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I've been told anecdotes like this several times on the interviews. Interviewers used this story as an argument in favor of defensive software development.

Here is an explanation from one of the numerous occurrences on the web:

This story was told by people from Motorola and is supposedly included in every microcontroller training course Motorola gives.

Test flights of F-16's were being conducted in Israel. The F-16's were doing low height rounds. On approach to the Dead Sea, the whole navigation system suddenly reset itself. The daring pilot landed the bird. HQ called up Motorola and ordered a team on the spot ASAP. The ground tests went perfectly, but every time the bird went airborn, it rebooted.

The pilots were getting restless. Flying on the border of hostile territory without navcom, with the Arabs pointing their earth-to-air missiles at anything that moves, wasn't that pleasant. Neither was debugging the whole navcom in-flight. Then someone figured it out.

The height of the Dead Sea relative to world sea level is -400 meters. As soon as the F-16 reached sea level, the navcom did a divide by zero, crashed, and rebooted.

When I tried to search for information on this topic I couldn't find out any references to mentioned Motorola training courses. I also failed to find any references to real-life events (dates, places, crash reports).

My question is: Were there any documented cases of aircraft navigation system crashes due to zero/negative height level?

Additional question that emerges from the quote above: Are there any Motorola microcontroller training courses that mention "Dead Sea case" as an example?

Related discussion on snopes forums

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Why would you need to divide anything by current altitude? I cannot think of any measure that would require that. –  vartec Aug 12 '13 at 11:52
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BTW. Another variant of the story is that the F-16s autopilot turned plane upside-down as soon as it crossed the equator. –  vartec Aug 12 '13 at 12:05
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@vartec, maybe a bug in the SubmarineMode() method :) –  Benjol Aug 12 '13 at 12:11
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if aircraft electronics could not deal with below sealevel altitudes, there'd be hundreds of aircraft crashes in the Netherlands every single day. Schiphol, Amsterdam International, is situated at -12 feet. Rotterdam International I think is at -7 but I don't remember exactly. Lelystad is at -10 or so (but has no scheduled flights, only executive and private aircraft), etc. etc. –  jwenting Aug 12 '13 at 12:23
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There are so manny things wrong with this that its hard to know where to start. The main indication of urban legend is the rather vague terms in which the story is told. "The whole navigation system reset" is the sort of thing you say in a made-up story, but if you really know what you are talking about then you are much more precise. Aircraft nav system record several different kinds of altitude, and almost all of them can go negative at some point - frequently enough for it to be tested. –  DJClayworth Aug 12 '13 at 13:59

1 Answer 1

I found two similar cases.

The USS Yorktown (CG-48) suffered a divide-by-zero error that brought down its entire network and caused its propulsion to fail. (ref, ref)

A group of 8 F-22 fighters had their systems fail when they crossed the international date line. (ref, ref)

I could find no evidence that a 0 foot altitude has caused a system failure at the dead sea or anywhere else.

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yeah, I actually found the link to USS Yorktown article. Thanks for the reference on F-22 squadron –  default locale Aug 12 '13 at 17:24
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Adding a minor data-point: I found a Snopes forum poster claiming the story was propagated in a non-fiction book by Tom Clancy. I searched the obvious candidate: "Fighter Wing: A Guided Tour of an Airforce Combat Wing", but it didn't appear in there. –  Oddthinking Aug 13 '13 at 1:14

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