Grass Runway (Unpaved Runway with Grass Surface)

A grass runway—sometimes called a turf or sod runway—is a prepared airfield surface covered with living grass, used for aircraft takeoff, landing, and taxiing. Unlike paved runways of asphalt or concrete, grass runways rely on the stability of compacted soil and the resilience of turf. These runways are a subset of unpaved or semi-prepared runways, as recognized by the International Civil Aviation Organization (ICAO) in Annex 14, and are common at general aviation (GA) airports, private strips, glider clubs, and in agricultural or special operations.

What Is a Grass Runway?

A grass runway is a purpose-built, level, and obstruction-free strip with a surface of maintained grass over compacted earth. It must provide adequate load-bearing capacity, minimal undulation, and effective drainage to prevent soft, muddy, or uneven patches. ICAO defines unpaved runways as “runways having a surface that is not paved with compacted or bound material such as concrete or bituminous mixes.” Grass runways are mainly used by light aircraft, with surface qualities such as grass species, root density, soil compaction, and smoothness directly affecting their performance and safety.

Key Characteristics of Grass Runways

• Surface Material: Natural grass over compacted soil. Grass species are chosen for local climate, durability, and frequency of use. Geocell reinforcement or cellular confinement systems may be used in modern installations.
• Load-Bearing Capacity: Most grass runways support aircraft with a Maximum Takeoff Weight (MTOW) below 5,700 kg (12,500 lbs). Heavier loads require special reinforcement and maintenance.
• Dimensions: Private strips may be as short as 300 m (1,000 ft); public or crosswind grass runways may exceed 1,200 m (3,900 ft) in length.
• Drainage: Crowned grading and, if necessary, sub-surface drains prevent waterlogging and rutting. Proper drainage is crucial for safety.
• Markings: Typically minimal—edge and threshold markings may use painted stones, cones, flags, or mowing patterns.
• Lighting: If present, it is usually low-intensity, solar-powered, or portable.
• Weather Sensitivity: Usability varies with rain, snow, drought, or freezing, and runways may close seasonally or after adverse weather.

How Grass Runways Are Used

Grass runways cater to a broad range of aviation activities. Typical users include:

• General aviation pilots of light, single-engine aircraft, gliders, ultralights, and vintage planes.
• Flight training operations, especially for teaching soft-field techniques.
• Glider and soaring clubs, which benefit from the forgiving surface for gliders and minimal undercarriage wear.
• Agricultural, banner towing, and skydiving operations, which require flexible, low-speed access near work sites.
• Recreational and vintage aviation for authenticity and reduced wear on classic aircraft.
• Public-use airports as crosswind or overflow runways.
• Military and emergency operations, where temporary grass strips are rapidly constructed for logistics and humanitarian needs.

Typical Use Cases and Examples

• Poplar Grove Airport (C77), Illinois, USA: Features two grass strips in addition to a paved runway.
• Lasham Airfield (EGHL), UK: Extensive grass areas for glider launches.
• Elmira-Corning Regional Airport (KELM), New York: Supports glider clubs with maintained grass surfaces.
• Reims-Prunay (LFQA), France / Popham Airfield (EGHP), UK: Public-use airports with active grass runways.
• Private farm strips, remote ranches, and agricultural sites: Custom-tailored for owner needs.
• Military and humanitarian expeditions: Construct temporary grass airstrips for rapid deployment.

Operational Considerations

Aircraft Suitability

Grass runways are suitable for light aircraft, especially those with tailwheel gear or low-pressure tires. Heavy aircraft are generally not recommended unless the runway is specially built and maintained.

Performance Impacts

• Takeoff and landing rolls are longer due to higher rolling resistance.
• Directional control is more difficult, especially if uneven, crowned, or soft.
• Braking is less effective, particularly on wet grass.

Environmental and Weather Factors

• Soil moisture, grass height, and surface firmness change with the weather.
• Drainage and grading are critical to maintaining usability.
• Inspections (walking the strip or low passes) are essential before use.

Maintenance Routines

• Frequent mowing to optimal grass height (3–6 inches).
• Rolling and compaction to flatten ruts.
• Aeration, fertilization, and reseeding as needed for turf health.
• Repair of divots and surface defects after heavy use or adverse weather.

Safety Practices

• Soft-field takeoff and landing techniques are necessary.
• Continuous surface assessment before operation.
• Field etiquette: repairing disturbed turf and avoiding sharp turns.

Regulatory Context

FAA Guidance

• FAA Advisory Circular 150/5300-13B outlines grass runway design, grading, surface prep, and maintenance.
• Surface inspections and NOTAMs are required for public-use grass runways.
• Pilot responsibility to confirm suitability before use.

ICAO Guidance

• Annex 14, Volume I: Details on surface coding, width, grading, and obstacle clearance.
• National requirements may set more specific standards.

Economic and Environmental Analysis

Cost Effectiveness

• Lower initial construction and maintenance costs compared to paved runways.
• Enables aviation access in rural, remote, or low-traffic areas.
• Neglect can lead to deterioration and higher restoration costs.

Sustainability and Environmental Impact

• Lower carbon footprint and less use of heavy materials.
• Promotes biodiversity and natural water infiltration.
• Visually and ecologically integrates with surroundings.
• Wildlife hazards are more common and must be managed.

Limitations

• Weather-dependent usability.
• Unsuitable for large or high-speed aircraft.
• Regular maintenance is essential to ensure safety.

Construction Fundamentals: Step-by-Step Guide

1. Site Selection: Flat, well-drained, and free from obstacles.
2. Regulatory Check: Compliance with zoning, environmental, and aviation authorities.
3. Grading and Drainage: Crowned grading, possible sub-surface drains.
4. Soil Preparation: Remove rocks, till and compact soil.
5. Sodding/Seeding: Choose suitable grass, establish turf, maintain irrigation.
6. Marking and Lighting: Use visible, durable markers; portable or solar-powered lighting if needed.
7. Ongoing Maintenance: Mowing, rolling, aeration, fertilizing, and repair.

Flight Operations: Best Practices

• Pre-Flight: Inspect the runway for firmness, grass height, and obstacles.
• Takeoff: Use soft-field techniques, maintain back-pressure, and accelerate in ground effect.
• Landing: Approach at the lowest safe speed, use aerodynamic braking, avoid heavy wheel braking.
• Taxiing: Go slow, avoid soft/rutted areas, repair turf after use.

Common Misconceptions

• “Grass runways are inherently unsafe.” Not true when properly maintained and used by trained pilots.
• “Only private strips use grass.” Many public-use airports maintain grass runways for GA and training.
• “FAA or ICAO design standards prohibit grass strips.” Both organizations explicitly recognize and provide standards for grass runways.

Grass runways play a vital role in global aviation—supporting flight training, recreation, glider operations, agricultural work, and rural connectivity—while offering economic and environmental advantages. When constructed and managed to modern standards, they provide safe, sustainable access for a wide range of aircraft and operators.