedFallingObject Feb 14 '17 at 00:19
  • A couple other things...first, you probably ought to mention that "nearest suitable" would involve either VMC or the availability of a GCA (ASR or PAR) approach (since without working nav systems, you wouldn't be able to shoot a normal instrument approach). Second, there is an off chance that someone'd be sent to intercept you under those conditions (which is a good thing, because you can simply then form up on the interceptor's wing and let them lead you to a safe place to land). – UnrecognizedFallingObject Feb 14 '17 at 00:25
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There are several different navigation systems in commercial airliners that can operate independently of each other such as:

and more besides.

The chances of all these systems failing simultaneously are so slim it's not normally considered. However the assuming other instruments are functional there are still methods of navigation available.

To start with, you would probably want to talk to air traffic control and advise them of your situation. If there is radar coverage for your location (probable if over land) they can track your position and keep you updated as required.

Secondly, you would know your position at some point prior to the system failure, your airspeed and direction. So you could use this information to work out your approximate position.

Finally if you're over land you could use good old fashioned navigation using landmarks to work out where you are and which way to go.

Notts90
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