When you're scanning for other traffic, it's easiest to spot airplanes moving quickly that contrast with the background behind them. If an airplane suddenly appears motionless, it might be on a collision course with you. Here's why...

Video: Citation Jet And Light Piston Nearly Collide

Over the UK, a student and instructor experienced a near mid-air collision with a Citation Jet when it appeared just in front of them, on-course for a head-on collision. As you'll notice in the video, it's difficult to see the apparent motion of the Citation Jet until it speeds past. The instructor banks the airplane away from the jet just a few hundred feet away from a potential impact...

So, how can you avoid something like this happening to you?

Understanding Apparent Motion During Your Traffic Scan

When an airplane is headed towards your path of flight, it will often appear motionless. Because it's not moving up, down, left, or right through your field of view, it's hard to spot.

This isn't really an optical "illusion" per se. It's simply the lack of perceived motion of another aircraft in comparison to your point of view. When you spot an airplane headed toward you, it might appear small at first, with a small growth rate (size perception). As traffic gets closer and closer, the growth rate will increase dramatically as the other airplane fills your field of view. Scan for traffic in 10-degree increments, and if you see another airplane that appears to float motionless in the sky, adjust your course right away.

Is The Traffic Moving Away From You?

During the daytime, it will be initially difficult to tell if the traffic is moving towards you or away from you. You'll have to analyze the aircraft to see if it's getting bigger, smaller, or staying the same size to determine its direction of flight.

Traffic can be hard to spot at night, but you'll have one upside. Aircraft position lights can help you determine which direction an airplane is moving. Red is always on the left wing, and green is always on the right.

ADS-B Can Be Your Best Pair Of Eyes

ADS-B "In" is a data link sending weather and traffic information into your cockpit. This data is transmitted from ground stations as well from other aircraft. While ADS-B "Out" is the only equipment that's required by the FAA, many aircraft are equipped with both. ADS-B In will give you the ability to find other aircraft well before you can see them. This is called TIS-B (Traffic Information Services - Broadcast), and it's sent to your airplane with ADS-B In.

With TIS-B traffic, you are able to see other planes around you on your instrument panel, or on an EFB application. This is incredibly helpful when you're navigating busy airspace. You'll be surprised at how many airplanes are flying around you that you can't spot visually.

Have you ever experienced a near mid-air with another airplane? Tell us about it in the comments below.