ATC Light Signals from the Tower
Traffic Light Signal
Even before you learned to drive, you knew about the Traffic Light Signal. Red for Stop. Yellow for Caution. Green for Go. Traffic on the streets would be chaos if drivers and pedestrians did not understand and obey these simple and well known traffic signals.
If you know someone who thinks they are an expert driver, then tell them you want to give them a quick “Transport Canada” Driving test:
Start by telling them to spell the word “SPOT”. After they have spelt the word “S – P – O – T”, then ask them to say the word “SPOT” three times quickly. “Spot – Spot – Spot”. Next, ask them what they do when they come to a Green Light. Chances are, they will respond with “STOP”! (Hmmmm. For an expert driver, they should really learn the proper Traffic Signals!)
Back to Traffic Signals
Just like driving an automobile, Pilots also must learn and obey Traffic Light Signals. You might wonder why a Pilot would need to use Light Signals when they have a Radio for Communication. In fact, as a pilot you will seldom use light signals. However, radios sometimes stop working. In the event of a communications failure, you will need to fall back on Light Signals for communication.
ATC Light Signals
Air Traffic Control (ATC) will use a powerful Light Gun to Signal the Pilot in the event of Radio Communications failure or other emergency when the pilot does not have a working Radio in the aircraft. When a pilot is flying with No Radio (NORDO), they must watch for the Light Signals from the Control Tower.
Similar to an Automobile Traffic Light, the ATC Light Signals will use three different colours. However, instead of Red, Green and Yellow used by Automobile Traffic Signals, the ATC Light Signals use the colours Red, Green and White.
Red, Green, White
The Controller will direct a concentrated beam of light directly at an aircraft to communicate with the NORDO Pilot. The Light Gun uses three different light colours. The pilot may see Red, Green or White signals from the controller. Each colour has a specific meaning.
Steady vs. Flashing Light
In addition to specific colours (Red, Green or White) the light beam may be Steady or Flashing. The pilot must recognize both the colour and also the pattern (Steady or Flashing) to properly decode the Light Gun message from the Control Tower.
Ground vs. Air
The Light Signals also have different meanings depending if your aircraft is on the Surface (Ground), or if your aircraft is In Flight (Air). The ATC Light Signals Chart shown here details the meaning of each Light Signal for aircraft on the Ground and in the Air.
Light Signals on the Ground
Steady Green = GO
A Steady Green light signal on the ground means the same to an airplane as a green traffic light means to a car. GREEN means GO. The steady green light means the aircraft is cleared for takeoff. The pilot may proceed to takeoff now.
A Flashing Green light signal on the ground means that you are cleared to Taxi. The Pilot has clearance to taxi the aircraft.
Steady Red = STOP
A Steady Red light signal on the ground means the same to an airplane as a red traffic light means to a car. RED means STOP. The steady red light means the aircraft must stop immediately. The controller wants the pilot to hold their position. When the time is right, the controller will provide a flashing green light or steady green light to communicate to the pilot they may continue to taxi, or they are cleared to takeoff.
A Flashing Red light signal on the ground means the same to an airplane as flashing red lights mean to a car. In a car, if you saw a flashing red light behind you (i.e. Police car or other emergency vehicle), you would get off the road. Similarly, in an aircraft, the flashing red light means the pilot must Taxi Clear of the Runway in use. (i.e. Get off the Runway) If you have just landed on the runway, the controller might signal you with a Flashing Red light to have you clear the active runway. The controller wants you to find the nearest taxiway and get off the runway to allow other aircraft to use the runway.
The Flashing White signal only applies to aircraft on the surface (ground), and it does not apply to aircraft In Flight (Air). This indicates the pilot should return to their starting point on the airport. Possibly, the airport is too busy for NORDO operations, and the controller wants you to return your aircraft to the airport parking apron.
When flying in the United States, pilots should also be aware of the Alternating Red/Green signal light. It is the same for both aircraft on the ground, and in the air. It is an important warning to the pilot to exercise extreme caution. Perhaps there are multiple NORDO aircraft in the area, and the controller is warning you to be particularly diligent.
Light Signals in the Air
Steady Green = GO
The Steady Green light signal to an aircraft in flight, is similar to the meaning of a Green Traffic Light for an automobile. GREEN means GO. This means the aircraft is cleared to land.
A Flashing Green light signal to an aircraft in flight means you should return for landing. This is essentially a Go-Around command. As the light is flashing, you do not have clearance to land, so you must return for landing via Go-Around.
A Steady Red light always means stop. In your car, you always stop at a red traffic light. However, for an aircraft in flight, it is impossible to simply stop. You must continue flying, but the steady red light indicates you must give way to other aircraft and continue circling. If the air traffic is particularly heavy, it might not be possible for the controller to sequence your airplane into traffic for landing at the moment. The red light indicates you must hold in your present position until you are cleared to land. At that time you will then receive a steady green light to communicate your clearance to land.
A Flashing Red light signal to an aircraft in flight indicates danger. Similar to the flashing red light beacons you see on obstacles such as TV Towers, the flashing red should warn you to stay away. Airport unsafe. Do not land.
As already mentioned, the Alternating Red/Green light signal is used in the U.S., and it applies to both aircraft on the surface and in flight. It is a warning to Exercise Extreme Caution.
Acknowledge Light Signals
Pilots should acknowledge that the light signal communications from the tower have been received. They acknowledge the instruction by wiggling their wings if they are in flight. If they are on the ground, they move the ailerons to signal acknowledgement. During night, the pilot can acknowledge the signals by flashing their landing or navigation lights.
In today’s world of communications, these light signals may seem primitive. However, when NORDO situations occur, these standardized light signals are a very effective means of communication. As a pilot, a back-up hand-held radio is always a good idea. But, if you ever find yourself without a radio for communications, you will need to know these important ATC (Air Traffic Control) Light Gun Signals used in Aviation.