What are the categories of aircraft in ICAO?

ICAO Aircraft Categories and Their Impact on Runway Design

The International Civil Aviation Organization (ICAO) has established a system for categorizing aircraft based on their performance and operational characteristics. These categories play a crucial role in runway design and strength requirements, affecting both flexible and rigid pavement structures.

Categories of ICAO Aircraft

ICAO categorizes aircraft into several groups based on factors such as maximum take-off weight, wingspan, and landing gear configuration. The primary categories are:

• Code A: Small aircraft with a maximum take-off weight of less than 5,700 kg (12,500 lbs)
• Code B: Medium-sized aircraft with a maximum take-off weight between 5,700 kg and 15,000 kg (12,500 lbs and 33,000 lbs)
• Code C: Large aircraft with a maximum take-off weight between 15,000 kg and 300,000 kg (33,000 lbs and 660,000 lbs)
• Code D: Very large aircraft with a maximum take-off weight greater than 300,000 kg (660,000 lbs)

Influence on Runway Design

The category of aircraft that a runway is designed to accommodate has a significant impact on its structural requirements. Heavier aircraft generate greater loads on the pavement, which must be accounted for in the design process.

Specifically, the following factors are influenced by the ICAO aircraft category:

• Runway thickness: Thicker pavements are required for runways designed for heavier aircraft.
• Pavement strength: The pavement must be sufficiently strong to withstand the loads imposed by the aircraft’s wheels and tires.
• Subgrade strength: The soil beneath the pavement must also be strong enough to support the aircraft’s weight and the loads it generates.

Subgrade Strength Categories

Subgrade strength is classified into several categories, which correspond to varying modulus of elasticity values. For example:

• CAT A: Represents high-strength subgrades
• CAT B: Represents medium-strength subgrades
• CAT C: Represents low-strength subgrades

The appropriate subgrade category for a particular runway is determined based on factors such as soil type, moisture content, and the expected traffic loads.

Conclusion

ICAO aircraft categories serve as a fundamental input for runway design and strength requirements. By understanding the characteristics of different aircraft categories, engineers can design runways that are safe, efficient, and capable of handling the anticipated aircraft traffic. Furthermore, considering the strength of the subgrade is essential to ensure the long-term integrity of the runway pavement.