Night Operations

The eye has two kinds of light-sensing cells. The Pilot's Handbook: "The cones are responsible for all color vision," and "the rods are better able to detect movement and provide vision in dim light. The rods are unable to discern color but are very sensitive at low-light levels" 1. Cones serve center vision, color, and detail, and they need light. Rods serve peripheral and dim-light vision, detect motion, and see no color.

The night blind spot

The center of the eye has no rods. The handbook: "There are so many cones in the fovea that are at the very center of the visual field but virtually has no rods at all. So in low light, the middle of the visual field is not very sensitive" 1. The Airplane Flying Handbook: "This absence of rods affects the central 5 to 10 degrees of the visual field. If an object is viewed directly at night, it may go undetected or it may fade away after initial detection" 2. A light that the pilot looks at directly at night can disappear from view.

Look to the side

Night scanning is off-center. The Pilot's Handbook: "To see an object clearly at night, the pilot must expose the rods to the image. This can be done by looking 5° to 10° off center of the object to be seen" 3. The night scan moves in stops: "For each stop, an area approximately 30° wide should be scanned," and each stop overlaps the last by 10 degrees 4. The pilot looks beside the traffic, not at it.

Thirty minutes to adapt

Full dark adaptation takes about 30 minutes. The Pilot's Handbook: "The rods can take approximately 30 minutes to fully adapt to darkness. A bright light, however, can completely destroy night adaptation, leaving night vision severely compromised while the adaptation process is repeated" 4. The AIM: "any degree of dark adaptation is lost within a few seconds of viewing a bright light, a pilot should close one eye when using a light to preserve some degree of night vision" 5. A pilot who views a bright light for a few seconds loses the 30 minutes of adaptation.

Preserving it

Four actions preserve dark adaptation. The pilot:

• dims the cockpit lights to the lowest level at which the pilot can read the instruments
• filters the flashlight, or dims it
• shields the eyes from strobes, landing lights, and lightning
• closes one eye when the pilot cannot avoid a bright light.

The Airplane Flying Handbook sets the limit at one second: the anticollision flashes "have a very short duration (less than 1 second)" and do not impair adaptation, but "if dark-adapted eyes are exposed to a bright light source (searchlights, landing lights, flares, etc.) for a period of 1 second or more, night vision is temporarily impaired" 2.

Red light and the chart

Red light preserves night vision and hides red and magenta print. The AIM: "Since red light severely distorts colors, especially on aeronautical charts, and can cause serious difficulty in focusing the eyes on objects inside the aircraft, its use is advisable only where optimum outside night vision capability is necessary. Even so, white cockpit lighting must be available when needed for map and instrument reading" 5. Red and magenta chart print fades under a red lamp. Dim white light is the compromise for chart reading.

Night vision is the first function that mild hypoxia degrades. The AIM: "Although a deterioration in night vision occurs at a cabin pressure altitude as low as 5,000 feet, other significant effects of altitude hypoxia usually do not occur in the normal healthy pilot below 12,000 feet" 6. The loss begins far below the altitude of the other hypoxia symptoms. The Pilot's Handbook gives a lower altitude: "Without supplemental oxygen, an individual's night vision declines measurably at pressure altitudes above 4,000 feet" 7. North Aero uses the AIM's number. Oxygen at night above 5,000 feet protects night vision, far below the altitude at which the oxygen regulation applies.

Four other causes

Carbon monoxide, smoking, fatigue, and low blood sugar each degrade night vision. The AIM: "Dark adaptation is impaired by exposure to cabin pressure altitudes above 5,000 feet, carbon monoxide inhaled in smoking and from exhaust fumes, deficiency of Vitamin A in the diet, and by prolonged exposure to bright sunlight" 5. The Pilot's Handbook adds fatigue and a missed meal: "Compounding the problem is fatigue, which minimizes physiological well being" 7, and "Missing or postponing meals can cause low blood sugar, which impairs night flight performance" 8. Carbon monoxide from a leaking exhaust enters through the "heater vents and defrost vents" 9, and it degrades night vision before the pilot notices any other symptom.

