Aircraft Mass (Weight) Breakdown
Definitions of various types of aircraft mass (i. e., weight) (see Section 4.5) are repeated here for the convenience of readers.
MEM (manufacturer’s empty mass) (8.1)
is the mass of an aircraft as it rolls out of the factory before it is taken to a flight hangar for the first flight.
OEM (operator’s empty mass) = MEM + Crew + Consumable (8.2)
The aircraft is now ready for operation (residual fuel from the previous flight remains).
MTOM (maximum takeoff mass) = OEM + Payload + Fuel (8.3)
The MTOM is the reference mass loaded to the rated maximum. This is also known as the brake release mass (BRM) ready for takeoff.
Aircraft are allowed to carry a measured amount of additional fuel for taxiing to the end of the runway, ready for takeoff at the BRM (MTOM). This additional fuel mass would result in the aircraft exceeding the MTOM to the maximum ramp mass (MRM). Taxiing fuel for midsized aircraft would be approximately 100 kg, and it must be consumed before the takeoff roll is initiated – the extra fuel for taxiing is not available for the range calculation. On busy runways, the waiting period in line for takeoff could extend to more than an hour in extreme situations.
MRM (maximum ramp mass) « 1.0005 x MTOM (very large aircraft) to
1.1 x MTOM = MTOM + fuel to taxi to end of runway for takeoff (8.4)
This is also known as the maximum taxi mass (MTM) and it is heavier than the MTOM.
ZFM (zero fuel mass) = MTOM minus all fuel (nonusable residual fuel remains)