On Wednesday night time US time, a passenger jet and US Military helicopter collided at a low altitude close to Ronald Reagan Washington Nationwide Airport, and crashed into the the Potomac River.
A complete of 60 passengers – together with US and Russian champion determine skaters – and 4 crew had been on board the American Airways flight AA5342 from Wichita, Kansas. Three navy personnel had been within the chopper, which was conducting a routine coaching flight. Authorities say nobody on board both plane survived.
This crash comes simply over a month after a passenger jet crashed in South Korea – probably on account of a hen strike – killing all however two of the 181 individuals on board. The 2 incidents have targeted consideration on aviation security world wide.
Within the case of the latest tragedy within the US, expertise exists that’s designed to assist pilots keep away from midair collisions with different plane. It is called the Visitors Collision Avoidance System – or TCAS.
So how does it work? And why may it have failed to stop catastrophe on this case?
What’s a TCAS?
A TCAS is an plane security system that screens the airspace round a airplane for different plane geared up with transponders. These are units that hear for and reply to incoming digital indicators.
The system – additionally typically known as an ACAS (Airborne Collision Avoidance System) – operates independently of an exterior air site visitors management system. Its objective is to alert pilots instantly to close by plane and potential midair collisions.
Because the expertise was developed in 1974, it has undergone a lot of advances.
The primary era expertise, often called TCAS I, screens what’s round an plane. It gives info on the bearing and altitude of any close by plane. If there’s a danger of collision, it generates what’s often called a “Traffic Advisory” – or TA. When a TA is issued, the pilot is notified of the risk, however should themselves decide the perfect evasive motion to take.
The second era expertise, often called TCAS II, goes a step additional: it gives a pilot with particular directions on the right way to keep away from a collision with a close-by plane or battle with site visitors, both by descending, climbing, turning or adjusting their pace.
These newer programs are additionally capable of talk with one another. This ensures the recommendation given to every plane is coordinated.
Any plane used for industrial functions should be geared up with a TCAS in accordance with worldwide rules beneath what’s often called the Chicago Conference. There are particular provisions beneath the conference for noncommercial plane.
Army helicopters are usually not topic to the provisions of the Chicago Conference (though they’re topic to home legal guidelines and rules). And there are studies the navy helicopter didn’t have a TCAS system on board.
Authorities have already eliminated dozens of our bodies from the Potomac River following the midair crash.
Carolyn Kaster/AP
Limitations of TCAS at low altitudes
No matter whether or not the navy helicopter concerned within the crash was fitted with a TCAS, the expertise nonetheless has limitations. Particularly, it’s inhibited at altitudes under roughly 300 metres.
The final recorded altitude of American Airways flight AA5342 was roughly 90 metres. The final recorded altitude of the US navy helicopter that collided with the airplane was roughly 60 metres.
It isn’t an accident {that a} TCAS is inhibited at low altitudes. The truth is, that is a part of the design of the expertise.
That is primarily as a result of the system depends on radio altimeter information, which measures altitude and turns into much less correct close to the bottom. This might probably lead to unreliable collision-avoidance directions.
One other subject is that an plane at such a low altitude can not descend any additional to keep away from a collision.
A TCAS isn’t designed to supply anti-collision recommendation when an plane is at a really low altitude.
Stephanie Scarbrough/AP
The positioning of a number of close to misses
Ronald Reagan Washington Nationwide Airport is likely one of the busiest airports in the USA. Business, navy and personal plane share very restricted airspace and corridors.
It has been the location of a number of close to misses in recent times.
For instance, in April 2024, a industrial airplane pilot coming into land needed to take evasive motion to keep away from a helicopter that was roughly 100 metres beneath it. In an incident report, the pilot stated:
We by no means acquired a warning of the site visitors from (air site visitors management) so we had been unaware it was there.
Many individuals, together with Democratic US senator Tim Kaine, pointed to this close to miss as proof of why a plan to permit extra flights into Ronald Reagan Washington Nationwide Airport mustn’t proceed. Regardless of this, the plan was accredited the next month.
All of it will undoubtedly be examined as a part of the investigation by the Nationwide Transportation Security Board into this catastrophe.
