How can pilots give a sign to the air traffic controllers if a plane has been hijacked? Today we will talk about the special transponder codes.
First of all, what is a transponder?
The transponder is a must-have communication device in busy airspaces, it sends signals and gives information about the current aircraft and flight, which are then received by the air traffic controllers. As a pilot, you will receive a transponder code of four digits by the tower of the airport of departure. This is from now on your identification number. With your transponder code, the ATC can identify you on their radar with your current altitude, cruise speed, and flight direction. In case of the following emergencies, pilots need to change the digits to the following:
Transponder Code 7500 (seven five – man with a knife)
This is the code all are afraid of to either send or receive. 7500 means that the aircraft has been hijacked. Perhaps the airplane is not under the control of the pilots anymore since hijacking is often achieved by using violence.
Sending the transponder code informs the ground crew about the emergency to start further procedures. Due to safety reasons, not much of the next actions are publicly known.
Transponder Code 7600 (seven six – hear nix)
Immediate action is required when 7600 is being sent. The code to signal a radio failure. Without radio, the ATC cannot navigate the aircraft through the airspace and poses a danger since coming closer to other aircraft is possible. Additionally, the landing could not be arranged with the ground crew.
Transponder Code 7700 (seven seven – going to heaven)
Not a very uncommon code, but important to inform the ground crew anyway. 7700 is the general code to signal any emergency. This could either be a medical issue of a passenger or a technical malfunction.
An aircraft sending the transponder code 7700 has first priority over other aircraft and gets immediate support.