Northrop delivers jam‑resistant LN‑351

Aircraft usually find their position by blending GPS with onboard motion sensors, so they can keep navigating when one source gets weak. Northrop Grumman said on April 17 it delivered the first production LN-351, a jam-resistant version of that package for the F-22 Raptor and E-2D Advanced Hawkeye. (northropgrumman.com) (airandspaceforces.com) The unit’s formal name is Embedded Global Positioning System/Inertial Navigation System Modernization, or EGI-M. Northrop says it is designed to keep providing positioning, navigation and timing data in GPS-contested and GPS-denied environments. (airandspaceforces.com) (publicnow.com) In plain terms, the inertial side measures movement and rotation inside the aircraft, while the GPS side checks that estimate against satellites. If jamming or spoofing disrupts the satellite signal, the aircraft can fall back on the inertial track instead of going blind. (northropgrumman.com 1) (northropgrumman.com 2) Northrop says the LN-351 uses military M-code, an encrypted GPS signal intended to resist jamming and spoofing better than older signals. The company also says the unit has a 24-channel receiver and four navigation modes: blended inertial/GPS, inertial-only, GPS-only and Blended Navigation Assurance. (northropgrumman.com) (airandspaceforces.com) The first two aircraft named for fielding are the Air Force’s F-22 and the Navy’s E-2D. The F-22 is a stealth fighter built for high-end air combat, while the E-2D is a carrier-based command-and-control aircraft that NAVAIR calls the Navy’s newest Hawkeye variant with a major radar upgrade. (airandspaceforces.com) (navair.navy.mil) The timing follows several years of development and testing. Air & Space Forces Magazine reported Northrop began engineering and manufacturing development in 2018, completed critical design review in 2020, flew the system on a Cessna Citation 560 in May 2023 and saw additional Air Force evaluation flights in February 2025. (airandspaceforces.com) Northrop has also described desert testing at White Sands Missile Range during NAVFEST, where teams run navigation gear against simulated jamming. In that account, engineers compared systems with and without M-code receivers and anti-jam features under nighttime convoy-run test conditions. (northropgrumman.com) The company says the LN-351 is built on the older LN-251 but adds a tightly coupled design, fiber-optic gyro technology and an open architecture for software updates and third-party positioning, navigation and timing applications. Northrop says that architecture is meant to let the hardware adapt as threats and satellite sources change. (northropgrumman.com) (airandspaceforces.com) For the Pentagon, the delivery is one more step in a broader shift toward resilient navigation, where aircraft are expected to keep flying even when GPS is attacked. For Northrop, it turns a program that had been in test articles and demonstrations into a production system headed onto operational aircraft. (airandspaceforces.com) (publicnow.com)