jgore
Posts: 518
Joined: Sun Feb 17, 2002 2:41 am

Why MD-80's Engines Are Facing Upwards?

Fri Mar 26, 2004 1:03 pm

Hey

Could anyone explain the reason MD-80's engines are facing a bit upwards ?
Is that related to its design and/or dynamics ?


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Thanks in advance

Jgore  Smile

 
QantasA332
Posts: 1473
Joined: Sat Dec 13, 2003 5:47 pm

RE: Why MD-80's Engines Are Facing Upwards?

Fri Mar 26, 2004 1:18 pm

This should answer your question. As explained there, MD-80 engines are angled in such a way to align them better with "clean" airstream -- in short, for airflow reasons.

Cheers,
QantasA332
 
DeltaGuy
Posts: 3965
Joined: Wed Sep 12, 2001 5:25 am

RE: Why MD-80's Engines Are Facing Upwards?

Fri Mar 26, 2004 3:22 pm

So I also hear, it's a good thing to help prevent FOD (foreign object damage)...not sure where it came from, so don't quote me  Big grin But the aero charactersitics are more important there...

DeltaGuy
"The cockpit, what is it?" "It's the little room in the front of the plane where the pilot sits, but that's not importan
 
QantasA332
Posts: 1473
Joined: Sat Dec 13, 2003 5:47 pm

RE: Why MD-80's Engines Are Facing Upwards?

Fri Mar 26, 2004 4:55 pm

I'm sure the "engine tilt" helps to reduce FOD to a very -- I repeat, very --limited extent, but, as you said, airflow orientation is the major consideration involved.

Cheers,
QantasA332
 
CFIcraigAPA
Posts: 223
Joined: Mon Jan 12, 2004 10:20 pm

RE: Why MD-80's Engines Are Facing Upwards?

Fri Mar 26, 2004 8:53 pm

This should help too. It's not just for airflow reasons, look for my reply about four or five down.
CM
Prior Proper Preparation Prevents Piss-Poor Performance
 
vikkyvik
Posts: 11755
Joined: Thu Jul 31, 2003 1:58 pm

RE: Why MD-80's Engines Are Facing Upwards?

Fri Mar 26, 2004 10:13 pm

Jgore,
The inlets are slanted upwards in order to alighn the intakes with the local airflow, as it has been disturbed by the wings and fuselage.

CFIcraigAPA,
In the reply in the linked thread, you stated that the horiz. stab. gives a nose-down moment, which is not correct. The H-stab gives a nose-up moment; it's an inverted airfoil, meaning it's generating lift downwards, which would obviously cause the tail end to lower and the nose to raise.
Also, adding power will cause a nose-up moment as well. The whole reason the H-stab is in existence is because the center of lift is ahead of the CG, therefore, causing a nose-up moment. Adding power will increase the aircraft speed, therefore increasing the lift. As far as as I know, this will counteract the very slight nose-down moment created by the engines increasing their thrust.
Someone correct me if I'm wrong.
~Vik
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
darkblue
Posts: 227
Joined: Thu Sep 11, 2003 10:27 pm

RE: Why MD-80's Engines Are Facing Upwards?

Sat Mar 27, 2004 1:41 am

This topic has been discussed before, you may want to do a search.

Note that it is the inlets of the engines that are facing up, not the actual engine. Aft-mounted engines are in the downwash of the wing so the inlets usually face upward to be aligned with the flow. Wing mounted engines are in the upwash of the wing and the inlets usually face downward to be aligned with the flow.

DB

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