Two commercial airlines experienced a near miss earlier this month south of San Juan in Puerto Rico. An Air France jet and an American Airlines plane were high above the Caribbean Sea and closed in on each other before TCAS activated to avoid a collision safely. The incident took place at midnight on Sunday 13 December 2020.
A potential collision between two passenger planes is 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 jet, registered as F-GZNN, was on its way to Lima from Paris. The American plane, N926NN, was on its way to Miami after departing from St George’s in Grenada.
Air France’s Boeing 777 is seven and a half years old and painted in the distinctive SkyTeam color. The American Airlines plane is six and a half years old. This is the first recorded incident for the Air France aircraft and the second recorded incident for the American Airlines jet.
Air France’s Boeing operated flight AF480. This is Air France’s regular departure at 10:30 from Charles de Gaulle straight down to Lima, and later on the same day. The American Airlines flight was AA1546, departing at 16:17 from Maurice Bishop International Airport in Grenada en route to Miami.
According to The Aviation Herald, the Air France Boeing 777 was 220 nautical miles south of San Juan in Puerto Rico and was climbing from FL360 to FL380. The American Airlines Boeing 737 was already at FL380 and was able to quickly converge with the Air France jet in a right angle.
The traffic warning and collision avoidance systems (TCAS) on both aircraft were then activated. The American Airlines Boeing 737 climbs and the Air France Boeing 777 descends to FL374. According to the report, the American Airlines plane crossed the flight path of the Air France plane at 38,800 feet, about four nautical miles before AF480. The Air France Boeing 777 crosses with the Boeing 737’s flight path at 37,400 feet.
The incident highlights the value of TCAS
After passing each other without further incident, both aircraft resumed their originally planned flight routes and proceeded to their destinations.
This incident highlights the value of TCAS (also known as air collision avoidance)
System or ACAS in some other jurisdictions). TCAS operates independently of the ground
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 the ground radars on air traffic control. The level of protection provided by TCAS equipment depends on the type of transponder that the aircraft is transporting. TCAS is a last resort safety net that operates independently of any separation standards.
Modern 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 the nearby aircraft and, if necessary, issue a warning.
While the mid-December incident involving Air France and American Airlines planes is a good example of TCAS working well, TCAS operates on short time frames. TCAS starts less than a minute before any possible conflict. Although four nautical miles seems to be at a safe distance, things will happen fairly quickly if planes travel hundreds of miles more per hour.
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