Night Operations

Two receptor types (PHAK ch. 17):

• Cones — concentrated in the fovea centralis at the center of the retina; responsible for color and fine detail in good light. In bright light rhodopsin is bleached out, making the rods less effective.
• Rods — out in the periphery; unable to discern color but very sensitive at low light levels and better at detecting movement.

The three viewing regimes: photopic (high light, central viewing, 20/20, cones), mesopic (medium/low light, both, acuity varies — described as the most dangerous period for viewing), and scotopic (low light, scanning required, no color, rods only, acuity 20/200 or less) (PHAK ch. 17).

The adjustment of the eye to a dark environment. Cones adapt rapidly; rods can take approximately 30 minutes to fully adapt to darkness, and a bright light can completely destroy night adaptation (PHAK ch. 17). Moving from a bright room into a dark one takes longer than moving from a dim room.

Practical instruction: dim the flight deck lighting, use a red or low-intensity white flashlight for chart reading, avoid looking at strobes or landing lights, and start the dark adaptation clock before you need the vision, not after.

Under scotopic vision, a night blind spot appears in the central field of view as cone sensitivity is lost (PHAK ch. 17) — so looking directly at a dim object makes it disappear.

The technique is off-center viewing: look 10° above, below, or to either side of the object so peripheral rod vision maintains contact. The catch: an image viewed off-center for longer than 2 to 3 seconds will disappear, because the rods reach a photochemical equilibrium that prevents further response until the scene changes (PHAK ch. 17). So the scan must keep moving — this is a technique students must practice, not just hear.

Beacons help identify an airport at night and are normally operated dusk until dawn. The beacon has a vertical light distribution most effective from 1–10° above the horizon (PHAK ch. 14):

• Flashing white and green — civilian land airport
• Flashing white and yellow — water airport
• Flashing white, yellow, and green — heliport
• Two quick white flashes alternating with green — military airport

Teaching trap worth naming: beacons are sometimes turned on when the ceiling is less than 1,000 feet and/or ground visibility is less than 3 statute miles, but there is no requirement for this, so the pilot retains the responsibility for determining whether the weather meets VFR requirements (PHAK ch. 14).

• Runway edge lights — HIRL, MIRL, and LIRL outline the runway edges; HIRL and MIRL have variable intensity. They are white, except on instrument runways where amber is used on the last 2,000 feet or half the runway length, whichever is less. The lights marking the end of the runway are red (PHAK ch. 14).
• Runway centerline lighting system (RCLS) — spaced at 50-foot intervals; viewed from the landing threshold, white until the last 3,000 feet, then alternating white and red for 2,000 feet, then all red for the last 1,000 feet (PHAK ch. 14).
• Touchdown zone lights (TDZL) — two rows of transverse bars symmetric about the centerline, steady-burning white, starting 100 feet beyond the threshold and extending to 3,000 feet beyond the threshold or the runway midpoint, whichever is less (PHAK ch. 14).
• REIL — runway end identifier lights, installed at many airports to identify the approach end.

• Taxiway edge lights — omnidirectional, blue; many have variable intensity adjustable by ATC or on pilot request. Some airports have green taxiway centerline lights (PHAK ch. 14).
• Clearance bar lights — three in-pavement steady-burning yellow lights at holding positions, to increase conspicuity in low visibility or to mark an intersecting taxiway at night.
• Runway guard lights — at taxiway/runway intersections; either a pair of elevated flashing yellow lights on each side of the taxiway, or a row of in-pavement yellow lights across the taxiway at the runway holding position marking.
• Stop bar lights — a row of red in-pavement lights across the taxiway at the holding position with elevated red lights on each side, used to confirm an ATC clearance; operated with the taxiway centerline lead-on lights, which turn on when the stop bar turns off.
• Taxiway centerline lead-off / lead-on lights — alternating green and yellow, beginning with green, from the runway centerline to one light position beyond the runway holding position or ILS critical area holding position (PHAK ch. 14).

