Commercial single and multi-land, instrument airplane, BSEE & MSEE, faculty University of Florida and Texas & Embry Riddle Aeronautical University, 20 yrs avionics design. First GPS, First GPS-Loran, first GPS moving map, first GPS-ILS, first GNSS Cat. III c, first transponder proximity detector, first passive radar, first working and affordable collision avoidance system

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We now have the worst air traffic delays ever experienced, and the margin of safety is decreasing inversely with the level of separation. The present system capacity is limited, and presently, it would seem, stretched to beyond that limit. The problems are entirely hardware. They can, however, be fixed with a simple modification to existing equipment, at a cost of about $500 per aircraft.

The efficacy of FAA management can be evaluated by comparing the FAA official report on the ATCRBS transponder technology operability problems set (http://www.gtwn.net/~keith.peshak/tn97_7.pdf) with the incongruous statement by the permanently employed top FAA official in charge (4th paragraph of http://www.gtwn.net/~keith.peshak/mcfaa.pdf). The former states that 96% of aircraft transponders do not work right, based on actual specified testing, the latter states that number to be smaller, with no stated criteria. At issue is the question, in order to direct air traffic, should ATC be allowed to see the airplane at all.

It is possible to independently research how FAA management damaged the formerly functioning transponder based ATC system capability. The transponder interrogation classically once consisted of three pulses, in time order, designated P1 then P2 then P3. If the transponder ever hears P2, the "side lobe suppression rule" was to thwart any reply from the transponder. This was done to prevent the "radar" from seeing the airplane, under that circumstance of that airplane positioned within the side lobe of the "radar" antenna (a wrong thing, if it were to reply from there). Since the P1-P2 spacing was always to be 2 microseconds, and since there would never be any other case of an interrogation containing two pulses spaced 2 microseconds (http://littongcs.glyphix.com/products/3iff/iffqa.html), the rule oft implemented in transponder detection circuitry was "if you ever hear two pulses spaced 2 microseconds, thwart reply". The remaining two rules for the civil aviation transponder are, "if you ever hear two pulses spaced 8 microseconds, reply squawk code" and "if you ever hear two pulses spaced 21 microseconds, reply altitude code" (once only if no P2, referring to P1-P3). Then there was another rule about "if you ever hear P0, a noise pulse, ignore it". This was done to prevent the loss of a transponder reply from interference caused by there being too many "radar" interrogators in the area. Simple, elegant, required few vacuum tubes to implement. Worked everywhere but the Los Angeles Basin, because of there being too many interrogators in the area (FAA management immediately set about breaking rules).

Then the FAA management created the Mode S "radar" interrogator, which is designed so that the transponder will always hear the P3-P4 pulse pair spacing of 2 microseconds, during a period of time when the transponder is allowed to be listening, between end of interrogation and beginning of reply (a 3 microsecond waiting period after P3 time before F1 time). This brought the LAB problem to every TCA. Then the FAA created the TCAS interrogator, which fly through space on everything containing passengers spewing forth omnidirectional radiations of the P3-P4 pulse pair spacing of 2 microseconds, during a period of time when the transponder is allowed to be listening. This brought the LAB problem to every ARSA at slam dunk time.

The FAA management changed the rule on how transponders are to suppress. This is a change in rule, without a corresponding change in the transistors in flight. Creating TSO C74c, FAA management dictated to transponder makers in 1973, the "side lobe suppression" section, that if the transponder were ever to hear P3 and a pulse 2 microseconds after P3 (which we call P4), then the transponder is to thwart reply. No mention is made of P2. Try to state that clearly, in non-engineering terms: If the transponder ever hears a new ground radar interrogation or a TCAS interrogation, it is to ignore the interrogation and not reply. It is also to ignore the classical "prevent ring around the airport" command. This is the first proof of incompetence.

Most all transponders in flight today have been certified since 1973. Therefore, either one of two things: The transponder was certified to operate in accordance with C74c, but yet operates in the opposite to the FAA technical specification (call this case "works"), which is a second proof of incompetence; Or, in the alternative, the transponder does operate in accordance with C74c, and, therefore, does not operate in the ATC system (the "Terra Problem" - call this case "don't work"), which is a second proof of incompetence.

