The First World War was a time of great experimentation for aircraft, resulting in some freaky designs. The R.I is a perfect example, with its great size and distinct, three-storey fuselage.
It was designed as an early long-range strategic bomber at a time when the concept had not yet even been fully established. Therefore we cannot blame the designers for such a creation. We can, however, enjoy its hilarious proportions from the comfort of the future.
Rather than go long, the R.I simply went up, stacking its various compartments on top of each other until its fuselage was taller than the tail of a B-17.
Contents
Background
The Linke-Hofmann R.I was developed during the intense period of First World War, a time marked by rapid advancements in military technology and strategy. In particular, the potential of aircraft to bypass traditional defenses and strike at the heart of enemy territory – a tactic we now know as strategic bombing.
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As the concept of strategic bombing began to take shape, Germany looked for aircraft capable of executing these long-range bombing missions effectively. They were to be very large aircraft, known as Riesenflugzeug (“giant aircraft”), in order to carry enough fuel and bombs for the trip.
This resulted in a number of designs that included several of the largest aircraft in the world at the time, such as the Siemens-Schuckert R.VIII. The wing span of that particular aircraft would remain unbeaten for 16 years.
In 1917, Linke-Hofmann became another manufacturer competing to produce a war-winning Riesenflugzeug. They were originally a locomotive and railway equipment manufacturer, but the needs of the war pressed them into this new field.
Given the task of producing a long-range bomber, the company embarked on the development of the R.I. The aircraft was designed to be a large, powerful bomber capable of delivering substantial payloads over great distances.
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The design of the Linke-Hofmann R.I was very unusual, especially compared to more modern designs, featuring internal engine placement and a three-storey fuselage. This arrangement was intended to enhance the aircraft’s aerodynamic efficiency and survivability—critical factors for the success of deep penetration bombing missions.
It also was intended to maximize the space between the wings of early biplanes. Smaller aircraft and models had shown this was a valid approach, but Linke-Hofmann were taking a gamble implementing this concept at such a large scale.
Due to the strange proportions of the aircraft, it is hard to gather its scale, even from photos. For reference though, it was taller and wider than a B-17 – a full 20 years before that aircraft would fly.
As with all the Riesenflugzeug, only a handful of R.Is would be built. Many others were completely one-off designs.
R.I Design
The Linke-Hofmann R.I is, well, quite an ugly aircraft (although beauty is in the eye of the beholder…). It is characterized by its tall, multi-storey fuselage. The aircraft’s fuselage was large and robust, built primarily to house its multiple engines internally.
Fuselage Layout
This internal placement was chosen to protect the engines from enemy fire and to reduce aerodynamic drag, thereby enhancing the aircraft’s range and survivability during missions. It also made it possible for mechanics to easily access the engines in flight.
On the top floor of the fuselage was the cockpit. The middle floor contained the engines, while the bottom floor contained the bombs and bombardiers. This resulted in a very top-heavy aircraft, with a height of 6.7 meters.
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Access pathways within the fuselage allowed crew members to move between different stations as needed, which was useful for the long-duration missions the aircraft was intended to perform. Almost the entire front of the aircraft was glazed, which gave good visibility in ideal conditions. However, it was found to be detrimental in rain and if the aircraft was illuminated by a searchlight.
Powerplants
Power came from four Mercedes D.IVa inline eight petrol engines. These produced around 260 hp, and were used in a large number of German machines, including the Gotha G.III bomber and Albatros reconnaissance aircraft.
They were designed and built to be mounted inside fuselages, so they were very thin. One quirk of this was the carburetor’s location, which was at the rear of the engine. This resulted in poor fuel distribution to the cylinders. On the R.I these engines powered two propellers, one on each wing.
To transfer power from the engines located inside the fuselage to the propellers, the R.I utilized an intricate system of shafts and gearboxes. These mechanical components extended from the engines through to the middle of the biplane wing structure where the propellers were mounted. This complex internal arrangement required a robust structural design to support the weight and vibration of the engines.
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The propellers’ mounting also helped limit vibrations. Rather than fixing them to the wings, as is common practice, the framework around them did not make contact with the wings.
Construction Materials
The aircraft was mostly made from wood, as was typical of the day. Interestingly, the first prototype was covered in a material called Cellon, which is a transparent, plastic-like film. This material was selected for its degree of transparency, which is useful for improving visibility for the crew, and camouflage.
Another notable advantage of Cellon was its smooth, glossy finish that contributed to a reduction in aerodynamic drag, a critical factor for the performance of large bombers like the R.I. The treated fabric also provided protection against the elements, helping to preserve the integrity of the underlying structure from environmental wear and tear.
Additionally, the transparency of Cellon was particularly advantageous for creating windows and observation panels, allowing crew members better visibility without compromising the overall strength and integrity of the aircraft. But the main motive for its use was as an early form of “invisibility” camouflage. It was hoped that, due to it being transparent, the aircraft would be harder to spot.
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However, Cellon had a number of issues. Namely, it would glint brightly in the sun, something that was easily visible to observers. This effectively negated its original purpose. It also suffered from rapid yellowing, making it more opaque. Finally, the material changed in size depending on temperature, affecting the behaviour of the aircraft in different conditions.
As a result the Cellon skin was replaced with camouflaged fabric in the following examples. Another unusual feature of the R.I was the heavily sprung steel-banded landing gear. That’s right, instead of rubber tires, the R.I’s wheels were steel.
All in, this ungainly-looking aircraft weighed 12 tons fully loaded, and could reach a top speed of 81 mph. Its wing span of 33.2 meters made it very large for its day.
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However, perhaps most importantly, the R.I had an endurance of 5 hours, something very useful for a long-range bomber.
Testing
The first flight occurred in early 1917 with the first prototype, designated 8/15. This aircraft was fitted with the transparent Cellon skin. These test flights quickly highlighted both its potential and its many limitations. Something noted was its concerning wing flexibility, which was likely the result of a delicate construction.
This caused “mushy” handling in flight, with one of the test pilots noting that the aircraft was almost uncontrollable.
This had deadly consequences in May of 1917 when the first prototype’s wings collapsed at low altitude. The subsequent crash killed one (some sources state two) of the crew. 40/16, the second prototype, was built later in the year and received changes learned from the crash.
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It received additional bracing in the wings for strength, and added dorsal, belly and waist gun positions. With these changes, the aircraft was said to have been surprisingly maneuverable.
While this aircraft performed better, the tall fuselage was found to be a problem. It brought very little benefit but made the R.I top heavy (particularly if it had released its bombs), and gave the pilots visibility issues. This made landings difficult, as the pilots had a hard time judging the aircraft’s distance from the ground.
Eventually, 40/16 was also destroyed in a crash, this time nosing over on landing. This was likely a result of the tall, top-heavy fuselage and visibility issues mentioned above. Another two aircraft were reportedly completed by Linke-Hofmann, but there are no surviving records on what happened to them.
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In the end, the R.I never saw any combat and is regarded as a failure. It must be remembered though that this was a time of pioneering work where designers were quite literally writing the book as they went. That, combined with the fact that Linke-Hofmann had minimal experience in aircraft design, it is an impressive achievement that it ever flew at all.
