In the last few years there have been multiple planes that have just dropped of the radar and vanished. Some more famous like the Malaysian airlines plane and some local incidents. Aren’t we already at a technologically advanced enough level where it should be virtually impossible for planes with no cloaking tech to vanish off of radar?
In: Technology
Radar needs a direct line of sight to something to be able to see it. This limits ground based radar to a range of about 60 miles. Major international airports will have radar that can see that far, but smaller airports – particularly those outside of the US – don’t.
Radar coverage throughout the world is pretty minimal. Civilian radars typically only cover a small area around airports while military radars only really cover the area around airbases as well as some potential conflict zones. Chances are that you’re outside of radar coverage if you aren’t flying over a major city.
However, commercial airliners are all equipped with a radio transponder that is just constantly broadcasting the plane’s current GPS coordinates and height. This allows airports to see where planes are far beyond the range of their actual radar.
When a plane suffers some sort of catastrophic problem – such as blowing up in mid air, that transponder gets destroyed and stops broadcasting. This is what the media will typically refer to as the plane “vanishing from radar.” In other words, the plane wasn’t actually being tracked by an active radar system, but it was showing up on an airport’s radar system because that system is capable of detecting the plane’s transponder signal out to a very long range and displaying the embedded positional information on the airport’s radar screen.
In the case of Malaysia Airlines flight 370, the theory is that the pilot turned the transponder off. If the transponder is off, then the plane will only show up on radar screens when it comes within that 60 mile range of an actual radar system that puts it close enough to be detected.
because radar will only see signals sent in a specific angle depending on the elevation and power of the dish.
Under a specific height the ground or sea will reflect the radar showing as a solid block of matter, as well as natural radiation reflection and heat reflection from the soil and water, This is also why Satellite communications companies rarely guarantee service in any elevation under 15 degrees (near the poles).
so usually radar is blind to objects which are too close to the ground,
You can usually compensate by using less powerful radar or smaller dishes, but it makes them useless for higher altitudes and longer ranges.
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