To be honest when I first saw the picture I went, cool a pickelhalb... Then came the gun.... However that is
not a Spandau... It's a parabellum. Much cooler machine gun, and very rare. The receiver gives it away, a Spandau has a big strange looking receiver, the parabellum has that nice boxy streamline look.
Spandau machine guns were usually in the front of the plane for forward firing, while the Parabellums were on the carriages on the rear.
Pictures for proof.
The Spandau
The Parabellum