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MD11 Question

Sat Oct 30, 2004 12:19 pm

How is the #2 engine mounted and supported? Is it an "upside down" pylon on the bottom of the engine? How similar (or not) is the pylon compared to the pylons for the #1 and #3 engines? Is it even called a pylon?
Answers appreciated;

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RE: MD11 Question

Sat Oct 30, 2004 12:56 pm


Great questions! The pylon (yes it is called a pylon) is above the engine and the engine hangs from it. The pylon mount is identical to 1 and 3 in that the engine attach points are the same. This is so any spare engine can be mounted at any location. I'm not sure but the pylon is probably fitted to the airframe differently.

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RE: MD11 Question

Sat Oct 30, 2004 10:14 pm

what was the rationale for the tail engine in the first place, and why was it abandoned ??
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RE: MD11 Question

Sun Oct 31, 2004 9:18 am

As DI757MD stated, #2 engine is hanging from a pylon attached to the rear spar of the vertical stabilizer. The whole structure is a bit complicated to explain, but basically you have 4 socalled banjo fittings, huge titanium forgings, looking like a ring with an attachment on top and on the bottom. The bottom attachment is connected to the rear fuselage, while the top attachments connect to the four spars of the vertical stabilizer.
The hole inside the rings is the inlet tunnel of #2 engine.
The fan case of #2 engine is bolted to a unit called a bell mouth, wich has a sliding connection with the inlet tunnel (so that the engine can vibrate and move without disturbing the structure of the inlet).
The engine mounts and accessories of #2 engine are slightly different from the other two engines. Additional to the two mount plates on top, which transmit the engine weight and thrust to the airframe, there is another diagonal brace at the bottom connecting the engine fan case with the lower attachment of the last banjo fitting to carry the torque forces of the engine and to transmit them to the airframe. Also, on the CF-6 engine, the hydraulic pump supply line comes from the bottom instead of from the top.
#2 engine also has a remote manual start valve mechanism with a push pull cable leading to a handle in the tail cone compartment. Additionally, there are remote service lines for both the engine oil tank and the IDG plus a remote IDG filter differential popout indicator, also located in the tail cone. You can´t just install a wing engine in the #2 position, you´ll have to modify it slightly before.

The reason for the DC-10 / MD-11 #2 engine layout was that they wanted to have a straight inlet to give the engine full performance, unlike the 727 or the L1011, where the s-duct restricts the performance of #2 engine.

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RE: MD11 Question

Sun Oct 31, 2004 9:25 am

what was the rationale for the tail engine in the first place, and why was it abandoned ??

The three major manufacturers took 3 different approaches. Boeing went with two huge engines, McDD went with 3 engines of 744 size, and Airbus went with 4 much smaller and easier to maintain engines.

The structure necessary to support the tail mount is very heavy, and maintaining an engine several stories off the ground is challenging even on good days.

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RE: MD11 Question

Sun Oct 31, 2004 12:44 pm

Gigneil, Airbus with 4 engines in the tail?

I only know of the Vickers VC-10 and the Lockheed Jetstar with that layout...

Edit: the IL62 too... Big grin

[Edited 2004-10-31 04:55:46]
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