29 September 2015

The Cheapest Aircraft of the Second World War: The Focke-Achgelis Fa 330

Poor quality video of the Fa 330 operating from a U-boat (YouTube)

Earlier this month I had written about the aircraft types that were operated off submarines in the First World War, albeit on a very limited operational basis, and some designs that never quite made it to sea. In the interwar period, there were several experiments and attempts at aircraft operations from submarines- some of which will be future topics here at Tails Through Time- but none ever really evolved into a useful operational system. As is often the case in wartime, the pressures and operational needs of combat sometimes rekindle old ideas and this certainly the case for the German Kriegsmarine's Ubootwaffe (U-boat arm) in the Second World War. The initial plans were for a light seaplane from the Arado Flugzeug Werke designated Ar 231. Arado had built observation floatplanes for the larger surface combatants of the Kriegsmarine and in 1940, they were issued a contract for six "U-Bootsaugen" or "submarine eyes". The Ar 231 was the result and it was a single seat high wing monoplane with a 160 hp six-cylinder engine. The wings folded back over the fuselage and the entire aircraft could fit into a container only six feet in diameter. However, sea trials showed the little floatplane couldn't take off in winds greater than 20 knots and much like the problems faced in 1917, only the calmest of sea states was needed for safe flight operations- this was an unrealistic expectation for the planned operational arena for the U-boats, in the harsh North Atlantic interdicting convoys bound for Great Britain from the United States. The idea for the "U-Bootsaugen" was quietly canceled with the Ar 231 fading into the footnotes of aviation history. However, following the entry of Japan into the Second World War after its attack on Pearl Harbor, the directive came down for the Kriegsmarine to find a way to join forces with the Imperial Japanese Navy. In the same year that IJN submarines began operating in the Indian Ocean interdicting British shipping, the idea was passed to the Kriegsmarine in December 1942 to base U-boats in Japanese occupied Malaya and the East Indies. A new U-boat variant based on the large ocean going Type IX submarine, the Type IXD2, was on the drawing boards at that time as an ideal submarine for what the Kriegsmarine called the "Monsun Gruppe" which were U-boats based at Penang in Malaya. 

The Fa 330 at the RAF Museum in Cosford (Wikipedia)
On the broad and calmer Indian Ocean (at least on the trade routes from Africa to Australia), the Kriegsmarine once again issued a limited requirement for some means to extend the visual range of a surfaced U-boat for targets of opportunity on the cruises around the Cape of Good Hope to Penang and back. Simplicity and ease of use were paramount, mindful of past pitfalls with operating aircraft from submarines had shown. The unique demands were met by one of the most unique aircraft of the Second World War, if not the simplest and cheapest, the Focke-Achgelis Fa 330. Heinrich Focke had founded Focke-Wulf in 1923. In the 1930s, Focke-Wulf had license built Juan de la Cierva's autogyro designs and from that experience, Heinrich Focke designed the Fw 61 helicopter. However, in 1936, he was ousted from Focke-Wulf. Several references indicate it was because he was considered politically unreliable the the Nazi regime, but in all likelihood it was to get him out of the way so that Focke-Wulf's production capacity could be used to build more Bf 109 fighters from his rival, Willy Messerschmitt. Despite this, the German Air Ministry was impressed with the Fw 61 which the German pilot Hanna Reisch had ably demonstrated by flying the helicopter indoors. They encouraged Focke to start a new company devoted to the development of his true interest, vertical flight. He teamed up with his helicopter test pilot, Gerd Achgelis (he flew the Fw 61 on its maiden flight in 1936) to start Focke-Achgelis and it was this outfit that created the Fa 330 to meet the Kriegsmarine requirement for an observation aircraft of utmost simplicity for use by the submarines of the Monsun Gruppe

