CHRISBA777ER
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777 Spool Up

Fri Mar 03, 2006 7:33 pm

Been spotting at LGW a load of times and noticed the 777s have a really unique spool up sound. Have noticed the A330 does do it but not as much.

The CO and BA triple sevens, being GE90 powered, tend to make a more pronounced whine, quite loud and high pitched, and the Rolls-powered ones do as well but not so loudly. I'm not talking about the actual jet noise, but a howl that seems to start once full power is applied and can be heard over the jet noise.

Listen here: http://www.flightlevel350.com/viewer.php?id=5076

Anyone know what causes it? I'm guessing it is something to do with the fan diameter - ultra high bypass or whatever.

I know that some jets, 757s and DC10s particularly, tend to make a buzzsaw noise but this tends to be in-flight rather than at brakes off. I know this is the fanblade tips going supersonic - i know the 777 does this too - so we can discount this as the cause of the whine.

Its a very unique sound - could listen to it all day!  Smile
What do you mean you dont have any bourbon? Do you know how far it is to Houston? What kind of airline is this???
 
RichardPrice
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RE: 777 Spool Up

Fri Mar 03, 2006 7:48 pm

Quoting CHRISBA777ER (Thread starter):
The CO and BA triple sevens, being GE90 powered, tend to make a more pronounced whine, quite loud and high pitched, and the Rolls-powered ones do as well but not so loudly. I'm not talking about the actual jet noise, but a howl that seems to start once full power is applied and can be heard over the jet noise.

I spotted this on a number of FL350 videos and asked about it in Tech/Ops but to no avail. It definately seems that theres a two stage spool up somewhere in the engine because the second whine is a lot faster and very late into the spool up, imho  Smile
 
CHRISBA777ER
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RE: 777 Spool Up

Fri Mar 03, 2006 8:12 pm

Quoting RichardPrice (Reply 1):
Quoting CHRISBA777ER (Thread starter):
The CO and BA triple sevens, being GE90 powered, tend to make a more pronounced whine, quite loud and high pitched, and the Rolls-powered ones do as well but not so loudly. I'm not talking about the actual jet noise, but a howl that seems to start once full power is applied and can be heard over the jet noise.

I spotted this on a number of FL350 videos and asked about it in Tech/Ops but to no avail. It definately seems that theres a two stage spool up somewhere in the engine because the second whine is a lot faster and very late into the spool up, imho

My thoughts exactly - thats exactly what I am on about.

Heard the PW-powered 777s at LHR and they dont make it hardly at all. The Rolls powered ones do it but its more high pitched and gets lost in the jetblast noise quite quickly - you only hear it for a second or two - the Rolls A330s do it too but not as loudly. I wonder if the Rolls A340s do it?

The GE90s do it much louder and more pronounced. Its most noticable in the Peter Max @ MAN takeoff vid on there.

Still - its a beautiful sound.
What do you mean you dont have any bourbon? Do you know how far it is to Houston? What kind of airline is this???
 
CHRISBA777ER
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RE: 777 Spool Up

Fri Mar 03, 2006 8:18 pm

IIRC all the 777 powerplants are three stage designs - the roller is a triple shaft design, the GE and the Pratt are single shaft.

What happens in the second stage? Bleed air? Could it be the bleed air vents?
What do you mean you dont have any bourbon? Do you know how far it is to Houston? What kind of airline is this???
 
LY777
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RE: 777 Spool Up

Fri Mar 03, 2006 8:24 pm

I love this sound, too
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CHRISBA777ER
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RE: 777 Spool Up

Fri Mar 03, 2006 8:33 pm

Ok so working on the hypothesis that the larger then fan diameter is, the more pronounced the noise is - presumably the 777-300ER/200LR will make it even louder?

Wonder if there's a video I can check this out?
What do you mean you dont have any bourbon? Do you know how far it is to Houston? What kind of airline is this???
 
Dtw757
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RE: 777 Spool Up

Fri Mar 03, 2006 9:57 pm

Here are two great videos which show these sounds. The first is a Saudi 777 with GE engines and the second is a BA 757 with RR engines. I love these sounds as well particularly the growl of the RR engines. The third video is a JA 744 with Pratt/Whitney engines which doesn't make either of these sounds.

http://www.flightlevel350.com/viewer.php?id=1388

http://www.flightlevel350.com/viewer.php?id=2386

http://www.flightlevel350.com/viewer.php?id=4033

I have always the noise to be there on takeoff and disappear as power is pulled back for cruise flight.
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CHRISBA777ER
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RE: 777 Spool Up

Fri Mar 03, 2006 10:20 pm

Wow that SV triple seven got off in about 4,000 ft of runway - Really fast rotation - she must have been nearly empty! Thats the noise though - definately. Cool vid BTW - cheers.
What do you mean you dont have any bourbon? Do you know how far it is to Houston? What kind of airline is this???
 
