B-21 Inlet Problem Was Resolved Before Design Freeze, RCO Says

A redesign of the inlet on the Northrop Grumman B-21 was completed before the final configuration of the stealth bomber was frozen in November 2018, according to the U.S. Air Force. 

The timing of the redesign before the critical design review in November 2018 supports the Air Force’s claim that the “major redesign” on the inlet subsystem, described by Rapid Capabilities Office (RCO) director Randall Walden, had no impact on the cost and schedule of the program. 

The design problem was first publicized in March 2018 by Rep. Rob Wittman, then chairman of the strategic forces subcommittee on the House Armed Services Committee. Wittman described an ongoing debate between Northrop and Pratt & Whitney engineers over the size of the inlet, which determines the volume of air entering the engine to generate thrust when compressed, mixed with fuel and ignited. 

But the debate was settled before the critical design review (CDR) was completed in November, according to a statement by the RCO. The CDR “established the weapon system design baseline, inclusive of resolving identified technical challenges,” the RCO said. 

“Further details are classified, but the B-21 program remains on track to the government’s baseline for cost and schedule established at contract award,” the RCO added.