Focke-Achgelis of Germany developed several helicopter and helicopter-type products for its participation in World War 2 (1939-1945). The most notable of the lot became the Fa 223 "Drache" which served in the military helicopter transport role to which some twenty examples were produced. Another creation, the Fa 330, was developed along the lines of "autogyro" and intended for use as a maritime scouting platform for the German Navy. The system was a single-seat aircraft tethered to an accompanying U-boat submarine (serving as its "mothership"), requiring a crew of just two to operate optimally.
By this time in aviation history, the Autogyro concept was a decades-old one, pioneered by Spaniard Juan de la Cierva through various developments of his own during the 1920s and 1930s. The autogyro did not carry a motor to drive its main rotor blades, instead relying on an unpowered rotation of these rotors to generate lift through natural means. Forward flight could be accomplished by installation of an engine coupled to a propeller unit or through simply towing the machine through the air by some other outside means. The key consideration for autogyros was in keeping a constant flow of air running through the rotor blades and thus forcing their rotation. The result was a relatively cheap and simple aircraft with few operational requirements.
The concept was among several considered by the German Navy during World War 2 to expand Over-The-Horizon (OTH) vision, particularly for its submarine force that was largely confined to the surface of the water - scouting accomplished from the conning tower. Traditionally floatplane aircraft served in this role for surface warships but there lay a challenge in housing and operating such aircraft from space-strapped submarines. Hence the idea to pull-behind an unpowered aircraft to achieve better vision OTH was researched - resulting in the Focke-Achgelis Fa 330.
The Fa 330 used a simple metal frame to hold the critical mission components - including the single seat for the pilot, three-bladed rotor mast, vertical tailplanes, landing skids, and simplified control scheme involving a control stick. Beyond this there was no fuselage skinning or engine to contend with, making the Fa 330 an ideal, cheap system for mass production and operational use.
In theory, the Fa 330 - once assembled from its watertight compartments (two would be installed on the deck of the U-boat) - would be released from the deck of the surfaced submarine and towed, via cable line, behind the vessel so lift could be generated for the blades (and then sustained once enough lift was had). The pilot had limited control, but control nonetheless, to maneuver the aircraft about and the major benefit lay in his unfettered vision across the open span of ocean around him, relaying any pertinent information back to the submarine crew. Operating altitudes would reach 120 meters and setup / take-down of the system was around twenty to thirty minutes.
The Fa 330 was fielded operationally on some German U-boats towards the latter stages of the war - mainly in operating areas that were not overrun by patrolling Allied aircraft. The systems were deployed (in very limited numbers) during 1943 but provided limited tactical value in the grand scheme of the conflict - just one enemy ship could be claimed through use of an Fa 330 aircraft and this being a Greek steamship during August of 1943. A captured example fell to the Allies the following year and the design was studied at length. About 200 Fa 330s were constructed and these served from Type IX U-boats.
The prospect of using such towed autogyro systems for submarines became a moot point with the end of the war in 1945 and, from then on, helicopter technology - especially aboard warships - soon overshadowed any benefits inherent in the autogyro-at-sea. As such the concept was allowed to fall by the wayside as more modern battlefield solutions were furthered. In time, the helicopter would become such a key component to at-sea operations and not rivaled in value until the arrival of the Unmanned Aerial Vehicle (UAV). Indeed, many modern warships feature a fixed helicopter flight deck over stern to support the launching and retrieval of rotary-wing aircraft. Newer warships are also supporting these same features for UAVs.
Several Fa 330 systems are on display at various museums around the world including the National Museum of the United States Air Force (Dayton, Ohio) and the Steven F. Udvar-Hazy Center (Chantilly, Virginia).
The Fa 330 was known as the "Bachstelze", or "Wagtail", in German.