What do these numbers mean when flights display the emergency code “7700” in the air?

Many people first heard of the 7700 code when watching the movie "The Captain", which was adapted from the real event of the successful emergency landing of Sichuan Airlines flight 3U8633 in May 2018.

On January 20, Sichuan Airlines flight 3U8884 from Beijing Capital to Chengdu Shuangliu took off at 11:52 and landed at Chengdu Shuangliu Airport at 14:48. It issued a 7700 alarm at 14:39.

It is reported that the flight in question was operated by an Airbus A330-200 with a 10.5-year-old aircraft, with nationality registration number B-6535 and equipped with two Rolls-Royce Trent 772C engines.

The latest response from the Civil Aviation Administration

After the plane landed safely at Chengdu Shuangliu International Airport at 14:47, the Civil Aviation Administration of China Southwest Administration responded that the plane and all the people on board are currently safe.

Sichuan Airlines flight 3U8884 after landing

The Southwest Civil Aviation Administration said that after learning of the failure, the crew of Sichuan 3U8884 promptly reported the relevant information and the cabin order was stable. It is understood that the failure of a single engine of an aircraft is one of the routine subjects of the daily training of flight crews in handling special situations. Qualified pilots who have received systematic professional training can effectively handle and respond to ensure the safety of both the pilot and the aircraft.

What exactly does the “7700” code mean?

The picture comes from the Internet

Generally speaking, when a civil aviation flight displays the "7700" emergency code, it means that an emergency has occurred on the aircraft. The air traffic control radar system will distinguish this flight from ordinary flights so that relevant civil aviation units can provide emergency support.

For example, in this incident, Sichuan Airlines flight 3U8884 experienced a single engine failure during the flight. It is understood that single engine failure is one of the routine subjects of the flight crew's daily training for special situation handling. Qualified pilots who have received systematic professional training can effectively handle and respond to ensure the safety of both the pilot and the aircraft.

How to display the emergency code?

To understand emergency codes, you first need to know what a cockpit transponder is.

Schematic diagram of the cockpit transponder (picture from the Internet)

The cockpit transponder (also called secondary radar transponder), referred to as transponder, is a secondary radar system device on the aircraft. It is installed in the cockpit and communicates with the ground secondary radar through pulse signals. It is widely used in air traffic control and air collision avoidance system (TCAS).

Normally, the transponder code is assigned by air traffic control. The air traffic control informs the pilot of a set of four-digit codes for the transponder through radio signals, from 0000 to 7777, a total of 4096, and the pilot will set the transponder code according to the instructions. In this way, through the secondary radar, the ground tower can receive the information of the aircraft - including the position, altitude, speed, flight number, etc. of the aircraft in the air.

Cockpit controls of a 737 commercial airplane.

Image source: Tuchong Creative

But if the flight encounters special circumstances, the captain can set the transponder code to a special code.

7700

The transponder code "7700" means that the aircraft has encountered an emergency, such as mechanical failure, sudden illness of a crew member on board, etc., but it is not necessarily in a very dangerous situation.

7600

The transponder code "7600" means communication failure, communication failure or radio loss.

Flight route map of Air India flight AI171 (picture from the Internet)

On March 10, 2017, Air India flight AI171 lost contact with the Budapest Regional Control Center due to a technical failure while en route from Ahmedabad Airport in India to London Heathrow Airport. Subsequently, the Czech Republic, Germany, Belgium and the United Kingdom sent air force fighters to escort the flight.

7500

The transponder code "7500" stands for unlawful interference, which means an emergency situation in which the aircraft is being hijacked or is in danger of being hijacked.

EgyptAir Flight 702 flight path map, showing the flight circling around Geneva

On February 17, 2014, an Ethiopian flight originally scheduled to fly to Rome landed in Geneva, Switzerland after issuing the "7500" code.

The plane took off from the Ethiopian capital at 0:30 local time on the 17th and was scheduled to arrive in Rome at 4:40 local time on the 17th. When flying over Sudan, the emergency code "7500" was displayed and the plane was escorted by military aircraft. Later, Swiss police confirmed that the hijacker was a pilot.

Marking the aircraft in red (picture from the Internet)

It is worth noting that when an aircraft displays the above three emergency codes, the aircraft will be distinguished by a red mark in the air traffic control radar system, which can remind controllers and other crews in the air to avoid it in time.

Emergency situations are rare events

I hope everyone doesn't encounter

But if something happens:

Don't panic, don't be afraid.

Be sure to follow the crew's instructions!

Comprehensive sources: Xinhuanet, CCTV News Client, Guangming Daily, etc.

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