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jspitfire
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Vortex Generators On Nose Of 737NGs

Fri Sep 08, 2006 4:25 am

While working for Westjet I've noticed that some of their aircraft have vortex generators just below the windshield. I have seen some 737-700s that have it, and some that don't. I'm wondering what purpose they serve if they are there, and why some of the aircraft don't even have them.

Here's two pictures of 700s, one with, one without:


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Jason
 
2H4
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RE: Vortex Generators On Nose Of 737NGs

Fri Sep 08, 2006 5:13 am



The VGs are part of the eyebrow window removal mod. I'm not sure what specific purpose they serve, but I seem to remember it being related to noise reduction.




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rsbj
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RE: Vortex Generators On Nose Of 737NGs

Fri Sep 08, 2006 6:02 am

I measured a 1.0 db reduction on our 737's with the window replacement mod and VG's versus a -700 without at FL410 and .79M
I fly really fast and take a lot of chances.
 
2H4
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RE: Vortex Generators On Nose Of 737NGs

Fri Sep 08, 2006 6:15 am




Quoting RSBJ (Reply 2):
I measured a 1.0 db reduction on our 737's with the window replacement mod and VG's versus a -700 without at FL410 and .79M

If you had to guess, what percentage of the noise reduction would you say is attributed to the VGs?




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aeroweanie
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RE: Vortex Generators On Nose Of 737NGs

Fri Sep 08, 2006 6:20 am

Quoting RSBJ (Reply 2):
I measured a 1.0 db reduction on our 737's with the window replacement mod and VG's versus a -700 without at FL410 and .79M

That's what the VGs are there for.
 
rsbj
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RE: Vortex Generators On Nose Of 737NGs

Fri Sep 08, 2006 8:46 am

Keeping in mind sound is measured on a logarithmic scale, like Richter, 1.0 db isn't too bad.

I would hazard a guess that the VG's are responsible for most of the reduction. The sheet metal on the eyebrow window replacement mod is relatively very thin compared to the glass it replaces, though glass has lower sound insulating properties. Perhaps the thick glass and thin metal are equal sound insulators.

As most people in Tech/Ops know, the window replacement was more about reducing the small amount of maintenance these small windows require throughout an airframes life.
I fly really fast and take a lot of chances.
 
2H4
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RE: Vortex Generators On Nose Of 737NGs

Fri Sep 08, 2006 10:38 am




Quoting RSBJ (Reply 5):
I would hazard a guess that the VG's are responsible for most of the reduction. The sheet metal on the eyebrow window replacement mod is relatively very thin compared to the glass it replaces, though glass has lower sound insulating properties. Perhaps the thick glass and thin metal are equal sound insulators.

Would the surface irregularities related to the windows (ie: rivets, sealant, frames, etc) not be a greater factor with regard to noise than the sound insulating properties of either material?




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aeroweanie
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RE: Vortex Generators On Nose Of 737NGs

Fri Sep 08, 2006 1:19 pm

Quoting 2H4 (Reply 6):
Would the surface irregularities related to the windows (ie: rivets, sealant, frames, etc) not be a greater factor with regard to noise than the sound insulating properties of either material?

A lot of the noise in the 707/727/737 cockpit comes from the sharp corners between the panes of flat glass on the windshield. The VGs help control the separation on these corners.


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HAWK21M
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RE: Vortex Generators On Nose Of 737NGs

Fri Sep 08, 2006 7:41 pm

Quoting RSBJ (Reply 2):
measured a 1.0 db reduction on our 737's with the window replacement mod and VG's versus a -700 without at FL410 and .79M

How much contributed by the Eyebrow Window removal & how much by the VGs.
What Instrument is used to measure this reduction.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
EssentialPowr
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RE: Vortex Generators On Nose Of 737NGs

Fri Sep 08, 2006 11:21 pm

I would offer that the a/c w/o the eyebrow windows (on a new a/c for ex) stay can maintain much lower cockpit temps sitting at the gate (particulrly w/ the windshield heat off).
 
OPNLguy
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RE: Vortex Generators On Nose Of 737NGs

Sat Sep 09, 2006 1:38 am

Here's a closer view of them...

http://i34.photobucket.com/albums/d143/OPNLguy/Vortex2.jpg

Note the changes in orientation between the one closest to the aircraft centerline and those outboard of it.
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
amtrosie
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RE: Vortex Generators On Nose Of 737NGs

Mon Sep 11, 2006 12:52 am

Any one know of a S/B or STC to eliminate the eyebrows and install the VG's on other models, specifically the 200's?
 
rsbj
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RE: Vortex Generators On Nose Of 737NGs

Mon Sep 11, 2006 9:29 am

I just flew 215WN this evening, and it had the eyebrow and VG mod. I noticed the recessed panels in the cockpit had some thermal insulation and a vinyl cover, adding to the noise canceling properties of this mod. I could be completely off base, but I'm going to say the window mod is worth 1/3 db and the VG's the remaining 2/3 db.

The 1.0 db reduction was measured with a Radio Shack sound meter that is fairly accurate except for low frequencies (< 40hz).

The test was done C-weighted, and I should've done it A-weighted. A-weighted is more atune to how we actually hear. I'll bring my meter with me for my next trip and hopefully fly a newer -700 and be able to do a more comprehensive test if people here would like me to.

Cheers,
Rick
I fly really fast and take a lot of chances.
 
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HAWK21M
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RE: Vortex Generators On Nose Of 737NGs

Mon Sep 11, 2006 8:09 pm

Quoting Rsbj (Reply 12):
The test was done C-weighted, and I should've done it A-weighted

Pls Elaborate on this.
regds
MEL
I may not win often, but I damn well never lose!!! ;)

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