Methods and apparatus for measuring liquid fuel flows within a conduit are disclosed. An example flow sensor may include a conduit arranged to flow fuel therethrough along a flow axis, the conduit defining a flow area orthogonal to the flow axis. The flow sensor may further include a first transducer arranged to direct a first signal through the conduit proximate the flow area to a second transducer, the second transducer being arranged to direct a second signal through the conduit proximate the flow area to the first transducer, the first transducer being spaced apart from the second transducer by a signal path length, and in a direction parallel to the flow axis by an axial distance. The fuel flow measuring system may further include a processor arranged to calculate a fuel mass flow rate based on first and second signal transit times, known fuel properties and a fuel temperature.