The second peak from about 30 - 35% N1 (Bendix system) and occurs at the completion of the start derichment cycle in the FCU.
As John has stated, the derichment in the start cycle keeps the engine away from surge and high TOT. (15 to 30% N1.)
The basic acceleration schedule takes over from about 30% N1 allowing more fuel to the nozzle.
Nick: I'm trying to come to terms with your explanation of the fuel nozzle causing the 2nd peak. At this point I have to disagree.
The FCU initiates the fuel flow, the nozzle allows it. Also it was my understanding that the secondary flow through the nozzle occured at a higher power setting, but not during starting. If a peak occured as the secondary fuel started flowing then why does the temp reduce when the engine obtains idle RPM?
Last edited by sprocket; 6th Oct 2003 at 20:19.