BLU-28 Practice Submunition
1. Overview
The BLU-28 is a United States practice (training) version of the BLU-3/B anti-personnel fragmentation submunition. Designated as a training analog, the BLU-28 replicates the external form, dimensions, and deployment characteristics of the live BLU-3/B “Pineapple” bomblet without containing a lethal explosive fill or fragmenting body. It was developed to allow aircrew and ground forces to train on delivery, dispersal patterns, and recognition of BLU-3/B type submunitions under realistic conditions.
Safety Note: All ordnance—including items designated as “practice”—should be treated as potentially dangerous until positively confirmed safe by qualified EOD personnel. Practice munitions may still contain pyrotechnic spotting charges, live fuze components, or other hazardous elements.
2. Country/Bloc of Origin
- Country: United States of America
- Era: Cold War period (1960s), concurrent with the development and fielding of the live BLU-3/B
- Producer: Manufactured by various U.S. defense contractors as part of the BLU-3/B production program
3. Ordnance Class
- Type: Practice submunition (training bomblet)
- Role: Training analog for the BLU-3/B anti-personnel fragmentation submunition
- Delivery Method: Air-dropped via the same dispenser systems as the live BLU-3/B, including the SUU-7 and SUU-14 series dispensers (CBU-2 and CBU-14 cluster bomb units)
4. Ordnance Family / Nomenclature
- Official Designation: BLU-28
- ASETDS Family: BLU (Bomb Live Unit) series, practice variant
- Related Live Variant: BLU-3/B (live anti-personnel fragmentation submunition)
- Common Names: BLU-28 practice bomb, BLU-3/B practice variant
- Parent Systems: Used with practice versions of CBU-2 and CBU-14 cluster bomb units
5. Hazards
- Primary Hazard: Although designated as a practice round, the BLU-28 may contain a pyrotechnic spotting charge to mark impact points during training exercises
- Fuze Components: May retain a live or partially functional fuze mechanism identical in design to the BLU-3/B, which includes a spring-loaded striker and detonator assembly
- Impact Hazard: The steel drag vanes and body present a physical hazard at terminal velocity; the item is designed to impact the ground at speed
- UXO Considerations: Practice rounds found in training ranges should not be assumed inert. Degradation, modification, or mixed loading could mean live components are present. BLU-28s may be found alongside live BLU-3/B submunitions in legacy training areas
- Misidentification Risk: Externally nearly identical to the live BLU-3/B; positive identification requires careful inspection of markings and body construction
6. Key Identification Features
- Size: Approximately 4 inches (101.6 mm) in height; 2.7 inches (68.6 mm) in diameter; approximately 6.8 inches (172.7 mm) with drag vanes deployed
- Weight: Approximately 1.7 lbs (0.77 kg), lighter than the live BLU-3/B due to the absence of steel fragmentation balls in the body
- Shape: Cylindrical body with a rounded top and six spring-loaded drag vanes that deploy upon release; nearly identical silhouette to BLU-3/B
- Color and Markings: Typically painted blue (indicating practice/inert ordnance per U.S. military color-coding conventions), in contrast to the yellow body of the live BLU-3/B. Markings are typically white or black, indicating practice designation
- Body Construction: The practice variant lacks the embedded steel balls that give the live BLU-3/B its characteristic “pebbled” surface texture. The body may appear smoother
- Drag Vanes: Six spring-loaded steel vanes identical to the live variant
- Distinguishing Feature: Absence of the pebbled/dimpled surface texture caused by embedded steel fragmentation balls is the most reliable visual differentiator from the live BLU-3/B
7. Fuzing Mechanisms
- Fuze Type: The BLU-28 may use a practice fuze or a modified version of the BLU-3/B’s impact fuze mechanism
- Arming Sequence: Identical to the BLU-3/B—upon ejection from the dispenser, the airstream strips the spring tab and safety strap, allowing the drag vanes to deploy. Vane deployment releases the cup assembly, withdrawing the firing pin from the arming slide cavity. An escapement mechanism provides a short delay before alignment of the detonator and firing pin
- Trigger Method: Impact-initiated; the cup drives the firing pin into the detonator upon ground contact
- Spotting Charge: If equipped, a pyrotechnic spotting charge produces a visible smoke signature to mark the impact point for training evaluation
