Maximum Takeoff and Landing Mass

Maximum Takeoff Mass (MTOM) Explained

Maximum takeoff mass (MTOM) is the highest weight at which an aircraft is permitted to begin its takeoff roll. This limit is established by the aircraft manufacturer and certified by aviation authorities, based primarily on structural strength. However, operational limitations—such as runway length, climb performance, obstacle clearance, and environmental conditions—may further restrict the allowable takeoff mass for a specific flight. The lowest value from all applicable limits (structural, field length, climb, obstacle, tyre, etc.) becomes the regulated takeoff mass (RTOM) for that departure.

Maximum Landing Mass (MLW) Explained

Maximum landing mass (MLW) is the greatest weight at which an aircraft is certified to land under normal conditions. Like MTOM, MLW is a structural limit, but operational factors can impose stricter constraints. For each landing, the actual landing mass must not exceed the lowest of:

• The structural MLW
• The landing field length limited mass (based on runway length and conditions)
• The approach and landing climb limited masses (based on engine-out climb performance)

The regulated landing mass (RLW) is the lowest of these values. Exceeding MLW can result in structural damage or inadequate stopping/climb performance.

How Limits Are Determined

• Structural Limits: Set by design and certification; found in the Aircraft Flight Manual (AFM).
• Performance Limits: Calculated for each flight using charts and tables, considering runway length, slope, surface, wind, temperature, and altitude.
• Climb Limits: Ensure the aircraft can achieve required climb gradients, especially after engine failure.
• Field Length Limits: Ensure the aircraft can stop or take off within the available runway.

Practical Application

Flight crews must calculate and compare all relevant limits before every takeoff and landing. The lowest applicable mass governs operations, ensuring compliance with regulations and maintaining safety margins.