Engine sounds??

[Robini]

Hello!
I have noticed one thing about the engines on the A330.
When im at ESGG, everytime the A330 shall takeoff the Trent
engines sounds so quiet,why??
When Novair took off with their A321 (V2500) the engines was roaring
so much as the whole terminal building was shaking!
And the question is why does it sounds like this, can it have something
to do with flex??

//Robini

[BerksFlyer]

Well flex is a downrating so probably not.

[Robini]

So you cant hear if the plane uses flex or not??

[Mark1234]

I don't know how 'flex' is downrated, or anything like that, I only fly lighties.. but simply, if the runway is long, and / or the load is light, it seems to be normal practice to use less 'throttle' on t/o. Consequently, the engine makes less noise.

Apparently it's got very beneficial effects for the service life of the engine.

[Tight Slot]

The 330 trents run a very high by-pass so most of the air coming out the back is low speed and thus low noise. Lots of air in and out but not at great noise levels. Stack load of power (72000 lbs each side) but the thrust is mainly from the N1 - ie the low speed fan so, not waking up the neighbours!

[Robini]

Thanks for the RR Trent explain ;)
But why does the V2500 sounds so much??
When i saw the A321 took off from GOT she used a lot of flex
(she used so much of the runway so i believe it was a flex thrust takeoff)
but the noice was so high, why didnt they do the V2500 engine quieter?
In GOT it doesnt play any sence because youre out of nowhere in
Amazonas :ok:

[FullWings]

I was told by one of our engineers that the Trent at high power settings creates a sort of 'shroud' of supersonic air around the fan tips that allows much less of the 'buzz' of the front fan to escape to the sides... I have no idea whether this is actually the case but I have noticed (Trent 895) that a full power takeoff is much quieter in the cabin than a 50deg derate, until the first power reduction when the fan noise reappears.

[Robini]

FullWings
So you mean that the Trent 772B (quite alike with the 895 i think) is
much quiter when the takeff thrust is high??
I was in GOT and i didnt hear anything...

[Wingswinger]

Hello Robini, young man.

It's probably to do with atmospheric conditions. What was the temperature? The barometric pressure? Was there a wind or was it calm? Was there a temperature inversion? All of these atmospheric factors have an effect on noise. If it is cold and calm and there is an inversion, a jet engine will be noisier.

[Robini]

Wingswinger
The temperature was about 7 degrees celsius,QNH no idea but i guess
it was pretty normal around 1015 hpa, the wind was 10-15 knots.
It was just an normal relative cold and calm day.

[Tight Slot]

well not too sure about the V2500's, might have a lower by-pass than the trent. What I can say though is that the 330 can take off with 233 tonnes, even with FLEX. Can also take off at under 140 tonnes so lots and lots of take off range in load. the 321 only has a take of range im guessing now of 20 tonnes so needs lots of power all the time. only a guess from a 330 pilot....

[Robini]

Both the A321 and A333 used 2200 m,thats must been a flex for the A321 or?
Tight Slot: wich airline are you working for and wich version of A330??

[Wingswinger]

Maybe the 321 was doing a TOGA take-off at maximum weight?

[Tight Slot]

you can never tell if its FLEX or not unless you know for sure the engine sounds. The 330 has a big big wing so can take off from small fields very well. What i tried to say was the 330 has lots of "free power" to get off at low weights or hot temps. the 319 - 321 needs lots of power (reltve) to get airbourne. Thats why a 330 can get in the air with not much noise. Think about an empty 744, taking off at 220 tonnes, not much thrust needed?

[Robini]

So you mean that the A321 have a longer Takeoff Distance than the A330??
The takeoff weight for the A333 this time was about 221 t.

[Tight Slot]

Did I say that? No. Your post was why a 330 made less noise than a 321. I think I have answerd your question. A 330 can FLEX (de rate) a shed load more than a 321.

Both being full.

After all a 330 can carry more than a 321 weighs in fuel. lots, lots more.

[Wingswinger]

yes, it could have if it was close to maximum weight and the 330 was relatively light.

[Tight Slot]

i thank you. (TRI 330)

[Robini]

Yeah, Wingswinger of course it is so, but the A330 wasnt light at all.
405 pax a lot of fuel,cargo...:ok:

Yeah, Tight Slot you have answered my question, i was just wondering
something about this sorry if im strenuous...
So a last question (you dont need to answer this if im so strenuous).
You said that the A330 can do a flex thrust departure at much higher
weights than the A321 and the question is cannot the A321 use the
flex method at higher weights??
And the A321 has better power to weight ratio than the A330 so i been
much sceptical...

Thanks

//Robini

[Tight Slot]

You are being very hard here!!! you are young and so I will give a pilots answer and not be rude. Far too many peolple on here will shoot you down, trust me. the 321 has a take off weight quite small ( as to the the 330...) so it needs to give lots of thrust, lots of the time time. The 330 on the other hand has over 120 tonnes between min and max take off weight. Thats why the A330 can take off nice and quiet - ill be rude here for once - cause it has a **** load of power!!! Empty it needs a breath of air to get in the the air - full it still goes off like a home sick angel... even to FL370, big wing - small runway.

[Robini]

Now im pretty OT but i really must ask you wile im talking to you :ok:
At VXO the A330 USED ONLY 1400 m is that possible??
It sounds crazy...

//Thanks for all help

[Mark 1]

The Trent and V2500 are different generations of engines developed in an increasingly tight noise certification and local noise restriction environment.

The Trent is higher bypass, and importantly, a much lower hot nozzle jet velocity at take-off; and jet noise is highly velocity dependent (6th or 8th power law IIRC). That also means that fan noise at take off is more audible on the Trent. Fan "buzz-saw" noise tends to dominate when the fans are just supersonic (70-75% N1?) and less important at higher and lower N1 fan speeds.

I suspect that a lot more technology has gone into the blade design and acoustic treatment of the nacelle in the Trent too, resulting in a lower level and different character to the V2500.

I don't have the certification EPNL numbers to hand, but I expect that the Trent would be much lower.