B-2A stealth bomber radar upgrade on hold for redesign

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Northrop Grumman has confirmed that flight tests for a $900 million radar antenna upgrade for the B-2A stealth bomber have been on hold for nearly a year to give engineers time to redesign the system.

The nearly year-long test delay means the US Air Force must request waivers to allow the B-2A fleet to legally operate in the part of the spectrum occupied by its current mechanically scanned radar - the ALQ-181, Northrop says.

That part of the spectrum in the Ku-band was redesignated about a decade ago for commercial use. This action forced the air force to upgrade the B-2 with an antenna designed to transmit at a non-interfering frequency within the same band.

The original schedule called for entering production of the new AESA system in late 2007, as the spectrum was expected to be transferred to commercial users from 2007 to 2010.

"There is a waiver in place that allows the air force's legacy B-2 radar to continue operating in the 'old' frequency band on a non-interference basis," Northrop says.

In 2003, the air force selected a Raytheon-made Ku-band active electronically scanned array (AESA) for the upgrade programme. The antenna is being upgraded, but the quality of the radar product will remain the same because the ALQ-181's back-end processor is left unchanged.

Flight tests are expected to resume within about one month after the nearly year-long hiatus, says Northrop. The air force, meanwhile, is working to submit a new development and production schedule that accounts for the flight-test delay and the redesign of the antenna.

The flight tests were halted last year for reasons that remain undisclosed. The AESA antenna is among the first to operate in the Ku-band, and must be designed in a way that preserves the B-2's unique low-signature profile for radar.

Raytheon is also manufacturing a host of X-band AESA radars for tactical and strategic aircraft, including the APG-63(V)3 for the Boeing F-15 and the APG-79 for the Boeing F/A-18E/F.