PA.III.A.K2· K
Light signals & lost comms
ATC light signals and lost communications
Every tower cab still has a light gun, for one situation: an airplane that can't talk. The day you need the signals, you can't ask what they mean.
the signals
Six signals; four change meaning between air and ground.
| Signal | In flight | On the ground |
|---|---|---|
| Steady green | Cleared to land | Cleared for takeoff |
| Flashing green | Return for landing (a steady green will follow) | Cleared to taxi |
| Steady red | Give way to other aircraft and continue circling | Stop |
| Flashing red | Airport unsafe — do not land | Taxi clear of the runway in use |
| Flashing white | Not used in flight | Return to the starting point on the airport |
| Alternating red and green | General warning — exercise extreme caution | General warning — exercise extreme caution |
On the ground the signals are about the runway; in the air, about the airport. Flashing red on the ground gets you off the runway; in flight the whole field is unusable.
Acknowledge every signal: rock your wings by day, flash the landing light at night .
when the radio quits
Almost every radio failure is a knob — work the problem in order.
If it's genuinely dead, squawk 7600 — the tower will know what's wrong and reach for the light gun.
arriving NORDO at a towered field
Enter Class D without two-way communications only after building the traffic picture from outside : stay outside or above the surface area until you determine the direction and flow of traffic, then join the pattern in that flow, eyes on the tower cab. Keep watching to the ramp — your taxi clearance comes from the same lamp.
At night, a landing light makes you findable. And you're never obligated to land there — if the light gun is ambiguous, divert.
En route, a radio failure in VMC is no emergency: squawk 7600, continue VFR, land as soon as practicable.
Worked example. Fifteen miles out, tower doesn't answer; comm 2 is dead too, avionics breaker in.
You squawk 7600, landing light on, and hold four miles southeast — clear of the surface area, 500 feet above pattern altitude — while two airplanes land on runway 21 and one departs the same way.
Flow confirmed, you descend, enter left downwind for 21, and watch the cab for a steady green abeam the numbers. Rock your wings; after clearing the runway, look for a flashing green to taxi.
Common DPE questions
Alternating red and green means:
★ Next up
PA.III.A.K3 · Transponder, ADS-B & radar services
Primary radar sees a smudge. Your transponder turns it into a target with an identity and an altitude — the difference between a traffic call and silence.