A lighted civil land airport beacon flashes white and green. The AIM's list: "White and Green− Lighted land airport," "White and Yellow− Lighted water airport," and "Green, Yellow, and White− Lighted heliport" 10. A military airport shows two quick white flashes between the green: "Military airport beacons flash alternately white and green, but are differentiated from civil beacons by dualpeaked (two quick) white flashes between the green flashes" 10.

The beacon by day

A beacon running by day in a surface area often means the weather is below basic VFR. The AIM: "operation of the airport beacon during the hours of daylight often indicates that the ground visibility is less than 3 miles and/or the ceiling is less than 1,000 feet," and "Pilots should not rely solely on the operation of the airport beacon to indicate if weather conditions are IFR or VFR" 11. A daytime beacon is not proof of IFR conditions and is not a substitute for a METAR.

Runway lights

Runway edge lights are white. From the approach the threshold shows green and the far end shows red. The AIM: "The runway edge lights are white," and "The lights marking the ends of the runway emit red light toward the runway to indicate the end of runway to a departing aircraft and emit green outward from the runway end to indicate the threshold to landing aircraft" 12. Green means the pavement begins. Red means the pavement ends.

Taxiway lights

Taxiway edge lights are blue, and centerline lights, where installed, are green. The AIM: "Taxiway edge lights are used to outline the edges of taxiways during periods of darkness or restricted visibility conditions. These fixtures emit blue light," and "Taxiway centerline lights are steady burning and emit green light" 13. Blue lights on both sides mark a taxiway. White lights on both sides mark a runway.

A two-bar VASI shows red over white on the glide path. The AIM: "Each light unit projects a beam of light having a white segment in the upper part of the beam and red segment in the lower part of the beam" 14. White over white is high. Red over red is low.

PAPI

A four-light PAPI shows two white and two red on the glide path. The AIM: the PAPI "uses light units similar to the VASI but are installed in a single row of either two or four light units. These lights are visible from about 5 miles during the day and up to 20 miles at night" 15. More white is high. More red is low. Four white is well above the path, and four red is well below it.

Keying the lights

The pilot keys pilot-controlled lighting on the frequency published for the airport, most often the CTAF. The AIM: "Suggested use is to always initially key the mike 7 times; this assures that all controlled lights are turned on to the maximum available intensity. If desired, adjustment can then be made, where the capability is provided, to a lower intensity (or the REIL turned off) by keying 5 and/or 3 times" 16. The lights turn off after a set time: "All lighting is illuminated for a period of 15 minutes from the most recent time of activation" 16. The pilot keys again on final, so that the lights do not go out in the flare.

Obstruction lights

Obstructions show red lights at night and white strobes by day or night. The AIM: "Flashing aviation red beacons (20 to 40 flashes per minute) and steady burning aviation red lights during nighttime operation," and "Medium intensity flashing white obstruction lights may be used during daytime and twilight with automatically selected reduced intensity for nighttime operation" 17. A lit tower's guy wires carry no lights. They extend far to the sides of the tower, and a pilot who clears the light by one wingspan can hit a wire.

Position lights are red on the left wingtip, green on the right, and white on the tail. The Airplane Flying Handbook: "A red light is positioned on the left wingtip, a green light on the right wingtip, and a white light on the tail" 18.

Sunset to sunrise

Position lights must be lighted from sunset to sunrise. Section 91.209(a) prohibits the following: "During the period from sunset to sunrise ... Operate an aircraft unless it has lighted position lights" 19. The AIM states that the rule applies on the ground: "Aircraft position lights are required to be lighted on aircraft operated on the surface and in flight from sunset to sunrise" 20. The same section covers the ground. No person may "Park or move an aircraft in, or in dangerous proximity to, a night flight operations area of an airport unless the aircraft" is clearly illuminated, has lighted position lights, or "is in an area that is marked by obstruction lights" 19.

