What is the name and purpose of this part on the flap at the DA40? There is a part on DA40's and also DA42's flap. I cannot find the technical document and I couldn't decide what is the purpose of that part. Is it a mass balance part or what? You may see the part at picture. (Note: First picture is not showing the part I meant to ask. The picture was wrong but I keep the picture not to make comments meaningless about it. Correct part is marked at second picture.)


Edit:

Sorry everybody, I drew wrong part before by mistake. The part marked at first picture is the aileron control rod. All previous answers and comments are correct for aileron. I add a new picture for the correct part and I found out it functions as a mass balance horn. We see housings from pictures but the related part is inside the housing.
Edit time: 11th Nov, 2016 10:30 UTC
It is an actuator fairing. It covers the flap actuator so to minimize the drag created by it.

An actuator directly exposed to the airflow would create more drag, increasing fuel consumption and reducing the flight range.