From Flightglobal:
Qantas' spokesman says the stub pipe defect is unrelated to the carrier's announcement last week that 16 of its Trent 900 engines require "modification to the latest standard or full replacement".
"That is not related to the stub pipe issue," the spokesman says. "The only stub pipe [fault] we have found is on this aircraft awaiting delivery." He declines to specify why the 16 other Trent 900s require change.
Three more Trent 900s found with manufacturing defect
So if not the stub pipe, why is QF changing 16 engines?
Is this to bring A mod and B mod engines to C mod standard? What does the C mod have the A and B mods don't?