Definition of Severe Damage in CFM 56.
With the CM56 series engines, if an engine failure occurs accompanied by strong airframe vibration the QRH states the engine must be shut down and the engine fire switch pulled. If a fire warning occurs the extinguisher must be used.
One of the signs of an engine seizure is severe vibration and the N2 indications goes to zero.
On the other hand if the auxilliary drive shaft fails the N2 will also go to zero and the engine flames out with no vibration.
My question is this: Does the failure of the auxilliary drive shaft constitute "Severe Damage"? If the drive shaft does fail for some reason and the fire switch is pulled as part of the engine shut-down checks (rightly or wrongly) what damage may occur to the engine driven hydraulic pump on that engine since the hydraulic fluid shut-off valve is closed. As hydraulic fluid is used for cooling and lubrication, does this mean the engine driven pump needs to be changed following operation of the fire switch?