The story of the legendary Dornier Do X flying boat began 100 years ago

The Do X flying boat is synonymous with the work of Claude Dornier.

In 1925, one hundred years ago, the story of the legendary Do X flying boat began.

Dornier was convinced that seaplanes would have a great future in international passenger transport, as all major cities were located on the water or on rivers. His vision of huge passenger flying boats or flying ships was already maturing in 1919, and an initial design from January 1919 was a high-deck flying boat with 8 engines of 270 hp each. This was followed in March of the same year by a revised design with the same motorisation but a modified wing geometry.

On 20 January 1920, the Peace Treaty of Versailles came into force, which resulted in a ban on aviation activities for Germany, among other things. Dornier had begun testing the Gs I flying boat (first flight 31 July 1919), which is to be regarded as the forerunner of the Wal-aircraft, and Wal-aircraft are in turn to be regarded as the forerunner of the Do X flying ship. Due to the Treaty of Versailles, the GS I flying boat was to be delivered to the victorious powers in 1920, which Dornier thwarted by deliberately sinking it.

Dornier was not allowed to build any more aeroplanes for the time being, but the Treaty of Versailles could not prevent the construction of further variants. As a result, the design departments produced further design plans for flying boats, including the Libelle and the Wal.

In order to build the Libelle, a small sports flying boat, Dornier rented a hangar with a direct ramp into Lake Constance in Rohrschach, Switzerland. The components for the ‘Libelle’ flying boat were manufactured in Germany and transported secretly from Germany to Switzerland in a sailing dinghy. On 16 August 1921, the ‘Libelle’ made its first rounds in Staader Bay on the Swiss side of Lake Constance.

The breakthrough for the Dornier seaplanes came in 1922, when Dornier held talks with the Spanish navy about seaplanes and presented design plans for the Wal. The Spanish military were so convinced by the concept that they ordered six Wal flying boats from the drawing board.

However, this order could no longer be processed via the hangar in Rorschach, and aircraft construction in Germany was still severely restricted. Claude Dornier found a solution in Italy. There he founded an aircraft hangar in Marina di Pisa for the construction of the Wal aircraft, Costruzioni Meccaniche Aeronautiche SA. The Dornier Wal built there had its successful maiden flight on 6 November 1922. In addition to the six Wal-aircraft for Spain, further Wal-aircraft were delivered to Holland, Argentina, Chile, Japan, Russia and Yugoslavia.

Parallel to the successes with the Wal-aircraft and the construction of other land and seaplanes, Dornier continued to work on his vision of a large seaplane. In September 1924, he presented the concept of an oversized Wal (internal project number 1190) with 12 engines and a wingspan of 48 metres and a length of 39 metres. However, this seaplane still had nothing in common with the later Do X. The twelve engines were arranged in tandem configuration in front fuselage and rear fuselage.

However, Dornier’s vision of a large seaplane was soon to become reality. In 1925, Dornier had a meeting with the President of the Association of the German Aviation Industry, retired Admiral Lahs. Admiral Lahs was an old naval officer and had a soft spot for seaplanes. Lahs knew about Dornier’s conceptual work on large seaplanes and asked Dornier to tell him about his current plans for a giant metal flying boat. In the course of the conversation, Lahs suddenly asked: ‘Dornier, what would you say if a stranger gave you a pile of money with the order to build a very large boat. Something that wasn’t even there yet?’ *1) After Dornier had digested the question, he simply said: ‘I would be delighted’. 1*)

Dornier was informed that considerable funds were available to continue work on the large seaplane. In the further course of the conversation, after his initial confusion about this development had subsided, Dornier specified the framework conditions for the large seaplane he was aiming for and the corresponding workshops and integration halls, which would not only cost a lot of money but also time.

In conclusion, Dornier said: ‘The design and construction of a large seaplane is one of the most beautiful, if not the most beautiful task I could wish for’. 1*) After a while, another naval officer, a good acquaintance of Admiral Lahs, joined the group and immediately joined in the conversation. ‘Well, Mr Dornier,’ he said, ’how many millions do you need to build us a big, beautiful ship? 1*). Of course, Dornier could not answer this question off the cuff, but it would take a lot of money and time to accomplish such a task.

At the end of the conversation, they toasted with a schnapps: ‘To the prosperity of the Do-X airship.’ 1*) Lahs informed Dornier about the source of the money: ‘You will conclude a contract with the Ministry of Transport, and the money will flow to you from there. Don’t ask any more questions.’ 1*)

Dornier’s vision was taking shape and could be realised with the promised funds. The die is cast for the construction of the Do X.

Dornier’s basic idea when building the Do X was to utilise the advantage of overseas traffic in order to achieve self-sufficiency, i.e. to pass on the costs incurred to a sufficient number of passengers or freight. The dimensions of the airship Do-X resulted from this consideration and the demand for increased safety.1*)

The construction ban was still in force in 1925. So the Do X flying ship had to be built abroad, but the shipyard in Marina di Pisa was too small for the construction of large seaplanes.

Back at the lake, Dornier began to think about the project as such. With a weight of fifty tonnes and a similar performance to the Wal being tested, an output of around seven thousand horsepower had to be installed. This required twelve engines with six hundred horsepower each. In his mind’s eye, a Wal appeared, enlarged to gigantic proportions, with twelve engines mounted in six tandem nacelles on its wings. In June 1926, the project design P 51223 was created, which largely incorporated the experience with the Wal-aircraft. This design was already very similar to the later Do X.

In December 1926, the final design approval and building authorisation for the Do X was granted with drawing P 51335 after a few minor modifications.

The design work was carried out at the Manzell factory. However, construction in Germany was out of the question due to the restrictions imposed by the Treaty of Versailles. And Marina di Pisa was, as already mentioned, too small.

In the search for ways to continue building aircraft, the Dornier aircraft factory in Friedrichshafen found a new shipyard site just a few kilometres above the lake in Switzerland. Claude Dornier found a suitable site with access to the lake in Altenrhein for the construction of a new production facility.

The canton of St. Gallen and the municipalities of Rorschach, Thal and Rheineck supported Dornier in the construction of the factory buildings and the airfield. The intention was to create new jobs in the region, which until then had been structurally weak.

The plan worked out: Dornier Flugzeugwerke (Do-Flug AG) was founded in Altenrhein in 1926, construction of the hangars began and the Dornier factory opened in 1927. At the same time, a 600-metre-long grass runway was laid out, from which the Rorschach-Altenrhein airfield, today’s St. Gallen-Altenrhein airfield, developed.

From 1928 to 1931, the Dornier works in Altenrhein built the three legendary and imposing Do-X seaplanes, one for the German customer and two for the Italian navy. Each of these flying boats, with a length of 40 metres and a wingspan of 48 metres, was equipped with 12 engines that could lift the 48-tonne aircraft out of the water and into the air.

The German Do X1 made its maiden flight on 12 July 1929 and became famous for its test and demonstration flight with 169 passengers on board and its world flight from Germany to South America, North America and back to Germany.

However, the three legendary aircraft are lost forever. Apart from a few fragments, nothing is left of the three aircraft built. The Do X design drawings are also no longer available.

However, the Do X, synonymous with Claude Dornier’s work in the field of seaplanes, is being rebuilt by the Do X Friends and Supporters Association. The complete construction plans should be available again by 2026/27 and the rebuilding has already begun.

*1) According to or adapted from Claude Dornier’s book ‘Aus meiner Ingenieurlaufbahn’ (From my engineering career)