## 1 Introduction  
The development of new products with complex human-machine interfaces ideally follows a user-centered design process [1]. In this process, prototypes are iteratively developed based on user requirements, as evaluated by users in usability tests. However, prototyping is time-consuming and expensive [2]. To reduce these costs, companies use virtual prototypes at the beginning of their development process [3]. Virtual reality (VR) technology offers the possibility of visualizing and experiencing virtual prototypes in detail. Users can test and evaluate the prototypes early in the development process by simulating the anticipated real-world environment in which the prototypes will eventually be utilized [4]. A literature review by [PERSON] et al. [5] shows that the application areas of user evaluation in VR are the automotive (37%), engineering (26%), and academic or unspecified (37%) sectors. In all three fields, VR is primarily applied to review design. In VR design reviews, the prototype is presented to the development team, experts, and users in three dimensions, thereby revealing the optimization potential and improving the efficiency of the development process [6, 7, 8, 9, 10, 11, 12, 13]. User testing is one of the most reliable methods for evaluating the usability of a prototype. Future users operate the new product and perform typical work processes [14]. Initial studies showed that the results of user testing in VR can be transferred to reality. However,in these studies, the prototypes and products were not tested in a pure VR environment, but in mixed reality environments [15; 16; 17; 18]. In these tests, virtual environments were mixed with real controls, such as a steering wheel, because the lack of haptic feedback can limit the prototype evaluation [19; 20]. However, purely virtual prototypes are advantageous, particularly during the early development phases. Different concepts and combinations of human-machine interfaces can be tested, independent of control elements or other real content. In addition, user tests can be performed regardless of location, allowing users anywhere in the world to be included in testing. Virtual user tests are particularly useful for complex machines and devices with a high demand for operational safety, such as control rooms, drilling rigs, and medical devices. To minimize possible usability issues and the resulting hazards to the environment and humans, numerous prototypes need to be tested, which results in high development costs and long development times. However, studies examining complex devices or machines in VR are scarce. [PERSON] et al. [21] conducted a user test in VR using a tunnel-boring machine. In this study, the influence of two different transparency levels of a machine boom on the work performance was investigated. The findings of the study enabled the identification of the preferred transparency level among the operators. [PERSON] et al. [22] investigated the suitability of VR for evaluating the control rooms in nuclear power plants. The test subjects rated VR as a suitable means for evaluating the control rooms. However, neither study validated their results with an evaluation in the real world. User tests in VR offer high potential for the development of offshore or onshore drilling rigs, which feature human-machine interfaces comprising various controls and displays. Onshore drilling rigs are used for deep drilling operations in the exploration for oil, gas, and geothermal resources on land. A driller is responsible for the drilling process. This person controls the drilling process from a driller cabin, monitors several displays, and operates the technical equipment of the drilling rig. Catastrophes such as the Deepwater Horizon explosion in the Gulf of Mexico show the importance of the user-oriented design of human-machine interfaces in this industry [23].