Night Operations

Night Definitions

Night means the time between the end of evening civil twilight and the beginning of morning civil twilight, as published in the Air Almanac, converted to local time. This definition is used when logging flight time to meet the aeronautical experience requirements for a certificate or rating.

Regulations concerning aircraft lights reference the period from sunset to sunrise. In Alaska, the regulations use the period a prominent unlighted object cannot be seen from a distance of 3 SM or when the sun is more than 6° below the horizon.

Regulations concerning PIC requirements for carrying passengers reference the period beginning 1 hour after sunset and ending 1 hour before sunrise.

Civil Twilight

The NOAA defines civil twilight as "the time at which the sun is 6° below the horizon." The times The NOAA defines civil twilight as "the time at which the sun is 6° below the horizon." The corresponding times are published in the Air Almanac yearly by the United States Naval Observatory.

As a rule of thumb, civil twilight begins 30 minutes before sunrise. It ends at sunrise. In the evening, civil twilight generally ends 30 minutes after sunset. For official times, pilots should refer to the civil twilight tables in the Air Almanac that are appropriate to their latitude and date.

Link: https://www.usno.navy.mil/USNO (Naval Observatory website)

Night Operations

Adjustment to Light

Rods in the eyes take more time to adjust to changes in light than the cones. The eyes adapt to sunlight in 10 seconds, but at least 30 minutes is required for the rods to adjust to the dark fully. The adjustment of the eye to low light intensities is called dark adaptation.

Night Blind Spot

Due to the absence of rods in the fovea, a central blind spot is created at night. The blind spot exists in an area between 5° and 10° wide in the center of the visual field. Pilots can more clearly see an object at night by not looking directly at it but rather looking to one side.

Visual Scanning at Night

Visual search at night depends almost entirely on peripheral vision. The rods must be exposed to the image. To perceive a dimly lit object, the pilot should not look directly at the object but scan the area adjacent to it.

To scan effectively, pilots must look from right to left or left to right in sections that are approximately 30° wide. When moving from one viewing point to the next, pilots should overlap the previous field of view by 10°. Each section should be scanned for no longer than 2 to 3 seconds. These short pauses help detect light and its movement.

Cockpit Lighting

Cockpit lighting should be kept as low as possible so that the light does not deteriorate night vision. When it is necessary to read charts and checklists, pilots should use a dim white light and avoid shining it directly into the eyes. Red light can help preserve nighttime vision but makes red nearly invisible on aeronautical charts.

Position Lights

Airplane position lights provide a means to determine the general direction of movement of other airplanes in flight. A red light is positioned on the left wingtip, a green light on the right wingtip, and a white light on the tail.

When a red and green light of another aircraft is observed:

• If the red light is on the left and the green to the right, the airplane is flying in the same direction.
• If the red light is on the right and green to the left, the airplane could be on a collision course.

Operation of Aircraft Lights

During the period from sunset to sunrise, no person may:

• Operate an aircraft unless it has lighted position lights,
• Move an aircraft unless the aircraft:
• Is clearly illuminated;
• Has lighted position lights; or
• Is in an area that is marked by obstruction lights.

At any time, no person may:

• Operate an aircraft that is equipped with an anticollision light system unless it has lighted anticollision lights. However, the anticollision lights need not be lighted when the PIC determines that, because of operating conditions, it would be in the interest of safety to turn the lights off.

If an airplane is equipped with anticollison lights, they must be operational. The inoperative equipment provisions of 14 CFR 91.213 do not apply. However, 14 CFR 91.205 states that operations with the aircraft (day or night) may be continued to a stop where repairs or replacements can be made.

If an aircraft is equipped with both strobe lights and a rotating beacon, both are considered part of the anticollision system, and both must be operational.

Recommended Usage of Exterior Lighting

• Engines Running: Beacon ON
• Sunset to Sunrise: Position lights ON
• Taxi (While Moving): Taxi light ON
• Taxi (When Stopped or Yielding): Taxi light OFF
• Crossing a Runway: All exterior lights ON
• Line Up and Wait: Landing light OFF; All other exterior lights ON

• Takeoff and Landing: All exterior lights ON
• Climb and Descent: All exterior lights ON

Control of Airport Lighting

ATC controls airport lighting at towered airports. A pilot may request various light systems be turned on or off and also request a specified intensity, if available.

