A320 Black Triangle
 

Could someone shed some light as to what this black triangle is for. Thank you.

http://postimg.org/image/519hanxl7/

It is the best location to have a visual check of the position of the flaps or slats. It can be done through the windows in the fuselage that are adjacent to the LE and TE. The windows to be used are identified by a brown/black triangle

Learn something everyday. Thank you.

Aviation is an everyday learning job...

it points to meca

I used to work with a bloke who used to claimed that, "that little black triangle will draw you further than gunpowder can blow you".
I thing that he meant another black triangle.

Icing
 

I understood to be the best view of the LE, to check for ice build up.. and have seen it used for such. I know it as 'The William Shatner" seat Nightmare at 20,000 Feet - Wikipedia, the free encyclopedia

I was told it was to identify the location of the emergency lights' batteries.

Tango Romeo A320 is correct.

The triangles on related cabin sidewall panels identify the windows
through which the cabin crew can observe the external S/F position
markings in A300/A310.

This to prevent parallax errors if observed from a different window.


For FBW Airbii there is no necessity to visual check the S/F position
- i.e. no procedure - because there is reliable electronic indication. (IPPU)

However the triangles (and S/F markings) are kept for traditional reasons
(crews originating from non FWB Airbii) only.