ATC RET 2003
No More Vectors
Zey are climEEN into Frahnsh airspace, zerefore zey are shopEEN. Eef, 'eaven forBEED, zey were climEEN into Ahn-GLEESH airspace, zey would be dice-EEN.
AA Boeing 777 Takeoff FULL POWER Take Off INTENSE
- Thread starter brent p h
- Start date
Zey are climEEN into Frahnsh airspace, zerefore zey are shopEEN. Eef, 'eaven forBEED, zey were climEEN into Ahn-GLEESH airspace, zey would be dice-EEN.
coa787
Unknown Member
Am I the only one who finds it funny when people try to correct or insult other people's grammar without being aware of their own flavor of hideous grammar? 
Located behind the fan blades, in the bypass duct (where the air that does not enter the compressor travels), are stators called Outlet Guide Vanes (OGVs). Since the fan blades are rotating, they make the airflow swirl in the direction of the rotation as it passes the fan blades (much like how the propeller airflow swirls around the fuselage of a single-engine, piston airplane).
This swirling airflow now has less momentum dedicated to thrusting the airplane forward because the total-momentum vector is split into two smaller vectors at 90° from each other; one vector is pointed to the rear of the engine, and the other vector is pointed to the side of the engine in the direction of fan rotation (think about the loss of vertical lift as the lift vector is split into vertical and horizontal vectors when an airplane begins to turn). OGVs are used to remove the swirl (eliminate the momentum vector that points to the side of the engine); thus, straightening the airflow to regain the momentum that is used for thrust.
These OGVs are a large source of the engine noise that you hear in the video. Each fan blade grabs a chunk of air and pushes it back. These chunks all slap against the OGVs. This is the "chopping noise" that you hear. The interaction between unsteady fan airflow and the OGVs also produces the rumbling sound. The intensity of the sounds will vary with the number and rotation speed of the fan blades.
The Rolls-Royce Trent 900 engine was the first Rolls-Royce turbofan engine to feature a contra-rotating section (the high-pressure compressor and high-pressure turbine). Currently, this engine is used only on the Airbus A380. The Boeing 777, like the one in the video, utilizes the Trent 800 engine.
Located behind the fan blades, in the bypass duct (where the air that does not enter the compressor travels), are stators called Outlet Guide Vanes (OGVs). Since the fan blades are rotating, they make the airflow swirl in the direction of the rotation as it passes the fan blades (much like how the propeller airflow swirls around the fuselage of a single-engine, piston airplane).
This swirling airflow now has less momentum dedicated to thrusting the airplane forward because the total-momentum vector is split into two smaller vectors at 90° from each other; one vector is pointed to the rear of the engine, and the other vector is pointed to the side of the engine in the direction of fan rotation (think about the loss of vertical lift as the lift vector is split into vertical and horizontal vectors when an airplane begins to turn). OGVs are used to remove the swirl (eliminate the momentum vector that points to the side of the engine); thus, straightening the airflow to regain the momentum that is used for thrust.
These OGVs are a large source of the engine noise that you hear in the video. Each fan blade grabs a chunk of air and pushes it back. These chunks all slap against the OGVs. This is the "chopping noise" that you hear. The interaction between unsteady fan airflow and the OGVs also produces the rumbling sound. The intensity of the sounds will vary with the number and rotation speed of the fan blades.
The Rolls-Royce Trent 900 engine was the first Rolls-Royce turbofan engine to feature a contra-rotating section (the high-pressure compressor and high-pressure turbine). Currently, this engine is used only on the Airbus A380. The Boeing 777, like the one in the video, utilizes the Trent 800 engine.
dustoff17
Still trying to reach the Top Shelf
Am I the only one who finds it funny when people try to correct or insult other people's grammar without being aware of their own flavor of hideous grammar?
Do you mean, for example, the use of a run-on sentence?
N519AT
Ahh! This is how I change this!
Am I the only one who finds it funny when people try to correct or insult other people's grammar without being aware of their own flavor of hideous grammar?
Located behind the fan blades, in the bypass duct (where the air that does not enter the compressor travels), are stators called Outlet Guide Vanes (OGVs). Since the fan blades are rotating, they make the airflow swirl in the direction of the rotation as it passes the fan blades (much like how the propeller airflow swirls around the fuselage of a single-engine, piston airplane).
