engine rattle!!

Member for

6 years 9 months

Posts: 24

Hi all, I'm new to this aviation forum this being only my second or so post. My wife and I have just been on holiday and travelled on an Airbus A321 with CFM (I think) engines, I have 2 questions that I would like to ask any engine experts out there. Firstly, we sat in row 9 for both flights and noticed the engine whine was very pronounced whilst in the climb, we have travelled in front of the wing many times on other aircraft with wing mounted engines and haven't noticed a whine this loud before, is this a quirk of the type of engine fitted? Secondly when we disembarked the aircraft the Port engine was still winding down and the chinking noises it was making could be heard whilst still inside the cabin, I have heard this chinking noise before but never a loudly as this, the cabin crew must have heard it and didn't seem to be in the least bit concerned, I was wondering what could be making the noise. It sounded for all the world like the fan blades were catching on the engine casing. Any info will be greatfully received. Mark.
Original post

Member for

14 years 11 months

Posts: 997

The aircraft was powered by CFM-56's. You can tell by the clanking when you were getting off. The fan blades are fixed into the hub in a way that allows them to move circumferentially. This allows them to move around to sort any minor imbalances in the blades as the engine starts. Once the engine reaches ground idle centrifugal forces lock the blades into position. This is the same as all fans. Certain fans have narrow chord fan blades and are built with snubbers (small fins cast into the upper and lower blade surfaces) these prevent the blades bending at high power settings. The fan will be blown around by the wind on the ground and because there is not enough centrifugal force to lock the blades into position they move about. The clanking noise is the snubbers hitting each other. The "Broad cord" Fans do not have the snubbers so they don't make the clanking noise. The fan whine you heard during the climb out is the typical noise a hard working fan makes. It's something due to pressure waves and stuff that's beyond me! All that I know is that is a magical sound that makes the hairs on the back of my head stand up! Rgds Cking
Profile picture for user nibb100

Member for

13 years 1 month

Posts: 346

I must admit they do have a very distinctive whine, when they come over my house on approach 10 miles from Heathrow you would think there was a Viscount coming over, very nostalgic,

Member for

6 years 9 months

Posts: 24

Thank you for the very informative reply just what i was looking for.