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Joint precision approach and landing system
Joint precision approach and landing system
Joint precision approach and landing system
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LAAS architecture, similar in concept to JPALS LDGPS fixed base category

In the United States Armed Forces, the joint precision approach and landing system (JPALS) is an all-weather system for precision guidance of landing aircraft. It is based on real-time differential correction of the Global Positioning System (GPS) signal, augmented with a local area correction message, and transmitted to the user via secure means. It is used on terrestrial airfields as well as the US Navy's amphibious assault ships and aircraft carriers (hull classifications LH and CVN, respectively).

The onboard receiver compares the current GPS-derived position with the local correction signal, deriving a highly accurate three-dimensional position capable of being used for all-weather approaches via an Instrument Landing System-style display. Accuracy, while classified, is believed to be about 1 m or better. While JPALS is similar to Local Area Augmentation System, but intended primarily for use by the military, some elements of JPALS may eventually see their way into civilian use to help protect high-value civilian operations against unauthorized signal alteration.

History

[edit]
JPALS tactical prototype

The development of JPALS was the result of two main military requirements. First, the military needs an all-service, highly mobile all-weather precision approach system, tailorable to a wide range of environments, from shipboard use to rapid installation at makeshift airfields. Second, they need a robust system that can maintain a high level of reliability in combat operations, particularly in its ability to effectively resist jamming.

Operation

[edit]

JPALS encompasses two main categories: SRGPS (shipboard relative GPS) and LDGPS (land/local differential GPS). SRGPS provides highly accurate approach positioning for operations aboard ship, including aircraft carriers, helo and STO/VL carriers, and other shipboard operations, primarily helicopter operations.

LDGPS is further divided into three sub-categories: fixed base, tactical, and special missions. Fixed base is used for ongoing operations at military airfields around the world, while the tactical system is portable, designed for relatively short-term, austere airfield operations. The special missions system is a highly portable system capable of rapid installation and use by special forces.

Accuracy

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The accuracy of local area augmentation system (LAAS) is better than CAT III ILS accuracy, and will provide horizontal and vertical resolutions of less than 1 m. Although the exact accuracy of JPALS will remain classified, it's estimated that JPALS will meet or exceed this accuracy for authorized users.

Benefits

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The main benefit of JPALS is that it's a system that can be taken anywhere, anytime, providing a safe and effective way to conduct 24/7, all-weather, anti-jam instrument landing system capability to all authorized users, worldwide. A secondary benefit is a significant reduction in cost over current systems.

The naval version of JPALS transmits a signal that has a low probability of intercept; so it is unlikely that an enemy will detect the signal and trace it back to its source. The existing system, tactical air navigation (TACAN), is not encrypted or concealed in any way, which can reveal the location of the ship on which it is installed. This is not acceptable in emissions control (EMCON) or stealth conditions.

The increase in both accuracy and reliability will significantly enhance operations while reducing non-operational periods due to weather or adversarial efforts.

See also

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References

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Joint precision approach and landing system

