Mr Spaceman
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Vortex Generators On A MEL List?

Wed Feb 25, 2004 6:01 am

Hi guys.

In the January issue of Flying magazine, there's a neat article about the Air National Guard (ANG) in Ohio. The writer explains his experience when flying in a KC-135R Stratotanker with the 121st Air Refueling Wing of the ANG of Ohio while on a mid-air refueling training mission over the eastern USA.

During the pre-flight inspections, it was noted that their KC-135R had 2 squawks/snags in the maintenance logs. The first squawk was in reference to the ADF, and the second was about vortex generators.

From the article ...............

"One vortex generator was missing from the bottom of the left horizontal stabilizer. It's okay to fly with two gone, and this was deferred to the next major maintenance."

My interpretation of the above sentence is that vortex generators (VG's) are on the KC-135's MEL list, and that the limit of missing VG's that can be deferred is only 2. If more than 2 VG's are noticed missing during a walk-around inspection, the aircraft will be grounded untill they're replaced. Have I understood this correctly?

So, my questions are .................

Do commercial airliners that use vortex generators on their wings, tails, flaps, etc, also have a set limit of VG's that can be missing in the airliner's MEL list? If the answer is yes, can someone give examples?

it would be interesting to learn that the need for such small objects could ground an airliner.



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Chris  Smile
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dc10hound
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 6:08 am

They're in the CDL (Configuration Deviation List):

B737 CDL

55-1 Aft Body Vortex
Generators
(AFM 55-30-1)

Normal Complement :8 Required For Departure:0

* Any number may be missing.

NOTES:
1. There is no performance penalty.
2. During cruise flight, occasional vertical
motions may be felt which appear to be light
turbu lence. These mot ions are
characteristic of this airplane and should not
be construed as associated with Mach
buffet.
"Eagles soar. But weasels never get sucked into jet intakes.."
 
Mr Spaceman
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 6:29 am

Hello Dc10hound.

Thanks for your quick reply.

OK, so vortex generators are found in an airliner's CDL (Configuration Deviation List), not in the MEL.

In the case of the Boeing 737, eight Aft Body VG's are required for departure but, any number can be missing (a little confusing to me). I woner what the CDL says about the VG's on the 737's wing?

It seems to me that vortex generators can't ground an airliner ........ imagine if they could!

A 737-3 with yellow VG's.


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A KC-135R Stratotanker.


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Spacepope
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 7:49 am

I think you misread that. 8 are the normal compliment, 0 are required for departure.

T.J.
The last of the famous international playboys
 
dc10hound
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 7:52 am

Let me restate this, please:

Normal Complement: 8 (Eight)

Required For Departure: 0 (Zero)

Any number may be missing.

But I see you already figured that...

 Big thumbs up

[Edited 2004-02-24 23:54:17]
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Mr Spaceman
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 8:06 am

Hello Spacepope.

Thanks for pointing that out to me. I did misread what Dc10hound typed out.

I better get my act together,  Nuts or Dc10hound is going to stop replying to me!

I suspect that the location and importance of certain vortex generators dictates how many can be missing before the airline needs to replace them.

I wonder, if something like 5 or more vortex generators in a row were missing from the top surface of the wing on the 737 in the photo below, would it still be allowed to depart?


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dc10hound
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 8:21 am

Chris,

Must you ask that question?  Big grin

The short answer is, yes:

B737 CDL

57-1 Wing Vortex Generators

(AFM 57-30-6)
Normal Complement - 16

Required For Departure -14

One on each wing may be missing.

NOTE:
There is no performance penalty.

57-7 Wing Leading Edge Vortilons

(AFM 57-41-12)

Normal Complement - 6

Required For Departure - 4

One on each wing may be missing.

NOTE:
There is no performance penalty.

57-12 Outboard Flap Leading Edge Vortex Generators

(AFM 57-53-7)

Normal Complement - 14

Required For Departure - 8

Up to three non adjacent per side may be
missing provided:

- Operation with flaps 40 is not authorized.
NOTE:
There is no performance penalty.
"Eagles soar. But weasels never get sucked into jet intakes.."
 
vikkyvik
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 8:22 am

Can someone give a quick explanation of what these do exactly? As in, why is it necessary to generate vortices on the upper wing and h stab surface? Thanks...
~Vik
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dc10hound
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 8:26 am

Pop Quiz

The small yellow object just forward of Spoiler # 4 is not a vortex generator or vortilon.

What is it?
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OPNLguy
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 8:52 am

>>>The small yellow object just forward of Spoiler # 4 is not a vortex generator or vortilon. What is it?

While it looks like just another vortex generator, this one has another function. In the event of an evacuation using the over-wing emergency exits, there's a little length of rope/cord stored that one deploys and clips to this yellow fitting. There's also one on the opposite side of the aircraft. IIRC, you'll only see them on 737-100s and 737-200s, since Boeing discontinued them on the 737-300s and later variants.
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
Illini_152
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 9:03 am

Can someone give a quick explanation of what these do exactly? As in, why is it necessary to generate vortices on the upper wing and h stab surface? Thanks...
~Vik



I don't know what they accomplish on airliners, but on light aircraft, they disturb the boundry layer airflow and delay seperation at high angels of attack when installed on the wing. This lets you fly at a higher AoA (and lower airspeed) without stalling.

