A320 Wing root fairings
 

Some A320s have protrusions on the leading edge of the wing root fairing while others have a leading edge that blends smoothly into the fuselage.

Anyone know why?

I'd put up some pis but I don't have the permission to do so.

I have not seen any without.

A notch or sawtooth in the LE generates a vortex which helps control the boundary layer and delay separation. I imagine it helps reduce interference drag betw wing and fuse.

Wing root fillet seal.

Does have fuel penalties if missing as per CDL.

interesting

any pics?

I just had a friend send me some good info regarding my question:

I don't think the company modified the older fleet, they just came that way. I was told by one of our Check Airmen that the newer design leading edge cuff is a vortex generator that delays airflow separation along the wing/fuselage juncture. Airflow separation means drag, so it is a drag reduction device, which means they must have discovered something in the way of an easy fix to reduce drag. My dad used to always say that the intersection of the wing and fuselage was one of the most difficult areas to design. If you get it wrong, the drag penalty can be huge for long range type aircraft. My dad was a aerodynamic flight controls design specialist on the XB-70 and the B1 among others - two long range aircraft that were designed before computer aided design was available. Amazing what those guys could do with a slide-rule.

Pics
 

http://db.tt/MmLLn7c

http://db.tt/vXKtYrj

Absolutely correct - and I speak from personal experience of the A320 wing design. About 1% drag reduction if memory serves.

Cheers CliveL. Was a surmisation on my part as why they put it there. Installed further out, I understand it helps against the negatives of tip stalling on a swept wing

Old ones don't have it
new ones have it
right

so it is good, although uglier...