View on Grokipedia
from Grokipedia
The Joint Precision Approach and Landing System (JPALS) is a software-based, high-integrity differential Global Positioning System (GPS) navigation and precision approach landing system designed to provide all-weather, precision guidance for military aircraft landings on aircraft carriers, amphibious assault ships, and expeditionary airfields. It utilizes real-time, dual-frequency (L1 and L2) local-area differential corrections to GPS signals, enabling ship-relative positioning with accuracy supporting Category I, II, and III approaches down to 200 feet above touchdown, while integrating with the host ship's inertial navigation system for enhanced precision in dynamic maritime environments. Developed as a joint U.S. military program since the early 1990s, JPALS addresses limitations of legacy landing systems by emphasizing interoperability, survivability, and cost-effectiveness through commercial off-the-shelf technologies compliant with Federal Aviation Administration (FAA), International Civil Aviation Organization (ICAO), and NATO standards. The U.S. Air Force leads development of the land-based (expeditionary) variant, while the U.S. Navy oversees the shipboard solution, with Collins Aerospace (formerly Raytheon) as the primary contractor since 2008. Key milestones include successful prototype testing in the 2000s for aircraft like the F/A-18, low-rate initial production (LRIP) contracts awarded in 2019, initial operational capability (IOC) declared on May 4, 2021—a year ahead of schedule—and full delivery of 23 shipboard units by March 16, 2023, with full operational capability expected by fiscal year 2026. The shipboard variant's total program cost is approximately $1.7 billion in then-year dollars, supporting enhanced sea-based combat operations under concepts like Distributed Maritime Operations. JPALS features a modular with ground- or ship-based reference stations, GPS receivers, and data links that enable up to 50 simultaneous approaches within a 20 radius, surveillance tracking out to 60 , and tactical air (TACAN) coverage up to 200 . It supports specific platforms including the F-35B, F-35C, F-35A, and MQ-25A unmanned aerial refueler, providing automatic landing capabilities, over-the-air inertial alignment, and rapid deployment options via the expeditionary variant (eJPALS), which is transportable by C-130 aircraft and operational in under 90 minutes with a crew of two. The system maintains 99% availability on carriers and amphibious ships, operates on 5,700 watts of power, and performs reliably in adverse weather, rugged terrain, and contested environments, including under GPS jamming. Operationally, JPALS has been installed on U.S. Navy vessels such as the USS Carl Vinson (CVN-70) since September 2020 and is undergoing testing for broader amphibious ship integration, with international adoption including a foreign military sale awarded to the Japan Maritime Self-Defense Force in December 2022 with deployment on JS Izumo in 2024, and installations on Italy's Cavour and the UK's HMS Queen Elizabeth. By enabling precise, hands-off landings for manned and unmanned aircraft, it significantly improves mission safety, reduces pilot workload, and supports allied interoperability in joint and coalition operations.

Background and Development

Historical Context

In the early 1990s, following the end of the , the U.S. Department of Defense recognized the need for a modernized precision approach and landing system to support joint military operations in diverse and unpredictable environments. This period saw increased emphasis on rapid deployment and among services, driven by evolving global security demands that required flexible aviation capabilities beyond traditional fixed-base operations. Discussions within the DoD highlighted shortfalls in existing landing systems, prompting the initiation of a joint program to develop a unified solution that could meet the precision guidance needs of multiple branches without relying on outdated infrastructure. The military requirements for this system centered on creating an all-service capability that was highly mobile, operable in all weather conditions, resistant to jamming, and adaptable to both shipboard decks and austere airfields. It was envisioned to support the , , , and Marine Corps by enabling safe landings for fixed-wing and rotary-wing aircraft in contested areas where electronic warfare threats could disrupt . These requirements emphasized , rapid setup by small teams, and compatibility with forward-operating bases, ensuring that forces could maintain air mobility during crisis response without vulnerability to environmental or adversarial interference. JPALS originated from adaptations of civilian Ground-Based Augmentation Systems (GBAS), such as the Local Area Augmentation System (LAAS), which provided corrections for enhanced accuracy in . Military versions incorporated heightened security features, including anti-jam protections and secure data transmission, alongside greater mobility for tactical deployment, diverging from the stationary focus of civilian implementations. Key drivers included the replacement of aging systems like Tactical Air Navigation (TACAN) and (ILS), which lacked sufficient precision and resilience in GPS-denied or contested environments, while addressing joint service needs for a standardized, GPS-based approach that promoted across platforms and with allied forces.

