Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Krueger Flaps  
User currently offlineZuluAviator994 From Australia, joined Mar 2008, 510 posts, RR: 0
Posted (6 years 3 months 1 week 23 hours ago) and read 21412 times:

Sorry, but i don't get the entire idea of Krueger flaps.
I know what they are...sorta.
But what is the real advantage to these and how are they different to normal slats?
Pictures would be appreciated
rgrds


If Speed is life, Altitude is life insurance. No one has ever collided with the sky.
16 replies: All unread, jump to last
 
User currently offlineOly720man From United Kingdom, joined May 2004, 6684 posts, RR: 11
Reply 1, posted (6 years 3 months 1 week 22 hours ago) and read 21407 times:

Pictures here.

http://www.desktopaero.com/appliedaero/airfoils2/highlift.html

http://www.hq.nasa.gov/pao/History/SP-468/ch10-5.htm

The main advantage is that they are simpler and lighter, but not as good aerodynamically. What they do is to change the shape of the leading edge of the wing (giving it a bigger radius) to reduce the adverse pressure gradient and high suction peak.



wheat and dairy can screw up your brain
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2543 posts, RR: 24
Reply 2, posted (6 years 3 months 1 week 21 hours ago) and read 21370 times:

The main difference is no slot, which adds a lot to the effectiveness of a slat, allowing airflow to remain attached at greater angles of attack (slats work mainly by increasing the stall AOA, so more lift can be generated).

Krueger flaps work like a hinged leading edge flap rather than like a slat. An airflow separation bubble is formed behind the Kreuger flap by the angled section which unfolds as the flap extends, so although it looks as though it didn't ought to work the air flowing behind it behaves very much as if there is a complete lower surface there, reattaching further aft. Crude looking but effective. Basically a Krueger flap increases wing camber and, like a slat, increases the AOA at which the wing will stall.

Boeing combined the slat with the Krueger flap and came up with the variable camber flap, as used outboard on the 747 leading edge.


View Large View Medium
Click here for bigger photo!

Photo © Will Lanting
View Large View Medium
Click here for bigger photo!

Photo © Will Lanting




The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineJetMech From Australia, joined Mar 2006, 2684 posts, RR: 53
Reply 3, posted (6 years 3 months 1 week 20 hours ago) and read 21343 times:



Quoting Jetlagged (Reply 2):
An airflow separation bubble is formed behind the Kreuger flap by the angled section which unfolds as the flap extends

Interesting  scratchchin . So the Krueger flap develops a laminar recirculation bubble over its flat surface which in turn "mimics" a generously rounded leading edge radius similar to that of the variable camber leading edge devices?

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineQslinger From India, joined Apr 2006, 258 posts, RR: 0
Reply 4, posted (6 years 3 months 1 week 18 hours ago) and read 21303 times:



Quoting JetMech (Reply 3):
Interesting . So the Krueger flap develops a laminar recirculation bubble over its flat surface which in turn "mimics" a generously rounded leading edge radius similar to that of the variable camber leading edge devices?

Regards, JetMech

Ouch....my head hurts!!



Raj Koona
User currently offline113312 From United States of America, joined Apr 2005, 569 posts, RR: 1
Reply 5, posted (6 years 3 months 1 week 17 hours ago) and read 21290 times:

The more typical Krueger flap is seen inboard of the engines on B737-200/300 as well as on Boeing 707s and the inboard devices on the B727. The ones shown, for the B747, are a bit different as they are flexible and go from flat when stowed to curved when extended.

User currently offlineJetMech From Australia, joined Mar 2006, 2684 posts, RR: 53
Reply 6, posted (6 years 3 months 1 week 16 hours ago) and read 21281 times:



Quoting Qslinger (Reply 4):

Was it my grammar or the content which hurts  Smile ?

Quoting 113312 (Reply 5):

True, but the leading edge lift enhancement devices between the wing root and inboard engines of the 747 are also flat-panel kruegers.

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineSfomb67 From United States of America, joined Dec 2005, 417 posts, RR: 0
Reply 7, posted (6 years 3 months 1 week 16 hours ago) and read 21265 times:

I only remember Boeing refering to the l/e devices, inbd of the pylons as krueger flaps, and the others as variable camber l/e flaps, on 747's.