Lacking its own power plant, the Fa 330 was really a gyro kite. It had a three-bladed 24-foot rotor and when fully assembled, the Fa 330 weighed only 180 lbs. The main body was essentially an upright welded steel tube to which the rotor was attached at the top. A longitudinal tube of smaller diameter was attached to the bottom to which the single seat, controls, tail surfaces and outrigger skids were attached. Each of the major components attached together with simple spring loaded pins which also made for easy disassembly. Two vertically-oriented containers attached to the conning tower housed the parts. With each rotor blade 12 feet long, that dictated the maximum depth of each storage compartment. Four men could assemble the Fa 330 in only 3 minutes in a reasonable sea state. A platform sat on the aft part of the conning tower where the Fa 330 was launched and recovered. With the pilot/observer ready, the U-boat would turn into the wind as 20 mph was needed to get the Fa 330 gyro kite airborne as the pilot used his controls to tilt the rotor head back to "catch the wind" like a kite with a steel cable which also carried a telephone line to allow the pilot/observer to communicate with the submarine's bridge. The operating speed was usually about 25 mph but the Fa 330 could stay airborne with as little as 17 mph of forward speed by the U-boat. Typical operating altitudes were between 200 to 500 feet, though in calm weather, the Fa 330 could be flown up to 1000 feet. In good visibility, this extended the U-boat's visual horizon out from the usual 12 miles to 50 miles. At an altitude of 600 feet, the visual horizon was 31 miles. Even at minimum operating speed, the Fa 330 could fly 200 feet up and that still gave the U-boat captain a visual horizon of about 20 miles. The Fa 330 was recovered by simply winding the cable back in until the Fa 330 could alight on the conning tower platform. Though Focke-Achgelis designed the Fa 330, it was built by another company, the Weser Flugzeugbau.

Model kit box art showing an Fa 330 being deployed by a U-boat (Mirage Hobby)
Pilot/observers were trained to fly powered gyrocopters at the French Aeronautical Experimental Establishment outside of Paris. Training on the Fa 330 itself was carried out inside a large wind tunnel with more advanced training taking place with the Fa 330 being towed by trucks on a runway before moving to being towed to higher altitudes by a gyrocopter. A proposal was floated to put a 60 hp engine on the Fa 330, but it never advanced far with the Kriegsmarine. About 200 Fa 330s were built. At sea, the pilot/observer was in an unenviable position should he have spotted a warship as that would have meant an immediate crash dive by the U-boat. If this were to happen, the pilot was to activate his escape mechanism which severed the rotor blades get them away from the pilot who then dropped away from what was left of the Fa 330, his parachute ripcord being pulled automatically by the departing blades as they fell away. That left the pilot to float down to the ocean and hope to be picked up when the submarine resurfaced. It's not known what happened to most Fa 330 pilot/observers, though Royal Navy patrols in the Indian Ocean did come across floating parts from the Fa 330. 

Only the U-boats with Monsun Gruppe in the Indian Ocean used the Fa 330 as the Allied air threat in the Atlantic was too great. Only one sinking is known to be attributed to Fa 330 operations when U-177 used its gyro kite to assist with the interception and sinking of the Greek steamer Ethalia Mari on 6 August 1943. Details of the use of the Fa 330 operationally are scant on account of so few U-boats surviving the war. Several U-boat captains, however, believed using the Fa 330 was too risky which may have ultimately prevented its more widespread use. The Allies found out about the Fa 330 after studying the submarine U-852 after it had run aground on the coast of Somalia after an air attack. While not impressed with its capabilities, they were suitably impressed with its simplicity and ease of use. 
The L-3 Valkyrie Virtual Mast unmanned gyro kite (Popular Science)
Interestingly in 2013, the defense company L-3 proposed a re-imagination of the Fa 330 concept with their Valkyrie "Virtual Mast" in which a carbon fiber gyro kite would carry aloft an electro-optical/IR sensor as high as 5000 feet on a steel cable for ships at sea. 

Sources: Strike From Beneath the Sea: A History of Aircraft-Carrying Submarines by Terry C. Treadwell. The History Press, 2009, pp 103-109. The Smithsonian National Air & Space Museum.

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