There is an additional issue, that should be addressed. The answer to the question how many transponders that were certified by the FAA to be compliant to the TSO C74c actually are compliant. The Terra line of transponder design, we know was, prior to the "fix" to make it non-compliant, compliant. The early Narco AT-150, we know was, prior to the "hot wire" Q415 circuit addition to make it non-compliant, compliant. Vast resources were squandered to find those compliant transponders, in order to render them non-compliant. Did we get them all? Are there other marks that should be made non-compliant to the TSO, so that they will become functional in the ATC system? The FAA technical study report, where insitu transponders were actually tested, to specified criteria, says 96%! Mr. McSweeny says 'don't worry'.

We solve this problem, completely, with a retrofit interrogation detection system on a chip (custom VLSI IC SoC), to replace the large number of small scale integration chips in the existing aircraft transponder with a fixed tuned, always compliant VLSI circuit "fixkit" (http://www.gtwn.net/~keith.peshak/ic.htm). Like any avionics shop has always been authorized to do in the past, without any STC, remove that and replace with this. Here is an example of an FAA order to do exactly that, on a King transponder (http://www.gtwn.net/~keith.peshak/King%20AD.htm) without an STC.

We stabilize the present ATCRBS system technology, and we eliminate, at the same time, the need for biennials to "adjust" the transponder, to keep it working within the ATC system. Fear not, this wasn't hard - all it does is to ignore P4, just as if it was never required to be transmitted by FAA management! And return the SLS function to be keyed off of P2 following P1! Cost to the aircraft owner, only about $500 (which is about the cost of the continuing biennial he would suffer for required periodic adjustment without the fix kit). The solution actually saves money (the aircraft owner about $250/yr), in addition to restoring ATC system reliability.

The story would end here, if there were not an additional fault in the ATC system hardware architecture. This, also, can be fixed, and from the transponder, and in the same IC that was used to correct for the FAA generated P4 problem set.

The FAA operators of the system have noticed deficiencies in system performance, to the extent that aircraft seen by radar are not showing on the radar planform display (http://home.columbus.rr.com/lusch/rtudslide00.html). This problem is quite complex, and more serious, though the solution is simple.

We are presently using an imperfect directional ground antenna, which has side and back lobes, and which has a wide beam width, to squirt interrogations and receive replies. Because a picture cannot be drawn from such information, we are using a computer to measure antenna "direction", and rotation rate, and interrogation sing rate, and replay sing rate, with the result to calculate each aircraft position from its "song". This works only when there are few interrogators (we now have a sky full of TCAS and TCAD active interrogators), and when there are few aircraft (we now have a sky full of ADS-B and Mode S interference sources, and there is a requirement, commonly violated, of a minimum spatial separation of aircraft so that transponder replies do not overlap on top of eachother in space). Simply put, different "radars" see the same airplane at different places (the simple additional problem), and many "radars" all do not see an airplane when basic electrical parameters, such as minimum separation and frequency quieting, are violated (the not-so-simple additional problem). In point of fact, it is good that not so many transponders actually work right, because, if they did, then the system wouldn't. There isn't the computer power!

This problem set can only be solved by going to a non-traditional computer architecture (associative parallel processing), which is a "junk this and start over", or finding a way to avoid the necessity of computer power to calculate aircraft position. Remember, the present ground equipment listens to what the airplane says.

Instead of requiring computer power to calculate where the airplane is, simply augment the system technology in the aircraft transponder to allow the airplane to say where it is, position and velocity, in addition to what it now says, squawk and altitude. The aircraft, today, has the ability to possess a sensor to determine where it is. Loran-C is best but isn't everywhere, Glonass is second place but only has 1/3 of a full constellation remaining, GPS is a poor third place with less than 1/2 constellation with remaining minimal reliability and no second frequency and the high resolution signal still jammed with AS (anti spoofing). (http://www.gtwn.net/~keith.peshak/satnav.htm) Galileo will be clearly the best, but is only a plan at this time (three frequency, precision modulation). VORTAC is there, VOR/DME is there, VOR/VOR is there (Collins DCE, $85, http://www.wagaero.com), there could be NDB/NDB, ... Many options, allowing cross checking and redundancy.

