Gents ,
Regardless of all the whys and wherefores, the engineer that signs off your a/c requires authority to do so , or the CAA or other regulatory authorities take a rather dim view of things . Unless the engine OEM's relent , there is a huge amount of pain in the future for operators .
Here is an extract from an OEM's All operator Wire :
The following actions are recommended for engines that have been exposed but have been parked (not
operated on the ground or in-flight) in a volcanic ash environment prior to the next engine start:
A. Remove volcanic ash from the area in front of engine inlet and around the exhaust.
B. Dry motor the engine at maximum motoring speed for 90 seconds to blow volcanic ash out of the
engine.
C. Borescope inspect the HPC and HPT at the 6:00 o’clock position to look for foreign material. If loose
material is observed, dry motor the engine again for 90 seconds and re-inspect.
D. Change the engine oil filters.
E. Drain the oil system and refill with fresh oil.
The following actions are recommended for engines that have been exposed to volcanic ash and operated
(on the ground or in-flight) in a volcanic ash environment prior to the next engine start.
The following actions are recommended for engines that have operated (on the ground or in-flight) in a
volcanic ash environment (or if exposure is suspected or unknown) prior to the next engine start.
A. Inspect the engine inlet and exhaust areas for damage or erosion
B. Borescope inspect the Booster, HPC, combustor, HPT, and LPT for evidence of erosion, foreign object
damage, ash deposits, and cooling hole plugging.
C. Change engine oil filters.
D. Drain oil system and refill with fresh oil.
E. Schedule a repeat HPT borescope inspection at the next aircraft A check or within 400-800 hours.
F. Perform a ground power assurance run.
G. Continue to use the engine and vigilantly review the engine trend monitoring data to look for
possible negative engine performance.
paths resulting in reduced cooling flow and can also cause rotor imbalance from accumulation of material
settling and drying in the rotor spools.
Engine operation in volcanic ash environment should be avoided if possible. In-flight procedures are
provided in the Aircraft Manufacturers’ Operating Instructions.
The manual states "Before next engine start"