X RX is the first ever portable, passive, stand-alone collision avoidance system for general aviation to offer direction from within the cockpit. Threat aircraft direction can be detected from within your cockpit in a tiny, self-contained unit. XRX offers multiple aircraft information, audio alerts and advisories, an easy-to-use menu interface, and local information. XRX displays “3-D View” quadrant bearing information, as well as relative altitude and range, all from inside the cockpit and without the need for external antenna arrays.
Proven, time-tested technology in the palm of your hand. See what you've been missing with PCAS XRX.
Purchase Online | $1795
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PCAS MRX, the smallest, lowest cost collision avoidance system ever created, all with proven digital technology and accuracy. MRX delivers accurate range and relative altitude in a package the size of a deck of cards. It's even portable and works for up to 8 hrs on 2 AA (NiMH) batteries.
Purchase Online | $499
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How PCAS Works
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Technology
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Written by Jason Clemens
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Monday, 18 December 2006
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The first in a series of in-depth articles taking a look at the technology behind PCAS and today's advanced collision avoidance systems. This article is a brief overview off the technology behind traffic detection.
PCAS, which stands for Portable Collision Avoidance System, is a trademark of Zaon Flight Systems for technology similar in function to TCAS (Traffic and Collision Avoidance System). TCAS is the industry standard for commercial collision avoidance systems. The original PCAS technology was developed in 1999. Now, the MRX/XRX line of collision avoidance systems incorporates the fourth generation of PCAS technology. Through this technology, transponder-equipped aircraft are detected and ranged, and the altitude is decoded. PCAS G4 technology has advanced to the point that highly accurate range, relative altitude, and quadrant direction can be accurately detected in a portable, all-in-one cockpit device.
To explain how the system works, consider the following:
Step One
To start the cycle, an interrogation is sent out from ground-based RADAR stations and/or TCAS or other actively interrogating systems in your area. This signal is sent on 1030 MHz. For TCAS, this interrogation range can have a radius of 40 miles from the interrogation source. The Ground RADAR range can be 200 miles or more
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Step Two
The transponder on any aircraft within range of the interrogation replies on 1090 MHz with their squawk code (known as Mode A) and altitude code (or Mode C). The altitude information is sent in an encoded format.
Mode S transponders also reply on this frequency, and encoded within the Mode S transmission is the Mode A (squawk) and Mode C (altitude) information.
Military aircraft also respond on this frequency but use a different transmission protocol (see Step 3).
Your aircraft’s transponder should also reply. However, the XRX unit watches for this signal and will not report it as a threat aircraft. The unit may use this information to establish base altitude for use in step 4.
Step Three
Any aircraft reply within the XRX detection window (maximum 6 miles) will be received. The range is computed, the altitude code is decoded, and the signal angle-of-arrival is determined. XRX will recognize interrogations from TCAS, Skywatch, and any other “active” system, military protocols, and Mode S transmissions.
Step Four
The altitude of the aircraft (in the example, 2500 ft.) is compared to your local altitude (i.e., 1500 ft.) and the relative altitude is calculated (i.e., 1000 ft. above you). With relative direction, altitude and range determined, XRX displays this information and stores it in memory.
Step Five
If additional aircraft are within detection range, the above process is repeated for each aircraft. The top threat is displayed on the left of the traffic screen, and on Screen A, the second and third threats are displayed on the right.
The greatest threat is determined by looking at aircraft within the detection window you set up and comparing primarily the vertical separation (+/- relative altitude), and secondarily the range to the aircraft currently being displayed. XRX uses patent-pending SmartLogic algorithms to determine which of two or more aircraft is a greater threat. See flight scenarios later in this chapter for more information.
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Technology
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Written by Jason Clemens
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Wednesday, 20 December 2006
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The second in a series of in-depth articles taking a look at the technology behind PCAS and today's advanced collision avoidance systems. This article demonstrates the amount of collision avoidance "coverage" in the U.S.
The Domino Effect
One of the most common questions I get asked when demonstrating PCAS is, "What about coverage?" It's a good question. First, it's important to note that PCAS (and every other collision avoidance system) receives transponder replies. Transponders in your area are interrogated by an active source, such as ground RADAR or TCAS-equipped airliners. Once interrogated, transponders emit the Mode A (squawk) and Mode C (altitude) codes that PCAS receives. (See "How Does PCAS Work?" for more on this). Think of it as a Domino Effect that starts with an active interrogation.
But what is the source of the interrogation?
PCAS has the unique ability to work in two interrogation envrionments. Ground RADAR, referred to as SSR or Secondary Surveillance RADAR) is perhaps the most obvious source and is prevalent throughout the US. The map below shows RADAR sites around the US. These include enroute, military, and terminal RADARs.
Ground RADAR Sites (ARSR-3, ARSR-4, ASR-9, and ASR-D)
Military RADAR
Dedicated military RADAR sites have an approx. average interrogation range of 200 NM (diameter). The following illustration shows the approximate coverage.
Military RADAR Coverage: 200 NM approx. avg. range
Terminal RADAR
Terminal RADAR sites typically exist around major airports and can extend to approx. 120 NM (diameter). The next illustration shows this interrogation source combined with military RADAR.
Terminal RADAR Coverage: 120 NM approx. avg. range (+ Military RADAR)
Enroute RADAR
The third class of RADAR interrogation source is enroute RADAR, which has a much greater range than terminal, approx. 400 NM (diameter). If we add this source to our map, we get the following:
Terminal RADAR Coverage: 120 NM approx. avg. range (+ Enroute and Military RADAR)
TCAS Interrogations
In addition to ground-based SSR interrogations, TCAS (Traffic and Collision Avoidance Systems), found in corporate aircraft and every airliner, also presents a viable interrogation envorinment. TCAS interrogation range varies from 40 NM to a maximum of 100 NM (radius). TCAS interrogations are often more informative than ground-based interrogations for a variety of reasons. For example, in mountainous areas, an airborne interrogation platform is not limited by mountains, unlike Ground RADAR, which is line-of-site. This means that an aircraft in a valley and in the shadow of ATC will still be interrogated by any airliner within 40 to 100 miles, and PCAS should be able to receive the reply.
When we overlay the average number of TCAS-equipped airliners and their approximate interrogation ranges on our map, the total interrogation coverage area looks like this:
Average Interrogation "Coverage" Area: Military, Terminal, Enroute RADAR and TCAS Interrogation
Conclusion
As you can see, it is very difficult to find an area where interrogations are not occuring. However, please note the following:
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The map does not include other active systems, such as Skywatch® or other GA-market systems
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Coverage may vary or be more limited than illustrated in more mountainous areas
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It is still possible for PCAS, or any other passive system, to miss aircraft due to any one of many reasons
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Ranges illustrated are approximate or averaged. TCAS ranges are computed from a snapshot of an average weekday system workload.
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