Program Timeline and Milestones

The Joint Precision Approach and Landing System (JPALS) program was established in the late 1990s as a joint initiative across U.S. military services to develop a GPS-based precision landing capability, with the Air Force initially leading efforts for land-based variants and the Navy overseeing shipboard solutions. Development formally began in 2008 following Milestone B approval, marking the entry into system development and demonstration for Increment 1A, the shipboard-focused phase led by the Navy. A key early milestone occurred in 2013, when the first JPALS-guided aircraft carrier landing demonstration was conducted aboard USS Theodore Roosevelt (CVN-71), validating the system's integration with carrier operations. The program encountered significant challenges, including Nunn-McCurdy cost breaches reported in 2013 due to schedule delays and scope changes, followed by a critical in 2014 stemming from reduced procurement quantities and increased unit costs exceeding 100% of original baselines. These issues led to a program restructuring certified in June 2014, which separated shipboard and land-based variants to address cost overruns and align with service-specific priorities, ultimately resolving the breaches. Progress resumed with the Engineering and Manufacturing Development (EMD) contract awarded to in September 2016 for four Engineering Development Model (EDM) units, focusing on shipboard hardware and software integration. Low-Rate Initial Production (LRIP) followed in May 2019, with the first unit installed on in September 2020. Initial operational capability (IOC) for shipboard JPALS was declared in May 2021 after successful operational testing on aircraft carriers. The U.S. Navy accepted delivery of the final JPALS unit in March 2023, completing procurement of 23 LRIP systems ahead of schedule and enabling broader fleet integration. Deployment to international partners advanced with Japan's purchase of one unit in 2022 and plans to install it on JS Izumo in 2024, supporting F-35B operations. As of 2025, JPALS has achieved full operational deployment across U.S. aircraft carriers and amphibious assault ships, supporting F-35B/C and other in all-weather conditions, with full operational capability targeted for 2026. The expeditionary variant (eJPALS), a portable system for tactical land-based use, remains in testing and demonstration phases, with successful field setups completed as early as 2019, including a three-week demonstration at in June 2021 supporting F-35B operations, and ongoing evaluations for Marine Corps integration. Future increments include enhanced integration with unmanned systems, such as the MQ-25A , and improved anti-jam capabilities to counter GPS threats, with these upgrades planned for incorporation by 2030 to ensure resilience in contested environments.

System Design and Components

Core Components

The Joint Precision Approach and Landing System (JPALS) consists of a ground subsystem and an airborne subsystem, designed as modular hardware and software elements that enable high-integrity navigation. The ground subsystem includes GPS reference receivers that monitor satellite signals to generate precise positioning data, differential correction processors that compute real-time corrections for GPS inaccuracies, and VHF/UHF data broadcast antennas that transmit these corrections securely to approaching aircraft. The airborne subsystem features GPS receivers installed in compatible aircraft, such as the F-35 variants and MQ-25A, which receive and apply the ground-based differential corrections to enhance navigation accuracy during approach. These receivers integrate with the aircraft's flight management systems, allowing seamless incorporation of JPALS data into and guidance functions. JPALS employs a modular open-system (MOSA) for both hardware and software, facilitating upgrades, cost-effective sustainment, and integration with existing shipboard systems through non-proprietary interfaces and components. Secure communication protocols are integral to the system, utilizing low-probability-of-intercept (LPI) signals for data transmission and anti-jam capabilities via dual-frequency (L1/L2) GPS processing to protect against electronic threats. The components are ruggedized to withstand shipboard vibrations and austere field conditions, with power requirements met by standard 115 VAC/60 Hz ship's electrical systems, and integrate with the host ship's inertial navigation system to maintain functionality in dynamic environments.

Variants and Configurations

The Joint Precision Approach and Landing System (JPALS) includes multiple variants and configurations tailored to diverse operational environments, ranging from maritime to expeditionary land settings, to ensure precision guidance for landings. The Shipboard Relative GPS (SRGPS) variant is specifically optimized for nuclear-powered carriers (CVN) and amphibious assault ships (LHA/LHD), delivering relative positioning accuracy aligned with the dynamic motion of the landing deck. Land Differential GPS (LDGPS) fixed base configuration supports permanent installations at airfields, seamlessly integrating with established to provide reliable differential corrections. In contrast, the LDGPS tactical configuration features portable units designed for expeditionary airfields, enabling deployment in hours by teams as small as two personnel. The LDGPS special missions variant, demonstrated as ultra-portable, man-portable units—such as backpack-sized systems—in 2013 for at remote or austere sites, leveraging JPALS hardware for rapid setup in contingency scenarios. The Expeditionary JPALS (eJPALS) represents a lightweight, ground-based adaptation for rapid deployment and unmanned operations, with demonstrations and testing initiated since 2020 to support austere environments. Across these configurations, JPALS maintains compatibility with all future manned and unmanned tactical , including support for operations under restricted emission control (EMCON) conditions, while drawing on shared core components like GPS receivers.

