Lockheed redesigning F-35 fuselage

[Zaphod58]

Due to apparently delays in development of the new APG-85 radar for the F-35, Lockheed is working on a redesign of the forward fuselage. The change would come starting in Lot 20, and would allow for aircraft to be fitted with the APG-81, with a later refit of the APG-85 with minimal changes having to be made to the aircraft. It also allows for the APG-85 to be fitted from the production line if it's ready in time.

The original plan was to begin refits of the APG-85 with Lot 17, which is in production now. Northrop told the JPO and Lockheed that the development timeline of the APG-85 was very aggressive as it is a big change and technological leap and it was going to take time to develop. Both times they pushed back against the timeline both the JPO and Lockheed pushed for them to stick to the timeline. As a result Lockheed is now buying long lead items for the APG-81 as far out as Lot 20, with Northrop paying for 25% of the costs for the items.

WASHINGTON — The Pentagon has maintained that a new radar for the F-35 would be ready for the plane’s Lot 17 airframes, which began production this year. But the CEO of F-35 prime contractor Lockheed Martin has quietly warned the Air Force of “risks” in the radar’s delivery schedule, leading the defense giant to craft workarounds that currently center on Lot 20, according to a letter obtained by Breaking Defense.
To mitigate potential delays, Lockheed is proposing redesigning the aircraft’s forward fuselage to be capable of accommodating either the aircraft’s incumbent radar, the APG-81, or the new radar dubbed the APG-85. The fresh fuselage design could enter service in the program’s Lot 20 production, Lockheed CEO Jim Taiclet wrote in the letter.
The letter does not say the cause of the potential delays — stakeholders declined to tell Breaking Defense — nor does it say what the fate of the radars for Lot 17, 18 and 19 is expected to be.

https://breakingdefense.com/2025/06/excl...ge-design/

[Signal Witch]

For those unfamiliar with these two systems:

 The APG-81 is the radar that’s been flying on all F-35 variants since the beginning. It’s a solid AESA system, derived from the APG-77 on the F-22, and it handles air-to-air and air-to-ground roles well. It’s got synthetic aperture radar imaging, good EW support, and can track moving ground targets, so it's no slouch. But it’s also a product of early 2000s design, and while it's still capable, it's starting to show its limits with all the new threats and weapons systems coming online.
 
That’s where the APG-85 comes in. It’s part of the Block 4 upgrade and is being built to handle the kind of high-demand, high-threat environments the F-35 is expected to face going forward. It has more processing power, better cooling, faster scanning, and improved resolution and range. It's designed to spot tougher targets, work better in contested electronic environments, and fuse data more effectively with other sensors. It’s also being built with future weapons in mind, especially long-range or hypersonic stuff.

In short, the 81 is still very good but the 85 is being developed because the battlespace is changing fast, and the F-35 needs to keep up.