by
Darryl Phillips
The November issue of AVIONICS contains an interesting editorial about new aviation products displayed at the annual convention of the World Airline Entertainment Association. That's a new one on me, after three decades of flying and many years in the avionics manufacturing business, I'd never even heard of WAEA.
It seems that inflight entertainment is big business in corporate aircraft as well as airliners. Between Inmarsat and inflight gambling (excuse me, "gaming") and airborne phones and faxes and computer linkups, there is an amazing amount of activity in this area. Everyone else in the plane has access to the electronic superhighway, it's just the pilots who are left behind.
What sort of bizarre Alice-in-Wonderland nightmare is this? What has happened to our method of thinking? Why should the flight crew be led zigging and zagging through the sky by pre-World War II methods while the passengers enjoy the latest electronic services?
I try to remember that the airplane is the reason for Air Traffic Control, not the other way around. And that government exists for our benefit, not the other way around. But sometimes I wonder.
A case in point is the Lincoln Labs plan to implement collision avoidance via Mode S transponders. Lincoln Labs receives tons of money from the FAA to develop the systems of tomorrow. They are responsible for the 1960s system called Mode S which is not yet operational. It was a good idea once upon a time, when only airliners and a few corporate aircraft carried transponders. It's a lousy idea today, but that doesn't deter Lincoln Labs. As long as FAA funds keep flowing they will continue to develop the equipment of yesterday.
They call it ADS-B. Automatic Dependent Surveillance - Broadcast. Well, I guess that makes as much sense as VOR or some of the other acronyms we've come to love. But what does it mean?
Automatic is easy to understand, no problem there. But Dependent is precisely the wrong word. INDEPENDENT is the point of the whole thing. Isn't that obvious? When viewed from the perspective of ATC, they are dependent on us, just as they are dependent today on our transponders and encoders. But viewed from the aviation perspective, gaining autonomy and independence (and thus freedom to fly in a safer and more efficient manner) is what we're working toward. So we need to get rid of Dependent.
The worst, however, is Surveillance. This is a highly pejorative term that puts pilots in the role of bad guys. A department store, for instance, uses TV cameras to make commercials and uses surveillance cameras to catch thieves. Both cameras use similar technology, the difference isn't the circuit boards. The difference is the attitude.
Look up surveillance in your dictionary. You will find examples such as "The police kept the criminal under close surveillance". Next time you hear surveillance on TV, notice the context. Surveillance doesn't just suggest distrust, it MEANS distrust.
If Black Americans don't want to be called by a certain well known derogatory term, their first step is to stop using the term themselves. And they have. The same applies to a word like surveillance. Pilots are not automatically criminals. We must avoid terms that carry a message of distrust and suspicion. Surveillance is such a word.
The fact that Air Traffic Control uses SSR and ADS is indicative of their attitude toward airplanes. That will take time to change. The necessary first step is for us to quit calling ourselves criminals. I know some will argue that this is just words, but words have meanings. Words are how we exchange ideas and concepts. Words are important.
One controversial part of the Mode S GPS collision avoidance signal is identification. Besides the trampling of civil rights and the likelihood that identification will be used to bill the cost of every ATC service to the pilot, there are technical reasons why Lincoln Labs is on the wrong track with ID. Their basic reasoning is this: If each signal has ID, then the receiving aircraft can compare successive positions to compute speed and direction of flight of nearby traffic, and the collision possibility can be evaluated. At first glance this seems reasonable. But it's not.
Here's why: Each plane already knows it's own vector. It knows where it is and where it's going. Interestingly, the vector components (groundspeed, track, rate of climb and rate of turn) represent about the same amount of data as ID does. So why should all the other planes have to make those calculations all over again? If there are a hundred aircraft, each one has to receive and store successive positions from the other 99, and has to calculate for each. So we have identical computations going on 99 places at once. This is needless. It's absurd. If a hundred unnecessary computations are going on in a hundred planes, that's ten thousand unnecessary determinations every second. Processor time would be better spent figuring out something the first plane didn't already know.
Plus, to make those determinations, at least two successive databursts must be flawlessly decoded. Until two positions are received and matched together, it's impossible to know which way the traffic is moving, what speed, and whether it's a potential threat or not. That means waiting for the second databurst, which takes time, precious time that would be better spent avoiding the accident. If the databurst contains the vector of the other aircraft, then the data is ready to use instantly. No need to store 198 sets of data and keep straight which belongs to who, no need to wait, no complexity introduced by missing databursts. When one burst comes in intact, all the data is instantly available to calculate a possible conflict and work out any necessary evasive action.
This is the sort of thing that is obvious to pilots, but not to Lincoln Labs. Or the FAA.
If everything necessary to evaluate the threat is contained in one burst, then the requirement for data integrity is eased. That is, we can sustain more signals being stepped on. And this directly relates to the number of planes that can be accommodated, how much range can be achieved, how reliable the whole thing is, how much it costs.
So the signal should not contain ID. These bits are needed to carry important data. A safe driver watches the other vehicles, he doesn't concentrate on their license plates. Same idea.
As many readers of THE OTHER WING know, AirSport manufactures receivers that decode all the data that the aircraft transponder is reporting to Air Traffic Control. They display that data for the benefit of the pilot. These receivers pick up 1090 MHZ. If more data could be packed onto that frequency, we could offer more benefits to our customers. So I'm not opposed to Mode S GPS on business grounds. Quite the contrary, if additional signals would fit at this spot on the dial we would love it. But there isn't any room. When Mode C was mandated a few years ago the resulting growth in transponder signals caused increased traffic spacing and led to the Northeast Reorganization Plan. Since Mode S testing began at Baltimore and Orlando, controllers are constantly complaining about "defective" general aviation transponders in those areas. As use of TCAS has proliferated, ATCRBS reliability has plummeted. If aviation is to survive, we cannot continue to pile more and more on this one frequency. I wish the pilot's organizations would understand that.
The collision avoidance equipment of tomorrow must be right for aviation, not what appears acceptable to Lincoln Labs. We need to remind the non-pilots that they are exactly that. I wouldn't begin to tell a surgeon how to carve the body; those non-pilots have no business telling us what information we need in the cockpit. And until they greatly improve magnetos and exhaust valves they have no business talking about 99.999% reliability, either.