Not as easy as originally perceived
User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 8, posted (6 years 3 months 1 week 12 hours ago) and read 21216 times:

On the B737s,The Kruger flaps are located Inboard of the Powerplants,with the Slats outboard.
The swinging outward mvmt & extending round nose are typical of this type.

regds
MEL



Think of the brighter side!
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3476 posts, RR: 67
Reply 9, posted (6 years 3 months 1 week 5 hours ago) and read 21110 times:

Quoting Sfomb67 (Reply 7):
I only remember Boeing refering to the l/e devices, inbd of the pylons as krueger flaps, and the others as variable camber l/e flaps, on 747's.
At Boeing, the 747 outboard leading edge devices as refered to as VCK's for Variable Camber Kreugers.

In the deployed position, there is a slot between the Kreuger trailing edge and the wing leading edge.

[Edited 2008-04-18 10:15:00]


Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlineTWAL1011727 From United States of America, joined Mar 2006, 622 posts, RR: 0
Reply 10, posted (6 years 3 months 3 days 3 hours ago) and read 20820 times:

Another big reason Kruegers were on inboard sections of the wings is if by chance you were to stall,
the outboard sections (where the flight controls were located) would still have aileron control authority
Kruegers tended to have a much sharper and cleaner stall than the slats.

KD


User currently offlineSoon7x7 From , joined Dec 1969, posts, RR:
Reply 11, posted (6 years 3 months 3 days 1 hour ago) and read 20793 times:

Just happened to have 747 Vaiable Camber Flap which by the way is composite in skin structure rienforced with aluminum extruded longerons and machined hinging assembly....Who ever designed this should be president!

The other is an example of all aluminum construction leading edge slat , typical to 727, 737, 757, 767 and 777.
This unit slides forward and down on a series of curved steel rails while the former(747) type is stowed under the leading edge of the wing and drops down and forward, while assuming it's cambered shape. The photo of it laying flat actually is in reverse position. If it were attached to the wing it would be inverted with all the (crap ) up inside the wing.
Big version: Width: 3912 Height: 2610 File size: 1463kb
Big version: Width: 3884 Height: 2591 File size: 1170kb
inverted, but stowed configuration...
Big version: Width: 3924 Height: 2618 File size: 1370kb
typical SLAT cross section...


User currently offlineJetMech From Australia, joined Mar 2006, 2684 posts, RR: 53
Reply 12, posted (6 years 3 months 2 days 21 hours ago) and read 20754 times:



Quoting Soon7x7 (Reply 11):

Nice! How did you happen to come into possession of that VC Krueger panel and mechanism  Smile ? Besides the cleverness of the linkage, which manages to camber the panel and flip the bull-nose, what used to amaze me about those panels was how stiff they were. Using both arms, my feet and the ground, I could only ever bend them a fraction of the distance they bend in service  weightlifter   faint  !

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineSoon7x7 From , joined Dec 1969, posts, RR:
Reply 13, posted (6 years 3 months 2 days 18 hours ago) and read 20734 times:



Quoting JetMech (Reply 12):

I love to collect Space Junk...yeh, your correct, it takes some sweat to configure that VC flap by hand...Boeing engineers were amazing when you consider no computers were used to figure this stuff out...You'd be amazed where you can find goodies like these...The VC component I purchased in AZ from Lee King. Boneyard2u...The slat I bought from a gent in California...Aviation Warehouse...But places all over the US exist and will sell as collectibles...gerard


User currently offlineZeke From Hong Kong, joined Dec 2006, 8861 posts, RR: 75
Reply 14, posted (6 years 3 months 2 days 14 hours ago) and read 20707 times:



Quoting Jetlagged (Reply 2):
An airflow separation bubble is formed behind the Kreuger flap by the angled section which unfolds as the flap extends, so although it looks as though it didn't ought to work the air flowing behind it behaves very much as if there is a complete lower surface there, reattaching further aft. Crude looking but effective. Basically a Krueger flap increases wing camber and, like a slat, increases the AOA at which the wing will stall.

