Old 20th Mar 2016, 06:33
  #11 (permalink)  
FE Hoppy
Join Date: Sep 1998
Location: wherever
Age: 51
Posts: 1,619
There is no reason apart from some joe bloggs who wrote the rule.

You can use a derate if you have the performance figures for contaminated with derate. This is a cost to the manufacturer to produce the figures.

There is no physical reason to not reduce with assumed to the equivalent derate thrust and you have the advantage of having more thrust available after the failure. But it's all about the cost of producing the performance data.
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