Plane & Pilot
Tuesday, September 6, 2011

When Airplanes Collide: Avoiding The Unexpected

With midair collisions showing no sign of decreasing, “See and Avoid” is more important than ever

The Visual Scan

The most important tool we have in avoiding a midair collision is our eyes. The problem is that most of us haven’t been taught a technique for using them effectively in the cockpit. Most of us are pretty confident that our standard visual scan is sufficient to make sure we don’t run into somebody else.

The problem is that the part of our eye that’s most acute comprises only 1% of our vision. It’s the central part of the retina (the lining on the back of the eye) called the “fovea.” Any detail outside that 1% is simply missed. We lose 90% of our visual acuity once we look anywhere outside of a 10-degree cone originating from the fovea. The bottom line is that if we look only straight ahead, we miss 99% of the sky.

Pilots need to employ a scan technique that optimizes their vision. The Air Safety Foundation suggests, “Scan implies a sweep of the eyes, while a proper scan for conflicting traffic is actually a sequence of intense, fixated observations. The eyes need one to two seconds to adjust before they can focus; a continuous sweep blurs the vision.” Separating the sky into “blocks” of 10 to 15 degrees and stopping in each “block” from left to right is an effective scan technique.

Most pilots also settle into a focus area that’s just beyond the propeller. This happens naturally after a minute or so of focusing on open sky. Pilots need to make a conscious effort to refocus on the farthest object in the distance—a cloud or mountain—to give their eyes a chance to break focus and spot possible conflicting traffic.

L-3 Traffic Avoidance System

L-3 Avionics must be doing something right, because they just sold their 15,000th collision-avoidance unit. Their SkyWatch system is well known in the industry and was the first certified collision-avoidance unit for general aviation. Today, Hawker-Beechcraft, Piaggio and Quest Aircraft install the unit in their aircraft.

One of the most full-featured TCAS systems around, the SkyWatch comes in both the standard “497” model and the “HP” version. SkyWatch works similar to other TCAS systems by continuously monitoring the location of nearby transponder-equipped aircraft, noting range, relative bearing, relative altitude and closure rate. Tracking up to 30 targets simultaneously, it uses this information to predict collision threats, and then presents potential hazards on a cockpit display (10 on the standard model, 35 on the HP).

For pilots who have never flown with a full-featured TCAS, it’s enlightening to suddenly see all the traffic around you that you never noticed with a visual scan. “The main benefits of installing a SkyWatch system are enhanced safety and the peace of mind that brings,” explains Larry Riddle, vice president of business development for L-3 Avionics Systems. “Customers often say they didn’t realize how many aircraft were in the air until they installed a SkyWatch system, and now they wouldn’t fly without one.”

In addition to standard TCAS functions, L-3’s SkyWatch system adds a lot of noteworthy features. The Look Up/Look Down display mode highlights specific layers of relative altitude range, which is useful during climb and descent where statistics show most midair collisions occur. SkyWatch also integrates with Stormscope lightning-detection systems. The unit’s “Verbal Intruder Positioning” (VIP) function verbally announces the range, bearing and relative altitude of threat aircraft through the cockpit’s audio system. This feature reduces heads-down time in the cockpit—critical in the airport area. Finally, L-3 Avionics adds a five-year warranty, giving owners peace of mind.

As far as the future, L-3 is adding ADS-B-capable versions of the SkyWatch HP and TCAS I models, which are expected to be available in 2012. L-3 Avionics says installation is easy. “Actually, it is the most retrofit friendly, given the single antenna that transmits and receives through all 360 degrees,” says Kim Stephenson, Aftermarket Business Development Manager. “It can be displayed on over 30 different displays from other avionics manufacturers, so most aircraft owners already have a compatible display in their cockpit.” SkyWatch is priced at $15,990 for the 497 system, $20,990 for the HP and $24,340 for the HP with the TCAS I configuration (all prices MSRP). Contact for more information.


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