Anticollision lights

Anticollision lights stay on for all operations, day and night. Section 91.209(b): a person must not "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 pilot-in-command determines that, because of operating conditions, it would be in the interest of safety to turn the lights off" 19. The AIM's cases: "Supplementary strobe lights should be turned off on the ground when they adversely affect ground personnel or other pilots, and in flight when there are adverse reflection from clouds" 20.

The night equipment list

Night VFR equipment is the day list plus five items. Section 91.205(c): "Instruments and equipment specified in paragraph (b) of this section," "Approved position lights," "An approved aviation red or aviation white anticollision light system," "If the aircraft is operated for hire, one electric landing light," "An adequate source of electrical energy for all installed electrical and radio equipment," and "One spare set of fuses, or three spare fuses of each kind required, that are accessible to the pilot in flight" 21.

The rule requires a landing light at night only when the flight is for hire 21. A private night flight without one is legal. Such a flight is still unwise, and North Aero does not dispatch one. The fuse requirement is specific: one spare set, or three spare fuses of each kind required, accessible to the pilot in flight.

Logged night time uses the civil twilight definition. Section 1.1: "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" 22. Civil twilight ends about 30 minutes after sunset. The night hours in the logbook and the night training of 61.109 use this definition 23.

The currency clock

Night currency uses a different definition of night. Section 61.57(b): "no person may act as pilot in command of an aircraft carrying persons during the period beginning 1 hour after sunset and ending 1 hour before sunrise, unless within the preceding 90 days that person has made at least three takeoffs and three landings to a full stop during the period beginning 1 hour after sunset and ending 1 hour before sunrise" 24. The landings count only if the person "acted as sole manipulator of the flight controls" and made them "in an aircraft of the same category, class, and type (if a class or type rating is required)" 24.

Three definitions, three clocks

The regulations define night three ways:

• civil twilight, for logging night time, from section 1.1
• sunset to sunrise, for the position lights, from section 91.209
• one hour after sunset to one hour before sunrise, for carrying persons, from section 61.57(b).

An exam question on night depends on which definition applies. A landing 20 minutes after sunset:

• requires the position lights on
• counts as a day landing for currency
• logs as night only if evening civil twilight has already ended.

Persons, not passengers

The recency rule says "carrying persons." Section 61.57(b) as written today: "carrying persons during the period beginning 1 hour after sunset" 24. Amendment 61-157, effective in November 2024, changed the word from "passengers," and older materials carry the old word.

Full stop

Day currency landings can be touch-and-go. Section 61.57(a) requires "at least three takeoffs and three landings within the preceding 90 days," with a full stop only for a tailwheel airplane 24. Night landings must be to a full stop. A night full-stop landing counts toward day currency too, because it is a landing within 90 days. A day landing never counts toward night currency. Three night full-stop landings satisfy both requirements.

Personal night equipment starts with two flashlights. The Airplane Flying Handbook: "At least one reliable flashlight is recommended as standard equipment on all night flights. A reliable incandescent or light-emitting diode (LED) dimmable flashlight able to produce white/red light is preferable," with "a spare set of batteries for the flashlight readily available. The white light is used while performing the preflight visual inspection of the airplane, the red light is used when performing flight deck operations, and the dim white light may be used for chart reading" 25. North Aero's list is two lights: white for the walk-around, red or dim for the cockpit, and spare batteries for both.

Organized before dark

The pilot organizes the night cockpit before dark. The handbook: "Once seated in the airplane and prior to starting the engine, a careful pilot will organize and arrange all items and materials to be used during the flight" 26. The list:

• charts out, and the EFB in night mode with its brightness down
• the frequencies for each leg staged
• the flashlight within reach of the seated pilot
• the checklists for each phase, including the emergencies.

The handbook on the EFB: "its brightness should be set so as not to seriously impair night vision" 25. Searching for gear in the dark is the typical night distraction.

Night pilotage uses lighted features. The Airplane Flying Handbook: "Rotating beacons at airports, lighted obstructions, lights of cities or towns, and lights from major highway traffic all provide excellent visual checkpoints" 27. Unlighted landmarks are not visible. A river, a ridge, and a section line do not appear at night. The nav log built in Module 2-1 names only the checkpoints that do.

