Four Wings

Four Wings (四枚羽) is the name given by Thor to refer to the unmanned attack helicopters that are derived from the HsAFH-11 "Six Wings" helicopter, or more accurately, a.

Principles
It is a state-of-the-art weapon manufactured by Academy City. According to Thor they are low cost versions of the Six Wings, but has apparently reduced its bulkiness to make it more maneuverable. It can be assumed that since Six Wings looks like a AH-64 Apache, the Four Wings would likely look like a much more slimmer version of it.

It is apparently an anti-personnel attack helicopter. It uses sonic weapons to stop any human resistance and then use machine guns and missiles to finish them off. Other specifications are unknown, but it most likely uses AI to check its surroundings like the original, and the rotors on the wings of the aircraft split into two.

Ichihanaran Festival Arc
A few Four Wings aircrafts are dispatched after Kamijou Touma and Thor are detected at the Windowless Building, forcing them to decide whether or not to abandon their cause, though, Thor states that there would be no more second chances in rescuing Fräulein Kreutune if they choose to retreat.

After Fräulein escapes from the Windowless Building, she makes quick work of the Four Wings.