Mass Limit Calculations: MTOM, MLM, MZFM, and Regulated Traffic Load

031-02-02Pablo Asensio Martínez2026-04-011 min

Determining Maximum Traffic Load

To find the maximum traffic load allowed for a flight, we must calculate the load permitted by each of the three main limits:

  1. Maximum Take-Off Mass (MTOM) Limit.
  2. Maximum Landing Mass (MLM) Limit.
  3. Maximum Zero Fuel Mass (MZFM) Limit.

The lowest of the three resulting traffic loads is the limiting factor.

1. MTOM Limit

$ \text{Max Traffic Load (MTOM)} = \text{MTOM} - \text{DOM} - \text{Take-off Fuel} $

2. MLM Limit

Since the aircraft burns trip fuel, it can take off heavier than the landing limit. $ \text{Max Take-off Mass allowed by MLM} = \text{MLM} + \text{Trip Fuel} $ $ \text{Max Traffic Load (MLM)} = (\text{MLM} + \text{Trip Fuel}) - \text{DOM} - \text{Take-off Fuel} $ Alternatively: Max Traffic Load = MLM - DOM - Reserve Fuel (Landing Fuel).

3. MZFM Limit

$ \text{Max Traffic Load (MZFM)} = \text{MZFM} - \text{DOM} $ Note: Fuel is not part of ZFM.

Example Calculation

Given:

  • DOM: 35,000 kg
  • MTOM: 65,000 kg
  • MLM: 55,000 kg
  • MZFM: 52,000 kg
  • Trip Fuel: 8,000 kg
  • Take-off Fuel: 15,000 kg

Calculate Max Traffic Load:

  1. Based on MTOM: $65,000 - 35,000 - 15,000 = 15,000 \text{ kg}$
  2. Based on MLM:
    • Max mass at take-off allowed by landing limit: $55,000 + 8,000 = 63,000 \text{ kg}$
    • Traffic Load: $63,000 - 35,000 - 15,000 = 13,000 \text{ kg}$
  3. Based on MZFM: $52,000 - 35,000 = 17,000 \text{ kg}$

Result: The lowest value is 13,000 kg (limited by Landing Mass).