Kurt Tank’s First Fighter; The Rohrbach Ro IX ROFIX

August 1, 2022

The German aircraft designer Kurt Tank is justifiably famous for creating one of the most iconic aircraft in history. But I think it is fair to say that he is primarily remembered for one aircraft in particular.

The Indian HAL Marut.

 

HAH! Only kidding.

Of course, actually it is the Focke Wulf 190 series and its offshoots, which from the types first encounter with Allied aircraft in 1941 was recognized as an extremely dangerous opponent.

 

But obviously, Tank didn’t just produce such an excellent fighter out of thin air. Like most of the great designers, his career was part of the continuous drive to improve aircraft and implement new technologies.

But where many designers had far more modest beginnings to their careers (Willy Messerschmitt, Tank’s great rival, for example started by designing and building gliders) Tank started his aircraft designing career at the cutting edge of aero technology. And his first fighter shows this handsomely.

The Rohrbach Ro IX Rofix. A fighter created for Turkey, designed in Germany and built in Denmark.

So how does one get to such a complicated arrangement?

With Germany’s defeat in the First World War, the victorious Allies stipulated in the Treaty of Versailles – specifically Article 170 – that Germany was forbidden from exporting weapons. But interestingly, it didn’t say anything about designing them.

So it was that in 1922 Rohrbach Metallflugzeugbau was set up by Adolf Rohrbach expressly to work on developing all-metal aircraft. This technology had been developed to some extent, with aircraft like the Junkers J 1, an all-metal aircraft, in fact flying in 1915.

 

But there was a long way to go before the all-metal aircraft would be able to replace the existing fabric and wooden airframes that were the norm. And it was visionaries like Rohrbach who would help drive this development, assisted by his new and talented designer, who had only graduated from the Technical University of Berlin in 1923.

Kurt Tank.

At Rohrbach, Tank cut his teeth working in this developing aircraft construction technique, and Rohrbach’s all-metal flying boat designs received a huge amount of interest, with two even being built under licence by the British.

Of course, there was the irritating detail of aircraft manufacture being banned in Germany – hence the establishment of a Rohrbach aircraft factory in Denmark.

So it was, with their flying boats getting so much attention, it was practically inevitable that someone should ask the company if they could turn their energies to more aggressive aircraft.

Thus, it was that in December 1925 the Turkish government approached Rohrbach with a request that they develop for them a new fighter. The order requested two prototypes, with the intention being that a follow up order for fifty would be placed should testing prove satisfactory.

Tank got to work and developed the Ro IX.

 

Construction was actually extremely quick, with the first prototype being ready for flight testing in late 1926. One of the reasons for the rapid development was that Rohrbach had been contracted to develop a fighter for the Japanese Navy in 1924 which ultimately seems to have fizzled out. But the company was able to utilise that preliminary work to create an advanced fighter in an extremely fast time.

The Ro IX had a single parasol wing that was dihedral and semi-cantilevered, with the use of steel wing structures and supports enabling the removal of much of the wing struts that were common in the day. The fuselage was also of all-metal construction, with a thin alloy stressed skin that used flush riveting for excellent streamlining.

Powerplant was a BMW VI water-cooled V12 that produced 600hp and proposed armament would have been two machine guns in the fuselage, with provision for an additional two in the wings.

It is perhaps instructive to look at another contemporary fighter to give an indication of just how advanced the Ro IX was. The same year that the Rohrbach flew, the Royal Air Force was ordering the Gloster Gamecock for service. This aircraft was built entirely of wood, was armed with two machine guns and was of a biplane design with the multitude wires and supports that such a design entailed.

Don’t get me wrong, the Gamecock was a perfectly competent fighter for its day, and certainly equivalent to other countries aircraft. But the Ro IX was really pointing to the future – the era of the all-metal monoplane.

And you can see this in the respective performances. Whilst the Gamecock had a top speed of 155mph (249km/h), the Ro IX clocked 177mph (285km/h). It also had a higher service ceiling.

Of course, all this came with a cost, and that was the aircraft’s spinning characteristics. Testing did in fact show that the Ro IX had very good flight and landing characteristics, but in the spin it could be vicious.

The first major problems occurred on 27 January, 1927 when one of the test pilots crashed the first prototype. He was unhurt, but the aircraft was destroyed.

The spin issue led to the second aircraft’s wing being tweaked several times to mitigate the problem, and by July of 1927 it was thought to have been largely solved. The aircraft had been flown multiple times, not just by the company’s test pilots, but also by several of Germany’s famous World War One aces, notably Ernst Udet, who would go on to be a huge influence on the Luftwaffe when it was created in the 1930s.

Transfer to the Turkish Air Force was scheduled for the 20th of July, the aircraft having even been painted up in Turkish colours.

But then, disaster struck.

On the 15th, only five days before the transfer, the Ro IX was sent up for a demonstration flight. The pilot was Paul Bäumer, another famous fighter pilot who was ranked as Germany’s ninth highest scoring ace from World War One.

Bäumer was working as a freelance test pilot for Rohrbach and took the aircraft up to 5000m, to conduct a spin recovery test. He got the Ro IX back under controlled flight at 3000m, as had been expected.

He then put it into another spin, but something went wrong and the plane crashed into the waters of the Øresund off of Copenhagen. Bäumer apparently tried to bail out but was too late and was killed.

It is difficult to know what went wrong with the Ro IX’s final flight. Kurt Tank, who was watching the demonstration, stated he believed that the engine speed had been too low for the second spin test and as a result the fault was pilot error. Possible, though as the designer of the aircraft he could be accused of having a skewed view of events.

But what is certain is the result. With the second crash and loss, the Turks cancelled their interest in the aircraft. This was apparently followed up by Rohrbach himself destroying all company documentation on the aircraft and refusing to allow his company to develop any more fighters.

And that would be that.

Except of course, Kurt Tank was the designer, and he went on to other things.

Including developing this:

The Focke Wulf Fw 159.

This was built in 1935 to compete for the new German fighter contracts that sprang up in the wake of Hitler taking power in Germany. While it lost out to the Messerschmitt Bf 109, the use of an all-metal stressed skin parasol design certainly harks back to the earlier Ro IX – Kurt Tank’s first fighter.

Sources/Related:

https://de.wikipedia.org/wiki/Rohrbach_Ro_IX

https://de.wikipedia.org/wiki/Rohrbach_Metallflugzeugbau

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