The Battle of the Atlantic was one of the great campaigns of the Second World War. Waged from 1939 and finally ending with the surrender of Nazi Germany in 1945, it is also considered the longest.
Although it featured heavy use of both sea-and-air power by both sides, the predominant feature of the campaign was the pitting of the German submarine service against the strength of the Allies surface and mercantile fleets.
Today, there is a vigorous historical debate as to how close the German submarines – colloquially known as U-Boats – actually came to causing the economic and physical collapse of Britain through their sinking of ships carrying critical war supplies.
But I think we can gain some insight into the significance of this battle from what Winston Churchill wrote of the ordeal after the war:
‘The only thing that ever really frightened me during the war was the U-boat peril.’
If Winnie was willing to admit that, I think we can agree it must have been pretty serious.
And certainly, both sides invested lavishly in new technology to help their respective combatants in what was the most drawn-out battle of attrition of the entire war. Radar, sonar, weapon systems and the various vessels that used them; all leaped forward tremendously in capability as money and effort were lavished upon them.
But there were, amongst the amazing technical breakthroughs, some that seem downright odd – or possibly brilliant. And one of those was the Focke-Achgelis Fa 330.
Which might look like a helicopter but was in fact…a kite!
But the similarity to a helicopter is no surprise as it was designed by Heinrich Focke – one of the great pioneers of the helicopter. In 1936 Focke was pushed out of his company, Focke-Wulf (yes, those guys), and found himself suddenly at a loose end.
However, his genius for designing and building rotor aircraft was appreciated by the German Air Ministry, and he was encouraged to start a new company to explore that field. This he did, founding Focke-Achgelis in 1937.
This company would develop several different models of helicopter and Focke, along with fellow helicopter pioneer, Anton Flettner, would make Nazi Germany the most advanced nation in terms of rotor technology at the start of the war.
The German Navy was an early appreciator of the potential, recognising that autogyros and helicopters could be extremely useful for naval reconnaissance and anti-submarine work.
The coastal waters around the UK and the United States, once productive hunting grounds, were now infested with patrol aircraft.
Allied advancements in radar and tactics also meant that these shallow seas were becoming increasingly lethal, pushing the U-Boats out into the mid-Atlantic where Allied air cover, at that point at least, couldn’t reach.
But this gave the U-Boats other problems. Operating in this area generally meant running on the surface in heavy swell to try to locate targets to attack. U-Boats were built low to the water to minimise their profile while running on the surface.
The problem with this was it meant they couldn’t see very far – sometimes as little as only six miles.
They also had much larger areas they needed to patrol. After all, operating close to the ports, they could be reasonably sure of running across Allied shipping. But in the middle of the Atlantic, the Allied convoys had a vast area of ocean to lose themselves in.
The U-Boats were looking for the proverbial needles in a haystack. What they needed was to improve their search radius – in other words an aerial scout.
And so, Focke was asked to come up with an aircraft capable of operating off a U-Boat that would boost scouting range but which needed to be small, mechanically simple to maintain and operate and easy to store.
His answer was, in my opinion, brilliantly elegant.
The Fa 330.
A rotor kite.
This aircraft had no power plant itself, instead relying on the motion of a towing vehicle – i.e. a U-Boat – to provide the energy to turn the blades and thus propel it into the air. As can be imagined, this keeps things extremely simple.
Weighing only 68kgs, or 150lb, the Fa 330 was constructed of simple steel tubing with a three-blade rotor atop the vehicle. Controls were a stick for pitch and roll control, and foot pedals to move the rudder to control yaw. Instrumentation was simply an altimeter, airspeed indicator, and tachometer.
The rotor blades were made of a 3.2 m (10 ft 4 in) steel spar with plywood ribs, skinned with fabric-covered plywood.
Operation was extremely simple. The machine was stored in two metal containers on the U-boats deck. In a calm sea four crewmen could assemble the Fa 330 in three minutes. This would take place on a small platform added to the rear railings of the conning tower, which also had the towing winch fitted.
