Structural, Performance, and Regulated Limits in Aviation

Introduction

• Understanding structural, performance, and regulated limits is crucial for the safe conduct of flights.
• These limits help manage the mass of an aircraft during different phases of a flight as the fuel burns.
• Key points during the flight regarding mass:
  • Takeoff Mass: Total mass minus taxi fuel.
  • Landing Mass: Takeoff mass minus trip fuel.

Structural Mass Limitations

• Definition: Hard limits related to the aircraft's structure.
• Key types:
  • Maximum Ramp Mass: Limits based on the gear wheel assembly when taxiing.
  • Maximum Structural Takeoff Mass: Maximum weight the aircraft can carry during takeoff.
  • Maximum Structural Landing Mass: Typically less than takeoff mass; accounts for the impact force on landing.
  • Maximum Zero Fuel Mass: Concerns structural integrity at the wing-body junction when fuel is depleted.
• Considerations:
  • Maximum structural landing and zero fuel masses can limit takeoff if exceeding them would breach safety upon reaching the destination.

Example Calculation

• Given:
  • Max Structural Landing Mass: 40,000 kg
  • Max Structural Takeoff Mass: 45,000 kg
  • Max Zero Fuel Mass: 39,000 kg
  • Takeoff Fuel: 3,000 kg
  • Trip Fuel: 2,000 kg
• Calculation shows that a limiting structural mass can lead to adjustments in payload or fuel to ensure safety.

Performance Limitations

• Definition: Limits due to engine performance and environmental conditions.
• Influencing Factors:
  • Air density (preferred cold, dense air at sea level).
  • Runway length and altitude (e.g., airports at high altitudes with short runways can limit performance).
• Types:
  • Performance Limited Takeoff Mass
  • Performance Limited Landing Mass

Regulated Limits

• Regulated Takeoff/Landing Mass: The lower value between structural and performance limits used for calculations.
• Example:
  • If performance limit is more restrictive at a high-altitude desert airport, it becomes the regulated limit.

Summary

• Acronyms and Terms:
  • Actual Takeoff Mass (ATOM)
  • Actual Landing Mass (ALM)
  • Structural Limits: MRM, MSTOM, MSLM, MZFM
  • Performance Limits: PLTM, PLLM
• Takeaway:
  • Use the lowest between structural and performance limits for legal compliance and safety.