View Full Version : 744 LE Flap Symbology

9th Apr 2009, 04:59
Photos: Boeing 747-406F/ER/SCD Aircraft Pictures | Airliners.net (http://www.airliners.net/photo/KLM%20Cargo/Boeing%20747-406F/ER/SCD/0480577/L/&width=1600&height=1212&sok=&sort=&photo_nr=&prev_id=&next_id)

Can't figure out why there are so many different symbols for LE's in this picture.

The flaps seem to be in Primary Electric Mode, with some LE's
1) in transit
2) at full deploy position
3) in transit, but have timed out? (amber hashed?)
4) not moved at all (?) (Solid amber?)

I expected the LE's to deploy more quickly than the TE's. This doesn't seem to be the case.
My notes suggest there is also an amber unfilled and un-hashed symbol. Is there such a thing?

Thanks for any insight,

Feather #3
9th Apr 2009, 05:45
Have a look at the EICAS and see the MSG FLAPS DRIVE.

Now check your NNC for that MSG and go from there.

G'day ;)

9th Apr 2009, 08:32
Thanks. This makes things slightly clearer, but there are still some oddities ...

"FLAPS DRIVE" (LE) can be caused by:

1) no movement in both Primary Pneumatic and Primary Electric drive
2) (in electric operation) no movement within 5 seconds or flaps taking more than 135 seconds to reach their target setting.
3) uncommanded motion for 3 seconds (in primary electric mode)

Is the solid amber symbol an indication that the outboard group has not moved at all in primary hydraulic and electric?(i.e. stuck in the stow position). My training notes are in B&W, so the symbols are somewhat ambiguous.
I understand that if one group fails, the opposite/symmetrical group will be shut down ... a kind of asymmetry protection (with a slight delay). This explains the "LE MULT DRIVE" message.

Why have the other LE groups not deployed sooner than the TE flaps, which normally take 6 minutes to deploy electrically (Slow deployment should have caused a timeout, triggering the FCU to shut them down also).

There seems to be some information missing here.


Dual ground
9th Apr 2009, 08:45
The engines are shut down, cargo doors are open, ground test are enabled. The aircraft is probably undergoing maintenance. We do all sorts of things to these aeroplanes on the ground you know. :ok:

9th Apr 2009, 10:16
We do all sorts of things to theses aeroplanes on the ground you know.

Indeed I do :} Now if only I can figure out what we did do ;)

9th Apr 2009, 15:31
That is the flap indication expanded display. It comes on when there is a non normal condition like the Flaps Drive message.
The solid green is full extend. The solid amber box is a failure or disagree condition.
The white with diagonal lines is In-Transit normal condition and the amber box with diagonal lines is In-Transit failure condition.
Solid White box outline is Full Up.
I'm a long way from my notes right now but I should be able to get more info on it.
I was also thinking that it could be that way because some of the PDUs are disconnected.

9th Apr 2009, 23:25
It's the solid amber which is causing the most confusion for me at the moment, Jetdoc. According to the operations manual, solid amber is full down and in a disagree position. Since the flap lever is at 30, and the solid amber group is full down, why is there a disagreement?

I would have expected a disagreement if the flap group was full up (in which case, the operations manual says the symbol should be unfilled (just an amber outline).


10th Apr 2009, 00:56
Theory No.2

The fault is actually with the RH O/B flap group. The asymmetry protection has shut down the L/H O/B flap group (Would this cause a solid amber symbol, even though this flap group has reached full down and agrees with the flap lever?).

Though this doesn't really explain the appearance/timing of the other symbols.

10th Apr 2009, 01:01
I'm on the road and have limited info right now but I think it may have something to do with the left and right LEs not agreeing. The left side is extended fully while the right is in transit. There may be enough of a discrepency between the left and right side to trigger an asymetric condition and thus both the full extend and in transit indications turn amber. I suspect this is caused by the aircraft under maintenance. Undoubtedly if you go out to the wings, there is probably some work being done on the PDUs.
Can't help much more than that right now.
Just thinking about it, I have seen similar displays intransit on one side with full extend or retract on the other side with electric operation. That happens on the classics and 400's.

Spanner Turner
10th Apr 2009, 08:12
Theory No.2

(Would this cause a solid amber symbol, even though this flap group has reached full down and agrees with the flap lever?).

Though this doesn't really explain the appearance/timing of the other symbols.

NSEU, you've nearly got the meaning of all the indications between you and Jetdoc. Jetdoc did well without books. I had to get them out to get exact timings. I wrote the answer in the hope that others without you’re maintenance knowledge may be able to fathom.The first is an explanation of the indication/colour meanings and then what I believe MAY have happened in the photo you linked to. No guarantees.

