By Robert N. Rossier, EAA 472091
One of the basic tenets of aviation is particularly simple: see and avoid. Whether we’re flying VFR or IFR, the rule is to keep a sharp visual lookout and steer around other aircraft that get in our way. It sounds simple, but at the same time, it can be a bit more difficult to consistently do than to say. If you’ve been flying very long, chances are you’ve had one of those close encounter situations arise where another aircraft materialized seemingly out of the blue, leaving you to wonder, where did that guy come from? Even if we are diligent, follow the rules, and maintain a vigilant visual scan, we can miss seeing other aircraft — even ones that are pretty close.
The ADS-B Wake-up Call
For the past year or two, I’ve been flying aircraft equipped with ADS-B (automatic dependent surveillance-broadcast). For those who might not be familiar with this technology, it is a GPS-based system that displays the location and movement of other ADS-B equipped aircraft. Beginning in January of 2020, aircraft will be required to be equipped with ADS-B for operations in the airspace defined in Part 91.225, which includes Class A, in or above Class B and C, within a 30-mile radius of Class B, altitudes above 10,000 feet MSL, and some additional Class E airspace above 3,000 feet MSL or 2,500 feet AGL (read the regulations for details).
Using ADS-B has been an eye-opener, so to speak. On more than one occasion now — actually in far too many occasions — I find that my ADS-B will alert me to aircraft that, while relatively close to me, were totally invisible in my normal scan. Think about that. How many times have you had another aircraft report somewhere in your vicinity, and despite your head-bobbing, squinting, and scanning, you somehow never saw it. Eventually you realize it is no longer a factor, and your focus shifts. Where did it go? How close was it? It might make us wonder just how good our visual scanning techniques are. And since not all aircraft are ADS-B equipped, it might make us wonder how we can up our game in traffic avoidance.
Basic Scanning Technique
The basic scanning procedure we’re taught as pilots (see FAA Advisory Circular 90-48D) is to scan the sky in sectors perhaps 10 degrees wide. We stop our eye movement in each sector and focus for a minimum of one second before moving on to the next sector. And, of course, we need to periodically check our flight instruments and gauges to ensure all is going as planned.
This basic scanning technique recognizes some of the limitations of human vision. First is that we have sharply focused vision only in a narrow cone of our visual field called foveal vision. We also can detect the movement of objects much easier than we see a change in their size. The unfortunate upshot is that we are less likely to see an aircraft on a collision course with us, since it has no relative motion. But that’s just the start.
The Limits of Vision
Any number of factors can limit our ability to see, and therefore avoid, other aircraft, even in good and legal VFR conditions. Perhaps the most common is the haze that often comes with the heat of summer. Hazy conditions can obviously limit visibility, but they also make it difficult to pick out aircraft, even when they’re relatively nearby. Combined with other scenarios such as a lowering sun angle, we might find that it’s difficult to pick out an aircraft unless it has an operating landing light or strobes. The practice of using the landing light for all takeoffs and landings not only is simple, but also can be highly effective in improving the chances of others seeing us and avoiding that unwanted close encounter. But even landing lights and strobes aren’t perfect solutions for all situations.
Even without any haze, the glare from the sun can also make it difficult to see in many conditions. This can be a particular problem both in takeoff and landing situations, as well as in cruise flight, if we’re flying in a direction toward the sun.
It’s easy to think that in a big sky with few aircraft, the likelihood of aircraft coming together to occupy the same space at the same time is pretty low, but that situation changes when we’re in locations where aircraft tend to congregate, such as near VORs, along shorelines, or in other areas where pilots like to navigate or sightsee. In these areas, a vigilant lookout is even more critical.
The traffic pattern is a pretty small chunk of aerial real estate where aircraft by necessity come in close proximity to one another. Here, another hazard arises with aircraft of different configurations. The pilot of a high-wing aircraft has little upward visibility, whereas the pilot of a low-wing can have restricted downward visibility — hence the issue of a low-wing aircraft descending on top of a high-wing aircraft. Such encounters often end in fatalities.
Visual scanning isn’t effective unless we actually do it, and one way pilots can suffer a close call is to change direction without ensuring the area is free of other traffic. Clearing turns can be essential to collision avoidance, and pilots who don’t do so can be putting themselves and others at high risk.
Another issue that confounds our attempts at spotting aircraft in flight is something called empty field myopia. This occurs when looking out into an empty or featureless sky where the eye has nothing on which to focus. In this situation, the eye typically tends to naturally focus at a distance of 10 to 30 feet. In essence, we become nearsighted and are unlikely to detect an aircraft in the distance. To help refocus our eyes, we should occasionally focus at the wingtips, on objects on the ground, or, when flying at night, at distant lights.
More Collision Avoidance Strategies
Considering the limitations of both our human vision and modern cockpit technology, we need to take advantage of any additional tools we can bring to bear on the problem of collision avoidance. One great strategy for collision avoidance is to use ATC flight following services. Rather than rely strictly on your own ability to visually pick out potentially conflicting traffic, using this service puts to use the ATC radar system combined with the expertise of controllers to give us a heads-up on traffic.
Although visual scanning is critical to the process of collision avoidance, we shouldn’t overlook the value in closely listening to what’s happening around us. That includes listening to the tower frequency when operating in or near B, C, and D airspace and using the CTAF when operating at nontowered airports. But even that can leave us blind in some cases. For example, aircraft operating under IFR to and from nontowered airports may be using the local approach frequencies, so it can help us to listen in on those frequencies to know when traffic is headed our way. Again, ATC flight following can help give us a clearer idea of what is going on around us.
Final Analysis
There is no silver bullet when it comes to the problem of avoiding traffic. Without a doubt, having an aircraft equipped with the latest technology — ADS-B — is a huge step in the right direction, even though not every aircraft has this technology. After seeing how much better it is at spotting aircraft than I am, I recognize the need to up my game and use every available strategy to avoid those close encounters.