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Old 10th Sep 2017, 17:24   #1 (permalink)
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What happened to those VG's on the 737

No longer on the Max. From Flight International June 13-19...

"The new circular tailcone eliminates a set of four drag inducing vortex generators on the aft fuselage. These were added to correct a design problem discovered in flight test in the late-1960's. 'The airplane had a vertical bounce to it back in the day, and vortex generators were the aerodynamic fix that smooths that airflow, which stopped the bounce but was additional drag.'"
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Old 11th Sep 2017, 01:20   #2 (permalink)
 
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what about the ones on the wings?

those small triangular generators on the intakes were such a drag....what about lack of landing gear doors?

Last edited by underfire; 11th Sep 2017 at 01:41.
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Old 11th Sep 2017, 02:57   #3 (permalink)
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What about them?
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Old 11th Sep 2017, 08:32   #4 (permalink)
 
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JS, et al, I wonder what was the last commercial aircraft which you flew that did not have any VGs?
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Old 11th Sep 2017, 11:24   #5 (permalink)
 
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Underfire, I think if you look you'll see what we call "intake strakes" (also known as 'Engine Ears' ) on most aircraft with big fan engines hanging under the wings. While less than desirable, they are a solution to a very messy problem. With an engine not running during final approach to landing, all that air spilling out of the inlet separates and messes up the airflow over a fair part of the wing (and during an engine out approach, loosing a bunch of lift is rather undesirable), That strake reenergizes that spillage out of the inlet and prevents it from separating the airflow over the wing.

BTW, to the original question, I suspect the aero engineers developed a more elegant fix for the aft fuselage separation problem than the vortex generators...
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Old 11th Sep 2017, 11:40   #6 (permalink)
 
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What about them?
Those vortex tabs on the wings were supposed to be a temporary fix when they first came out. Pilots had a alot of questions about them, especially since they didnt stay on that well at first.

When I speak of the vortex tabs on the wing, I mean the ones on top of the wing

To date, doesnt look like Boeing has been able to design a wing that does not need them.

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Underfire, I think if you look you'll see what we call "intake strakes" (also known as 'Engine Ears' ) on most aircraft with big fan engines hanging under the wings.
That is fine, but not what we are talking about here.

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The new circular tailcone eliminates a set of four drag inducing vortex generators on the aft fuselage.

Last edited by underfire; 11th Sep 2017 at 11:52.
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Old 11th Sep 2017, 20:12   #7 (permalink)
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Originally Posted by safetypee View Post
JS, et al, I wonder what was the last commercial aircraft which you flew that did not have any VGs?
I decided to mention these ones on the 737 because they are particularly large and always wondered why they were there. For interests sake, I decided to make this post in case any other 737 drivers were interested.

To be honest...I don't remember any on the 747.
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Old 11th Sep 2017, 20:32   #8 (permalink)
 
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Some early 737s had a set on the underside of the tail too.

In theory the MAX tail would be retrofitable to most NGs as the basic airframe is identical otherwise.
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Old 12th Sep 2017, 23:23   #9 (permalink)
 
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Hmmm -- I'ld question that motive for adding VG's on the aft fuselage.
Nope, had nothing to due with the APU. When the 737 originally entered service, the cabin crews started getting violently ill due to the vertical bounce in the tail (where the flight crew tends to spend a lot of their time). Apparently the separation of the aft fuselage airflow caused the oscillation at a frequency of a few hertz - which is very, very hard on the human body (the natural frequency of our insides is in that same frequency range - you can imagine what could happen when they match)


However if you look at the tail of a 787 near the APU exhaust, you'll see some strange additions - the result of failing the APU fluid leakage testing multiple times.
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Old 13th Sep 2017, 03:35   #10 (permalink)
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Thanks....very cool to be able to get some info like this.
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Old 13th Sep 2017, 04:15   #11 (permalink)
 
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Originally Posted by tdracer View Post
the cabin crews started getting violently ill due to the vertical bounce in the tail (where the flight crew tends to spend a lot of their time)
I guess if the flight crew were spending a lot of time back there it's no wonder the cabin crew were getting a little vertical bounce in the tail...
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Old 13th Sep 2017, 17:22   #12 (permalink)
 
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Nope, had nothing to due with the APU. When the 737 originally entered service, the cabin crews started getting violently ill due to the vertical bounce in the tail
Yes, of course, that is a well known after the fact fix, that has endured until the Max came out. Speaks volumes on the design of the aircraft!

Now, about the other short term fixes that seem to have become permanent, like the tabs on top of the wing....or the vortex generators on the APU intakes....
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Old 14th Sep 2017, 00:22   #13 (permalink)
 
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IGh
This what I "know".
The vortex generators were there on the 737-200 - I know because I saw them. Back when I first started with Boeing (1977), I worked in Renton and we'd go jogging at lunch time using a locker room/shower in a building on the Renton flightline. We'd jog by the 727s and 737s getting ready for delivery - and I'd noticed those big, ugly VGs on the 737 aft body, so I asked about them. The response I got is reflected my post - a few hertz vibration of the aft fuselage that made the cabin crew sick (the response was a bit more graphic, including if the frequency matched the natural frequency of the individual, they'd loose control of their bowels ). Now, it's possible that answer was total BS, but the source was normally pretty accurate.
The other part is a very good friend of mine was responsible for the APU installation on the 737NG - he got a patent and a cash reward for his idea for the "dual asshole" APU exhaust (look at the tail of a 737NG and you'll know what I'm talking about). He never mentioned anything regarding the VG installation affecting the APU. He retired about 10 years before me, but we've stayed in touch - if I don't forget I'll ask him about it next time I see him.
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