This has to rank among the most idiotic ideas I've ever heard: The German government wants to prevent terrorists from flying planes into nuclear power plants by jamming aircraft GPS navigation systems in the vicinity of nuclear power plants.
"The radio transmitters would jam satellite navigational equipment aboard incoming aircraft, effectively making nuclear facilities 'invisible' to pilots who were not within visual distance."
It is estimated (not by the German government) that in order for this technique to be effective, which is to say to jam GPS navigation beyond visual range of a power station from an aircraft at 10,000 feet or so, the system would have to jam GPS to a radius of approximately 100km (about 60 miles) from each nuclear power plant. It is also estimated that this would effectively jam GPS pretty much throughout Germany. (That does, I suppose, at least mean that the hypothetical terrorist would be unable to locate the stations simply by finding the edge of the jamming zone and turning to fly directly into it... because the zones would overlap so much there'd hardly be any edges to find.) It would do nothing to prevent the hypothetical terrorist from flying a dead-reckoning course to within visual range and eyeballing it in from there, navigating his way to the nuclear plant using a map, navigating via ADF or VOR, or simply scouting out the area in advance on the ground and picking out landmarks to guide the pilot to the target. As if this isn't already stupid enough, the German government also plans to hide the plants from visual attack by generating large clouds of smoke or fog to mask them in case of an attack. ("How do we find the target?" "Just look for the smoke cloud.") As has been pointed out elsewhere, even if it worked at all, this would have to be activated in advance of an attack, so would be no protection against a surprise attack.
This is apparently a response to several recent incidents involving distraught individuals doing stupid and suicidal things with light aircraft (one committed suicide by attempting to crash a light plane into the Bundestag parliament building, for example, but missed). The German government has apparently overlooked the fact that general-aviation aircraft of this class are so light and of such flimsy construction that they would present no realistic threat in such an attack anyway; a Cessna 172 weighs less than a Honda Civic, and would just crumple up like tinfoil if flown into a reactor containment building. There is serious grounds for doubt about whether even a fully-laden commercial airliner would actually present a serious threat to the integrity of the containment building. We're not talking about a mostly-glass office building here, we're talking about a thick reinforced-concrete blockhouse designed to contain a catastrophic failure of a nuclear reactor. Pretty much the worst that could be accomplished with a light general-aviation aircraft is to temporarily take the plant off the grid by crashing the plane into the distribution farm.
This is a stupid, inane, ill-thought-out, Hollywood-movie-plot response to a threat that is barely even credible in the first place.
(Crossposted by request to snobss)