Originally Posted by
acheo
According to Boeing, when N2 reaches 9%, EEC dies and A/T should disconnect. This is engineering data. We have thrown a seized engine malfunction to get this N2=0% and could never get the A/T disconnect.
Which engine - PW4000 or CF6-80C2 FADEC? 'Stay Alive' speed for the EEC on the PW4000 is quite a bit lower than 9% - it varies a bit engine to engine but ~4% N2 is typical. CF6 is a bit higher, more like ~6% N2. In either case N2 will remain high enough to keep the EEC from dropping off line except at very low airspeeds. Further, on the CF6 the EEC is powered via the fuel switch - so long as the switch is in RUN the EEC will remain powered, even with a seized N2 rotor. The PW4000 is different and is not powered via the fuel switch unless your engines are equipped with something called an SCU (not common on the 767 except for the ones Delta bought).