That is true of the simple Krueger like found on the inboard wing of the Boeing 707, the bull-nose Krueger (727) flow on the upper surface of the Krueger is attached over a wider angle-of-attack range, and normally they have more than one setting, takeoff and landing. The variable camber Krueger flap (747) improved the the airfoil shape of the Krueger dramatically and also improves the aerodynamic performance, however that came at a cost of complexity (complex 4-bar linkage, and lower bending stiffness of the fiberglass panel and only two stiffeners basically doubling the number of two span wise hinges). Variable camber Krueger flap were optimized in two positions for landing, they are not as effective for takeoff, they tried to add another optimum position for takeoff, it was considered too complex.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3476 posts, RR: 67
Reply 15, posted (6 years 3 months 2 days ago) and read 20606 times:



Quoting Zeke (Reply 14):
Variable camber Krueger flap were optimized in two positions for landing, they are not as effective for takeoff, they tried to add another optimum position for takeoff, it was considered too complex.

And that's the reason they appear on the 747 but not the Boeing twins.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3476 posts, RR: 67
Reply 16, posted (6 years 3 months 1 day 6 hours ago) and read 20524 times:



Quoting Zeke (Reply 14):
Variable camber Krueger flap were optimized in two positions for landing

There is only one extended position for the 747 VCK's. It is the same for landing and takeoff.

While the VCK's are sometimes referred to as two position devices, the two positions are extended and retracted.

There maybe some confusion as the Flaps 1 detent does not extend all the 747 leading edge devices.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
Top Of Page
Forum Index

Reply To This Topic Krueger Flaps
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Does The A340-600 Take Off With Full Flaps? posted Thu Mar 13 2008 13:13:11 by Happy-flier
A340 Ailerons Drooping When Flaps Set posted Sat Feb 16 2008 20:15:26 by Happy-flier
787/A350 Flaps For Camber Control posted Tue Jan 1 2008 00:48:32 by Faro
747 Landing Speeds (No Flaps) posted Fri Oct 26 2007 14:59:57 by ZBBYLW
What Kind Of Flaps Are These? posted Wed Sep 26 2007 02:11:34 by UAL747
Select Parking Brake Instead Of Flaps? posted Thu Sep 13 2007 13:28:34 by RussianJet
MD11 Landing, So Much Flaps? posted Mon Sep 3 2007 19:25:32 by Readytotaxi
Airbus Flaps Vs. Boeing Flaps posted Tue Aug 21 2007 21:29:04 by UAL747
Fowler Flaps Vs "Barn-Door Flaps" posted Thu Aug 16 2007 19:14:01 by Blackbird
Ailerons, Flaperons, Flaps - All On The Same Wing posted Sat Jul 7 2007 13:31:28 by TripleDelta
What Kind Of Flaps Are These? posted Wed Sep 26 2007 02:11:34 by UAL747
Select Parking Brake Instead Of Flaps? posted Thu Sep 13 2007 13:28:34 by RussianJet
MD11 Landing, So Much Flaps? posted Mon Sep 3 2007 19:25:32 by Readytotaxi
Airbus Flaps Vs. Boeing Flaps posted Tue Aug 21 2007 21:29:04 by UAL747
Fowler Flaps Vs "Barn-Door Flaps" posted Thu Aug 16 2007 19:14:01 by Blackbird
Airbus Slats/flaps Vs Boeing Slats/flaps posted Mon Jan 10 2011 11:31:59 by flaps30
Full Flaps At Takeoff? posted Fri Oct 22 2010 10:54:46 by ANITIX87
When Outboard Ailerons Act As Flaps... posted Sat Nov 14 2009 20:39:55 by Happy-flier
Why Don't Flaps Fly Off? posted Tue Oct 20 2009 03:19:33 by Faro
Why Do Flaps Extend Slowly? posted Wed Oct 14 2009 19:24:07 by TimePilot
Why Flaps On Airbus Dont Have A Gap Like Others posted Mon Aug 17 2009 00:06:51 by AirIndia
Why Do Flaps Extend Slowly? posted Wed Oct 14 2009 19:24:07 by TimePilot

Sponsor Message:
Printer friendly format