BLU-97/B Combined Effects Munition (CEM)
1. Overview
The BLU-97/B Combined Effects Munition (CEM) is a multipurpose air-delivered submunition designed to engage soft targets, light armored vehicles, and materiel through a combination of shaped charge, fragmentation, and incendiary effects. As the payload of the widely-used CBU-87 Combined Effects Munition and CBU-97 Sensor Fuzed Weapon dispenser, the BLU-97/B became one of the most extensively employed cluster munition submunitions in US military operations from the 1990s onward. Its “combined effects” design allows a single submunition to be effective against multiple target types.
2. Country/Bloc of Origin
- Country: United States of America
- Developer: Aerojet (warhead); various contractors for complete system
- Development Period: 1980s
- Service Entry: Late 1980s
- International Users: United States and numerous allied nations
The BLU-97/B was developed to provide air forces with an area-effect weapon capable of engaging diverse target sets with a single munition type, reducing the logistical burden of carrying multiple specialized weapons.
3. Ordnance Class
| Attribute | Classification |
|---|---|
| Type | Submunition / Bomblet |
| Role | Combined Effects (Anti-Personnel, Anti-Materiel, Incendiary) |
| Delivery Method | Air-delivered via dispenser (CBU-87/B, CBU-97/B) |
| Category | Area Effect Munition |
| Target Types | Personnel, light armor, vehicles, materiel, POL sites |
The BLU-97/B is classified as a combined effects submunition, meaning it incorporates multiple kill mechanisms in a single munition to maximize effectiveness against varied targets.
4. Ordnance Family / Nomenclature
Primary Designation:
- BLU-97/B (Bomb Live Unit)
- BLU-97A/B (Improved variant)
- BLU-97B/B (Further improvements)
Parent Systems:
- CBU-87/B CEM (Combined Effects Munition) – Contains 202 BLU-97/B submunitions
- CBU-97/B SFW (Sensor Fuzed Weapon) – Uses BLU-108/B submunitions which deploy Skeet warheads (different system)
- CBU-103/B – Wind Corrected Munitions Dispenser (WCMD) variant with 202 BLU-97/B
Related Munitions:
- BLU-108/B – Smart submunition used in CBU-97 SFW (different design)
- Mk 118 Mod 0 – Earlier Rockeye anti-armor bomblet
- M85 – Similar DPICM submunition (other nations)
NATO Stock Number (NSN): 1325-01-250-4514
Common Names:
- CEM Bomblet
- Combined Effects Bomblet
- “Yellow Bomblet” (due to distinctive color)
5. Hazards
Primary Hazards
| Hazard Type | Description |
|---|---|
| Shaped Charge | Armor-penetrating jet capable of defeating light armor |
| Fragmentation | Steel body fragments at high velocity |
| Incendiary | Zirconium ring creates intense fire; ignites fuels and flammables |
Combined Effects Lethality
The BLU-97/B’s three kill mechanisms work synergistically:
- Shaped charge penetrates armor or creates entry point
- Fragmentation produces anti-personnel and anti-materiel effects
- Incendiary ignites fuel, ammunition, or other flammables
Sensitivity Factors
- Impact Sensitivity: Designed to function on impact; duds may retain sensitivity
- All-Ways Acting Fuze: Functions regardless of impact angle
- Dud Rate: Historical dud rates of 5-20% create significant UXO hazard
- Fuze Variability: Duds may have armed but unfired fuzes, making them extremely dangerous
Safety Considerations
- High Dud Rate: Cluster munitions historically have higher dud rates than unitary weapons
- Bright Color: Yellow coloring makes bomblets attractive to children
- Small Size: Can be picked up and handled, leading to casualties
- Environmental Factors: Soft ground, vegetation, snow can cushion impact and prevent functioning
- Delayed Hazard: Duds may function if subsequently disturbed
Kill/Danger Radius
| Zone | Distance | Effect |
|---|---|---|
| Lethal Radius | ~10 meters (individual bomblet) | High probability of fatal injuries |
| Fragmentation Hazard | ~50 meters | Significant injury risk |
| Incendiary Effect | Immediate vicinity | Fire ignition of flammables |
| Pattern Coverage | ~200m x 400m (typical) | Full CBU-87 dispersion area |
⚠️ WARNING: BLU-97/B submunitions have historically high dud rates. The bright yellow coloring makes them visible but also attractive, especially to children. Unexploded bomblets are extremely dangerous and may detonate if touched, moved, or disturbed. Never approach any suspected BLU-97/B munition.
