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747 Wing Slats?  
User currently offlineSteve332 From Ireland, joined Feb 2007, 116 posts, RR: 0
Posted (7 years 6 months 2 days 21 hours ago) and read 9109 times:

http://www.youtube.com/watch?v=ZJa3FTExWuA

In the above video of a 744 landing in Sydney as soon as it hits the ground the 1st two slats retract and the 3rd one at the end of the wing stays out. Is this controlled by the pilot or is it automatic? it seems timed with the extension of the spoilers but I could be wrong.
Also the video cuts after the aircraft exit's the runway and the 1st 2 slats are back out the the last one is now retracted

Anyone know what this does??

Steve.

42 replies: All unread, showing first 25:
 
User currently offlineLH526 From Germany, joined Aug 2000, 2372 posts, RR: 14
Reply 1, posted (7 years 6 months 2 days 21 hours ago) and read 9093 times:
AIRLINERS.NET CREW
FORUM MODERATOR

This is usual automated procedure to reduce stress on the slats during thrust reverse and give clear airflow to the spoilers. This is not linked with spoiler extension though.
(Slats are no longer needed after touchdown anyway)

Mario
LH526



Trittst im Morgenrot daher, seh ich dich im Strahlenmeer ...
User currently offlineSteve332 From Ireland, joined Feb 2007, 116 posts, RR: 0
Reply 2, posted (7 years 6 months 2 days 21 hours ago) and read 9069 times:

Quoting LH526 (Reply 2):
LH526

Cheers, Iv never noticed it before (Iv never been looking for it tho!)

Do other aircraft have this feature yes?


User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 3, posted (7 years 6 months 2 days 19 hours ago) and read 8940 times:

Quoting LH526 (Reply 1):
This is usual automated procedure to reduce stress on the slats during thrust reverse and give clear airflow to the spoilers. This is not linked with spoiler extension though.
(Slats are no longer needed after touchdown anyway)

Partially true. The LE Edge devices retract to prevent damage from debris thrown up during the reverse thrust operation.


User currently offlineLH526 From Germany, joined Aug 2000, 2372 posts, RR: 14
Reply 4, posted (7 years 6 months 2 days 17 hours ago) and read 8803 times:
AIRLINERS.NET CREW
FORUM MODERATOR

Quoting PhilSquares (Reply 3):
The LE Edge devices retract to prevent damage from debris thrown up during the reverse thrust operation

That's what I meant ..  Smile Thanks anyway for making things more clear.



Trittst im Morgenrot daher, seh ich dich im Strahlenmeer ...
User currently offlineJetdoctor From United Kingdom, joined Aug 2001, 257 posts, RR: 0
Reply 5, posted (7 years 6 months 2 days 17 hours ago) and read 8773 times:

Hey all

Even more cool, is when use of the reverse thrust is completed, they extend again. (only to see all of them being retracted for taxi to the gate or wherever it is parking) This is in the case of a late "go-around" procedure, so they are back out again for lift.

Regards,

Jetdoctor



Break ground, and head into the wind. Don't break wind and head into the ground.
User currently offlineRichPhitzwell From , joined Dec 1969, posts, RR:
Reply 6, posted (7 years 6 months 2 days 13 hours ago) and read 8630 times:

Here is a shot of the back of the wing (different flight of course) into JFK. Kinda cool seeing everything that goes on. Sorry for the low quality, my cam is not the worlds best.

Landing

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User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 7, posted (7 years 6 months 2 days 12 hours ago) and read 8570 times:

This comes up quite frequently in the Tech/Ops forum:

Question On 747-400 Slat Retraction (by UPSMD11 Jun 28 2006 in Tech Ops)

747 Automatic Slat Retraction (by Rducky Jun 14 2004 in Tech Ops)

Slat Retraction During Reverse Thrust? 747-400 (by Ajaaron Nov 5 2006 in Tech Ops)

Leading Edge Slat's On 747-400? (by Rducky Apr 14 2004 in Tech Ops)

Quoting PhilSquares (Reply 3):
The LE Edge devices retract to prevent damage from debris thrown up during the reverse thrust operation.

...is correct.


User currently offlineViscount724 From Switzerland, joined Oct 2006, 25442 posts, RR: 22
Reply 8, posted (7 years 6 months 2 days 12 hours ago) and read 8553 times:

Quoting RichPhitzwell (Reply 6):
Here is a shot of the back of the wing (different flight of course) into JFK. Kinda cool seeing everything that goes on.

