EAA Sport Aviation - February 2011

he night sky can be a dangerous place for
the unprepared pilot. By observing the
following precautions, we can better prepare
ourselves for the challenges of a night flight.

• Establish personal weather minimums for night flight that accurately reflect your experience and training. In general, these minimums should be higher than they are for daytime flights.

• Always obtain a thorough weather briefing before launching into the night sky. Remember that clouds and weather conditions that you would avoid in daylight can be hidden by darkness. Never attempt VFR flight when there is a possibility of getting trapped in deteriorating weather.

• Before attempting night flight with visibility less than 5 miles, seek training and maintain proficiency in aircraft control by sole reference to instruments. Training should include recovery from unusual attitudes.

• When possible, use flight following or other radar services to assist in collision avoidance.

• Use all available cockpit resources at your disposal. This includes GPS, DME, and other navigation aids to assist in terrain/obstacle avoidance and descent planning.

• When flying at night or in reduced visibility, use flight instruments in conjunction with visual references. Cross-check the instruments frequently as part of your scan to avoid the effects of visual illusions and to ensure positive control of the aircraft is maintained. Rely on instrument indications unless the natural horizon or surface reference is clearly visible.

• Remember that night falls early in the winter, so be prepared for delays that could extend your flight into the darkness hours. Beyond the regulatory requirements for night flight, be sure to get the training needed to be current and comfortable with the night flying environment.

Finally, we can look for the telltale signs that we’ve gone astray. Twinkling lights on the approach suggest trees between us and those lights, and signal the need for an immediate go-around.

FALSE HORIZON

Other illusions in the night sky can lead to disorientation. Lights lining a highway or other linear terrain feature at night can create the illusion of a horizon, tempting us to roll our wings in alignment with that feature. The result can be an unrecognized descent, steep bank, or other unusual attitude as we make improper control inputs to correct the perceived picture.

DODGING THE LIGHTS

Another illusion we can suffer on a starry night is apparent movement of a stationary light. When we look directly at a stationary light in a dark background, it can suddenly appear to move. This phenomenon, called “autokinesis,” can cause a pilot to become distracted or even to initiate an evasive maneuver to avoid what appears to be another aircraft.

To avoid autokinesis, refrain from staring at a single light for too long and use a systematic scan. Break the viewing area into segments that are roughly 10 degrees wide, and only fix your gaze in each segment long enough to focus. Then move on to the next segment, and repeat the process. Some pilots find that they can more easily detect relative motion by using their peripheral vision at night. Again, avoid fixating your scan for too long in any one segment.

Numerous pilots have reported a similar illusion when viewing a bright star (or planet) in the night sky. A bright, “rising star,” such as Venus, just above the horizon can look like the landing light of an oncoming aircraft, causing the pilot to alter heading or make an abrupt avoidance maneuver.

Perhaps the best guard against mistaken identity in the night sky is familiarity. Spend some time learning about the sky, the constellations, and their movement through the heavens. The more familiar we are with the sky, the less likely we are to be fooled by a bright star.