Northrup Grumman B-2 Upgrades.

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From Aviation Week Magazine.


7 Aug Close


By Guy Norris


A fresh wave of structures, systems and weapons upgrades is being rolled into the Northrop Grumman B-2 as part of efforts to keep the stealth bomber in the front line to 2050 and beyond.

The drive to sustain the 20-strong fleet enjoys “good support across the board” says Brig. Gen. Robert Wheeler, commander of the 509th Bomb Wing at the B-2’s home at Whiteman AFB, Mo. The case for injecting new life into the B-2 was unquestionably bolstered by U.S. Defense Secretary Robert Gates’s April decision to ax the next-generation bomber project, ambitiously aimed at fielding a new aircraft in 2018. But Wheeler adds the stealth bomber was always part of the equation.

“Even if the next-generation bomber came along, we were always going to be part of the fight.” The upgrade plan evolved for the B-2 is “designed to look to the threats of the future and that’s the plan we have right now. We are exactly on that plan,” he adds. The effort builds on key avionics and systems enhancements, plus new weapons capabilities and initiatives to sustain the low-observable structure and skin.

“We are building a new aircraft from the inside out,” says Col. Kevin Harms, commander of the 702nd Aeronautical Systems Group at Wright-Patterson AFB, Ohio. “We didn’t have the means to remake the aircraft itself but we’ve put together a very strategic plan. The original aircraft design is quite flexible and, although it was originally designed as a nuclear bomber, it has migrated and become a multirole aircraft and we see that continuing as we go forward.”

A key upgrade recovering from a slow start is the delayed B-2 radar modernization program (RMP). Under the RMP, the mechanically scanned antenna of the Raytheon APQ-181 Ku-band multimode navigation and attack radar is being replaced with an active electronically scanned array (AESA). The effort is now well underway, with five aircraft expected to be flying by year-end. Northrop Grumman, which manages the RMP, was awarded a $382-million system development and demonstration (SDD) contract by the Air Force in 2004.

Integration and other issues stalled the RMP and forced Northrop Grumman and El Segundo, Calif.,-based Raytheon Space and Airborne Systems to set up a “tiger team” to get the effort back on track, says Northrop Grumman vice president and B-2 program manager Dave Mazur. “A lot of decisions were being made and technical risks being pushed down the road to meet a ‘need date,’ so we basically said ‘let’s stop and re-group,’” he adds.

The upgrade, which also included a new power supply and modified receiver/exciter as well as the AESA antennae (two per shipset), was instigated because of an upcoming frequency spectrum conflict with emerging digital TV satellite signals. However, the hold-ups have had a knock-on effect because the RMP was designed in conjunction with other systems upgrades as part of efforts to provide the bomber with an “open architecture” for later modifications. “It’s basically two years late, and all the upgrades are backed up,” says Wheeler. “Now my biggest drawback is getting enough aircraft because they’re going through the upgrades.”

“We’ve got two inducted now and three are out there flying,” says Wheeler. A sixth, the final SDD phase aircraft, is in programmed depot maintenance at Northrop Grumman’s Palmdale, Calif., facility. Test results to-date are positive in terms of performance and maintenance. “The picture is very clear, and the crews are quite happy with it. There is also a lot less maintenance. It’s a reliable day-to-day working radar without moving parts,” he adds. The AESA modification will also add “hooks” for future modes, including high-resolution synthetic aperture radar and enhanced land/sea moving-target indication.

Production RMPs for the remaining 14 B-2s are coming under a $468-million contract awarded to Northrop Grumman in December 2008. In mid-June the company passed the second of two Air Force program audits. The first, in February, saw completion of a Verification Compliance Review (VCR)-1, which audited testing of the radar’s hardware and basic operational modes. VCR-2 confirmed results for the testing of the radar’s strategic mission modes. Despite the hold-ups, upgrades are expected to be completed by October 2010.

As well as RMP, most other avionics upgrades are aimed at sustainability as well as performance improvements. “Low observable (LO) is no longer the major maintenance driver,” says Mazur, referring to the support headaches associated with keeping the B-2 stealthy. “That’s now No. 3 and avionics has started to raise its head.” Issues are chiefly concerned with supporting the aging technology which, in most cases, dates from the 1970s and 1980s. Special test equipment is becoming obsolete, with maintainers and suppliers sometimes being forced into scouring eBay for equipment as outdated as floppy discs.