Distance and height at night

Distances and heights are hard to judge at night. The handbook: "Distance may be deceptive at night due to limited lighting conditions. A lack of intervening references on the ground and the inability to compare the size and location of different ground objects cause this. This also applies to the estimation of altitude and speed. Consequently, more dependence should be placed on flight instruments, particularly the altimeter and the airspeed indicator" 28. The pilot takes obstacle and terrain clearance from the chart and the altimeter, not from the view outside.

The instruments corroborate

Over dark terrain the instruments supply the references that the window does not. The handbook: "The most noticeable difference between daylight and nighttime flying is the limited availability of outside visual references at night. Therefore, flight instruments should be used to a greater degree in controlling the airplane" 29. The pilot cross-checks the attitude indicator and the altimeter against the view outside for the whole leg. Module 1-8's skills apply at night, over each lake and each dark field.

Finding the airport

The pilot finds the airport at night by the beacon first and the runway lights second. The handbook: "A pilot should normally fly toward the rotating beacon until the lights outlining the runway are distinguishable. To fly a traffic pattern of proper size and direction, the runway threshold and runway-edge lights need to be positively identified. Once the airport lights are seen, these lights should be kept in sight throughout the approach" 28. The beacon is visible from far outside the airport, and the runway lights are a small rectangle among the lights of a city.

The lights going out

Ground lights that disappear along a line mean something is between the airplane and the lights. The handbook: "Usually, the first indication of flying into restricted visibility conditions is the gradual disappearance of lights on the ground. If the lights begin to appear surrounded by a halo or glow, further flight in the same direction calls for caution. Such a halo or glow around lights on the ground is indicative of ground fog" 30. A cloud, a ridge, or a fog bank is between the airplane and the lights. This sign is the first warning of night IMC or terrain, and the response is a turn back toward the lights that remain visible.

Night weather

At night the clouds are present and the pilot cannot see them. The handbook: "Generally, at night, it is difficult to see clouds and restrictions to visibility, particularly on dark nights or under an overcast," and "Pilots should avoid a VFR night flight if expecting conditions below VFR minimums" 30. The pilot relies on the METAR, the TAF, and the disappearing-lights check instead of on the view outside. North Aero's night personal minimums on the Personal Minimums Sheet are higher than the day minimums: more ceiling, more visibility, and no marginal VFR.

The flight of N6312G

On September 30, 2023, at 7:42 in the evening, a Cessna 150 spiraled into Lake Winnipesaukee from the traffic pattern at Laconia, New Hampshire. The pilot, a 70-year-old private pilot with 675 hours, died. He had no instrument rating, and his logbook back to 2020 showed "no logged flights at night, nor was there any simulated or actual instrument flight time logged" 31.

He was flying the airplane home from Providence, where he "had flown to PVD earlier in the month for a flight review, but due to weather, had not been able to return to New Hampshire" 31. That evening, "The pilot planned to land at LCI and have dinner with his girlfriend, who was waiting for him at LCI when the accident occurred." Before he left, "The pilot was advised by a flight instructor before departing on the accident flight that meteorological information indicated visibility might be diminished by the time he arrived at the destination airport, but he decided to depart anyway." The instructor said "the pilot had experienced multiple delays returning the accident airplane to his home and had plans with a friend that evening" 31.

He entered the right downwind for runway 26 on the 45. The runway lights were on. "The airplane continued on the downwind and after passing abeam the threshold of runway 26, the airplane continued 1.6 miles on a course about 66 degrees true (80 degrees magnetic). The airplane then crossed the shore of Lake Winnipesaukee and continued on the same course for an additional 0.4 nm," and began a left turn at 1,275 feet. "The moon was full, but the haze from wildfires diminished its illumination and it was dark over the lake" 31. A witness on the shore saw the landing lights pass: "The airplane was less than 100 ft above the water and was in a descending right turn" 31. The airport reported "visibility 5 statute miles in haze, clear skies" fourteen minutes after the accident 31.

