avi
Posts: 888
Joined: Sat Sep 15, 2001 1:27 am

A B744 LE Flaps While Braking, Again

Wed Jul 17, 2002 2:23 am

A few weeks ago there was a discussion in here about the B744 Leading Edge (LE) flaps.
It was said that when the thrust reversers are active the inboard Kruger flaps (slats) and the midspan Variable Camber flaps are retracted as seen in the KLM picture.

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Photo © Peter Unmuth - Vienna Aviation Photography
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Photo © Lee Archer


Now here is a picture of a PIA B744 and as you can see the thrust reversers are active and ALL of the LE flaps (including the outboard Variable Camber flaps) are retracted. My questions are:

1) Is that an airline specific item (the outboard LE flaps)?
2) Does it have anything to do with the engines type?
3) Did the KLM picture was photo before the outboard LE flaps were retracted?
4) What does actually happen when the pilot activate the thrust reverser?

Thanks
Long live the B747
 
aamd11
Posts: 863
Joined: Sat Nov 17, 2001 11:54 am

RE: A B744 LE Flaps While Braking, Again

Wed Jul 17, 2002 3:28 am

That is NO PIA 744! Cos afterall PIA dont have any 744s.
It is a 747-300 that they recently bought from Cathay Pacific.

Aside, i think that maybe the classic 747s have retracting LE flaps the whole length of the wing, my guess is Boeing decided it wasnt necessary for all of them to retract (or it was better that they didnt all retract), and so made it so only the inboard and midspans retracted.

A^A MD-11
 
JETPILOT
Posts: 3094
Joined: Tue May 18, 1999 6:40 am

RE: A B744 LE Flaps While Braking, Again

Wed Jul 17, 2002 8:53 am

Your killing me here.....

Inboard Krueger.... FLAPS
Midspan.... SLATS

JET
 
hkgspotter1
Posts: 5750
Joined: Fri Nov 04, 2005 12:43 pm

RE: A B744 LE Flaps While Braking, Again

Wed Jul 17, 2002 9:48 am

Flaps / Slats,

They are just metal things that move about on the wing  Smile/happy/getting dizzy
 
JETPILOT
Posts: 3094
Joined: Tue May 18, 1999 6:40 am

RE: A B744 LE Flaps While Braking, Again

Wed Jul 17, 2002 11:04 am

Not true... but if you want to be ignorant.... enjoy.

JET
 
MartinKoschel
Posts: 14
Joined: Tue Jun 18, 2002 11:00 pm

RE: A B744 LE Flaps While Braking, Again

Wed Jul 17, 2002 4:07 pm

JET: I agree......

Hkgspotter1: hope you're kidding on this. Here at High-Lift Systems Integration at Airbus we take our Job serious. Very serious. Thus, I have some difficulties with that kind of humor, sorry.
DOn't know if you're a technical person, but anyways: I recommend reading the Book "Aircraft Flight Control Actuation System Design" by E.T. Raymond and C.C. Chenoweth. Will give you some more insight. It's a nice overview.

-martin
 
shaun3000
Posts: 439
Joined: Thu Mar 14, 2002 4:10 pm

RE: A B744 LE Flaps While Braking, Again

Wed Jul 17, 2002 5:01 pm

I didn't think the 747s had slats, rather that they had Kreugers down the entire LE. They all fold out from under the LE. Do the outboard ones have a slot, thus making them a slat? I know that Kreugers don't have a slot between the flap and the LE.
 
FredT
Posts: 2166
Joined: Thu Feb 07, 2002 9:51 pm

RE: A B744 LE Flaps While Braking, Again

Wed Jul 17, 2002 6:37 pm

The terminology in this area is messed up. Slats, slots, flaps... you'd get your head chewed off in some places for even daring to mention flaps as being among the LE devices. So I'd tread lightly on this one...

