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united319
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Chrome Engine Nacelles/Slats

Wed Dec 10, 2014 1:22 am

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Mender
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RE: Chrome Engine Nacelles/Slats

Wed Dec 10, 2014 1:41 am

I'd say it's purely for aesthetics.
 
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SEPilot
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RE: Chrome Engine Nacelles/Slats

Wed Dec 10, 2014 2:48 am

I believe it does have significance. Surface characteristics are very important on certain parts, and leading edges of wings and empennage top the list. I would suspect that the front ring of the nacelle would be right up there as well. Paint is not as smooth as polished metal, no matter how well applied. I am sure this is the reason.
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larshjort
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RE: Chrome Engine Nacelles/Slats

Wed Dec 10, 2014 3:13 am

The anti ice systems in the leading edge of the wings and engine nacelles on most aircraft is using bleed air from the engines. To protect the structure from the hot air they are therefore constructed of stainless steel. I suspect impact resistance is an additional benifit.

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united319
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RE: Chrome Engine Nacelles/Slats

Wed Dec 10, 2014 3:22 am

Thanks for the clarification on this. Always wondered about that.
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AA737-823
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RE: Chrome Engine Nacelles/Slats

Wed Dec 10, 2014 4:03 am

You guys haven't answered his question.
Some airlines buff the engine inlet (like Continental's 737 fleet, for example), while others don't buff it, like United's Airbus fleet.

Any hits as to why this is?

Leading edges do indeed get polished, but they usually look pretty ratty by the time they're due for a re-polish!
 
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Scooter01
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RE: Chrome Engine Nacelles/Slats

Wed Dec 10, 2014 7:12 am

Quoting AA737-823 (Reply 5):
Any hits as to why this is?

Me think you guys got it all wrong. It is only to please some of the camera-carrying passengers.
(Or so that we can check if the nosewheel is down before landing)


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Mender
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RE: Chrome Engine Nacelles/Slats

Wed Dec 10, 2014 10:59 am

Quoting Mender (Reply 1):
I'd say it's purely for aesthetics.

As I've said it will be purely for aesthetics.

Any possible benefit of a polished nacelles/slat compared to an unpoilshed nacelles/slat would be so small you would not be able to measure it in the real world. You can measure how much time and material it takes to polish them but to compare one flight with another to measure the benefit you'd have to fliy EXACTLY the same flight profile with EXACTLY the same weather and EXACTLY the same passengers and EXACTLY the same cargo in the hold. Would you be able to measure the differance in a wind tunnel. Almost certainly but it still wouldn't be cost effective to polish them.
 
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RE: Chrome Engine Nacelles/Slats

Wed Dec 10, 2014 12:03 pm

Polishing the engine cowls and LE/Slats is mostly an esthectic value. It has to be done very carefully so as to not damage the surface of the slat or cowl. I believe that Gulfstream had a GV a few years back that required a slat replacement because of a botched polishing job on the slat. One of my previous employers had a special team come into polish the LE/Cowls on the BBJ's that we operated so I guess that there is more to it than meets the eye. Interestingly they used corn starch as a polishing materail as opposed to a more gritty substance.
 
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CALTECH
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RE: Chrome Engine Nacelles/Slats

Wed Dec 10, 2014 12:44 pm

Quoting Mender (Reply 1):
I'd say it's purely for aesthetics.
Quoting SEPilot (Reply 2):
believe it does have significance. Surface characteristics are very important on certain parts, and leading edges of wings and empennage top the list. I would suspect that the front ring of the nacelle would be right up there as well. Paint is not as smooth as polished metal, no matter how well applied. I am sure this is the reason.

As I remember it being said somewhere, the heat from anti-icing would discolor and ruin any paint on these surfaces, plus with the heat and cold, the paint would flake off. At United and at Continental, these inlet cowls came with a brushed aluminum surface, but after a while they would get polished.


Polished, Brushed.


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Quoting larshjort (Reply 3):
The anti ice systems in the leading edge of the wings and engine nacelles on most aircraft is using bleed air from the engines. To protect the structure from the hot air they are therefore constructed of stainless steel. I suspect impact resistance is an additional benifit.

No stainless steel. The leading edges and engine inlets are constructed of aluminum.
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DashTrash
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RE: Chrome Engine Nacelles/Slats

Wed Dec 10, 2014 2:53 pm

Quoting BravoOne (Reply 8):
It has to be done very carefully so as to not damage the surface of the slat or cowl. I believe that Gulfstream had a GV a few years back that required a slat replacement because of a botched polishing job on the slat.

Gulfstreams don't have slats. Must be a leading edge panel that happened to.

Quoting CALTECH (Reply 9):
As I remember it being said somewhere, the heat from anti-icing would discolor and ruin any paint on these surfaces, plus with the heat and cold, the paint would flake off.

Bingo. You won't see paint on heated surfaces. They get good and hot.
 
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CCA
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RE: Chrome Engine Nacelles/Slats

Wed Dec 10, 2014 3:31 pm

Quoting larshjort (Reply 3):
To protect the structure from the hot air they are therefore constructed of stainless steel.

I can assure you no Boeing or Airbus has stainless steel leading edges on wings or engines. Limitations on the use of wing and engine anti ice protect the structure.

It's purely aesthetic, there will be a small gain but it's doubtful it would pay for the man hours to maintain it.
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BravoOne
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RE: Chrome Engine Nacelles/Slats

Wed Dec 10, 2014 3:45 pm

Quoting DashTrash (Reply 10):
Gulfstreams don't have slats. Must be a leading edge panel that happened to.

Yes I stand corrected and I should have known better as having a type in the GV, Duh!
 
