As part of a project to modify one of the engines of a Cessna Skymaster to operate on hydrogen, a test set-up is designed. A crucial part of this design is the Safety Analysis, for which a risk analysis must be performed. In this thesis, an in depth analysis of the probability of one of the risks involved in engine testing with hydrogen is conducted: the risk of catastrophic engine failure as a result of an increase in pressure and/or temperature inside the cylinders. It is found, that, although a small increase in peak temperature and a significant increase in peak power is found for hydrogen compared to Avgas, the risk of catastrophic failure is probably low. A final numerical simulation is proposed to obtain a definitive answer, and experimental validation experiments are proposed to increase the accuracy of the risk analysis.