A664
My mistake, yes the EEC Channel A/B selection at start is normally alternated.
This prevents the accumulation of dormant faults, normally.
However, between starter cut-out and Idle, the EEC may select a channel change. If one Channel has defects, the other channel will be selected for control. Also, if both channels have defects, the channel in control at identification of defects gets (retains) control.
As to degradation, (#1, #4). The EEC monitors/controls the Engine through motors, solenoids, and relays, while transmitting data to the a/c (Cockpit).
The Channel that is in control can make use of the standby channels logic, inputs and outputs. If a like output is faulted in both, the control Channel is the one that remains in operation. So the EEC communicates with the a/c. It maintains and supplies data for fault analysis to other systems on the aircraft. To what extent each of the other EECs is contingent on the failure (or failure reads) of one or both Channels of #2 I am unclear. Can you help with that??
RE: Fuel cutoff. One assumes that the "protections" limiting EEC authority to halt fuel supply include Overheat, and Fire. At the Burst, N3 was over limit. The Fuel is supplied by the HP Pump, which is driven by the Gearbox shaft, which in turn is connected to N3. Prior to 'shutdown' of #2, one assumes the HP was operating overlimits as well, and for a brief time may have been flooding the nozzles with fuel. Since the assumption is made that N3 at 98% was caused by fuel supply continuing past N1 N2 failure to turn, one also assumes the supply had continued, the supply may have been too "plentiful", and that EEC and or cockpit controls had lagged in protecting the engine from burst. Back to DEP, boosted thrust logic, etc.?
Last edited by bearfoil; 8th Jan 2011 at 17:00.