Definition of Severe Damage in CFM 56.

[Tee Emm]

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?

[KBPsen]

A hydraulic pump running dry will eventually overheat and seize up. The pump drive-shaft will then shear, as it is designed to do, and isolate the pump from the gearbox.

If the AGB drive-shaft has sheared then the hydraulic pump is not being driven and neither are the other components which rely on fluids that will be shut off by pulling the fire handle. In this case no components will be damaged.

[Tee Emm]

Thanks KBPsen

Many years ago I experienced a complete loss of System A Hydraulics oil contents in a 737-200 just after lift off when the landing gear hydraulic down line burst.
After landing I recall the engineer had to change both engine driven hydraulic pumps as part of the rectification process. This apparently was because loss of hydraulic oil to the System A engine driven pumps caused damage to something to do with a case drain.. Sorry if I am a bit vague on the terminology but I do remember the poor old engineer worked through the night in the open with winds and pissing rain to change the pumps.

[wrenchbender]

"I do remember the poor old engineer worked through the night in the open with winds and pissing rain to change the pumps."

Probably got paid crap to do it, too.

[Tee Emm]

Probably got paid crap to do it, too.

How right you are. He was a Hong Kong Chinese engineer from HAECO that flew with us everywhere until going back to Hong Kong each fortnight. These blokes were excellent engineers and the airline was fortunate to have their services. We also used engineers from the Australian airline Ansett and again top class blokes. The Aussie engineers were paid much more than the Hong Kong engineers.

[MisterBliss]

Is the payment nowadays still crap?

I remember when I was an engineer I had the highest income because we worked 24/7

For now I became an instructor, less payment, but weekends, evenings and nights off and.... no horizontal rain