Northrop Grumman B-21 begins engine runs

The Northrop Grumman B-21. (Northrop Grumman)

Northrop Grumman has commenced engine runs of the B-21 Raider bomber for the first time, the US Air Force (USAF) announced on 12 September.

The first engine run took place at Northrop Grumman's Palmdale, California, factory where the aircraft was built. Further details, including whether the engine runs involved a single engine or both engines, were not immediately available.

“Engine testing is an essential milestone for the program as the world's first sixth-generation aircraft continues on the path to flight test,” Northrop Grumman said in a statement. “The B-21's first flight will remain a data-driven event that is monitored by Northrop Grumman and the United States Air Force,” the company added.

The twin-engine B-21's powerplants are widely thought to be descended from Pratt & Whitney's F135, which powers the Lockheed Martin F-35, but neither the USAF nor Northrop Grumman has disclosed the engines' type or specifications.

Details about the B-21's progression to flight test have been scarce. Northrop Grumman CEO Kathy Warden disclosed in July that the aircraft's electrical systems had been switched on, and the company's programme manager told Janes in December 2022 that two B-21s had been completed – T-1, which is intended to conduct the first flight, and G-1 for ground testing – and that four more were in final assembly at the Palmdale factory. Which aircraft conducted the first engine run has not been publicly released.

The B-21's rollout and subsequent pictures have shown only the front of the aircraft, lest the world glimpse its planform.

The B-21 is scheduled to conduct its first flight in late 2023, with initial operational capability scheduled for 2025, although delays are common for new aircraft programmes.