F-35 Modifications

The F-35 Modifications program for the Air Force is a comprehensive effort aimed at sustaining, enhancing, and standardizing the operational fleet of F-35A Conventional Take Off and Landing (CTOL) aircraft. The program's overarching goals are to correct documented deficiencies, implement capability upgrades, and address reliability, maintainability, and lifecycle cost concerns. Modifications are executed through field and depot retrofits, ensuring that both early production and newer aircraft converge toward a common configuration as the F-35 program evolves. The program is managed by the Air Force in coordination with the Joint Strike Fighter (JSF) Program Office and involves multiple agencies and contractors, including Lockheed Martin and Pratt & Whitney.

Block Upgrade Modifications (Block 3i, 3F, and Block 4) focus on bringing earlier Low Rate Initial Production (LRIP) aircraft up to the latest operational standards. Block 3i and 3F upgrades involve hardware and software retrofits, such as new radar modules, integrated core processors, and electronic warfare modules, to avoid the logistical and cost challenges of maintaining multiple configurations. Block 4 modifications, implemented through a Continuous Capability Development and Delivery approach, introduce advanced capabilities like Technical Refresh 3 (TR-3), Next Generation Distributed Aperture System (DAS), enhanced cooling, and modernized electronic warfare systems. These upgrades are essential for maintaining fleet lethality and survivability against emerging threats. Block 4 modifications are scheduled to lag production by one year to mitigate technical risks.

Concurrency and Correction of Deficiencies lines address issues discovered after aircraft acceptance and production concurrency with ongoing development. The Concurrency line funds retrofits to correct deficiencies tied to the Joint Contract Specification, such as the Digital Tuner Insertion Program (DTIP), which enables compatibility with TR-3 upgrades and standardizes the training and combat fleets. The Correction of Deficiencies line is primarily focused on the Structural Life Limited Parts (SLLP) program, which removes flight hour limitations by retrofitting components to extend aircraft life from below 4,000 hours (SLLP2) to 8,000 hours (SLLP3). This effort involves numerous Engineering Change Proposals (ECPs) and is supported by expanded depot capacity at Ogden Air Logistics Complex.

Propulsion Modifications are designed to improve the reliability, maintainability, and availability of the F-35A's F135 engine, reduce lifecycle costs, and address production deficiencies and obsolescence. Key initiatives include redesigns of the mid bearing compartment scavenge tube, multi-attitude deaerator gearbox, fuel pump gear retrofits, nozzle linkage durability improvements, and harness bracket mistake-proofing. These modifications are implemented at the depot level, with material procured from Pratt & Whitney and installation managed by Air Force organic depots.

Reliability and Maintainability (R&M) Modifications target readiness degraders that impact the cost per flight hour and overall fleet availability. The program identifies and incorporates ECPs to address critical R&M issues as they arise, with installations performed by field mod teams and depots. The goal is to achieve significant improvements in platform reliability and reduce maintenance costs over the aircraft's lifecycle. Cost growth in this area is primarily driven by increased quantities and updated depot installation costs.

Each modification line item within the F-35 Modifications program is justified by the need to maintain a capable, safe, and standardized fleet that can meet current and future operational requirements. The program supports a Total Active Inventory of aircraft, with funding levels adjusted annually based on the number of aircraft inducted for modification and the scope of required upgrades. This approach ensures that the Air Force's F-35A fleet remains technologically advanced, operationally effective, and cost-efficient throughout its service life.