Chapter 10: Night Operations
Night operations present additional risks, which must be identified and assessed. Night flying operations should only be undertaken by pilots who are current and proficient in night flying.
Night flying requires an understanding of the physical limitations that affect all pilots. Equipment requirements, procedures, and emergency situations must also be considered.
Per the regulations, "night" is defined as the time between the end of evening civil twilight and the beginning of morning civil twilight (14 CFR 1.1, "Definitions and Abbreviations"). Morning civil twilight begins when the geometric center of the sun is 6° below the horizon, ending at sunrise. Evening civil twilight begins at sunset, ending when the geometric center of the sun reaches 6° below the horizon.
For flight operations, "night" refers to the time period starting one (1) hour after sunset and ending one (1) hour before sunrise (14 CFR part 61). No person may act as pilot in command (PIC) of an aircraft carrying passengers, within the preceding 90 days, unless that person has made at least three takeoffs and three landings to a full stop during this night period.
During the period from sunset to sunrise, operating aircraft are required to have a functioning anti-collision light system, including a flashing or rotating beacon and position lights.
Due to the physiology of the human eye, sight is limited in low light conditions, such as at night.
Light-sensitive nerves are located at the back of the eye or retina, which is a layer upon which all images are focused. These nerves connect to the optic nerve, which transmits messages directly to the brain.
There are two types of light-sensitive nerves within the retina: Cones and rods.
Cones are located in the center of the retina. Their function is to detect color, details, and faraway objects.
Rods are concentrated in a ring around the cones. They function when something is seen in peripheral vision. Rods detect objects — particularly those that are moving — but they do not transmit details or color information.
Both the cones and the rods are used for vision during daylight and moonlight. In the absence of normal light, the process of night vision is placed almost entirely on the rods, which make night vision possible.
The rods do not lie directly behind the pupils. Instead, they are distributed in a band around the cones. Because of this, off-center viewing (looking to one side of an object) important during night flight.
During daylight, an object can be seen best by looking directly at it. At night, there is a night blind spot in the center of the field of vision. Any object is in this area may not be perceived by the optic nerve.
The size of the night blind spot increases as the distance between the eye and the object increases. Because of this, large distant objects may not be perceived. During night operations, pilots should scan using an off-center technique, rather than looking directly at objects. Pilots also should move their eyes more slowly than they would in daylight conditions. If night vision becomes blurred, try blinking several times.
When you enter a dark room, you will find that it's difficult to see anything for a period of time. Gradually, vision improves. This is called dark adaptation.
During the dark adaptation process, the pupils immediately enlarge to receive as much available light as possible. Within five to ten minutes, the cones adjust to the limited amount of light. After this, the eyes are approximately 100 times more sensitive to light than they were before the dark room was entered.
It takes about about 30 minutes for the rods to adjust to darkness. After this period of adjustment, they are about 100,000 times more sensitive to light than they were in the lighted area. When dark adaptation is complete, the human eyes can perceive large amounts of visual information, particularly with off-center viewing.
Dark adaptation rapidly reverses when the viewer is exposed to a light source. Any immediate, bright light will cause temporary blindness. However, the eyes will adjust after a few moments, after which all dark adaptation is lost. Restoring the full potential of night vision will require darkness and another 30 minutes of adjustment.
Pilots must undergo the dark adaptation process before night flight. This begins by utilizing the appropriate time to become fully adapted, and setting aside extra time in a dark environment, if necessary.
Pilots also must protect their night vision by avoiding exposure to any bright light source. Landing lights are an example of bright lighting in a nighttime airport environment. Because each eye adapts to the dark independently, closing or covering one eye when exposed to light will retain some night vision acuity in the closed eye.
When night vision is impacted by unusually bright light, the result can be temporary blindess, illusions, or after-images. In flight, this can result in mistaking slanted clouds for the horizon, or believing that a populated area is an airport. Recognizing that the brain and eyes can play tricks in this manner is the best protection for flying at night. Illusions can affect pilots at every level of experience and skill.
Do not wear sunglasses after sunset as this impairs night vision.
Night vision also can be impacted by fatigue, colds, vitamin deficiency, alcohol, stimulants, smoking, or medication.
If oxygen is available, use it during night flying. Keep in mind that night vision can deteriorate at cabin altitudes as low as 5,000 feet.
Night illusions can cause confusion and distractions during night operations.
Visual autokinesis is a visual illusion that causes stationary lights to appear to be in motion. This can occur when staring at a single light source for several seconds.
The autokinesis effect will not occur if the visual field is expanded through scanning techniques, which reduces the probability of vision becoming fixed on one source of light.
Flicker vertigo can lead to physical reactions, such as nausea, dizziness, grogginess, unconsciousness, headaches, or confusion. It can be caused by a flickering light in the flightdeck, anti-collision light, or other aircraft lights. Light sources on the flight deck that can induce flicker vertigo should be eliminated.
A black-hole approach creates disorientation. It can be caused when the runway lights are the only source of light, such as when landing from over water or non-lighted terrain. A black-hole approach can make the runway can seem out of position, with either a down-sloping or up-sloping aspect. Landing short is possible.
