Gasps of disbelief exploded from AOPA Pilot Associate Editor Nate Ferguson and me during what was — up to that point — a routine landing on Runway 23 at Frederick, Maryland, last June. The unthinkable had just happened: Within seconds of our touchdown, another airplane, a Piper Arrow, seemingly appeared out of nowhere and landed in the same direction less than 250 feet in front of us.
We had just completed a long, straight-in GPS approach, making position reports along the way. The Arrow, we learned later, flew a standard left traffic pattern to the same runway and never saw us as the instructor coached a commercial student through power-off, spot-landing drills. The instructor claimed he made position reports, but we never heard them. Fortunately for all of us that day, it was nothing more than a good scare.
But who was at fault? We'll never know. But maybe more important is how to avoid the same situation in the future. This is one of the scenarios tailor-made for collision avoidance systems and what a new line of traffic advisory systems (TASs) from Avidyne — including the first active collision avoidance system available for less than $10,000 — is all about.
On November 3, 2005, Ryan International Corp. and Avidyne — maker of FlightMax products such as the EX500 and EX5000 multilink multifunction displays (MFDs) and the Entegra integrated flight deck that's standard equipment on new Cirrus Design, The New Piper Aircraft, Adam Aircraft, and Symphony Aircraft Industries airplanes — announced the two companies were merging. Three new TAS products were introduced and special pricing was announced for bundled TAS and Flight-Max products.
The Ryan TCAD 9900BX system, an active system, became the TAS620. Two additional active TAS models also were introduced.
Active systems transmit interrogation signals. Nearby Mode C- and Mode S transponders reply with altitude data. Range is determined using radar time of arrival between the interrogation and reply signals. Bearing is determined using dual directional antennas — one located on the top of the airplane and the other a patented dual-blade antenna on the belly.
The new active traffic systems include the TAS600, which is designed for single-engine piston airplanes. It interrogates aircraft within seven miles and 3,500-foot vertical separation up to 18,500 feet msl; the TAS 610 is intended for midlevel-altitude airplanes by interrogating transponders within a 12-mile radius, within 3,500-foot vertical separation up to 25,000 feet; and the TAS 620 is intended for high-altitude aircraft — it interrogates out 21 miles within a 9,900-foot vertical separation up to 55,000 feet.
Before the merger, Ryan sold a passive system — the 9900B — that received and crunched nearby transponder replies. The Avidyne factory now offers an upgrade to convert the 9900B to TAS600, -610, or -620 configuration.
Simply put, the family of TAS600 systems reaches out electronically for transponder-equipped airplanes and automatically warns the crew through visual and audio traffic advisories when there's the possibility of a collision within 15 to 30 seconds.
Ryan developed the following terminology for its TAS: An "intruder" is any transponder-equipped airplane within the surveillance range. Intruders being tracked that aren't a threat to the host aircraft are termed "other traffic" (OT). A target that is of concern but not an immediate hazard generates a "proximity alert" (PA). The processor continually monitors changes in range and altitude. When the processor calculates that the time to closest point of approach (CPA) of an intruder will be 15 to 30 seconds — this varies according to aircraft type and speed — a traffic alert (TA) is generated and, using a feature Ryan calls its "audible position alerting" (APA), this generates an audio warning.
If we'd had a TAS600 last June, the Arrow in the pattern would have first appeared as an OT symbol, an open-centered blue diamond. As we flew toward the airport, the symbol for the Arrow would have changed to a solid blue diamond, the PA symbol. The OT and PA would have alerted us to the presence of the Arrow with plenty of time to take appropriate action to avoid a close encounter. Otherwise, when the processor in the TAS600 decided that the two airplanes were within 30 seconds of a collision, a TA symbol — a solid yellow circle — would have appeared and an APA would have sounded in our headsets. The APA warning starts with a tone and is followed by the announcement, "Traffic" and the clock position of the intruder and the range and relative altitude. We would have heard, "Traffic, nine o'clock, same altitude, less than one mile" as the Arrow turned base.