Not as much as goes on on a B727 wing on approach/landing! Sitting over the wing on a 727 and watching it gradually disassemble itself on approach was one of the highlights of flying on a 727!


User currently offlineRichPhitzwell From , joined Dec 1969, posts, RR:
Reply 9, posted (7 years 6 months 2 days 12 hours ago) and read 8533 times:

Quoting Viscount724 (Reply 8):


Not as much as goes on on a B727 wing on approach/landing! Sitting over the wing on a 727 and watching it gradually disassemble itself on approach was one of the highlights of flying on a 727!

It would be pretty cool if we had vids like the two above clearly showing the leading edge as well as trailing for 727 or others. 727's still fly, maybe someone has a vid (not that I would ever encourage using electronic devices).


User currently offlineViscount724 From Switzerland, joined Oct 2006, 25442 posts, RR: 22
Reply 10, posted (7 years 6 months 2 days 11 hours ago) and read 8507 times:

Quoting RichPhitzwell (Reply 9):
It would be pretty cool if we had vids like the two above clearly showing the leading edge as well as trailing for 727 or others.

There probably is a 727 video of the wing activities somewhere. There are quite a few A.net photos, including the following:


View Large View Medium
Click here for bigger photo!

Photo © Chris Waser
View Large View Medium
Click here for bigger photo!

Photo © Peter Kesternich



View Large View Medium
Click here for bigger photo!

Photo © Bruce Leibowitz
View Large View Medium
Click here for bigger photo!

Photo © Bruce Leibowitz



And a few things were happening at the front of the wing too!


View Large View Medium
Click here for bigger photo!

Photo © Andy Jung
View Large View Medium
Click here for bigger photo!

Photo © Andy Jung



User currently offlineRichPhitzwell From , joined Dec 1969, posts, RR:
Reply 11, posted (7 years 6 months 2 days 9 hours ago) and read 8451 times:

Great photos. Period.

Unfortunately still photos dont really show the complexity and as an amateur, I'm having a difficult time seeing the complexity vs the 744. Perhaps someone could explain how and why.


User currently offlineLASOctoberB6 From Japan, joined Nov 2006, 2380 posts, RR: 1
Reply 12, posted (7 years 6 months 2 days 8 hours ago) and read 8437 times:

i just dont understand why the slats retract upon reverse thrust activation and when deactivated, the 2 slats come back out and then all 3 retract....makes no sense but okay......


[NOT IN SERVICE] {WEStJet}
User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 13, posted (7 years 6 months 2 days 8 hours ago) and read 8426 times:

Quoting LASOctoberB6 (Reply 12):
i just dont understand why the slats retract upon reverse thrust activation and when deactivated, the 2 slats come back out and then all 3 retract....makes no sense but okay......

It's very simple, the slats retract during reverst thrust to prevent damage to the inboard leading edge devices. Once reverse thrust is cancelled, then the slats return to the selected position. After the aircraft is clear of the runway, the crew does the "after landing check" and the flaps are retracted. Retracting the flaps will cause the LE devices to retract and stow.

Simple!!!


User currently offlineTheJoe From Australia, joined Oct 2006, 61 posts, RR: 4
Reply 14, posted (7 years 6 months 2 days 6 hours ago) and read 8402 times:

Sorry to be picky, but aren't they leading edge flaps? There is a very distinct difference! Classic example, 737 outboard of the engine = leading edge slats. Inboard = Kruger flaps!

Slats allow air to pass up between them and the leading edge of the wing. Kruger flaps generally have an aerodynamic seal that stops air flowing between them and the leading edge of the wing. Slats are generally part of the leading edge of the aircraft at all times and extend when required, kruger flaps fold out from inside the leading edge and are tucked away when not required!

Regards,

TheJoe


User currently offlineAmericanB763ER From Luxembourg, joined Sep 2005, 166 posts, RR: 0
Reply 15, posted (7 years 6 months 2 days 6 hours ago) and read 8401 times:

Quoting PhilSquares (Reply 13):
the slats retract during reverst thrust to prevent damage to the inboard leading edge devices

Not to be a nitpicker here but aren't the 744's leading edge devices called something like 'Kruger flaps' rather than slats? IIRC all 747's have them. (what about the 748 ...?). Technically 747's don't have slats at all correct me if I'm wrong.

Quoting PhilSquares (Reply 13):
It's very simple, the slats retract during reverst thrust to prevent damage to the inboard leading edge devices. Once reverse thrust is cancelled, then the slats return to the selected position. After the aircraft is clear of the runway, the crew does the "after landing check" and the flaps are retracted. Retracting the flaps will cause the LE devices to retract and stow.

