Radar mountings in the nose of the Lockheed Martin F-35 fighter are different for the current AN/APG-81 by Northrop Grumman and the future AN/APG-85 radar, also by Northrop Grumman–a difference which has helped complicate fielding of the new radar which was to deliver with F-35 Lot 17 but may now instead deliver later, possibly in Lot 20 in the next two years.
“The APG-81 is different than the APG-85, and therefore delivering the aircraft, as currently configured, with an APG-85 radar versus an APG-81 radar is challenging,” Rep. Rob Wittman (R-Va.) said in an interview off the House floor on Feb. 3.
“The bulkhead configuration is key because for both of the radars, they are very different,” he said. “Remember, the bulkhead configuration allows the placement of the radar towards the attitude of the array, and the attitude of the array makes all the difference in the world about how the radar operates.”
A dual mount to accommodate either the APG-85 or the APG-81 would take two years to field, a source told sister publication Defense Daily.
“I know all about it, but the delivery of the aircraft is classified,” Wittman said when asked whether he knew if it were true that Lockheed Martin has been delivering F-35s to the military services since last June without radars, including all F-35As. “I can’t speak to the condition of the aircraft so you’ll have to go to the Air Force, the customer, and ask them about that.”
Wittman, the chair of the House Armed Services Committee’s Tactical Air and Land Forces panel, has been bird-dogging the F-35 program and the contractor team since the fall of 2024 on delays in the delivery of the APG-85, including what he said have been monthly phone calls since then with the head of the F-35 program executive office. Marine Lt. Gen. Gregory Masiello became the F-35 program executive officer in July last year. He succeeded Air Force Lt. Gen. Michael Schmidt, now retired, who served as the head of the F-35 Joint Program Office between July, 2022 and July, 2025.
“I spoke to Lockheed yesterday, and they’re working with Northrop to get APG-85 delivered even faster,” Wittman said on Feb. 3. “They’re doing some things to try and integrate it with Technology Refresh-3 [TR-3] and Block 4.”
Nearly a year and a half ago, Wittman said that he had met with Northrop Grumman to discuss the need to reduce test time for the APG-85, which he said had increased from three days to 78 days—part of a wider set of challenges involved in building a Gallium Nitride-based radar needing upgraded cooling and power in the F-35’s nose.
Wittman said that “they’ve condensed the testing regime” and “have been able to truncate some of those things” to accelerate delivery. “We’ve been on Lockheed, as well as Northrop to continue to compress the schedule,” he said. “I’d like to see them compress it even more. I think they can do that.”
The APG-85 is to deny adversary use of the electromagnetic spectrum and to allow better weapons accuracy and targeting of adversary airborne and surface radars at greater ranges.
“It’s an incredibly advanced radar,” Wittman said of the APG-85. “The arrays on it give it much more power which is why we have to upgrade the engine. I think we need about 82 kilowatts of power versus what it’s producing right now. The APG-85 is key to Block 4, and it’s key to TR-3 software upgrade capabilities and integration with the imaging system, the Distributed Aperture System.”
More than two and a half years ago, now retired Air Force Lt. Gen. Richard Moore, then the service’s deputy chief of staff for plans and programs, said that “we are getting very close to the new radar on the F-35” and that the APG-85 would be “a dramatic increase in our ability” over the APG-81 radar, which Northrop Grumman builds in Linthicum, Md.
“It’s my hope they do it [delivery of APG-85] as fast as humanly possible and have the system perform,” Wittman said on Feb. 3. “I don’t want it delivered, if it’s gonna be operationally deficient because then the aircraft sits on the tarmac.”
F-35 deliveries to U.S. units in the field since last June have had the APG-85 mountings, which do not fit the APG-81. But, the radar-less F-35 deliveries have not affected sales to foreign partner nations which have the APG-81 on their jets, the source said, adding that, without a radar, there had to be additional weight added in the nose for aircraft balance during flight. Radar-less F-35s have been able to fly, as long as they are accompanied by other F-35s, data linked and equipped with the APG-81, the source said.
On Feb. 3, an Air Force spokeswoman said that the Air Force’s, Navy’s, and Marine Corps’ joint development and integration of the advanced APG-85 will help defeat “current and projected adversarial air and surface threats.”
“This advanced radar will be compatible with all variants of the F-35 aircraft,” according to the Air Force. “Due to program security reasons, we are protecting any additional information with enhanced security measures.”
F-35 deliveries restarted in July 2024 after a halt in late 2023 due to software problems with TR-3, which is to allow the integration of dozens of new sensors and weapons for the Block 4 upgrade.
In January 2023, Northrop Grumman disclosed the development of the APG-85 for Block 4 F-35s beginning with Lot 17, but the company and the F-35 program have not revealed funding levels nor contract details for the radar.
A version of this story originally appeared in affiliate publication Defense Daily.