Estimating Takeoff Thrust from Surveillance Track Data

Emissions inventory calculations for airports, using standard emissions inventory reporting methods, are inflated due an assumption of use of maximum takeoff thrust. To enhance the operational life of jet engines and reduce fuel burn, airlines frequently use reduced thrust (i.e. Derated or Flex Temperature thrust) for the takeoff procedure. Without access to internal airline “load sheet” paperwork or flight data recorders it is not possible to identify the thrust setting for each departure operation and account for the reduced thrust in emissions inventory calculations. This paper describes an approach to estimate the takeoff thrust using a combination of radar surveillance track data, aerodynamic model, and weather data. Groundspeed and rate-of-climb from gear-up altitude to the thrust reduction altitude (1500’) are derived from surveillance track data. These values are combined with recorded wind speed data from airport weather data, an estimation of takeoff weight, and a steady-state aerodynamic model, to derive an estimate of takeoff thrust for each operation. Sensitivity analysis shows the importance of the estimate of takeoff weight in the calculations. An approach based on stage-length is used to estimate takeoff weight. A case study for flights from Chicago O’Hare airport exhibited an average takeoff thrust of 86% of maximum takeoff thrust. The implications and limitations of this approach are discussed.