Operational Principles

How JPALS Works

The Joint Precision Approach and Landing System (JPALS) operates as a differential (GPS)-based navigation aid that delivers real-time precision guidance for during approach and landing phases. The process begins at the ground station, which continuously monitors GPS satellite signals using reference receivers to establish a known position, computes errors such as those caused by atmospheric delays and satellite clock inaccuracies, and generates differential to enhance positional accuracy. These are then broadcast via a VHF to approaching , enabling the system to function in diverse environments including degraded or contested conditions. Upon reception, the aircraft's onboard avionics capture the VHF-transmitted corrections through standard antennas, integrating them with the aircraft's GPS receiver to calculate a highly precise position relative to the runway or carrier deck. This corrected position data is processed in real time, allowing the system to provide lateral and vertical guidance cues displayed to the pilot or fed directly to the autopilot for automated control. The guidance supports approaches equivalent to Category III Instrument Landing System (ILS) standards, facilitating hands-off landings where the aircraft follows a predefined glide path from as far as 10 nautical miles out. JPALS integrates seamlessly with the aircraft's inertial navigation system (INS) to maintain continuity during potential GPS signal outages, blending INS-derived data with differential GPS inputs for redundant positioning. In shipboard operations, a dedicated ship-relative mode dynamically adjusts guidance to account for the vessel's motion, including pitch, roll, and yaw, by coupling with the ship's INS to ensure the approach path aligns with the moving deck. For enhanced security, the system employs emission control features, including silent operational modes that utilize directional VHF antennas to limit signal detectability and reduce vulnerability in hostile environments.

Precision and Accuracy

The Joint Precision Approach and Landing System (JPALS) achieves horizontal and guidance accuracy of less than 1 meter, with the exact value classified for security reasons. This precision enables reliable aircraft positioning during critical landing phases. For sea-based operations, JPALS integrates the ship's to deliver accuracies of less than 6 inches, compensating for deck motion and environmental challenges. Key error sources in JPALS include ionospheric scintillation and multipath interference, which can distort . Ionospheric effects are mitigated through dual-frequency processing using L1 (1575.42 MHz) and L2 (1227.60 MHz) carrier-phase measurements, allowing cancellation of ionospheric delays and robust ambiguity resolution for centimeter-level precision. Multipath errors, particularly severe in shipboard environments, are minimized via controlled reception pattern antennas (CRPAs) with digital , which steer nulls toward reflectors and reduce phase variations to as low as 1.8° standard deviation through calibration. These mitigations ensure undetected navigation errors remain below a 1-meter alert limit. JPALS performance standards surpass those of Category III (ILS), which operates with a 50-foot decision height, by enabling fully coupled automatic landings in all weather conditions with greater than 99.9% availability. Compared to legacy Tactical Air Navigation (TACAN) systems, which offer 1-2 positional accuracy, JPALS provides orders-of-magnitude superior precision while maintaining functionality under jamming through CRPA anti-jam antennas and digital , rejecting interference up to 50 dB. In jamming scenarios, relative between satellites and jammers is optimized to preserve carrier-phase integrity. Testing in 2013 carrier trials aboard USS Theodore Roosevelt demonstrated JPALS accuracy of 0.5-1 meter, with a project incentive test achieving 20 cm or better touchdown dispersion after 20 consecutive F/A-18C landings. Ongoing validation efforts confirm compatibility for unmanned operations, supporting systems like the MQ-25A with two-way datalink for precision equivalent to manned flights.

Applications and Advantages

Military Applications

The Joint Precision Approach and Landing System (JPALS) primarily supports U.S. aircraft carriers, including Nimitz-class and Gerald R. Ford-class vessels, by providing GPS-based precision guidance for such as the F-35C Lightning II. It is also integrated on amphibious assault ships, like the Wasp-class and America-class, to enable Marine Corps F-35B short takeoff and vertical landing operations, with deployments supporting aviation missions since 2016. For the U.S. , the expeditionary variant (eJPALS) facilitates landings at tactical airfields in austere locations, allowing rapid setup by two personnel in under 90 minutes from a C-130 transport. In joint operations, JPALS enhances and Marine Corps expeditionary landings by supporting distributed forces in remote environments, where eJPALS can handle up to 50 simultaneous approaches within a 20-nautical-mile radius for multiple points. This capability aids rapid airfield establishment at forward bases, enabling seamless integration of naval, air, and ground assets during multinational exercises or contingency responses. Additionally, JPALS integrates with unmanned systems, such as the MQ-25A unmanned aerial refueler, which relies on the system for autonomous carrier landings following in-flight refueling missions, with successful simulations completed in and shipboard integration planned for 2026. Internationally, JPALS has been deployed to allied forces, including units installed on the UK's HMS Queen Elizabeth (certified April 2021) and Italy's ITS Cavour (installed March 2021), as well as a unit delivered to the Japan Maritime Self-Defense Force in 2023 for installation on the Izumo-class helicopter destroyer JS Izumo by 2024, enhancing F-35B compatibility and Indo-Pacific interoperability. The system aligns with NATO standards through coordination on differential GPS protocols, as outlined in STANAG 4392, supporting potential compatibility for coalition operations. Operationally, JPALS enables night and all-weather aircraft recoveries on carriers and amphibious ships in contested maritime environments, such as distributed operations in the Philippine Sea, while eJPALS supports quick-relocation scenarios at contested forward airfields to counter threats like cruise missiles.

