Originally Posted by
RVDT
So if you have a stronger (better performing) N1 or Ng than the other you must have Q splits all the time?
Correct. The DECU match N1 for load sharing. RFM Part 2 Section 1 pg 1-10 refers, together with all the other intricacies of the DECU. And just to extend on that concept, the pilot has no control over TQ matching with the engines in automatic mode. So even if the pilot wanted to, he can't match/trim the TQ output of each engine. The DECU will only allow N1 matching until TQ limits are reached. If one engine has a better TQ margin than the other, the DECU will hold it at the TQ limit and then N1 will split until the weaker engine reaches its TQ limit. The DECU gets pretty busy at that point with soft limiting logic, and eventually blow-away logic, if you keep demanding more power. When you back off from a TQ limit the DECU reverts back to N1 matching for load sharing. It's the way the system is designed.
Unlike helicopters like B212 or B412, which have a TQ split limitation, there is no such limitation in a S76 fitted with DECU. As long as the engines make power assurance, flying with DECU matched N1 and a TQ split due to engines having different margins is no big deal.