Pilots may think that they are too low or have less distance to the runway if it has bright runway and approach lighting systems, especially where few lights illuminate the surrounding terrain. In this situation, the tendency is to fly a higher-than-normal approach.
Flying over terrain with only a few lights makes the runway recede or appear farther away. In this situation, the tendency is to fly a lower-than-normal approach.
If a runway has a city in the distance on higher terrain, the tendency is to fly a lower-than-normal approach.
Bright lights or bold colors advance the runway, making it appear closer than it actually is. The tendency is to fly a lower-than-normal approach.
When a double row of approach lights joins the boundary lights of the runway, there can be confusion where the approach lights terminate and runway lights begin. And under certain conditions, approach lights can make the aircraft seem higher in a turn from base to final, compared to when its wings are level.
When landing at night, pilots should rely on visual landing aids such as a VASI or PAPI. An electronic glideslope also should be utilized, if the aircraft is equipped with one and the airport has an ILS approach to the landing runway.
When landing at night, if either the runway or altitude is in doubt, execute a go-around.
A reliable white flashlight is recommended for night operations, to be used during the preflight visual inspection. This light also will be useful in case of emergencies, such as an off-airport landing or other unexpected scenarios.
A light-emitting diode (LED) flashlight or penlight that produces red or blue light is ideal for cockpit use. The red or blue light will not interfere with night vision, while a white light will disrupt night adaptation. This light can be used for reading checklists and charts, and it's commonly worn on a lanyard around the pilot's neck. Note that any chart details in red/blue ink will not be legible under a red/blue light.
The pilot should add at least one spare flashlight of each type, as well as new batteries, in his/her flight bag.
The lights of cities, towns, and radio towers can be seen at surprising distances at night. Be certain to carry adjacent sectional charts if you may need to identify lights from cities that are not depicted on your local sectional.
Airplane Equipment and Lighting
The standard instruments for instrument flight are a valuable asset for aircraft control at night. These instruments are noted in 14 CFR part 91.
During the period from sunset to sunrise operating aircraft are required to have a functioning anti-collision light system, including a flashing or rotating beacon and position lights. .
The anti-collision lights need not be lighted when the pilot in command (PIC) determines that, because of operating conditions, it would be in the interest of safety to turn the lights off.
Airplane position lights are arranged similar to those of boats and ships. A red light (port) is positioned on the left wingtip, a green light (starboard) on the right wingtip, and a white light on the tail (aft).
The color and arrangement provides a means to determine the general direction of movement of other airplanes in flight. If both a red and green light of another aircraft are observed ahead, with the red light is on the left (port) and the green to the right (starboard), the airplane is flying the same direction. If the lights are in the opposite positions, the airplane is closing distance and could be on a collision course.
During night operations, pilots are encouraged to turn on their landing lights when operating within 10 miles of an airport and below 10,000 feet.
Pilots should not be complacent when visually scanning for other aircraft at night. Most aircraft lights blend in with the stars or the lights of the cities at night and go unnoticed unless a conscious effort is made to distinguish them from other lights.
Airport and Navigation Lighting Aids
Airports located near or within large cities are often difficult to identify at night, as the airport lights tend to blend with the city lights. During night operations, it is important not to only know the exact location of an airport relative to the city, but also to be able to identify these airports by the characteristics of their lighting pattern.
Most airports have rotating beacons, which produce a series of light flashes at regular intervals. The beacon's colors identify various types of landing areas.
Other lights include:
Runway lighting system
Runway edge lights are white, in two straight parallel lines that define the lateral limits of the runway. Yellow lights may be installed for a distance of 2,000 feet from the far end of the runway, indicating a caution zone.
Some airports have pilot-controlled lighting, which permits the activation of runway edge lights via the radio. A one-step system permits the activation of runway edge lights when the aircraft's radio is tuned to the Common Traffic Advisory Frequency (CTAF) and the pilot keys ("clicks") the push-to-talk button three times in succession. Lighting is illuminated for a period of 15 minutes from the most recent time of activation and may not be extinguished prior to the end of the 15-minute period.
The three-step system and two-step system permit the intensity of the runway lights to be controlled by pilots.
With a three-step system, seven clicks activates the runway lights at their highest intensity, while five clicks activates the lights at medium intensity, and three clicks at low intensity.
With a two-step system, medium intensity is not available. Five clicks activates the lights at their highest intensity, with three clicks for low intensity.
Pilots are encouraged to activate the runway lights at their highest available intensity, and then to lower the intensity if desired.
Due to the close proximity of general aviation airports using the same CTAF, radio-controlled lighting receivers may be set at a low sensitivity. This will require aircraft to be relatively nearby to activate the system. Pilots should note the 15-minute duration of pilot-activated lights and not activate them until they are certain they will be on the ground within that time period.
Green runway threshold lights mark the approach end of the runway. Red runway end lights mark the far limit of the runway.
Blue taxiway edge lights outline the usable limits of taxi paths.
Training for Night Flight
Learning to safely fly at night requires time and experience. Pilots should practice straight-and-level flight, climbs and descents, level turns, climbing and descending turns, and steep turns. Practicing recovery from unusual attitudes should only be done with a flight instructor.
