View Full Version : MD11 CF6 N2 Vibs limits check list

Carbon Fibre
20th Jan 2010, 06:12
Hi everyone, sorry I am an engineer.

Just wondering if someone could provide me with the N2 Vibration limits for the CF6 powerplant for the MD11 by way of the checklist (and attach a copy if possible) neccesary for an exceedance or approaching exceedance levels. Also to my engineering colleagues a copy of the vibration limits in the maintenance manual ( and attach a copy if possible).

Please be garuanteed that no one is going to get into trouble I am just having issues with the engine shop!


Carbon Fibre

20th Jan 2010, 14:22
Be aware that engine vibration, its causes and its results are quite subjective in nature. If it turns into an argument then many other details (symptoms etc.) need be brought into the discussion.

Carbon Fibre
22nd Jan 2010, 06:16
Actually, lomapaseo is a very experienced professional engineer and one from whom you could learn more than a few things if you were to pay attention ...

Either way, we try to discourage overt rudeness in posts. JT

Castle Don
23rd Jan 2010, 14:26
Carbon Fibre,

Pretty sure there is no specific cockpit checklist for high vib. It is referenced in the Compressor Stall procedure only as a supporting indication.

PS. I am not current on MD11. Never been current on PS3

24th Jan 2010, 17:02
I can check the limits at a later time, but I am pretty sure that excessive vibe prompts a secondary engine page "que light" and displays in amber.

Don't believe the pilots have a checklist with limitations, limits may be in the fcom with procedures. Usually a significant vibe is felt through the airframe as a primary indicator.

Will try to get back to topic when I can quote facts.

We Fix Them
9th Feb 2010, 22:08
Hello !

Never worked this aircraft before but a mate of mine in the UK sent me this from the AMM 71-00-00-2 for the CF6-80C2D1F. Maybe this is what you were looking for ?

High vibration - Emergency Engine Shutdown. Before you change the throttle position, monitor on the primary and the secondary engine pages the indications that follow. Make a record of these indications to make an analysis of the problem. - EVM indication - N1 - N2 - EGT indication - Fuel flow - Oil pressure - Oil temperature - Oil quantity - All engine alerts that are shown.

2) Move the throttle lever forward or aft until the engine vibration decreases below 4.0 units. The ENG X VIB HI alert on the display screens must go off when the vibration decreases below 4.0 units.

3) If the EVM indication goes below 4.0 units and the ENG X VIB HI alert goes off, continue to operate the engine. Do not operate the engine at throttle positions, or in wind conditions that will increase engine vibration.

4) If all other engine parameter indications are correct, you can continue to operate the engine when the EVM indication is 4.0 or lower (and ENG X VIB HI alert is on). Continue to monitor the engine parameters for unusual indications.

5) Shutdown the engine if the EVM indication stays above 4.0 (ENG X VIB HI alert on). The unusual engine indications that follow are shown: High EGT, High oil pressure, Large N1 fluctuation, Large N2 fluctuation, Oil pressure fluctuation and Compressor stalls.

10th Feb 2010, 18:23
Not sure about the MD-11 - but I can quote some earlier types. My observation is that vib indicators ARE NOT MEL items - the a/c is serviceable without them. In that case, the airframe itself serves as your vib instrumentation.