Painting aircraft engine fire damage to fuselage/wings.

I would do this the same way I do "sooty" exhaust, only with a heavier hand. A base of Tamiya Smoke folllowed by black pigment on top. Depending on what you're using, you may be able to "fix" the pigment by dabbing it with thinner. MIG pigments work that way, but pastels and powders generally won't fix, and when you hit them with a clear coat they'll separate and float into little clumps.

Sorry for the delay in replying due to my office at home having been stripped and refurbished.

Thanks for the ideas

Keep these damages limited as aluminum has a low melting point. Any severe fire will result in a puddle of molten metal on the tarmac. Get good research photographs of said fires to keep it realistic.

First off get a soot black weathering powder to simulate the... black soot. Now aluminum turns white before melting. This being said paint the 'hot metal' white BEFORE adding the powders. Another consideration is powders are messy & should not be over coated  with a flat clear / mat finish as these 'soak up' the weathering pigments....SO:

Have the model secured on a base or be able to handle it with a gloved hand by a wing or fuselage before adding weathering powders. 

'Once the powders are applied its finished'

Also welcome to the forums PhilB