In preparation for an upcoming interview I came across something that I can't find defined anywhere. Can someone please explain exactly what "engine rollback" is? The original source for asking about this is:

http://www.wweek.com/html/king56-062597.html

After some research I found an Emergency AD on the subject.

I is obviously a reduction in performance somehow...but due to what? Is this just an instrument thing as I understand from the mention of software in the AD or is it really losing power on one of the engines?

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/0dd44fe2beb1f516862571f9006b5dad/$FILE/2006-20-51.pdf