Even if the probability of a combustion chamber burn-through is unlikely in modern aeroengines, the behavior of the engine has to be considered in term of airworthiness and safety. The whole 3D flow field inside the bypass duct of two aeroengines, BR710 and BR715 were simulated numerically in the event of a combustion chamber burn-through. The simulations showed the effect of different burn-through hole sizes on the bending of the torch and on the maximum temperature of the bypass duct. Utilizing the latest CFD methods the hypothetical case of an additional failure of the bypass duct structure was also simulated. These simulations also showed that both engines retain their integrity for the various burn-through scenarios.