Is this a unique feature of the 747 or is it found on other aircraft types as well?

Marco


User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 16, posted (7 years 6 months 2 days 6 hours ago) and read 8402 times:

Quoting TheJoe (Reply 14):
Sorry to be picky, but aren't they leading edge flaps? There is a very distinct difference! Classic example, 737 outboard of the engine = leading edge slats. Inboard = Kruger flaps!



Quoting AmericanB763ER (Reply 15):
Not to be a nitpicker here but aren't the 744's leading edge devices called something like 'Kruger flaps' rather than slats? IIRC all 747's have them. (what about the 748 ...?). Technically 747's don't have slats at all correct me if I'm wrong.

They are technically leading edge flaps. Not Kruger flaps, not slats. The 748 will have leading edge flaps and double slotted trailing edge flaps rather than the triple slotted flaps on the existing 747/744.

Quoting AmericanB763ER (Reply 15):
Is this a unique feature of the 747 or is it found on other aircraft types as well?

It's not on any other Boeings I know of, it's not on any Airbus aircraft, nor is it on the DC-10/MD-11.


User currently offlineBoeingOnFinal From Norway, joined Apr 2006, 476 posts, RR: 0
Reply 17, posted (7 years 6 months 2 days 5 hours ago) and read 8381 times:

What is the definition of a kruger flap? Because in many explainations the term leading edge flap and kruger flap is used for the same thing.

Would also appreciate a good explaination of the difference between slats and leading edge flaps.



norwegianpilot.blogspot.com
User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 18, posted (7 years 6 months 2 days 5 hours ago) and read 8378 times:

Quoting BoeingOnFinal (Reply 17):
What is the definition of a kruger flap? Because in many explainations the term leading edge flap and kruger flap is used for the same thing.

Would also appreciate a good explaination of the difference between slats and leading edge flaps

Here's a good place to start. http://www.desktopaero.com/appliedaero/airfoils2/HighLift.html


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17053 posts, RR: 67
Reply 19, posted (7 years 6 months 2 days 3 hours ago) and read 8350 times:

Quoting BoeingOnFinal (Reply 17):

Would also appreciate a good explaination of the difference between slats and leading edge flaps.



Quoting BoeingOnFinal (Reply 17):
What is the definition of a kruger flap? Because in many explainations the term leading edge flap and kruger flap is used for the same thing.

As I understand it, and I may be wrong:

Slats flit the (normally leading) edge like a glove and extend out. That is, in the retracted state they encase the edge. Slats allow an increase in angle of attack without stalling. They do not lower stall speed per se.

Leading edge flaps extend like the flaps you normally see on the trailing edge, increasing chord and camber. These allow both in increase in AoA and lower stall speed.

Krueger flaps are hinged along the leading edge and fold out forward from their storage position under the wing. Variable camber variants like those on the 747 have an extra hinge in the flap itself, allowing the camber to vary along the flap. These allow both in increase in AoA and lower stall speed.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineZeke From Hong Kong, joined Dec 2006, 9111 posts, RR: 75
Reply 20, posted (7 years 6 months 2 days 2 hours ago) and read 8344 times:

Quoting PhilSquares (Reply 16):

They are technically leading edge flaps. Not Kruger flaps, not slats. The 748 will have leading edge flaps and double slotted trailing edge flaps rather than the triple slotted flaps on the existing 747/744.

Phil,

I know what you have said is what the 744 FCOM says, however I think inboard of the engines they are Krueger (kruger) flaps, the outboard sections have variable camber flaps, I have seen these referred to in NASA papers as bullnose Krueger flaps and variable camber Krueger flaps respectively.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineSteve332 From Ireland, joined Feb 2007, 116 posts, RR: 0
Reply 21, posted (7 years 6 months 2 days 2 hours ago) and read 8341 times:

Quoting LASOctoberB6 (Reply 12):
the 2 slats come back out and then all 3 retract....makes no sense but okay......

At the end of the video I noticed that the 2 that had originally retracted came back out while the 3rd hadn't retracted on landing but did when the other 2 came back out.

Any reason for this??


User currently offlineAmericanB763ER From Luxembourg, joined Sep 2005, 166 posts, RR: 0
Reply 22, posted (7 years 6 months 2 days 1 hour ago) and read 8317 times:

Quoting Steve332 (Reply 21):
At the end of the video I noticed that the 2 that had originally retracted came back out while the 3rd hadn't retracted on landing but did when the other 2 came back out

I've noticed exactly the same thing. The odd part of it is that the 3rd outboard-flaps actuallly retract some time AFTER the engines have stopped T/R' ing and the 2 inboard devices hade come back out.

