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 navigate the North Atlantic using advanced Inertial Reference Systems (IRS) with laser-ring gyros, replacing older sextant and Inertial Navigation Systems (INS) methods.
Current navigation relies on multiple onboard Inertial Reference Units (IRUs) combining data from GPS, VOR, and DME, processed by redundant Flight Management Computers (FMCs) for precise real-time positioning.
The system incorporates redundancy, allowing for continued, though restricted, navigation even with failures in some IRU or FMC components.

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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.