EZY A319/A320 Vibration/Resonating "Wow, Wow" Sound?

[MrJoshua]

Hi All

I was on an EasyJet flight between Barcelona and Doncaster late last night. The flight was smooth and uneventful apart from a regular rolling "Wow, Wow, Wow, Wow" sound coming from the engine(s)/airframe that occasionally could be felt fairly strongly underfoot. I was sat on a starboard wing/exit seat and the vibration was felt shortly after take-off and during descent but a couple of times during cruise (although less obviously).

The sound was like a rough humming noise and was very regular, maybe 0.5 or 1 Hz throughout the whole flight.

No one else appeared concerned about this (apart from my missus who nudged me about it early on in the flight), so wondering if we're just flying wusses, or whether it was something I should have alerted cabin crew about?

Many Thanks

Josh

*** Edit - This isn't the "Barking Dog" Hydraulic noise, something quite different ***

[Anansis]

Hi Mr Josua,

I'm not sure what this specific noise was if it wasn't the "barking dog" hydraulics but there is an interesting thread which deals with whether or not you should inform the crew in these situations:

http://www.pprune.org/passengers-slf-self-loading-freight/408810-safety-when-should-pax-alert-crew.html

[tom775257]

It is probably just the front fan on one engine running at a slightly different speed to the other, this causes the sound you are talking about - more common on twin props, but will happen on turbofans too..

A few years ago now when I flew twin props, we would trim one engine (prop) speed lever to match the other using our ears to stop the beating. When getting more out of sync the frequency would increase, moving towards sync the beat would slow down and then stop.

[MrJoshua]

Hi Tom

That explanation makes sense to me (like trying to mix two records when one is slightly out of sync #DJ).

Good enough for me unless anyone else wants a go :)

Cheers

Josh

[Capot]

Props/fan out of sync has a plausible ring, although I have never ever heard of having to sync jets.

But turbo-props had/have auto sync, don't they, and have had it for decades? If so, and if it's necessary to synchronise the fans on a by-pass jet (??) surely that would be automatic?

[Dan Winterland]

It's certainly fan sync. I've heard it myself often. There is no auto matic syncronisation on the A320, and I've not heard of it on any other turbojet. Although I used to fly a jet which had a syncroscope which had three rotating needles which stopped when engines 2,3 and 4 were syncronised to 1. That was sort of automatic - for the pilots anyway. The flight engineer with the sync with is own set of thrust levers!

[redsnail]

The lil Hawker 800XP has a synch for the N1s. :ok: You need to get it to within 2% and it'll do the rest. ;)

[Nicholas49]

Would the lack of synchronicity between the fan blades show on the engine indicators on the A320 Flight Deck? Or would the pilots only know about it if they could actually hear the vibration?

Sorry for the naive question, but is this a different scenario from the one where both engines do not have the same percentage of N1? In other words, can the fan blades move at slightly different speeds even though both engines are producing the same level of thrust?

[Landroger]

Very slight thread drift here, but having the same theme. As I understand it, British WWII bomber (and twin engine) crews would synchronise their engines to cancel this phenomenon, while the Germans deliberately desynchronised their Heinkel III engines to create a vrrrooom - vrrrooom - vrrrooom beat that would terrorise those about to be bombed. :eek:

It was so pronounced that even my late Grandmother would have easily recognised the difference between a Wellington and an He III from miles away. :)

Roger.

[Flightrider]

Were you on G-EZEA?

[Nubboy]

One of our 319s was doing it the other week. I disconnected the autothrottle and synch'ed it on the N1s. Normal mode is to match the power using EPR setting. If one engine has worn more than the other then the same EPR setting will have one engine running faster than the other.
Normally turbofans don't need synching, but props do. I did 500 hrs on the Trislander, and could get that in synch most, but not all the time. Especially as we had 3 blades on the wing engines, and 2 on the tail. The trick was to set the left one to your chosen rpm, match the right engine and minimise the beat on the rear. The best thing we did was to ditch the old David Clark headclamps and replace them with ANR headsets . Bliss.
Wonder if 411A needs to do it on his dinosaur jet?

[proxus]

Wonder if 411A needs to do it on his dinosaur jet?

Probably not, but then again the L1011 had dancing virgins that had the job of putting Indian silk woven earplugs into the flightcrews ears.

[easyflyer83]

Nothing wrong at all with asking the crew about it. Chances are though that if it was something unusual the cabin crew would have noticed it.

[dubh12000]

It can depend also on where you sit. Someone 2 rows ahead can sometimes not hear it.

[MrJoshua]

Were you on G-EZEA?

It may well have been, that registration rings a bell (unless they're all rather similar). We were stood on the bus for about 30 minutes while they "rebooted" one of the computers due to a fault (on top of a 2.5 hour delay) and I noted that the registration was quite nifty (ie sounds like Easy).

It was flight 7410 on the 20th October - Not sure how to find out which plane I was on?

Thanks for all the comments... Good to know it wasn't anything serious. Maybe I should have mentioned something, but it's knowing what to say!

[champair79]

MrJoshua,

It wasn't G-EZEA but G-EZMS.

All of the EZY registrations start with G-EZ** so that's why you're probably thinking it sounded like 'Easy'.

Hope that helps,

Champ