Dear Oluf,
OK, can you explain, why the FAA issued an AD on the 23. jan. 2008, only six days after BA38s "grass-landing" in order to:
"Prevent internal engine damage due to ice accumulation and shedding, which could cause a shutdown of both engines, and result in a forced landing of the airplane"
After reading the AD, i think you are taking this passage out of context.
The statement in your post is incomplete. It is preceded by, i quote:
"This AD results from reports of engine surges and internal engine damage due to ice accumulation during extended idle thrust operation in ground fog icing conditions. We are issuing this AD to prevent internal engine damage . etc. . ."
Shutdown of both engines in this case could occur during or immediately after take-off, resulting in a forced landing. If there would be a relationship to the BA38 "grass landing" i would have expected the AD to have included prolonged CDAs in icing conditions also. Since the AD does not, i read this AD as valid in ground fog icing conditions only.
Also, there is a difference between ground idle (minimum idle) and approach idle. Approach idle is automatically selected in flight, resulting in a higher engine thrust setting when engine anti ice is on or when landing flaps are selected. For the RR Trent the EECs use EPR as primary thrust setting parameter. If core icing would have been a factor i would assume EPR would have started to deviate from normal settings in relation to the other primary engine indications, N1 and EGT. If not noticed by the crew, i think they would have noticed if this were the case, this would have certainly shown up in the DFDR and QAR parameters. No mention about such deviations is made in the AAIB reports.
Regards,
Green-dot