FAA management wishes to replace old ATCRBS technology with new ADS-B technology (throw away, start over). The same idea, have the airplane say where it is. Unfortunately, the space in the data packet is utilized, greatly, for the transmission of an unnecessary piece of information - the world wide unique number for each different aircraft. These are much longer packets, and this requires that many packets be sent, to communicate one positional message. That effects the capacity of the system, to the extent that it is less than the capacity of the current system. This happens because of the monumental amount of jamming to ATCRBS. To be safe, when ADS-B was tested, the entire state of Ohio was grounded. ADS-B also poses a whole new set of safety deficiencies for the system, which have not been properly evaluated (http://www.gtwn.net/~keith.peshak/ADS-Bterror.htm), not the least of which is the ability to, with simple components readily available from a Radio Shack (http://www.radioshack.com), guide a missile to blow a particular specific aircraft (airforce 1) out of the sky, whilst avoiding all others that might get in the way (http://littongcs.glyphix.com/products/3iff/ppx3b/overview.html).

We can provide the advantages of ADS-B technology, while eliminating all of the limitations of ADS-B technology, within this augmentation to the ATCRBS VLSI fixkit, removing the need for then unnecessary TCAS and TCAD interrogations, and ADS-B incessant long message interference. All that is required is a rethinking of what information should be sent in the transmission, how often, and how to accomplish that to compliance within the existing ICAO standard packet format (http://www.gtwn.net/~keith.peshak/peshak22.htm).

There is no reason to eliminate ATCRBS as a technology, when the problems with P0, P4, "tuning", processor "horsepower" deficiency, interference, and bandwidth are all cured, allowing autonomous collision avoidance, and for approximately a $500 cost per aircraft. There is no reason to expend extremely large costs on a new ADS-B technology, both for aircraft equipment (estimated at $300,000/aircraft) and ground equipment (TIS estimated at billions of dollars for ATCRBS compatibility), when all of the necessary capability is provided into the current existing transponder equipment by one IC.

We now describe a working demonstrated solution for ATCRBS, that also includes a working demonstrated GPS input based AIS-P augmentation. Working equipment was shown at AirVenture99 and again at AirVenture2000 (http://www.airventure.org/forums/presenter.asp?EventID=12&PresenterID=538). A technical presentation is available on tape (#128 AirVeture99) from EAA (dcyeoman@juno.com or tpoberezny@eaa.org). We have proven that the existing ATCRBS "radar" system can be fixed to resolve all problems and deficiencies, while further augmented to provide all critical ADS-B objectives, eliminating the clear ADS-B limitations. The packet definition conforms to the ICAO message standard. We do, however, require that one of the available downlink format numbers be assigned to the packet format by request to Jack Howell (jhowell@icao.int).

This format was designed to eliminate the need for a microprocessor for GPS incoming message parsing, and transponder outgoing message assembly, which reduces the added component cost for the transponder fixkit, the development cost for software, and the humongous cost for the FAA management software certification process (DO-178).

The AIS-P augmentation to the transponder restores all of the ATCRBS collision avoidance operability not seen since the C74c TSO, and provides all of the ADS-B minimum collision avoidance requirements necessary for general aviation, and probably also commercial and military aviation. It accomplishes this without the severe cost and exposure ADS-B limitations. It completely repairs the problematic ATCRBS reply of all transponders to interrogations containing P0 and/or P4 pulses, and keeps the transponder always in "tune", eliminating the need for biennial. The equipage cost to restore being seen, and allow being seen better, and fix ATCRBS, has been reduced from $300,000 to about $500. The system capacity has been raised to far beyond what it has ever been, which is far beyond what it can ever be under ADS-B TCAS TCAD. This modification to the existing transponder is quite simple, removing the old detector digital and analog circuitry (http://www.gtwn.net/~keith.peshak/aispkit3.jpg).

Once accomplished, this alternative allows for an effective radar picture to be built (http://www.gtwn.net/~keith.peshak/AISP1.gif) from a software driver available from a radio amateur (bhildebrand@earthlinknet), which controls an off-the-shelf map product (http://www.delorme.com/). The data block is the location of the aircraft, and is the pressure altitude of the aircraft (same mode C blind encoder code currently in use). The triangle, the "Bob Collins Box", reaches out in the direction of the target travel, the distance it will cover in one minute of time. If the same pixel is painted green twice, you are alerted, and you have 60 seconds to clear the collision. This particular ASR comes in at about $5,000.

The only thing preventing us from sharing in the benefits of this technology is your FAA management: (http://www.gtwn.net/~keith.peshak/taillight.htm).