The quantity and rate of fuel burnt during aircraft operations forms the basis of all emission inventory work at airports. The international standard for calculating the fuel burn and emissions produced is the Landing and Takeoff (LTO) cycle of the International Civil Aviation Organization (ICAO), and this forms the basis for many emission inventory models. The acquisition of real-time cockpit flight data recorder (CFDR) information by the Emissions Measurement and Modeling division of the VOLPE National Transportation Systems Center provided a unique opportunity to compare actual fuel flow and time-in-mode under operating conditions and compare this to the ICAO standard for aircraft operations. There is tremendous variety in fuel flow patterns, rates of fuel flow, and times-in-mode. Only 67% of the flights analyzed show a classic transition from takeoff to climbout. For these flights, actual take-off times are significantly higher, and climbout times lower, than the ICAO standard. The remaining 33% of the flights showed essentially flat line fuel flow profiles, with some exceptions. Fuel flow rates are highly variable. All aircraft show some fuel flow rates indicative of reduced (derate) thrust departures, with fuel flow values ranging 75-80% of ICAO engine certificated values. In general, total fuel burn is overestimated by the ICAO method. The values determined by ICAO matched favorably to the CFDR totals for four-engine aircraft, but grossly over predicted total fuel burn for the twin-engine aircraft in this study. Further investigation will compare this data to fuel burn and emissions predicted by performance models.
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