Many TBO techniques for Trajectory Management for arrivals involve either speed management by ATC or time management by the aircraft. However, in high density operations, both speed management and time management exhibit too many uncertainties, making them incompatible with high-density arrival operations. In previous research, the benefits of an alternative method of managing trajectories in a speed managed environment, have been demonstrated. In this alternative method, geometric descents are employed. Using these fixed angle descents, many uncertainties are eliminated. However, since such descents are flown off-idle, a different balance between capacity and flight efficiency is created. On the other hand, opportunities exist to allow aircraft to fly idle descents, when higher uncertainties can be permitted due to specific operational circumstances. This study will research the uncertainties associated with idle descents and off-idle geometric descents within the CTA related to EHAM. A model demonstrating the dynamic application of both descent techniques in a 24H operation will be developed based on determined criteria, and compared to static applications of the descent techniques.