The NTSB: "The pilot was not instrument-rated and had no recent experience flying at night. Witnesses indicated visibility in the area was reduced by wildfire smoke. Surveillance video confirmed that the sky was obscured and that the airplane was flying through low clouds immediately before the loss of control occurred. Few ground lights or other visual references were available in the vicinity of the lake that could have helped the pilot maintain orientation or aid in recovery after he lost control of the airplane" 31. The probable cause: "The pilot's loss of control during visual flight rules flight in night instrument meteorological conditions due to spatial disorientation. Contributing to the accident was the pilot's motivation to depart on the flight despite being made aware that conditions might be unsafe and his continuation of the flight as weather conditions deteriorated" 31.

Where the pilot could have prevented the accident

A 675-hour pilot with no night landing in three years extended his downwind over a dark lake in smoke. Each decision below carries the PAVE category that applied to it.

Night taxi is slower and needs more verification. The Airplane Flying Handbook: "Pilots should taxi slowly, particularly in congested areas. If taxi lines are painted on the ramp or taxiway, following the lines ensures a proper path along the route," and "While taxiing for any takeoff, the pilot should verify that the aircraft position, taxi route, and runway for the departure all appear as expected. The taxi diagram, signage, pavement markings, and instruments should all reinforce the pilot's situational awareness. If any conflicting information or doubt exists, the pilot should not proceed with the taxi or the takeoff" 26. The pilot uses the blue edge lights and the green centerline lights, keeps the taxi diagram out, and can request progressive taxi instructions.

The taxi light and the strobes

The taxi or landing light stays on whenever the airplane moves. The handbook: "After starting the engine and when ready to taxi, the pilot turns the taxi or landing light ON," and "When using lights, consideration should be given to not blinding other pilots" 26. When another airplane approaches head-on, the pilot switches the light off until that airplane passes. The strobes stay off during taxi, and the pilot turns them on when entering the runway. The AIM: "Supplementary strobe lights should be turned off on the ground when they adversely affect ground personnel or other pilots" 20, and AC 91-73B: "Strobe lights should not be illuminated if they will adversely affect the vision of other pilots" 32.

Hold short at night

Hold-short lines are harder to see at night. The AIM's holding position markings are "four yellow lines, two solid and two dashed," across the taxiway 33. At night the yellow paint is hard to see until the taxi light shines on it. The pilot verifies position against three things at once: the lighting, the signage, and the diagram. A pilot who is unsure stops and asks. The handbook's rule applies: in doubt, the pilot "should not proceed with the taxi or the takeoff" 26.

Another airplane's lights show which way it moves. The Airplane Flying Handbook: "This 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, and the red light is on the left and the green to the right, the airplane is flying the same direction. Care must be taken to maintain clearance. If red were on the right and green to the left, the airplane could be on a collision course" 18. The four cases:

• red and green together, with red on the right: it approaches you
• red alone: you face its left side, and it crosses from your right to your left
• green alone: you face its right side, and it crosses from your left to your right
• white alone: it moves away, or you overtake it.

The handbook adds the warning that "Aircraft lights may 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" 18.

Autokinesis is a single light that seems to move. The Airplane Flying Handbook: "In the dark, a stationary light will appear to move about when stared at for many seconds. The disoriented pilot could lose control of the aircraft in attempting to align it with the false movements of this light" 34. The remedy is to keep the eyes moving and never to stare at one light.

False horizon

A false horizon is a line that is not the horizon. The handbook: "A dark scene spread with ground lights and stars, and certain geometric patterns of ground lights can provide inaccurate visual information, making it difficult to align the aircraft correctly with the actual horizon. An aurora borealis display at night or a visible sloping cloud formation can also affect a pilot's sense of the horizon" 34. A sloping cloud deck, a lit shoreline, and a line of highway lights can each look like the horizon. The attitude indicator shows the true horizon.

