Programmable Bomb Fuze Meets the Challenges of the Modern Battlefield

Today’s aircraft operate amid varied, fast-evolving mission requirements — whether they’re Air Force F-15s engaging enemy fighters in air-to-air combat, F/A-18s taking off from carriers to attack inland enemy targets, or large B-52 bombers entering dangerous airspace for precision bombing campaigns.

The ability for these aircraft to carry a larger, lighter, all-electronic and reliable programmable bomb fuze would enable pilots to adjust attack mission requirements in flight and improve the tactical equation.

This kind of thinking informs the conceptual inspiration for Northrop Grumman’s new FMU-139D/B bomb fuze, a high-tech weapons technology in full-rate production now being presented to potential customers.

“This is a general-purpose bomb fuze that has a true hard target capability,” said Harmon Stockwell, senior manager for business development at Northrop Grumman. “It replaces three legacy fuzes: the FMU-139C/B, the FMU-152 and the FMU-143.”

Finding Hard Targets

As opposed to more easily reachable soft target sets that are more readily available and exposed, heavily defended “hard & buried” targets can be challenging to destroy — sometimes even with advanced GPS or laser-guided bombs. Hard targets require not only accurate intelligence and precision-guidance technology, but also a highly effective fuzing system that will survive target impact/penetration while optimizing warhead blast effects and the ultimate destruction of the target.

The technical and operational concept forming the new fuze system increases operational capability and mission flexibility while lowering the total cost of ownership for customers. But perhaps most importantly, to meet the changing dynamics of the battlespace the fuze’s increased capabilities are optimized by a cockpit programmable feature. This feature provides the aircrew with a pre-weapon release ability to flex missions or target sets in seconds by changing weapon/fuze settings enroute to the engagement area. 

“It’s all electronic – no moving parts to fail improving functionality and survivability” Stockwell pointed out. “Prior to this fuze, the U.S. general-purpose fuzes were “Electro-Mechanical” applications – a combination of electronics and explosive-train moving parts. Before that, they were all mechanical fuzes.”

Stockwell explained that weapon systems like Joint Direct Attack Munitions (JDAMs) and Paveway precision systems include a guidance system, warhead and fuze. These components must integrate successfully to ensure operational functionality. With the “all-electronic” FMU-139D/B, Navy and Air Force pilots can operate a tailorable cockpit-programmable fuze delivering greater effects across the battle space.

Stockwell explained. “The FMU-139D/B improves the reliability, survivability and safety of the fuze, allowing pilots to program delays and arm times from the cockpit. It gives a true hard target capability where previous fuzes had limited hard target capability.”

Bigger Impact, Smaller Footprint

Yet another advantage with the FMU-139D/B is that it enables JDAMs and Paveway bombs to operate across the target spectrum with a single fuze. This streamlines operational effectiveness, improves efficiency and reduces costs. One of the key aims in designing the new technology was to reduce the number of fuzes required for mission success and reduce the logistical footprint needed for operations.

For the U.S., replacing three fuzes with one fuze is a major logistical savings right up front, “Stockwell noted.” The advantages of a single fuze inventory are huge: reduces multi-fuze training requirements/systems for air and ground crew to one system, reduces global storage space required for a multi-fuze inventory – and the new fuze is compatible with current tool and test sets used with legacy fuze systems reducing overall total upfront ownership cost.

Ultimately, alongside the logistical and cost-saving advantages provided by the FMU-139D/B, the optimal purpose for the technology is to support warfighters by providing increased attack flexibility, precision guidance and the operational lethality needed to successfully destroy enemy targets the “first time, every time.”

“You never want to return to the same target because either you missed it or the weapon system didn’t function – because the intensity with which that target will be defended the second time will go up exponentially,” Stockwell explained.”

Fitting the Tool to the Task

The new fuze will service a wide variety of BLU-100 and MK-80 series warheads — and that means warfighters can choose the right tool for the task-at-hand. Larger 2,000-pound bombs such as the BLU-109 — or even 500-pound BLU-111s are all optimized with the FMU-139D/B. The Mark-80 series, which includes the Mk 81, Mk 82, Mk 83 and Mk 84, range from 250-pounds up to 2,000 pounds as well. “The nuances of the target engagement that you are looking for will determine whether or not it will be a BLU warhead or a Mk warhead,” Stockwell said.

“Until now, bomb fuzing was most often the weak-link in total weapon system performance,” remarked Stockwell. “Early in the Vietnam War, bomb delivery was characterized by a “dumb bomb” with two mechanical fuzes (for reliability). Later in the conflict, the introduction of the Paveway Laser Guidance Bomb kits improved guidance, but actually reduced fuzing reliability by occupying the forward fuze-well replacing the second mechanical fuze. As precision guidance and warheads continued to improve, fuzing did not see its first major improvement until 1986 with the introduction of the FMU-139A/B later followed by FMU-139B/B and C/B. However, it was not until the development of JDAM and Enhanced Paveway (GPS & Laser) in the mid ‘90s that led to a significant effort in fuzing development. This development gave way to the FMU-152 Joint Programmable Fuze (JPF) introduced in 2004. Intended for service with both the U.S. Air Force and U.S. Naval forces, the FMU-152 displayed limited hard-target capability and was never adopted by the U.S. Navy. The introduction of the FMU-139D/B set a new standard in general purpose and hard-target bomb fuzing. The FMU-139D/B has exceeded all customer expectations and fully embraced by both US Naval Forces and the US Air Force – providing future technology today and providing fuzing service well into the future.

Northrop Grumman is now in full-rate production with the FMU-139D/B for U.S Forces and its Allies. The programmable fuze holds tremendous potential for giving warfighters more and better options during combat, so they can more effectively keep our nation safe.

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Kailen Brant
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