Summary of the Operating Masses

Summary

Basic Empty Mass (BEM) = Start mass , found in the weighing manual

Dry Operating Mass (DOM) = When we add all the unusable fuels, fluids, equipment, catering, chemicals, etc.. to the BEM. The crew and their baggage is included in the DOM.
It is the mass of the aircraft ready for operation but without the passengers, cargo and (useable) fuel.

Zero Fuel Mass (ZFM) = When we add the traffic load (passengers, cargo, mail, ...) to the DOM. The only thing missing is the take off fuel.

Operating Mass (OM) = When we add the take off fuel to the DOM. The only thing missing is the traffic load.

Useful Load (UL) = Consists of both the Traffic Load and the Take Off Fuel.

Take Off Mass (TOM) = Mass of the aircraft ready at the start of the take off run.

Landing Mass (LDM) = Mass of the aircraft when landing at destination, it is the take off mass minus the trip fuel.

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Formulas

Having a good understanding of the summary (image) below and the formulas will help you solve the Questions on this subject in no time!

TOM - DOM = UL

TL + T/O FUEL = UL

TL = ZFM - DOM

T/O FUEL = OM - DOM

T/O FUEL = BLOCK FUEL - TAXI FUEL

DOM + T/O FUEL = OM

DOM + TL = ZFM

TOM + TRIP FUEL = LDM