This swirling airflow now has less momentum dedicated to thrusting the airplane forward because the total-momentum vector is split into two smaller vectors at 90° from each other; one vector is pointed to the rear of the engine, and the other vector is pointed to the side of the engine in the direction of fan rotation (think about the loss of vertical lift as the lift vector is split into vertical and horizontal vectors when an airplane begins to turn). OGVs are used to remove the swirl (eliminate the momentum vector that points to the side of the engine); thus, straightening the airflow to regain the momentum that is used for thrust.
These OGVs are a large source of the engine noise that you hear in the video. Each fan blade grabs a chunk of air and pushes it back. These chunks all slap against the OGVs. This is the "chopping noise" that you hear. The interaction between unsteady fan airflow and the OGVs also produces the rumbling sound. The intensity of the sounds will vary with the number and rotation speed of the fan blades.
The Rolls-Royce Trent 900 engine was the first Rolls-Royce turbofan engine to feature a contra-rotating section (the high-pressure compressor and high-pressure turbine). Currently, this engine is used only on the Airbus A380. The Boeing 777, like the one in the video, utilizes the Trent 800 engine.
I thought the noise was just the tips of the fan blades going super sonic. :dunno:
coa787
Unknown Member
Maybe.
That's what creates the "buzz saw" noise from the shock waves.
Now that I think about it, I may have made a mistake in my original explanation. When the blades go supersonic, the majority of the fan noise that is heard is the "buzz saw" noise, which I now realize is the "chopping" noise that I was talking about. When the blades are subsonic, the majority of the noise comes from the interaction between the fan airflow and the downstream guide vanes, but this is more of a "whining" noise, though, as the wakes of air smack into the OGVs and the compressor's Inlet Guide Vanes (IGVs).
I don't have it in my possession, but the book Aircraft Noise, by Michael Smith, will go into more detail about the different sources of engine noise.
I wonder how the person taking the film figured it was full power?
Anyhoo, on the 767, most are "assumed temperature"/reduced power takeoffs, but depending on weather, weight and "other", sometimes we do "full blower" thrust settings.
But at that point, we're either performance restricted or so fat that it's hard to notice any "Woo Hoo"-able difference in the takeoff.
Anyhoo, on the 767, most are "assumed temperature"/reduced power takeoffs, but depending on weather, weight and "other", sometimes we do "full blower" thrust settings.
But at that point, we're either performance restricted or so fat that it's hard to notice any "Woo Hoo"-able difference in the takeoff.
dasleben
That's just, like, your opinion, man
True that. Last max thrust takeoff I did (in the Middle East), we saw alternating red/white centerline lights during rotation on an 11,500' runway. I thought we lost an engine when I called for climb thrust.
Heeeere piggy piggy piggy!
I've seen a few of those.
Lots of thoughts start going through your head like:
"I hope there's no convective activity because now would be a DAMNED INCONVENIENT TIME for windshear"
"Rotate early or wait just a feeeeew more seconds until we're at the actual rotation speed"
"What was the fuel flow again"
and others!
Lots of thoughts start going through your head like:
"I hope there's no convective activity because now would be a DAMNED INCONVENIENT TIME for windshear"
"Rotate early or wait just a feeeeew more seconds until we're at the actual rotation speed"
"What was the fuel flow again"
and others!
Exactly!
I do love it when some check pilots will extrapolate data like "We've never had an engine failure using reduced power!"
And then I tell them that I had an engine failure doing just that and there's that blink-eyed pause before they say "That's what I heard at the last line check airman meeting!"
"Oh, in that case, let me reimburse Southernjets for bringing back a perfectly good aircraft and canceling a flight for no good reason..."
I do love it when some check pilots will extrapolate data like "We've never had an engine failure using reduced power!"
And then I tell them that I had an engine failure doing just that and there's that blink-eyed pause before they say "That's what I heard at the last line check airman meeting!"
"Oh, in that case, let me reimburse Southernjets for bringing back a perfectly good aircraft and canceling a flight for no good reason..."
brent p h
Well-Known Member
-This was a fully loaded transcon flight....LFPG-KDFW.
brent p h
Well-Known Member
Ooops. correction inter-con ....from my understanding most takeoffs such as these (777) are performed at 91-94% N1. The Trent 800's in the video also produce a whopping 70k lbs of thrust! (They also rattle you quite a bit):laff:
dasleben
That's just, like, your opinion, man
Nick
Well-Known Member
I'd imagine it's closer to 90k a side.
And the -300s are 115K per side!
Nick
Well-Known Member
That's a little more than half the range of that airplane!