Once assembled and the pilot strapped in, take-off would be accomplished generally by a deckhand spinning up the rotors by vigorously hauling on a rope wrapped around a drum on the rotor hub.
A minimum towing speed of 17mph was required for the rotors to achieve and maintain enough rotation for lift.
The Fa 330 was attached to an electric winch that paid out the line. The amount that could be let out, and consequently the Fa 330s altitude, depended on the airspeed. This was a combination of both the towing sub’s speed and the windspeed blowing into the face of the craft.
The maximum safe airspeed was 50 mph (80 kph), and with that the Fa 330 could reach a height of 220 meters (722 ft). At that altitude, the pilot could spot a ship 33 miles (53 km) away in clear conditions.
However, If the airspeed was lowered then the amount of line that the Fa 330 could sustain dropped accordingly. The minimum safe airspeed was 22mph (35 kph), and at that the maximum altitude possible was only 100 m (330 ft), with spotting distance reduced to 22 miles or 35km.
The tow cable had an intercom wire wrapped around it, and through this the pilot could report any sightings to the crew below.
Obviously, with no fuel requirement the only limiting factor on how long the Fa 330 could stay aloft was pilot fatigue, weather conditions and enemy action, and in optimal conditions the aircraft could be pulled down, disassembled and stored in four minutes.
The Kreigsmarine cleared the Fa 330 for operational deployment at the beginning of 1943, at which point only the big Type IX oceanic U-boats, which had a top surfaced speed of 18 knots (roughly 21 mph /33kph), could tow the little craft fast enough for flight in low wind conditions.
By this point the Allies grip on the Atlantic was tightening. Although the fight was still very much in the balance, it seems that it was recognised that the complexities of operating the Fa 330 in the rough North Atlantic, combined with the heavy presence of escorts and aircraft now using radar as standard, meant that utilising the little rotor kite in that theatre was not viable.
Instead, the only records of any use by German U-Boats seems to be on submarines deployed further afield, possibly in the South Atlantic and Pacific but certainly in the Indian Ocean.
In fact, how much these aircraft were used is basically unknown.
This is due to the fact that most U-Boats were ultimately lost in the war, along with their crews and logs, and so we just don’t know if they were used very much at all. In fact, only one known action involved an Fa, when U-177 sank a cargo ship off Madagascar in August 1943.
It is likely more did occur but as stated, the records went down with their various ships.
It also seems that the Fa 330 might not have been popular with U-boat captains, who feared being attacked while deploying the aircraft and thus being vulnerable. This was a real concern, and U-boats were liable to sudden attack at any moment in any area by Allied airpower – a situation which would only get worse as the war continued.
Should the U-boat come under attack and need to ‘crash’ dive while flying its Fa 330, the procedure was as follows.
The pilot pulled a large red lever above his seat. This disconnected the towline and the rotor from the aircraft. The submarine could now dive to safety, while the departing rotors pulled a cable that deployed the pilot’s parachute. When this opened, the pilot popped his seat harness and the remainder of the gyrocopter fell into the sea.
The idea was that after the submarine evaded the danger, it could then recover the pilot.
If the threat was more distant, the pilot could also just release the towline, which would then allow the whole aircraft to slowly drop down to the surface on its own. He could then ditch close to the sub and be picked up before diving or, if the pilot was particularly good or else conditions just right, land on the sub itself.
But it seems these options were not often exercised, at least not enough to have gone on records that survived, and the Fa 330, despite being a rather ingenious idea, never really achieved much.
Despite this, they were of some interest to the victorious allies. One was captured aboard U-852 in May 1944 and after the war Fa 330s were tested for several years by various nations to assess if it had any possible value.
But with helicopters very much coming to the fore by that point, the Fa 330 and other rotor kites were seen as something of a dead end.
About 200 Fa 330s were built, and quite a few still survive today in museums in Europe and the United States.