Benefits and Limitations

The Joint Precision Approach and Landing System (JPALS) enables 24/7 all-weather operations, allowing aircraft to conduct safe precision landings in extreme weather and low-visibility conditions that would otherwise restrict or halt flight activities. Its modular design reduces lifecycle costs by minimizing maintenance and support requirements through the use of a single ground station per airfield, in contrast to legacy systems that demand multiple installations. JPALS enhances safety by supporting automatic, hands-off landings via autopilot integration, improving pilot situational awareness and reducing human error risks during critical phases of flight. Additionally, its low probability of intercept (LPI) and anti-jam features ensure survivability in electronic warfare environments, with demonstrated success in maintaining landing accuracy under severe GPS jamming scenarios. JPALS achieves cost savings by replacing multiple legacy systems, such as the (ILS) and Tactical Air Navigation (TACAN), thereby lowering acquisition, installation, and operational expenses across military platforms. Despite these advantages, JPALS remains dependent on , which are vulnerable to jamming and spoofing, although mitigations like interference suppression technologies and controlled reception pattern antennas help address these risks. The program has faced high initial deployment costs, including a critical Nunn-McCurdy breach in 2014-2015 due to unit cost increases exceeding 100 percent from the original baseline, driven by scope expansions and reduced procurement quantities. Functionality is limited to aircraft and ships equipped with compatible receivers, restricting its use to modernized platforms. Overall, JPALS improves sortie generation rates and aircraft availability in poor visibility by enabling more reliable operations and reducing downtime from weather-related delays, thereby supporting enhanced power projection in joint theater environments. Its precision exceeds that of traditional ILS systems, further contributing to operational efficiency.

References

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  2. https://www.navair.navy.mil/jpals
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  4. https://www.esd.whs.mil/Portals/54/Documents/FOID/Reading%20Room/Selected_Acquisition_Reports/FY_2021_SARS/22-F-0762_JPALS_SAR_2021.pdf
  5. https://apps.dtic.mil/sti/tr/pdf/ADA534677.pdf
  6. https://www.naval-technology.com/news/us-last-jpals-f35-aircraft/
  7. https://www.navair.navy.mil/news/US-Navy-partners-Japan-Maritime-Self-Defense-Force-deliver-JPALS-equipment/Tue-02072023-1436
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  11. https://www.esd.whs.mil/Portals/54/Documents/FOID/Reading%20Room/Selected_Acquisition_Reports/FY_2022_SARS/JPALS_SAR_DEC_2022_final.pdf
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  14. https://www.rand.org/pubs/monographs/MG1171z8.html
  15. https://www.esd.whs.mil/Portals/54/Documents/FOID/Reading%2520Room/Selected_Acquisition_Reports/FY_2014_SARS/15-F-0540_JPALS_Inc_1A_SAR_Dec_2014.PDF
  16. https://www.navy.mil/Press-Office/News-Stories/Article/2621944/navy-declares-initial-operational-capability-for-joint-precision-approach-and-l/
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  24. https://www.af.mil/News/Article-Display/Article/123694/precision-landing-system-ready-for-take-off/
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  26. https://apps.dtic.mil/sti/pdfs/AD1016049.pdf
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  29. https://enac.hal.science/hal-01021724/document
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  33. https://www.esd.whs.mil/Portals/54/Documents/FOID/Reading%2520Room/Selected_Acquisition_Reports/FY_2021_SARS/22-F-0762_JPALS_SAR_2021.pdf
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  35. https://www.flightglobal.com/military-uavs/us-navy-to-fly-mq-25-from-aircraft-carrier-in-2026/164268.article
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  37. https://ieeexplore.ieee.org/document/4745656/
  38. https://www.gao.gov/assets/gao-13-396.pdf
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