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Magic Box, Redux

Not quite a year ago, in August of 2002, I flew a Cessna 172 with a Traffic Proximity Alert System, or TPAS. Well, I've got a hot sequel for you. Actually, the folks at SureCheck Aviation out in Vista, California, are the ones with the scoop. The TrafficScope TPAS (VRX and VR) is a black box you'll soon be seeing in catalogs, at airshows, and by the time word gets around, probably in a cockpit near you.

Not quite a year ago, in August of 2002, I flew a Cessna 172 with a Traffic Proximity Alert System, or TPAS. Well, I've got a hot sequel for you. Actually, the folks at SureCheck Aviation out in Vista, California, are the ones with the scoop. The TrafficScope TPAS (VRX and VR) is a black box you'll soon be seeing in catalogs, at airshows, and by the time word gets around, probably in a cockpit near you.

The previous RX-110 model was a welcome prescription indeed, for the limitations of human sight, and provides the user with traffic advisories for any other transponder equipped aircraft within a selected detection radius and within 1800 feet of your altitude. It also uses a synthesized female voice to convey messages with escalating degrees of urgency. But as I concluded last time, a welcome enhancement would be to use the already available Mode C to provide an altitude readout, as well as simply range data. I had said: "I have a funny feeling they're working on it…" Well, guess what? They did.

Figure 1

Veni, Vidi, Vici: TCAS, TCAD, and TPAS
Traffic Alert/Collision Avoidance System (TCAS) installations have been in use in commercial aircraft for over 20 years. However, they're at least ten times too rich for our blood. Then came Traffic and Collision Alert Device (TCAD). Ever since TCAD devices came out, over a dozen years ago, pilots have been hoping for an affordable means of assistance to alert them to possible traffic conflicts. Just because you might file and fly IFR all the time doesn't mean separation is someone else's problem. Around uncontrolled airports or areas popular with VFR aircraft, especially when visibility is marginal and ATC is busy, both you and a controller could miss a few potential conflicts. And one is all it takes.

TrafficScope has the same TPAS technology that indicates whether (and whenever) your aircraft is being interrogated by a TCAS-equipped aircraft or a ground-based Secondary Surveillance Radar. Like TCAD, and the RX-110, the VRX works only if the other airplane has Mode C and is being interrogated by radar. Of course, it's a given that where it's already busy, and where Mode C is already required (particularly in areas where the concentration of aircraft is already significant), such a limitation becomes pretty much an academic one. I don't mean to sound like the guy in the striped suit selling snake oil, but wait 'till you hear what else they've packed inside the follow-on unit (which is also about half the size of the -110). Incidentally, the TrafficScope comes in two flavors now: the VRX and the VR. (The VR is like the RX-110 in that it doesn't display relative altitude information.) I reviewed the VRX, which still costs a small fraction of the original TCAD units (and, I might add, a fraction of what a TIS-enabled Mode S transponder and a Garmin GNS 430 would cost) and it can still do quite a bit.

Like its predecessor, it's easy to set up...
Antenna: The stubby antenna doesn't take up much space (and you can get an extended antenna if the geometry of your panel and windshield doesn't allow for its three-inch height when mounted directly).

Headset interface: The patch cord connects in series with your headset jack -- they make a helicopter "Y" adaptor for the single-plug U-174U or U-93A/U type, used in helicopters. On the other end it has an "audio out" connection for the aircraft's audio and an "audio in" for the intercom. (It can handle both monaural and stereo systems.)

Power: Power comes either from four AA batteries or the supplied cigarette lighter adaptor.

Adaptability: The device's on-board solid state altimeter can adapt to the cockpit of a pressurized aircraft, by means of a switch inside the battery bay and can also be plumbed into an aircraft's static port line, for permanent installations.

It tells you at what altitude and what distance other aircraft are ... within a predetermined area. It does not tell you what direction you need to look to find those aircraft. Using the box is intuitively easy. Its traffic detection volume (or "threat detection envelope") is defined in two independently adjustable dimensions: horizontally (range), and vertically (altitude). Mode C transponders broadcast to the nearest 100 feet, so that's the resolution shown on the VRX. Range is shown to the nearest tenth of a nautical mile, and is determined from the amplitude of the received transponder signal. For traffic at lower altitudes, the VRX incorporates logic to compensate for signal attenuation caused by the airframe of the "threat" aircraft being between you and its transponder antenna.

