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Pilots today have more than enough technology both in the cockpit and in the infrastructure that supports them to know with great precision where they are at any given time. How/why do they still sometimes go off-course?

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    $\begingroup$ Haven't seen all the details from this one, but last time we've seen two conflicting accounts of what happened. Did they cross the border? Did they not? How far? How long? Unless you were actually on site with the right equipment to precisely determine the position of the aircraft at all times, it's just wild speculation on who is right. $\endgroup$ – jcaron Jan 30 '16 at 23:57
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    $\begingroup$ They enter in others space because they want to. They know they are in. $\endgroup$ – Trebia Project. Jan 31 '16 at 0:25
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    $\begingroup$ @mins It is not a political game. I can accept that the vast majority, if not all, of modern airspace violations are intentional, but voting to close without the slightest attempt to explain technically how unintentional violations could happen or why they should not happen is a total non-answer. My question is not meant as flamebait. $\endgroup$ – Pedro Jan 31 '16 at 3:00
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    $\begingroup$ @mins Would it have made any difference if I phrased my question as, "How would it be possible for aircraft to unintentionally enter another country's airspace?" Because that is essentially what I am asking. $\endgroup$ – Pedro Jan 31 '16 at 3:17
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    $\begingroup$ Are you also interested in the vertical navigation error (altitude error)? $\endgroup$ – mins Jan 31 '16 at 22:28
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1) Technology is fallible.

2) Humans are fallible.

Now that aircraft have GPS receivers it is rare for them to be off course by a considerable margin. That said, technology can fail and there are cases where the GPS cannot, or should not, be used.

The crew can also make mistakes, either by incorrectly reading the navigation data or by incorrectly entering flight path details into the navigation system: An aircraft may actually be 'on course' based on what the crew told it to do, but they told it the wrong thing. Depending on how data is entered into the system it's easy to add the wrong waypoint (some have very similar names, there's been a few cases of that happening) or to enter reciprocal bearings or lat/lon points. On top of that there's simple crew distraction - if they're manually flying then they may be focussing on something else and not notice that are off-course: As happened on the Sukhoi superjet demonstration flight a few years ago.

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  • $\begingroup$ @ Simon: in your great answer you mention crew distraction as a possible cause of getting off-course. Not sure if it's always to be called distraction. After all the golden rule is first flying the aircraft, which can be quite a job sometimes. Then comes navigating it. (And then communicating.) $\endgroup$ – Rob Vermeulen Feb 8 '16 at 9:22
  • $\begingroup$ @RobVermeulen: Yes, that's a good point. To be honest 'distraction' was simply the best word I could think of to describe this. Flying might be most important, but it is still a distraction from the navigation task :) $\endgroup$ – os1 Feb 8 '16 at 10:35
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    $\begingroup$ And to add to #2... people will sometimes hand fly the aircraft and just flat out forget to look at the map: sometimes if they think they know where they are but are in fact in a very similar looking area. I've done this when driving before I realised there are two very similar looking churches next to two very similar looking garages... $\endgroup$ – Jon Story Feb 8 '16 at 10:50
  • $\begingroup$ Thanks for the answer. I would be interested in knowing in what kind of situations GPS is not recommended. $\endgroup$ – Pedro Feb 8 '16 at 16:00
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    $\begingroup$ @Pedro - ask another question! Sounds like a valid one to me. $\endgroup$ – FreeMan Feb 8 '16 at 17:15
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The navigation data (angles, coordinates) are initially numbers and must be read by human first to use the navigation systems. If the pilot misreads or wrongly interprets the initial data, the navigation tools cannot help.

This seems the reason of both Varig Flight 254 and TWA Flight 3 navigation mistakes. In general cases seem rare as they require the navigators to stay disoriented for a long time, regardless of that they see, radio stations they hear, etc, etc.

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My Dad was a fighter pilot in the Korean War. He acidentally did something in the cockpit which effected his air mix. Without sufficient oxygen, my Dad got lightheaded and started flying towards North Korea. My Dad might well have died or become a POW except that members of his fighter group flew back to find him. My Dad was sufficiently cognitively aware to recognize his comrades and use them as his "navigators" back to home base.

Things that can effect a pilot's cognitive state can still happen. Look at naval and air force fighter crashes over the past handful of years. As a chemist, I'd identify one likely culprit as new cockpit materials insufficiently tested for offgassing (changed chemical state) at critical state points. I have one material, in particular, in mind.

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    $\begingroup$ Out of curiosity, which material and why? $\endgroup$ – Pedro Oct 11 '18 at 16:43
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A basic expansion of os1’s answer.

1) broken or defective equipment.

2) equipment that is not properly maintained or calibrated.

3) improper use of equipment by flight crew.

4) incorrectly interpretation of output data from equipment by flight crew.

5) terrestrial or satellite navaids needed to operate equipment either down for maintenance or unavailable.

6) incorrect procedures used by flight crew.

7) Overconfidence in onboard systems causing negligence of basic airmanship and good risk management.

8) Confusion among duties for pilots in aircraft requiring more than one flight crewmember.

9) saturation by existing cockpit tasks causing negligence in navigation.

10) human frailty, fatigue and external pressures.

It can happen to anybody, in any kind of airplane, no matter how advanced the equipment on board is. I wrote in a post about Instrument flying that modern integrated flightdecks i.e. glass cockpit have the capability to make a good pilot better and a poor pilot dangerous. This still rings true today. Smart people routinely do stupid things in aircraft and it can have tragic consequences. This can be insidious if one is not careful.

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