How planes, military aircraft work to avoid ‘preventable’ collisions

More than 40 bodies have been pulled from the Potomac River near Washington, D.C., after Wednesday’s fatal collision that saw an Army helicopter and American Airlines flight collide, killing 67 people aboard the two aircraft.

U.S. Transportation Secretary Sean Duffy said both aircraft had been flying standard flight patterns when the incident occurred, and there had been no breakdown in communication.

Here’s a look at how civilian and military aircraft work to avoid accidents like Wednesday’s tragic crash.

Aviation experts who spoke with Global News stressed neither type of aircraft typically communicate with one another directly.

“That would create some mayhem in the system,” said Brian Alexander, a former military aircraft pilot and aviation accident lawyer.

“So the communications go through air traffic control. Ideally, the aircraft operating in the same airspace will be on the same frequency and controlled by the same controller. However, that rule is not always the case.”

Commercial aircraft use very high frequency (VHF) radios to communicate, while military operate on ultra high frequency (UHF), so communication between the planes is difficult though the military will sometimes utilize VHF allowing pilots to hear them.

He said air traffic control gives direction and advises on other vessels in the air while also ensuring separation between different aircraft.

But with military helicopters typically flying at lower altitudes than commercial aircraft, they too have to keep watch around them.

“The helicopters were essentially always and only operating under visual conditions in the corridor,” said Alexander, who has flown the same D.C. route where the crash occurred multiple times.

“Even though they’re talking to the air traffic control, they are required to see and avoid, they are required to have their head on a swivel at all times, to be monitoring other air traffic and seeing and avoiding the same traffic.”

Along the Potomac route, military helicopters are required to fly no higher than 200 feet, yet the collision occurred at an altitude of 300 feet, according to Reuters.

Even before the plane descended to 300 feet, Boeing 777 pilot Shem Malmquist said commercial airline pilots would have been starting their approach to the airport, which can change what those pilots are looking for.

During descent, other than watching for potential hazards like birds or drones, pilots are focusing on landing and while they are looking out the window, they’re not going to be necessarily focusing on looking for aircraft nearby once air traffic controllers clear them to go ahead.

“When you are on final approach, and especially on this one, they’re transitioning from one runway to another. It’s a challenging thing to do there,” Malmquist said.

“The crew is going to be very, very occupied with ensuring that their flight path and, of course, their aircraft speeds and power settings and everything are correct for the approach to make sure that there aren’t any other problems.”

Air traffic control had asked the plane pilot a few minutes before landing if the plane could land on the airport’s shorter Runway 33, which the pilots said they could.

Less than 30 seconds before the crash, an air traffic controller asked the helicopter if it had the arriving plane in sight, according to released recordings.

The helicopter acknowledged it had the plane in its sights and was advised to maintain visual separation and to pass behind the aircraft, but the crash followed.

Planes also use the Traffic Alert and Collision Avoidance System (TCAS) to avoid collisions with other aircraft. Military flights use the Automatic Dependent Surveillance-Broadcast to track aircraft location.

In the case of TCAS, it detects what other aircraft are transmitting including position and altitude and will provide guidance to avoid that aircraft such as to climb or descend.

But when below 1,100 feet, it will only give visual information, not warnings.

“It’s based on the fact that the probability of having a collision with another airplane when you’re in that flight regime is extremely remote,” Malmquist said.

“If a system were to give what we call a resolution advisory telling pilots to descend, descend now or even climb, climb now when the airplane is in such a critical phase, that could cause secondary risks, problems. And in one case, of course, flying into the ground or the water and on the other, potentially a loss of control of the aircraft.”

This is why commercial pilots keep an eye on their runways, and helicopter pilots are told to keep their heads on a “swivel,” with air traffic communicating between them.

Speaking to Reuters, pilot Rick Redfern cautioned that visibility can also create issues, noting he was able to use evasive maneuvers when he spotted a Coast Guard helicopter hovering above the Potomac about a decade ago during a flight.

Air traffic control promptly also warned the helicopter to stay clear.

But at night in similar areas, the lights from other planes and the surrounding communities can disorient pilots.

Alexander said there are challenges that exist in the area because of the lightning and high amount of traffic, which is why air traffic control information is so crucial.

“It’s a very challenging environment visually for the pilot, which is why the call out of the traffic, the acknowledgement of the specific traffic being called out and then the avoidance of the traffic by adequate separation is the most critical thing,” he said.

Both Alexander and Malmquist say early indications are that the collision was “preventable,” and that part of the investigation will look to air traffic control and staffing.

“The system has been blinking red for a number of years with staffing issues, underfunding, a technology lag and an experience transition generationally where there’s been some very significant concerns about our air traffic control system here,” Alexander said.

“This is a terribly tragic crash that all the early indications suggest strongly, absolutely, was preventable.”

According to a Federal Aviation Administration report, obtained by the Associated Press, there was one traffic controller working two positions at the time of the crash, a configuration that was “not normal” for the time of day and volume of traffic.

“There is a tacit pressure on controllers to keep things moving and they are going to want to make the system work,” Malmquist said.

“If they are told, ‘You only have one person and you have to get the job done,’ they’re going to find ways to get that job done.”