The black hole

A black-hole approach is an approach to a lighted runway over dark, featureless terrain. The handbook: "A black-hole approach occurs when the landing is made from over water or non-lighted terrain where the runway lights are the only source of light. Without peripheral visual cues to help, orientation is difficult. The runway can seem out of position (down-sloping or up-sloping) and in the worst case, results in landing short of the runway. If an electronic glide slope or visual approach slope indicator (VASI) is available, it should be used" 35. The Pilot's Handbook names the result: the illusion "causes pilots to fly a lower approach" 36. The pilot flies the VASI or a computed descent, not the view outside.

The bright runway

Unusually bright runway lighting makes the runway seem closer than it is. The handbook: "Bright runway and approach lighting systems, especially where few lights illuminate the surrounding terrain, may create the illusion of being lower or having less distance to the runway. In this situation, the tendency is to fly a higher approach" 35. This illusion is the opposite of the black hole. One error is low and one is high, and the glide path lights correct both.

Roads that look like runways

Pilots mistake roads and lines of lights for runways at night. The handbook: "Lights along a straight path, such as a road or lights on moving trains, can be mistaken for runway and approach lights" 35. The beacon, the runway layout, and the traffic on the CTAF confirm the runway before the descent continues. A straight line of white lights with no green threshold at the end and no beacon beside it is a highway.

The landing light fails

A failed landing light in flight changes the flare technique. The handbook trains the blackout landing as an emergency procedure, and the approach itself stays normal. The handbook: "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. This demands a smooth and very timely round out and requires that the pilot feel for the runway surface using power and pitch changes," and "Blackout landings should always be included in night pilot training as an emergency procedure" 28. The approach is normal. The pilot times the flare from the runway-edge lights.

Night collision avoidance

Night collision avoidance uses a slower scan and the position-light pattern. The AIM's scan rule applies: "Each movement should not exceed 10 degrees, and each area should be observed for at least 1 second to enable detection" 37. At night the scan segments overlap, the eyes look beside each light, and position-light logic replaces silhouette recognition. There is no silhouette. There are a red, a green, and a white light, and their arrangement.

Night currency is the legal minimum. Night proficiency is the personal-minimums question, asked separately: recent night landings, this airplane, this airport. The Risk Management Handbook has pilots set minimums "more restrictive than the regulatory requirements" 38, and the Pilot's Handbook, under P, asks "Am I ready for this trip?" in terms of experience, recency, and currency 39. Three landings in 90 days is the rule. Three landings in the last month, at this field, in this airplane, is the North Aero number.

An inoperative position light

An inoperative position light after sunset grounds the flight unless the inoperative-equipment process clears it. Section 91.209 requires the lights 19, and section 91.205(c) lists them as required equipment for night VFR 21. Section 91.213(d) is the only relief, and it excludes equipment "Required by § 91.205 or any other rule of this part for the specific kind of flight operation being conducted" 40. A position light is required by 91.205(c) for night VFR, so the night flight cannot defer it. The airplane flies by day, or after the light is fixed. A light that worked in daylight does not justify a night dispatch.

The forced landing at night

The night forced-landing procedure has three parts:

• glide toward an airport, or away from congested areas
• configure early
• check the landing light at altitude and turn it on in time to light the terrain.

The handbook: "Maintain positive control of the airplane and establish the best glide configuration and airspeed. Turn the airplane towards an airport or away from congested areas" 41, and "Complete the before-landing checklist, and check the landing lights for operation at altitude and turn ON in sufficient time to illuminate the terrain or obstacles along the flightpath" 42. Darkness hides the surface until late in the descent, and the light must be on before that part. Module 1-15's engine-failure decisions apply unchanged. The field is harder to see.

Night fuel

The night fuel reserve at North Aero is larger than the 45-minute legal minimum. Section 91.151 requires fuel to the first point of intended landing plus 45 minutes at night 43. North Aero's night reserve is one hour, and the pilot plans fuel stops where fuel is available at the arrival time. The FBO's hours and the self-serve pump are in the Chart Supplement, which the Pilot's Handbook says carries "types of fuel available (use to decide on refueling stops)" 44. A fuel stop at a field whose pump is locked at 9 in the evening is not a fuel stop.