744 flap retraction sequence

[Lump Jockey]

Hello one and all. I would be grateful if someone could tell me, if this isn't one for "Questions" that is, what the 747-400 flap retraction sequence is on the after landing roll-out, or whatever it's called. Especially the Kruegers and what stage they go in at? Is it possible they can go in and out with different trailing edge settings? I'm sure I've seen this. Cheers.
LJ.

[Avago]

If my fading memory serves me correctly:

During flap extension, the outboard LE flaps extend with the first flap selection (ie Flaps 1), followed by inboard LE flaps and all TE flaps when Flaps 5 is selected. With subsequent flap selections (Flaps 10 thru 30), the TE flaps extend further.

During flap retraction, (eg after landing) the reverse happens: all TE flaps and the inboard LE flaps retract first, followed by the outboard LE flaps once the TE flaps have fully retracted. In addition, during the landing roll the inboard LE flaps will retract when reverse thrust is selected, and deploy again when it is cancelled.

[bsevenfour]

From the B744 manual.

Flap 1 : Inboard and midspan LE flaps extend
Flap 5 : Outboard LE flaps extend and TE flaps extend to Flap 5 position
Flap 10,20,25,30: TE flaps extend to the selected position

For your question about the after landing scenario there is automatic retraction of the Inboard and Midspan LE flaps when reverse is selected. These groups will extend again when reverse is cancelled. When the flight crew retract the flaps the sequence described above is reversed.

There is also an exception to the above sequence of extension and retraction and it occurs when you are in alternate mode of operation. In the alternate mode when you start extension all the LE devices extend together and the trailing edge flaps start extending. For retraction in this case the LE devices, all of them, will only retract when all the TE flaps have retracted.

Finally as far your question on Kreugers is concerned, on the 744 only the inboard LE flaps are Kreugers. The midspan and the outboard groups are variable camber type. Therefore to answer your question the Kreugers will be retracted last of all along with the Midspan variable camber LE flaps.

Hope this helps.

[Avago]

My memory must be fading faster than I thought!

:sad:

[Lump Jockey]

Thank you all very very much. Wasn't actually sure you really knew how they worked!:\ :(
LJ.

[SMOC]

The 400 uses a diferent logic to the "Classic" it only uses flap lever position, so after landing when the flap lever is moved towards UP the trailing edge obviously begins to retract but as soon as the flap lever is placed or passes F1 the outboard LE flap begins to retract and as soon as the flap lever is placed in the UP position the midspan and IB Krugers begin to retract, this is why the LE on a 400 looks like it retracts as one unit on the ground after landing but actually the OB section just starts a fraction earlier as the handle passes flap 1. The "Classic" on the other hand has to wait for the TE to sequence the retraction of the LE.
I hope this helps.

This is incorrect see below.

[QAVION]

The 400 uses a diferent logic to the "Classic" it only uses flap lever position, so after landing when the flap lever is moved towards UP the trailing edge obviously begins to retract but as soon as the flap lever is placed or passes F1 the outboard LE flap begins to retract...."

Are you sure, SMOC? According to my 744 Engineering training notes, the Group B LE flaps (outboard) begin to move when the TE flaps (not the flap lever) are less than 4&1/2 units (and the flap lever is moved to 1 unit).

".... and as soon as the flap lever is placed in the UP position the midspan and IB Krugers begin to retract, this is why the LE on a 400 looks like it retracts as one unit on the ground after landing"

According to my notes, the Group A (Inboard and Midspan) don't begin moving until the TE flaps are UP.

This applies to normal retraction.

Unfortunately, I won't be back at work for several weeks to verify this.

Regards.
Q.

[SMOC]

Haven't got the notes in front of me but I'll check.

[Intruder]

QAVION is correct on this one. Just the other day I watched one in maintenance on the stand next to ours. The outboard LE flaps retracted well before the TE flaps got above the F20 position, but the midspan and inboard LE flaps stayed out until the TE flaps were retracted.

[QAVION]

QAVION is correct on this one. .... The outboard LE flaps retracted well before the TE flaps got above the F20 position,...."

??? Sounds like I was only partially right.... I said:

".... the Group B LE flaps (outboard) begin to move when the TE flaps (not the flap lever) are less than 4&1/2 units (and the flap lever is moved to 1 unit)."

Were they being retracted normally in your situation (hydraulics and pneumatics available)? I've seen some strange things happen when circuit breakers have been pulled and the flaps have been extended in ALTernate mode. When you think everything has been reset, with the flap lever in UP and the flaps up, and you switch on hydraulics, the flaps begin to extend. Very alarming.

I may have to check this out for myself when I get back to work.

Cheers.
Q.

[SMOC]

I was wrong.
This pic shows after landing with group A still extended.
http://www.airliners.net/open.file/166345/L/