On Wednesday evening 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 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 army 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 chook strike – killing all however two of the 181 folks 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 named the Site visitors Collision Avoidance System – or TCAS.
So how does it work? And why may it have failed to forestall catastrophe on this case?
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What’s a TCAS?
A TCAS is an plane security system that screens the airspace round a airplane for different plane outfitted with transponders. These are units that hear for and reply to incoming digital alerts.
The system – additionally typically known as an ACAS (Airborne Collision Avoidance System) – operates independently of an exterior air site visitors management system. Its function is to alert pilots instantly to close by plane and potential midair collisions.
For the reason that expertise was developed in 1974, it has undergone quite a lot of advances.
The primary era expertise, often known as TCAS I, screens what’s round an plane. It supplies data on the bearing and altitude of any close by plane.
If there’s a danger of collision, it generates what’s often known as a “Traffic Advisory” – or TA. When a TA is issued, the pilot is notified of the menace, however should themselves decide one of the best evasive motion to take.
The second era expertise, often known as TCAS II, goes a step additional: it supplies 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 techniques are additionally capable of talk with one another. This ensures the recommendation given to every plane is coordinated.
Any plane used for industrial functions have to be outfitted with a TCAS in accordance with worldwide laws below what’s often known as the Chicago Conference. There are particular provisions below the conference for noncommercial plane.
Navy helicopters are usually not topic to the provisions of the Chicago Conference (though they’re topic to home legal guidelines and laws). And there are studies the army helicopter didn’t have a TCAS system on board.
Limitations of TCAS at low altitudes
No matter whether or not the army helicopter concerned within the crash was fitted with a TCAS, the expertise nonetheless has limitations. Specifically, it’s inhibited at altitudes beneath roughly 300 metres.
The final recorded altitude of American Airways flight AA5342 was roughly 90 metres. The final recorded altitude of the US army helicopter that collided with the airplane was roughly 60 metres.
It’s not an accident {that a} TCAS is inhibited at low altitudes. In truth, 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 doubtlessly end in unreliable collision-avoidance directions.
One other challenge is that an plane at such a low altitude can not descend any additional to keep away from a collision.
The positioning of a number of close to misses
Ronald Reagan Washington Nationwide Airport is without doubt one of the busiest airports in america. Business, army 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 mentioned:
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 shouldn’t proceed. Regardless of this, the plan was authorised the next month.
The near-miss crash at DCA yesterday is one more instance of why we will’t hold cramming extra flights to this airport. I’ve been warning about this for years—the system is overwhelmed and it’s a menace to public security.
— Tim Kaine (@timkaine) April 19, 2024
All of this may undoubtedly be examined as a part of the investigation by the Nationwide Transportation Security Board into this catastrophe.
Chrystal Zhang, Affiliate Professor, Aerospace Engineering & Aviation, RMIT College
This text is republished from The Dialog below a Inventive Commons license. Learn the authentic article.
