Maximum Zero Fuel Mass

What is Maximum Zero Fuel Mass?

Maximum zero fuel mass (MZFM) is a structural weight limit defined for every aircraft. It represents the sum of the dry operating mass (aircraft, crew, catering, etc.) and the traffic load (passengers, baggage, cargo), but specifically excludes all usable fuel. Only unusable fuel is included in this calculation.

Why Does MZFM Exist?

The main reason for the zero fuel mass limit is to protect the aircraft's structure, particularly the wing roots. When the fuselage is heavily loaded but the wings are not supported by the weight of fuel, the bending moment at the wing root increases. The MZFM ensures these structural loads remain within safe limits.

How is MZFM Used in Practice?

• MZFM is a fixed value published in the aircraft's flight manual.
• During pre-flight mass and balance calculations, the sum of dry operating mass and traffic load must not exceed the MZFM.
• After confirming ZFM compliance, fuel is added to determine take-off mass and landing mass.
• The centre of gravity (CG) for the zero fuel mass condition must also be within the approved envelope.

Special Considerations

• In most aircraft, only wing fuel is excluded from ZFM; fuselage fuel may be included if specifically stated in the aircraft documentation.
• Exceeding MZFM is not permitted at any time, on the ground or in flight.
• Payload restrictions may apply if the planned traffic load would cause the ZFM to exceed the limit.

Related Terms

• Zero fuel mass (ZFM): the actual calculated value for a specific flight.
• Maximum zero fuel mass (MZFM): the published structural limit.
• Payload restriction: reducing traffic load to stay within MZFM.
• Structural mass limits: include MZFM, maximum take-off mass, and maximum landing mass.