.......From a note from SFO MOC Engineering: 2372 came in and the fire department trucks were giving the final salute. The truck on the right side sprayed fire extinguishing agent (foam) rather than water. IAD wanted to clean it and go. SAMC called the MOC who put a stop on that action. Foam
is very corrosive on hot titanium parts (primarily in the HPC section
of the gaspath. SFOEP had the engines borescoped and both showed evidence
of foam ingestion (both engines were running at idle when this occurred).
The airplane is OTS in IAD and the engines will be removed. The MOC
doesn't have any spare 777 engines so they are using previously removed
engines as mules to fly the airplane from IAD to SFO for storage until
they can produce more engines. The airplane will be OTS for the near
future - just before the major holiday traffic period!
Generally speaking almost all the fire extinguishing agents are corrosive
on hot engine parts so if that happens it is an engine removal. However,
P&W has never tested this particular foam so the MOC is getting a sample
of the foam for P&W to test.