• Please take a moment and update your account profile. If you have an updated account profile with basic information on why you are on Air Warriors it will help other people respond to your posts. How do you update your profile you ask?

    Go here:

    Edit Account Details and Profile

If it's not BOEING, I'm not going ... ???

Shpion1

Shpion1

Member
Contributor
Is it just me or do the engines seem to be of a larger diameter? higher bypass maybe for noise/efficiency?
 
Alpha_Echo_606

Alpha_Echo_606

Does not play well with others!™
Contributor
Yes they are huge! We have the Rolls Royce Trent 1000 test bed here that first tested that engine. It's a 747 and the engine hangs about 1 foot from the ground. It did seem to be quieter than the other engines when they were doing initial run ups behind our building.
 
Junkball

Junkball

"I believe in ammunition"
pilot
I think the larger, slower turning fan blades make for a quieter engine. Just think of the fast-rotating compressors of the super-loud (and inefficient) turbojets of the '60's.


 
Fog

Fog

Old RIOs never die: They just can't fast-erect
None
Contributor
I think the larger, slower turning fan blades make for a quieter engine. Just think of the fast-rotating compressors of the super-loud (and inefficient) turbojets of the '60's.

Junkball: JMHO, but I think the deep-throated roar of J-79s was a much more pleasant sound (or less unpleasant) than the ear-piercing scream I detect from F-404s/414s. At 3,000lbs/hr/side, they could suck some gas, though - especially down low.
 
C

Cleonard19

Member
Contributor
While I make no claim whatsoever to having experience in anything related to aviation, it would seem to me from an outsiders perspective, that the 787 is suffering from the same fate as the Osprey in that the press will never let it live down its issues and shortcomings suffered early in the program.

The 787 program has been plagued by ill-fitting parts and other problems.
Click to expand...
 
Junkball

Junkball

"I believe in ammunition"
pilot
Fog said:
Junkball: JMHO, but I think the deep-throated roar of J-79s was a much more pleasant sound (or less unpleasant) than the ear-piercing scream I detect from F-404s/414s. At 3,000lbs/hr/side, they could suck some gas, though - especially down low.
Click to expand...

No doubt, J79s are the sound of FREEDOM!

Shpion1 said:
Is it just me or do the engines seem to be of a larger diameter? higher bypass maybe for noise/efficiency?
Click to expand...
787_dreamliner_taxi_test.jpg


They're huge! When I was younger, I had saw a picture of my uncle standing in the cowling of the right engine of his 777 along with the rest of his crew. I thought it was a photoshopped picture for the longest time.

Flying011_001.JPG


Cleonard19 said:
While I make no claim whatsoever to having experience in anything related to aviation, it would seem to me from an outsiders perspective, that the 787 is suffering from the same fate as the Osprey in that the press will never let it live down its issues and shortcomings suffered early in the program.
Click to expand...

While it has face criticism, its also has enjoyed a lot of support in the media. I would in no way compare the delays w/ the 787 with the Osprey's tortured development. The MV-22 enjoyed extended stints of criticism on 60 Minutes and other print outlets, while the 787 has not had that pleasure. Dan Rather spewed some garbage about it on his new gig at HDNet, but other than that, it has enjoyed some support from domestic MSM, as the counterpoint to the Gaul's A380. Any real criticism has for the most part been limited to trade journals, AvWeek etc.
 
A4sForever

A4sForever

BTDT OLD GUY
pilot
Contributor
Junkball said:
...They're huge! When I was younger, I had saw a picture of my uncle standing in the cowling of the right engine of his 777 along with the rest of his crew....
Click to expand...
We preferred to us STEWs for our photo ops ... :) ... for a variety of reasons.
1970747engine.png
 
Beans

Beans

*1. Loins... GIRD
pilot
Alpha_Echo_606 said:
Yes they are huge! We have the Rolls Royce Trent 1000 test bed here that first tested that engine. It's a 747 and the engine hangs about 1 foot from the ground. It did seem to be quieter than the other engines when they were doing initial run ups behind our building.
Click to expand...

Junkball said:
I think the larger, slower turning fan blades make for a quieter engine. Just think of the fast-rotating compressors of the super-loud (and inefficient) turbojets of the '60's.
Click to expand...

Generally, you guys have the right idea. The propulsive efficiency (not to be confused with the thermodynamic efficiency*, which is another beast driven by the core of the engine) of a gas turbine engine has to do mostly with the ratio of the exhaust velocity to the aircraft's velocity. The closer the ratio gets to 1, the better the propulsive efficiency. Conversely, the intensity of the sound produced by the exhaust scales with something like the 8th power of that ratio**. In turbojets/low-bypass AB turbofans, this is usually a very high ratio, and the bypass ratio is low, something usually less than 1. The Trent 1000 is 11. So yes, the J79s (and even F414s) are noisy, and a Trent 1000 should be a comparative whisper.

:glasses_1

*This is driven almost entirely by the overall bypass ratio... and holy smokes! The Trent 1000 is 52!

**Since I am on leave, I do not have my treasured copy of "Aircraft Engines and Gas Turbines" at my side.
 
Flugelman

Flugelman

Well-Known Member
Contributor
A4sForever said:
Well then .... how 'bout THIS !!! :D

1991stew.jpg


... and yet another good reason to 'Fly Jets' ... as you can't do this w/ a prop. :D
Click to expand...

A4s seems to have a lot of these pictures of FAs in intakes. Bet he did it just to get peeks up the skirts while he was helping 'em into the nacelle...:eek: :D
 
You must log in or register to reply here.
Top