6. Key Identification Features
Physical Characteristics
| Dimension | Measurement |
|---|---|
| Length | Approximately 20 cm (7.9 inches) |
| Diameter | Approximately 6.1 cm (2.4 inches) |
| Weight | Approximately 1.5 kg (3.3 lbs) |
Visual Identification
- Shape: Cylindrical body with conical nose and distinctive tail fin assembly
- Color: Bright yellow body (highly distinctive)
- Markings: Black stenciled text with nomenclature and lot data
- Material: Steel body (for fragmentation)
- Distinctive Features:
- Bright yellow color is unmistakable
- Conical nose with shaped charge liner visible
- Pop-out scissor-type tail fins (deployed state)
- Fabric/nylon drag ribbon may be attached
Tail Assembly
The BLU-97/B features a distinctive scissor-type pop-out tail fin assembly:
- Fins deploy after release from dispenser
- Creates drag and orients bomblet nose-down
- Fins may be found extended or partially deployed in dud specimens
- Fabric ribbon may also be present as additional drag device
Color Significance
The bright yellow color serves multiple purposes:
- Identification: Easily identifiable as live ordnance
- Warning: High-visibility color indicates danger
- Unfortunately: Also attractive to civilians, especially children
Condition Indicators
- Intact: Yellow body visible, tail fins may be deployed or stowed
- Partially Functioned: Damaged body, possible deformation
- Dud: Appears intact but impacted ground without detonating; extremely dangerous
- Post-Detonation: Fragmented remains, scorch marks, small crater
7. Fuzing Mechanisms
Primary Fuze System
The BLU-97/B employs an all-ways acting (AWA) impact fuze:
| Component | Function |
|---|---|
| Firing Pin | Strikes detonator on impact |
| All-Ways Acting Mechanism | Ensures function regardless of impact angle |
| Safe/Arm Device | Prevents premature detonation before release |
| Spin Arming | Rotation during fall arms the fuze |
Arming Sequence
- Release: Submunition ejected from dispenser
- Tail Deployment: Scissor fins pop out, creating drag
- Spin-Up: Aerodynamic forces cause rotation
- Arming: Centrifugal force moves arming mechanism
- Descent: Bomblet orients nose-down via drag
- Impact: All-ways acting fuze initiates detonation
Safety Mechanisms
- Setback Safety: Requires ejection acceleration to initiate arming sequence
- Spin Arming: Minimum rotation required before fuze arms
- S&A Device: Mechanical safety prevents firing pin travel until armed
All-Ways Acting Fuze Principle
The AWA fuze ensures detonation regardless of how the bomblet strikes the target:
- Functions at any impact angle
- Mechanical design allows firing pin to strike detonator from multiple orientations
- Critical for area-effect weapons where precise orientation cannot be guaranteed
Dud Fuze Conditions
Unexploded BLU-97/B bomblets may have fuzes in various states:
- Unarmed Dud: Failed to complete arming sequence (rare; still dangerous)
- Armed Dud: Fully armed but failed to detonate on impact (most common; extremely dangerous)
- Delayed Function: May detonate with any subsequent disturbance
8. History of Development and Use
Development Background
The BLU-97/B was developed during the 1980s as part of the Combined Effects Munition program. The US Air Force sought a single submunition that could effectively engage multiple target types—eliminating the need to carry separate anti-personnel, anti-armor, and incendiary weapons for different mission requirements.
