Air France 777 and American Airlines 737 are almost in conflict over the Caribbean Sea

Two commercial airlines suffered near misses earlier this month south of San Juan in Puerto Rico. An Air France jet and an American Airlines plane were high over the Caribbean Sea and approaching before TCAS activated to safely avoid a collision. The incident occurred in the middle of the evening on Sunday, December 13, 2020.

A potential collision between two passenger jets avoided

According to Simon Hradecky’s report in The Aviation Herald, the incident involved an Air France Boeing 777-300 and an American Airlines Boeing 737-800. The Air France plane, registered F-GZNN, was en route to Lima from Paris. The American Airlines plane, registration N926NN, was heading for Miami after leaving St George in Grenada.

Air France’s Boeing 777 is seven and a half years old and painted in the distinctive SkyTeam livery. The American Airlines plane is six and a half years old. This is the first recorded incident for the Air France plane and the second recorded incident for the American Airlines plane.

The Air France Boeing was operating flight AF480. This is the regular departure of Air France at 10:30 am from Charles de Gaulle directly to Lima, arriving later the same day. The American Airlines flight was AA1546, departing 16:17 from Maurice Bishop Grenada International Airport to Miami.

According to The Aviation Herald, Air France’s Boeing 777 was 220 nautical miles south of San Juan in Puerto Rico and was climbing to FL380 from FL360. The American Airlines Boeing 737 was already at FL380 and was rapidly converging with the Air France jet at a right angle.

The traffic warning and collision avoidance systems (TCAS) of the two aircraft were then activated. The American Airlines Boeing 737 climbed and the Air France Boeing 777 descended to FL374. The report says the American Airlines jet crossed the Air France plane’s flight path at 38,800 feet, about four nautical miles ahead of the AF480. The Air France Boeing 777 crossed the flight path of the Boeing 737 at 37,400 feet.

The incident highlights the value of TCAS

Having passed each other without further incident, the two planes resumed their initially planned flight paths and continued to their destinations.

This incident highlights the value of TCAS (known as the
System or ACAS in other jurisdictions). TCAS operates independently of the ground system
air traffic control system and provides collision protection for commercial passenger aircraft.

TCAS uses the same radar beacon transponders installed on aircraft to work with air traffic control ground radars. The level of protection provided by TCAS equipment depends on the type of transponder the aircraft is carrying. TCAS is a safety net of last resort that operates independently of any separation standards.

Contemporary TCAS systems use secondary surveillance radar transponder signals. An aircraft’s TCAS examines the Mode C and Mode S transponders of nearby aircraft. It can read the altitude and range of nearby aircraft and, if necessary, issue an alert.

While the mid-December incident involving the Air France and American Airlines jets is a good example of how well TCAS works, TCAS is operating on tight deadlines. TCAS starts up in less than a minute before any potential conflict. While four nautical miles may seem like a safe distance, when aircraft are each traveling hundreds of miles and more per hour, things are going to happen quite quickly.

What do you think of the incident? Let us know what you think in the comments section.