The requirements of the civil engine authorities certification include the demonstration of a successful fan blade off test performed on a whole engine mounted on a rig. In order to comply with these severe criteria, manufacturers carry out expensive containment spin tests during the development phase of a new engine. However, the numerical Finite Element analyses is an appropriate means to understand the fan blade off event and to prevent the financial and time delay risks caused by any failure occurring in the validation process. In the present paper, the simulation of a fan blade off on the front part of an engine is investigated. The prediction of the engine behavior thanks to a non-linear fast dynamic code is compared to experimental data gathered during one of these containment tests conducted by Snecma Moteurs. The good agreement between the calculated and measured results confirms the reliability of the applied method to assist in the design and optimization of the engine components.