🔷 Fuzion

The 20-year Fuze Saga

Last week, Northrop Grumman finalized a $198m Navy contract as part of the full rate production of 56,000 FMU-139D/B bomb fuzes. This program is intended to replace 3 other fuzes: the FMU-139C/B, FMU-143, and FMU-152.

The origin story of how it came to be is a good one.

What

These fuzes are tall-boy-sized devices with an arming unit and delay feature connected to small booster material (aka tiny explosive). They screw into bomb bodies and are what make them go boom. No fuze = no boom.

The 3 fuzes being replaced by this program were each designed with a purpose:

• FMU-139: developed by the Navy in the early 1980s as a replacement for Vietnam-era mechanical fuzes, this electro-mechanical fuze has faceplate settings that are selectable during installation or pre-flight.

• FMU-143: developed by the Air Force in the late 1980s for hard target penetration, this fuze has a reinforced case with a simple mechanical non-selectable delay optimized to survive penetration before detonation. It has several variants to support 30, 60, or 120-millisecond delay options, as well as different versions for the Air Force and Navy.

• FMU-152: developed jointly by the Air Force and Navy (but Air Force-led) in the mid-1990s to combine all the features of the FMU-139 and FMU-143 into a single fuze—and replace them. It also added cockpit-selectable capabilities leveraging the JDAM smart bomb interface that was being developed in parallel. The FMU-152 is commonly known as the Joint Programmable Fuze (JPF).

Nerd Alert: the US military has weird ways of naming things, and fuze suffixes are one of them. They start with FMU-XXX (FMU = Fuze Munition Unit), then add “/B” for the version/production, so it looks like this: FMU-139/B. When a new version comes out, they insert a new letter in between (FMU-139A/B), and subsequent versions advance that letter. Hence, the FMU-139C/B is being replaced by the FMU-139D/B. And yes, to confuse you, this means that even though D is the fourth letter of the alphabet, it stands for the 5th version.

So What

Getting back on track: If you read the above carefully, you probably noticed that the newest of those programs—the FMU-152 JPF—didn’t replace any of the other fuzes as promised.

One of the issues was a tendency to dud at penetration delay settings, even at the lower end of the FMU-143’s capabilities—and the higher the delay the higher the dud rate. The Air Force had to keep using the FMU-143.

The other issue the JPF had was long-delay options—like really long. This capability enabled one to drop a bomb and let it sit for 15 minutes to 24 hours (in selectable increments) before it detonated. Our memory is a bit hazy, but the internal design to enable this became a significant issue when the Navy-sponsored 2004 insensitive munitions (IM) certification policy came into effect—effectively restricting/barring the FMU-152’s use on aircraft carriers even though it used a navy-conforming booster (PBXN-7). The Navy had to keep using the FMU-139C/B.

WTF

Due to this nuance, of the tens of thousands of JDAM smart bombs employed by US airpower in the Middle East over the past 20 years, a JDAM employed by the Air Force predominantly used FMU-152 fuzes while JDAMs dropped by the Navy used FMU-139 fuzes.

And due to that nuance, the Air Force had convenient cockpit-selectable fuzes the whole time whereas the Navy did not.

💣 Clarification: The Navy Hornet/Super Hornet community uses the Mk 122 safety switch with the FMU-139, giving it a poor man’s form of cockpit selectability.

What Now

The new FMU-139D/B is an Electronic Safe and Armed Fuze (ESAF), a design used in other weapons where the fuze is built into the weapon during production.

Still, it won’t meet all the hard target needs. That job is for the FMU-167/B Hard Target Void Sensing Fuze (HTVSF), also produced by Northrop Grumman.

Finally, you might be wondering why the new FMU-139D/B did not just continue using the FMU-152 designation lineage. Our hunch is that it’s because 1) the Navy leads the new fuze program, 2) they own the FMU-139 program lineage, and 3) they have scar tissue from the Air Force-led FMU-152 program.

In That Number

60+

China has 60+ fixed-wing airborne early warning and control (AEW&C) platforms. The link is a great one-stop shop deep-dive into the fleet. 

TRIVIA

On this day in 1951, the Treaty of Peace was signed by Japan and 48 UN members, officially ending hostilities between Japan and the Allied powers after World War II. The Soviet Union refused to sign. Why?

A) The treaty allowed US military bases in Japan
B) They were supporting North Korea in the Korean War
C) They were still in conflict with Japanese forces post-WWII

On the Radar

Northrop Grumman and L3Harris are competing to win the EW portion of Poland’s program to upgrade 48 Block 50 F-16s to the Block 70 standard. NG is pitching the ALQ-257 IVEWS, whereas L3H is offering the ALQ-254 Viper Shield for the project. L3H’s Viper Shield is part of the FMS program of Block 70/72 F-16s for allied countries. But NG’s IVEWS is the system being integrated into US Air Force Block 50 F-16s and just entered flight testing. Poland’s upgrade program puts them in a unique position to choose either.

• The Merge’s Take: Note that the newer ALQ-257 designation is going on older US F-16s, while the older ALQ-254 is destined for new Block 70/72s. That, plus knowing the rigors of flight testing between domestic and FMS programs…we’d go with whatever the US Air Force is fielding. Bonus: it should inherit US-driven follow-on upgrades and programming support.

They Said It
“I wouldn’t rule anything out. But I also wouldn’t rule anything back in. What we’ve got to make sure is, as we sum it up into a package that delivers air superiority, that it actually meets the mission need as best we are able to do it and is affordable at the same time.”

— Andrew Hunter, Air Force chief weapons buyer, on how the 6th-gen NGAD fighter requirements review could cascade into tweaking requirements for its unmanned loyal wingmen—the CCA program

NGAD is on pause as the service starts at the beginning by reviewing its requirements. The other dynamic is Congressional support to fund the production of a fleet that is reportedly projected to cost $300m per plane. Yep, definitely want to get the ducks in a row.

Meanwhile, CCA has been getting more vocal support from Congress due to its affordable mass narrative

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Knowledge Bombs

• TAI’s long-range bomber drone flew with ordnance for the first time (VIDEO)

• Kvertus (Ukrainian company) revealed Aero Azimuth, a balloon-based ESM sensor that detects and locates drone operators

• Top Aces now has an IRST pod integrated into their aggressor F-16s

• The Air Force awarded 2 firms contracts to design a refueling pod for the F-15

• WB Group (a Polish company) unveiled a new line of long-range kamikaze drones

• India’s first unmanned bomber completed its maiden flight

• Palantir is joining the S&P 500

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ANSWER
A. The Soviets opposed US military bases in Japan, knowing it would complicate regional relations as Cold War tensions grew.