Cheers,
Fred
I thought I was doing good trying to avoid those airport hotels... and look at me now.
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: A B744 LE Flaps While Braking, Again

Thu Jul 18, 2002 5:45 am

A -300 is a 200 with a stretched upper deck.

747 Classic leading edge devices do not retract on reverser selection. They did in the early days when the engines had turbine reversers but when they went so the LED retraction.
 
shaun3000
Posts: 439
Joined: Thu Mar 14, 2002 4:10 pm

RE: A B744 LE Flaps While Braking, Again

Thu Jul 18, 2002 8:07 am

Clarification on my post:

When I say "they all fold out from under the LE" I'm referring to the LE devices on the 747s, not LE devices, in general.

Anyway, what do 747s have? I always thought they were Kreugers and I took an airframe class where the teacher agreed with me, but others said they were something different...
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: A B744 LE Flaps While Braking, Again

Thu Jul 18, 2002 8:27 am

Ind of the inbd engines they are Krugar's

All the rest are Variable Camber Flaps
 
shaun3000
Posts: 439
Joined: Thu Mar 14, 2002 4:10 pm

RE: A B744 LE Flaps While Braking, Again

Thu Jul 18, 2002 2:49 pm

I am not familiar with variable camber flaps. Can you please explain to me what those are and briefly how they work? I have an idea of what they are from the name but I don't know how that would work.... haha

Thanks!  Smile
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: A B744 LE Flaps While Braking, Again

Thu Jul 18, 2002 9:52 pm

A Krugar Flap remains flat at all times

A VC Flap is flat when it is stowed but a camber is induced in it during deployment to provide more efficient low speed lift.

You will also notice a slot is formed between the flap and the wing LE to increase the aero' efficiency.






When the TE & LE flaps are fully deployed on a 747, lift is increased by 80% compared to the clean wing.
 
shaun3000
Posts: 439
Joined: Thu Mar 14, 2002 4:10 pm

RE: A B744 LE Flaps While Braking, Again

Fri Jul 19, 2002 6:20 am

Ok, that's cool. So it actually bends the aluminum (or whatever material it uses) on the surface? Doesn't this lead to increased wear?
 
AJ
Posts: 2295
Joined: Wed Nov 03, 1999 3:54 pm

RE: A B744 LE Flaps While Braking, Again

Fri Jul 19, 2002 3:19 pm

I believe the B747-400 VC flap is composite. I've observed them being extended in the hanger with only pneumatic power to the flaps (TE weren't being run) and they groan as they extend. Fortunately engine noise normally masks this noise!
JETPILOT: My -400 manual describes all the leading edge devices as flaps, inboard, midspan and outboard!
 
Guest

RE: A B744 LE Flaps While Braking, Again

Fri Jul 19, 2002 4:13 pm

Dear VC-10
Our 747 classics "more recent" retract LE during reverser operation, but some older airplanes we have leased, did not... you got me confused there...
Apparently, Mr. Boeing decided to "retract the LE" during reversers to prevent that foreign objects or... ice located itself under the LE devices due to the reverser thrust... that feature was also common with the 707s I flew, and was the explanation I was given back then...
I remember "slats" from my DC-8 flying days, never heard that word in the 747 and we dont care, they are for us "leading edge devices"...
Cheers, dont insult each other...  Wink/being sarcastic
(s) Skipper
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: A B744 LE Flaps While Braking, Again

Fri Jul 19, 2002 6:06 pm

B747skipper,

dont insult each other... - Who did I insult ?
 
avi
Posts: 888
Joined: Sat Sep 15, 2001 1:27 am

RE: A B744 LE Flaps While Braking, Again

Fri Jul 19, 2002 10:47 pm

Thanks to the replies guys.

I didn’t notice that the PIA aircraft is not 400.

VC-10, great illustrations. Can you post illustrations for the TE flaps (not SP) and the gears (all 3 types  Smile ) please?

Thanks again.

Long live the B747

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