At selected nontowered airports the pilot controls the lighting by selecting a specified frequency and clicking the microphone (PHAK ch. 14):

• 7 clicks within 5 seconds — highest intensity available
• 5 clicks within 5 seconds — medium or lower intensity (lower REIL or REIL off)
• 3 clicks within 5 seconds — lowest intensity available (lower REIL or REIL off)

Refer to the Chart Supplement for PCL information at a specific airport. At towered airports lighting is controlled by ATC; at nontowered fields it may be on a timer, or controlled by FSS personnel where an FSS is on the field.

Teaching technique: always key 7 clicks first, even if you want low intensity — it guarantees the system is on and gives you the brightest picture while you are still far out. Then step down.

• Red obstruction lights — flashing or steady red at night; the obstruction is painted orange and white for daytime
• High intensity white obstruction lights — flashing high intensity white by day, reduced intensity at night
• Dual lighting — flashing red beacons and steady red lights at night, high intensity white by day

(PHAK ch. 14.)

From sunset to sunrise (in Alaska, when a prominent unlighted object cannot be seen from 3 SM or the sun is more than 6° below the horizon), no person may do the following without lights (91.209(a)):

• Operate an aircraft unless it has lighted position lights
• Park or move it in or near a night flight operations area unless it is clearly illuminated, has lighted position lights, or is in an area marked by obstruction lights
• Anchor it without anchor lights, or in an area where anchor lights are not required for vessels

Separately, no person may operate an aircraft equipped with an anticollision light system unless the anticollision lights are lighted — however, they need not be lighted when the PIC determines that, because of operating conditions, it is in the interest of safety to turn them off (91.209(b)).

Note the mismatch worth teaching: 91.209 uses sunset to sunrise, while night currency under 61.57(b) uses 1 hour after sunset to 1 hour before sunrise. Three different "nights" exist in the regulations, and students conflate them.

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 unless, within the preceding 90 days, that person made at least three takeoffs and three landings to a full stop during that same period, acting as sole manipulator of the controls, in an aircraft of the same category, class, and type (if a class or type rating is required).

The takeoffs and landings may be accomplished in an approved full flight simulator with the visual system adjusted to represent that period, used under an approved part 142 course (61.57(b)(2)).

Currency is the legal minimum: three full-stop landings in 90 days. Proficiency is whether you can actually fly a black-hole approach into an unlit field, interpret an unfamiliar runway's lighting, and hand-fly on instruments if the horizon disappears.

The teaching move is to make the gap concrete for the student: ask when their last night landing was, at which airport, and in what conditions. Three tower-lit full-stops at the home field on one evening satisfy 61.57(b) for 90 days and prepare nobody for a moonless cross-country. Personal minimums for night should be separate numbers, not the daytime ones.

Airplane position lights are arranged like a boat's: a red light on the left wingtip, a green light on the right wingtip, and a white light on the tail (AFH ch. 11). The arrangement tells you the other airplane's direction of movement: red on the left and green on the right means it is flying the same direction as you, so you maintain clearance; red on the right and green on the left means it could be on a collision course (AFH ch. 11).

Seeing only the white tail light means you are behind and overtaking — and the aircraft being overtaken has the right-of-way, so the overtaking pilot must alter course to the right to pass well clear (91.113(f)).

Combine this with the no-relative-motion cue from Task II.B: lights that stay in the same place on the windshield and get brighter are the ones that matter. And remind the student that aircraft lights may blend in with stars or city lights and go unnoticed without a conscious effort to distinguish them (AFH ch. 11).

• Two flashlights, one of them small enough to hold in the mouth or clip to a headset, plus spare batteries — the second one is the point
• A red or dimmable white light for chart reading, to protect dark adaptation (PHAK ch. 17)
• Current charts and Chart Supplement — you cannot browse a torn chart with one hand at night, and PCL frequencies come from the Chart Supplement (PHAK ch. 14)
• Clear glasses, not sunglasses; anything that reduces light reduces detection
• Cold weather gear appropriate for an off-airport landing on the route you are flying

Make the student assemble the kit and show it to you at the preflight briefing. A list recited is not a flashlight in the airplane.