At nontowered airports, the lights may be on a day/night timer, or the pilot may control the lighting by radio. The lighting intensity can be changed by selecting a specified frequency and clicking the radio microphone. Lights typically remain on the selected intensity for 15 minutes.

VFR-Night Instruments and Equipment

For a night flight under VFR, the following instruments and equipment are required to be in an operable condition for civil aircraft with a Standard Airworthiness certificate. All of the instruments and equipment for a VFR-day flight are also required.

Mnemonic: FLAPS

• Fuses (one spare set of fuses, or three spare fuses for each kind required, that are accessible to the pilot in flight)
• Landing light (an electric landing light if the aircraft is operated for hire)
• Anticollision lighting system (approved aviation red or white)
• Position lights
• Source of electricity (an adequate source of electrical energy for all installed electrical and radio equipment)

Recent Flight Experience Requirements

Night Experience for Carrying Passengers

No person may act as PIC of an aircraft carrying passengers during the period beginning 1 hour after sunset and ending 1 hour before sunrise (as published in the American Air Almanac) unless, within the preceding 90 days, he or she has made at least 3 takeoffs and 3 landings to a full stop during that period in the category, class, and type (if a type rating is required) of aircraft to be used and acted as the sole manipulator of the controls.

Night Considerations for Navigation and Flight Planning [VFR]

• Airport beacons and city lights make good checkpoints. City lights correspond to the yellow outlines on VFR charts.
• Routes should be planned to keep the aircraft close to suitable airports for use in an emergency.
• Continuously monitor position, time estimates, and fuel consumed. Use NAVAIDs to assist in monitoring en route progress.

• A narrow temperature/dew point spread may indicate the possibility of fog.
• Personal minimums should be raised as an added safety margin.
• Identify areas that are below VFR weather minimums.
• Crossing large bodies of water at night is hazardous because the horizon may blend with the water.

Night Considerations for Preflight Inspections

• Ensure that the aircraft is equipped for night operations per 14 CFR 91.205.
• Carry at least two flashlights; a bright one for the preflight and a smaller one to use while flying.
• Parking ramps should be checked with a flashlight before entering the airplane.
• Inspect all interior and exterior lighting for proper operation. Tap the light fixtures to check for loose connections.

Night Considerations for Engine Starting

• Use extra caution to ensure the propeller area is clear.
• The position (navigation) lights should be turned ON after engine start.
• The anticollision lights are not required to be ON if the PIC determines that it would be in the interest of safety to leave them OFF.

Night Considerations for Taxiing

• Taxi slowly, particularly in congested areas.
• Use extra caution when entering or crossing a runway.
• Avoid using the strobe lights and bright, forward-facing lights around other aircraft.
• When stopped, use extra vigilance to ensure the airplane does not creep forward.

• Adjust the interior lights to a minimum brightness that allows reading the instruments and switches. Dimming the lights reduces reflections on the windows.

Night Considerations for Takeoffs

• Use extra vigilance when entering the runway. Approaching aircraft may not be equipped with or be using landing lights.
• Use caution for wildlife. Deer and other mammals are active at night.
• During the takeoff roll and immediately after liftoff, keep the runway lights parallel to the direction of motion.
• Cross-check the flight instruments after liftoff to help maintain the climb attitude.

• Do not turn until reaching a safe maneuvering altitude.

Night Considerations for Landings

• Distances and height can be deceptive. Use slope indicators to help maintain the approach angle.
• Check NOTAMS for unlit obstacles and runway closures.
• Beginning pilots tend to round out too high. The flare should begin when the landing lights reflect on the runway and tire marks can be seen clearly.

• When landing without a landing light, the flare should begin when the far-end runway edge lights appear to rise above the nose.
• Use caution for wildlife. Deer and other mammals are active at night.

Night Considerations for Go-Arounds

• A loss of control is more likely at night, where spatial disorientation is most likely. Cross-check the flight instruments to help maintain the climb attitude.
• Execute a go-around immediately if visual contact is lost with the landing runway. High terrain could be obstructing the view.

