Structural, Performance, and Regulated Limits in Aircraft

Introduction

• Lecture on structural, performance, and regulated limits in the context of aircraft mass and balance.
• Importance for safe flight conduct.
• Previous class covered mass at various flight points and its change due to fuel burn.

Key Mass Definitions

• Takeoff Mass: All-up mass minus taxi fuel.
• Landing Mass: Takeoff mass minus trip fuel.

Structural Mass Limitations

• Related to the physical structure of the aircraft.
• Cannot be exceeded.
• Main structural limits:
  • Maximum Ramp Mass
  • Maximum Structural Takeoff Mass
  • Maximum Structural Landing Mass
  • Maximum Zero Fuel Mass

Descriptions

• Maximum Ramp Mass: Limit of gear wheel assembly during taxiing.
• Maximum Structural Takeoff Mass: Maximum weight plane can carry into the air.
• Maximum Structural Landing Mass: Less than takeoff mass due to landing impact.
• Maximum Zero Fuel Mass: Concerns wing root forces when wings are unloaded.

Importance

• Maximum Structural Landing Mass can be a limiting factor during takeoff.
• Maximum Zero Fuel Mass can limit takeoff if exceeded after fuel burn.

Example Calculation

• Given limits: Structural Landing Mass = 40,000 kg, Takeoff = 45,000 kg, Zero Fuel = 39,000 kg.
• Takeoff Fuel = 3,000 kg, Trip Fuel = 2,000 kg.
• Limiting mass calculated at 42,000 kg to ensure compliance with landing and zero fuel constraints.

Practical Use

• Example problem with an aircraft:
  • Maximum Structural Takeoff Mass = 65,000 kg
  • Dry Operating Mass = 45,000 kg
  • Traffic Load = 10,000 kg
  • Required Fuel = 15,000 kg
• Total mass exceeds structural limit; solution involves reducing traffic load.

Performance Limitations

• Influenced by engine performance and runway conditions.
• Preferred conditions: Cold, dense air, long runway.
• High-altitude, hot, short runways reduce performance limits.

Performance Limits

• Performance Limited Takeoff Mass
• Performance Limited Landing Mass
• Often more restrictive than structural limits in challenging conditions.

Regulated Limits

• Regulated Takeoff Mass: Lower of structural or performance limit.
• Regulated Landing Mass: Similarly derived from performance vs. structural constraints.

Summary of Key Points

• Acronyms:
  • Actual Takeoff Mass (ATM)
  • Actual Landing Mass (ALM)
  • Maximum Structural Takeoff Mass (MSTOM)
  • Maximum Structural Landing Mass (MSLM)
  • Maximum Zero Fuel Mass (MZFM)
• Structural and performance factors determine regulated limits.
• Regulated limits ensure compliance with both performance and structural constraints for safe operations.