Strange indeed


User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 23, posted (7 years 6 months 2 days ago) and read 8299 times:

Quoting Zeke (Reply 20):
Phil,

I know what you have said is what the 744 FCOM says, however I think inboard of the engines they are Krueger (kruger) flaps, the outboard sections have variable camber flaps, I have seen these referred to in NASA papers as bullnose Krueger flaps and variable camber Krueger flaps respectively.

No, they aren't Kurger Flaps. The 727 had Krugers on the inboard segment and the 744/747 doesn't. They might look like Kurgers but they are all considered "leading edge flaps"

Quoting AmericanB763ER (Reply 22):
I've noticed exactly the same thing. The odd part of it is that the 3rd outboard-flaps actuallly retract some time AFTER the engines have stopped T/R' ing and the 2 inboard devices hade come back out.

Strange indeed

You might want to get your eyesight checked. They are all retracted when the "after landing check" is performed. If they were deployed when the engines were shut down, they would stay extended. They are pneumatically driven and mechanically locked in place. Please see my post 13.


User currently offlineZeke From Hong Kong, joined Dec 2006, 9111 posts, RR: 75
Reply 24, posted (7 years 6 months 2 days ago) and read 8283 times:

Quoting PhilSquares (Reply 23):
No, they aren't Kurger Flaps. The 727 had Krugers on the inboard segment and the 744/747 doesn't. They might look like Kurgers but they are all considered "leading edge flaps"

I guess we are going to have to agree to disagree, I might add the FAA, NTSB, UK CAA amongst others also call them Krueger flaps.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
25 David L : I can see what AmericanB763ER is saying. In the video above, the inboard LE flaps redeploy when reverse thrust is cancelled, as you described, but sh
26 BoeingFixer : The LE devices extend back to their pre-selected position for sequencing only, not for a late "go-around". Once reverse thrust is selected, you are c
27 Post contains images AmericanB763ER : It says "some time AFTER the engines have stopped T/R' ing" - NOT "some time AFTER the engines have stopped" maybe I used the wrong letters, it was s
28 BoeingFixer : What you're seeing is the normal flap retract sequencing. Upon retracting the flaps from position 5 to 1, the outboard LE group will retract. From fl
29 Post contains images BoeingFixer : As long as electrical power is available, won't the LE devices retract in Secondary mode if pneumatics are lost? Cheers, John
30 Post contains images PhilSquares : Not automatically. You'd have to use ALTN FLAPS system, which is not normally used for "normal" flap extension or retraction. Normal procedures would
31 Post contains images Steve332 : No he's seeing the same thing I saw! (I actually had an eye test last week and passed with flying colours 'Excuse the pun' ) They extend again while
32 PhilSquares : Ok, when reverse thrust is selected, the inboard 2 leading edge segments on both wings retract. When reverse thrust is cancelled, they retract. Once
33 Post contains images BoeingFixer : My reply was to your comment that with the engines shut down, the LE devices would stay extended. I understand the normal procedure is pneumatics for
34 Steve332 : Exactly what I asked in the first place, Cheers for the answer.
35 David L : D'oh! Of course. Rusty brain - I haven't used it for a couple of weeks (I shouldn't have left it outside, though).
36 PhilSquares : We're now getting into the realm of trying to take off on a move able track with the aircraft full of birds flapping their wings. If the aircraft los
37 Post contains images BoeingFixer : No need to resort to insults! Sorry if my reply to your comment wasn't what you would like. Losing hydraulics on the way to the gate wasn't part of m
38 Post contains images JetMech : G'day Phil , I'm gonna respectfully add a point of discussion here; From the looks of these photos, the inboard leading edge lift enhancement devices
39 Jetlagged : Technically the variable camber flaps on the outboard leading edges are a type of Krueger flap. The 747 inboard LE flaps are most definitely Krueger
40 JetMech : Yep, I understand that, but if there is no fluid in systems 1 or 4, the ADP's could spin all day with no effect. What I was getting at is there is no
41 Post contains images Jetlagged : Agreed, but I don't think anyone actually meant that that could happen. Obviously with no hydraulic fluid in the system none of the pumps will work,
42 TristarSteve : Glad to see there is someone else that remembers the droop leading edge on the Trident 1C. I spent many happy nightshifts trying to rig them! Later T
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