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Preventing Near-Misses: ATC and TCAS

TCAS IndicatorThe Federal Aviation Administration reports that in the last twelve months, the rate of “serious” near collisions between commercial airliners has increased from 2.44 per million flights to 3.28 per million flights.

This rise could be due to the fact that there are more aircraft in the sky today than ever before. Meanwhile, the air traffic control infrastructure that governs the increasingly packed skies has changed little. Moreover, approximately half of all commercial air traffic now consists of smaller regional jets flying short trips at low altitudes. This means that the airspace closest to airport terminals has never been more congested than it is today, and more planes are flying all the time.

The FAA, as well as pilot and air traffic controller organizations, have stated that they are monitoring the situation carefully. Meanwhile, the Washington Post has issued sobering reports of dangerous mistakes made by air traffic controllers in their state which could have led to mid-air collisions if they hadn’t been corrected.

Nevertheless, potential air travelers should exercise judgment in their interpretation of reports about these near-misses.

For example, a recent story from the Associated Press about one of these near collisions mentions pilots making last second changes in course after alarms in the cockpit sounded to warn of an impending collision. This cockpit alarm is a called a TCAS (Traffic Collision Avoidance System), and it is linked to the aircraft’s transponder. TCAS provides pilots with a basic graphic representation of the space around the aircraft, warning pilots of other transponder-equipped aircraft, independently of human-operated air traffic control systems on the ground. Prompts from TCAS are always intended to take precedence over ATC instruction.

The current generation of TCAS (TCAS II) supports vertical evasion advisories, issuing loud, urgent “Climb now!” and “Descend! Descend!” commands to both aircraft. A newer TCAS system was in development which included lateral advisories as well to create further space between the aircraft, but there are currently no plans to implement this system. In normal situations, there is enough space between aircraft that vertical evasion is all that is needed to prevent danger.

When the media reports pilots making “last second” maneuvers to avoid an impending crash, it should not be taken literally in most cases. TCAS is a precautionary device meant to prevent near collisions from coming close to happening, but its loud vocal commands can seem ominous to passengers.

A simulation of the TCAS system in action can be seen in the video below:

The TCAS has only been mandated in commercial aircraft with over 30 passenger seats by the FAA since 1993. Thus, past collisions of the 1970s and 1980s cited in media stories occurred before this alarm was standard equipment, and when air traffic controller protocols were not as clearly defined. The progression of better technology and better training has reduced the threat of crashes in midair to an extraordinary degree.

The United States currently has the most crowded airspace of any country in the world. Meanwhile, American air traffic control has not kept pace with the growing amount of commercial air traffic. The problem is not new; air traffic controllers in the U.S. are increasingly overwhelmed and often working with aging, obsolete equipment.

Still, ATC has done exceedingly well. The majority of pilots will never be involved in a near miss during their entire careers. And for the relatively few occasions where it does occur, it is important to note that the 3.28 close call incidents per million flights — which works out to less than 10 per year — refer not to accidents, but serious situations where pilots came close to colliding and prevented a crash from happening.

In addition, various air agencies have been at work on specific proposals to make both fixed-wing and helicopter air ambulance travel safer, including requiring EMS operators to train employees in flight-risk evaluation and to use new flight-monitoring procedures that include up-to-date weather information and assistance in flight risk assessment decisions.

Meanwhile, the FAA is considering new safety monitoring proposals that apply specifically to helicopter air ambulances, including requiring specific distances of visibility (1/2 mile during daylight and 1 mile at night) to permit an even greater margin of safety in preventing mid-air collisions.

Though there will always be ways to make the busy skies safer for travel, flying today should not be considered dangerous — it is, as the old cliché states, much safer than driving. And, with the aid of technology and training, it is becoming safer all the time.

What are some ways we can continue to make air ambulance travel even safer?

The Federal Aviation Administration reports that in the last twelve months, the rate of “serious” near collisions between commercial airliners has increased from 2.44 per million flights to 3.28 per million flights.

This rise could be due to the fact that there are more aircraft in the sky today than ever before. Meanwhile, the air traffic control infrastructure that governs the increasingly packed skies has changed little. Moreover, approximately half of all commercial air traffic now consists of smaller regional jets flying short trips at low altitudes. This means that the airspace closest to airport terminals has never been more congested than it is today, and more planes are flying all the time.

The FAA, as well as pilot and air traffic controller organizations, have stated that they are monitoring the situation carefully. Meanwhile, the Washington Post has issued sobering reports of dangerous mistakes made by air traffic controllers in their state which could have led to mid-air collisions if they hadn’t been corrected.

Nevertheless, potential air travellers should exercise judgment in their interpretation of reports about these near-misses.

For example, a recent story from the Associated Press about one of these near collisions mentions pilots making last second changes in course after alarms in the cockpit sounded to warn of an impending collision. This cockpit alarm is a called a TCAS (Traffic Collision Avoidance System), and it is linked to the aircraft’s transponder. TCAS provides pilots with a basic graphic representation of the space around the aircraft, warning pilots of other transponder-equipped aircraft, independently of human-operated air traffic control systems on the ground. Prompts from TCAS are always intended to take precedence over ATC instruction.

The current generation of TCAS (TCAS II) supports vertical evasion advisories, issuing loud, urgent “Climb now!” and “Descend! Descend!” commands to both aircraft. A newer TCAS system was in development which included lateral advisories as well to create further space between the aircraft, but there are currently no plans to implement this system. In normal situations, there is enough space between aircraft that vertical evasion is all that is needed to prevent danger.

When the media reports pilots making “last second” maneuvers to avoid an impending crash, it should not usually be taken literally. TCAS is a precautionary device meant to prevent near collisions from coming close to happening, but its loud vocal commands can seem ominous to passengers.

A simulation of the TCAS system in action can be seen here (http://www.youtube.com/watch?v=z-6zF9PEtdU).

The TCAS has only been mandated in commercial aircraft with over 30 passenger seats by the FAA since 1993. Thus, past collisions of the 1970s and 1980s cited in media stories occurred before this alarm was standard equipment, and when air traffic controller protocols were not as clearly defined. The progression of better technology and better training has reduced the threat of crashes in midair to an extraordinary degree.

The United States currently has the most crowded airspace of any country in the world. Meanwhile, American air traffic control has not kept pace with the growing amount of commercial air traffic. The problem is not new; air traffic controllers in the U.S. are increasingly overwhelmed and often working with aging, obsolete equipment.

Still, ATC has done exceedingly well. The majority of pilots will never be involved in a near miss during their entire careers. And for the relatively few occasions where it does occur, it is important to note that the 3.28 close call incidents per million flights — which works out to less than 10 per year — refer not to accidents, but serious situations where pilots came close to colliding and prevented a crash from happening.

In addition, various air agencies have been at work on specific proposals to make both fixed-wing and helicopter air ambulance travel safer, including requiring EMS operators to train employees in flight-risk evaluation and to use new flight-monitoring procedures that include up-to-date weather information and assistance in flight risk assessment decisions.

Meanwhile, the FAA is considering new safety monitoring proposals that apply specifically to helicopter air ambulances, including requiring specific distances of visibility (1/2 mile during daylight and 1 mile at night) to permit an even greater margin of safety in preventing mid-air collisions.

Though there will always be ways to make the busy skies safer for travel, flying today should not be considered dangerous.

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