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89 votes

Can someone actually "fly under the radar"?

In many cases, yes you can fly under the radar because typical civilian radar is line of sight, meaning that it has to have a straight unobstructed path to an object in order to "see" it. This is ...
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79 votes

How is radar used to help aiming a gun on fighter jets?

F-16 engineer here. This is from a great article about fire-control radar in fighter jets: For guns kills, if the aircraft has a radar lock on a target, it can accurately gauge range to the target, ...
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71 votes

Can someone actually "fly under the radar"?

It is certainly possible to fly "under the radar." Military pilots practice a type of flying called nap-of-the-earth for exactly this purpose. This tactic is primarily used by smaller fighters and ...
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68 votes
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Why do pilots have the ability to turn off the transponder in-flight?

Basically everything that consumes power on an aircraft can potentially cause interference, short-circuits, or otherwise jeopardize the safety of flight and therefore must be switchable. Sometimes the ...
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48 votes
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How is a missile lock detected?

To add some data to Matthew's answer: Anti aircraft missiles come in basically 4 types (some others have been tried but aren't in common use). Active radar homing Passive radar homing Infrared ...
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48 votes
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Why does a radar altimeter show negative values on the ground?

The zero reading is calibrated for main-wheel touchdown in a landing attitude. With the antenna forward of the main gear, it is, at that point, higher than it will be after the nosewheel is lowered to ...
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44 votes
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Would a homemade lawn chair balloon be visible on ATC and collision avoidance radar?

Would a homemade lawn chair balloon be visible on ATC and collision avoidance radar? It might be visible to ATC, but, at best, only as one of several inconspicuous unidentified red dots. It wouldn't ...
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38 votes

How did pilots avoid thunderstorms and related weather before “reliable” airborne weather radar was introduced on airliners?

They looked out the window! If you are talking about a developing thunderstorm, especially during the day, they can be quite easy to see in front of you provided decent visibility. Here is some good ...
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38 votes

What is the significance of radar cross section (RCS) for air defense?

Its all about detection distance. Take a car and a beer can. You're 10 miles away, on an open plain. From there, you can't see either. Get closer...5 miles. Still can't see either. At 3 miles, you can ...
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33 votes
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Could an aircraft 'hide' in the aircraft shadow of another aircraft without being detected or noticed?

Radar resolution is defined in terms of degrees of arc (or alternatively in steradians/solid angles) and as such, the further away from the radar, the larger volume is being sampled. At altitude and ...
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33 votes
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Can a helicopter mask itself from radar?

Note that for advanced radar systems, moving helicopters might always be distinguishable from cars and other objects, due to the fact that helicopters have moving rotors. While I have no information ...
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31 votes
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What is this radar-like thing?

It is a wind tee; it serves the same function as a wind sock. It is designed to resemble an airplane from the air so that pilots overflying the field can more easily determine in which direction they ...
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28 votes
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Why does the radar dome on the E-3 have a white stripe down the middle?

The white strip is the metallic part which houses the electronics and serves as support structure for the antenna. The black part is basically a composite (fiberglass) shell, which covers the antenna. ...
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28 votes

Why do (or did, until very recently) aircraft transponders wait to be interrogated before broadcasting beacon signals?

The Secondary Surveillance Radar system provides range in a method similar to primary radar: by measuring the time between the transmission of the interrogation signal and reception of the reply. The ...
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27 votes

Can someone actually "fly under the radar"?

Secondary Surveillance Radars work on 1030 MHz and 1090 MHz. Most primary radars work at higher frequencies. Signals at these frequencies do not follow the curvature of the earth very well. They work ...
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27 votes

How is a missile lock detected?

A general search radar, because it has to search a much larger portion of the area around the plane, can only scan so many times a second. When that radar finds a target, and the pilot commands the ...
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26 votes
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How does a PESA radar work?

Your question: What is the logic behind the delay of the signal and how is the echo signal later bound with the signal sent? Short answer A PESA is an array of individual antennas. Each antenna ...
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25 votes
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How does the weather radar work?

It works the same way any radar works. An antenna broadcasts a pulse of energy and listens for its reflection and interprets the power of the reflection to calculate the reflectivity factor Z, ...
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25 votes

Can a helicopter mask itself from radar?

The answer is yes (in most cases) but it has little to do with the helicopter itself. 5 meters (~16.5 feet) AGL is quite low to the ground. Chances are you are simply below the radar horizon for ...
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25 votes
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What is that airport equipment that looks like an SMR but rotates like a windmill?

That is a bird tracking radar antenna to detect and track birds in the vicinity of the airport. The vertical component is used to determine the bird's altitude. ROBIN's 3D Flex system consists of a ...
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24 votes

Would a homemade lawn chair balloon be visible on ATC and collision avoidance radar?

Primary radars are sensitive enough to pick up even large birds. A lawnchair ballon would certainly register if the settings allow. To suppress the signals from birds and other non-aircraft objects, a ...
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24 votes

What is this radar-like thing?

It's a lighted 'wind tee'. this website shows various wind direction indicators
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24 votes

How did the gyro gunsights of WW2 get the range and lead of a target?

You are seriously over estimating the technical capabilities of the time. The gun-sight is not much more than an intricate slide-rule. You had to feed it information about the target size/aircraft ...
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23 votes

Did WWII fighters do a roll before engaging to identify themselves to radar operators?

For a radar to be able to detect/recognize/distinguish the electromagnetic signature of a "roll" requires very sophisticated real-time Signal Processing, that was not available until digital ...
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22 votes
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Is it possible for a modern commercial airliner to stop being tracked without substantial mechanical failure?

The device you are talking about is called a transponder. This is a device that listens for a signal (an interrogation) and responds with information about the airplane including an ATC assigned code,...
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22 votes

Why do pilots have the ability to turn off the transponder in-flight?

Everything including the flight recorder has a power switch or circuit breaker. Electrical devices occasionally malfunction, and you don't want a sparky transponder setting the plane on fire when you ...
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21 votes

How does ATC radar/ADS-B ground stations not get confused with signals sent from multiple aircraft?

The class of ATC radars that you are talking about is secondary radar. Secondary radar works by transmitting an interrogation signal on 1030 MHz to which the transponder replies on 1090MHz. There ...
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21 votes
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What method does ATC use to calculate distance between two aircraft?

The things you mention would matter, if you wanted to know the distance to 6 or more significant digits. But ATC does not need that precision. They need to be able to tell whether it's 4 nmi (too ...
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21 votes

Can a helicopter mask itself from radar?

The JSTARS (Joint Surveillance Target Attack Radar System) military radar developed and used from 1991 was particularly good at identifying helicopters. JSTARS was designed to identify moving objects ...
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