Use demonstration-performance (AIH ch. 9), and front-load everything that is different:

1. Preflight in daylight if possible, or with the student's own flashlight, so the walkaround is a real inspection rather than a ritual.
2. Taxi first. Night taxi operations (AI.II.M.K8) get their own segment: blue edge lights, yellow clearance bars and runway guard lights, red stop bars, and the fact that hold-line geometry that is obvious by day is nearly invisible at night (PHAK ch. 14). Runway incursion is an explicit night risk element (AI.II.M.R6).
3. Traffic pattern work at the home field first, so the sight picture is being learned against a known runway.
4. Then the departure from the pattern, orientation and navigation, and the return.

For a student who will solo at night, that pattern work at the specific airport where the solo will be conducted is not optional — 61.87(o)(1) requires night training in takeoffs, approaches, landings, and go-arounds at that airport, plus night navigation training in its vicinity.

• Featureless terrain ("black hole") illusion — an absence of surrounding ground features, as in an overwater approach over darkened areas or terrain made featureless by snow, creates the illusion that the aircraft is higher than it actually is, causing the pilot to fly a lower approach than desired (PHAK ch. 17). Countermeasure: use the VASI or PAPI and the altimeter as primary, not the sight picture.
• Haze — creates the illusion of being at a greater distance and height from the runway, so the pilot tends to be low on the approach; extremely clear air has the opposite effect (PHAK ch. 17).
• Runway width and slope illusions — a narrower-than-usual or upsloping runway makes you feel high, driving you low; wider or downsloping makes you feel low, driving you high. Amplified at night because the runway lights are all you have.
• Autokinesis — a single static light stared at will appear to move. Countermeasure: keep the eyes scanning; do not stare at one light.
• False horizon — a sloping cloud deck, a shoreline, or a line of ground lights mistaken for the horizon.
• Featureless terrain — no texture means no height cue.

Teaching method: brief the illusion, then set it up deliberately and let the student experience it with you guarding the controls. Experience plus explanation beats explanation alone (AIH ch. 2).

Integrated flight instruction pays off at night. The daytime split is roughly 90 percent outside with instruments validating attitude and performance (AFH ch. 3); at night, when the outside references thin out, the instruments become the arbiter — but the student must already have the habit of cross-checking them, or they will not start now.

Concrete techniques to teach:

• Confirm the attitude indicator against the visible horizon while it is still visible, so a discrepancy is obvious later
• Fly the departure and the pattern with the altimeter and VSI as active instruments, not decorations
• On final, cross-check the VASI/PAPI against altitude and distance rather than trusting the picture
• If the horizon disappears, transition fully to instruments and say so out loud

You cannot see what you are flying into. Clouds, precipitation shafts, and lowering ceilings are invisible until you are in them; the first cue is often ground lights disappearing or a halo around them. Fog and radiation cooling favor the overnight hours, so a field that was VFR at departure can be below minimums by the return.

Teach a hard rule set rather than judgment calls: know the freezing level and the dew point spread, pick alternates with weather reporting and lighting, and treat a disappearing ground-light picture as an immediate turn-around trigger.

Two layers. First, 91.205(c) adds night equipment requirements to the daytime list, and 91.213 governs operating with inoperative instruments and equipment. Second, and more practically: the landing light that works on the ramp and fails on short final, the panel light that dies, and the flashlight with the flat battery are all single-point failures with no daytime equivalent.

Instructor practice: brief the failure before it happens. "If the landing light quits, we continue the approach normally and land — the light is a convenience, not a requirement." A student who has heard that sentence does not go around from 10 feet in the dark.

Traffic is reduced to point sources, so the relative-motion cue from Task II.B is all you have, and the scan technique changes — off-center viewing, moving every 2 to 3 seconds, because a dim target stared at will disappear (PHAK ch. 17). Add the central night blind spot and reduced acuity (20/200 or less under scotopic conditions), and detection range collapses.

Countermeasures to teach:

• Anticollision and landing lights on — landing lights are encouraged within 10 miles of an airport and below 10,000 feet, day or night and in reduced visibility, and in areas where flocks of birds may be expected (AFH ch. 11)
• ADS-B In in the scan, with its limitations understood (PHAK ch. 14)
• Position reporting at nontowered fields