Newer Kitchenaid (krff507hps) makes an occasional helicopter sound. I'd assume it's a fan blade somewhere. It seems to be the upper left side way in back.
The noise stops when a door is opened and starts again when closed. It happened 3 times in the past few months. Each time I turned off the cooling for 15 minutes and it was stopped when I started it back up. The last time it didn't so I let it go till it stopped itself which was about 20 minutes. I'm pretty sure a Condenser fan is in lower back. This seems to be up top.