- Self-Destruct/Neutralization: No self-destruct or self-neutralization features
8. History of Development and Use
- Development: The BLU-28 was developed in the early-to-mid 1960s alongside the live BLU-3/B to support training for cluster bomb delivery during the Vietnam War era. The U.S. military required a safe means to practice dispersal patterns and delivery tactics with the CBU-2 and CBU-14 weapon systems
- Use: Employed extensively on U.S. military training ranges during the Vietnam War period and into the Cold War era for aircrew qualification and delivery training
- Notable Service: Used primarily at U.S. Air Force and Navy training ranges to develop and refine cluster bomb delivery tactics, including low-altitude delivery profiles
- Current Status: Obsolete. No longer in active production or standard military training inventories. Legacy items may still be encountered on former training ranges
- UXO Relevance: BLU-28 remnants may be found on U.S. and allied training ranges alongside other Vietnam-era ordnance. Range clearance operations must account for potential mixed loading with live BLU-3/B submunitions
9. Technical Specifications
| Parameter | Specification |
|---|---|
| Designation | BLU-28 |
| Type | Practice submunition |
| Live Analog | BLU-3/B |
| Height (body) | ~4 in (101.6 mm) |
| Diameter | ~2.7 in (68.6 mm) |
| Height (vanes deployed) | ~6.8 in (172.7 mm) |
| Weight | ~1.7 lbs (0.77 kg) |
| Body Material | Aluminum or zinc alloy (no embedded steel balls) |
| Explosive Fill | Pyrotechnic spotting charge (if equipped); no main HE fill |
| Fuze | Practice impact fuze (modified BLU-3/B fuze) |
| Color | Blue (practice ordnance marking) |
| Dispenser Systems | SUU-7 series, SUU-14 series |
10. Frequently Asked Questions
Q: How do I visually distinguish a BLU-28 practice round from a live BLU-3/B? A: The two most reliable indicators are color and surface texture. The BLU-28 is typically painted blue per U.S. practice ordnance conventions, while the live BLU-3/B is painted yellow. Additionally, the BLU-3/B has a distinctive pebbled surface from embedded steel fragmentation balls, which the BLU-28 lacks. However, paint may be weathered or absent in field conditions, so surface texture becomes the more durable identification feature.
Q: Is a BLU-28 safe to handle? A: No ordnance item should be assumed safe without proper EOD assessment. BLU-28 practice rounds may contain live pyrotechnic spotting charges and functional fuze components. Additionally, practice and live rounds may have been mixed in training loadouts. Always treat discovered submunitions as live until confirmed otherwise by qualified personnel.
Q: Why was the BLU-28 needed when the BLU-3/B existed? A: Training with live cluster munitions on practice ranges posed unacceptable safety risks and environmental contamination concerns. The BLU-28 provided a safe, realistic training experience that allowed pilots to practice delivery profiles, evaluate dispersal patterns, and develop tactics without the hazards of live fragmentation submunitions.
Q: What parent munitions deliver the BLU-28? A: The BLU-28 was loaded into the same dispenser systems used for the live BLU-3/B, primarily the SUU-7 series (used in CBU-2 variants) and the SUU-14 series (used in CBU-14 variants). This ensured training realism, as the dispersal characteristics closely matched live employment.
Q: Where might BLU-28 submunitions be found today? A: BLU-28s may be encountered on former U.S. military training ranges, both domestic and overseas, particularly ranges used during the 1960s and 1970s for tactical air-to-ground training. They may also be found in Vietnam-era legacy storage facilities.
Q: Could a BLU-28 be confused with other submunitions? A: Yes. Without markings, the BLU-28 closely resembles the BLU-3/B in overall shape and size. It also shares the same drag vane configuration as other BLU-series submunitions. Positive identification requires examination of body color, surface texture, and stenciled markings. In degraded conditions, expert EOD assessment is essential.
Q: How does the BLU-28 relate to modern practice submunitions? A: The BLU-28 represents an early generation of practice cluster submunitions. Modern practice submunitions incorporate more sophisticated spotting charges, improved safety features, and clearer marking systems. The basic concept—replicating the form and deployment of a live round while eliminating the lethal payload—remains the same.