CHRISBA777ER
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RE: 777 Spool Up

Fri Mar 03, 2006 10:40 pm

Wow that JAL 744 got off just as fast and that was going twice as far!
What do you mean you dont have any bourbon? Do you know how far it is to Houston? What kind of airline is this???
 
TinkerBelle
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RE: 777 Spool Up

Fri Mar 03, 2006 10:43 pm

Quoting CHRISBA777ER (Reply 8):
Wow that JAL 744 got off just as fast and that was going twice as far!

I was just thinking about that.

Quoting CHRISBA777ER (Thread starter):
Listen here:

Is that the new 772LR that was @ MAN last Saturday?
If you are going through hell, keep going.
 
CHRISBA777ER
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RE: 777 Spool Up

Fri Mar 03, 2006 11:00 pm

Quoting TinkerBelle (Reply 9):
Quoting CHRISBA777ER (Thread starter):
Listen here:

Is that the new 772LR that was @ MAN last Saturday

No mate - thats the normal 92b-powered 200ER.
What do you mean you dont have any bourbon? Do you know how far it is to Houston? What kind of airline is this???
 
manzoori
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RE: 777 Spool Up

Fri Mar 03, 2006 11:36 pm

Quoting CHRISBA777ER (Reply 3):
IIRC all the 777 powerplants are three stage designs - the roller is a triple shaft design, the GE and the Pratt are single shaft.

What exactly do you mean by stage Chris?

The Rolls-Royce large civil engines are as you say three shaft, and therefore have a low pressure compressor and turbine (the LP compressor being the fan), an intermediate pressure compressor and turbine and a high pressure compressor and turbine.

P&W and GE are both make two shaft engines and have High and low pressure compressors and turbines.

Cheers!

Rez
 Big grin
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CHRISBA777ER
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RE: 777 Spool Up

Fri Mar 03, 2006 11:40 pm

Quoting Manzoori (Reply 11):
Quoting CHRISBA777ER (Reply 3):
IIRC all the 777 powerplants are three stage designs - the roller is a triple shaft design, the GE and the Pratt are single shaft.

What exactly do you mean by stage Chris?

The Rolls-Royce large civil engines are as you say three shaft, and therefore have a low pressure compressor and turbine (the LP compressor being the fan), an intermediate pressure compressor and turbine and a high pressure compressor and turbine.

P&W and GE are both make two shaft engines and have High and low pressure compressors and turbines.

Cheers!

Rez

Thanks for clearing this up fella.

I think stage and shaft are the same thing now you've explained it.
What do you mean you dont have any bourbon? Do you know how far it is to Houston? What kind of airline is this???
 
jetstar
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RE: 777 Spool Up

Fri Mar 03, 2006 11:53 pm

The noise is from the pneumatic air starters on the engines. Years ago on the Mohawk airlines BAC-111’s, (I am dating myself) which were RR Spey powered, you could hear when the starter engages and starts turning from across the airport. The noise started at a low pitch and as the engine spools up the noise would get higher and you could hear it when the starter disengages and winds down. AA’s BAC111’s had a different model Spey engine and the Gulfstream G2’s and G3’3 also with the Spey engine, you could not hear their air starters.


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At the airport that I was working as an A&P for a small FBO on the airport, Mohawk Airlines served the airport with their BAC-111’s. Sometimes the electric starter engage solenoid would fail and prevent the starter from operating. On the solenoid manual override button, when held in it would allow the starter to engage and start the engine. I was usually called out for this after being checked out by their maintenance people on how to manually override the solenoid. The procedure was simply to open the bottom cowling, hold the button in, give the pilot who was sticking his head out of the window the thumbs up signal and he would then start the engine and the starter would disengage normally after startup. After engine start I would then go into the cockpit and sign off the logbook. I also checked out some of our other mechanics on how to start the engine. I would do this at least a few times a month until they finally came up with a fix to the problem. I heard it was moisture getting in the solenoid.

Take my word for it, being near the air starter as the starter engages and hearing the starter close up was awesome, even with my Mickey Mouse hearing protectors on.

On one airplane at every stop they had to have a mechanic manually start the engine until their maintenance people could replace it, they even carried the solenoid on board with them hoping they could find someone on the road who could change it.

The old DC-8’s with the P&W engines also had a loud starter, you could hear them from across the ramp. Also ever hear a large diesel truck start, they also use pneumatic starters.
 
CHRISBA777ER
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RE: 777 Spool Up

Sat Mar 04, 2006 12:08 am

But the engines got started long time prior to the noise - The noise only comes when TOGA/FLEX is applied.

Do you mean they keep the starter running?
What do you mean you dont have any bourbon? Do you know how far it is to Houston? What kind of airline is this???
 
