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Why MD-80's Engines Are Facing Upwards?  
User currently offlineJgore From Argentina, joined Feb 2002, 550 posts, RR: 2
Posted (10 years 9 months 13 hours ago) and read 6244 times:

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



6 replies: All unread, jump to last
 
User currently offlineQantasA332 From Australia, joined Dec 2003, 1500 posts, RR: 25
Reply 1, posted (10 years 9 months 13 hours ago) and read 6212 times:

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


User currently offlineDeltaGuy From , joined Dec 1969, posts, RR:
Reply 2, posted (10 years 9 months 11 hours ago) and read 6060 times:

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


User currently offlineQantasA332 From Australia, joined Dec 2003, 1500 posts, RR: 25
Reply 3, posted (10 years 9 months 9 hours ago) and read 5963 times:

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


User currently offlineCFIcraigAPA From United States of America, joined Jan 2004, 223 posts, RR: 4
Reply 4, posted (10 years 9 months 5 hours ago) and read 5892 times:

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
User currently offlineVikkyvik From United States of America, joined Jul 2003, 10335 posts, RR: 26
Reply 5, posted (10 years 9 months 4 hours ago) and read 5863 times:

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



How can I be an admiral without my cap??!
User currently offlineDarkblue From United States of America, joined Sep 2003, 233 posts, RR: 10
Reply 6, posted (10 years 9 months ago) and read 5827 times:

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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