For SA Airbii, my understanading is that PERF only mathematically increases the estimated fuel burn as calculated by FMS.
The antenna would increase real burn, and eventually through APM it will be reflected in the revised perf factor. My experience is that the actual burn - all the usual suspects being equal - versus OFP versus FMC predictions is within 200 kgs on a typical 4 hr sector. And inside 3 minutes.
Did you see the FCOM chapters on PERF factor?
Last edited by FlightDetent; 15th February 2017 at 22:12.