Following is a link to the latest AD note regarding the roll back incident.
Justia Regulation Tracker Airworthiness Directives: Boeing Model 777?200 and ?300 Series Airplanes Equipped with Rolls-Royce Model RB211?TRENT 800 Series Engines , - Federal Aviation Administration - 9565?9568 [E9?4650]
Below is an alternate link if Justia link is not available:
FR Doc E9-4650
Partial content of AD:
Since we issued AD 2008-19-04, we received a report of a single-
engine rollback as a result of ice blocking the fuel oil heat exchanger
(FOHE) on a Model 777 airplane equipped with Rolls-Royce Model RB211-
TRENT 800 series engines. The data confirm that ice accumulates in the
fuel feed system and releases after a high thrust command, creating
blockage at the FOHE and resulting in the inability of the engine to
achieve the commanded thrust. Examination of the data from the rollback
shows that the second of two maximum thrust step climbs was performed
approximately 40 minutes prior to the thrust rollback. Ice was released
within the fuel system during the step climbs and formed a restriction
at the FOHE of the affected engine, as evidenced by an increase in
engine oil temperature. Further analysis of the data shows that ice
accretes in the fuel system more rapidly and at warmer fuel
temperatures than previously indicated, and ice may build up gradually
on the FOHE before causing the engine to rollback. The data from this
event, in combination with Boeing fuel lab testing, demonstrates that
reducing the fuel flow to minimum idle levels will clear any ice
accumulation at the FOHE within a few seconds.
All of the testing and research has been conducted on Boeing Model
777-200 and -300 series airplanes, equipped with Rolls-Royce Model
RB211-TRENT 800 series engines. Initial review of other Model 777
airplane engine combinations has not revealed the same vulnerability to
the identified unsafe condition.