If you wanted to travel across the Atlantic in the 1920s, your choices were rather limited which inspired the creation of the Dornier Do X. You could take a ship, but that journey could take anything up to 12 days.
From the late 1920s, mighty Zeppelin airships provided a much faster alternative, but flights were few and very, very expensive. What was needed was a reliable passenger aircraft capable of making return flights between Europe and America.
There were a number of problems. Most notably, the aero engines of the period were less than totally reliable. It wasn’t uncommon for engine problems to force aircraft to make unscheduled landings. For over-land flights, that was possible. For long over-water flights, it wasn’t an option. That was where the notion of using flying boats on transcontinental flights came from – a flying boat could land safely anywhere there was a sufficiently large body of water.
By the 1930s, elegant American Boeing 314 Clippers were regularly crossing both the Atlantic and the Pacific Oceans and British Short Empire flying boats were making trips from the UK to Africa, Asia and even Australia.
However, long before British and American flying boats were in service, a vast and luxurious German flying boat would briefly become the largest aircraft in the world.
Claudius Dornier completed his studies in engineering at Munich Technical College in 1910 and immediately began looking for a position with an aviation company. He was able to find work with the Zeppelin airship factory at Friedrichshafen, on the shores of Lake Constance in southern Germany. However, Dornier was always more interested in aircraft than airships.
The Zeppelin company was at the forefront of the creation and use of new alloys. Zeppelin used a metal framework to give them rigidity, but building this out of steel would have made them too heavy to fly.
Instead, they used new lightweight alloys to provide strength. Dornier was interested in applying this new technology to the design of aircraft and in 1912, Ferdinand, Graf von Zeppelin permitted Dornier to found a separate aircraft works at Lindau, a few kilometres south of Friedrichshafen.
This culminated in the creation of the Zeppelin-Lindau D.I fighter which made its first flight in June 1918. Although it was too late to see service with Germany during the war, this was a remarkably advanced little aircraft. It was the first single-seat fighter to use a stressed-skin, monocoque structure that was far stronger than the wood and fabric construction of most contemporary military aircraft.
However, during the war, Dornier also designed an all-metal seaplane, the massive Zeppelin-Lindau Rs IV. This was a parasol-wing monoplane with four engines mounted in a pair of push/pull pods between the wing and the lower fuselage which contained the cockpit and sideways-projecting sponsons which gave stability on the water.
The Rs. IV (designated a Riesenflugzeug (Giant aircraft) by the Imperial German Navy) was intended as a long-range maritime patrol aircraft, but only one was completed before the end of the war.
In 1923, Claude Dornier was able to take over the Zeppelin-Lindau works and establish for the first time his own company, Dornier Flugzeugwerke. One of the first new designs to emerge from Dornier was that of a flying boat, the Do J Wal (Whale).
This was another parasol-wing design using sponsors to provide stability in water and a single push/pull engine pod above the wing. The Wal was first produced in 1925 and proved to be a long-lasting and reliable design, being used in several pioneering flights and produced in both military and civilian versions until 1932. However, even while the Wal was still in production, Claude Dornier was working on the design of a much larger and more impressive flying boat.
In terms of innovation, there was little that was truly new in what Dornier named the Do X. This was a shoulder-wing monoplane using a stressed skin over a Duralumin structure on the fuselage and fabric covered with aluminium paint over a Duralumin structure on the wings. Stability on the water was provided by a pair of wide sponsons attached to the lower hull (these also provided passenger and crew access to the aircraft) and the engines were mounted in pairs in nacelles above the wing.
What made the Do X different was its sheer size. With a wingspan of over 155 feet and a length of over 130 feet, the Do X was directly comparable in size to a modern Boeing 767-300 airliner.
Power was provided by no fewer than twelve 500 horsepower Siemens Jupiter nine-cylinder radial engines mounted in pairs in six nacelles. The engine controls were so complex that the pilot had no direct control: as on a ship, the pilot would relay engine commands to the flight engineer via a command telegraph.
There were three separate decks, with the upper deck containing the cockpit, navigation office, engine control compartment and radio room while the main deck provided the main passenger seating area (which could be converted to sleeping berths if required), writing rooms, bathrooms, a kitchen, bar and a 60-foot-long dining area. The lower deck contained nine watertight compartments and fuel tanks.
When it made its first flight from Lake Constance in July 1929, the Do X became the largest heavier-than-aircraft to fly (though it was surpassed a few years later by the even larger Tupolev ANT-20 Maxim Gorki).
In October of the same year, it set a new record when it took 159 passengers (mainly journalists and Dornier workers) and 10 crew on a 45-minute flight around Lake Constance – this number of passengers carried on a single flight would not be exceeded for more than 20 years.
In the twelve months following this record-breaking flight, a great deal of work was done on the interior of the Do X in order to make it as luxurious as possible (it was intended to compete directly with first-class accommodation provided on passenger liners). Passengers would sit in upholstered leather armchairs in spaces that featured Persian carpets and richly decorated furnishings.
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Although it was designed to provide space for up to 100 passengers, on most flights it was assumed that just 40 well-heeled passengers would be carried on most flights.
