A321 v2 noise (not PTU)

[Tommohawk]

Hi. Not sure if I'm posting in the correct area - I'm not a professional, so this looks nearest.

Boarding an A321 today and couldnt help noticing a loud noise coming from the port/number 1 engine. I can best describe it as a clanking/clattering, similar to the sound you might get from a couple of half bricks in an empty concrete mixer.

Drew this to the attention of cabin crew, and basically advised it was nothing to worry about. Not that anyone took the trouble to actually check it out.

Anyhow from inside the noise was not apparent, and the engines seemed perfectly normal throughout the flight and landing.

I am very curious what the origin of this might be. I couldn't see any other equipment nearby - the noise seemed to come from the turbine. I know pretty much nothing about aircraft engines, but have rebuilt many car and M/C engines, and if any one of them made a noise like this, I wouldnt be thinking of driving it.

Any thoughts? Thanks in advance.

[KBPsen]

You are of course correct in comparing a turbine engine to a car engine. What you heard was most likely an incorrectly fitted timing belt causing a piston to make contact with an intake valve. It is a common problem on turbine engines.

[Dct_Mopas]

Ignoring KBPsen's answer, the noise is an everyday occurrence when the wind drives then fan blade at a (comparatively) slow rotation speed.

Each individual blade sits in what can be described as a slot. With the engine at a high rotation speed the blades are held perfectly in place by centrifugal force. They also have a fair bit of movement on the ground as they have room to expand as they heat up during normal operations.

So on the ground each blade will drop slightly (by a few mm) as it reaches the 12o'clock position as the centrifugal force is too weak. As soon as the engine is started, or the wind really picks up, the fan blade spins at a fast enough rate for no movement and so no noise.

Hope that helps!

[Cymmon]

Sounds fantastic, like a can of marbles when you de-plane in Butuan.
You think the engine is about to fall off.

[Tommohawk]

OK, DCT_Mopas thats a very helpful answer - and makes perfect sense.

Hmmmm... centrifugal force .... I thought that had been declared unfit for purpose??!!. Only kidding ;)

Cymmon, +1 for the can of marbles sound effect.

Thanks very much for the info and reassurance!

Cheers,
Tom

[WHBM]

As DCT says. The BAe146 with the original ALF502 was particularly noteworthy for the blade rattling when crossing the ramp on a windy day.