"Only one EEC discretes card serves both engines via the TMC, so both engines receive the same bleed demand information.". .. .Just trying to make sense of this, GR... (I thought I understood what was going on, but...). .. .I think I'm getting different trimming concepts muddled here..... .. .*You have trimming which compensates for slight differences in the position of two or more throttle levers (i.e. the type mentioned by Dan and discussed at length in a previous message thread on 747-400's). This happens during non-A/T and A/T controlled thrust ops on FADEC engines.. .*You have idle speed adjustment when Anti-Ice is on or when the flaps are }/= 23 deg.. .*Then you have trimming (if this is the right word) for (other) pneumatic/bleed demands.. .. .It's the last one that is giving me the most problems. What exactly does it do to the engine? Does it boost the N1 of the engine to a higher level.... or does it simply allow the engine speed to get back to where it was before you slowed it down by sucking off lots of bleed air from the compressor? (or am I simplifying things too much here by only mentioning engine speed). Does it allow the engine to brace itself for the anticipated extra bleed demand (so that the rpms remain the same when the bleed demands are made)?. .. .Re the EEC Discretes card: I see from my gathered information that, on FADEC engines at least, the Discretes card sends ECS/bleed valve data to the EEC via the TMC. Conceivably, with today's technology, a summary of all the demands/bleed valve positions could be relayed to the EEC from the TMC on databusses and the EEC could easily determine which bits of data are important to it and have each engine respond accordingly/uniquely, rather than have both engines responding to an "average" bleed demand determined by the TMC. Of course, with things running normally on the aircraft, bleed demands will be pretty much the same for both engines (even with the Bleed Isolation Valves closed) and individual engine responses might be a bit of overkill. But in other, non-normal, situations....?. .. .On CF6 FADEC engines, there seems to be no direct output to the EEC from the Discretes card. Does this mean the engine cannot compensate for bleed demands without the TMC being operative?. .. .Anyway, my aplogies for the rambling.. .. .Regards.. .Q.