DALLAS — In the world of commercial aviation, sometimes two or more aircraft make unplanned contact with one another when taxiing or during pushback. On the runway, airplanes may also strike one another, and could even slam into the terminal building.
Aircraft collisions are avoided through a variety of measures, including air traffic control, communication between pilots, and technology such as radar and collision avoidance systems.
Air traffic control is responsible for managing the flow of aircraft in and out of airports, and for ensuring safe separation between aircraft. Through radio communication, air traffic controllers provide pilots with instructions on when and where to take off, land, and taxi. They also monitor for potential conflicts and issue alerts when necessary.
Pilots themselves also play a key role in avoiding collisions. They are required to follow all air and ground traffic control instructions and to maintain situational awareness at all times. Pilots rely on a combination of visual cues and technology to navigate and avoid potential conflicts.
Though rare, increased miscommunication between ATC and pilots, a lack of situational awareness, a lack of trust in the cockpit, marshaling mishaps, and errors from collision avoidance systems, are some of the causes of near misses or collisions at airports.
However, there’s a reason 45,000 flights take off daily in the United States, and there has not been a fatal commercial plane crash since 2009. In this post, we list a few strategies implemented in commercial aviation to prevent aircraft collisions while on the ground, making air travel the safest mode of transportation.
Pilots operating aircraft on the ground may have a restricted view of the outside world through their cockpit windows, increasing the possibility of a collision with aircraft, automobiles, airport infrastructure, and terminal buildings in the vicinity.
Aircraft wing tips and tails can move vast lengths away from the nose when they are turning, a phenomenon known as Swept Wing Growth, which increases the possibility that a portion of the aircraft would collide with other adjacent objects like other aircraft or vehicles when navigating tight places.
In an airport, aircraft carrier, or helipad, ground personnel known as a marshaller communicates visually with the pilots of the aircraft to assist in operations such as turning, slowing down, stopping, starting, and turning off engines.
Mashallers directs aircraft safely and precisely to the location where it should stop at the parking gate after it lands, as well as when it should move out to the maintenance hangar or to the runway while standing in the prominent position in front of the aircraft and being visible to the pilots. He/she also drives a follow-me car to indicate directions to the pilots.
Additional lookout personnel who communicates with the marshaller from the wing tips or tail may be required in order to ensure that there is sufficient space between the aircraft and other objects, preventing a collision.
There are also vehicles and also smart systems that ground controllers use to aid pilots visually. You might have seen them in use.
Follow Me Cars
Sometimes, the marshaller indicates directions to the pilot by driving a “Follow-Me” car—usually a yellow van or pick-up truck with a checkerboard pattern—prior to disembarking and resuming signaling, though this is not an industry standard.
They are also the taxiway lights that turn green when the specific aircraft is given a taxi route clearance and back to red when no aircraft is supposed to taxi on it. For example, a frequent callout might be “Singapore875, taxi on the green, W7, NC, S3” the keyword here being “taxi on the green.”
Firstly, being bi-colored provides a secondary confirmation that they are taxiing on the correct routing and secondly, with all taxiway lights out there, they serve as a visual aid on where the center of the taxiway is and making sure that there is enough wingtip clearance from both edges of the taxiway.
At busier and better-equipped hubs, marshallers are replaced on some stands with a Visual Docking Guidance System (VDGS), of which there are many types.
Electronic displays used in Advanced Visual Docking Guidance Systems (A-VGDS) carry out the same tasks as an AGNIS/PAPA installation, but much more accurately. They might also offer protection against collisions with stationary objects.
The entire area is being scanned by an infrared high-definition camera for any potential objects that could endanger the safety of the aircraft. The typical separation is 8 to 50 meters. (26–164 ft). The A-VGDS has a low visibility feature that enables aircraft to park in extremely bad visibility. Emergency stop buttons are typically found on stands and in the jetway/gate area of A-VDGS systems, which instantly activate the stop indication.
Another example is the RLG GIS-206, which uses lasers to determine the position of the aircraft, subsequently displaying the distance the aircraft must go as well as showing Azimuth guidance.
Anti-collision lights are a set of lights that must be installed on every aircraft to enhance their visibility and prevent collisions by alerting other pilots, ground personnel, and vehicles to the position of an active aircraft.
To be seen by the ground crew, the majority of transport category aircraft have two types of anti-collision lights, the beacon, and the strobe.
A beacon is a red flashing light whereas strobes are synchronized flashing white lights. In many aircraft, there are two beacon lights – one on top of the fuselage and the other on the bottom. Strobe lights are three, one near the trailing edge of each wingtip, and one below the tail cone of the aircraft.
In accordance with aviation regulations, an aircraft’s anti-collision lights must be turned on as soon as its engine is started for air navigation purposes. As a safety measure, they must also be turned on before an engine is started or a propeller or rotor is made to move.
To prevent collisions, ingestion by engine intake, jet blast, radar, and fire dangers, they advise anyone approaching an aircraft that is in operation to keep a safe distance of at least 10 meters and take all required precautions.
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Featured image: Delta Air Lines N301NB Airbus A319. Photo: Michael Rodeback/Airways