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20 Figure V-4. Recorded fuel flow from an A320's Figure V-5. Relative emission index adjusted taxiway phase is shown as a function of time since for fuel flow rate for the example calculation engine start. The reference ICAO 7% thrust fuel described in the text. flow is depicted in the horizontal line, and the trace is derived from the digital flight data record. The actual reported fuel flow has been divided by two since the original data source represents the sum from two engines. the effects of both ambient temperature and fuel flow rate. The contours reflect that some of the dependence on fuel flow has been softened, relative to the dependence in Figure V-2. V.2Example Application of the Model Figure V-6. Fuel dependent adjusted emission The overall approach adopted here is to convert the rate is depicted for two cases. The brown trace is recorded fuel flow rates to instantaneous emission rates the example taxiway operation, and the light red using both the temperature and fuel flow dependent emission trace is the ICAO emission rate for idle phase. index. The steps associated with the fuel flow conversion only are outlined here for a single operation for an A320 aircraft being operated at Zurich Airport. The ambient tempera- Figure V-1. In this example, the extrapolation is assumed to ture during the operation was within 2°C of the reference be linear above the 7% thrust value. temperature (15°C) and thus the temperature correction is very small. HC ( Fuel Flow ) s = 1 + -52 [ Fuel Flow - FF7% ] In Figure V-4, shortly after engine start a sub-7% fuel flow HC ( FF7% ) kg is established. Periodically, the fuel flow actually increased above the 7% thrust, presumably to achieve "breakaway" thrust-- In Figure V-6 the UHC emission rate is calculated for the the point where the aircraft begins to move. time-dependent fuel flow rate from the example operation. The units of the emissions index correction factor are grams As noted earlier, the fuel flow dependent model is probably not UHC/grams UHC7% kg fuel7%/kg fuel. This is a multiplicative very accurate for the breakaway accelerations, but this example factor to the 7% thrust emission index; however, the potential at least estimates this portion of the fuel flow only dependence. difference in fuel flow needs to be treated explicitly. The ratio of the integrated emission for the example operation Figure V-5 depicts the estimated adjusted emission index to the ICAO 7% emission of equivalent duration is 1.34 for factor for the example fuel flow time series depicted in this portion of the LTO.