Flying after sunset presents unique challenges and rewards. To receive a Private Pilot’s License in the US, the Federal Aviation Administration (FAA) requires no less than three hours of night flight training, consisting of one cross-country flight over 100 nautical miles total distance as well as 10 takeoffs and 10 landings to a full stop with each landing involving a flight in the traffic pattern at an airport. While private pilots may choose to avoid taking to the skies at night, it’s a basic part of the job for commercial airline pilots and they will normally find a mix of day and night flying on their schedules.
Night flying has its own unique benefits. Turbulent air from the earth’s heating during the day dissipates as night falls, often making for much smother rides during the hours between sunset and sunrise. City lights uniquely illuminate population centers in a surprisingly discernible pattern out of the darkness. And on a clear night, star formations and other meteorological wonders await the pilot looking above the cockpit displays for just a few moments. A lower number of aircraft in the skies also reduces the workload for air traffic controllers and frequently allows pilots greater options for shorter, more direct routes. If you were to ask most pilots about flying at night, many would respond with descriptions including the words "calm" and "peaceful." And it often is, but night flying presents challenges too, and a professional plot must be prepared to mitigate those challenges.
Once the sun sets, a whole different side of aviation reveals itself and takes to the skies until the wee hours of the morning. For pilots, a unique series of requirements and skill sets comes into play for late night flights. Aviation is a 24/7 business where the clock is little more than a number for the departure or arrival of planes flying at night. Certain segments of the industry kick into high gear once the sun sets, particularly freight operations. Every weeknight, the FedEx World Super Hub in Memphis, Tennessee, becomes the world’s busiest airport. Each night, an average of 1.3 million packages arrive, are sorted, and head back out to their next destination via hundreds of aircraft. Their operation contains over 300 miles of linked conveyor belts which comprise a digital sorting and processing system for domestic and international small packages transshipped through the facility.
Night flying brings its own set of challenges. Fatigue becomes a potential issue for pilots even when they are relatively used to flying at night. Poor lighting in the aircraft can cause issues for navigation during night flights as well. Plus, it can lead to inadvertent flight into clouds, referred to as instrument meteorological conditions (IMC). Proper planning takes these threats into account and makes for as safe a flight as possible. Further, at night our eyes require more oxygen to function. Hypoxia is a condition with which pilots of all aircraft types must be aware. It occurs when the body lacks sufficient oxygen, and its effects become more pronounced as altitude increases. At night, the given altitude at which a person could experience symptoms of hypoxia, including difficulty breathing, anxiety, headache, lack of awareness, or even unconsciousness, decreases. Pressurized aircraft mitigate this by maintaining a constant cabin altitude as the plane climbs or descends.
The FAA’s Pilot’s Handbook of Aeronautical Knowledge states it can take as long as 30 minutes for the eyes to adjust to the darkness. Reintroduce a bright light, destroying this adaptation, and the process must begin again. For this reason, pilots avoid bright lights during night flights and tend to keep the lighting in the cockpit minimal. Bright lights can also come from outside the cockpit, so airfield lighting must be kept to the lowest usable intensity. At large airports, lighting intensity is controlled from the ground. But, at smaller airports (including the one where I learned to fly), the responsibility for controlling runway lighting can be in the hands of pilots who must adapt to utilizing the lowest level of lighting that provides usefulness and safety.
Night flying also presents any number of potential threats, such as challenges to depth perception, distance interpretation and optical illusions with which pilots must contend. There are two common night vision challenges. The first is the autokinetic effect (also referred to as autokinesis), a phenomenon of visual perception in which a pilot fixates on a small stationary point of light in an otherwise dark or featureless environment and the point will appear to move, even though it’s stationary. The second is the false horizon, which occurs when a pilot loses spatial orientation when the natural horizon (the reference point where land meets sky) is obscured or not readily apparent. Looking out at a distance, stars could be confused for city lights at night. And, if flying over the ocean or other large bodies of water, discerning between sky and water is nearly impossible. Pilots always have to interpret and discern the horizon despite dark terrain, confusing lights, or stars in the night sky.
A good visual scan and instrument scan can lessen the impact of these issues. In a good visual scan, the pilot will avoid focusing on any point or location for more than a few seconds. In a good instrument scan, the pilot will continually move his or her eyes from one instrument to another, especially instruments interpreting horizon, altitude, airspeed and heading, to keep good spatial awareness when visual clues are limited or may be confusing. Remember, the mechanical operation of an airplane at night is no different than operating the same airplane during the day. The airplane does not know if it is being operated in the dark or in bright sunlight. It performs and responds to control inputs by the pilot. The pilot, however, is affected by various aspects of night operations and must take them into consideration during night flight operations. Some are actual physical limitations affecting all pilots while others, such as equipment requirements, procedures, and emergency situations, must also be considered.
Until next time…safe travels.
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