Modernization to digital standards is therefore expected to reap both maintenance and performance benefits, adds Mazur. Other avionics updates include several to integrate the B-2 more closely with other air and ground assets. The high-bandwidth, Extremely High-Frequency (EHF) satcom and computers upgrade is “a big pipe, and could make the B-2 the mother node for stealthy platforms in the combat area,” says Mazur. Although running later than originally planned, the first unit is being modified for testing at Edwards AFB, Calif., to “show how it will be integrated,” adds Wheeler. Initial fielding is believed to be set for around mid-2012.

The Link-16 Center Instrument Display/In-Flight Replanner is another upgrade designed to improve theater integration, while a Mode 5/S Identification Friend or Foe (IFF) project likely to be fielded around 2012 will enable better combat identification as well as operations in civilian-controlled airspace.

“One of the biggest items is the defensive management system, which will go to a digital system,” says Mazur. The Lockheed Martin APR-50 DMS is being upgraded with new processors and threat emitters, as well as new software. An associated integrated display systems upgrade will provide processors, fiber optics, Ethernet and the architecture capable of supporting more advanced weapon systems. The upgrade includes flat panel Rockwell Collins multifunction displays, which will replace the original CRT-based Honeywell displays in the field from 2010 onward.

Lockheed Martin Systems Integration is also developing an associated integrated processor unit upgrade designed to replace up to a dozen current stand-alone avionics computers. The new architecture, which includes a Honeywell-developed disk drive unit, also supports a revised single-board processor flight management computer. The processor will also host a new version of the operational flight program (OFP) software translated from the original Jovial programming language into a contemporary language, C.

Longer-term structural viability issues continue to be addressed with a potential third-generation aft deck design to counter persistent cracking caused by high-frequency vibro-acoustic conditions around the recessed engine exhausts. “We’ve got to the preliminary design, and are in the process of going forward with a manufacturing demonstration,” says Harms. The new deck, described by Harms as a complex geometric design, “will have to flex with temperature cycles and will have to be manufactured to certain tolerances.” Fielding is targeted for early 2013, but “based on funding might have to go to 2014,” he adds.

Day-to-day maintenance issues with the LO coating treatment have dropped significantly with the introduction of alternate high-frequency material (AHFM). “It’s much more maintenance-friendly and more durable from an LO perspective,” says Harms. Maintenance downtime to repair and replace skin sections to the correct stealthy signature levels has dropped from between 36-96 hr. to as little as 45 min. “And that’s to do the job perfectly,” says Wheeler.

Faced initially with the staggering statistic of being non-mission capable up to 48,500 hr. per year due to LO maintenance issues, the Air Force has successfully driven beyond its goal of 24,200 hr. to achieve 13,900 hr. in Fiscal Year 2008. LO maintenance man-hours are similarly down by 30% compared with earlier years, says Harms.

Associated LO upgrade programs include an improved signature diagnostic system database, better radar frequency diagnostics, door edge treatments, magnetic radar-absorbing material framing and windshield LO treatments. Some of this is being realized through an integrated windshield redesign which is designed to reduce cracking and improve electrical conductivity.

The B-2 fleet is also around 80% of the way through an upgrade to its General Electric F118-100 engines which, together with the addition of a full authority digital engine control unit (Fadec), are designed to extend engine life as well as reduce incidents involving foreign object damage due to ice buildup in the s-shaped inlet duct. Analysis has showed the problems cropped up during ground runs before flight, when sublimation of atmospheric water vapor caused ice accretion in the inlet. “We made some decisions to do with inlet temperature and dew point, and reduced the amount of time we run the engines on the ground,” Wheeler adds. “As a result, we had zero problems last year.”

The engine improvements include beefing up the first and third stages of the fan module as well as the Fadec, and some elements of the high-pressure system. The upgrade therefore keeps the F118 in line with the more recently refreshed F110 core which shares the same F101 heritage as the B-2 engine. “These changes in combination with the Fadec had made us FOD-free, though the key was some really smart weather guys who figured out the problem,” Wheeler continues.

Weapons upgrades are focused on integrating two new bombs at extreme ends of the spectrum, the winged 250-lb. small diameter bomb II (SDB II) and the bunker-busting 28,900-lb. massive ordnance penetrator (MOP). In late April, the Air Force, Northrop Grumman and Boeing completed a fit check of the MOP at Whiteman using the B-2 weapons load trainer and a MOP mock-up. The B-2 will be capable of carrying two GPS-guided MOPs, and the program includes provision for development of a single smart bomb rack controller per weapon bay, as well as mixed load capability with smart bomb rack assemblies. The first MOP-capable B-2s are expected to be fielded by 2011.

Further off, the SDB II, developed for the B-2 under the “moving target kill” effort, is expected to form part of the bomber’s store mix from around 2013.