16.4 Communications, Light-Gun Signals, Lighting, and Traffic Patterns

ACS PA.III.A is communications, light signals, and runway lighting. PA.III.B is traffic patterns at towered and nontowered airports. AIM 4-1-9, 4-3, 2-1, and 14 CFR 91.125 / 91.126 are the exam pages. Lost-comm IFR (91.185) is not the private-pilot VFR answer; VFR lost comm is stay visual, land as soon as practicable, and use this section’s light gun.

Who you are talking to

CTAF (common traffic advisory frequency) is the frequency designated for airport advisory practices when there is no operating control tower. AIM 4-1-9: it may be a UNICOM, MULTICOM, FSS, or the tower frequency itself. Read the sectional data block and the Chart Supplement; do not guess 122.8 for every grass strip.

• UNICOM is a nongovernment advisory station — fuel, wind if someone answers, not ATC separation. Common UNICOM CTAFs include 122.7, 122.8, 122.725, 122.975, and 123.0. If no one answers, self-announce on the same frequency.
• MULTICOM 122.9 is the self-announce frequency when there is no tower, FSS, or UNICOM.
• Tower owns the Class D (or C/B) surface area while open. Initial call about 15 miles out (AIM 4-3-2), with ATIS. Ground owns the movement area except the runway; do not taxi onto a runway without the local controller. When the tower is closed, the CTAF is usually the tower frequency and the airspace often reverts — confirm the Chart Supplement.
• ATIS is the recorded tower-airport briefing (weather, duty runway, NOTAMs). ASOS/AWOS are automated weather. Get one-minute weather before you call, and say you have it.

AIM 4-1-9 recommended calls at a field without an operating tower: before taxi, before taking the runway, 10 miles out, entering downwind, base, and final, and clear of the runway. Phraseology is position and intention, not a novel: “Podunk traffic, Skyhawk 345, 10 south, inbound for left downwind 27, Podunk.”

Patterns — left unless marked

14 CFR 91.126 / 91.127: at nontowered airports, make all turns to the left unless the airport displays approved light signals or visual markings indicating right turns, or ATC says otherwise. AIM 4-3-3: RP plus a runway number in the data block means right traffic for that runway. The segmented circle and its L-shaped traffic-pattern indicators show the same thing on the ground. A tetrahedron, if installed, shows landing direction (small end points the way you land); do not use it as a wind sock.

AIM 4-3-3 recommended pattern altitudes unless the Chart Supplement publishes another TPA: propeller-driven airplanes 1,000 feet AGL; large/turbine not less than 1,500 feet AGL or 500 above the established TPA. AC 90-66C and AIM figures: the standard recommended entry is a 45° entry to the downwind, at pattern altitude, abeam midfield. Straight-in and midfield-crosswind entries exist; they are not an excuse to cut off someone already on downwind. At a towered field, fly what the tower assigns — “make right traffic, report midfield” wins over the RP note.

Pattern parts (AIM 4-3-2): departure / upwind, crosswind, downwind, base, final. Wind correction on downwind is the same ground-reference skill as Chapter 10: crab so the ground track is parallel to the runway. 91.113: the lower aircraft on approach has the right-of-way, but do not cut in front of someone already on final.

Light-gun signals — exact (91.125 / AIM TBL 4-3-1)

If the radio fails in the pattern at a tower, squawk 7600, enter the pattern, and watch the tower. AIM 4-3-13: by day, acknowledge by moving the ailerons or rudder; at night, flash the landing or navigation lights.

Memorize the flashing-red trap. In the air, flashing red is airport unsafe, do not land — go somewhere else. On the ground, flashing red is taxi clear of the runway. Steady red in the air is not “go away”; it is give way and keep circling until you get a green. Flashing white does nothing for an airplane in flight. Alternating red/green is caution in both states; it is not a clearance and not a wave-off by itself.

Lighting, PCL, beacons

VASI and PAPI both use red/white glide-path cues. Memory that matches AIM 2-1-2: red over white, you’re all right. Two-bar VASI: both white = too high; both red = too low. PAPI (usually four lights): two white / two red on path; more white = high; more red = low. REIL are the two synchronized flashing lights at the threshold that say “this is the runway.” ALS is the approach lighting system off the arrival end. Runway edge lights are white (often amber on the last 2,000 feet, or last half, of some runways); threshold appears green when landing, runway end red. Taxiway edge lights are blue; taxiway centerline lights are green.

Pilot-controlled lighting (PCL) is keyed on the CTAF or a published lighting frequency. AIM 2-1-8 typical intensity steps: 3, 5, or 7 microphone clicks within 5 seconds for low / medium / high (confirm the Chart Supplement). Lights usually stay up about 15 minutes; click again on final if they die. A starred L on the sectional means lighting limitations — hours, intensity, or PCL — and you open the Supplement.

Rotating beacons (AIM 2-1-10), night and often IMC day: white and green = civilian land airport; white and yellow = water airport; white-white-green (dual-peaked white) = military; white, yellow, and green = heliport. A beacon on in daylight can mean the ground visibility is less than 3 SM or the ceiling is less than 1,000 feet — treat it as a weather clue, not a clearance to scud-run.

PAR scenario: Towered Class D, radio dead after you already have ATIS. Squawk 7600, enter left traffic unless the data block said RP, rock the ailerons when the gun hits you. Flashing green in the air means return for landing and wait for steady green to actually land. Flashing red in the air means leave — the airport is unsafe. After landing, flashing red means get off the runway; flashing white means go back to where you started (the ramp, not another circuit). At the nontowered alternate, CTAF is 122.9 because there is no UNICOM, enter 45° to left downwind at 1,000 AGL, and click the mic seven times so the REIL and MIRL come up.