1. Device for determining a measurement of mass fluid flow for a combustion chamber comprising a fluid metering device and a means of measuring the position of metering device known as the measured position, characterised in that it comprises: a mass flow meter for measuring a mass flow of fluid known as the measured flow, a hybridisation device suitable for determining an actual mass flow of fluid comprising: a first input comprising a set-point value (WFset-point) of the mass flow sought or a set-point value (Xset-point) of the position of the metering device sought, a prediction unit ( 26 ) capable of determining, from the first input and variables of state comprising the actual mass flow (WFactual) and parametric unknowns (IP), estimated values comprising the estimated position of the metering device ({circumflex over ( )}Xmetering device) and the mass flow ({circumflex over ( )}WF flow meter), a second input comprising the measured position of the metering device (Xmetering device) and the measured fluid mass flow (WFflow meter), a calculator of residues ( 30 , 22 , 20 ) capable of determining a first residue (Rmetering device) between the measured position of the metering device and the estimated position of the metering device and a second residue (Rflow meter) between the measured fluid mass flow and the estimated fluid mass flow, a correction unit ( 24 ) capable of determining from the first and second residues corrections capable of being applied by the estimation unit to the variables of state (Wfactual, IP).