Having a particularly low superstructure, a submarine has an extremely limited horizon. This is one of the chief limitations of the type, since a U-boat can’t sink what it can’t see. An observation aircraft was an obvious solution. Co-operation with shore-based aircraft was useful but was constantly hampered by Goring’s intransigence. Out of the range of land, and beyond the political haggling of the Third Reich, the Naval Staff conceived of the need for a U-boat-carried observation aircraft. The idea itself was not new, experiments going on with the Hansa-Brandenburg W20 in 1918. Most naval powers toyed with the idea of at one time or other, particularly the Japanese. Now with the U-Kreuzer of the type XI Class on the drawing boards in 1938, the Arado Flugzeugwerke was given a contract to develop an U-bootsauge (U-boat’s eye). The result of this was the development of the Arado Ar 231. Powered by a lightweight Hirth engine, the little parasol wing float-plane had an endurance of about four hours. The wing center section was angled so that one wing could be stowed above the other when folded back. A set-up and break-down time of six minutes was achieved with the proto-types that were built. First flying in 1941, it proved to have poor airborne and seaborne characteristics. Further, it proved impossible to takeoff in any but the lightest seas. Not too surprisingly, when Donitz was able to cancel the type XI project, the Ar 231 was dropped by the RLM. In the meanwhile, another much more novel solution to the problem had been raised. Heinrich Focke, one of the founders of the Focke-Wulf Flugzeugwerke, had been designing autogyros and helicopters since 1932 with some success. Among the designs that had reached production status was the Focke-Achgelis Fa 330 Bachstelze (Wagtail) rotor kite. With the failure of the Ar 231, a search was made for a craft that could be used with existing U-boats. The Fa 330 seemed to be exactly what was needed. “Flying” on its tether, this Fa 330 Bachstelze trails behind a type IX boat in the Indian Ocean. It was only in those waters that the relative scarcity of targets and escorts made its use more necessary and more safe. Note the number of crew left on deck in case the kite had to be hauled in. Basically an unpowered autogyro, the Bachstelze operated on the same principals, differing only in that it needed to be towed to stay aloft. The structure was simplicity itself, being nothing more than a vertical pole with a three-bladed rotor at the top and a horizontal pole with landing skids underneath, a seat at the front and fabric-covered control surfaces at the rear. The 18 kt. surface speed of a type IX was sufficient to keep it airborne, being towed by a 150m cable that included a telephone line. Only seven minutes were required from surfacing of the U-boat for assembly and attainment of 120m altitude. Recovery proved to be a much slower operation, the tow cable being gradually winched in as the pilot tried to lose altitude. If surprised by an enemy escort ship, the U-boat commander was confronted with the unhappy choice of abandoning the Fa 330 and pilot, which couldn’t stay aloft waiting for the boat to surface later, or attempting the dangerously slow recovery process. For this reason, the Fa 330 was unpopular with the U-boats and, even though 200 were built, only a few were used and only in the Indian Ocean where the relative scarcity of both targets and anti-submarine escorts made its use both more helpful and more safe. On at least two occasions, Fa 330s were swapped for the E14Y1 Glen collapsible float planes carried by Japanese I-boats, during encounters in the Indian Ocean. Some of the unfortunate history of Kriegsmarine - Luftwaffe co-operation is told elsewhere, but there was one area where the two forces worked well together. Operating mainly out of Tromso, Norway, SAGr 130 flying BV138C seaplanes provided excellent reconnaissance of the Murmansk convoy route until the appearance of escort carriers in September 1942, made this too dangerous. As late as August 1943, though, co-operation continued between these planes and the U-boats of the 11.U-bootsflottille. The BV138s were able to double their search range by rendezvousing with the arctic boats, mainly in the protected waters off Spitsbergen, and refuelling for the return sweep. In the most dramatic example of this teamwork during late summer 1943, two U-boats set up a forward base for the seaplanes on the island of Novaya Zemlya, off Russia’s Siberian Coast, allowing them to reconnoitre deep into the Kara Sea in search of convoy activity.