The goal of this research project is to develop a novel test methodology which can be used for optimizing cost and time efficiency of helicopter-ship qualification testing without reducing safety. For this purpose, the so-called “SHOL-X” test methodology has been established, which includes the associated predictive software tool as developed in this dissertation. The test methodology consists of three distinctive phases. In phase I the ship-environment in which the helicopter will operate is determined by conducting wind tunnel measurements of the airflow in the take-off and landing paths of the ship. For the helicopter a ground assessment and shore-based hover trials are carried out to verify precisely the helicopter limitations, including aspects such as pilot workload in cross-wind conditions, engine performance and control margins. Thereafter, in phase II, the potential operational limitations are derived by combining the behaviour of the isolated helicopter and the environmental conditions for a particular ship type. This so-called “Candidate Flight Envelope” is used as starting point for sea trials. Finally, in phase III, a (partial) flight test campaign on board the ship is conducted preferably in a range of weather conditions by day and by night. This is to determine for the particular helicopter-ship combination the effects on the pilot workload from, for example, visual references, ship motion and turbulence. The main advantage of the new test methodology, aided by the presented predictive tool, is that the operator can perform early evaluation of safety limits for helicopters operating on ships in a wide range of in-service conditions. In this way the qualification process is less dependent on the successful outcome of solely qualitative assessed test points during dedicated sea trials. As such, the test methodology can be used to allow a well-considered assessment of the gap between the safe flight envelope, as determined by the helicopter manufacturer, and the user-defined operational flight envelope for a particular helicopter-ship combination. Additionally, the tool allows initial assessment of the impact of design changes to both helicopter and/or ship after the finally established operational limitations have been released to service with regard to flight performance and control capability. The newly developed predictive tool in this dissertation, is considered original, and can be seen as the most important novelty of this work. The innovative test methodology, including the associated predictive tool, has already been successfully applied between 2012 and 2014 during the helicopter-ship qualification process of the NH90 NFH across the entire Dutch fleet. The academic research is mainly performed somewhere between technology readiness level 2 (i.e. technology concept and/or application formulated) and technology readiness level 4 (i.e. model and/or sub-models validation). However, the validation sea trials at full-scale enabled the high ambition of this research project to be achieved: technology readiness level 7 (i.e. model demonstration in an operational environment). This high aim might seem ambitious for an academic research; although the reader should fully understand that the aim of this research is to reduce the number of flight hours for helicopter-ship qualification testing without reducing safety. The innovative test methodology enables the construction of operational limitations by two different options. The first and most common option is using dedicated sea trials in which the potential boundaries for the various take-off and landing procedures are validated. The second option, is the construction of the operational limitations for Hot & Heavy conditions by desk-top analysis alone, i.e., above approximately 25 °C outside air temperature (hot) with maximum weight of the helicopter (heavy). The construction of the operational limitations for Hot & Heavy conditions are based on the data gathered during shore-based hover trials and the flight test results for other referred weights (i.e. helicopter weight as a function of air density) on board the same ship type. The construction of operational limitations by desk-top analysis alone is a novel approach, and can be seen as the most important achievement of this work. Unfortunately, the establishment of helicopter-ship operational limitations is still considered a national responsibility, and there are no internationally agreed regulations or standard procedures. Consequently, the kind of interpretation given to such limitations differs strongly between countries. Therefore, as it is assumed that each country or operator aims for maximum operational flexibility of a particular helicopter-ship combination, with minimal expenses and without any concessions in flight safety, this dissertation has the ambition to function as the starting point for international regulations or standard procedures to conduct helicopter-ship qualification testing.