How can figher planes fly under the radar???

Question

random question!! but i dont understand the whole idea of radar tracking planes but how can a plane 'fly under the radar' without getting caught?? is it flicking off some switch r summit?

Answer 1

Wow.   lots of 'experts' and none of them really gave the answer.

1.  radar is not pointed upward, unless they need to look upwards. its pointed parallel to the ground or 1 or 2 degrees above the horizon.

2.  radar signals bounce off things. planes, mountains, rain/ice. buildings.and waves on the ocean...lots of stuff interferes with radar signals close to the ground.  sometimes as high as 200'.  All this is called "ground clutter".

early on, pilots learned of this and new if they flew close to the tree tops or above the waves, they would be "lost in the clutter".

Modern radar has multiple components and in someways...can see over the horizon.  this is better the higher up the antenna is mounted.  for every 6feet in elevation gives 10 miles of added range. so if you are 150 feet above the water (like an AC carrier)  you can see 250 miles....well beyond the normal horizon for a 6' man with binoculars.

wer

so.

Answer 2

Sticking strictly to the topic of "flying under the radar," here is how it works:  a radar antenna is pointed upward at a shallow angle.  Because of this, the radar signal travels  upward as it travels outward from the antenna.  For a target to be depicted, the radar signal must strike the target and be reflected back to the radar site.  At a distance of 50 miles from the antenna, anything below perhaps 2000 feet might be below the radar "beam," but five miles from the antenna, coverage will extend virtually to the ground.   The greater the distance from the antenna, the higher the floor of radar coverage becomes.

If you are trying to evade radar then, the object would be to remain below the lowest altitude a particular radar is capable of displaying.  The problem is that generally there will be multiple radars covering a given area, and determining what area has coverage, and what area doesn't have coverage is problematic.  Another kicker for trying to "fly below the radar" is that there may be airborne sensors (another word in this context for radars) that are capable of looking down at the ground and painting a target virtually at ground or sea level.

Answer 3

A radar transmitter is usually put up high on a pole so it can scan the horizon above any tall hills or buildings.  They're usually about 50 ft up.  A plane than can fly less than 50 feet from the ground would not be detected.  That is what's called flying under the radar.  

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Answer 4

I don't know where drwer2 got his figures, but they are funny. 6 feet for another 10 miles in range?

The stuff about ground clutter is accurate. That's what made the FB111 so great, TF RADAR, flying at 250 AGL.

Stay low, the slower the better to follow terrain. Even so, non-stealth aircraft are metal and give a better signature than a pile of dirt or bunch of trees and are moving, so they will eventually be detected by a RADAR looking for them.

Answer 5

Nap of the earth, the earths curvature. Radar can only get so low.

Answer 6

Hi! First of all, fighter planes don't actually (most times, anyways) fly "under" the radar. Radar is typically pointed/sending/receiving it's signal in an upward pointed position. So, hence the term flying"under the radar". It flies lower than the typical radar is monitoring. On the newer more sophisticated planes, (stealth) it's more complex. If you'll watch some of the educational programs, sometimes they'll have a feature about exactly how they function. But, for the biggest part, the Stealth fighter is built in such a manner and with non-reflective materials so that radar just simply doesn't detect it with conventional radar. Try and catch a program about it sometime. But, I hope I've clarified it just a bit for you.

Answer 7

it gets hit  by the radar but it reflects the beam  some where else

Answer 8

i was a search radar operator  navy that can happen fly low altitude about 20 miles away from the radar... the world is round and the beam follows a line of sight  now if you are 20 miles away  you will go under the radar beam.. because the world is round.. just fly 20 foot high above ground or sea level. ok

Answer 9

Here's the whole story. Aside from the first guy, who is describing stealth or "low observability:, everyone here had described a different aspect of using low altitude to avoid radar. A transmitter's elevation, it's angle compared to the ground, terrain and clutter, and the curvature of the earth all play a role in avoiding radar.  "Flying under" usually refers to staying below the beam of the radar. As above answers indicate, how low you have to fly is determined by the angle of the radar and how high it is placed. Putting a radar on a tower, however, allows the operator ro "look" down over terrain and the Earth's curvature, so choosing the best flight path can be tricky. Flying behind mountains and low enough for trees, boulders, dust, etc. block the radar signal is a related, but separate technique called "terrain masking". It's important to note that the mst effective radar arrays are attached to aircraft called AWACS or Airborne Warnng And Control Systems. These planes have the ultimate high ground, allowing them, to see even low flyers. Those and newer, more sophisticated systems like fast scanning phased array radars are making it harder and harder to hide down low.