The TrafficScope has four types of advisories, determined by algorithms that account for relative altitude, track rate, and range data. First, if there is no threat, you'll see a hollow diamond shape; if there is presently no threat but the traffic has moved closer in any direction, the diamond becomes solid; a traffic advisory is shown using a hollow square and is accompanied by an audio "traffic advisory" alert to remind you to try visually acquiring the threat aircraft; and last is a solid square and audio "traffic alert!" that tells you to make visual contact and possibly take evasive action. (There is a "mute" button available, should you wish not to have aural alerts, although I myself would probably be hesitant to use it.) Keep in mind that any traffic having vertical separation from you at one moment, could in another moment become a threat by climbing or descending through your altitude.

After initial power-up, the user is presented with the operational mode menu: flight, ground, or "auto":

In auto mode, the VRX decides when to switch from ground to flight modes (which it does whenever it senses that you've gained 500 feet).

In flight mode, the unit is looking both above and below you.

In ground mode, it only cares about traffic 200 feet higher, and up.

The next selection is the range menu. According to the Pilot Information Manual, aircraft three nmi or less from you are assessed first using their altitude, and then their range; any traffic seen beyond three miles is considered using relative distance first, before its altitude. Range settings can be selected for five, three, two, or 1.5 (nautical) miles.

The desired altitude window is the third menu selection that comes up. (The initial default settings for start-up are those for cruise flight: five nmi and 1500 feet.) You can select altitude detection windows of plus-or-minus 1500, 1000, or 500 feet.

Once you have made your selections, what the unit does for you goes beyond the old -110 model. Besides showing range and altitude for the closest threat aircraft, the new box also gives "MTI" or multiple-threat information. If the primary target moves off, it shifts its focus to the next-closest one. Actually, the little airplane or "double airplane" icon is actually two indications...

  • If only range and altitude are displayed (no MTIs), then only one Mode C aircraft is nearby;
  • if you see range/altitude + one MTI symbol, two such aircraft are near;
  • and with range/altitude + two MTI symbols displayed, three aircraft are near.

It also warns of possible wake turbulence, and advises you accordingly -- also in a pleasant female voice. It does that whenever it detects a Mode S aircraft (presumably something big) 1000 feet or less above you, within two miles. (The display symbol for detected Mode S aircraft on the TrafficScope is a swept-wing airplane icon.)

Other goodies... Pushing the "LOC ALT" button on the front panel tells you your own present altitude, based on its internal pressure altitude sensor. Next to that button also is a "XPNDR CONFLICT" light that illuminates to warn you if your transponder or altitude encoder were to fail. If on the other hand there was no radar coverage by ATC, the TrafficScope will tell you that, as well -- the "down arrow" would no longer show on the display screen. (A corresponding "up arrow" shows whenever your aircraft is interrogated by a TCAS-equipped aircraft.) If that down arrow does go away, it means there may not be any Secondary Surveillance Radar (SSR), and the unit won't be able to display traffic information. (This could happen if you were over 100 miles from the nearest ground-based RADAR installation, which in most populated areas of the country, would be unlikely.) If you're running on batteries alone, there is a battery indicator that appears on the display, along with a low power voice alert. There are also buttons on the display for a backlight and for a self-test mode.

Again, even the VRX doesn't give the azimuth (the "o'clock" value) of other traffic. And again, unlike TCAS, it's a "passive" system: it can only indicate Mode C traffic, and it won't do much for you in a non-radar environment. It won't indicate the Mode C altitude of any traffic that is above 25,200 feet, as it will display a constant "FL250" above this. Of course, if you're PIC this high up, you probably have TCAS, anyway. The unit also won't give altitudes for traffic below sea level. (So if you're in Death Valley, you'd just see a "zero" for any low-flying aircraft.) I still won't leave mine home, though.

Next time: We fly with one.

- SureCheck TrafficScope VRX Product Information

Note: If you're attenting AirVenture 2003, be sure to visit the new SureCheck booth #3108 in Exhibit Hangar C.

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