Collision Avoidance. It's a term pilots hear often, and for good reason. Avoiding collisions with other aircraft is one of the most critical objectives pilots manage every flight. Mid-air collisions are almost always fatal, and they can happen with little or no warning. The risk of a mid-air collision never goes away. Every second of every flight, day or night, good weather or bad, the risk of a mid-air collision lurks in the background. In your mind, however, consideration of that risk should be in the foreground.
The recent mid-air collision over the Hudson River resulting in the deaths of nine people is a sobering reminder of this. It's easy for pilots to forget about the danger of mid-airs. It's extremely rare that we unintentionally share our airplane's personal space bubble with another aircraft. Heck, on some flights we hardly even see other aircraft in the sky around us. It's easy for us to feel like we are alone in our chunk of the sky and relax, or altogether discontinue, our traffic scan. We figure the sky is big, so what are the odds that another aircraft is going to occupy the exact same piece of it simultaneously with us? That depends.
In the vicinity of an airport those odds increase drastically. In the case of the recent Hudson mid-air, the probability of a mid-air collision was markedly higher than in most areas of the country because of the business and congestion of the New York terminal area. It's like a bee's nest for aircraft. And when the weather is good (as it was the day of the Hudson mid-air), watch out. The odds of bumping into another aircraft increase even more. Although that might be counterintuitive at first, remember that good weather not only means more airplanes in the sky, but less ATC control and separation of those airplanes. When weather is good VFR, the total number of aicraft in the sky increases while the number of aircraft being positively controlled and separated by ATC decreases. That spells increased collision risk.
Most mid-air collisions occur during daytime VMC in the vicinity of an airport, just like the Hudson mid-air. But mid-airs can happen anytime. It only takes two airplanes in the sky to introduce a collision risk. The collision of two vintage airliners over the Grand Canyon many years ago was an excellent example of this. The two airplanes were virtually the only ones in the area, yet they collided killing all aboard. Anytime there's another guy up buzzing around in the same sky as you, there's a chance you could smash into each other. Throw more airplanes into the mix, as in the vicinity of an airport, and you better watch out.
The FAA's "Operation Lights On" program suggests pilots turn all external lights on (including landing lights) within ten miles of an airport, and/or when operating below 10,000 feet MSL. Lights should also be on during reduced visibility or, of course, when taking off or landing. Landing lights should be used even during daylight. The use of external lights helps manage collision risk by making your aircraft more conspicuous to other traffic.
Remember to maximize use of internal and external resources. If you have passengers aboard, brief them before engine start to speak up if they see traffic. Use effective scanning techniques when searching for traffic. Remember, the human eye takes a second or two to focus after it fixes on an area. Sweep the area around the airplane in short, ten degree segments, pausing 1-2 seconds each segment. Sweeping your eyes in a nonstop motion across the sky is unlikely to help you spot other aircraft because your eyes will be out of focus and their motion-detecting ability will be compromised. Use traffic avoidance systems such as TIS or TAS only as a secondary or backup means of avoiding other aircraft, and remember that those systems will not warn you of aircraft without a transponder. Never relax when the TIS/TAS display shows no other airplanes around. There could be a J-3 Cub without an operative transponder converging head-on with you. Minimize "heads down" time in flight and remember most of your attention should be focused outside of the airplane while in visual conditions, even when on an IFR flight plan. ATC only separates IFR traffic from other IFR traffic; it's the VFR guys you need to be concerned about. Just like the regulations state, it's the responsibility of the pilot to maintain separation from other traffic while in visual conditions. ATC can't separate you from someone they don't know is there (i.e. a VFR aircraft without a transponder).
If flying VFR, utilize ATC Flight Following whenever possible. This is one of the best external resources VFR pilots have available to help manage collision risk. This service also helps manage risk in other areas such as terrain and airspace avoidance. Always follow AIM-recommended procedures regarding traffic patterns to assist other pilots in knowing where to look for you. When the flow of traffic is orderly and predictable, there's less risk of a mid-air. And, of course, always use the CTAF at uncontrolled airports to let other pilots know where you are and what you're doing.
Our current collision avoidance system for VFR aircraft is limited in the United States. It relies almost completely on the "see and be seen" or "see and avoid" principles, and that doesn't work sometimes. It didn't work over the Hudson, and nine people are dead because of it. Luckily, transponders and traffic avoidance systems are becoming more mainstream and widespread throughout the GA community. That's a big step forward, but remember the best method of reducing collision risk is to keep your eyes outside of the airplane searching for threats. Don't expect the other guy to be looking for you, because often he isn't. It's your responsibility to keep yourself separated from other aircraft, so take it seriously. Your life depends on it.
