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Bear with me for a moment; I know that this is based on a movie scene, but there's a real question at the end.

Early in the 1995 movie The Net, there's a scene where a programmer is flying their Cessna at or near dawn, approaching the destination airport. This is a night flight, so it would presumably be an IFR flight with all of what that means, or rather meant in the mid-90s. We get to hear some communication between the pilot and ATC:

(pilot) Burbank tower, Cessna seven-three-nine-Mike-Bravo, intercepting approach course, ILS runway eight.

(ATC) 39 Mike Bravo, we've lost radar contact. Say your position and altitude.

(pilot) Just passing the middle marker at 1300 feet.

(ATC) 39 Mike Bravo, that's a negative. Verify your position and check your instruments.

(pilot) All normal, for crying out loud, you must be able to see my lights.

(ATC) That's a negative. Execute a missed approach immediately. Contact approach control on one-two-four point five.

A moment later,

the airplane crashes into what appears like it could be power station chimneys, and turns into a fireball, killing the pilot.

That ATC exchange has always bothered me. I can see a few things that feel obviously wrong:

  • It seems awfully late, especially in IFR towards a big airport (assuming that's Hollywood-Burbank, which goes nicely with a later in-movie statement that this happened "outside L.A."), to contact ATC only by the time you are well into the final approach.
  • If this is an IFR flight, shouldn't the pilot be following a filed flightplan, and wouldn't someone notice if the aircraft strays too far from its intended course and at least ask the pilot what's going on then rather than wait until it is well into populated or industrial areas? (Note: I can't tell from the movie if the plane supposedly has a transponder or not.)
  • By the time of passing the middle marker, shouldn't the pilot have the runway clearly in sight and at the very least be lining up with it, if not already be fully lined up with it? This is in moderate darkness, but it doesn't appear to be in otherwise difficult conditions; no visible fog, for instance, even in aircraft-exterior shots.

If someone wants to comment on the above as well, feel free to. However, my main question is this: if this situation were to somehow develop in real life, then is the phraseology realistic? Would ATC say that they have "lost" radar contact? Since the aircraft is obviously in the wrong place by that time, it would seem like they should never have had radar contact in the first place. In such a situation, I (as a non-pilot) would expect ATC to request an ident, possibly verifying the transponder code as well.

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  • $\begingroup$ I hope I tagged this correctly. $\endgroup$ – a CVn Aug 29 '17 at 20:53
  • $\begingroup$ "that's a negative. Verify your position and check your instruments" - yet they lost radar contact, so how do they know it's incorrect? $\endgroup$ – Steve Kuo Aug 29 '17 at 21:31
  • $\begingroup$ @SteveKuo Extra-sensory perception? Or knowing which direction to look in and not seeing any aircraft navigation lights? (That latter is how I've explained that particular comment to myself...) After all, the pilot is giving a supposed heading to the aircraft (the inverse of ~80° along the runway) and supposed distance ("middle marker"), so someone who knows where those are should know where to look given that. If there's nothing there, then, well... $\endgroup$ – a CVn Aug 29 '17 at 21:35
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"Radar contact lost" is standard phraseology. Most typically it's used when an aircraft far from the radar antenna is no longer being picked up, and it's just an advisory that "we can talk to you but we can't still see you." (Remote VHF antennas are cheaper & easier to put up in remote places than radar transmitters.)

As for the scenario itself, initial contact with the tower is hardly the point where ATC would first notice that the aircraft wasn't going where it should be. To get TO the ILS course, you'd typically have Approach Control issuing radar vectors to the aircraft, ending up with "N1234X, 3 miles from Van Nuys, fly heading 100 until established, cleared ILS runway 8 at Burbank." If the aircraft flies through the course (for whatever reason; it sounds like in the movie the implication is that his navigation equipment has been hacked), they'd issue another vector, cancel his approach clearance & tell him to climb, or whatever.

Also, ATC (i.e. Approach Control, even more so than Tower) will get automated low altitude alerts when an aircraft is below set altitudes. If an aircraft in radar contact was descending into terrain (and not on final to a runway), well before the radar loses line-of-sight with the aircraft, the controller would issue something along the lines of "N1234X, low altitude alert, check altimeter 30.05, climb and maintain 2000'."

There are non-radar environments where pilot mistakes have put perfectly flyable aircraft into the terrain without any opportunity for ATC intervention. There have been cases within radar coverage where misread instruments, usually only when combined with an additional pilot error, have put aircraft into terrain or obstacles short of the landing runway. The smokestacks referenced sounds like a prominent feature well north of Burbank, so at a minimum there's some "artistic license" involved in claiming that a hacked ILS could put the aircraft that far off course in that direction without ATC catching it well in advance of things getting to the point of a crash.

Also, an ILS receiver would be awfully hard to hack, no matter what sort of evil programming genius you are. You could disable it in several different ways (pair of wire cutters would do that), but the malfunction would be obvious to the pilot early on. To have the receiver seem perfectly normal but in fact guiding the pilot down too soon would really require broadcasting false signals to the aircraft in real time in a way that an ILS ground station probably can't do -- at least not without triggering a warning in the monitoring equipment that ends up shutting it down. And even then, when the pilot gets to 200' above the runway elevation, if HE doesn't see the runway lights, he should be going around.

All in all, this scenario has its weaknesses. The idea that a hacker could create enough problems to bring down a plane is actually more credible now than in 1995, but even so, the most likely problems are a lot less dramatic than what's described -- "hey, where'd all my electronic charts go?" Aviation has a LOT of safeguards to prevent exactly this sort of scenario from playing out, even with state-sponsored bad guys as the potential threat.

But, it made for a fun movie, so suspension of disbelief and all, right?

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  • $\begingroup$ My favorite movie ILS hack was in Die Hard 2, where the terrorists, with a few clicks on the keyboard, made the glide slope antenna sink 50 feet into the ground! $\endgroup$ – TomMcW Aug 29 '17 at 21:27
  • $\begingroup$ @TomMcW With no degredation of signal quality for approaching aircraft, I'm sure? $\endgroup$ – a CVn Aug 29 '17 at 21:28
  • $\begingroup$ @MichaelKjörling I believe you could mess with the glide slope and get it to fly you too low, but it's not something you could do remotely. You'd have to have physical access to the equipment. Since it works on amplitude one could boost the 90Hz signal and the instrument would continually think you were too high. Getting the pilot not to notice the discrepancy would be the next trick $\endgroup$ – TomMcW Aug 29 '17 at 21:37
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    $\begingroup$ @TomMcW Actually on KAL 801 in Guam, the GS was out of service, and they descended all the way down to Localizer mins right after passing the marker, instead of stopping at the step-down fix that would have kept them clear of Nimitz Hill. That was one of the cases I had in mind with the "an additional pilot error" comment. They knew they were descending dive-and-drive to LOC mins, but they missed the stepdown on the chart. $\endgroup$ – Ralph J Aug 29 '17 at 21:59
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    $\begingroup$ There is one very close call caused by a faulty GS. An ANZ 767 got down to 400ft AGL before they noticed a problem and went around. They apparently were prompted by seeing city lights. Had there been a thick fog it's possible they could have flown right into the ground $\endgroup$ – TomMcW Aug 30 '17 at 16:29

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