Congress has docked the F-35 program for delays in the Block 4 upgrades for the fighter, but it well may be that some of the envisioned Block 4 features will move to the U.S. Air Force’s future Collaborative Combat Aircraft.

“Block 4 will ensure F-35 relevance in a high-end fight against our peer competitors,” the Air Force wrote in an Aug. 29 email in response to questions on Block 4.  “The Air Force expects Full Block 4 capability in Lot 20, which delivers in 2028. The Air Force continues to evaluate potential capabilities for an unmanned Collaborative Combat Aircraft.”

Technology Refresh 3 (TR3) is the computer backbone for Block 4, which is to have 88 unique features and to integrate 16 new weapons on the F-35. A big challenge, however, for TR3 is the L3Harris [LHX] integrated core processor, and the Government Accountability Office has been concerned by the possibility of further delays in processor deliveries and by the poor software quality for Block 4.

The Air Force’s fiscal 2023 budget curtails the planned buy of F-35As from more than $5 billion sought for 48 planes in fiscal 2022 to about $4.5 billion for 33 F-35As in fiscal 2023. Both House and Senate appropriators have signed off on the request for 33 F-35As in fiscal 2023.

In May, Air Force Secretary Frank Kendall told the House Appropriations Committee’s defense panel that the Air Force is “very interested and insistent on getting the Block 4 capabilities for F-35, and the contractor has been late in delivering them so far so we want to see evidence that he’ll be able to accomplish that before we increase the production” (Defense Daily, May 13).

The F-35 program has said that the fighter will need a new or significantly upgraded engine with improved electrical power and cooling capacity to accommodate the 53 new capabilities slated for Block 4.

Block 4 may cost $15 billion, while the Air Force has pegged the development cost of a new, Advanced Engine Transition Program (AETP) power plant for the F-35 at $6.7 billion (Defense Daily, June 30).

“While ‘Block 4’ capabilities are probably needed, it doesn’t necessarily mean all 53 capability improvements need to be squeezed into the F-35,” retired Air Force Lt. Col. Mike “Pako” Benitez, the former director of staff for the Air Force 53rd Wing, the service’s primary operational test wing, wrote in the latest edition of his newsletter, The Merge. “Moving some of the power/cooling-hungry capabilities to a Combat Collaborative Aircraft would permit full-yet-distributed ‘Block 4’ capabilities in a manned-unmanned team without the expense of a new F-35 engine.”

The Air Force’s fiscal 2024 budget request early next year is expected to lay out the service’s path forward on F-35 engines.

Raytheon Technologies‘ Pratt & Whitney [RTX] builds the current F135 engine for the fighter.