Of the many kites and kite-hybrids used during World War II, one of the more novel was the rotary wing kite----the Bachstelze, or Sandpiper---used by the German submarine service. A free-turning three-blade rotor mounted on a vertical pylon attached to a simple framework, the kite was used as an observation post.
The observer’s seat was unprotected. The 24-foot kite was carried aft on a tubular boom and consisted of a rudder and horizontal stabilizing surface. The observer had controls for operating the rudder and for tilting the rotor head.
The kite was connected to the U-boat by cable and winch and maintained height when towed by a surfaced submarine. The observer communicated with the vessel by telephone.