[HolyGrail]

That would be class files or missing texture error .
Make sure you installed everything as it should be in right order .
When there is class files error or missing texture not being loaded , there are many possibilities of outcome .
One of them is that for example , damage model can get disabled for specific situations until problem with
class error file or missing texture is resolved .
It sounds extremely similar to these two things .

I downloaded and installed the Sound Mod and the Aircraft pack last night

you should have been more specific as to what is this stuff you just installed and it could have been installed all wrong .

S! HG