Righto, here is the meaning of ALL the L/E expanded primary indications,

FULLY EXTENDED …..Solid Green = Normal........... Solid Amber = Disagree

IN TRANSIT…….Hashed White = Normal.............. Hashed Amber = Disagree
….(Note here that “Transit” means NOT extended and NOT retracted, it doesn’t necessarily follow that the flaps are indeed moving – just that they’re not at their limits. A bit like landing gear indication. The gear is not up and it’s not down and locked – you have no idea how close it may be to either extremity)

FULLY RETRACTED.White Box Outline = Normal...... Amber Box Outline = Disagree

What is a disagree?
When L/E flaps are in “Primary Electric Mode” a disagree is one of 2 things.
1) Failure to move in the commanded direction within 3 seconds.
2) Failure to reach commanded position within 135 seconds.

When a “Disagree” is detected the FCU shuts down/removes power from that ‘Group’
A group in this case is a symmetrical pair of PDU’s. i.e O/B left and O/B right.

Now to the photo - as this aircraft is obviously in a maintenance situation all sorts of things can happen. I highly doubt that Tech Crew would ever be confronted with anything even remotely similar to this. I can explain how the config in the picture can be achieved although it may be hard to put into words. I’ll give it a go.

- A/C is in maintenance/hangar so no bleed air or hydraulics (safety)
- All L/E and T/E flaps are retracted.
- All L/E and T/E flap circuit breakers are pulled. (safety again)
- There’s a requirement to extend all devices.
- Flap lever is moved to 30
- Due nil pnuematics or hydraulics both L/E and T/E flaps go to PRIM ELEC.after 15seconds.( 135 second counter begins)
- Due all C/B’s pulled(refer above) NO surfaces move but cockpit operator begins locating and bashing them in.
- To explain the outboard group indication, when the 135 seconds have elapsed the L/H motor has driven to the extend limit so shows a SOLID box, the R/H motor however is slower/older and has not quite reached it’s full extend limit. The FCU has counted the 135 seconds elapsed time and senses a “disagree” and removes power from that group (both left and right O/B motors) and turns indications amber.
- For the “middle” group in the photo, due to the differing times the C/B’s were set, the 135 second time limit hasn’t been reached yet (say 133 seconds) and in this time the L/H PDU has made it to full extend (hence solid box and green as no disagree has yet been sensed) The right PDU is not quite at full extend so shows a white hash. (NOTE - if the r/h pdu fails to make it to full extend in the next 2 secs then both left and right will go amber and power removed.
- For the inboard set, once again the 135 second limit has not yet been reached yet neither the left or right have made it to full extend so show white hashed transit indications.

This may not be exactly what happened - in fact it may be far from it. I've not included T/E control and/or leading to trailing edge sequencing etc as it's pretty confusing already. Weird and wonderful things happen in maintenance although I think it's during an extension cycle due to the "white" indications. i.e any white indication says that it's within 135 seconds of command so would generally not be enough time to get in and disconnect torque tubes and/or PDU canon plugs.

The asymmetry protection has shut down the L/H O/B flap group
The 744 doesn’t really have a L/E flap assymetry system as such. All the “real” assymetry systems I’ve come across (including 744 TRAILING edge stop all movement instantly the assymetry is detected. The L/E use a timing system and/or change modes.
For example if you select flaps out with bleed air available on the left wing yet no bleed air on the right wing you’ll get full L/H leading edges with no ‘shutdown’. The right wing will change to “Primary Electric” and then give the devices another 135 seconds to reach their extend position before ultimately removing power (as above).

Sorry for the lengthy tome and NSEU please keep the 744 questions coming. Really good to test the old nuts and bolts upstairs and maint manual research capability. There’s far too much 320 and 737 stuff (apologies to those who work on light twin aircraft that you can’t walk under):}



11th Apr 2009, 17:27
Sorry for the lengthy tome and NSEU please keep the 744 questions coming. Really good to test the old nuts and bolts upstairs and maint manual research capability. There’s far too much 320 and 737 stuff (apologies to those who work on light twin aircraft that you can’t walk under)http://static.pprune.org/images/smilies/badteeth.gif

I spent about 25 years on B747s. I'm a pretty tall guy and always appreciated the fact that for the most part, I never really had to duck to walk under a 747. Unfortunately it's been about 7 years since I last worked on one. I did get to do some instructing on the aircraft but even that doesn't happen anymore.
I did get a copy of a schematic and I appreciate your explanation. Things are slowly starting to click. I still need to get my notes but its interesting to discuss things like this. Much more enjoyable than doing a crossword puzzle to keep the mind sharp!!..........

11th Apr 2009, 19:11
I miss the old 747 classic, spending more time on Heavy MD equipment and have great respect for them all. I have changed L/E PDU's by myself as a kid, learned some great tricks from some old timers like how to service them first on the ground and how to rig them in a blink of an eye (2 vice grips). A little older now myself and am looking forward to getting to know the 777. I had a chance to do some avionics work on the G550 and citationX and as I hear it is a bit closer in technology to the advanced corperate jets.

But for now I am happy moving Mud Ducks

12th Apr 2009, 01:19
Thanks, Spanner Turner : )))

Some excellent thoughts... and safety tips, too.