Tuesday, October 21, 2008

Assume a Frictionless Universe

As a diversion from recent events, I wanted to get on with some other posts I had in the pipeline.

I received a really cool gift a few weeks ago - a Zaon MRX PCAS (portable collision avoidance system). I've been using it for over a week now and wanted to share my observations on this fascinating product. You might be wondering why an instructor who trains in TAA (technically advance aircraft) with Traffic Information Service (TIS) would need a PCAS. And the purists out there say we should just be using our eyes to look for other aircraft, not fancy gadgets. You can explain most anything if you assume, as the old physics jokes go, that we live in a frictionless universe. The thing is, there's plenty of potential friction out there.

There are several reasons why a PCAS unit can increase safety and prevent collisions. Here are just a few:
  • There are several places I fly where ATC's radar doesn't support TIS.
  • I often fly aircraft that are not equipped with TIS (Traffic Information System).
  • Even when TIS is available, the Zaon MRX provides several unique advantages.

If you're like me, you get a sinking feeling when you hear the G1000's audible warning "TIS not available." This happens when you are out of radar contact or when you enter an area where ATC's radar does not support the uploading of traffic data to appropriately enabled, Mode S transponders. The NORCAL sectors around Stockton/Modesto and eastward do not support TIS nor does Travis Approach. These are areas I frequent with students and while I'm conscientious about scanning for traffic, let's just say I've been able to perform more air-to-air inspections on the rivets of other aircraft than I'd like.

The FAA put us on notice that support for TIS will be phased out over the next 7 years or so. This seems a fundamentally bad idea, based on the unrealistic notion that we'll all soon have ADS-B (Automatic Dependent Surveillance-Broadcast) and won't need TIS. Nothing could be further from the truth. ADS-B has yet to see the widespread acceptance that the G1000 and other TIS products have seen. I've never flown an ADS-B aircraft, but there must be thousands of G1000 aircraft out there using TIS to provide an increased level of safety. Ground-based support for ADS-B is supposed to be completed for the US National Airspace System by sometime in 2014. By the way, Garmin provided this map a while back to show areas where TIS is still supported along with when and where it will be phased out.

I've been using the Zaon MRX both in TIS-equipped aircraft and those that have no collision avoidance systems. The MRX only provides the distance and relative altitude to other aircraft based on their transponder replies; it doesn't tell you where the traffic is in relation to you. What I've discovered is that even when TIS is available and working, the MRX provides useful, perhaps lifesaving information.

You can set the warning envelope on the MRX and I usually use the 3 mile radius and 2000 foot altitude setting, unless I'm in busy, class B or class C airspace. When an aircraft gets too close, the MRX will flash, display the distance and relative altitude, and provide a beep. The warnings take two-forms - and advisory and alert. You can hook up the MRX to provide audible warnings through you headset, but I find I can see the flashing alert and hear the beep, even through a noise-canceling headset.

The MRX will detect pretty much any transponder when it responds to an interrogation from ATC radar or from another aircraft's TCAS. It is possible for the MRX to detect a collision threat from an aircraft transponder that is responding to a TCAS interrogation, even if the threatening aircraft is not in radar contact with ATC. Still, the MRX won't see all aircraft. It won't see aircraft that are not transponder-equipped or if the transponder of the other aircraft is turned off. I've also noticed that the transponder replies of aircraft below and behind my aircraft seemed to be masked and the MRX might not detect those aircraft.

Here are just a few of the dozens of collision threats that the MRX alerted me to in the last two weeks.

Scenario #1

On an approach to a Class Delta airport, we were told to "circle east, enter right traffic, report downwind." Reporting on downwind, the tower controller (who sounded like a trainee) told us a Lancair was inbound from the Northeast on a right base. The MRX showed an aircraft 2 miles and 400 feet above us and, suspecting it was the Lancair, I looked to our left and saw the traffic. We adjusted our pattern, keeping our base turn tight. The newbie controller had her hands full since the Lancair was coming in hellbent for leather, but she handled it pretty well. She told the aircraft on final approach for the parallel runway to go around and switched the Lancair to the parallel runway.

Scenario #2

With a commercial candidate, we'd been getting traffic advisories while doing chandelles, lazy eights, and what not. Finished with our maneuvers, we advised the controller we were headed to Oakland for a practice approach. I took the controls while my candidate donned his view-limiting device, the controller gave us a new squawk and then apparently got busy arranging the handoff to the next sector. Thats when the MRX alerted us to traffic within 3 miles at the same altitude. I scanned left to right and saw a Bonanza at our three o'clock. Thing is, we were heading 220 at 4500 feet and the Bonanza was eastbound at 4500 feet - WAFDOF (wrong altitude for direction flight). I descended 300 feet and the Bonanza passed overhead, apparently oblivious to us. The controller never said a word, probably too busy arranging the handoff.

Scenario #3

Flying ground reference maneuvers near the Sacramento River Delta, the MRX announced traffic within 3 miles at the same altitude. A quick scan and we didn't see anything, so we climbed 400 feet. That's when we saw a helicopter pass right below where we had been at the altitude we had been flying.

The MRX is lightweight, so I keep it in one pocket of my kneeboard and I carry the lightweight power adapter in the other kneeboard pocket. A friend turned me onto Garmin's Temporary Adhesive Disks. These disks provide as a convenient way to temporarily mount the MRX securely and then remove it with no trace of residue when you're done. I use just a bit of a single disk, one dab on each corner of the MRX. A good way to store the unit so that it won't stick to my kneeboard is to simply wrap it in a small sheet of baking parchment. I've mounted and re-mounted the MRX several dozen times and the four dabs of Garmin adhesive disk have yet to lose their grip.

The last thing I'll say about the MRX, especially to those of you who think having and using such a device is overkill, is that the unit has a great side benefit. I mount the unit on the top of the glareshield of whatever plane I'm flying and when I hear the beep, I look up. This can be especially important in a glass cockpit instructional environment, where it's easy for both the instructor and student to get distracted by the pretty colors. And the MRX audible alert sounds much sooner than, say, the G1000's traffic alert.

We don't live in a frictionless universe, there's a lot more traffic out there than we can see, and I'm a firm believer in using every and all available tools and devices. All's fair in love, war, and traffic avoidance.


PlasticPilot said...

Thank you John for this excellent review. I know the system, but never tried it, and was somehow hesitating, for some of the the reasons you mention.

I liked your pilot oriented review. Good work.

Sarah said...

I agree it's useful. I've been flying with one in my sailplane this season. It doesn't go off that frequently with +/- 2000 and 3SM range settings, but when it does my scan goes up a few notches. No close calls, but it has resulted in me picking out traffic I'd probably have missed before.

I've had more mixed results using it on the dash of a power-plane. As you say, reception below and especially behind is not great, probably because the signal is being shielded by all that metal. I've also had a few eye-opening "false alarms", typically with steep turns down low. I suspect these are false-echoes of my own transponder.

Definitely worth considering depending on how/what/where you fly, and I don't regret the $500 yet. If I were to depend on it more with power, I'd consider an external ( or multiple internal ) antennas. Anyone have experience with Zaon's extra antennas?

Colin Summers said...

I love my personal traffic system.


For all the reasons you mentioned, I pull it out and flip it on as soon as "Traffic unavailable" is spit out by the traffic lady in the G1000.