Pilots can practice "blackout" maneuvers with all the flight-deck lights turned off to simulate an electrical or instrument light failure.
In spite of fewer references or checkpoints, night cross-country flights do not present particular problems if pre-planning is adequate. Navigational aids, if available, will help monitor the flight's progress.
Preparation and Preflight
Preparation for a night flight includes a thorough review of the available weather reports and forecasts with particular attention given to temperature/dew point spread. A narrow temperature/dew point spread may indicate the possibility of fog, which would prohibit landing in visual conditions.
Note prominently lighted checkpoints along the prepared course. Rotating beacons at airports, lighted obstructions, lights of cities or towns, and lights from major highway traffic all provide excellent visual checkpoints.
Parking ramps should be checked with a flashlight prior to entering the airplane to ensure that items and debris easily seen during the day are not overlooked.
Starting, Taxiing, and Runup
After starting the engine and when ready to taxi, turn the taxi or landing light on. Because the airplane taxis at low RPM, the landing light may create a drain on the battery. This should be monitored. Overheating of an incandescent landing light also is possible when the aircraft is stationary or taxiing.
Be certain to taxi with the aircraft centered on any taxi lines that are painted on the ramp or taxiway.
During the run-up checklist, be alert for any forward movement, which is less obvious at night than during the day.
Takeoff and Climb
The procedure for night takeoffs is the same as for normal daytime takeoffs except that many of the runway visual cues are not available.
Check the flight instruments frequently during the takeoff to ensure the proper pitch attitude, heading, and airspeed are being attained. Refer to both outside visual references, such as lights, and to the flight instruments.
After becoming airborne, the darkness of night often makes it difficult to sense the airplane's relationship with the surface. To ensure the airplane continues in a positive climb, be sure a climb is indicated on the attitude indicator, vertical speed indicator (VSI), and altimeter. Maintain best-rate-of-climb speed (Vy).
Turns should not be made until reaching a safe maneuvering altitude.
The landing light can cause distortion when it is reflected by haze, smoke, or clouds that might exist in the climb. The pilot may want to turn off the landing light in these conditions. However, it is recommended that the landing light remain in use for collision avoidance when operating below 10,000 feet. Therefore, the landing light should be re-activated if smoke, haze, and clouds are no longer a factor.
Orientation and Navigation
Under no circumstances should a VFR night flight be made during poor or marginal weather conditions unless both the pilot and aircraft are certificated and equipped for flight under instrument flight rules (IFR).
When flying at night under visual flight rules (VFR), pilots must exercise caution to avoid flying into clouds, which can be difficult to see in the dark. Typically, the first indication of flying into restricted visibility conditions is the gradual disappearance of lights on the ground.
If lights on the ground begin to take on an appearance of being surrounded by a halo or glow, use caution in attempting further flight in that same direction. Such a halo or glow around lights on the ground is indicative of ground fog.
Crossing large bodies of water at night in single-engine airplanes could be potentially hazardous. During poor visibility conditions over water, the horizon becomes obscure and may result in a loss of orientation. On clear nights, the stars may be reflected on the water surface, which could appear as a continuous array of lights, thus leading to a loss of the horizon for visual reference. Unprepared pilots, and those without proper instrument training, may experience a loss of control that could be catastrophic.
Approaches and Landings
When approaching the airport to enter the traffic pattern and land, it is important that the runway lights and other airport lighting be identified as early as possible.
Fly toward the rotating beacon until the lights outlining the runway are distinguishable.
The runway threshold and runway-edge lights must be positively identified in order to fly a traffic pattern of proper size and direction. Once these lights are seen, they should be kept in sight throughout the approach.
Deceptive perceptions of distance can be created by the lack of intervening references on the ground, as well as the inability to compare the size and location of different ground objects. Therefore, more dependence must be placed on flight instruments, particularly the altimeter and the airspeed indicator.
At night, the judgment of height, speed, and sink rate during landing is impaired by the scarcity of observable objects in the landing area. Inexperienced pilots tend to round out too high until attaining familiarity with the proper height for the correct round-out.
To aid in determining the proper round-out point at night, continue a constant approach descent until the landing lights reflect on the runway and tire marks on the runway can be seen clearly.
Blackout landings should always be included in night pilot training as an emergency procedure. During landings without the use of landing lights, the round out may be started when the runway lights at the far end of the runway first appear to be rising higher than the nose of the airplane.
The greatest concern regarding night operations in a single-engine airplane is the possibility of a complete engine failure and the subsequent emergency landing. While this is legitimate, continuing flight into adverse weather and poor pilot judgment account for most serious night accidents.
In the event of an engine failure, the emergency checklist should be followed. This checklist does not change for night operations.
Consider an emergency landing area close to public access if possible. This may facilitate rescue or help, if needed.
If the condition of the nearby terrain is known and is suitable for a forced landing, turn towards an unlighted portion of the area and plan an emergency forced landing to an unlighted portion.
If the landing lights are unusable and outside visual references are not available, the airplane should be held in level-landing attitude until the ground is contacted.
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