A nacelle may include a pylon and a thrust reverser having an inner fixed structure. A locking mechanism may automatically engage and prevent relative movement between a thrust reverser half and the pylon. A bumper may be coupled to the inner fixed structure. The locking mechanism may limit deflections between the thrust reverser and the pylon in response to a burst duct. The locking mechanism may allow the thrust reverser halves to be opened for access to the engine.