On August 31, 1986, a Piper Archer flying at 6,500 feet in clear skies collided with a DC-9 that had been cleared for an ILS approach into Los Angeles International Airport.
All 64 people aboard the airliner, three people in the Piper and 15 people on the ground were killed. The NTSB declared the accident was because of \"the limitations of the ATC system to provide collision protection.\"
Almost immediately, Congress passed a law requiring the FAA to mandate that all airlines use a relatively new technology called Traffic Alert Collision Avoidance System, or TCAS, to prevent such an accident from happening again, and so far, it\'s been a success?there hasn\'t been a single fatality from a collision in a TCAS-equipped airplane in the United States since.
But until recently, the general aviation airplanes most of us fly didn\'t have that technology, and on almost a monthly basis, we see result: television stories about fatal collisions that could have been avoided with TCAS or TCAS-like technology.
The issue has always been cost?expensive TCAS-like systems typically cost upwards of $40,000 or $50,000, making them beyond reach of all but corporations and charter operators that have the means to keep their pilots and passengers safe.
Thankfully, all that is changing because of better technology, reduced costs, and pressure from aircraft manufacturers like Cirrus who have turned safety into a competitive advantage.
\"With Cirrus\' culture of focusing on safety first, it is only natural for us to push for the best tools to help the pilot operate their aircraft safely,\" said John Gauch, Fleet Sales Director for Cirrus Design Corporation.
To better understand the options available, let\'s break the technology down into relatively simple terms. There are five different types of collision avoidance technology, and knowing how they work will help you better understand which one you need.
The simplest system is a passive receiver. These units listen to transponder signals in the airplane\'s immediate area, and provide visual or audible signals that another airplane is close by.
One example is the Zaon Flight Systems XRX portable unit. The company claims the unit, which was released in December, can spot aircraft up to six miles away at altitudes 2,500 feet above or below your airplane.
The XRX is priced about $1,800 and is designed to sit on the airplane\'s glareshield. It comes with its own internal antenna, which can mean blind spots or spotty coverage depending on how the unit is positioned in the airplane.
Depending on the sophistication of the display device, passive systems will tell you roughly where the other airplane is, and where their position is relative to yours. Some devices may also provide trend information so you know whether the other airplane is climbing or descending.
The next step up in accuracy is the Traffic Information System, which uses the Mode-S datalink from an airplane\'s transponder to communicate with a ground-based radar network and receive traffic information on a five-mile radius, 1,200 feet above or below your airplane. Because it relies on a ground-based system, TIS is only available in congested traffic areas?which you want?but it won\'t help you outside of those areas.
The Garmin GTX 330/330D trans-ponder is an example of a Mode-S transponder that can relay traffic information to a display device like the Garmin 530 or the G1000 glass panel. In fact, most of the new G1000-equipped aircraft use TIS, meaning they rely on updates from a ground-based system to provide traffic information.
Next in our hierarchy comes the Traffic Advisory System. With this technology, your airplane actively monitors the airspace looking for nearby transponder-equipped aircraft and displays this information on a multi-function device within the airplane.
Two excellent examples of this technology are the Skywatch system from L-3, and the new TAS600 from Avidyne/Ryan. Skywatch is the system included on Cirrus airplanes, and it uses active interrogation to query the transponders of nearby aircraft and determine that airplane\'s position and movement. It can track up to 30 airplanes within in a two- six - or twelve-mile radius, 10,000 feet above or below your airplane, and provides visual and audible warnings about airplanes it considers to be on a collision course with your airplane.
\"After flying with the Skywatch system, I\'m surprised at the number of aircraft I never saw before and it makes me happy to know about the traffic before ATC gives me a call,\" Gauch said.
The TAS600 comes in three models ranging from seven to 21 miles in coverage area. What makes the Avidyne/Ryan product so compelling is that it is economically priced (under $10,000 for the low-end unit), and provides capabilities similar to systems costing $30,000 or more.
Avidyne\'s head of sales and marketing Mark Sandeen said the price break is a direct result of the merger between Ryan and Avidyne, because it allows the companies to integrate their products more closely, reducing the overall cost to the consumer.
A higher-end version of TAS is TCAS, which combines a TAS-like system with onboard computers that not only tell you where other airplanes are, they figure out whether you are likely to have a collision with that airplane and warn you ahead of time.
TCAS provides a range of up to 20 miles and is typically installed on heavier aircraft used for business and charter operators. A key feature of TCAS II is that it not only anticipates potential collisions, but will also alert the pilot what action to take to avoid an accident, such as to climb or descend.
On the horizon is yet another system called Automatic Dependent Surveillance-Broadcast, or ADS-B. ADS-B is a key component of the planned Free Flight System in which aircraft are responsible for their own separation and collision avoidance.
Instead of sending signals to ground-based radar systems where coverage is limited, ADS-B equipped airplanes send position information to a satellite network called the Global Navigation Satellite System. That network then exchanges information with other aircraft and ground-based controllers so that all participating aircraft know where everyone else is.
Because it\'s a satellite-based system, it should work much better than today\'s ground-based radar systems because it\'s coverage is universal, and not affected by mountains or distance. But unlike TAS systems which query each other, ADS-B systems rely on other ADS-B systems to self-report, which means it won\'t be terribly useful until it\'s adopted on a universal scale.
The FAA appears to be currently working toward adopting ADS-B, but that appears to be a ways off. There are two major issues?one is equipping ground-based controllers with new equipment, while the other is making sure all airplanes are equipped for ADS-B. Neither problem will get solved over night.
One neat advantage of ADS-B is its broadband capabilities, allowing airplanes to receive not only traffic information, but also weather data from ground-based reporting stations.
If all of this sounds futuristic, it\'s not. ADS-B is currently being used in Alaska to help pilots in what is largely an uncontrolled airspace avoid accidents in areas where radar coverage is limited.
All of the new glass-panel aircraft from companies like Columbia, Cirrus, Diamond, New Piper, and Cessna come with some form of TAS or TIS system, and aftermarket units designed for non-glass airplanes are becoming more and more affordable.
Happily, the day may soon come when mid-air collisions, even among general aviation airplanes, become an unheard of event.
[5 of 5 Stars!]