The new TAS600 family of systems consists of a processor box and two patented antennas. The TAS units are compatible with all common MFDs and electronic flight information systems (EFISs), as well as popular electronic HSI (horizontal situation indicator) displays and with Garmin's very popular GNS 430- and 530-series GPS/nav/com units. The AOPA sweepstakes Rockwell Commander 112A has a Ryan 9900BX, which displays alerts on both the forward-looking primary flight display and the overhead view of the navigation display of the Chelton Synthetic Vision EFIS.
The TAS600 family of systems can be installed in a variety of ways: as an audio-only system, or with an Avidyne display/controller; or with an Avidyne multihazard display; or interfaced with a multifunction display or EFIS. The audio-only system issues APA warnings for TA aircraft. The audio warnings are augmented with a panel-mounted "traffic warning" light.
The display/controller option — sometimes referred to as the "digital display" — is one step up from the audio-only system. The panel unit measures 3.26 inches wide by 1.5 inches high, so it takes up very little panel space, and is most often purchased by owners who don't have an MFD. An additional feature of the digital display is an altitude alerter. Although this display option does not have a screen to display OT and PA symbols, it provides "look for" guidance by displaying the whereabouts of PA and TA intruders in relative altitude, range in nautical miles, and general bearing. There is a set of symbols depicting whether the intruder aircraft is in a climb, descent, or level flight path relative to the host aircraft. If the PA gets close enough to become a TA, an additional symbol is displayed along with an APA. There's also the provision to install a separate TA light if desired.
The second Avidyne display option is what the company calls its "multihazard display" (MHD). This display is like a mini MFD in that it is a full-color active-matrix liquid-crystal display, yet it takes no more panel space than a typical analog flight instrument. It also features an altitude alerter with audio annunciations such as, "One thousand feet to go; 500 feet to go; at altitude," and can be integrated with an L-3 Stormscope WX-500.
The TAS boxes have two sensitivity ranges. During normal flight operations the airspace monitored is at system maximum in what Avidyne calls "Sensitivity Level B." When the landing gear is extended, or the GPS switches to Terminal mode, the system automatically switches to Sensitivity Level A. This reduces the time to closest point of approach and the volume of monitored airspace. Other automatic functions inhibit APA advisories when the airplane is on the ground.
At any time, the pilot can push the yoke-mounted Mute button twice to refresh the display. This feature permits the pilot to ask the system for a fresh picture of the traffic situation at a time that's convenient to the pilot. This refresh feature is valuable as a final traffic check before taxiing on the runway for takeoff at an untowered airport, especially when the takeoff is into IFR conditions with low ceilings.
The highest expression of this merger is the introduction of Avidyne's MHAS-6000 system that consists of an Avidyne full-color FlightMax EX500 MFD coupled with the TAS600 system appropriate for the airplane. The result is a multihazard avoidance system that provides the pilot with a one-stop display that can be toggled between datalink weather, airborne color radar (if equipped), and the latest in traffic alerting technology, terrain, obstacles, and moving-map capabilities, as needed. Options include interfaces for enhanced ground proximity warning system (EGPWS) and Avidyne's CMax JeppView electronic approach chart display for enhanced situational awareness during instrument procedures and while taxiing.
Introductory prices for the multifaceted MHAS6000 systems are discounted with the TAS600 system retailing for $16,985, the TAS610 system retailing for $22,985, and the TAS620 system going for $27,985. Prices for add-on TAS systems begin at $9,900 for the 600.
With more airplanes occupying the same amount of airspace, a state-of-the-art traffic advisory system is an invaluable tool for today's pilots. Having flown with the Ryan 9900BX for more than 100 hours in the AOPA sweepstakes Commander, it didn't take me long to appreciate the comfort of having what amounted to a silent crewmember who was continually focusing his electronic eyeballs on the task of protecting my passengers and me by finding and tracking nearby traffic.
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Links to additional information about Avidyne may be found on AOPA Online.