CHRISBA777ER
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RE: 777 Spool Up

Sat Mar 04, 2006 12:09 am

Quoting Jetstar (Reply 13):

Wicked post though - thanks mate. Very informative.
What do you mean you dont have any bourbon? Do you know how far it is to Houston? What kind of airline is this???
 
Tristarsteve
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RE: 777 Spool Up

Sat Mar 04, 2006 12:23 am

Quoting Jetstar (Reply 13):
AA’s BAC111’s had a different model Spey engine and the Gulfstream G2’s and G3’3 also with the Spey engine, you could not hear their air starters.

The Spey engine on the Trident and the Gulfstreams had an ordinary air turbine starter.
On the BAC111 the starter was combined with the CSD. The CSD had an air driven constant speed device, not oil like every other one i've ever seen. This air rotor was driven by APU bleed air to start the engine. It was called a CSDS. I agree the noise when it started was unique. You could hear it from the other side of the airport. Wonder why no other manufacturer ever tried this design. It worked OK. But it was a large bit of kit and very heavy to replace.
 
jetstar
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RE: 777 Spool Up

Sat Mar 04, 2006 1:20 am

Quoting Tristarsteve (Reply 16):
The Spey engine on the Trident and the Gulfstreams had an ordinary air turbine starter.
On the BAC111 the starter was combined with the CSD. The CSD had an air driven constant speed device, not oil like every other one i've ever seen. This air rotor was driven by APU bleed air to start the engine. It was called a CSDS. I agree the noise when it started was unique. You could hear it from the other side of the airport. Wonder why no other manufacturer ever tried this design. It worked OK. But it was a large bit of kit and very heavy to replace.

Thanks Tristarsteve, very interesting.

As I mentioned on AA’s BAC-111’s, you could not hear the starter and I know they had a different model Spey engine, I think it had more thrust so I assume they had the standard air starter like on the Gulfstream 2’s and the Fokker F-28’s. I worked on G-2’s and the Spey engines and I remember they had constant speed drives on the engines, but I can’t remember where the starter was mounted on, the CSD or gearbox.

Airframe manufactures can build up the same engine differently for their needs, so the very popular Spey engine has quite a few engine buildups
 
Dtw757
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RE: 777 Spool Up

Sat Mar 04, 2006 1:24 am

The starter wouldn't be engaged at takeoff power would it?....I'm going to guess that the shape of the fans have something to do with the sound they produce.
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CHRISBA777ER
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RE: 777 Spool Up

Sat Mar 04, 2006 1:27 am

Is it the fans making the noise though - or is it the air being sucked and pushed into the core?
What do you mean you dont have any bourbon? Do you know how far it is to Houston? What kind of airline is this???
 
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AA777223
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RE: 777 Spool Up

Sat Mar 04, 2006 1:39 am

Awesome post! Love listening to the sounds of those massive T7 engines. I am especially fond of the GE90's and RR 892's.
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DTWAGENT
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RE: 777 Spool Up

Sat Mar 04, 2006 1:51 am

I love the sound of the B777 when they start the take off roll.. Those engines had a great sound to them.......
 
Mich
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RE: 777 Spool Up

Sat Mar 04, 2006 2:17 am

Favorite sound second only to the buzzsaw.

Does sound like it simply increased in rps's though from the 500 rpm idle to about 1500 rpm then stepped up to 2500 rpm take off thrust. Core speed is shown at 6600 rpm at 500 rpm fan speed and 10,600 rpm core speed at take off 2500 fan speed rpm. This is for the GE90 version, models will vary.

www.ge.com
 
BigMac
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RE: 777 Spool Up

Sat Mar 04, 2006 2:22 am

Here's another 777 RR Trent spool up, but from inside the cabin. You can clearly hear the whining (which gets my adrenaline pumping): http://www.flightlevel350.com/viewer.php?id=2279
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Dtw757
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RE: 777 Spool Up

Sat Mar 04, 2006 3:09 am

Quoting CHRISBA777ER (Reply 19):
Is it the fans making the noise though - or is it the air being sucked and pushed into the core?

My guess is it is the sound of the intake fan, a different shape fan makes a different sound. I think it's quite similar to larger vehicles that are equipped with fan clutches. We have several medium duty trucks and when that fan clutch engages and the fan is spinning at full rpm, it will make a sound quite similar to the "buzzsaw" sound.