Development Timeline
| Year | Event |
|---|---|
| 1980s | Development of combined effects concept |
| 1986 | CBU-87 enters service |
| 1991 | Extensive combat use in Operation Desert Storm |
| 1999 | Used in NATO Kosovo operations |
| 2001-2003 | Employed in Afghanistan and Iraq |
| 2008 | Convention on Cluster Munitions adopted (US did not sign) |
Combat Employment
Operation Desert Storm (1991): The CBU-87 with BLU-97/B submunitions was extensively used against Iraqi forces, including:
- Armored formations
- Artillery positions
- Troop concentrations
- Supply depots and POL sites
- Airfield facilities
Thousands of CBU-87 dispensers were employed, distributing hundreds of thousands of BLU-97/B bomblets.
Kosovo (1999): NATO air forces employed CBU-87 against Serbian forces and infrastructure. Post-conflict UXO clearance revealed significant numbers of unexploded BLU-97/B bomblets.
Afghanistan (2001-2002): Used against Taliban and Al-Qaeda positions. The yellow color of BLU-97/B bomblets unfortunately resembled humanitarian food packages also being dropped, causing tragic confusion.
Iraq (2003): Employed during Operation Iraqi Freedom against various military targets.
Dud Rate Controversy
The BLU-97/B became central to cluster munition controversy due to dud rates:
- Manufacturer Claims: Less than 5% dud rate
- Field Experience: Often 10-20% or higher depending on conditions
- Contributing Factors:
- Soft ground cushioning impact
- Snow or vegetation
- Low-altitude releases
- Fuze manufacturing defects
- Age of munitions
Current Status
- The CBU-87/BLU-97/B system remains in US inventory
- Subject to US policy restrictions on cluster munition use
- Not banned for US forces (US did not sign 2008 Convention on Cluster Munitions)
- Extensive UXO contamination exists in former conflict zones
9. Technical Specifications
Explosive Content
| Specification | Detail |
|---|---|
| Main Charge | Cyclotol (RDX/TNT mixture) |
| Charge Weight | Approximately 287 grams (0.63 lbs) |
| Shaped Charge Liner | Copper |
| Incendiary Ring | Zirconium |
Warhead Effects
| Effect Type | Capability |
|---|---|
| Shaped Charge Penetration | ~175mm (7 inches) RHA equivalent |
| Fragmentation | Hundreds of high-velocity steel fragments |
| Incendiary | Zirconium burns at ~3,000°C; ignites fuels |
Performance Characteristics
| Specification | Detail |
|---|---|
| Armor Penetration | 175mm Rolled Homogeneous Armor |
| Effective Against | APCs, IFVs, trucks, aircraft on ground, POL, soft targets |
| Function Mode | Impact (all-ways acting) |
| Operating Temperature | -40°C to +70°C (-40°F to +158°F) |
Dispenser Configuration
| System | Submunition Count | Coverage Area |
|---|---|---|
| CBU-87/B | 202 BLU-97/B | ~200m x 400m |
| CBU-103/B WCMD | 202 BLU-97/B | Similar (wind-corrected) |
Dispersion Pattern
- Typical Pattern: Elliptical footprint
- Size Variables: Release altitude, aircraft speed, wind conditions
- Density: Bomblets distributed across pattern at varying intervals
- Overlap: Adjacent patterns may be used for larger area coverage
10. Frequently Asked Questions
Q: Why is the BLU-97/B yellow, and does this create problems? A: The bright yellow color is standard US practice for marking high-explosive ordnance, intended to make the munitions easily identifiable as dangerous. However, this has created serious problems in humanitarian contexts. In Afghanistan (2001-2002), yellow BLU-97/B bomblets were dropped in the same areas where yellow humanitarian daily ration (HDR) packages were also being airdropped. Despite different shapes, the similar color caused tragic confusion, particularly among children. This led to changes in humanitarian packaging colors. The yellow color also makes unexploded bomblets attractive to children who may mistake them for toys.
Q: How does the BLU-97/B achieve its three combined effects? A: The BLU-97/B integrates three kill mechanisms in its design. The copper-lined shaped charge in the nose penetrates armor and hard targets upon impact. The steel body fragments at high velocity, creating anti-personnel and anti-materiel effects similar to a grenade. The zirconium incendiary ring surrounding the explosive charge burns at approximately 3,000°C upon detonation, capable of igniting fuel, ammunition, and other flammable materials. This combination makes a single submunition effective against personnel, light armored vehicles, parked aircraft, supply dumps, and fuel storage—targets that would otherwise require different specialized weapons.
