Feb. 4, 2016

Air traffic controllers officially implemented reduced lateral separation minimums (RLatSM) on the North Atlantic Tracks on Dec. 14, 2015, but not all operators flying from North America to Europe may be aware of the details of the new operating rules.

RLatSM reduces the lateral spacing between aircraft in the tracks from one degree (60 nautical miles) of longitude to half a degree (25 nautical miles).

“The authorities essentially took the two core tracks, and laid a third track between them, using the new 25-nautical-mile spacing,” said Chris Strand, an international captain for Amway and vice chairman of NBAA’s International Operators Committee.

Now that RLatSM is effective, all major air routing providers have added half-degree waypoints to their published charts and flight planning systems. Aircraft must be certified for RNP4, CPDLC and ADS-C to fly in the three core tracks.

Update Contingency Plan

Most business aircraft fly above the tracks, at 43,000 feet or higher. The new spacing only applies to flight levels 350 to 390 inclusive. And, as operators have reported to the International Operators Committee, Gander Center is not assigning routes with half-degree waypoints unless operators specifically request them in their flight plan.

However, the North Atlantic is the world’s busiest oceanic airspace, and it’s not uncommon for business aircraft operators to file flight plans that overlay the tracks from above, to get the best winds.

“Flying an overlay simplifies your contingency planning, while flying a route that cuts across the published tracks makes it more difficult,” said Craig Hanlon, chief pilot on the G550 for DuPont Aviation and chair of NBAA’s International Operators Committee. “It can be like driving in the left lane of a big freeway, with your exit on the right, and having to merge across seven lanes of traffic.”

The International Operators Committee has received anecdotal reports from Gander Center that most aircraft operators are not yet comfortable with RLatSM procedures and haven’t trained for them.

“Even if operators fly above the tracks, they need to have a plan to get down between the tracks if they lose an engine or pressurization,” said Strand. “With the half degree of separation, you need to increase your situational awareness. At every point along your route, you should know where the tracks are in reference to your position if you have to divert.”

Confusion with Waypoint Naming Convention

RLatSM is still relatively new, and the committee said some have been confused by the convention for identifying half-degree waypoints. Some air routing providers are using an ‘H’ prefix, while others are using an ‘N’ prefix for half-degree waypoints.

Following the ‘N’ prefix convention, a one-degree waypoint would be represented as “5230N,” and a half-degree waypoint would be “N5230,” which could be confusing. In NAT Ops Bulletin 3/15 Revision 1, the International Civil Aviation Organization has recommended use of the ‘H’ prefix.

“Both naming conventions work in our flight management system (FMS),” said Hanlon. “But it can be confusing if the flight plan loaded in your FMS is using a different convention than the enroute chart you’re looking at.”

The International Operations Committee will present a regional update on North Atlantic airspace, as well as information on avionics integration, at the International Operators Conference, March 21 to 24 in San Diego, CA. Learn more about NBAA’s International Operators Conference and register.