Night Considerations for Emergency Landings

If the engine fails at night, incorporate the following procedures:

• If the nearby terrain's condition is known and suitable for a forced landing, turn towards an unlighted portion of the area and plan an emergency forced landing to an unlighted portion.
• Turn the landing lights ON in time to illuminate the terrain or obstacles.
• If outside visual references are not available, maintain a level-landing attitude until the ground is contacted.

Illusions in Flight

Illusions in flight can related to the vestibular or visual systems. These illusions can lead to spatial disorientation, approach and landing mishaps, and errors in visual scanning and collision avoidance.

Visual Illusions Leading to Spatial Disorientation

False Horizon Illusion: Occurs when the pilot confuses cloud formations with the horizon or the ground. A sloping cloud deck may be perceived as horizontal, although it may not be level to the ground; thus, the pilot may fly the airplane in a banked attitude. The illusion may result in the pilot placing the airplane parallel to the clouds.

Relative-Motion Illusion: The falsely perceived self-motion in relation to the motion of another object.

Flicker Vertigo: While technically not an illusion, viewing a flickering light can be distracting. Flicker vertigo may be created by airplane propellers interrupting direct sunlight at a rate of 4–20 cycles per second. Flashing strobe lights, especially in the clouds, can also produce this effect.

Confusion with Ground Lights:

• Ground lights can be mistaken for stars. This illusion prompts the pilot to place the airplane in an unusual attitude to keep the lights above them.
• When no stars are visible because of overcast conditions, unlighted areas of terrain can blend with the sky.

Visual Illusions Related to Visual Scanning and Collision Avoidance

Autokinesis: Occurs at night when ambient visual cues are minimal, and a small, dim light is seen against a dark background. After 6–12 seconds of visually fixating on the light, one perceives movement at up to 20° in any particular direction or in several directions in succession, although there is no actual movement.

Size-Distance Illusion: When one stares at a point of light, it may appear to approach or recede rapidly. A change in the intensity of the light can cause this illusion. When a light gets suddenly brighter, it may appear much closer.

Reversible Perspective: At night, an aircraft may appear to be moving away from an observer when it is approaching. To eliminate this illusion, use the position lights and their relative arrangements to determine the aircraft's orientation and motion.

Visual Illusions Leading to Landing Errors

Runway Width Illusion: A narrower-than-usual runway can create the illusion that the airplane is too high. The pilot who does not recognize this illusion will fly a lower approach, risking impact with the ground short of the runway. A wider-than-usual runway has the opposite effect.

Runway and Terrain Slopes Illusion: An up-sloping runway can create the illusion that the airplane is higher than it is. The pilot who does not recognize this illusion will fly a lower approach. A down-sloping runway can have the opposite effect.

Featureless Terrain Illusion ("Black Hole Approach"): An absence of ground features can create the illusion that the airplane is at a higher altitude than it is. The pilot who does not recognize these illusions will fly a lower approach.

Atmospheric Illusions:

• Rain on the windshield can create the illusion of greater height, and atmospheric haze can create the illusion of being a greater distance from the runway. The pilot who does not recognize these illusions will fly a lower approach.
• Penetrating fog can create the illusion of pitching up. The pilot who does not recognize this illusion will abruptly steepen the descent.

Ground Lighting Illusions:

• Streetlights or other lights along a straight path can be mistaken for runway or approach lights.
• Bright runway lights may create the illusion of less distance to the runway. The pilot who does not recognize this illusion will fly a higher approach.

Best Practices for Preventing Landing Errors Due to Visual Illusions

• Anticipate visual illusions during approaches to unfamiliar airports, particularly at night or in adverse weather conditions.
• Consult airport diagrams and the Chart Supplement for information on runway slope, terrain, and lighting.
• Make frequent reference to the altimeter and vertical speed indicator.

• Use Visual Approach Slope Indicator (VASI) or Precision Approach Path Indicator (PAPI) systems for a visual reference, or an electronic glideslope, whenever they are available.
• Utilize the visual descent point (VDP) found on many nonprecision instrument approach procedure charts. [IFR]