Development and Validation of a Dynamic/Probabilistic Method for the Assessment of the Trajectories of Parts Detached from Rotorcraft (PDR)

The objective of this thesis is the assessment of the probability distribution function (PDF) of parts detached from an helicopter, striking the helicopter itself. We will treat two PDRs: the passenger window and one exhaust terminal debris. Given the non deterministic nature of the problem, the most suitable method consists in a Monte Carlo (MC) simulation to obtain the required PDF. The Monte Carlo approach is simple in nature. Consider the following problem: the trajectory of a PDR like a window is heavily influenced by its initial conditions, as a small perturbation in attitude near the stall region produces an unpreadictable flow field, thus high oscillatory forces and moments; how can we obtain the most probable trajectory? We could perform a large number of experiments, each with different boundary conditions, then count the occurences of collision events over the total number of experiments, yielding an approximation of the actual probability of the event. The associated likelihood of the events is expressed as the number of occurences per flight hour, while the associated risk shall be evaluated conforming to the European Risk Classification Scheme (ERCS) or SAE Guidelines for Safety Assessment.