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Stereo Radar Ears
Excerpt from Winging It! With Dr. Paul: Forty Tales Your Flight Instructor Never Told You (copyright © 1989 by H. Paul Shuch)

"If God had intended man to fly, he would have given us. . . transponders!"

That thought typifies the FAA approach to air traffic separation, a system designed around ground based radar and ground-bound controllers, dependent upon a steady stream of verbiage along a tenuous radio link. Those of us who fly the system with any degree of regularity recognize that it works, most of the time. But we are also acutely aware of its limitations. We know how vulnerable our current air traffic control system is to equipment failure. We contemplate the fine line which separates jargon from gibberish. We endure frequency saturation which all too often makes it impossible to get an edge in word-wise. And above all, we come down to the inescapable fact that the ultimate responsibility for collision avoidance rests squarely upon the shoulders of the pilot in command. The pilot is, after all, the first person to arrive at the scene of the accident.

What must ultimately emerge from the alphabet soup of technological alternatives is a collision alert system designed specifically for general aviation use, intended to supplement existing air traffic control procedures. I see it as not so much revolutionary as evolutionary, in that we are continuing an established trend of returning the responsibility for a pilot's actions to the cockpit, where it belongs.

"Another new collision avoidance system?" I hear you asking. "What can a new one possibly do that can't be done with ACAS, BCAS, TCAS or XYZCAS? Why do we need another system anyway? And what's all this going to cost?" Fair questions. I'll try to answer them all.

What's wrong with XYZCAS? Nothing, as long as everybody does his job perfectly, and the equipment never malfunctions. The problem with the plethora of collision avoidance systems previously proposed or currently under consideration is that they are all cooperative in nature. That is, they all depend for their operation on some sort of equipment installed aboard the other aircraft, or on the ground.

The objection to such systems is obvious, and tends to be more philosophical than technological. It has to do with self-determination, and the fierce independence which flying seems to foster. Why should I rely, the thought process goes, upon ATC's radar, or your transponder, tail strobe, or laser beacon to do its job correctly, or for that matter, even to be turned on? If I wish to control my own destiny, I should rely only upon that equipment within my personal control. That means placing the collision alert radar not on the ground, but aboard my plane, where I can assume full responsibility for its operation. That also means I need to detect your aircraft not just from transponder returns, but from direct reflection of radiant electromagnetic energy off your plane's wood or metal, fabric, foam or fiberglass. Take no offense, but I trust my own reflective airborne radar more than I do your transponder!

Current technology provides us with a wide variety of effective methods for determining those variables pertinent to the collision avoidance equation: target distance, bearing, direction of flight and relative velocity. Existing systems provide this information to the pilot visually, utilizing a variety of display technologies. The primary objection to all visual display systems is that they keep the eyes of the crew in the cockpit instead of encouraging a constant and thorough visual traffic scan.

An alternative to visual displays is an aural traffic alert. However, the usual method of a controller providing verbal information to a pilot can lead to misinterpretation. For example, how often have you responded to a call of "traffic at your 1 o'clock position, three miles" by looking at 3 o'clock and 1 mile?

In any collision avoidance system , whether based on skin reflective radar, transponders, lasers, airborne interrogators, ground-based support or satellites, the weak link has to do with clear, unambiguous communication of traffic information to the pilot in a manner compatible with both the performance of required flight duties and maintaining an effective visual traffic scan. The challenge lies not so much in the ability to sense targets, as in the area of user interface.

To understand one possible solution to the CAS problem, try standing blindfolded on a railroad track. For persons with normal binaural hearing, there is absolutely no doubt as to the direction from which the train is approaching, how far away it is, how fast it's moving, how soon it will be upon you, or even which way to run. The sound of the whistle tells it all! Similarly, binaural hearing can be used to communicate to a pilot the position, relative distance and closing velocity of potentially conflicting traffic without distracting the pilot from either normal cockpit duties or a visual traffic scan.

All we need do is provide a tone which, like the train whistle, tells it all. This is a trivial task for current radar and stereo audio technologies. The object here is to provide you, the pilot, with an aural indication of the presence of potentially conflicting air traffic. The distance to the nearby aircraft, its location with respect to the user aircraft and its speed and direction of motion relative to the user aircraft are all interpreted directly by the ear/brain combination, thanks to your natural binaural hearing.

But what price protection? Cost is the single most difficult system parameter to accurately forecast. In the late Seventies I was a member of the engineering team which broke the $4000 barrier for home satellite TV systems. My colleagues and I thought we had reached rock-bottom. Today, any number of dealers will offer you comparable systems for $700 or less. What drove the prices down? Economies of scale, mass marketing, offshore production, heavy competition and, eventually, market saturation all played a role. Unfortunately, few of these same dynamics apply in the avionics industry.

The active U. S. general aviation fleet currently sits at about 200,000 aircraft. Let's assume an appropriately priced collision alert system can achieve about ten percent market penetration, over a five year phase-in period. That suggests a market for about 20,000 units, or 4,000 per year. Not a very large base for volume production. Higher than expected public demand can raise these figures two- or even three-fold, but we're still talking a minuscule potential volume. Especially when contrasted with the home satellite TV market of 1 million units annually throughout the early Eighties. On the face of it, one concludes that no avionics product can ever achieve even marginal economies of scale.

On the other hand, one need only look at the diverse and competitive nature of the LORAN-C market to realize that there are dollars waiting to be spent on avionics which fill a perceived need. Collision alert may well fall in this category, especially if the insurance industry offers incentives in the form of premium reductions for equipped aircraft. When Texas Instruments announced their $7000 aircraft LORAN-C unit just a few years ago, I doubt whether anyone anticipated the order-of-magnitude price reduction which would follow. Or the bells and whistles which would be added to subsequent products.

Then there's the favorite economist's controversy: does volume drive price, or vice versa? That's like debating whether power or pitch controls airspeed. The LORAN-C experience does give us some insight into possible pricing of an independent CAS system, in that the electronic and mechanical complexity of the two systems is roughly equivalent. Should similar market conditions exist, it is not unreasonable to expect pricing to follow suit. Thus one can expect that general aviation collision alert systems could range in uninstalled price from about $1000 for a bare-bones unit, up to perhaps three times that amount for one with all the bells and whistles. What those bells and whistles might be, I cannot begin to imagine!

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