Q: Why do BLU-97/B bomblets have such high dud rates compared to other munitions? A: Several factors contribute to BLU-97/B dud rates exceeding design specifications: the all-ways acting fuze is mechanically complex and susceptible to manufacturing variations; soft impact surfaces (mud, sand, snow, vegetation) may cushion the bomblet sufficiently to prevent fuze function; low-altitude releases may not allow sufficient spin-up time for proper arming; stockpiled munitions may experience component degradation over time; and the sheer numbers deployed (hundreds per dispenser) statistically guarantee significant dud quantities even at low percentage rates. A single CBU-87 with 202 bomblets at even a 5% dud rate leaves 10 unexploded submunitions; at 15%, that number rises to 30.
Q: What targets is the BLU-97/B most effective against? A: The BLU-97/B is most effective against “soft” and lightly armored targets where its combined effects can be fully exploited: personnel in the open or in light cover; light armored vehicles (APCs, IFVs, trucks); parked aircraft and helicopters; radar installations and air defense equipment; POL (petroleum, oil, lubricants) storage and supply points; ammunition storage areas; and support infrastructure. The 175mm armor penetration is insufficient against main battle tank frontal armor but effective against top and side armor of lighter vehicles. The incendiary effect makes it particularly devastating against fuel and ammunition.
Q: How should unexploded BLU-97/B bomblets be approached during clearance operations? A: Unexploded BLU-97/B bomblets should NEVER be approached by anyone other than qualified EOD personnel. The all-ways acting fuze in an armed dud may function if the bomblet is touched, moved, or even subjected to nearby vibration. Standard clearance protocols require: marking the location and establishing a wide cordon; documenting the position with GPS and photography from a safe distance; reporting to EOD authorities; and awaiting disposal by qualified personnel using remote or standoff techniques. In heavily contaminated areas, systematic survey and clearance operations using appropriate protective measures are required.
Q: How does the CBU-87 dispenser release and distribute the BLU-97/B bomblets? A: The CBU-87 is a tactical munitions dispenser (TMD) that opens at a preset altitude, ejecting its 202 BLU-97/B submunitions. The dispenser’s clamshell halves separate, releasing the bomblets which then deploy their scissor tail fins for stabilization. The bomblets spread in an expanding pattern as they fall, creating an elliptical footprint on the ground. Pattern size depends on release altitude (higher releases create larger patterns), aircraft speed, and wind conditions. The pilot or weapons officer sets fuzing options to achieve the desired pattern density for the target type.
Q: What is the difference between the CBU-87 and CBU-97, since both designations sound similar? A: Despite similar nomenclature, these are distinctly different weapons. The CBU-87/B CEM (Combined Effects Munition) contains 202 “dumb” BLU-97/B bomblets that fall ballistically and detonate on impact. The CBU-97/B SFW (Sensor Fuzed Weapon) contains 10 BLU-108/B submunitions, each of which releases four “Skeet” smart warheads that use infrared sensors to detect and target armored vehicles. The CBU-97 is a precision weapon specifically designed for anti-armor operations, while the CBU-87 is an area-effect weapon for multiple target types. The CBU-103 WCMD is an improved CBU-87 with GPS/INS guidance for better accuracy.
Q: Why hasn’t the United States banned the BLU-97/B under the Convention on Cluster Munitions? A: The United States did not sign the 2008 Convention on Cluster Munitions (CCM) and is not bound by its provisions. US officials have cited several reasons: military utility of cluster munitions against dispersed targets; lack of adequate alternative weapons for certain mission sets; and the assertion that newer submunitions with lower dud rates and self-destruct features adequately address humanitarian concerns. The US has implemented national policy restrictions on cluster munition use, including dud rate requirements, but retains the BLU-97/B and other cluster munitions in inventory. This remains controversial, with humanitarian organizations continuing to advocate for US signature of the CCM.
This document is for educational and training purposes only. All ordnance should be treated as dangerous until rendered safe by qualified EOD personnel. Never attempt to handle, move, or disturb any suspected explosive ordnance.