Pilot representatives are calling for new rules in South America to make aircraft fly offset from existing airway centrelines in a bid to avoid mid-air collisions in the event of vertical separation failing such as the September Gol crash.

The International Federation of Air Line Pilots’ Associations (IFALPA) says some of its South American member pilot unions are recommending the implementation of lateral offset procedures, partly because modern avionics make the possibility of two aircraft flying on very precise reciprocal headings, even if separated vertically, much more likely. The problem is compounded by imperfect pronounciation by air traffic controllers when flight plans change. The federation is also urging pilots to be particularly cautious while operating in Brazilian airspace.

It follows last September’s fatal collision between a Gol Lihnas Aéreas Boeing 737-800 and an Embraer corporate aircraft over the Amazon, with the loss of all those on board the larger jet. The aircraft had been travelling in opposite directions on the same airway and at the same altitude.

Offset procedures, whereby aircraft fly a displaced course parallel to the normal airway centreline, similar to driving on the right- of lefthand side of a road, are designed to mitigate the increased collision risks posed by accurate modern navigation systems that separate aircraft vertically, but not laterally.

Strategic lateral offset is permitted in some parts of the world, such as the North Atlantic flight corridor, where pilots can opt to fly the centreline, or offset to a parallel track either 1nm (1.85km) or 2nm to the right. This procedure was implemented to reduce risks to transatlantic aircraft in the event of unexpected altitude deviation.

Lateral offset does not exist in South America, says IFALPA But it says: “Some member associations are actively debating the benefits of this concept and may soon put forth positions encouraging use of this procedure.”

The Amazon collision has concentrated the federation’s attention on potential hazards within Brazil, and the organisation says it has received reports from pilots operating in the region which cite poor communication and procedural issues.

“Of particular concern is the method of both procedural and technical air traffic control used in Brazilian airspace and the flight information region boundary areas, compared with what pilots may be used to in other parts of the world,” says IFALPA.

Controllers are still developing experience in full-radar operations, it warns, after years of conducting non-radar procedures. This can lead to radar procedures being used even within a non-radar environment, giving an incorrect impression that flights are under radar surveillance. Scheduling methods also mean that inexperienced controllers might be given responsibility for particularly complex airspace sectors.

Revisions to flight plans might not be properly transmitted through the air traffic control system which can lead to different sector controllers having differing flight plans – meaning that pilots need to clarify any changes and confirm that the flight is proceeding under the latest clearance. The federation says that such clarification is essential to avoiding complications posed by language barriers. While some controllers possess good English pronunciation skills, it points out, this can mask their true proficiency in the language.

IFALPA, which attributes the underlying deficiencies to inadequate governmental oversight of Brazil’s airspace management, is recommending that pilots strictly adhere to ICAO-standard phraseology, ensure they are aware of all operational guidance, avoid assumptions, and even consider using high-visibility strategies – such as turning on all aircraft exterior lighting – when changing altitude.

Source: FlightGlobal.com