When an aircraft radio communications fails or loses its course, or is in distress, the pilot usually initiates distress actions. If the pilot is unable to establish radio contact due to the unserviceable state of the Radio Transmitter (RT) or Radio Receiver (WT), they can relay their distress message through the radar screen by adopting one of the following procedures as applicable to the situation.
Pilot Action
Setting up Squawking
If the IFF (Identification Friend or Foe) system is serviceable, the pilot sets the Squawk to 7600. This Squawk is an international radio communication failure code. When an aircraft displays Squawking 7600 on the radar screen, the Air Traffic Controller understands that the aircraft has experienced radio communication failure. The controller then takes appropriate action. If the IFF system is unserviceable, the pilot follows the procedures outlined below.
When the Transmitter is Unserviceable
If the transmitter is unserviceable, the aircraft flies in a triangular pattern to the right (clockwise), holding for two minutes for each leg (1 minute for jet aircraft). The aircraft completes at least two such patterns before resuming its course and repeats the same at twenty-minute intervals or less if required.
When Both Transmitter & Receiver Are Unserviceable
If both the transmitter and receiver become inoperative, the pilot flies in a triangular pattern to the left (anticlockwise), holding for two minutes for each leg (1 minute for jet aircraft). The aircraft completes at least two such patterns before resuming its course and repeats the same at twenty-minute intervals or less if required.
Following the Flight Plan
If all procedures fail, the captain continues to follow the flight plan, maintaining appropriate routes, altitude, and published airspace procedures. Upon reaching the destination, the pilot attempts to land without the assistance of ATC services. After safely landing, the pilot reports the communication failure to the appropriate authority.
Air Traffic Control Action
When ATC controllers identify that an aircraft has experienced communication failure, they take the following steps:
Actions to Establish Communication
The controllers continue trying to re-establish communication with the pilot. They may also attempt to communicate through alternative means such as data link communication or direct messages to the aircraft’s cockpit display system.
Guiding Another Aircraft
ATC may request another nearby aircraft to guide the affected aircraft up to the landing. ATC may declare an emergency and prioritize landing instructions.
Radar Monitoring
ATC controllers continue to closely monitor the radar display to track the exact position and altitude of the aircraft. They inform other nearby aircraft of the situation and ensure traffic separation to avoid collisions.
Using Light Signals
When the aircraft is within visual range of the control tower, ATC uses light signals to communicate instructions to the pilot. These signals are standard and convey essential information such as clearance to land, hold position, or go around.
