Trent 972
I'm still waiting for you to prove that the FAA wasn't happy with the Trent certification as you claimed yesterday.
The circular implies "Here is a way to accomplish vibration testing that is acceptable to us, but there are other way that may be acceptable as well." It is a unhappy day to have spent $1M or $2M on an engine test to only learn it didn't meet the certification criteria in the FAA's eyes.
I think you misunderstood what this comment meant, it wasn't a claim the FAA was unhappy. It was a statement in general to explain why the FAA guidance circulars exist in addition to the certification requirements. It is to prevent misunderstanding or misinterpretation of the certification process for certain elements of testing. Should this happen, a significant amount of money could be wasted because of a required "do over". These regulations not only apply to RR, P&WA and GE, who are very familiar with certification requirements, but other engine producers that may not be so familiar. The comment was not directed at the Trent 900 certification as you suggested.
Sorry if I confused you...