Shoulders – Paved Area Adjacent to Runway or Taxiway

Definition

Shoulders in aviation refer to the paved or stabilized areas immediately next to the edge of a runway or taxiway. Their primary role is to provide lateral support to the pavement, prevent edge deterioration, facilitate safe aircraft excursions, and help keep foreign object debris (FOD) away from operational surfaces. While not designed for regular aircraft movement, shoulders are vital in maintaining the structural integrity and long-term safety of airport movement areas.

Purpose and Functions

Shoulders are critical for several reasons:

• Edge Support: They prevent pavement edge failure by distributing occasional loads from aircraft wheels straying from the main surface.
• Safety Buffer: Shoulders serve as a safety margin for aircraft in case of minor excursions, reducing the risk of structural damage and incidents.
• FOD Prevention: Paved shoulders inhibit the migration of debris and vegetation onto operational surfaces, which is crucial for jet engine safety.
• Drainage and Maintenance: Designed with a slight slope, shoulders ensure proper water runoff and provide a stable base for maintenance vehicles and snow removal equipment.
• Regulatory Compliance: Meeting FAA/ICAO requirements for shoulders is mandatory for airport certification and ongoing operations.

Regulatory Framework: FAA & ICAO Standards

Shoulder design and maintenance are regulated by both the FAA (United States) and ICAO (international). Key documents include:

• FAA AC 150/5300-13A: Specifies design criteria for shoulder width and structure based on aircraft size.
• FAA AC 150/5340-1M: Details marking and maintenance standards.
• ICAO Annex 14, Volume I: Sets international requirements for shoulder width, surface, and drainage.
• ICAO Aerodrome Design Manual, Part 2: Offers guidance on construction and operational considerations.

Typical standards:

• Runway shoulders for large aircraft (Boeing 747, A380, etc.): At least 7.5 meters (25 feet) wide on each side.
• Taxiway shoulders: Minimum 6 meters (20 feet), depending on aircraft type.

Physical and Structural Characteristics

• Width: Determined by the largest aircraft using the surface—wider for larger, wide-body jets.
• Surface: Usually asphalt or concrete, but with less structural depth than the main pavement. Shoulders must resist rutting, erosion, and FOD generation.
• Slope: Typically 1.5%–2% away from the main pavement to encourage drainage.
• Transition: Smooth interface with both operational pavement and surrounding unpaved areas.
• Structural Strength: Designed for occasional aircraft loading, not continuous use.

Marking Standards and Visual Cues

• Runways: Shoulders are marked with solid yellow lines or yellow chevrons.
• Taxiways: Marked with a continuous yellow edge line; additional markings may be added in complex layouts.
• Visibility: Markings are inspected regularly and maintained for high visibility and distinction from operational pavement markings.

Lighting and Visual Aids

• No dedicated lighting is installed for shoulders. Runway and taxiway edge lights define operational boundaries.
• Lights must be frangible and kept clear of shoulder zones to avoid confusion or damage during excursions.
• Reflective markers or painted aids may be used in rare cases, subject to regulatory approval.

Maintenance and Inspection Protocols

• Routine Inspections: Regular checks for surface damage, debris accumulation, marking visibility, and drainage function.
• Debris & FOD Removal: Mechanical sweepers, vacuum systems, and manual cleaning as needed.
• Surface Repairs: Prompt attention to rutting, cracking, or elevation differences (not exceeding 3 inches/76 mm with main pavement).
• Drainage Maintenance: Ensures water flows away from operational areas.
• Documentation: All activities are logged for regulatory compliance (e.g., under FAA Part 139).

Safety Considerations

• Shoulders are not for regular aircraft use; excursions are considered abnormal.
• Personnel and vehicles must avoid unnecessary access to prevent surface damage and FOD.
• Markings/colors are standardized (yellow for shoulders) to avoid confusion, especially in low-visibility conditions.
• Incidents involving shoulder use may trigger reviews and corrective actions for airport design and operations.

Regulatory and Reference Integration

Key references for airport operators:

• FAA AC 150/5300-13A: Airport Design
• FAA AC 150/5340-1M: Standards for Airport Markings
• 14 CFR § 139.305: Paved Areas
• ICAO Annex 14, Volume I: Aerodrome Design and Operations
• ICAO Aerodrome Design Manual, Part 2
• Additional guides: Aeronautical Information Manual, ACRP Apron Planning Guidebook

Associated Terms

• Federal Aviation Administration (FAA): U.S. authority over civil aviation, including airport regulations.
• Surface Painted Holding Position: Markings at runway/taxiway intersections for aircraft hold positions.
• Runway Holding Position Marking: Indicates where aircraft must stop before entering a runway.
• Terminal Apron: Paved area for aircraft parking, loading, and service near terminals.
• Pavement Edge: Boundary between load-bearing pavement and shoulder or unpaved area.

Summary

Airport shoulders, though not part of the main operational pavement, are essential for runway and taxiway safety, integrity, and maintenance. Their design and upkeep are strictly governed by FAA/ICAO standards, ensuring that airports can efficiently manage both routine operations and unexpected incidents. Regular inspections, proper marking, and diligent maintenance of shoulders help preserve the safety and reliability of airport movement areas, supporting the growing demands of modern aviation.