This would be an art/sound/engine request. The helicopter already has localized damage as a concept (different components can receive damage at different rates and fail at different times). This would be just applying that a) more visibly and allowing this to result in crashes that don't destroy all components completely. To this end, I would suggest that upon crashing, the MROT and the ATRQ both get destroyed but the HULL and the ENG carry on at only a highly damaged state. The tail boom might break and the landing struts (or gear) would be damaged but the textures would localize the fire damage to the engine area. The MROT would also still be visible but in a broken state. Lastly, after the crash, the turbine would still be heard whining down and maybe have a particle effect for the damaged exhaust. This would require a slight texture change to the damaged helicopter and a persistent sound effect being added as well as a particle effect being added for the turbine exhaust.
examples
http://www.youtube.com/watch?v=CP6kDgGSzM0
http://youtu.be/HWEA06k3LIc?t=49s