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What Are The MD-80 Fins?  
User currently offlineUpsmd11 From United States of America, joined May 2003, 815 posts, RR: 4
Posted (11 years 4 months 1 week 5 days 16 hours ago) and read 6541 times:
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I have always wondered what the fins are on the fuselage of the MD-80's. A friend of mine who works for DL once told me they were steps so MX could wash the windows but I doubt this as the DC-9's don't have them.

Regards,
John


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User currently offlineBruce From United States of America, joined May 1999, 5057 posts, RR: 15
Reply 1, posted (11 years 4 months 1 week 5 days 15 hours ago) and read 6499 times:

They are called "strakes" and they help improve the aerodynamic stability of the MD80. They have them on the engine nacelles too. Probably need them due to the md80s length and overall design.

bruce



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User currently offlineCdfmxtech From United States of America, joined Jul 2000, 1341 posts, RR: 27
Reply 2, posted (11 years 4 months 1 week 5 days 15 hours ago) and read 6482 times:

friend of mine who works for DL once told me they were steps so MX could wash the windows

I hope this is all your friend advises you about!!!


User currently offlineTechspec From United States of America, joined Sep 2001, 70 posts, RR: 0
Reply 3, posted (11 years 4 months 1 week 5 days 14 hours ago) and read 6474 times:

If my memory is correct. The MD80 strakes were installed to assist airflow across the Vertical Stab and elevators during high angle of attack situations. Prevents what is called "tail" stall. From what I was told in certain flight profiles (nose high) the wings had a tendency to rob airflow from the elevators. So the story goes....
Also, the engines have similar strakes on them also.


User currently offlineFBU 4EVER! From Norway, joined Jan 2001, 998 posts, RR: 7
Reply 4, posted (11 years 4 months 1 week 5 days 9 hours ago) and read 6448 times:

The nose strakes were introduced on the DC-9-50 to improve the directional stability and aerodynamic airflow at high angles of attack and certain flap positions.The DC-9-40 had an internal mechanical solution to this problem,but this was deemed uneccessesary with the arrival of the strakes.On the DC-9-50 and MD-80 series the strakes are anti-iced by bleed air via the airfoil anti-ice switches,on the MD-90 they are electrically heated.
The engine nacelle strakes were introduced on the MD-80 series for another reason,namely stall recovery.They add area which in turn adds drag and in a stall condition,this will help the nose drop faster than the tail.On the MD-90,with it's much heavier engines,there are small "flaps" at the trailing edge of the engine pylons in addition to the nacelle strakes.These operate only in the air and when the control column has reached it's fully forward position.The nacelle strakes are not heated in any way.



"Luck and superstition wins all the time"!
User currently offlineLiamksa From Australia, joined Oct 2001, 308 posts, RR: 0
Reply 5, posted (11 years 4 months 1 week 5 days 9 hours ago) and read 6446 times:

The Beech 1900 has ventral strakes which hang from the T-tail. The increase in side area combined with the relatively long moment arm improve directional stability.

They supposedly also increase rudder effectiveness in a sideslip by providing a vortex.


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Rob.


User currently offlineConcordeBoy From , joined Dec 1969, posts, RR:
Reply 6, posted (11 years 4 months 1 week 5 days 3 hours ago) and read 6408 times:

While we're on this subject... what is the purpose of the small vertical fin?

It's above the "W" in "World" on the DC9 photo in the first post.


User currently offlineFBU 4EVER! From Norway, joined Jan 2001, 998 posts, RR: 7
Reply 7, posted (11 years 4 months 1 week 5 days 3 hours ago) and read 6400 times:

It's the VHF Com. Radio #1 antenna.The one for the #2 Radio is underneath the fuselage.


"Luck and superstition wins all the time"!
User currently offlineCitationJet From United States of America, joined Mar 2003, 2438 posts, RR: 3
Reply 8, posted (11 years 4 months 1 week 5 days 2 hours ago) and read 6389 times:

Since the Beech 1900 is based on the original King Air, Beech did everything they could to avoid designing a new tail for the 1900D.


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