Blast Fence (Jet Blast Deflector)

Definition and Overview

A blast fence, also known as a jet blast deflector or jet blast barrier, is a purpose-built safety structure installed at airports and airfields to protect people, vehicles, and infrastructure from the powerful exhaust produced by aircraft jet engines. Jet blast is a high-velocity, high-temperature stream capable of causing severe injury, property damage, and the dangerous propulsion of debris (Foreign Object Debris/FOD). Blast fences are strategically installed behind aircraft parking positions, at runway thresholds, along taxiways, and near engine test enclosures to redirect and diffuse this hazardous airflow away from vulnerable areas such as service roads, passenger walkways, buildings, and critical equipment.

Unlike blast walls or revetments—which are intended to absorb explosive force or provide anti-ram protection—blast fences are specifically engineered to manage the continuous, directional force of jet exhaust. Their design focuses on redirecting airflow upward or to the side, rather than containing shock waves from explosions. International aviation authorities, including the International Civil Aviation Organization (ICAO) and the Federal Aviation Administration (FAA), recognize blast fences as essential components of airport safety management, especially in areas where aircraft operate at high engine power near people, vehicles, or infrastructure.

Modern blast fences have evolved alongside the development of more powerful jet engines and the increasing complexity of airport environments. Early designs relied on simple metal screens, but advances in materials science, aerodynamic modeling, and noise abatement have led to blast fences that are transparent, acoustically treated, modular, or portable. Materials such as galvanized steel, stainless steel, aluminum, fiberglass, acrylic, and composites are chosen for their suitability to specific environments and operational needs. Computational Fluid Dynamics (CFD) is now commonly used in the design process to optimize the fence’s angle, height, and shape for maximum safety and efficiency.

Blast fences are not limited to civilian airports; they are also used at military airfields, engine test pads, and rocket launch sites—anywhere protection from high-velocity exhaust is needed. Across all settings, their primary mission is to ensure operational safety by controlling and redirecting hazardous jet exhaust, safeguarding people, infrastructure, and the public.

Purpose and Function

Blast fences address multiple hazards associated with jet blast:

• Physical Injury: Jet blast can knock down or seriously injure personnel.
• Property Damage: The force can damage vehicles, buildings, and equipment.
• Debris Propulsion: Loose objects or FOD can be hurled at dangerous speeds.
• Erosion: Repeated jet blast erodes pavement and landscaping.
• Noise Pollution: High engine thrust produces excessive noise, disturbing workers and nearby residents.

The principal function of a blast fence is to redirect and diffuse jet blast. The fence is installed at a calculated distance and angle to deflect high-speed airflow, usually vertically (70–90° from horizontal), so that wind speed and turbulence are reduced at ground level. This protects people, vehicles, and equipment behind the fence.

Blast fences also contain debris by intercepting and redirecting objects carried by jet blast, preventing them from entering operational zones or public areas. In some designs, especially those integrated into Ground Run-Up Enclosures (GREs), blast fences also reduce noise, providing up to 20 dB(A) of attenuation.

By controlling airflow and turbulence, blast fences prevent inadvertent movement of aircraft, vehicles, or equipment caused by jet blast, reducing the risk of accidents. They also allow for the efficient use of apron and taxiway space, enabling protected zones to be located closer to active operations without compromising safety.

Design Principles

Designing a blast fence involves aerodynamics, structural engineering, materials science, and operational know-how:

• Deflection Angle: Most blast fences deflect exhaust upwards at a steep angle (typically 70–90° from horizontal), minimizing ground-level wind speeds and turbulence. CFD simulations are used to determine the optimal angle for each site.
• Aerodynamic Performance: Curved or contoured surfaces facilitate smooth airflow and minimize turbulence. Mesh or transparent barriers are used where visibility is critical.
• Structural Integrity: Materials are chosen for durability and resistance to corrosion, fatigue, and impact. Hot-dip galvanized steel is common, but fiberglass or composites are used where radar/ILS compatibility is needed.
• Footprint Optimization: Modular and prefabricated systems allow installation in tight or irregularly shaped areas, while portable solutions can be deployed as needed.
• Visual Transparency: Mesh or transparent acrylic panels are chosen in locations where clear sightlines are essential.
• Modern Innovations: Frangible materials (which break away if struck), integrated lighting, and sustainable manufacturing practices are increasingly used.

Types of Blast Fences

Opaque (Solid) Deflectors:
Traditional style, using solid corrugated or flat steel, stainless steel, or composite panels. These redirect blast vertically and are used where the highest levels of protection are needed, such as runway ends and behind widebody aircraft.

Mesh and Transparent Barriers:
Use metallic grids or clear acrylic/polycarbonate panels. These offer partial or full visibility and are used where operational oversight is critical, such as near terminal access roads or ramp controls.

Fiberglass and Composite Deflectors:
Non-conductive, frangible, and radar/ILS-neutral, these are ideal near sensitive navigation aids or in corrosive environments. Lightweight and easy to assemble, they reduce risk if struck by an aircraft.

Portable and Modular Solutions:
Rapidly deployable for temporary needs, such as construction zones or changing apron layouts. Modular systems can be scaled as needed.

Ground Run-Up Enclosures (GREs) with Integrated Blast Protection:
Specialized structures that combine blast deflection with advanced acoustic attenuation, enabling safe engine testing near operational areas.

Key Features and Technical Specifications

Material Options

• Galvanized Steel: High strength, corrosion-resistant, suitable for most climates; modular and easy to repair.
• Stainless Steel: Superior corrosion resistance for coastal/industrial sites; non-magnetic.
• Aluminum: Lightweight, corrosion-resistant, ideal for portable/modular systems.
• Fiberglass: Non-conductive, frangible, radar/ILS-neutral, and corrosion-free; good for sensitive or harsh environments.
• Acrylic/Polycarbonate: Transparent, UV-stabilized, impact-resistant; used for locations needing visibility.
• Composites: Used for acoustic/hybrid solutions, providing sound absorption and sustainability benefits.

Applications and Use Cases

Taxiways and Aprons:
Protect service roads, parking, and equipment from jet blast during taxiing and engine run-ups.

Runway Ends and Holding Bays:
Shield sensitive areas from full-power engine thrust during takeoff/pre-departure checks.

Terminal Roadways and Parking Structures:
Prevent jet blast from affecting public infrastructure, often using visually integrated or transparent panels.

Engine Test Facilities (GREs):
Enable safe, quiet engine testing close to operational areas.

Military Airfields:
Provide operational security, aircraft protection, and blast mitigation for munitions or vehicle impact.

Design Considerations & Customization

• Aircraft Type and Power: Widebody jets require taller/stronger barriers.
• Proximity to Protected Area: Closer proximity increases deflection and strength requirements.
• Site Constraints: Modular/custom panels adapt to space limitations or existing infrastructure.
• Visual Requirements: Mesh or clear panels maintain operational visibility.
• Acoustic Needs: Acoustic panels or GREs used near noise-sensitive areas.
• Regulatory Compliance: All designs adhere to international and local standards for safety and quality.
• Environmental Factors: Materials and coatings are selected for climate, corrosion risk, and sustainability goals.

Conclusion

A blast fence is a critical safety feature at airports and airfields, essential for protecting people, infrastructure, and the operational environment from the hazards of jet blast. Through advanced engineering, careful material selection, and adherence to international standards, modern blast fences provide robust, customizable solutions for today’s complex aviation environments.

For airport operators, engineers, and planners, investing in high-quality, properly designed blast fences is vital for safe, efficient, and sustainable airport operations.