By Graham Warwick in Washington DC
Northrop Grumman has begun flight testing a new active-array antenna on the B-2 stealth bomber as the US Air Force rushes to change the radar’s Ku-band frequency to avoid interference with commercial signals from 2007.
Concurrency between testing of the Raytheon active electronically scanned array (AESA) and modification of operational B-2s to meet the deadline means Northrop will have to clear the radar modes in increments. Mode Set 1 is the “absolute minimum to go to combat”, while the remaining modes will follow in Set 2, says Dave Mazur, vice-president long-range strike.
The initial block of modes has been further divided. Set 1a, which is almost complete, provides demonstration modes only for training while the same “bare-bones” modes are fully qualified as the go-to-combat Set 1b. While the radar is still being tested, “development unit” arrays are being built to allow the modification of operational B-2s to begin. The concurrency makes it “a risky programme”, says Mazur.
Northrop and Raytheon are working on the AESA upgrade under a $382 million system development and demonstration contract awarded in 2004. Two engineering development model arrays have been installed in air vehicle 3, the B-2 used for flight testing at Edwards AFB in California.
The AESA replaces the existing passive electronically scanned antenna, its array of Ku-band transmit/receive modules allowing the original radar’s travelling wave-tube transmitter to be removed, reducing weight and improving reliability. Structural and software changes are minimal and existing modes are retained, although Northrop is pushing for funds to upgrade the processor take advantage of the AESA’s capability.
Shifting the radar frequency required changes to “a couple of items” on the aircraft that were sensitive to interference, Mazur says.
Source: Flight International