The aircraft engines also received an upgrade. The air-cooled Jupiter engines proved to be underpowered and the aircraft was unable to climb above around 500 feet when fully loaded.
They were replaced by more powerful, water-cooled Curtiss Conqueror 12-cylinder engines, each producing over 600 horsepower. The more powerful engines allowed the Do X to achieve around 100 knots and to climb to a slightly higher altitude of around 2,000 feet fully loaded, far short of its design cruising altitude of 10,000 feet but felt to be sufficient for a safe transatlantic journey.
The Do X in Service
On November 30th 1930, the Do X took off from Friedrichshafen bound for New York. This was planned to be a triumphant vindication of German technology and design, but that wasn’t how things worked out.
Although it had been designed with transatlantic travel in mind, the Do X had a major problem: fuel consumption. The more powerful Curtiss engines allowed the flying boat to gain a little more speed and altitude, but at cruising speed the 12 engines drank around 400 gallons of fuel each hour. For this reason, its first long-distance flight was a series of short hops to allow for frequent refuelling.
After leaving Friedrichshafen, the Do X flew to the Netherlands, England, France, and Spain before landing in Lisbon, Portugal on 29th November. There a fire destroyed most of the port wing.
Repairs took more than six weeks and then the Do X made several short hops down the coast of West Africa before heading west to the Cape Verde islands where it landed in June. It then finally completed a crossing of the Atlantic to reach Brazil before turning north and reaching New York on 27th August 1931, a less than impressive flight time of over nine months!
The return journey was rather better, with the Do X leaving New York on May 21st, 1932 and arriving in Berlin three days later, on May 24th. However, by that time the world was in the grip of the Great Depression and there was no market for a luxury airliner with extremely high fuel consumption.
Dornier, unable to fund further flights, handed the Do X over to Deutsche Luft Hansa, the German State airline in the summer of 1932. After some short trips around the German coast, the Do X set off on a journey to Istanbul in 1933, but it only got as far as a reservoir near the city of Passau in Bavaria before it was badly damaged during a landing accident.
It was clear that Luft Hansa had no interest in such a large and complex aircraft and after it was repaired, it returned to Berlin where it was placed on display as the centrepiece of the new German air museum, the Deutsche Luftfahrt-Sammlung.
It never flew again and remained on display until it was badly damaged by Allied bombing in 1943. Most of the remains were removed by scrap-merchants in 1945. A few fragments of the tail are all that remain of the mighty Do X and these are currently on display at the Dornier Museum in Friedrichshafen.
Italian Do X
Although only one Do X was operated by Dornier and then by Luft Hansa, two further examples were sold to Italy. In 1931, the Italian airline Italian Società Anonima Navigazione Aerea (SANA) purchased two examples, the Do X2 “Umberto Maddalena” and Do X3 “Alessandro Guidoni.” Although both were purchased with the intention of using them on Mediterranean air passenger services, this does not seem to have happened.
The main problem was that both Italian examples were provided with 12 Fiat engines, each producing just over 440hp, which further degraded already marginal performance with a full passenger load. Instead, both Do X were used by the Italian armed forces as long range maritime patrol aircraft.
They were even tested as bombers, which included the addition of a glazed bomb-aimer’s station in the lower rear hull. However, Do X2 was damaged in a series of accidents and withdrawn from service in 1935 and both Italian Do X were eventually scrapped in 1937. No trace of either remains.
In the 1920s, there was considerable interest in the development of a transatlantic airliner. That’s where the idea of the Do X was born, but this aircraft was hampered by some serious flaws. Most notable was excessive fuel consumption which restricted it to relatively short hops.
A lack of engine power also meant that it could never rise much above 2,000 feet while carrying passengers. That would have involved flying through rather than over variable weather over the Atlantic, something that most passengers would have likely found extremely distressing no matter how luxurious their surroundings.
However, this aircraft’s main problem was one of timing. It was very expensive to operate and relied on wealthy passengers who were willing to pay a great deal for luxury travel. It made its first flight to the US just as the impact of the Great Depression were becoming obvious. The market for luxury travel was shrinking dramatically and no airline other than SANA showed any interest in purchasing the Do X.
The Do X was a bold experiment and one of the biggest and most instantly recognisable of all inter-war aircraft. But it was also much less commercially successful than the smaller Dornier Wal flying boats which continued to provide airmail and passenger services across the South Atlantic until 1938. Bigger isn’t always better…
- Crew: 10-14
- Capacity: 66-100 passengers
- Length: 40.05 m (131 ft 5 in)
- Wingspan: 47.8 m (156 ft 10 in)
- Width: 4.8 m (15 ft 9 in) maximum hull beam
- Height: 10.25 m (33 ft 8 in)
- Gross weight: 49,000 kg (108,027 lb)
- Powerplant: 12 × Siemens Jupiter 9-cylinder air-cooled radial piston engines, 391 kW (525 hp) each
- Maximum speed: 242 km/h (150 mph, 131 kn)
- Range: 1,700 km (1,100 mi, 920 nmi)
- Service ceiling: 3,200 m (10,500 ft)