On Wednesday night, US Time, a passenger jet and the US Army helicopter Ronald Reagan collided at a low height near Washington National Airport, and crashed into the Potomac River.
A total of 60 passengers – which includes US and Russian champion Figure Skaters – and four crews were riding on the flight AA5342 from Wichita, Kansas to American Airlines. Three military personnel were in the helicopter, operating a regular training flight. Officials say any aircraft survived any board.
The accident occurs exactly a month after a passenger jet crashed in South Korea – possibly as a result of a bird strike – killing all of 181 people on the board. Both events have focused on aviation security worldwide.
In the case of the most recent tragedy in the US, technology exists to help pilots avoid the midar collision with other aircraft. It is known as a system of avoiding traffic collision – or TCAS.
So how does it work? And why can it fail to stop the disaster in this case?
What is TCAS?
A TCAS is an aircraft security system that monitors aircraft around an aircraft for other aircraft equipped with transponders. These are devices that listen and react to upcoming electronic signals.
System – sometimes known as an ACAS (airborne conflict avoidance system) – is independently operated of an external air traffic control system. Its purpose is to immediately alert pilots for nearby aircraft and potential midar confrontation.
Since technology was developed in 1974, it has made many progress.
The first generation technique, known as TCAS I, is what is around an aircraft. This provides information about the effects and height of any surrounding aircraft. If there is a risk of collision, it produces that “traffic advisor” – or is known as TA. When a TA is released, the pilot is informed about the danger, but must determine the best action to take itself.
The second generation technique, known as TCAS II, moves a step forward: it provides a pilot to avoid conflict with a nearby aircraft or avoid conflict with traffic, either descending, climbing By adjusting the bend or their speed.
These new systems are also capable of communicating with each other. This ensures that the advice given to each aircraft is coordinated.
Any aircraft used for commercial purposes should be equipped with TCAS in accordance with international rules under the Chicago Convention. There are specific provisions under convention for non -commercial aircraft.
Military helicopters are not subject to the provisions of the Chicago Convention (although they are subject to domestic laws and rules). And it is reported that the military helicopter did not have a TCAS system on the board.
Limits of Tcas at low height
Even though the military helicopter involved in the accident has been fitted with TCAS, technology still has limitations. In particular, it is interrupted at a height of about 300 meters.
The last recorded height of the American Airlines flight AA5342 was about 90 meters. The last recorded height of the American military helicopter colliding with the aircraft was about 60 meters.
It is not an accident that a Tcas is interrupted at low height. In fact, it is part of the design of technology.
This is primarily because the system depends on the radio ultimate data, which measures the height and becomes less accurate near the ground. This can probably result in incredible collision-revision instructions.
Another issue is that an aircraft at such a low altitude cannot proceed to avoid confrontation.
Many site near Mrs. Mrs.
Ronald Reagan Washington National Airport is one of the busiest airports in the United States. Commercial, military and private aircraft share very limited airs and corridors.
It has been the site of many near Mrs. Mrs. in recent years.
For example, in April 2024, a commercial aircraft pilot coming into the ground was to take action to avoid a helicopter that was about 100 meters below it. In an incident report, Pilot said:
We never received traffic warnings from (air traffic control), so we were unaware that it was there.
Many people, including Democratic American senator Tim Can, pointed out to Miss why the plan to allow more flights to Ronald Reagan Washington National Airport should not be carried forward. Despite this, the plan was approved next month.
All this will undoubtedly be investigated by the National Transport Safety Board as part of the investigation in this disaster.
Author: Crystal Zhang, Associate Professor, Aerospace Engineering and Aviation, RMIT University
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