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However different the Link Trainer and the Diamond Simulator may seem, they essentially serve the same purpose: to enable pilots to learn how to fly and handle an aeroplane. However, there is a 70-year age gap between the devices, as well as a host of technical differences. This raises two questions: What developmental steps actually lay between these seemingly completely different technologies? And how did the practice of “learning to fly” change alongside the devices?

Whilst thousands of pilots were still being taught essential flying skills on the Link Trainer during the Second World War, efforts were already under way to develop a new generation of flight simulators. In 1941, Richard Carl Dehmel (1904–1992) filed a patent application in the United States for a “device for flight training”, which was granted to him in 1950. According to Dehmel’s ideas, his invention was intended to fulfill two purposes: Firstly, it was intended to familiarise flight students with an aircraft’s response to their control inputs. Secondly, it was designed to train them to fly purely by instruments using ground-based radio infrastructure for navigation when external visibility was lacking.

Dehmel’s invention was designed to simulate all the radio navigation signals that a pilot of the time would receive during an actual flight: the signals from a radio beacon, the glide path and the approach signals of an instrument landing system, as well as the signals from an “A-N radio range”, which were received in the cockpit via headphones as audible Morse code signals for “A” and “N”. (If “A” and “N” overlapped to form a continuous tone, the pilot was on a predefined heading.) Another distinctive feature of this new generation of flight simulators was that the devices were now based on analogue computers, which calculated the state of the simulated aircraft in the air in real time.

In 1943, several years before his aforementioned patent was granted, the US aircraft manufacturer Curtiss-Wright hired Richard Dehmel and launched the first electronic simulator in 1946. After the Second World War, a duopoly developed between Curtiss-Wright and Edwin Link’s company, which was now also offering computer-based simulators. Curtiss-Wright sold the first electronic flight simulator for civilian use to Pan American World Airways. Link was awarded the contract by the US military to build the first simulator for a jet-powered aircraft with its “C-11” model series. A C-11 that was once used by the German Air Force is now also part of the Deutsches Museum’s collection. This new generation of electronic simulators quickly became established, despite their complexity and the notorious unreliability of the vacuum tubes used in them. Furthermore, the purchase of a fully-fledged electronic simulator involved enormous costs; prices were in the six-figure dollar range.

However, several advantages of the new devices stood out in comparison to flying in a real aircraft: training sessions in the simulator were significantly cheaper and could take place regardless of the weather and other air traffic. Furthermore, technical faults and emergency situations could be practiced safely on the ground, without risking a potentially fatal crash. In 1949, Pan American forwarded an internal study to Curtiss-Wright with words of appreciation: thanks to their simulator, safety standards in pilot training were higher, costs were lower and the duration of training was shorter than ever before.

Alongside the expensive simulators, Curtiss-Wright also manufactured a more affordable product range, the ‘Dehmel Flight Duplicator’. Whilst the simulators elaborately replicated a specific type of aircraft, including its flight characteristics and cockpit instrumentation, the Flight Duplicator was primarily a training device for radio-based navigation procedures. One such device has been part of the Deutsches Museum’s collection since 2021. As very little documentation on these objects has survived and only a few other devices are held in the collections of other museums in the USA, it is all the more revealing to examine the museum’s own Flight Duplicator at close quarters in the depot.

The instructor, who led the training session in the Flight Duplicator, was seated on the left-hand side of the cockpit. At the heart of his workstation was the “Dehmel Automatic Radio Aids Unit”, featuring a control panel where the instructor set the key parameters for the exercise in question. These included weather conditions such as wind direction, wind speed and temperature; for training in instrument landing procedures, the altitude and direction of the simulated runway as well as the glide path and the approach markers for the final approach were configured. The parameters for the simulated “A-N radio range” were also set here.

The instructor’s station also had another key function: the flight path completed by the trainee was automatically plotted onto a chart disc using a pen. This allowed the instructor to monitor in real time whether the trainee was on the prescribed course; furthermore, he could subsequently discuss the trainee’s ‘navigation performance’ with them using this record. One such chart disc is still clamped into the Automatic Radio Aids Unit in the museum’s depot. This reveals a direct link to the Flight Duplicator’s former place of operation: in the typical style of an aeronautical chart, important landmarks around Hamburg Airport are marked on it. These include, for example, the two runways 05/23 and 15/33, the final approach to runway 23 on a heading of 232°, and the corresponding outer approach marker directly in the center of the circular chart.

The object of the Deutsches Museum was previously used by Lufthansa to train its own pilots. Lufthansa purchased this Flight Duplicator in 1957 for $150,000 from Curtiss-Wright and put it into operation in the newly completed ‘simulator building’ at Hamburg Airport. It was not the only piece of equipment housed there. Between 1957 and 1958, several electronic simulators were added: a simulator for the Lockheed L 1049-G Super Constellation and one for the Boeing 707, both from Curtiss-Wright, as well as a simulator for the Vickers Viscount from the British company Redifon.

In the absence of precise records regarding the use of the Flight Duplicator and the other simulators mentioned at Lufthansa, it is worth comparing the situation with that of other airlines. The US-based Trans World Airlines also brought together simulators and procedural trainers in a single training center. The two types of equipment were intended to complement one another through their respective areas of application. An advertising brochure explained that, across a total of five simulators, crews practiced the airline’s standardized procedures as a team. Much of the training was devoted to emergency procedures, whether in the event of a fire, engine failure or other technical malfunctions. Four Flight Duplicators, on the other hand, were designed to enable precise training in radio navigation procedures.

It is remarkable how quickly international airlines integrated this new generation of simulators and training equipment into the training of their own pilots. Lufthansa, newly founded in 1953, began training its own pilots from scratch in 1955, and by 1957 it was already operating a dedicated simulator building. The proportion of simulator hours in commercial pilot training increased even further in the years that followed. In 1979, a conference of the simulator industry in London noted that simulators had by then been developed for 80 different aircraft models. In 1981, in the USA, retraining for a new aircraft type was permitted to take place entirely in a simulator for the first time; a check ride in a real aircraft was no longer required.

During this period, simulators and procedural trainers such as the Dehmel Flight Duplicators not only helped shape pilot training practices but also had an impact on the safety culture in civil aviation and on the pilot’s role itself. The increasing complexity of modern aircraft technology and the growing density of air traffic made adherence to standardized, internalized procedures at the cockpit workstation all the more relevant. Repeated practice in simulators and procedural trainers as well as the attempt to train pilots to react confidently in real flight operations by exposing them to every conceivable malfunction scenario, was intended to contribute to the reliability of flying.