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JetDriverWannabe
1st May 2003, 05:11
Last time I taken I trip on a B777, I noticed that there is a little fin mounted on the upper inboard side of the B777 engines. Does any one know what this fin is for? I noticed that they are on all B777 Engines regardless of engine make..

Photos of the fin I am talking about is can be found at airlines.net and photo 1 (http://www.airliners.net/open.file/056615/L/) and here. (http://www.airliners.net/open.file/023818/L/)

What does this fin do?

Eckhard
1st May 2003, 05:34
I'm not sure, but the DC-10 has a similar strake on its nacelles, also on the inboard side I think. Maybe it produces a vortex to energise local airflow over the wing, or maybe it reduces the strength of an existing vortex, to reduce drag. The gap between engine nacelles, wing and fuselage can produce unexpected drag increases, in the form of a local 'choke point'.

I wouldn't want you to think that I know what I'm talking about though.......

john_tullamarine
1st May 2003, 06:56
All the larger wing pylon mounted engines, being close to the wing due to nacelle size and ground clearance considerations, shed vortices which cause undesirable flow problems, particularly in the stall regime.

The VG which you a looking at (often referred to as a nacelle chine but a VG, nonetheless) generates a strong vortex at high alpha which reduces the problem of the nacelle shed vortex and reduces the stall speed a few knots.

Have a look at the sticky URL thread - there is a page there which describes the situation very clearly.

regards,

JT

Checkboard
1st May 2003, 07:08
They are known as Chines. The following two TechLog threads refer to them:
Nacelle fins? (http://www.pprune.org/forums/showthread.php?s=&threadid=9228&highlight=chines)
Engine Cowling Fins (http://www.pprune.org/forums/showthread.php?s=&threadid=68329&highlight=chines)

... and you will find information on this pdf (http://www.smartcockpit.com/operations/Vortex%20Generators.PDF) document.

JetDriverWannabe
1st May 2003, 07:12
I can definately confirm that the air flow passing that fin then flows over the top of the wing. On that trip, I saw the contrail form from that fin and then flow over the top of the wing......at least during take off with flaps and slate set to take off settings .