What causes that noise?
Boarding my A320 this week I heard a rattling noise coming from the slowly turning fan. It was not unlike a washing machine drum slowly turning with a load of loose metal chunks inside. I’ve heard this many times before and I’m still here to ask the question so it’s obviously nothing serious. I am intrigued though as to what causes the noise. The power pack was a CFM56-5B4/P if that makes any difference. Any ideas guys?