In twins, I believe it has something to do with increasing rudder authority and reducing Vmc, but as I don't have a "MEL" printed on my certificate yet, I really couldn't say  Big grin.
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Mr Spaceman
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 9:12 am

Hello Dc10hound.

Thank You, for all of that information. It's appreciated! Big grin I enjoy learning about how little things can effect a big airliner's operation.

Regarding your Pop Quiz, I don't know what that yellow object is for, but I suspect it has the same purpose as the yellow object that's found on all A320's wings near the same location.

It appears to be an atachment point where a cable or hook might be used to lift the whole airliner up off a hangar floor .......... pretty far fetched eh?


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> Vikkyvik, vortex generators create a vortex which helps the airflow over a wing stay atached to the wing during high angles of atack & slow airspeeds. It helps prevent a laminar airflow's boundary layer from separating from a wings surface, thus preventing a stalling condition.


Chris  Smile


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OPNLguy
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 9:19 am

>>>Regarding your Pop Quiz, I don't know what that yellow object is for, but I suspect it has the same purpose as the yellow object that's found on all A320's wings near the same location.


Answer is in post #9
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
Mr Spaceman
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 9:35 am

Hello OPNLguy.

Thanks for the correct answer.

Well, your answer sure makes a lot more sense than mine! I wasn't serious about my answer though, I was just saying what it looked like it was for.  Laugh out loud I know that mechanics have large tripod type stands that hook into the lower sides of an airliner's fuselage for the purpose of lifting it off the ground.

You mentioned .............

you'll only see them on 737-100s and 737-200s, since Boeing discontinued them on the 737-300s and later variants

Well, not to be nic-picking but, the 737 in the Pop Quiz photo is a -376 model. So I guess Boeing waited ontill the -400 series to stop using those yellow hook-ups.

Chris  Smile
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dc10hound
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 9:37 am

What is it?

While it looks like just another vortex generator, this one has another function. In the event of an evacuation using the over-wing emergency exits, there's a little length of rope/cord stored that one deploys and clips to this yellow fitting.

OPNLguy has it right!

It appears to be an atachment point where a cable or hook might be used to lift the whole airliner up off a hangar floor .......... pretty far fetched eh?

Why, yes, Chris that really is far fetched!!!

 Nuts



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OPNLguy
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 9:44 am

None of our -300s (that I know of) have them, and I just assumed that Boeing stopped installing them, since we (SWA) were a launch customer (along with USAir) on the -300. Guess they still offer them as an option...
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Francoflier
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RE: Vortex Generators On A MEL List?

Wed Feb 25, 2004 1:13 pm

Actually even small turboprops that use vortex generators have an item on the MEL about it.

For instance on the Jetstream 31/32, you may have no more than 2 non-adjacent vortex generators missing per side. T/O is prohibited if this condition is not satisfied.
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Mr Spaceman
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RE: Vortex Generators On A MEL List?

Thu Feb 26, 2004 7:00 am

Hello Francoflier.

Thanks for your info about the Jetstream 31/32.

In these photos of Jetstream Super 31's you can see the vortex generators between the engines and the fuselage (you might need to enlarge the first shot).


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AJ
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RE: Vortex Generators On A MEL List?

Thu Feb 26, 2004 8:42 am

We had exactly this ex-Hong Kong a few weeks back. It was a deferred defect pertaining to two vortex generators missing from the 767....you guess where!
 
Mr Spaceman
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RE: Vortex Generators On A MEL List?

Thu Feb 26, 2004 8:54 am

Hello AJ.

I'll take a guess as to where they were missing from...........

The leading edge of the outboard flaps on one of the wings, specifically the left wing. Big grin

You can clearly see them in this photo.


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liamksa
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RE: Vortex Generators On A MEL List?

Thu Feb 26, 2004 11:56 am

For interest's sake the retrofit VG kit available for Piper Navajo/Chieftains allows a higher MTOW. This is because the one engine inoperative (OEI) rate of climb required in this category is related to the stall speed, which is lower with the addition of VGs -> can carry more weight.

Rob.
 
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RE: Vortex Generators On A MEL List?

Thu Feb 26, 2004 2:21 pm

Close Chris, but no cigar!
 
QantasA332
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RE: Vortex Generators On A MEL List?

Fri Feb 27, 2004 6:36 am

Can someone give a quick explanation of what these do exactly? As in, why is it necessary to generate vortices on the upper wing and h stab surface? Thanks...

In general, they turbulate the airflow over the wing, thus added total KE to the flow and allowing it to travel further along the wing before seperating, much like dimples on a golf ball do. This is obviously useful at close-to-stall speeds/high AoA.

I'm not sure, but I don't think that their typical usage would differ greatly between lights, twins, and airliners, however there might be some differences.

Cheers,
QantasA332

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