How Do Airliners Navigate the North Atlantic?

Today, inertial reference systems (IRSs) that include laser-ring gyros operate within three separate onboard inertial reference units (IRUs).

Les Abend

Wednesday, December 06, 2023 at 07:31 AM ET

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Navigating over the North Atlantic has changed a lot since the days when Lindbergh first made the flight. [Adobe Stock]

Key Takeaways:

Modern transport-category jets have replaced traditional navigation methods like sextants and older inertial navigation systems (INS) with advanced Inertial Reference Systems (IRSs).
These IRSs utilize laser-ring gyros and integrate position data from GPS, VOR, and DME for highly accurate real-time positioning.
Two interconnected Flight Management Computers (FMCs) process this combined data, providing redundancy that allows for continued, albeit sometimes restricted, navigation even with component failures.

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Question: How do transport-category jets navigate the North Atlantic?

Gone are the days of navigating with a sextant. Until the early 1980s, my former airline actually utilized a sextant viewing port aboard the Boeing 707 as a secondary means of verifying position. This remained until the airplane was retired from service. Even inertial navigation systems (INSs) have virtually become extinct. Today, inertial reference systems (IRSs) that include laser-ring gyros operate within three separate onboard inertial reference units (IRUs).

Position data from the IRUs is combined with GPS position, VOR position, and DME position. The combined data is processed by two separate flight management computers (FMC) that communicate with each other to provide a more accurate real-time position in addition to numerous other complex functions.