DashTrash
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RE: Chrome Engine Nacelles/Slats

Wed Dec 10, 2014 7:10 pm

Quoting BravoOne (Reply 12):

Time to turn that type in.... 
 
m1m2
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RE: Chrome Engine Nacelles/Slats

Thu Dec 18, 2014 9:12 pm

I would be tempted to say that it's purely for aesthetics, but the CRJ 200 IPC seems to say otherwise. It states that polished and non-polished leading edges cannot be mixed on the same wing. (There are three leading edge segments on each wing of the CRJ 200). Polished, or non-polished can be used, but not mixed on the same wing. Not sure why this is, but that's what's stated in the manual.

The CRJ 200 and CRJ 900 leading edges are covered with aluminum skins as well.

Polishing bare aluminum tends to protect it from the elements. Most of the non-polished aluminum is anodized to protect it from the elements.

So, your questions has more than one answer, sometimes it's for aesthetics, sometimes it's what's available, or what is approved.

[Edited 2014-12-18 13:15:01]
 
BravoOne
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RE: Chrome Engine Nacelles/Slats

Fri Dec 19, 2014 12:54 am

Quoting DashTrash (Reply 13):
Quoting DashTrash (Reply 13):
Time to turn that type in.

Yes. that rating and 13 others would get me enough money to by a cup of coffee these days!
 
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Faro
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RE: Chrome Engine Nacelles/Slats

Sun Dec 21, 2014 8:59 am

On the 787 I would say it's more for aerodynamic efficiency because 787 nacelles are designed to maintain laminar flow over approx. one sixth of the nacelle length. Laminar flow implies a clean, even surface so polishing is important.


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RE: Chrome Engine Nacelles/Slats

Mon Dec 22, 2014 5:51 am

Quoting Faro (Reply 16):
On the 787 I would say it's more for aerodynamic efficiency because 787 nacelles are designed to maintain laminar flow over approx. one sixth of the nacelle length. Laminar flow implies a clean, even surface so polishing is important.
http://modernairliners.com/Boeing787_files/Boeing_787_8_Jetstar_engine.jpg


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CALTECH
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RE: Chrome Engine Nacelles/Slats

Tue Dec 23, 2014 11:45 pm

Quoting DocLightning (Reply 17):
Evidently not.

I'll second that. More of a brushed aluminum look. Same with the Leading edge. No polishing yet.

http://www.netairspace.com/photos/EI-LND/Norwegian_Air_Shuttle/Boeing_787-8_Dreamliner/MCO_KMCO_Orlando_International_McCoy/photo_50474/medium.jpg?uq=0001
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eaglepower83
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RE: Chrome Engine Nacelles/Slats

Tue Jan 06, 2015 3:58 pm

Quoting m1m2 (Reply 14):
Polishing bare aluminum tends to protect it from the elements. Most of the non-polished aluminum is anodized to protect it from the elements.

Bingo.......I think it just depends on the leading edge specified by the engine mfg.
At Pratt, most of our nacelle entrances were just anodized aluminum, so they had a matte finish.

But to those that said surface finish is nil......that couldn't be more inaccurate.
Even such a thing as a cowl screw standing too proud or too recessed will affect the airflow.
It's something that was paid attention to. Because it can matter.
 
MD11Engineer
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RE: Chrome Engine Nacelles/Slats

Tue Jan 06, 2015 8:17 pm

The leading edges and intake lips get sand blasted whenever the plane flies, hence the brushed look. Sure, one could polish them, but this would take a lot of expensive work. As for the exhausts, they are mainly made from steel or titanium, but the heat lets them get superficialy oxydised quite fast.

Jan
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RE: Chrome Engine Nacelles/Slats

Thu Jan 08, 2015 5:02 am

Quoting md11engineer (Reply 20):
The leading edges and intake lips get sand blasted whenever the plane flies, hence the brushed look. Sure, one could polish them, but this would take a lot of expensive work.

The brushed look comes from the factory. Some operators have polished leading edges and nacelle inlets. Air Force One is famous for its shiny metallic surfaces.
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MD11Engineer
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RE: Chrome Engine Nacelles/Slats

Thu Jan 08, 2015 6:05 pm

Quoting DocLightning (Reply 21):

The brushed look comes from the factory. Some operators have polished leading edges and nacelle inlets. Air Force One is famous for its shiny metallic surfaces.

Normally they are quite shiny, fresh from the factory, because the panels they are made of are like this. But in use they become dull due to the constant sandblasting by atmospheric dust.
Most airlines don't bother to polish them because of the extra work.

Jan
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CALTECH
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RE: Chrome Engine Nacelles/Slats

Thu Jan 08, 2015 10:07 pm

Quoting md11engineer (Reply 22):
Normally they are quite shiny, fresh from the factory, because the panels they are made of are like this. But in use they become dull due to the constant sandblasting by atmospheric dust.
Most airlines don't bother to polish them because of the extra work.

All of our 737 and 787 inlet lips are not shiny from the factory. They have the brushed aluminum look from the manufacturer.

# 478 as she was delivered. Inlet lip has brushed aluminum, and it even looks like little machine marks on the inlet lip.

http://www.netairspace.com/photos/N28478/United_Airlines/Boeing_737-924ER/MCO_KMCO_Orlando_International_McCoy/photo_29609/medium.jpg?uq=0001

# 413 had brushed aluminum inlet cowls and leading edges,...

http://www.netairspace.com/photos/N37413/Continental_Airlines/Boeing_737-924ER/MCO_KMCO_Orlando_International_McCoy/photo_31483/medium.jpg?uq=0001

Have seen older 737NGs with polished aluminum inlet lips, # 254,

http://www.netairspace.com/photos/N76254/United_Airlines/Boeing_737-824/MCO_KMCO_Orlando_International_McCoy/photo_28709/medium.jpg?uq=0001
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