On takeoff the fan on the jet engine is spinning close to maximum rpm, you would get the most noise out of it at that point. At cruise flight power is pulled back and the fan is not spinning nearly as fast as it was on takeoff so the noise pretty much disappears.
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flydreamliner
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RE: 777 Spool Up

Sat Mar 04, 2006 4:08 am

One might attribute the strange sound made by the GE90 to its fairly uniquely shaped intake fans. Even more strange are the intake fan designs for the GEnx, which I'm sure will make an interesting sound as well.
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Tristarsteve
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RE: 777 Spool Up

Sat Mar 04, 2006 4:14 am

Quoting Jetstar (Reply 17):
can’t remember where the starter was mounted on, the CSD or gearbox

On the non BAC111 Speys, the starter was mounted on the gearbox.
The CSD and the generator were monted on opposite sides of the gearbox, with the CSD to generator drive running through the gearbox and out the other side. RR can always be different.
 
positiverate
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RE: 777 Spool Up

Sat Mar 04, 2006 4:19 am

Quoting DTW757 (Reply 6):
I love these sounds as well particularly the growl of the RR engines.

Almost, but not quite, as good as the RR growl on the L-1011's...
 
RichardPrice
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RE: 777 Spool Up

Sat Mar 04, 2006 4:33 am

This video shows a wonderful example of what I think we are talking about  Smile

http://flightlevel350.com/viewer.php?id=4392
 
EWROwznj00
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RE: 777 Spool Up

Sat Mar 04, 2006 5:23 am

Great thread. I've always wondered about the different noises you hear from the engine. The best clip here I think is the AA 777 taking off. The spool up sound is something else.
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jetstar
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RE: 777 Spool Up

Sat Mar 04, 2006 7:01 am

Quoting Tristarsteve (Reply 26):
On the non BAC111 Speys, the starter was mounted on the gearbox.
The CSD and the generator were monted on opposite sides of the gearbox, with the CSD to generator drive running through the gearbox and out the other side. RR can always be different.

Tristarsteve, thanks again for the information,
 
ptharris
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RE: 777 Spool Up

Sat Mar 04, 2006 8:16 am

Quoting CHRISBA777ER (Reply 14):
But the engines got started long time prior to the noise - The noise only comes when TOGA/FLEX is applied.

Do you mean they keep the starter running?

Umm.. no. At least not on the RR or GE engines. Perhaps on the old JT8's, but dunno. I'm surprised an A/P mechanic hasn't picked up on this thread.

My question is for the original poster, are you talking about the same sound that 752's make at full power?

I think, and I'm not a mechanic so I'm purely speculating, that it is from the intake fan at full thrust.

It'd be nice to know what that racquet is from the engines.  Big grin
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KDTWflyer
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RE: 777 Spool Up

Sat Mar 04, 2006 10:25 am

Listen to this A330-300 spool up noise from the inside...
http://flightlevel350.com/viewer.php?id=1689
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Bluewave 707
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RE: 777 Spool Up

Sat Mar 04, 2006 12:29 pm

Visually, the PWs spew some smoke as they spool up right before take-off. It's reminiscent of the old JT3s from back in the day. The UA and KE 772s here @ HNL do that as they begin their take-off roll down Rwy 8R.
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FI642
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RE: 777 Spool Up

Sat Mar 04, 2006 4:17 pm

Nothing sounds like a RB211 powered 757..... except maybe "You've just won two hundred million dollars!"
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fbgdavidson
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RE: 777 Spool Up

Sat Mar 04, 2006 4:45 pm

And if you need a comparison with a 747 I've got one here. This was a BA747 so I presume RR RB-211s...

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AvFan4ever
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RE: 777 Spool Up

Sat Mar 04, 2006 5:26 pm

Different parts of an engine contribute different sounds to the mix. You have transonic fan tip "buzz saw" sounds, turbomachinery whine from the compressor, tone from the combustor, mechanical sounds from the turbines, exhaust flow from the core, and of course, flow from the fan exhaust.

Early jet engines with low (or no) bypass ratios had very little (or no) help from the fan exhaust to dilute and break up the hot, high-velocity core exhaust flow, which causes the ear-splitting thunder common to earlier engines. High-bypass engines insulate the core flow with large amounts of fan exhaust air, mixing and diluting the core exhaust and reducing the loudest elements of jet noise. Chevrons and other mixing devices within noise suppresion systems can help. Compressor whine is the next loudest sound source, followed by fan blade buzz saw noises.

Ultra high bypass engines with large fan diameters such as the GE90 have relatively low fan speeds, and relatively low exhaust sound levels. This lets other turbomachinery and other engine sounds to be more pronounced, reaching the ear and creating a sound that is distinctive to large high bypass engines. Exhaust sounds are the most annoying to communities neighboring airports, buzzsaw sounds are most annoying to passengers in the forward cabin, and exhaust flow sounds impacting the cabin are most annoying to passengers in the rear cabin. Airframe and engine companies try to reduce all of these sounds. As each type of sound becomes more attenuated, other sounds begin to emerge and become noticeable to the ear.

Engine speed, fan size, bypass ratio, and exhaust velocity all contribute to the signature sound of each engine.

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